KR100537604B1 - Electrolyte for a lithium polymer battery and a lithium polymer battery using the same - Google Patents

Abstract

Disclosed is an electrolyte for a lithium polymer battery and a lithium polymer battery using the same. Electrolyte solution for a lithium polymer battery is a mixed organic solvent comprising 10 to 50% by weight of fluorobenzene, 40 to 80% by weight of a carbonate-based material; And 1 to 10% by weight of stabilizer; characterized in that it comprises a. The carbonate-based material preferably includes at least one material selected from the group consisting of ethylene carbonate, dimethyl carbonate and diethyl carbonate, and the stabilizer includes at least one material selected from biphenyl, methoxythiophene and thiophene. It is desirable to. Fluorobenzene contained in the electrolyte improves the low temperature performance of the battery, and the stabilizer induces a polymerization reaction in the electrolyte consisting of a carbonate-based organic solvent to increase the resistance value of the electrolyte, thereby increasing the flow of current through the electrolyte. This prevents the battery from deteriorating due to the overcharging.

Description

Electrolyte for lithium polymer battery and lithium polymer battery using same {Electrolyte for a lithium polymer battery and a lithium polymer battery using the same}

The present invention relates to a lithium polymer battery electrolyte and a lithium polymer battery using the same, and more particularly to a lithium polymer battery electrolyte that can improve the safety of the lithium polymer battery.

As the necessity of a battery having a high energy density as a power source for portable electronic devices has increased, research on lithium polymer batteries has been actively conducted.

Lithium polymer batteries exhibit unique battery characteristics by complex electrochemical reactions such as positive / electrolyte and negative / electrolyte. Therefore, the electrolyte of a lithium polymer battery is the most important component in the electrochemical reaction occurring inside the battery, and it is obvious in the battery technology that it is an important factor that can influence the performance of the battery.

The negative electrode of a lithium polymer battery was initially manufactured using a lithium metal material, but in this case, since there is a risk of explosion of the battery due to battery short-circuit due to the formation of dentrite, in order to prevent this, in recent years, negative electrode manufacturing has been performed. Lithium metal materials, which have been conventionally used, have been replaced by carbon materials such as artificial graphite (MCF), natural graphite (graphite), and the like.

The positive electrode of a lithium polymer battery is made of a mixed metal oxide containing lithium, for example, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium manganese oxide and the like.

There are various types of electrolytes developed to date. The electrolytes used in early battery manufacturing techniques were simply enough to function as mediators to move lithium ions. Most of the electrolytes used in the early stages of battery development decompose some or all of the cells during charging / discharging. The decomposition phenomenon of electrolyte solution is a cause which causes the performance degradation of a battery.

Conventionally, an electrolyte solution including a carbonate-based material has been proposed to solve a problem of deterioration of battery performance due to electrolyte decomposition. However, since the carbonate-based material is an organic solvent having a strong ignition property, there is a problem that is vulnerable to external ignition factors. Therefore, the technology in which the mixed organic solvent containing a carbonate material and a phosphoric acid material is employ | adopted as electrolyte of a battery continuously developed. As a result, the battery using the mixed organic solvent electrolyte can suppress the electrolyte decomposition reaction in the battery relative to the battery prepared using the electrolyte consisting of a conventional carbonate-based material, thereby producing a more stable lithium polymer battery. I can do it.

However, as described above, the method of using a mixed organic solvent prepared by mixing a carbonate solvent and a phosphoric acid solvent as an electrolyte may be improved in safety compared to a conventional electrolyte prepared using only a carbonate solvent. During electrochemical charging / discharging inside a lithium polymer battery, the phosphoric acid component of the mixed organic solvent electrolyte is easily decomposed, thereby causing another problem of excessively increasing the irreversible capacity of the battery. If the irreversible capacity of the battery is excessively increased, several basic characteristics of the battery may be greatly degraded. The irreversible capacity of the battery is expressed as a percentage of the total charge amount, and the difference between the charge amount and the discharge amount is substantially caused by the problem that the effective capacity of the battery decreases as the irreversible capacity of the battery increases.

The present invention is to solve the above problems of the conventional electrolyte solvent, improve the low-temperature characteristics of the battery and improve the safety of the battery, and also the problem that the performance of the battery is degraded by decomposing the electrolyte during charge / discharge generated inside the battery It is an object of the present invention to provide an electrolyte with improved safety used in a lithium polymer battery.

In order to achieve the above technical problem to be solved by the present invention, an electrolyte solution for a lithium polymer battery includes a mixed organic solvent including 10 to 50 wt% of fluorobenzene and 40 to 80 wt% of a carbonate-based material; And 1 to 10% by weight of stabilizer; characterized in that it comprises a.

Lithium polymer battery for achieving the above technical problem to be solved by the present invention is a mixed organic solvent comprising 10 to 50% by weight of fluorobenzene, 40 to 80% by weight of a carbonate-based material; And 1 to 10% by weight of stabilizer; characterized in that it comprises an electrolyte solution comprising a. On the other hand, the stabilizer must be present even in a small amount in the electrolyte, but if the content exceeds 10%, the appropriate numerical limitation as described above is essential because the performance of the battery may be rather deteriorated.

In the lithium polymer battery electrolyte according to the present invention and a lithium polymer battery using the same, the carbonate-based material preferably comprises at least one material selected from the group consisting of ethylene carbonate, dimethyl carbonate and diethyl carbonate, and the stable The topical agent preferably comprises at least one material selected from biphenyl, methoxythiophene and thiophene.

Fluorobenzene in the electrolyte is a material used to improve the low temperature performance of the battery and to stabilize the battery life.

The stabilizer induces a polymerization reaction in a mixed organic solvent including the fluorobenzene and a carbonate-based material under a condition that the battery voltage is about 6 volts to increase the resistance of the electrolyte. Therefore, it is possible to solve the problem that the flow of the current passing through the electrolyte is disturbed and the battery characteristics generated during high rate overcharging are deteriorated. That is, the stabilizer such as thiophene, biphenyl, or the like will cause a polymerization reaction at 6 volts or more, and thus oligomers or polymers may be formed in the electrolyte to prevent the flow of current.

Hereinafter, the present invention will be described in more detail with reference to examples according to the present invention and comparative examples.

Example 1

A mixed organic solvent including carbonate based material and fluorobenzene, which are mixed solvents of ethylene carbonate and dimethyl carbonate, was prepared. In this case, the weight ratio of ethylene carbonate, dimethyl carbonate and fluorobenzene in the mixed organic solvent was set to 3: 4: 5. Meanwhile, 5% by weight of methoxythiophene was added to the mixed organic solvent as a stabilizer of the mixed organic solvent. As a result, a battery was manufactured using the prepared electrolyte, and the cathode of the battery was prepared using lithium nickel cobalt manganese oxide as an active material, and the anode of the battery was prepared using artificial graphite (MCF).

Various characteristics of the battery manufactured using the electrolyte prepared as described above were evaluated according to each evaluation method described in the following (1) to (4), and the results are shown in Table 1 below.

(1) Evaluation method for life characteristics of battery

Typically, the battery life characteristics of the battery was measured after performing 500 cycle charge and discharge at 1C. At this time, when the capacity of the battery is 70% or more of the initial capacity is considered to be excellent.

(2) Battery capacity evaluation method

After the battery was completely prepared, the initial discharge capacity and the irreversible capacity in one cycle were measured.

(3) Battery safety evaluation method

Overcharge, high rate and charge tests were performed using eight safety testers in the cell safety evaluation room. It is judged whether the pass or fail of the battery can be commercialized.

(4) Evaluation method of low temperature characteristics of battery

The capacity at the time of discharge was measured in the chamber maintained at minus 20 degreeC which is an extreme condition, and the discharge capacity of the battery in normal laboratory conditions was compared.

Example 2

An electrolyte solution was prepared by adding 5 wt% biphenyl as a stabilizer to the mixed organic solvent prepared in the same manner as in Example 1. As a result, various characteristics of the battery manufactured using the prepared electrolyte were evaluated according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

Example 3

A battery was prepared by adding 2.5% by weight of thiophene and 2.5% by weight of biphenyl as a stabilizer to the mixed organic solvent prepared in the same manner as in Example 1. As a result, various characteristics of the battery manufactured using the prepared electrolyte were evaluated according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

Comparative Example 1

A battery was prepared using a mixed organic solvent having a weight ratio of ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a 3: 4: 3 electrolyte solution as a lithium polymer battery. This is according to the conventional method of manufacturing a battery using an electrolyte solution in which the fluorobenzene and the stabilizer are not added to the mixed organic solvent, unlike Examples 1 to 3. As a result, various characteristics of the finished battery using the prepared electrolyte solution were evaluated according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

Comparative Example 2

A battery was manufactured using a mixed organic solvent having a weight ratio of ethylene carbonate, dimethyl carbonate, and fluorobenzene in a 3: 4: 3 solution as an electrolyte of a lithium polymer battery. This is in accordance with the conventional method for producing a battery using an electrolyte solution that does not add a separate stabilizer to the mixed organic solvent, unlike Examples 1 to 3. As a result, in order to evaluate various characteristics of the finished battery using the prepared electrolyte solution, the evaluation was performed according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

Comparative Example 3

To the mixed organic solvent prepared in the same manner as in Example 1, 0.5 wt% of methoxythiophene was added as a stabilizer of the mixed organic solvent to prepare an electrolyte solution. As a result, various characteristics of the battery manufactured using the prepared electrolyte were evaluated according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

Comparative Example 4

To the mixed organic solvent prepared in the same manner as in Example 1, 12% by weight of methoxythiophene was added as a stabilizer of the mixed organic solvent to prepare an electrolyte solution. As a result, various characteristics of the battery manufactured using the prepared electrolyte were evaluated according to the evaluation method described in Example 1, and the results are shown in Table 1 below.

division life span(%) Volume safety Low temperature characteristics (%) (at -20 ° C) Initial discharge capacity Irreversible capacity (%) Overcharge (1C) High rate and charge Example 1 85 2150 8 **** **** 70 Example 2 84 2090 12 **** **** 65 Example 3 89 2120 14 **** **** 73 Comparative Example 1 90 2100 9 ** ** 83 Comparative Example 2 92 2130 11 *** ** 80 Comparative Example 3 88 2140 13 *** ** 65 Comparative Example 4 85 2080 12 ** *** 60

According to Table 1, in the life characteristics, capacity and low temperature characteristics of the battery it can be seen that the embodiment according to the present invention has the performance of the product without significant difference from the comparative example. On the other hand, in terms of safety of the battery focusing on the present invention was expressed by the number of stars (*) as a criterion for determining the pass or fail. As a result of the battery's safety test, less than two asterisks (*) on the safety of the battery are defective products, and in the case of two or more asterisks (*), the product has been passed as a product. On the other hand, even if passed, there is a difference in the safety of the product, so if it is rated, two stars (*) are good, three are very good, and four or more can be classified as the best. In addition, according to Table 1, it can be seen that in the case of Examples 1 to 3 all have improved safety compared to the conventional comparative example.

The present invention described above with reference to the embodiments should not be construed as being limited to the above embodiments, but only those disclosed for the purpose of easy understanding of the present invention will be apparent to those skilled in the art. . Accordingly, the scope of the present invention also includes various modifications of the contents mentioned in the above embodiments.

When manufacturing a lithium polymer battery using the lithium polymer battery electrolyte according to the present invention it is possible to ensure a good low-temperature characteristics of the battery, and by the decomposition of the electrolyte components in the battery safety and safety of the battery during charging and discharging of the battery The problem of deterioration of battery characteristics caused by increasing irreversible capacity can be solved. That is, when a predetermined stabilizer is added to a mixed organic solvent containing fluorobenzene and a carbonate organic solvent, which is a low temperature characteristic improving agent as in the present invention, the added stabilizer induces a polymerization reaction in the mixed organic solvent. The safety of the battery can be significantly improved.

Claims (6)

A mixed organic solvent comprising 10 to 50 wt% of fluorobenzene and 40 to 80 wt% of a carbonate-based material; And 1 to 10% by weight of a stabilizer; the electrolyte solution of a lithium polymer battery comprising a. The method of claim 1, The carbonate-based material is a lithium polymer battery electrolyte, characterized in that it comprises at least one material selected from the group consisting of ethylene carbonate, dimethyl carbonate and diethyl carbonate. The method of claim 1, The stabilizer is a lithium polymer battery electrolyte, characterized in that it comprises at least one material selected from biphenyl, methoxythiophene and thiophene. In a lithium polymer battery prepared by including an electrolyte solution, The electrolyte is a mixed organic solvent comprising 10 to 50% by weight of fluorobenzene, 40 to 80% by weight of a carbonate-based material; And 1 to 10% by weight of a stabilizer; lithium polymer battery comprising a. The method of claim 4, wherein The carbonate-based material is a lithium polymer battery, characterized in that it comprises at least one material selected from the group consisting of ethylene carbonate, dimethyl carbonate and diethyl carbonate. The method of claim 4, wherein The stabilizer is a lithium polymer battery, characterized in that it comprises at least one material selected from biphenyl, methoxythiophene and thiophene.