JP4235702B2 - Positive electrode active material, manufacturing method thereof, and nonaqueous electrolyte secondary battery using the same - Google Patents

Description

【００８１】
ここでＡは硫酸カルシウム２水塩、Ｂは硫酸水素テトラブチルアンモニウムである。
【００８２】
正極活物質Ｃ−１〜Ｃ−７及び比較−１、比較−２は、硫酸リチウム１水素の添加量を調整することにより、硫酸根の濃度を変化させている。正極活物質Ｃ−８〜Ｃ−１０は、炭酸リチウム又は酸化コバルト中の硫酸根含有率を変化させている。正極活物質Ｃ−１１及びＣ−１２は、添加する硫酸塩を変化させている。
【００８３】
硫酸根の定量は、以下の方法により行った。
試料０．５ｇを３０ｍｌビーカーに秤量し、（１＋１）硝酸６ｍｌ及び（１＋１）過酸化水素４ｍｌを加え、ホットプレート上て加熱し、完全に溶解させる。次いで、放冷した後、１００ｍｌメスフラスコに移し、定容する。さらに、１０倍に希釈し、イオンクロマトグラフ（米国 ＤＩＯＮＥＸ社製、２０００ｉ／ｓ型）にて硫酸根を定量した。
【００８４】
（負極材料である複合金属酸化物の合成例，溶融法）
ＳｎＯを６７．４ｇ、Ｂ₂ Ｏ₃ を１７．４ｇ、Ｓｎ₂ Ｐ₂ Ｏ₇ を１０２．８ｇ混合し、自動乳鉢で十分に粉砕、混合した後、アルミナ製るつぼにセットしてアルゴンガス雰囲気下で１０００℃で１０時間焼成を行った。焼成後、１００℃／分の速度で急冷し、黄色透明ガラス状の負極活物質前駆体ＳｎＢ_0.5 Ｐ_0.5 Ｏ₃ を得た（化合物Ａ−１）。活物質のＸ線回折を測定したところ、Ｃｕ−α線の照射下で２θ＝２０−３５°の領域にブロードな回折のバンドを示したが、結晶構造に帰属するシャープな回折線は検出されず、活物質構造がアモルファス（非晶質）であることが判明した。
【００８５】
（電極合剤シートの作製例）
正極合剤として、正極活物質の化合物Ｃ−１を用い、正極活物質に対して、アセチレンブラック６．７重量％、そして結着剤としてポリテトラフルオロエチレンの水分散物３．３重量％とポリアクリル酸ナトリウム１．１重量％からなる混合物に水を加えて混練し、得られたスラリーを厚さ３０μｍのアルミニウムフィルム（正極集電体）の両面に塗布して、正極シートを作製した。塗布シートを乾燥、プレスした結果、乾膜の塗布量は片面当たり２３０ｇ／ｍ² 、塗布膜の厚みは片面当たりおよそ９０μｍであった。〔表１〕記載の正極活物質Ｃ−２〜Ｃ−１２及び比較−１、比較−２を用いて同様に電極合剤シートを作製した。
【００８６】
負極活物質前駆体として化合物Ａ−１を８６重量％、鱗片状黒鉛を３重量％、アセチレンブラックを６重量％、結着剤としてスチレン−ブタジエンゴムの水分散物４重量％およびカルボキシメチルセルロース１重量％からなる混合物に水を加えてホモジナイザーで１００００ｒｐｍで１０分以上混練し負極合剤スラリーを調製した。得られたスラリーを厚さ１８μｍの銅フィルム（負極集電体）の両面に塗布して、負極シートを作製した。塗布シートを乾燥、プレスした結果、乾膜の塗布量は片面当たりおよそ７０ｇ／ｍ² 、塗布膜の厚み片面当たりおよそ３０μｍであった。
【００８７】
次に、負極シートの活物質層の表面に、鱗片状黒鉛と酸化アルミニウムの１：４（重量比）の混合物からなる保護層（平均厚さ５μｍ）を塗設し、表面保護層付きの負極シートを作製した。
【００８８】
（シリンダー型電池の作製例）
厚さ３５μｍの金属Ｌｉ箔を幅５ｍｍ長さ３７ｍｍの断片に裁断し、露点−６０℃の乾燥空気中で、上記の負極活物質前駆体Ａ−１を塗布した負極シートの両面の表面保護層の上に、２ｍｍの規則的間隔（ギャップ）を置いて圧着ローラーを用いて付着させた。負極シートへのＬｉ付着量は重量としておよそ１１０ｍｇであった。このリチウムは、負極活物質前駆体中へ電池内でリチウムを電解挿入し、負極活物質前駆体を活物質に転換するために用いられる。
【００８９】
上記の正極シートを３５ｍｍの幅に裁断し、負極シートを３７ｍｍの幅に裁断して、シートの末端にそれぞれアルミニウム、ニッケルのリード板をスポット溶接した後、露点−４０℃の乾燥空気中で１５０℃で２時間脱水乾燥した。図１の電池断面図に示したように、脱水乾燥済みの正極シート３、セパレーターとして多孔性ポリエチレンフィルム４、脱水乾燥済みの負極シート２、そしてセパレーター４の順でこれらを積層し、巻き込み機で渦巻き状に巻回した。この巻回体をニッケルメッキを施した鉄製の有底円筒型電池缶１（負極端子を兼ねる）に収納した。この電池缶１の中に電解質として１ｍｏｌ／リットルのＬｉＰＦ₆ （エチレンカーボネート、ブチレンカーボネート、ジメチルカーボネートの２：２：６（体積比）混合液）を注入した。
【００９０】
正極端子を有する電池蓋１３をガスケット７を介してかしめて直径１４ｍｍ高さ５０ｍｍの円筒型電池を作製した。なお、正極端子１３は正極シート３と、電池缶１は負極シート２とあらかじめリード端子により接続した。
【００９１】
上記の方法により、〔表１〕の各正極活物質を用いた電池をそれぞれ作製した。
【００９２】
上記のように作製した電池は負極活物質前駆体に塗布シート保護層上のリチウムが電気化学的に挿入されるプロセスが完成されていない電池前駆体である。そこで、負極活物質前駆体にリチウムを挿入させて負極活物質に変換し、電池前駆体を充放電サイクル可能な二次電池とするための操作を、以下のように実施した。
【００９３】
電池前駆体を、室温で１２時間放置後、０．１Ａの一定電流のもとで１時間予備充電を行い、次いで５０℃のもとで１０日間エージングを実施した。このエージングの工程で、負極上に担持したＬｉは溶解し、負極活物質前駆体の中に挿入されたことを確認した。
【００９４】
この電池を活性化のために、２ｍＡ／ｃｍ² で室温下で４．２Ｖまで充電を行った。さらに、充電状態で電池を５５℃に保持し、３日間エージングを実施した。
【００９５】
以上の電池を、充電終止電圧４．２Ｖ（開回路電圧（ＯＣＶ））、放電終止電圧２．８Ｖ（回路電圧）、２ｍＡ／ｃｍ² （０．２Ｃ相当）の電流密度の条件で繰り返し充放電させた。また電池を、１０ｍＡ／ｃｍ² （１．０Ｃ）の電流で充放電サイクルさせたときの、３００サイクル終了後の初期容量に対する維持率を測定し、電池のサイクル寿命を評価した。
【００９６】
上記の電池について、サイクル寿命の評価の結果を〔表２〕に整理した。
【００９７】
【表２】

【００９８】
硫酸根含有率が０．０１〜４．９重量％である正極活物質Ｃ−１〜Ｃ−１２を用いた電池１〜７、９〜１４は、サイクル維持率（寿命）が高く、サイクル特性が優れている。正極活物質（比較−１）は、硫酸根含有率が０．００５重量％であって少なすぎるため、サイクル維持率が低くなった。正極活物質（比較−２）は、硫酸根含有率が６．０重量％であって多すぎるため、サイクル維持率が低くなった。
【００９９】
正極活物質に含有される硫酸根の濃度は、０．０１重量％〜５重量％が好ましく、０．０５重量％〜２重量％がより好ましく、０．１重量％〜１重量％が特に好ましい。
【０１００】
正極活物質Ｃ−１〜Ｃ７に示すように、硫酸塩の添加量を調整してもよいし、正極活物質Ｃ−８〜Ｃ−１０に示すように、正極活物質材料（炭酸リチウム又は酸化コバルト）中の硫酸根含有率を調整してもよい。
【０１０１】
〔実施例２〕
正極合剤として、実施例１の正極活物質番号比較−１を用い、正極活物質に対して、アセチレンブラック６．７重量％、そして結着剤としてポリテトラフルオロエチレンの水分散物３．３重量％とポリアルカリ酸ナトリウム１．１重量％を加え、これに硫酸リチウム１水和物を活物質に対して硫酸根が０．００５重量％となるように加え、この混合物に水を加えて混練し、実施例１と同様に電極シート及び電池１５を作製し、評価した。
【０１０２】
硫酸リチウム１水和物の添加量が異なる以外は同様にして〔表３〕の電池１６〜２２を得て評価した。
【０１０３】
【表３】

【０１０４】
正極活物質に硫酸リチウムを加えて焼成した後に、硫酸根を加えて正極合剤を作製した場合にも、所定量の硫酸根濃度を有する正極のサイクル特性が優れていた。
【０１０５】
〔実施例３〕
負極活物質として平均粒子サイズ約５μｍのグラファイトを９２重量％、導電剤としてアセチレンブラック３重量％の割合で混合し、さらに結着剤としてポリ弗化ビニリデンを４重量％及びカルボキシメチルセルロースを１重量％加え、水を媒体として混練してスラリーを得た。これを厚さ１０μｍの銅フィルムの両面に塗布、乾燥、プレスして負極シートを作製した。この負極シートにＬｉ箔を付着させないで用いる以外は、実施例１で作成した電池と同様に電池を作成し、評価した。結果は実施例１と同様に硫酸根を含む電池のサイクル寿命が優れていた。
【０１０８】
【発明の効果】
Ｌｉ源及びＭ源（ＭはＣｏ又はＮｉ）を含む正極活物質材料に硫酸リチウムを加えて焼成することによって得られるリチウム含有複合酸化物であり、０．０１重量％以上、５重量％以下の硫酸根を含有する正極活物質を二次電池に用いれば、サイクル寿命が優れた二次電池を提供することができる。
【図面の簡単な説明】
【図１】実施例に使用したシリンダー型の電池の断面図を示す。
【符号の説明】
１ 電池缶（負極端子を兼ねる）
２ 負極シート
３ 正極シート
４ セパレーター
５ 下部絶縁板
６ 上部絶縁板
７ ガスケット
８ 正極リード
９ 防爆弁体
１０ 電流遮断スイッチ
１１ ＰＴＣリング
１３ 電池蓋（正極端子を兼ねる）
１５ 溶接プレート
１６ 絶縁カバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode active material having excellent cycle life and a lithium ion non-aqueous electrolyte secondary battery using the same.
[0002]
[Prior art]
Currently, in general-purpose lithium ion secondary batteries, various carbonaceous materials are used for a negative electrode as a material for reversibly intercalating (occluding / releasing) lithium in an ionic state. A so-called rocking chair type lithium ion secondary battery in which these lithium storage / release materials are combined using a lithium-containing metal composite oxide capable of insertion / release has been used. As the positive electrode active material of these batteries, LiCoO₂LiCo_1-xNi_xO₂, LiNiO₂Cobalt such as cobalt, nickel, and lithium are used, and high potential and high capacity are achieved. However, there is still a high demand for improvement in terms of cycle life, and various attempts have been made. These attempts include stabilizing the crystal structure by dissolving different metals and metalloid elements in the active material cobalt or nickel-lithium composite oxide, and the amount of impurity elements such as sodium and potassium. Although there are attempts to adjust, satisfactory cycle life has not yet been achieved.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a positive electrode active material having a long cycle life or a manufacturing method thereof, and secondly, a lithium ion non-aqueous electrolyte secondary using these positive electrode active materials and having excellent cycle characteristics. It is to provide a battery.
[0004]
[Means for Solving the Problems]
  Of the present inventionAccording to one aspect,
  (A) preparing a positive electrode active material containing a Li source and an M source (M is Co or Ni);
  (B) adding and baking lithium sulfate to the positive electrode active material, and
For producing a positive electrode active material for a lithium ion non-aqueous electrolyte secondary battery, wherein a positive electrode active material containing 0.01 wt% or more and 5 wt% or less sulfate radical
Is obtained.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Although the form of this invention is demonstrated below, this invention is not limited to these.
[0006]
(1) Positive electrode active materialIt is obtained by adding lithium sulfate to a positive electrode active material containing a Li source and an M source (M is Co or Ni) and firing it.A lithium-containing composite oxide,0.01 wt% or more and 5 wt% or lessA positive electrode active material for a lithium ion non-aqueous electrolyte secondary battery, comprising a sulfate group.
[0009]
(2) In a secondary battery including a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte containing a lithium salt,The positive electrode is a lithium-containing composite oxide obtained by adding lithium sulfate to a positive electrode active material containing a Li source and an M source (M is Co or Ni) and firing, and is 0.01 wt% or more and 5 wt% Contains less than% sulfate radicalA lithium ion non-aqueous electrolyte secondary battery characterized by the above.
[0013]
(3) (A) a step of preparing a positive electrode active material containing a Li source and an M source (M is Co or Ni); and (b) sulfuric acid in the positive electrode active material.lithiumAdding and baking.A positive electrode active material containing 0.01 wt% or more and 5 wt% or less of sulfate radicals,A method for producing a positive electrode active material for a lithium ion non-aqueous electrolyte secondary battery.
[0014]
(4)Between the steps (a) and (b),(c) Measuring the concentration of sulfate radicals contained in the positive electrode active materialTheIncludeItem 3A method for producing a positive electrode active material for a lithium ion non-aqueous electrolyte secondary battery.
[0015]
  (5) Said process (b) Depending on the measurement result, the positive electrode active materialAdd lithium sulfate toTerms for adjusting the concentration of sulfate radicals and firing4The manufacturing method of the positive electrode active material of description.
[0016]
  (6) (A) a step of firing a positive electrode active material containing a Li source and an M source (M is Co or Ni); and (b) sulfuric acid added to the fired positive electrode active material.lithiumAnd adjusting the positive electrode mixture by addingProducing a positive electrode mixture containing 0.01 wt% or more and 5 wt% or less of sulfate radicals,The manufacturing method of the positive mix for lithium ion non-aqueous electrolyte secondary batteries.
[0017]
Hereinafter, the positive electrode material according to the embodiment of the present invention and the lithium ion non-aqueous electrolyte secondary battery according to the embodiment of the present invention will be described in detail.
[0018]
The positive electrode active material is Li_xM_1-yN_yO_2-zX_a(M is Co or Ni, N is a transition metal element that is not the same as M, or one or more elements selected from Group 2, Group 13, and Group 14 elements of the periodic table, and X is a halogen element. A lithium-containing composite oxide having a composition of 0.2 <x ≦ 1.2, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 1, 0 ≦ a ≦ 2z), and Li_XCoO₂, Li_XNiO₂ In this case, cobalt or nickel and a part of oxygen are substituted with other elements.
[0019]
Specifically, N is preferably one or more elements selected from Mg, B, Al, Sn, Si, Ga, Mn, Co, Ni, Fe, Ti, Nb, Zr, Mo, and W (provided that M is N is an element other than Co when Co, and N is an element other than Ni when M is Ni).
[0020]
X is a halogen element, and a fluorine atom is particularly preferable.
A preferable positive electrode active material is a composite oxide of lithium and cobalt and / or nickel, and a material represented by the following general formula (1) is preferable.
[0021]
General formula (1) Li_xNi_yCo_1-yzM_zO₂
In the above formula, M is at least one selected from B, Al, Sn, Si, Ca, Fe, Mn, Ti, Nb, Zn, Mo, W, and Sr, 0.1 ≦ x ≦ 1.05, 0 ≦ y ≦ 0.9 and 0 ≦ z ≦ 0.2.
[0022]
As a preferred specific positive electrode active material compound, LiCoO₂ , LiNi_0.02Co_0.98O₂ , LiNi_0.05Co_0.95O₂ , LiNi_0.1 Co₀.₉O₂ , LiNi_0.15Co_0.85O₂ , LiNi_0.2 Co₀.₈O₂ , LiNi_0.78Co_0.2 Al₀.₀₂O₂ , LiNiO₂ , LiNi_0.67Co_0.3 Sr₀.₀₃O₂ Can be mentioned.
[0023]
As a particularly preferred positive electrode active material, LiCoO₂ , LiNi_0.2 Co₀.₈O₂ , LiNi_0.78Co_0.2 Al₀.₀₂O₂ , LiNiO₂ , LiNi_0.67Co_0.3 Sr₀.₀₃O₂ Can be mentioned.
[0024]
It is difficult to obtain these compounds with high purity, and as described in [Prior Art], different elements such as Na, K, Mg, Ca, Al, Cu, Fe, and Si are used as impurities as the positive electrode. It will be mixed into the active material. Since these impurities cause a reduction in the discharge capacity and cycle life of the battery, it is preferable to reduce the impurities in principle.
[0025]
In order to synthesize a positive electrode active material containing a sulfate group, a compound containing a large amount of a sulfate group may be used as a reaction raw material, or an inorganic or organic sulfate may be added.
[0026]
As the reaction raw material, lithium carbonate as a lithium source, cobalt oxide or nickel oxide as a raw material for M, various oxides as a raw material for N, or the like having a high sulfate radical content can be selected.
[0027]
  Add and useInorganic sulfateas,Lithium sulfate can be used.
[0028]
The content of sulfate radicals in the positive electrode active material is represented by (weight of sulfate radical determined by analysis) / (weight of positive electrode active material obtained by synthesis), and is preferably 0.01 wt% or more and 5 wt% or less. . Furthermore, 0.05 wt% or more and 2 wt% or less is more preferable, and 0.1 wt% or more and 1 wt% or less is particularly preferable. Various methods can be used for the determination of the sulfate radical. For example, the sulfate radical can be quantified by ion chromatography after completely dissolving the sample with nitric acid / hydrogen peroxide or the like. In addition, sulfate radicals can be quantified by ICP emission analysis or titration. The ICP emission analysis method is a method in which a sample is dissolved with nitric acid and perchloric acid, sulfur is quantified by ICP emission analysis, and converted to a sulfate radical. The titration method involves adding barium chromate and dilute hydrochloric acid solution to the sample, neutralizing with ammonia, filtering, and replacing the sulfate radical with CrO in the filtrate._Four ^2-Is determined by the iodine method, and the sulfate radical is quantified indirectly (for details, see the Chemical Society of Japan, published by Maruzen Co., Ltd., “Experimental Chemistry Course 15 Analytical Chemistry (below)”).
[0029]
If there are too few sulfate radicals, the cycle characteristics of the secondary battery will deteriorate. When there are too many sulfate radicals, the amount of the positive electrode active material effective for the battery reaction is reduced by that amount, so that the battery capacity is reduced. The content of the sulfate radical is preferably within the above predetermined range.
[0030]
The synthesis of the lithium composite oxide containing a sulfate group consists of a lithium compound as a lithium raw material, a cobalt compound or a nickel compound as a raw material for M, and optionally Co, Ni, Mg, B, Al as a raw material for N , Sn, Si, Ga, Mn, Fe, Ti, Nb, Zr, Mo, W-containing compounds represented by other elements N, halogen compounds as necessary, and inorganic or organic sulfuric acids as necessary It is carried out by mixing a salt and performing a heat-firing reaction or a chemical reaction in a solution state typified by a sol-gel method. The raw materials may be mixed by dry mixing or wet mixing.
[0031]
As for the mixing ratio of the lithium raw material and the M and N element raw materials, it is preferable to mix the atomic ratio of lithium / (element M + element N) at a blending ratio of 0.99X or more and 1.10X or less.
[0032]
The example of the adjustment method of the content rate (concentration) of a sulfate radical is shown. First, a positive electrode active material containing lithium source and M and N element sources is prepared. Next, the concentration of sulfate radical in the positive electrode active material is measured by the ion chromatograph or the like. Next, the concentration of sulfate radicals in the positive electrode active material is adjusted according to the measurement result. Usually, the amount of sulfate radicals present as impurities in the positive electrode active material is small. In that case, an inorganic or organic sulfate (sulfate radical) is added so that the sulfate radical has a predetermined concentration. Thereafter, the added positive electrode active material is fired.
[0033]
Regarding the mixing method of the raw material powder, for example, the powder mixing method described in JP-A-62-264560, JP-A-2-40861, JP-A-6-267538, JP-A-6-231767, JP-A-4-237533, The solution mixing method described in JP-A-5-325966 and JP-A-6-203834, the synthesis method by coprecipitation described in JP-A-63-2111565, and the like can be used.
[0034]
The firing conditions include a raw material powder mixture or a slurry-like mixture in which the sulfate radical concentration is adjusted at a temperature of 600 ° C. to 1100 ° C., preferably 700 ° C. to 1000 ° C., for 2 hours to 48 hours, preferably 5 It is preferable to carry out the synthesis by reacting for 15 to 15 hours. The firing atmosphere is performed in the presence of oxygen or at an oxygen partial pressure of 0.2 atm or more as in the method of synthesis under the control of oxygen partial pressure described in JP-A-6-60887. Firing may be performed a plurality of times under the same conditions or different conditions as necessary. The raw material mixture with the sulfate group concentration adjusted may be previously filled in a pellet and molded as in the methods described in JP-A-5-283076 and JP-A-6-310145. Even when calcination is carried out, sulfate radicals hardly evaporate (disappear).
[0035]
After firing, the fired product can be cooled and pulverized to such an extent that it can be lightly crushed to obtain a positive electrode active material. In cooling, a method of quenching the fired product described in JP-A-5-198301 and JP-A-5-205741 may be used.
[0036]
In addition, a method of firing in a molten state using a LiOH hydrate described in JP-A-5-325969, a fluorine doping method described in JP-A-6-243871, and an interior of particles described in JP-A-8-138670 Alternatively, a method of synthesizing active materials having different surface compositions may be used.
[0037]
The preferable average particle diameter of the positive electrode active material is 1 to 30 μm, preferably 3 to 25 μm. This average particle size corresponds to a particle size usually measured by a laser scattering particle size distribution measurement or the like, and corresponds to a normally defined particle size.
[0038]
The specific surface area of the positive electrode active material is 0.1 to 10 m as measured by the BET method.²/ G is preferable, 0.1 to 3 m²/ G is more preferable.
[0039]
Next, a lithium ion nonaqueous electrolyte secondary battery will be described. The battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. The positive electrode is formed by applying a positive electrode mixture composed of a positive electrode active material, a conductive agent, a binder, and the like on a positive electrode current collector. . This battery is characterized in that the positive electrode contains a sulfate group. The sulfate radical may be contained in the positive electrode active material as described above, or may be contained in a positive electrode mixture other than the active material.
[0040]
The concentration of sulfate radicals contained in the positive electrode mixture is preferably 0.008 wt% or more and 7 wt% or less in total of the amounts present in the positive electrode active material and other mixture layers. Further, it is more preferably 0.04 wt% or more and 3 wt% or less, and particularly preferably 0.08 wt% or more and 1.5 wt% or less. The sulfate radical may be included in both the positive electrode active material and the other positive electrode mixture, or may be included only in the positive electrode active material or only in the positive electrode mixture other than the active material. The same sulfate as that used for the synthesis of the positive electrode active material can be used as the sulfate that can be used.
[0041]
Negative electrode materials used for the negative electrode include metal composite oxides and carbonaceous materials. A metal composite oxide having an amorphous structure and / or a crystal structure mainly containing tin oxide, or a carbonaceous material such as graphite may be used alone, or a composite of these composite metal oxide and carbonaceous material. You may use thing. Since these negative electrode materials feature high-capacity lithium storage, the capacity of the rocking chair type secondary battery can be increased efficiently by combining the positive electrode active material having a high capacity in a well-balanced manner. .
[0042]
Examples of the carbon material include non-graphitizable carbon materials and graphite-based carbon materials. Specifically, carbon materials having surface spacing, density, and crystallite size described in JP-A-62-122066, JP-A-2-66856, JP-A-3-245473, etc. A mixture of natural graphite and artificial graphite described in Japanese Patent No. -290844, and vapor-grown carbon materials described in Japanese Patent Laid-Open Nos. 63-24555, 63-13282, 63-58763, and Japanese Patent Laid-Open No. 6-212617 A material obtained by heating and baking non-graphitizable carbon described in JP-A-5-182664 at a temperature exceeding 2400 ° C. and having a peak of X-ray diffraction corresponding to a plurality of 002 planes, No. 307957, JP-A-5-307958, JP-A-7-85862, and JP-A-8-315820, a mesophase carbon material synthesized by pitch firing described in JP-A-6-84516 Graphite with the above coating layer, various granular materials, microspheres, flat bodies, microfibers, whisker-shaped carbon materials, phenolic resins, acrylonitrile resins, furfuryl alcohol resin fired bodies, hydrogen atoms Examples thereof include carbon materials such as polyacene material. In particular, the carbon materials described in JP-A-5-182664, various granular materials, microspheres, flat plate bodies, fibers, whisker-shaped carbon materials, mesophase pitch, phenol resin, acrylonitrile resin fired bodies, Polyacene materials containing hydrogen atoms are preferred.
[0043]
The composite metal oxide includes a crystalline compound and an amorphous compound. Two or more of these compounds may be used in combination. For example, an amorphous compound may be used in combination, or a crystalline compound and an amorphous compound may be used in combination. It is also a more preferable form to use the carbonaceous material and the composite metal oxide in combination. The composite metal oxide is preferably an oxide containing Group 1, Group 2, Group 13, Group 14, Group 15, a transition metal, and a halogen element in the periodic table. When the carbonaceous material and the composite metal oxide are used in combination, the ratio is preferably 10% or more and 70% or less, preferably 20% or more, by weight of the carbonaceous material relative to the total weight of the carbonaceous material and the composite metal oxide. 50% or less is more preferable.
[0044]
Examples of crystalline metal oxides include Ag.₂O, TiO₂, Fe₂O_Three, MgO, V₂O_Five, NiO, CuO, ZnO, Mo₂O_Three, In₂O_Three, SnO, SnO₂, SnSiO_Three, In₂Sn₂O₇These compounds occlude lithium to form a composite oxide containing lithium.
[0045]
The amorphous composite metal oxide is mainly composed of tin oxide, and one or more selected from Group 1, Group 2, Group 13, Group 14, Group 15, transition metal, and halogen elements in the periodic table It is a compound containing. These metal oxides are also called negative electrode active material precursors. More specifically, it is an amorphous composite oxide mainly containing tin, and is obtained by electrochemically inserting lithium ions into a negative electrode active material precursor represented by the following general formula.
[0046]
Sn_xM1_1-xM2_yO_z
Here, M1 is one or more selected from Mn, Fe, Pb, and Ge, and M2 is selected from Al, B, P, Si, Periodic Table Group 1, Group 2, Group 3, and a halogen element. Two or more elements are represented, and 0 <x ≦ 1, 0.1 ≦ y ≦ 3, and 1 ≦ z ≦ 8. To describe a more preferable composition according to the above structural formula, M1 is an element selected from Pb and Ge, and M2 is two or more selected from B, P, Si, groups 1 and 2 of the periodic table. In particular, M2 is preferably an element other than Al.
[0047]
The insertion of lithium ions into the active material precursor is carried out by cathodic polarization of the negative electrode in the presence of lithium ions in the battery and electrochemical insertion of the lithium ions into the structure.
[0048]
The complex oxide as the precursor is characterized by including an amorphous structure in the structure or being amorphous. The complex oxide contains an amorphous structure, specifically, a state that gives a diffraction scattering band having a broad peak with a weak intensity from 20 ° to 40 ° with a 2θ value by an X-ray diffraction method using CuKα rays. And may have a crystalline diffraction line in this broad scattering band. This crystalline diffraction line is a reflection of a slightly ordered structure in the amorphous structure. More preferably, when a crystalline diffraction line is observed at a 2θ value of 40 ° or more and 70 ° or less, the strongest intensity of the crystalline diffraction lines is observed at a 2θ value of 20 ° or more and 40 ° or less. The intensity of the diffraction line at the apex of the broad scattering band is preferably 500 times or less, more preferably 100 times or less, particularly preferably 5 times or less, and most preferably no crystalline diffraction line. .
[0049]
The negative electrode active material precursor is prepared by mixing a tin compound which is a tin raw material and a powder of a compound containing an element other than tin, and melting the mixture at a high temperature of 800 ° C. to 1500 ° C., preferably 900 ° C. to 1200 ° C. for 4 hours to Synthesize by reacting for 48 hours. The synthesis atmosphere is preferably an inert gas atmosphere such as nitrogen or argon. Especially the oxygen partial pressure is 10^-1Or less, preferably 10^-2The reaction is preferably carried out under the following conditions.
[0050]
The reaction may be quenched at a rate of 50 ° C. to 500 ° C./min to promote amorphization. Conversely, slow cooling can be performed for the purpose of increasing the density of the amorphous structure and increasing the strength.
[0051]
The glassy negative electrode material obtained by these methods is pulverized to obtain a particle size distribution and used as negative electrode particles. A preferable range of the negative electrode particles is 0.5 to 20 μm as an average particle diameter, and more preferably 1 to 10 μm.
[0052]
In addition to the melting method, a synthesis method using a solution reaction, for example, synthesis by a sol-gel method can be used. The range of the preferable average particle diameter of the particles synthesized by the sol-gel method is 0.1 to 10 μm, more preferably 0.2 to 5 μm, as the particle diameter of the secondary particles.
[0053]
Below, the preferable example of the negative electrode active material precursor used by this invention is shown.
SnSi_0.8P_0.2O_3.1
SnSi_0.5B_0.2P_0.2O₁.₈₅
SnSi_0.8B_0.2O₂.₉
SnSi_0.8Al_0.2O₂.₉
SnSi_0.6Al_0.1B_0.2O₁.₆₅
SnSi_0.3Al_0.1P_0.6O₂._{twenty five}
SnSi_0.4B_0.2P_0.4O₂.₁
SnSi_0.6Al_0.1B_0.5O₂.₁
SnB_0.5P_0.5O_Three
SnK_0.2PO_Three.₆
[0054]
SnRb_0.2P_0.8O_Three.₂
SnBa_0.1P₁.₄₅O_Four._Five
SnLa_0.1P_0.9O_Three._Four
SnNa_0.1B_0.45O₁.₇₅
SnLi_0.2B_0.5P_0.5O_Three.₁
SnCs_0.1B_0.4P_0.4O₂.₆₅
SnBa_0.1B_0.4P_0.4O₂.₇
SnCa_0.1Al_0.15B_0.45P_0.55O_Three.₉
SnY_0.1B_0.6P_0.6O_Three.₅₅
SnRb_0.2B_0.3P_0.4O₂.₅₅
[0055]
SnCs_0.2B_0.3P_0.4O₂.₅₅
SnCs_0.1B_0.4P_0.4O₂.₆₅
SnK_0.1Cs_0.1B_0.4P_0.4O₂.₇
SnBa_0.1Cs_0.1B_0.4P_0.4O₂.₇₅
SnMg_0.1K_0.1B_0.4P_0.4O₂.₇₅
SnCa_0.1K_0.1B_0.4P_0.5O_Three
SnBa_0.1K_0.1Al_0.1B_0.3P_0.4O₂.₇₅
SnMg_0.1Cs_0.1Al_0.1B_0.3P_0.4O₂.₇₅
SnCa_0.1K_0.1Al_0.1B_0.3P_0.4O₂.₇₅
SnMg_0.1Rb_0.1Al_0.1B_0.3P_0.4O₂.₇₅
[0056]
SnCa_0.1B_0.2P_0.2F_0.2O₂.₆
SnMg_0.1Cs_0.1B_0.4P_0.4F_0.2O_Three._Three
Sn_0.5Mn_0.5Mg_0.1B_0.9O₂.₄₅
Sn_0.5Mn_0.5Ca_0.1P_0.9O_Three.₃₅
Sn_0.5Ge_0.5Mg_0.1P_0.9O_Three.₃₅
Sn_0.5Fe_0.5Ba_0.1P_0.9O_Three.₃₅
Sn_0.8Fe_0.2Ca_0.1P_0.9O_Three.₃₅
Sn_0.3Fe_0.7Ba_0.1P_0.9O_Three.₃₅
Sn_0.9Mn_0.1Mg_0.1P_0.9O_Three.₃₅
[0057]
Sn_0.2Mn_0.8Mg_0.1P_0.9O_Three.₃₅
Sn_0.7Pb_0.3Ca_0.1P_0.9O_Three.₃₅
Sn_0.2Ge_0.8Ba_0.1P_0.9O_Three.₃₅
SnAl_0.1B_0.5P_0.5O_Three.₁₅
SnCs_0.1Al_0.4B_0.5P_0.5O_Three.₆₅
SnCs_0.1B_0.5P_0.5O_Three.₀₅
SnCs_0.1Ge_0.05B_0.5P_0.5O_Three.₁₅
SnCs_0.1Ge_0.05Al_0.3B_0.5P_0.5O_Three.₆₀
[0058]
Examples of the negative electrode active material that can be used with the above negative electrode material in a secondary battery include lithium metal and the above lithium alloy. The purpose of the combined use of the lithium metal and lithium alloy is to insert lithium ions into the negative electrode material in the battery, and does not use a dissolution and precipitation reaction of lithium metal or the like as the battery reaction.
[0059]
A conductive agent, a binder, a filler, etc. can be added to an electrode mixture (a positive electrode mixture and a positive electrode mixture). The conductive agent may be anything as long as it is an electron conductive material that does not cause a chemical change in the constructed battery. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal (copper, nickel, aluminum, silver (JP-A-63-148)) , 554) etc.) Conductive materials such as powders, metal fibers or polyphenylene derivatives (Japanese Patent Laid-Open No. 59-20,971) can be included as one kind or a mixture thereof. The combined use of graphite and acetylene black is particularly preferred. The addition amount is not particularly limited, but is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight. In the case of carbon or graphite, 2 to 15% by weight is particularly preferable.
[0060]
The binder is usually starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-di. Enter polymers (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluororubber, polyethylene oxide and other polysaccharides, thermoplastic resins, rubber elastic polymers and the like are used as one kind or a mixture thereof. The addition amount of the binder is preferably 2 to 30% by weight. Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0 to 30 weight% is preferable.
[0061]
Non-aqueous electrolytes used for the production of secondary batteries include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfate. Foxoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester (JP 60-23973), trimethoxymethane (JP 61 61) -4,170), dioxolane derivatives (JP-A Nos. 62-15771, 62-22,372, 62-108,474), sulfolane (JP-A No. 62-31,959), 3-methyl-2-oxa Lidinone (JP 62-44961), propylene carbonate derivatives (JP 62-290,069, 62-290,071), tetrahydrofuran derivatives (JP 63-32,872), A solvent in which at least one aprotic organic solvent such as diethyl ether (Japanese Patent Laid-Open No. 63-62,166) and 1,3-propane sultone (Japanese Patent Laid-Open No. 63-102,173) is mixed, and Lithium salts that are soluble in solvents, for example LiClO_Four, LiBF_Four, LiPF₆, LiCF_ThreeSO_Three, LiCF_ThreeCO₂, LiAsF₆, LiSbF₆, LiB_TenCl_Ten(JP 57-74,974), lower aliphatic lithium carboxylate (JP 60-41,773), LiAlCl4, LiCl, LiBr, LiI (JP 60-247265), lithium chloroborane (Japanese Patent Laid-Open No. 61-165,957) and lithium tetraphenylborate (Japanese Patent Laid-Open No. 61-214,376) and the like. Among them, a mixture of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate is mixed with LiCF._ThreeSO_Three, LiClO_Four, LiBF_FourAnd / or LiPF₆The amount of these electrolytes preferably added to the battery is not particularly limited, but can be used depending on the amount of the positive electrode active material and the negative electrode active material and the size of the battery. The volume ratio of the solvent is not particularly limited, but is 0.4 / 0.6 to 0.6 / 0.4 in the case of a mixed solution of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate. (The mixing ratio when both 1,2-dimethoxyethane and diethyl carbonate are used is preferably 0.4 / 0.6 to 0.6 / 04). The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.
[0062]
Among the above electrolytic solutions, particularly preferable as the electrolytic solution composition in terms of the effect of improving the charge / discharge cycle life of the secondary battery is at least ethylene carbonate as a solvent, and at least LiPF.₆As a lithium salt, and another preferred composition is at least LiPF using at least ethylene carbonate and diethyl carbonate as a solvent.₆Is a composition containing lithium as a lithium salt, and another preferred composition is at least LiPF using both ethylene carbonate and dimethyl carbonate as a solvent.₆In the form of a lithium salt.
[0063]
In addition to the electrolytic solution, the following organic solid electrolyte can also be used. For example, a polyethylene oxide derivative or a polymer containing the derivative (Japanese Patent Laid-Open No. 63-135447), a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ionic dissociation group (Japanese Patent Laid-Open Nos. 62-254,302 and 62- 254,303, 63-193,954), a mixture of an ion-dissociating group-containing polymer and the above aprotic electrolyte (US Pat. Nos. 4,792,504, 4,830,939, JP, Sho 62-22,375, 62-22,376, 63-22,375, 63-22,776, JP-A-1-95,117), phosphate polymer (JP-A) 61-256, 573) is effective. Furthermore, there is a method of adding polyacrylonitrile to the electrolytic solution (Japanese Patent Laid-Open No. 62-278,774). In addition, a method using an inorganic and organic solid electrolyte in combination (Japanese Patent Laid-Open No. 60-1,768) is also known.
[0064]
As a separator used for the secondary battery, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made from olefin polymers such as polypropylene, glass fibers or polyethylene are used because of their organic solvent resistance and hydrophobicity. A range useful for batteries is generally used as the pore diameter of the separator. For example, 0.01 to 10 μm is used. The thickness of the separator is generally used in the battery range. For example, 5 to 300 μm is used.
[0065]
When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.
[0066]
In order to improve discharge and charge / discharge characteristics, it is known to add the following compounds to the electrolyte. For example, pyridine (JP 49-108,525), triethyl phosphite (JP 47-4,376), triethanolamine (JP 52-72,425), cyclic ether (JP No. 57-152,684), ethylenediamine (JP 58-87,777), n-glyme (JP 58-87,778), hexaphosphoric triamide (JP 58-87,779). ), Nitrobenzene derivatives (JP-A 58-214,281), sulfur (JP-A 59-8,280), quinoneimine dyes (JP-A 59-68,184), N-substituted oxazolidinones and N, N'-substituted imidazolidinone (JP 59-154,778), ethylene glycol dialkyl ether (JP 59-205,167), quaternary ammonium salt (special Sho 60-30,065), polyethylene glycol (JP 60-41,773), pyrrole (JP 60-79,677), 2-methoxyethanol (JP 60-89,075). ), Aluminum trichloride (Japanese Patent Laid-Open No. 61-88,466), a monomer of conductive polymer electrode active material (Japanese Patent Laid-Open No. 61-161,673), triethylenephosphonamide (Japanese Patent Laid-Open No. 61-208, 758), trialkylphosphine (JP 62-80,976), morpholine (JP 62-80,977), aryl compounds having a carbonyl group (JP 62-86,673). Hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,575), bicyclic tertiary amine (JP 62-217,578), oi (JP 62-287,580), quaternary phosphonium salts (JP-63-121,268), and a tertiary sulfonium salt (JP 63-121,269).
[0067]
In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte (Japanese Patent Laid-Open No. 48-36,632). In addition, carbon dioxide gas can be included in the electrolytic solution to make it suitable for high-temperature storage (Japanese Patent Laid-Open No. 59-134,567).
[0068]
The mixture of the positive electrode and the negative electrode may contain an electrolytic solution or a supporting salt. For example, a method is known in which the ion conductive polymer, nitromethane (Japanese Patent Laid-Open No. 48-36,633), and an electrolytic solution (Japanese Patent Laid-Open No. 57-124,870) are included.
[0069]
In addition, the surface of the positive electrode active material can be modified. For example, the surface of a metal oxide is treated with an esterifying agent (Japanese Patent Laid-Open No. 55-163,779) or a chelating agent (Japanese Patent Laid-Open No. 55-163,780), or a conductive polymer (Japanese Patent Laid-Open No. 58-163,188 and 59-14,274), and a method of modifying by coating the surface layer of polyethylene oxide or the like (Japanese Patent Laid-Open No. 60-97,561). Similarly, the surface of the negative electrode active material can be modified. For example, an ion conductive polymer or a polyacetylene layer can be coated (Japanese Patent Laid-Open No. 58-111,276), or surface treatment can be performed with a Li salt (Japanese Patent Laid-Open No. 58-142,771).
[0070]
The current collector of the electrode active material may be anything as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. For example, in addition to stainless steel, nickel, aluminum, titanium, calcined carbon, etc. as materials for the positive electrode, the surface of aluminum or stainless steel is treated with carbon, nickel, titanium, or silver. In addition to stainless steel, nickel, copper, titanium, aluminum, calcined carbon, etc., the surface of copper or stainless steel treated with carbon, nickel, titanium or silver), Al—Cd alloy, or the like is used. Oxidizing the surface of these materials is also used. As the shape, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used in addition to the foil. The thickness is not particularly limited, but a thickness of 5 to 100 μm is used.
[0071]
FIG. 1 is a cross-sectional view of a cylinder type battery. The battery shape can be applied to both cylinders and corners. A cylindrical battery can be manufactured by making the winding core into a cylinder shape, and a rectangular battery can be manufactured by making the winding core into a square shape. The battery is formed by inserting the positive electrode sheet 3 and the negative electrode sheet 2 wound together with the separator 4 into the battery can 1, electrically connecting the battery can 1 and the negative electrode sheet 2, and injecting and sealing the electrolyte. The terminal cap 13 also serves as a positive electrode terminal and is fitted into the upper opening of the battery can 1 via the gasket 7. The positive electrode sheet 3 is electrically connected to the terminal cap 13 via a positive electrode lead 8, a welding plate 15, an explosion-proof valve body 9, a current cutoff switch 10, and a positive temperature coefficient resistance (hereinafter referred to as PTC) ring 11.
[0072]
In the sealing body, the terminal cap 13, the PTC ring 11, the current cutoff switch 10, and the explosion-proof valve body 9 are stacked in order from the top, and are fitted and supported by the gasket 7. The terminal cap 13 is a surface exposed portion of the battery, and the explosion-proof valve body 9 is inside the battery. The insulating cover 16 covers the upper surface of the explosion-proof valve body 9. The current cutoff switch 10 includes a first conductive body 10a, a second conductive body 10b, and an insulating ring 10c.
[0073]
The electrode group is obtained by winding the positive electrode sheet 3 and the negative electrode sheet 2 with the separator 4 interposed therebetween. The upper insulating plate 6 is disposed between the electrode group and the explosion-proof valve body 9. The upper insulating plate 6 insulates the electrode group and the sealing body, and insulates the electrode group and the battery can 1. A lower insulating plate 5 is disposed between the electrode group and the battery can 1 to insulate the electrode group from the battery can 1.
[0074]
The PTC ring 11 has a function of cutting off current by increasing resistance when the temperature inside the battery rises. The current cutoff switch 10 is a laminated structure of a first conducting body 10a, an insulating ring 10c, and a second conducting body 10b. The first conducting body 10a is disposed on the explosion-proof valve body 9 side and has a through hole. The conductive body 10b is arranged on the PTC ring 11 side, that is, the terminal cap 13 side, and has a structure having a through hole. The first conductor 10a and the second conductor 10b are electrically connected at the center, and have a thin portion around the connection portion of the first conductor 10a. The explosion-proof valve body 9 can be deformed to the side opposite to the electrode group side when the internal pressure is increased, and may be anything that can push up the central connection portion of the first conductive body 10a. When the internal pressure rises due to an abnormal reaction in the battery, the explosion-proof valve body 9 is deformed to break the connecting portion between the first conducting body 10a and the second conducting body 10b of the current cutoff switch 10 to cut off the current. If it increases, the thin part of the explosion-proof valve body 9 is destroyed and the pressure is released. At this time, since the current cut-off switch 10 is arranged on the side opposite to the electrode group side of the explosion-proof valve body 9, even if a spark occurs in the cut-off portion, the battery is prevented from rupture due to ignition of the electrolyte vapor. Is done.
[0075]
The battery shape can be applied to any of coins, buttons, sheets, cylinders, and corners. In coins and buttons, a mixture of a positive electrode active material and a negative electrode active material is used after being pressed into a pellet shape. In the sheet, cylinder, and corner, the positive electrode active material and the negative electrode active material mixture are applied onto a current collector, dried, dehydrated, and pressed. The coating thickness is determined by the size of the battery, and is preferably 10 to 500 μm in a compressed state after drying.
[0076]
Applications of non-aqueous secondary batteries are not particularly limited. For example, when installed in electronic devices, color notebook computers, monochrome notebook computers, pen input computer pocket (palmtop) computers, notebook word processors, pocket word processors, electronic books Player, mobile phone, cordless phone, pager, handy terminal, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electric shaver, electronic translator, automobile Examples include telephones, transceivers, power tools, electronic notebooks, calculators, memory cards, tape recorders, radios, backup power supplies, and memory cards. Others for consumer use include automobiles, electric vehicle motors, lighting equipment, toys, game equipment, road conditioners, irons, watches, strobes, cameras, medical equipment (pacemakers, hearing aids, shoulder grinders, etc.). Furthermore, it can be used for various military use and space use. It can also be combined with solar cells.
[0077]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples of battery fabrication. However, the scope of the present invention is not limited to these examples as long as the gist of the invention is not exceeded.
[0078]
[Example 1]
(Adjustment of positive electrode active material)
63.29 g of lithium carbonate powder (purity 99.38 wt%) (containing 0.004 wt% sulfate radical), 0.0111 g of lithium sulfate monohydrate, and 136.71 g of cobalt oxide (cobalt content 73.4 wt%) ( 0.005% by weight sulfate group) was put in an alumina crucible and mixed well to prepare a uniform mixture. The average particle diameter of cobalt oxide is about 3 μm. Next, this mixture was filled in an alumina crucible, put in an electric heating furnace, heated in the atmosphere, and maintained at 940 ° C. for firing. The obtained fired product was cooled in the air and then pulverized, and 0.01 wt% sulfate group-containing lithium cobalt oxide LiCoO.₂(Positive electrode active material C-1) was obtained.
[0079]
Cathode active materials C-2 to C-12 of [Table 1] having different sulfate radical contents and the same as the cathode active material C-1 except that the sulfate radical content and the type and amount of sulfate used are different, and comparison- 1 and Comparative-2 were obtained.
[0080]
[Table 1]

[0081]
Here, A is calcium sulfate dihydrate, and B is tetrabutylammonium hydrogen sulfate.
[0082]
In the positive electrode active materials C-1 to C-7 and Comparative-1 and Comparative-2, the concentration of sulfate radicals is changed by adjusting the amount of lithium hydrogen sulfate 1 added. The positive electrode active materials C-8 to C-10 change the sulfate group content in lithium carbonate or cobalt oxide. The positive electrode active materials C-11 and C-12 change the sulfate to be added.
[0083]
The sulfate radical was quantified by the following method.
Weigh 0.5 g of sample into a 30 ml beaker, add 6 ml of (1 + 1) nitric acid and 4 ml of (1 + 1) hydrogen peroxide, heat on a hot plate and dissolve completely. Then, after allowing to cool, transfer to a 100 ml volumetric flask and make a constant volume. Furthermore, it diluted 10 times and the sulfate radical was quantified with the ion chromatograph (The US DONEEX company make, 2000i / s type | mold).
[0084]
(Synthesis example of composite metal oxide as negative electrode material, melting method)
67.4 g of SnO, B₂O_Three17.4 g, Sn₂P₂O₇Were mixed and sufficiently ground and mixed in an automatic mortar, then set in an alumina crucible and baked at 1000 ° C. for 10 hours in an argon gas atmosphere. After firing, it is rapidly cooled at a rate of 100 ° C./min, and a yellow transparent glassy negative electrode active material precursor SnB_0.5P_0.5O_Three(Compound A-1) was obtained. When X-ray diffraction of the active material was measured, it showed a broad diffraction band in the region of 2θ = 20-35 ° under the irradiation of Cu-α ray, but a sharp diffraction line attributed to the crystal structure was detected. Thus, the active material structure was found to be amorphous (amorphous).
[0085]
(Production example of electrode mixture sheet)
The positive electrode active material compound C-1 was used as the positive electrode mixture, 6.7% by weight of acetylene black with respect to the positive electrode active material, and 3.3% by weight of an aqueous dispersion of polytetrafluoroethylene as the binder, Water was added to a mixture of 1.1% by weight of sodium polyacrylate and kneaded, and the resulting slurry was applied to both surfaces of a 30 μm thick aluminum film (positive electrode current collector) to prepare a positive electrode sheet. As a result of drying and pressing the coated sheet, the coating amount of the dry film was 230 g / m per side.²The thickness of the coating film was approximately 90 μm per side. An electrode mixture sheet was prepared in the same manner using the positive electrode active materials C-2 to C-12 and Comparative-1 and Comparative-2 described in [Table 1].
[0086]
86% by weight of compound A-1 as a negative electrode active material precursor, 3% by weight of flake graphite, 6% by weight of acetylene black, 4% by weight of an aqueous dispersion of styrene-butadiene rubber as a binder and 1% by weight of carboxymethyl cellulose % Was added to the mixture and kneaded with a homogenizer at 10,000 rpm for 10 minutes or more to prepare a negative electrode mixture slurry. The obtained slurry was applied to both sides of a 18 μm thick copper film (negative electrode current collector) to prepare a negative electrode sheet. As a result of drying and pressing the coated sheet, the coating amount of the dry film was approximately 70 g / m per side.²The thickness of the coating film was approximately 30 μm per one side.
[0087]
Next, a protective layer (average thickness 5 μm) made of a 1: 4 (weight ratio) mixture of scaly graphite and aluminum oxide is applied to the surface of the active material layer of the negative electrode sheet, and the negative electrode with the surface protective layer A sheet was produced.
[0088]
(Cylinder type battery production example)
A surface protective layer on both sides of a negative electrode sheet obtained by cutting a metal Li foil having a thickness of 35 μm into pieces having a width of 5 mm and a length of 37 mm and applying the negative electrode active material precursor A-1 in dry air having a dew point of −60 ° C. A 2 mm regular interval (gap) was placed on top of the substrate using a pressure roller. The amount of Li attached to the negative electrode sheet was approximately 110 mg as a weight. This lithium is used for electrolytically inserting lithium into the negative electrode active material precursor in the battery and converting the negative electrode active material precursor into an active material.
[0089]
The positive electrode sheet was cut to a width of 35 mm, the negative electrode sheet was cut to a width of 37 mm, and aluminum and nickel lead plates were spot welded to the ends of the sheet, respectively. Dehydrated and dried at 2 ° C. for 2 hours. As shown in the cross-sectional view of the battery in FIG. 1, the positive electrode sheet 3 that has been dehydrated and dried, the porous polyethylene film 4 as the separator, the negative electrode sheet 2 that has been dehydrated and dried, and the separator 4 are laminated in this order. Wound in a spiral. This wound body was housed in a nickel-plated iron-bottomed cylindrical battery can 1 (also serving as a negative electrode terminal). In this battery can 1, 1 mol / liter LiPF is used as an electrolyte.₆(A 2: 2: 6 (volume ratio) mixture of ethylene carbonate, butylene carbonate, and dimethyl carbonate) was injected.
[0090]
A battery lid 13 having a positive electrode terminal was caulked through a gasket 7 to produce a cylindrical battery having a diameter of 14 mm and a height of 50 mm. The positive electrode terminal 13 was connected to the positive electrode sheet 3 and the battery can 1 was connected to the negative electrode sheet 2 in advance by a lead terminal.
[0091]
Batteries using the respective positive electrode active materials shown in [Table 1] were produced by the above method.
[0092]
The battery produced as described above is a battery precursor in which the process of electrochemically inserting lithium on the coating sheet protective layer into the negative electrode active material precursor is not completed. Therefore, an operation for converting the battery precursor into a negative electrode active material by inserting lithium into the negative electrode active material precursor and making the battery precursor a chargeable / discharge cycleable secondary battery was performed as follows.
[0093]
The battery precursor was allowed to stand at room temperature for 12 hours, precharged for 1 hour under a constant current of 0.1 A, and then aged at 50 ° C. for 10 days. In this aging step, it was confirmed that Li supported on the negative electrode was dissolved and inserted into the negative electrode active material precursor.
[0094]
2 mA / cm for activation of this battery²The battery was charged to 4.2 V at room temperature. Further, the battery was kept at 55 ° C. in a charged state, and aging was performed for 3 days.
[0095]
The above batteries were charged with a charge end voltage of 4.2 V (open circuit voltage (OCV)), a discharge end voltage of 2.8 V (circuit voltage), and 2 mA / cm.²The battery was repeatedly charged and discharged under the condition of a current density (equivalent to 0.2 C). Also, the battery is 10 mA / cm²When the charge / discharge cycle was performed at a current of (1.0 C), the maintenance ratio relative to the initial capacity after the end of 300 cycles was measured, and the cycle life of the battery was evaluated.
[0096]
The results of cycle life evaluation of the above batteries are summarized in [Table 2].
[0097]
[Table 2]

[0098]
The batteries 1 to 7 and 9 to 14 using the positive electrode active materials C-1 to C-12 having a sulfate radical content of 0.01 to 4.9% by weight have a high cycle retention rate (lifetime), and cycle characteristics. Is excellent. Since the positive electrode active material (Comparative-1) had a sulfate radical content of 0.005% by weight and was too small, the cycle retention rate was low. Since the positive electrode active material (Comparative-2) had a sulfate radical content of 6.0% by weight and was too much, the cycle retention rate was low.
[0099]
The concentration of the sulfate radical contained in the positive electrode active material is preferably 0.01% by weight to 5% by weight, more preferably 0.05% by weight to 2% by weight, and particularly preferably 0.1% by weight to 1% by weight. .
[0100]
  The amount of sulfate added may be adjusted as shown in the positive electrode active materials C-1 to C7, or the positive electrode active material (lithium carbonate or oxidation) as shown in the positive electrode active materials C-8 to C-10. The content of sulfate radicals in (cobalt) may be adjusted..
[0101]
[Example 2]
The positive electrode active material number comparison-1 of Example 1 was used as the positive electrode mixture, 6.7% by weight of acetylene black with respect to the positive electrode active material, and an aqueous dispersion of polytetrafluoroethylene as the binder 3.3 % By weight and 1.1% by weight sodium polyalkali acid are added, lithium sulfate monohydrate is added to the active material so that the sulfate radical is 0.005% by weight, and water is added to the mixture. After kneading, an electrode sheet and a battery 15 were prepared and evaluated in the same manner as in Example 1.
[0102]
Batteries 16 to 22 shown in [Table 3] were obtained and evaluated in the same manner except that the amount of lithium sulfate monohydrate added was different.
[0103]
[Table 3]

[0104]
  Cathode active materialAdd lithium sulfate toEven when a positive electrode mixture was prepared by adding a sulfate group after firing, the cycle characteristics of the positive electrode having a predetermined amount of sulfate group concentration were excellent.
[0105]
Example 3
92% by weight of graphite having an average particle size of about 5 μm as a negative electrode active material, 3% by weight of acetylene black as a conductive agent, 4% by weight of polyvinylidene fluoride and 1% by weight of carboxymethyl cellulose as binders In addition, a slurry was obtained by kneading with water as a medium. This was applied to both sides of a 10 μm thick copper film, dried and pressed to prepare a negative electrode sheet. A battery was prepared and evaluated in the same manner as the battery prepared in Example 1 except that the Li foil was used without adhering to the negative electrode sheet. As a result, the cycle life of the battery containing a sulfate group was excellent as in Example 1.
[0108]
【The invention's effect】
  A lithium-containing composite oxide obtained by adding lithium sulfate to a positive electrode active material containing a Li source and an M source (M is Co or Ni) and firing, and is 0.01 wt% or more and 5 wt% or lessIf a positive electrode active material containing a sulfate group is used in a secondary battery, a secondary battery having excellent cycle life can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylinder type battery used in Examples.
[Explanation of symbols]
1 Battery can (also serves as negative electrode terminal)
2 Negative electrode sheet
3 Positive electrode sheet
4 Separator
5 Lower insulation plate
6 Upper insulation plate
7 Gasket
8 Positive lead
9 Explosion-proof valve body
10 Current interrupt switch
11 PTC ring
13 Battery cover (also serves as positive terminal)
15 Welding plate
16 Insulation cover

Claims (6)

The positive electrode active material is Li source and M source (M is Co or Ni) and lithium-containing composite oxide obtained by firing the addition of lithium sulfate to the cathode active material a material containing 0.01% by weight or more, 5 A positive electrode active material for a lithium ion non-aqueous electrolyte secondary battery, characterized by containing a sulfate group of not more than wt% . In a secondary battery including a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte containing a lithium salt, the positive electrode is fired by adding lithium sulfate to a positive electrode active material containing a Li source and an M source (M is Co or Ni). A lithium ion non-aqueous electrolyte secondary battery comprising a lithium-containing composite oxide obtained by the method and containing 0.01 wt% or more and 5 wt% or less of a sulfate group . (A) preparing a positive electrode active material containing a Li source and an M source (M is Co or Ni);
A step of firing the addition of lithium sulfate to (b) the positive electrode active material,
Only containing 0.01 wt% or more, to produce a positive electrode active material containing 5 wt% or less of the sulfate group, method for producing a cathode active material for a lithium ion nonaqueous electrolyte secondary battery. Between the steps (a) and (b),
( C ) measuring the concentration of sulfate radicals contained in the positive electrode active material ,
The method for producing a positive electrode active material for a claim 3 lithium ion nonaqueous electrolyte secondary battery according including. 5. The method for producing a positive electrode active material according to claim 4, wherein the step ( b ) is performed by adding lithium sulfate to the positive electrode active material according to the measurement result, adjusting the concentration of sulfate radicals, and firing. (A) firing a positive electrode active material containing a Li source and an M source (M is Co or Ni);
(B) adding lithium sulfate to the fired positive electrode active material to adjust the positive electrode mixture ;
Only containing 0.01 wt% or more, to produce a positive electrode mixture containing 5 wt% or less of the sulfate group, method for producing a lithium ion nonaqueous electrolyte secondary battery positive electrode mixture.

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