WO2023070992A1 - 电化学装置及包括其的电子装置 - Google Patents

电化学装置及包括其的电子装置 Download PDF

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WO2023070992A1
WO2023070992A1 PCT/CN2022/076462 CN2022076462W WO2023070992A1 WO 2023070992 A1 WO2023070992 A1 WO 2023070992A1 CN 2022076462 W CN2022076462 W CN 2022076462W WO 2023070992 A1 WO2023070992 A1 WO 2023070992A1
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positive electrode
active material
lithium
electrochemical device
formula
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PCT/CN2022/076462
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French (fr)
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周墨林
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宁德新能源科技有限公司
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Priority to CN202280002550.XA priority Critical patent/CN115336068A/zh
Priority to EP22884909.7A priority patent/EP4425598A1/en
Priority to JP2024524759A priority patent/JP2024539299A/ja
Publication of WO2023070992A1 publication Critical patent/WO2023070992A1/zh
Priority to US18/645,924 priority patent/US20240282960A1/en

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    • H—ELECTRICITY
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of energy storage, in particular to an electrochemical device and an electronic device including the same.
  • a solid electrolyte interface (SEI) will form on the surface of the negative electrode, resulting in irreversible capacity loss, thereby reducing the energy density of lithium-ion energy storage devices.
  • SEI solid electrolyte interface
  • the first charge-discharge cycle will consume about 10% of the active lithium source; while using high-capacity negative electrode materials, such as alloys (silicon or tin, etc.), oxides ( Silicon oxide or tin oxide) and amorphous carbon anode, the consumption of active lithium source will be further aggravated during the first charge-discharge cycle.
  • the patent with the authorized notification number CN1290209C proposes a method for replenishing lithium in the negative electrode.
  • the lithium metal powder, the negative electrode material and the non-aqueous liquid are mixed to form a slurry, and the slurry is coated on the negative electrode current collector, and then dried and rolled.
  • the assembly of the energy storage device is completed through processes such as pressure and liquid injection.
  • the production process requires that it is not compatible with Non-aqueous organic solvents for lithium reactions and strict control of moisture are required, which increases the difficulty of the process.
  • the FMC company of the United States has carried out certain improvement processing to lithium powder, and the stabilized lithium metal powder (SLMP) that it produces has better stability, but it also can only exist stably for a few hours in dry air, and this time limit Strict requirements are put forward for the manufacturing process of lithium-ion batteries (including pulping, coating, drying, slitting, rolling, winding, liquid injection, etc.).
  • SLMP also has strict requirements on the humidity and oxygen content of the operating environment. If the dry method is used, the lithium powder will easily float in the air, posing a safety hazard; if the wet method is used, it is also necessary to select a non-aqueous solvent and control the moisture.
  • the relatively safer and easier-to-operate positive electrode lithium supplementation method has attracted more and more attention from the industry.
  • the patent with the publication number CN104037418A discloses a positive electrode lithium supplement material based on lithium oxygen compound, lithium source and alkyllithium, but the decomposition potential of lithium oxygen compound is relatively high, and oxygen and other by-products are generated during the decomposition process , affecting battery life.
  • the patent with the authorized notification number CN101877417B discloses Li 2 NiO 2 lithium supplement materials. This type of lithium supplement material has a high specific capacity, a simple preparation method, and can well supplement active lithium. However, this type of lithium supplement material is charged in the first cycle.
  • inactive components will remain on the pole piece, which is not conducive to further improving the energy density of lithium-ion batteries.
  • a large amount of active lithium is intercalated into the negative electrode, resulting in a further decrease in the real potential of the negative electrode, and the solvent in the electrolyte continues to undergo a reduction reaction at the negative electrode, resulting in a continuous increase in impedance, which in turn affects cycle performance.
  • the present application provides an electrochemical device in an attempt to solve at least one problem existing in the related art, at least to some extent.
  • the application provides an electrochemical device, which includes a positive pole, a negative pole, a separator and an electrolyte, wherein the positive pole comprises a positive active material layer, and the positive active material layer comprises a positive active material shown in formula (1): Li 1+r Ni 1-pq M1 p M2 q O 2-s M3 s
  • M1 and M2 are each independently at least one of Co, Mn, Fe, Ti, Al, V, Cr, Nb, Zr, La or Y
  • M3 is S, At least one of N, F, Cl or Br, wherein the resistance of the positive electrode is R ⁇ , the compacted density of the positive electrode is P g/cm 3 , and the density of one side of the positive electrode is Q g/1540.25mm 2 , and the positive electrode satisfies the formula (2): 3.5 ⁇ R ⁇ P/Q ⁇ 30
  • the positive electrode further satisfies formula (3): 5.0 ⁇ R ⁇ P/Q ⁇ 12 formula (3).
  • R satisfies R ⁇ 3.
  • R satisfies R ⁇ 1.5.
  • P satisfies 2.8 ⁇ P ⁇ 3.6.
  • Q satisfies 0.16 ⁇ Q ⁇ 0.32.
  • the weight percentage of fluoroethylene carbonate is greater than 0 and less than or equal to 15%.
  • the weight percentage of the positive electrode active material is 80% to 98%.
  • the positive electrode active material comprises a phase A and a phase B
  • the phase A has a characteristic diffraction peak A1 of the (003) crystal plane at 17° to 19°
  • the phase A B appears at 16° to 18°
  • the characteristic diffraction peak B1 of the (001) crystal plane, the intensity I A of the characteristic diffraction peak A1 and the intensity I B of the characteristic diffraction peak B1 satisfy the formula (4): 0 ⁇ IA / I B ⁇ 100 Formula (4).
  • the present application further provides an electronic device, which includes any one of the above electrochemical devices.
  • FIG. 1 is an X-ray diffraction (XRD) pattern of the positive electrode active material Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 2 in Example 1 of the present application.
  • XRD X-ray diffraction
  • FIG. 2 is the first charging curves of Example 2 and Comparative Example 5 of the present application.
  • the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and account for minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurred exactly as well as instances in which the event or circumstance occurred with close approximation.
  • the term when used in conjunction with a numerical value, the term may refer to a range of variation of less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 10%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the difference between two numerical values is less than or equal to ⁇ 10% of the mean of the stated values (e.g., less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%), then the two values can be considered to be "substantially" the same.
  • a list of items linked by the terms “at least one of”, “at least one of”, “at least one of” or other similar terms may mean that the listed items any combination of .
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • an electrochemical device including a positive electrode, a negative electrode, a separator, and an electrolyte.
  • the electrochemical device is a lithium ion battery.
  • the electrochemical device of the present application has the advantages of high energy density, good rate performance and long cycle life.
  • the positive electrode in the electrochemical device of the present application comprises a kind of nickel-based positive electrode active material, and this nickel-based positive electrode active material has higher initial charge specific capacity, can replenish the active lithium caused by generating solid electrolyte interface (SEI). loss, thereby increasing the energy density of the electrochemical device.
  • the electrolyte in the electrochemical device of the present application contains fluoroethylene carbonate, which can make the negative electrode form a more uniform and dense SEI while replenishing lithium at the positive electrode, and reduce the continuous consumption of active lithium.
  • the resistance, compaction density and single-surface density of the positive electrode in the electrochemical device of the present application meet certain design requirements, which significantly improves the cycle life and rate performance of the electrochemical device.
  • the application provides an electrochemical device, which includes a positive pole, a negative pole, a separator and an electrolyte, wherein the positive pole comprises a positive active material layer, and the positive active material layer comprises a positive active material shown in formula (1):
  • M1 and M2 are each independently Co, Mn, At least one of Fe, Ti, Al, V, Cr, Nb, Zr, La or Y, M3 is at least one of S, N, F, Cl or Br, wherein the resistance of the positive electrode is R ⁇ , so
  • the compacted density of the positive electrode is P g/cm 3
  • the single surface density of the positive electrode is Q g/1540.25mm 2
  • the positive electrode satisfies the formula (2):
  • the electrolyte contains fluoroethylene carbonate.
  • the positive electrode active material Li 1+r Ni 1-pq M1 p M2 q O 2-s M3 s contains two phases, namely phase A and phase B.
  • Phase A for example, nickel cobalt lithium manganate (NCM)
  • Phase B for example, NCM after over-intercalation of Li
  • Phase A belongs to the R-3m space group and can be used as a positive electrode active material with high specific capacity.
  • Phase B for example, NCM after over-intercalation of Li
  • Phase B belongs to the F-3m1 space group, which has a high specific capacity, and can release a large amount of lithium ions to supplement active lithium during the first charge, so as to make up for the active lithium caused by the formation of SEI. loss, and transform into phase A after delithiation, and participate in subsequent charge-discharge cycles as the positive electrode active material.
  • the characteristic diffraction peak A1 of the (003) crystal plane appears in phase A at 17° to 19°
  • the characteristic diffraction peak B1 of the (001) crystal plane appears in phase B at 16° to 18°
  • the intensity I A of the characteristic diffraction peak A1 and the intensity I B of the characteristic diffraction peak B1 satisfy the formula (4):
  • I A / IB is about 0, about 0.01, about 0.05, about 0.1, about 0.13, about 0.15, about 0.2, about 0.5, about 1, about 5, about 10, about 15, about 20 , about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, about 65, about 70, about 75, about 80, about 85, about 90, about 95, about 99 or can It is a range composed of any two values above, such as about 0.01 to about 0.2, about 0.01 to about 10, about 0.1 to about 50, 0 to about 50 or about 0.1 to about 100.
  • the specific capacity of the positive electrode active material Li 1+r Ni 1-pq M1 p M2 q O 2-s M3 s depends on the size of r in Li 1+r Ni 1-pq M1 p M2 q O 2-s M3 s , r The larger the value, the higher the degree of over-intercalation of lithium, and the greater the specific capacity of the first charge. In some embodiments, the Ni content in the positive electrode active material Li 1+r Ni 1-pq M1 p M2 q O 2-s M3 s exceeds 50%.
  • s 0 in the positive electrode active material
  • M1 is Co
  • M2 is at least one of Mn or Al, for example, Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 2 , Li 1.2 Ni 0.6 Co 0.2 Mn 0.2 O 2 or Li 1.2 Ni 0.8 Co 0.08 Mn 0.1 Al 0.02 O 2 etc.
  • M1 in the positive electrode active material is Co
  • M2 is Mn
  • M3 is at least one of F or S, such as Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 1.95 F 0.05 or Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 1.9 S 0.0 5F 0.05 .
  • the positive electrode includes a positive electrode current collector, and the positive electrode current collector includes two opposite surfaces in its own thickness direction, and the positive electrode active material layer is arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes formula (1 ) shown in the positive electrode active material.
  • the weight percentage of the positive active material is about 80% to about 98% based on the total weight of the positive active material layer. In some embodiments, based on the total weight of the positive electrode active material layer, the weight percentage of the positive electrode active material is about 80%, about 82%, about 84%, about 86%, about 88%, about 90%, about 92%, About 94%, about 96%, about 98%, or a range that can be any two of the above values, such as about 80% to about 85%, about 80% to about 90, about 85% to about 95%, or about 90% to About 98% etc.
  • the resistance (R ⁇ ) of the positive electrode is the sheet resistance, which can be measured by the DC two-probe method.
  • m is the weight of the positive electrode active material layer in g
  • v is the volume of the positive electrode active material layer in cm 3 .
  • the volume v of the positive active material layer may be the product of the area Ar of the positive active material layer and the thickness of the positive active material layer.
  • the electrical resistance, compacted density, and single-sided areal density of the positive electrode are key parameters for designing and fabricating electrochemical devices. Excessive resistance of the positive electrode will deteriorate the cycle performance and rate performance of the electrochemical device. If the compaction density is too large or too small, the cycle performance and rate performance of the electrochemical device will be deteriorated.
  • R P/Q can be about 3.5, about 3.7, about 3.8, about 5, about 5.5, about 6, about 6.5, about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5, about 12, about 13, about 14, about 15, about 18, about 19, about 20, about 22, about 25, about 28, about 29, about 30 or It can be a range composed of any two values above, such as about 3.5 to about 10, about 3.7 to about 9, about 5 to about 8, about 5 to about 10, about 5 to about 15, about 8 to about 12, about 10 to About 12, about 10 to about 20, about 10 to about 30, about 15 to about 30, or about 20 to about 30.
  • the positive electrode further satisfies formula (3):
  • R P/Q can be about 5, about 5.5, about 6, about 6.5, about 7, about 7.5, about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about 11, about 11.5 , about 12, or a range consisting of any two of the above values, such as about 5 to about 8, about 5 to about 10, about 8 to about 12, or about 10 to about 12.
  • the resistance of the positive electrode is less than or equal to 3 ⁇ (ie, R ⁇ 3), to advantageously improve the cycle performance and rate performance of the electrochemical device.
  • R can be any value or range less than or equal to 3, for example, R can be less than or equal to 2.8, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, less than or equal to 1.2, less than or equal to 1, less than or equal to 0.8, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, or R can be about 3, about 2.8, about 2.5, about 2, About 1.8, about 1.5, about 1.2, about 1, about 0.8, about 0.6, about 0.5, about 0.3, about 0.1, etc.
  • the resistance of the positive electrode is less than or equal to 1.5 ⁇ (ie, R ⁇ 1.5).
  • the positive electrode has a compacted density greater than 2.8 g/cm 3 and less than or equal to 3.6 g/cm 3 , ie, 2.8 ⁇ P ⁇ 3.6.
  • P can be any value or range between greater than 2.8 and less than or equal to 3.6, for example, P can be greater than 2.8 and less than or equal to 3.0, greater than 2.8 and less than or equal to 3.5, greater than or equal to 3.0 and less than or equal to 3.3, greater than or equal to equal to 3.0 and less than or equal to 3.6, greater than or equal to 3.2 and less than or equal to 3.6, etc., or P may be about 2.85, about 2.9, about 3.0, about 3.1, about 3.2, about 3.3, about 3.4, about 3.5, about 3.6 or It may be a range composed of any two values above, for example, about 2.9 to about 3.3, about 3.0 to about 3.5, or about 2.9 to about 3.6.
  • the compaction density of the positive electrode within the above range is conducive to
  • the single surface density of the positive electrode is greater than 0.16g/1540.25mm 2 and less than 0.32g/1540.25mm 2 (that is, 0.16 ⁇ Q ⁇ 0.32), so as to ensure the improvement of the electrochemical device under the premise of charging and discharging capacity. cycle performance and rate performance.
  • Q can be any value or range between greater than 0.16 and less than 0.32, for example, Q can be greater than 0.16 and less than 0.30, greater than 0.16 and less than 0.28, greater than 0.16 and less than 0.25, greater than 0.16 and less than 0.20, greater than or equal to 0.20 and less than 0.32, greater than or equal to 0.25 and less than 0.32, greater than or equal to 0.30 and less than 0.32, or Q can be about 0.17, about 0.18, about 0.19, about 0.20, about 0.21, about 0.22, about 0.23, about 0.24, about 0.25, about 0.26, about 0.27, about 0.28, about 0.29, about 0.30, about 0.31, or a range consisting of any two values above, such as about 0.17 to about 0.31, about 0.18 to about 0.31, about 0.20 to about 0.31, about 0.25 to about 0.30.
  • the present application adds fluoroethylene carbonate to the electrolyte, so that the negative electrode forms a uniform and dense SEI film rich in LiF components, effectively suppressing the continuous loss of active lithium; at the same time, fluoroethylene carbonate Esters are more resistant to high-pressure oxidation on the positive side, further improving the cycle life of electrochemical devices.
  • the weight percentage of fluoroethylene carbonate is greater than 0 and less than or equal to 15%. In some embodiments, based on the total weight of the electrolyte, the weight percent of fluoroethylene carbonate can be any value or range between greater than 0 and less than or equal to 15%, for example, the weight percent of fluoroethylene carbonate can be About 0.1%, about 0.5%, about 1.0%, about 2.0%, about 3.0%, about 4.0%, about 5.0%, about 6.0%, about 7.0%, about 8.0%, about 9.0%, about 10.0%, about 11.0%, about 12.0%, about 13.0%, about 14.0%, about 15.0%, or a range consisting of any two values above, such as about 0.1% to about 15.0%, about 0.5% to about 15.0%, about 1% to About 15.0%, about 5% to about 10.0%, about 5% to about 15.0%, or about 10% to about 15.0%.
  • the electrochemical device of the present application realizes high energy density, excellent rate performance and Organic unity for long cycle life.
  • the positive active material layer further includes a binder.
  • the binder improves the bonding of the positive electrode active material particles to each other, and also improves the bonding of the positive electrode active material to the positive electrode current collector.
  • the binder includes styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol At least one of butyral (PVB), ethylene-vinyl acetate copolymer (EVA) or polyvinyl alcohol (PVA), but not limited thereto, and the adhesive can be selected according to actual needs.
  • the weight percentage of the binder is less than or equal to 2.0%, so as to obtain a lower positive electrode sheet resistance. In some embodiments, based on the total weight of the positive electrode active material layer, the weight percentage of the binder is about 2.0%, about 1.8%, about 1.5%, about 1.2%, about 1.0%, about 0.8%, about 0.5%, About 0.3%, about 0.1%, or a range consisting of any two values above, such as about 0.1% to about 2.0%, about 0.5% to about 2.0%, about 0.1% to about 1.0%, or about 1.0% to about 2.0% .
  • the positive electrode active material layer also includes a conductive agent
  • the conductive agent includes at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the conductive agent can be selected according to actual needs.
  • the weight percentage of the conductive agent is greater than or equal to 0.5%, so as to obtain a lower positive electrode sheet resistance. In some embodiments, based on the total weight of the positive electrode active material layer, the weight percentage of the conductive agent is greater than or equal to 0.5%, greater than or equal to 1.0%, or greater than or equal to 1.5%, and the like.
  • the positive electrode current collector can use metal foil or porous metal plate, such as aluminum, copper, nickel, titanium or silver or their alloy foil or porous plate, such as aluminum foil, but not limited thereto .
  • the thickness of the positive current collector is from about 5 ⁇ m to about 20 ⁇ m, for example, about 5 ⁇ m, about 6 ⁇ m, about 7 ⁇ m, about 8 ⁇ m, about 10 ⁇ m, about 12 ⁇ m, about 14 ⁇ m, about 16 ⁇ m, about 18 ⁇ m, about 20 ⁇ m or It may be in a range composed of any two values above, for example, about 6 ⁇ m to 18 ⁇ m or about 8 ⁇ m to about 16 ⁇ m.
  • the positive electrode active material layer can be produced by dry mixing the positive electrode active material and binder (conductive material and thickener used as needed) to form a sheet, and The obtained sheet is pressure-bonded to the positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is coated on the positive electrode current collector and dried.
  • binder conductive material and thickener used as needed
  • the positive electrode can be prepared by methods known in the art.
  • the positive electrode may be obtained by mixing a positive electrode active material, a conductive material, and a binder in a solvent to prepare an active material composition, and coating the active material composition on a positive electrode current collector.
  • the solvent may include N-methylpyrrolidone (NMP) and the like, but is not limited thereto.
  • the negative electrode may be a metal lithium sheet, or may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the negative active material layer includes a negative active material, and optionally includes a conductive agent, a binder, and a thickener.
  • the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn One or more of -O alloy, Sn, SnO, SnO 2 , lithium titanate Li 4 Ti 5 O 12 with a spinel structure, Li-Al alloy and metallic lithium.
  • MCMB mesophase microcarbon spheres
  • the conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may be styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl butyral, water-based acrylic resin, carboxymethyl cellulose, or polyacrylic acid (PAA). one or more.
  • the thickener may be carboxymethylcellulose.
  • the negative electrode in the electrochemical device of the present application is not limited to the above materials, and the present application can also use other materials that can be used as negative electrode active materials, conductive agents, binders and thickeners of lithium-ion batteries.
  • the negative electrode current collector can use materials such as metal foil or porous metal plate, such as copper, nickel, titanium or iron or their alloy foil or porous plate, such as copper foil.
  • the negative electrode can be prepared according to conventional methods in the art. Usually the negative electrode active material and optional conductive agent, binder and thickener are dispersed in a solvent, the solvent can be N-methylpyrrolidone or deionized water to form a uniform negative electrode slurry, and the negative electrode slurry is coated On the negative electrode current collector, the negative electrode sheet is obtained through drying, cold pressing and other processes.
  • a solvent can be N-methylpyrrolidone or deionized water to form a uniform negative electrode slurry
  • the negative electrode slurry is coated On the negative electrode current collector, the negative electrode sheet is obtained through drying, cold pressing and other processes.
  • the separator in the electrochemical device of the present application is not particularly limited, and any known porous structure separator with electrochemical stability and chemical stability can be selected, such as glass fiber, non-woven fabric, polyethylene (PE), polyester Single-layer or multi-layer films of one or more of propylene (PP) and polyvinylidene fluoride.
  • any known porous structure separator with electrochemical stability and chemical stability can be selected, such as glass fiber, non-woven fabric, polyethylene (PE), polyester Single-layer or multi-layer films of one or more of propylene (PP) and polyvinylidene fluoride.
  • the electrolytic solution in the electrochemical device of the present application includes organic solvent, electrolyte lithium salt and additives in addition to fluoroethylene carbonate. This application does not specifically limit the types of organic solvents and electrolyte lithium salts, which can be selected according to actual needs.
  • the organic solvent can be ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dicarbonate Propyl (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), vinylene carbonate (VC), methyl formate (MF), methyl acetate (MA ), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyric acid At least one of ethyl ester (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylethylsulfone (EMS) and diethylsulfone (ESE).
  • EC ethylene carbon
  • the electrolyte lithium salt can be lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), bisfluorosulfonimide Lithium (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium difluorooxalate borate (LiBOB), lithium difluorophosphate ( One or more of LiPO 2 F 2 ), lithium difluorooxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF4 lithium perchlorate
  • the solution may optionally include other additives, which may be any additives that can be used as lithium-ion batteries, and are not specifically limited here, and may be selected according to actual needs.
  • the additive may be ethylene carbonate (VEC), succinonitrile (SN), adiponitrile (AND), 1,3-propene sultone (PST), sulfonate cyclic One or more of quaternary ammonium salt, tris(trimethylsilane) phosphate (TMSP) and tris(trimethylsilane) borate (TMSB).
  • the electrolyte in the electrochemical device of the present application can be prepared according to conventional methods in the art.
  • the organic solvent, electrolyte lithium salt, fluoroethylene carbonate and other optional additives are uniformly mixed to obtain an electrolyte solution, and the order of adding each material is not particularly limited.
  • electrolyte lithium salt, fluoroethylene carbonate and other optional additives are added into an organic solvent and mixed uniformly to obtain an electrolyte solution.
  • the electrolyte lithium salt can be added into the organic solvent first, and then the fluoroethylene carbonate and other optional additives can be added into the organic solvent separately or simultaneously.
  • the electrochemical device of the present application can be prepared according to conventional methods in the art.
  • the above-mentioned positive electrode, separator and negative electrode are stacked in order, so that the separator is between the positive electrode and the negative electrode to play the role of isolation, and the battery core can be obtained, or the battery core can be obtained after winding; the battery core is placed in the The electrolyte solution is injected into the package shell and sealed to obtain an electrochemical device.
  • the electrochemical device described by the present application is applicable to electronic devices in various fields.
  • the application of the electrochemical device of the present application is not particularly limited, and it can be used for any application known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • Negative electrode active material artificial graphite, silicon oxide, binder polyacrylic acid and conductive carbon black are mixed according to mass ratio 85.9:10:2.8:1.3, solvent deionized water is added, and negative electrode slurry is obtained under the action of vacuum mixer; The negative electrode slurry is evenly coated on the negative electrode current collector copper foil; then transferred to an oven for drying at a temperature of 120°C, and then subjected to cold pressing and slitting to obtain the negative electrode.
  • Ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were uniformly mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Dissolve 1 mol/L LiPF 6 in the above organic solvent, then add a certain amount of fluoroethylene carbonate, and mix evenly to obtain an electrolyte solution.
  • a polypropylene film (provided by Celgard) with a thickness of 14 ⁇ m was used as the release film.
  • the lithium-ion batteries of Examples 1 to 21 and Comparative Examples 1 to 5 Prepare the lithium-ion batteries of Examples 1 to 21 and Comparative Examples 1 to 5 according to the above-mentioned preparation method, the positive electrode active material of each embodiment and each comparative example, the resistance of the positive electrode, the compacted density of the positive electrode, the single surface density of the positive electrode, and The weight percent of fluoroethylene carbonate in the electrolyte relative to the total weight of the electrolyte is shown in Table 1 below, and the prepared lithium-ion battery was tested as follows.
  • the positive electrode active material in Comparative Example 5 is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , and the other parameters are exactly the same as in Example 2. In the following high-temperature cycle performance test, the first charging curves of Example 2 and Comparative Example 5 were drawn.
  • Test the resistance of the positive electrode with Hiji BT3562 resistance tester The specific test steps include: clamp the positive electrode between the two conductive terminals of the internal resistance tester, and apply pressure to fix it, and test the resistance R of the positive electrode.
  • the probe is connected to the positive electrode.
  • the contact area of the pole piece is 49 ⁇ mm 2
  • the diameter of the conductive terminal is 14mm
  • the applied pressure is 15MPa-27MPa
  • the sampling time ranges from 5s to 17s.
  • the lithium-ion battery in a constant temperature box at 45°C, charge the lithium-ion battery at a constant current rate of 1.5C to 4.3V, and then charge it at a constant voltage at 4.3V until the current is less than or equal to 0.05C, and then charge it at a rate of 1C Constant current discharge to 3.0V, this is a charge-discharge cycle, the lithium-ion battery is charged and discharged according to the above method, and the discharge capacity of the first cycle of the lithium-ion battery and the discharge capacity of each subsequent cycle are recorded until the lithium-ion battery The discharge capacity of the battery decays to 80% of the discharge capacity of the first cycle, and the number of charge and discharge cycles at this time is recorded.
  • the 2C rate discharge capacity retention rate (%) of the lithium-ion battery 2C rate discharge capacity/0.2C rate discharge capacity ⁇ 100%.
  • Adopt X-ray diffraction tester Panalytical Holland, XPertPro MPD
  • set test conditions Cu K ⁇ radiation
  • the working current is 250mA
  • continuous scanning is adopted
  • the working voltage is 40kV
  • the scanning range 2 ⁇ is 10° ⁇ 70°
  • the step size is 0.1°
  • the scanning speed is 0.2 seconds/step.
  • the sample powder of the embodiment is subjected to diffraction test to confirm the sample phase.
  • FIG. 1 is an X-ray diffraction (XRD) pattern of the positive electrode active material Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 2 in Example 1 of the present application.
  • Figure 2 is the first charging curve of Example 2 and Comparative Example 5. It can be seen from Figure 2 that the positive electrode active material in the present application has a high first-cycle charging specific capacity, which can effectively compensate for the loss of active lithium caused by the generation of SEI. , thereby increasing the energy density of lithium-ion batteries.
  • Table 2 is the test results of the lithium ion batteries of Examples 1 to 21 and Comparative Examples 1 to 5.
  • the positive electrode active material of the present application has a high first-cycle charge specific capacity, which can effectively compensate for the loss of lithium caused by the formation of SEI, thereby increasing the energy density of the battery.
  • references to “some embodiments”, “partial embodiments”, “one embodiment”, “another example”, “example”, “specific example” or “partial example” in the entire specification mean that At least one embodiment or example in this application includes a specific feature, structure, material or characteristic described in the embodiment or example.
  • descriptions that appear throughout the specification such as: “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example In”, “in a particular example” or “example”, they are not necessarily referring to the same embodiment or example in this application.
  • the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及一种电化学装置和电子装置。电化学装置包括正极、负极、隔离膜和电解液，其中正极包含正极活性材料层，正极活性材料层包括式(1)所示的正极活性材料：Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s式(1)，在式(1)中，0＜r≤1，0＜p＜1，0＜q＜1，0＜p+q＜0.5，0≤s＜0.2，M1和M2各自独立地为Co、Mn、Fe、Ti、Al、V、Cr、Nb、Zr、La或Y中的至少一种，M3是S、N、F、Cl或Br中的至少一种，其中正极的电阻为RΩ，正极的压实密度为Pg/cm 3，正极的单面面密度为Qg/1540.25mm 2，并且正极满足式(2)：3.5≤R·P/Q≤30式(2)，其中电解液包含氟代碳酸乙烯酯。

Description

电化学装置及包括其的电子装置 技术领域
本申请涉及储能技术领域，尤其涉及电化学装置及包括其的电子装置。
背景技术
锂离子电池在首次充放电循环过程中，其负极表面会形成固态电解质界面(SEI)，造成不可逆的容量损失，从而降低了锂离子储能器件的能量密度。在使用石墨作为负极材料的锂离子电池中，首次充放电循环会消耗大约10％的活性锂源；而在使用高比容量的负极材料，例如合金类(硅或锡等)、氧化物类(氧化硅或氧化锡)和无定形碳负极的锂离子电池中，首次充放电循环过程中的活性锂源的消耗会进一步加剧。
为了弥补首次充放电循环过程中的活性锂源的消耗，本领域的研究人员尝试通过负极补锂方法来改善锂离子电池。例如，授权公告号为CN1290209C的专利提出了一种负极补锂方法，将金属锂粉、负极材料和非水液体混合形成浆料，将浆料涂布到负极集流体上，然后经干燥，辊压和注液等工序完成储能器件的组装，这种方法虽然能提高锂离子电池的能量密度，但金属锂的反应活性极高，易与空气中的水分反应，因此生产工艺要求采用不与锂反应的非水有机溶剂并且需要严格控制水分，从而增大了工艺难度。美国的FMC公司对锂粉进行了一定的改进处理，其生产的稳定化金属锂粉(SLMP)具有更好的稳定性，但其在干燥空气中也仅能稳定存在几个小时，这个时间限制对于锂离子电池的制作工艺(包括调浆、涂布、烘干、分切、辊压、卷绕、注液等)提出了苛刻的要求。而且，SLMP对于操作环境湿度和氧含量的要求同样很严格，若采用干法操作，锂粉容易漂浮在空气中，具有安全隐患；若采用湿法操作，同样需要选择非水溶剂并控制水分。
鉴于负极补锂策略面临着巨大的挑战，相对更加安全和便于操作的正极补锂方法得到了产业界越来越多的关注。例如，公开号为CN104037418A的专利公开了一种基于锂氧化合物、锂源和烷基锂的正极补锂材料，但其中锂氧化合物的分解电位较高，且分解过程中产生氧气和其它副产物，影响电池寿命。授权公告号为CN101877417B的专利公开了Li 2NiO 2类补锂材料，这类补锂材料的比容量高，制备方法简单，可以很好地补充 活性锂，但这类补锂材料在首圈充电脱锂后会在极片上残留非活性组分，不利于进一步提升锂离子电池的能量密度。此外，在首次充电过程中，大量的活性锂嵌入负极，导致负极的真实电位进一步降低，并且电解液中的溶剂持续在负极发生还原反应，造成阻抗的持续增长，进而影响循环性能。
因此，如何使锂离子电池在提高能量密度的同时具有较好的循环和倍率性能是电池领域的研发重点。
发明内容
本申请提供一种电化学装置以试图在至少某种程度上解决至少一个存在于相关领域中的问题。
本申请提供了一种电化学装置，其包括正极、负极、隔离膜和电解液，其中所述正极包含正极活性材料层，所述正极活性材料层包括式(1)所示的正极活性材料：Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s式(1)，在式(1)中，0＜r≤1，0＜p＜1，0＜q＜1，0＜p+q＜0.5，0≤s＜0.2，M1和M2各自独立地为Co、Mn、Fe、Ti、Al、V、Cr、Nb、Zr、La或Y中的至少一种，M3是S、N、F、Cl或Br中的至少一种，其中所述正极的电阻为RΩ，所述正极的压实密度为P g/cm 3，所述正极的单面面密度为Q g/1540.25mm 2，并且所述正极满足式(2)：3.5≤R·P/Q≤30式(2)，其中所述电解液包含氟代碳酸乙烯酯。
根据本申请的一些实施例，所述正极进一步满足式(3)：5.0≤R·P/Q≤12式(3)。
根据本申请的一些实施例，R满足R≤3。
根据本申请的一些实施例，R满足R≤1.5。
根据本申请的一些实施例，P满足2.8＜P≤3.6。
根据本申请的一些实施例，Q满足0.16＜Q＜0.32。
根据本申请的一些实施例，基于所述电解液的总重量，氟代碳酸乙烯酯的重量百分比为大于0且小于等于15％。
根据本申请的一些实施例，基于所述正极活性材料层的总重量，所述正极活性材料的重量百分比为80％至98％。
根据本申请的一些实施例，所述正极活性材料包含物相A和物相B，所述物相A在17°至19°处出现(003)晶面的特征衍射峰A1，所述物相B在16°至18°处出现(001) 晶面的特征衍射峰B1，所述特征衍射峰A1的强度I A与特征衍射峰B1的强度I B满足式(4)：0≤I A/I B＜100式(4)。
本申请进一步提供了一种电子装置，其包括以上任一种电化学装置。
本申请的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1为本申请实施例1中的正极活性材料Li 1.2Ni 0.8Co 0.1Mn 0.1O 2的X射线衍射(XRD)图。
图2为本申请实施例2和对比例5的首次充电曲线图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在此所描述的实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
如本文中所使用，术语“大致”、“大体上”、“实质”及“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式 是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
本申请的一些实施例涉及电化学装置，其包括正极、负极、隔离膜和电解液。在一些实施例中，电化学装置是锂离子电池。
本申请的电化学装置具有能量密度高、倍率性能好且循环寿命长等优点。一方面，本申请的电化学装置中的正极包含一种镍基正极活性材料，该镍基正极活性材料具有较高的首次充电比容量，可以补充因生成固态电解质界面(SEI)造成的活性锂损失，从而提升电化学装置的能量密度。另一方面，本申请的电化学装置中的电解液包含氟代碳酸乙烯酯，可以在正极补锂的同时使负极形成更均匀且致密的SEI，减少活性锂的持续消耗。又一方面，本申请的电化学装置中的正极的电阻、压实密度和单面面密度满足一定的设计要求，显著地提升了电化学装置的循环寿命和倍率性能。
一、电化学装置
本申请提供了一种电化学装置，其包括正极、负极、隔离膜和电解液，其中所述正极包含正极活性材料层，所述正极活性材料层包括式(1)所示的正极活性材料：
Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s式(1)，
在式(1)中，0＜r≤1，0＜p＜1，0＜q＜1，0＜p+q＜0.5，0≤s＜0.2，M1和M2各自独立地为Co、Mn、Fe、Ti、Al、V、Cr、Nb、Zr、La或Y中的至少一种，M3是S、N、F、Cl或Br中的至少一种，其中所述正极的电阻为RΩ，所述正极的压实密度为P g/cm 3，所述正极的单面面密度为Q g/1540.25mm 2，并且所述正极满足式(2)：
3.5≤R·P/Q≤30式(2)，
其中所述电解液包含氟代碳酸乙烯酯。
正极活性材料Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s包含两个物相，即物相A和物相B。物相A(例如，镍钴锰酸锂(NCM))属于R-3m空间群，可作为高比容量的正极活性材料。物相B(例如，过嵌Li之后的NCM)属于F-3m1空间群，其比容量很高，在首次充电时可脱出大量的锂离子来补充活性锂，以弥补因形成SEI导致的活性锂损失，并在脱锂后转变成物相A，作为正极活性材料参与后续充放电循环。
在一些实施例中，物相A在17°至19°处出现(003)晶面的特征衍射峰A1，物相B在16°至18°处出现(001)晶面的特征衍射峰B1，所述特征衍射峰A1的强度I A与特征衍射峰B1的强度I B满足式(4)：
0≤I A/I B＜100   式(4)。
在一些实施例中，I A/I B为约0、约0.01、约0.05、约0.1、约0.13、约0.15、约0.2、约0.5、约1、约5、约10、约15、约20、约25、约30、约35、约40、约45、约50、约55、约60、约65、约70、约75、约80、约85、约90、约95、约99或可以为以上任意两数值组成的范围，例如约0.01至约0.2、约0.01至约10、约0.1至约50、0至约50或约0.1至约100。
正极活性材料Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s的比容量取决于Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s中r的大小，r越大，代表过嵌锂的程度越高，首次充电比容量就越大。在一些实施例中，正极活性材料Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s中的Ni含量超过50％。
在一些实施例中，正极活性材料中的s＝0、M1为Co、M2为Mn或Al中的至少一者，例如，Li 1.2Ni 0.8Co 0.1Mn 0.1O 2、Li 1.2Ni 0.6Co 0.2Mn 0.2O 2或Li 1.2Ni 0.8Co 0.08Mn 0.1Al 0.02O 2等。
在一些实施例中，正极活性材料中的M1为Co、M2为Mn且M3为F或S中的至少一者，例如Li 1.2Ni 0.8Co 0.1Mn 0.1O 1.95F 0.05或Li 1.2Ni 0.8Co 0.1Mn 0.1O 1.9S 0.05F 0.05。
在一些实施例中，正极包括正极集流体，正极集流体在自身厚度方向上包括相对的两个表面，正极活性材料层设置于正极集流体的至少一个表面上，正极活性材料层包括式(1)所示的正极活性材料。
在一些实施例中，基于正极活性材料层的总重量，正极活性材料的重量百分比为约80％至约98％。在一些实施例中，基于正极活性材料层的总重量，正极活性材料的重量百分比为约80％、约82％、约84％、约86％、约88％、约90％、约92％、约94％、约 96％、约98％或可以为以上任意两数值组成的范围，例如约80％至约85％、约80％至约90、约85％至约95％或约90％至约98％等。
正极的电阻(RΩ)是膜片电阻，可以通过直流两探针法来测得。正极的压实密度(P g/cm 3)可以通过公式P＝m/v计算得出，公式中m为正极活性材料层的重量，单位为g；v是正极活性材料层的体积，单位为cm 3。正极活性材料层的体积v可以为正极活性材料层的面积A r与正极活性材料层的厚度之积。正极的单面面密度(Q g/1540.25mm 2)可以通过公式Q＝1540.25m/A r计算得出，式中m是正极活性材料层的重量，单位为g；A r是正极活性材料层的面积，单位为mm 2。
在本申请中，正极的电阻、压实密度和单面面密度是设计和制作电化学装置的关键参数。正极的电阻过大，会恶化电化学装置的循环性能和倍率性能。压实密度过大或过小，都会使电化学装置的循环性能和倍率性能变差。正极的单面面密度过大，会导致电化学装置的循环寿命降低，并影响电解液的渗透，进而使得电化学装置的倍率性能下降，尤其会导致电化学装置在高倍率下的放电容量降低；而正极的单面面密度过小，意味着相同电池容量下，集流体和隔膜的长度增加，增大了电化学装置的欧姆内阻。发明人研究发现，在电化学装置的制作中对这些参数进行综合设计以使正极满足上述式(2)，可以有效地提高电化学装置的循环性能和倍率性能。
在一些实施例中，R·P/Q可以为约3.5、约3.7、约3.8、约5、约5.5、约6、约6.5、约7、约7.5、约8、约8.5、约9、约9.5、约10、约10.5、约11、约11.5、约12、约13、约14、约15、约18、约19、约20、约22、约25、约28、约29、约30或可以为以上任意两数值组成的范围，例如约3.5至约10、约3.7至约9、约5至约8、约5至约10、约5至约15、约8至约12、约10至约12、约10至约20、约10至约30、约15至约30或约20至约30。
在一些实施例中，正极进一步满足式(3)：
5.0≤R·P/Q≤12   式(3)，
例如，R·P/Q可以为约5、约5.5、约6、约6.5、约7、约7.5、约8、约8.5、约9、约9.5、约10、约10.5、约11、约11.5、约12或可以为以上任意两数值组成的范围，例如约5至约8、约5至约10、约8至约12或约10至约12。
在一些实施例中，正极的电阻小于或等于3Ω(即，R≤3)，以有利地改善电化学装置的循环性能和倍率性能。R可以为小于或等于3中的任意值或任意范围，例如，R 可以小于或等于2.8、小于或等于2.5、小于或等于2、小于或等于1.5、小于或等于1.4、小于或等于1.3、小于或等于1.2、小于或等于1、小于或等于0.8、小于或等于0.6、小于或等于0.5、小于或等于0.4、小于或等于0.3，或者R可以为约3、约2.8、约2.5、约2、约1.8、约1.5、约1.2、约1、约0.8、约0.6、约0.5、约0.3、约0.1等或可以为以上任意两数值组成的范围，例如约0.1至约1、约0.5至约1、约0.4至约1.5、约0.6至约1.5、约0.5至约1.5、约1至约2、约0.5至约3或约1.5至约3。在一些实施例中，正极的电阻小于或等于1.5Ω(即，R≤1.5)。
在一些实施例中，正极的压实密度大于2.8g/cm 3且小于或等于3.6g/cm 3，即，2.8＜P≤3.6。P可以为大于2.8且小于或等于3.6中的任意值或任意范围，例如，P可以大于2.8且小于或等于3.0、大于2.8且小于或等于3.5、大于或等于3.0且小于或等于3.3、大于或等于3.0且小于或等于3.6、大于或等于3.2且小于或等于3.6等，或者P可以为约2.85、约2.9、约3.0、约3.1、约3.2、约3.3、约3.4、约3.5、约3.6或可以为以上任意两数值组成的范围，例如约2.9至约3.3、约3.0至约3.5或约2.9至约3.6。正极的压实密度在上述范围内有利于正极中电子和离子的迁移，从而提高电化学装置的循环性能。
在一些实施例中，正极的单面面密度大于0.16g/1540.25mm 2且小于0.32g/1540.25mm 2(即，0.16＜Q＜0.32)，以保证在充放电容量的前提下提高电化学装置的循环性能和倍率性能。Q可以为大于0.16且小于0.32中的任意值或任意范围，例如，Q可以大于0.16且小于0.30、大于0.16且小于0.28、大于0.16且小于0.25、大于0.16且小于0.20、大于或等于0.20且小于0.32、大于或等于0.25且小于0.32、大于或等于0.30且小于0.32，或者Q可以为约0.17、约0.18、约0.19、约0.20、约0.21、约0.22、约0.23、约0.24、约0.25、约0.26、约0.27、约0.28、约0.29、约0.30、约0.31或可以为以上任意两数值组成的范围，例如约0.17至约0.31、约0.18至约0.31、约0.20至约0.31、约0.25至约0.30。
进一步地，本申请通过在电解液中添加氟代碳酸乙烯酯，使得负极形成了富含LiF成分的、均匀且致密的SEI膜，有效地抑制了活性锂的持续损失；同时，氟代碳酸乙烯酯在正极侧更耐高压氧化，从而进一步提升电化学装置的循环寿命。
在一些实施例中，基于电解液的总重量，氟代碳酸乙烯酯的重量百分比为大于0且小于或等于15％。在一些实施例中，基于电解液的总重量，氟代碳酸乙烯酯的重量百分比可以为大于0且小于或等于15％中的任意值或任意范围，例如，氟代碳酸乙烯酯的重量百分比可以为约0.1％、约0.5％、约1.0％、约2.0％、约3.0％、约4.0％、约5.0％、 约6.0％、约7.0％、约8.0％、约9.0％、约10.0％、约11.0％、约12.0％、约13.0％、约14.0％、约15.0％或可以为以上任意两数值组成的范围，例如约0.1％至约15.0％、约0.5％至约15.0％、约1％至约15.0％、约5％至约10.0％、约5％至约15.0％或约10％至约15.0％。
本申请的电化学装置通过包含高比容量的镍基正极活性材料和氟代碳酸乙烯酯并调整正极的电阻、压实密度和单面面密度，实现了高的能量密度、优良的倍率性能以及长的循环寿命的有机统一。
在一些实施例中，正极活性材料层还包括粘合剂。粘合剂提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与正极集流体的结合。
在一些实施例中，粘合剂包括丁苯橡胶(SBR)、水性丙烯酸树脂、羧甲基纤维素(CMC)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、乙烯-醋酸乙烯酯共聚物(EVA)或聚乙烯醇(PVA)中的至少一种，但不限于此，可以根据实际需求来选择粘合剂。
在一些实施例中，基于正极活性材料层的总重量，粘结剂的重量百分比小于或等于2.0％，以获得较低的正极膜片电阻。在一些实施例中，基于正极活性材料层的总重量，粘结剂的重量百分比为约2.0％、约1.8％、约1.5％、约1.2％、约1.0％、约0.8％、约0.5％、约0.3％、约0.1％或可以为以上任意两数值组成的范围，例如约0.1％至约2.0％、约0.5％至约2.0％、约0.1％至约1.0％或约1.0％至约2.0％。
在一些实施例中，正极活性材料层还包括导电剂，导电剂包括石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种，但不限于此，可以根据实际需求来选择导电剂。
在一些实施例中，基于正极活性材料层的总重量，导电剂的重量百分比大于或等于0.5％，以获得较低的正极膜片电阻。在一些实施例中，基于正极活性材料层的总重量，导电剂的重量百分比大于或等于0.5％、大于或等于1.0％或大于或等于1.5％等。
在一些实施例中，正极集流体可以采用金属箔材或多孔金属板，例如使用铝、铜、镍、钛或银等金属或它们的合金的箔材或多孔板，例如铝箔，但不限于此。
在一些实施例中，正极集流体的厚度为约5μm至约20μm，例如，约5μm、约6μm、约7μm、约8μm、约10μm、约12μm、约14μm、约16μm、约18μm、约20μm或可以为以上任意两数值组成的范围，例如约6μm至18μm或约8μm至约16μm。
在一些实施例中，正极活性材料层可以通过如下操作来制作：将正极活性材料和粘结剂(根据需要而使用的导电材料和增稠剂等)进行干式混合而制成片状，将得到的片压接于正极集流体，或者使这些材料溶解或分散于液体介质中而制成浆料状，涂布在正极集流体上并进行干燥。
在一些实施例中，正极可以通过本领域公知的制备方法制备。例如，正极可以通过如下方法获得：在溶剂中将正极活性材料、导电材料和粘合剂混合，以制备活性材料组合物，并将该活性材料组合物涂覆在正极集流体上。在一些实施例中，溶剂可以包括N-甲基吡咯烷酮(NMP)等，但不限于此。
在一些实施例中，负极可以是金属锂片，也可以是包括负极集流体及设置于负极集流体至少一个表面上的负极活性材料层。
在一些实施例中，负极活性材料层包括负极活性材料，并可选地包括导电剂、粘结剂和增稠剂。
在一些实施例中，负极活性材料可以包括天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的钛酸锂Li 4Ti 5O 12、Li-Al合金及金属锂中的一种或多种。
在一些实施例中，导电剂可以包括石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。
在一些实施例中，粘结剂可以是丁苯橡胶、聚偏二氟乙烯、聚四氟乙烯、聚乙烯醇缩丁醛、水性丙烯酸树脂、羧甲基纤维素或聚丙烯酸(PAA)中的一种或多种。
在一些实施例中，增稠剂可以是羧甲基纤维素。
本申请的电化学装置中的负极不限定于以上材料，本申请还可以使用可被用作锂离子电池负极活性材料、导电剂、粘结剂和增稠剂的其它材料。
负极集流体可以使用金属箔材或多孔金属板等材料，例如使用铜，镍，钛或铁等金属或它们的合金的箔材或多孔板，如铜箔。
负极可以按照本领域常规方法制备。通常将负极活性材料及可选的导电剂，粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮或去离子水，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压等工序得到负极极片。
本申请的电化学装置中的隔离膜没有特别的限制，可以选用任意公知的具有电化学 稳定性和化学稳定性的多孔结构隔离膜，例如玻璃纤维、无纺布、聚乙烯(PE)，聚丙烯(PP)及聚偏二氟乙烯中的一种或多种的单层或多层薄膜。
本申请的电化学装置中的电解液除了氟代碳酸乙烯酯，还包括有机溶剂、电解质锂盐和添加剂。本申请对有机溶剂和电解质锂盐的种类不做具体限制，可以根据实际需求进行选择。
在一些实施例中，有机溶剂可以为碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸丁烯酯(BC)、碳酸亚乙烯酯(VC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1，4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的至少一种。在一些实施例中，有机溶剂包括上述化合物中的至少两种。
在一些实施例中，电解质锂盐可以为六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或多种。
在一些实施例中，解液中还可选地包括其它添加剂，其它添加剂可以是任意可被用作锂离子电池的添加剂，在此不做具体限制，可以根据实际需求进行选择。在一些实施例中，添加剂可以是碳酸乙烯亚乙酯(VEC)、丁二腈(SN)、己二腈(AND)、1，3-丙烯磺酸内酯(PST)、磺酸酯环状季铵盐、三(三甲基硅烷)磷酸酯(TMSP)及三(三甲基硅烷)硼酸酯(TMSB)中的一种或多种。
本申请的电化学装置中的电解液可以按照本领域常规的方法制备。例如，将有机溶剂，电解质锂盐，氟代碳酸乙烯酯及其它可选的添加剂混合均匀，得到电解液，其中各物料的添加顺序并没有特别的限制。例如，将电解质锂盐，氟代碳酸乙烯酯及其它可选的添加剂加入到有机溶剂中混合均匀，得到电解液。其中可以是先将电解质锂盐加入有机溶剂中，然后再将氟代碳酸乙烯酯和其它可选的添加剂分别或同时加入有机溶剂中。
本申请的电化学装置可以按照本领域常规的方法制备。例如，将上述正极、隔离膜及负极按顺序堆叠好，使隔离膜处于正极与负极之间起到隔离的作用，得到电芯，也可 以是经卷绕后得到电芯；将电芯置于包装外壳中，注入电解液并封口，得到电化学装置。
二、电子装置
由本申请所述的电化学装置适用于各种领域的电子装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何用途。在一个实施例中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
三、实施例
以下，举出实施例和对比例对本申请进一步具体地进行说明，但只要不脱离其主旨，则本申请并不限定于这些实施例。
锂离子电池的制备
(1)正极的制备
将正极活性材料、粘结剂聚偏二氟乙烯及导电炭黑进行混合，其中正极活性材料、聚偏二氟乙烯及导电炭黑的重量比为97.6∶1.3∶1.1，加入溶剂NMP，在真空搅拌作用下搅拌至均匀，获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后转移至烘箱干燥，烘干温度为120℃，再经过冷压，分切，得到正极。
(2)负极的制备
将负极活性材料人造石墨、氧化亚硅、粘结剂聚丙烯酸及导电炭黑按照质量比85.9∶10∶2.8∶1.3进行混合，加入溶剂去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；之后转移至烘箱干燥，烘干温度为120℃，再经过冷压，分切，得到负极。
(3)电解液的制备
将碳酸乙烯酯、碳酸甲乙酯及碳酸二乙酯按照体积比为1∶1∶1混合均匀，得到有机溶剂。将1mol/L的LiPF 6溶解于上述有机溶剂中，再加入一定含量的氟代碳酸乙烯酯，混合均匀，得到电解液。
(4)隔离膜的制备
离膜采用厚度为14μm的聚丙烯薄膜(Celgard公司提供)。
(5)锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕得到裸电池；将裸电池置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的电池中，经过真空封装、静置、化成、整形等工序，即完成锂离子电池的制备。
按照上述制备方法制备实施例1至21以及对比例1至5的锂离子电池，各实施例和各对比例的正极活性材料、正极的电阻、正极的压实密度、正极的单面面密度以及电解液中的氟代碳酸乙烯酯相对于电解液总重量的重量百分比如下面的表1所示，并对制备好的锂离子电池进行下面测试。对比例5中的正极活性材料为LiNi 0.8Co 0.1Mn 0.1O 2，其余参数与实施例2完全相同，在下面的高温循环性能测试中绘制实施例2和对比例5的首次充电曲线。
表1
Figure PCTCN2022076462-appb-000001
Figure PCTCN2022076462-appb-000002
测试方法
(1)正极的电阻测试
采用日置BT3562型电阻测试仪测试正极的电阻，具体测试步骤包括：将正极夹持于内阻测试仪的两个导电端子之间，并施加压力固定，测试正极的电阻R，其中探针与正极极片的接触面积为49πmm 2，导电端子的直径为14mm，施加压力为15MPa～27MPa，采点时间的范围为5s～17s。
(2)高温循环性能测试
将制备好的锂离子电池放至45℃恒温箱中，将锂离子电池以1.5C倍率恒流充电至4.3V，再在4.3V下恒压充电至电流小于或等于0.05C，再以1C倍率恒流放电至3.0V，此为一个充放电循环，将锂离子电池按照上述方法进行充放电循环，并记录锂离子电池的首次循环的放电容量以及之后的每一次循环的放电容量，直至锂离子电池的放电容量衰减至首次循环的放电容量的80％，记录此时的充放电循环次数。
(3)倍率性能测试
在25℃下，将锂离子电池以0.2C倍率恒流充电至4.3V，再在4.3V下恒压充电至电流小于等于0.05C，再以0.2C倍率恒流放电至3.0V，记录0.2C倍率的放电容量。
在25℃下，将锂离子电池以0.2C倍率恒流充电至4.3V，再在4.3V下恒压充电至电流小于等于0.05C，再以2C倍率恒流放电至3.0V，记录2C倍率的放电容量。
锂离子电池的2C倍率放电容量保持率(％)＝2C倍率放电容量/0.2C倍率放电容量×100％。
(4)X射线衍射测试
采用X射线衍射测试仪(荷兰帕纳科，XPertPro MPD)，并设定测试条件：Cu K α辐射
Figure PCTCN2022076462-appb-000003
工作电流250mA，采用连续扫描，工作电压为40kV，扫描范围2θ为10°～70°，步长0.1°，扫描速度0.2秒/步，对实施例的样品粉末进行衍射测试来确认样品物相。
测试结果
图1为本申请实施例1中的正极活性材料Li 1.2Ni 0.8Co 0.1Mn 0.1O 2的X射线衍射(XRD)图。物相A在17°至19°处出现(003)晶面的特征衍射峰A1的强度I A与物相B在16°至18°处出现(001)晶面的特征衍射峰B1的强度I B的比值I A/I B＝7.2。
图2为实施例2以及对比例5的首次充电曲线图，从图2可以看出，本申请中的正极活性材料的首圈充电比容量高，可有效弥补因生成SEI所造成的活性锂损失，进而提高锂离子电池的能量密度。
表2是实施例1至21以及对比例1至5的锂离子电池的测试结果。
表2
  R·P/Q 高温循环次数 2C倍率放电容量保持率(％)
对比例1 63.88 266 96.5
对比例2 38.05 282 96.7
对比例3 0.7 231 94.7
对比例4 8.75 188 97.8
对比例5 8.75 302 98.0
实施例1 8.75 345 97.1
实施例2 8.75 392 97.5
实施例3 8.75 399 97.7
实施例4 8.75 421 97.6
实施例5 8.75 436 97.6
实施例6 8.75 482 98.1
实施例7 8.75 430 97.2
实施例8 3.74 381 97.0
实施例9 30 386 97.4
实施例10 8.75 379 97.9
实施例11 8.75 478 97.2
实施例12 29.0 336 96.6
实施例13 18.71 369 96.7
实施例14 6.75 353 96.5
实施例15 9.25 368 96.8
实施例16 13.13 371 97.0
实施例17 6.56 356 96.7
实施例18 8.75 324 98.0
实施例19 8.75 347 98.0
实施例20 8.75 368 97.9
实施例21 8.75 412 97.3
通过比较实施例2和对比例5可知，本申请的正极活性材料的首圈充电比容量高，可有效弥补因生成SEI所造成的锂损失，进而提升电池能量密度。
通过比较实施例1、2和7与对比例1至3可知，本申请通过控制正极电阻R、压实密度P和单面面密度Q满足3.5≤R·P/Q≤30，能够使锂离子电池具有良好的循环性能 和倍率性能。
通过比较实施例1、2、7、8和9与对比例1可知，本申请中的电解液中添加的氟代碳酸乙烯酯可以与正极补锂策略能发挥协同作用。在首次充电时，由于大量活性锂嵌入负极，导致负极的真实电位进一步降低，造成电解液中溶剂的持续还原，影响循环性能，在电解液中添加氟代碳酸乙烯酯，可以诱导生成更加致密和轻薄的SEI层，阻止了电解液的持续消耗，此外，氟代碳酸乙烯酯更耐高压氧化，更有利于提升高电压区间的循环寿命。控制电解液中的氟代碳酸乙烯酯小于或等于15％可以实现更好的高温循环性能。
整个说明书中对“一些实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例“，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (10)

  1. 一种电化学装置，其包括正极、负极、隔离膜和电解液，其中所述正极包含正极活性材料层，所述正极活性材料层包括式(1)所示的正极活性材料：
    Li 1+rNi 1-p-qM1 pM2 qO 2-sM3 s  式(1)，
    在式(1)中，0＜r≤1，0＜p＜1，0＜q＜1，0＜p+q＜0.5，0≤s＜0.2，M1和M2各自独立地为Co、Mn、Fe、Ti、Al、V、Cr、Nb、Zr、La或Y中的至少一种，M3是S、N、F、Cl或Br中的至少一种，
    其中所述正极的电阻为RΩ，所述正极的压实密度为P g/cm 3，所述正极的单面面密度为Q g/1540.25mm 2，并且所述正极满足式(2)：
    3.5≤R·P/Q≤30   式(2)，
    其中所述电解液包含氟代碳酸乙烯酯。
  2. 根据权利要求1所述的电化学装置，其中所述正极进一步满足式(3)：
    5.0≤R·P/Q≤12  式(3)。
  3. 根据权利要求1所述的电化学装置，其中R满足R≤3。
  4. 根据权利要求1所述的电化学装置，其中R满足R≤1.5。
  5. 根据权利要求1所述的电化学装置，其中P满足2.8＜P≤3.6。
  6. 根据权利要求1所述的电化学装置，其中Q满足0.16＜Q＜0.32。
  7. 根据权利要求1所述的电化学装置，其中基于所述电解液的总重量，氟代碳酸乙烯酯的重量百分比为大于0且小于或等于15％。
  8. 根据权利要求1所述的电化学装置，其中基于所述正极活性材料层的总重量，所述正极 活性材料的重量百分比为80％至98％。
  9. 根据权利要求1所述的电化学装置，其中所述正极活性材料包含物相A和物相B，所述物相A在17°至19°处出现(003)晶面的特征衍射峰A1，所述物相B在16°至18°处出现(001)晶面的特征衍射峰B1，所述特征衍射峰A1的强度I A与特征衍射峰B1的强度I B满足式(4)：0≤I A/I B＜100  式(4)。
  10. 一种电子装置，所述电子装置包含权利要求1至9中任一项所述的电化学装置。
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