JP2006210358A - Lithium secondary cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary cell excellent in cycle property and safety such as the prevention of overcharging. <P>SOLUTION: The lithium secondary cell includes a positive electrode composed of a composite metal oxide containing cobalt or nickel, and lithium, and a negative electrode composed of metallic lithium, a lithium alloy or a material capable of occluding and releasing lithium. A nonaqueous solvent in a nonaqueous electrolyte of the lithium secondary cell is prepared to contain a chain carbonate and not less than two kinds of cyclic carbonates. The nonaqueous electrolyte is prepared to contain a total content to the electrolyte 0.1-10 mass% cyclohexylbenzene and a tert-alkylbenzene derivative. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium secondary battery excellent in battery characteristics such as safety such as prevention of overcharge, cycle characteristics, electric capacity, and storage characteristics.

In recent years, lithium secondary batteries have been widely used as driving power sources for small electronic devices and the like. In addition, there is great expectation as a power source for automobiles as well as portable electronic / communication devices such as small video cameras, mobile phones, and notebook computers. This lithium secondary battery is mainly composed of a positive electrode, a non-aqueous electrolyte and a negative electrode, and in particular, a lithium secondary battery having a lithium composite oxide such as LiCoO ₂ as a positive electrode and a carbon material or lithium metal as a negative electrode. Are preferably used. And carbonates, such as ethylene carbonate (EC) and propylene carbonate (PC), are preferably used as the non-aqueous solvent for the electrolyte solution for lithium secondary batteries.

  In such a lithium secondary battery, excessive lithium is released from the positive electrode at the time of overcharge exceeding the normal working voltage, and at the same time, excessive lithium is deposited at the negative electrode, resulting in dendrite. Therefore, both the positive and negative electrodes are chemically unstable. When both the positive and negative electrodes become chemically unstable, they eventually decompose by acting with carbonates in the non-aqueous electrolyte, causing a rapid exothermic reaction. This causes a problem that the battery generates heat abnormally and the safety of the battery is impaired. Such a situation becomes more important as the energy density of the lithium secondary battery increases.

  In order to solve such a problem, for example, Patent Document 1 proposes a technique that can ensure safety against overcharge by adding a small amount of an aromatic compound as an additive in an electrolytic solution. It was done. In this Patent Document 1, an anisole derivative having a π electron orbital having a molecular weight of 500 or less and having a reversible oxidation-reduction potential at a potential nobler than the positive electrode potential at the time of full charge is used. Yes. Such anisole derivatives ensure the safety of the battery against overcharging by redox shuttle in the battery.

  Patent Document 2 uses a carbon material for the negative electrode, and uses about 1 to 4% of biphenyl, 3-R-thiophene, 3-chlorothiophene, and furan as an additive for the electrolytic solution. A method has been proposed in which biphenyl or the like is polymerized at a voltage exceeding 1, thereby increasing the internal resistance of the battery and ensuring the safety of the battery against overcharging. In Patent Document 3, similarly, biphenyl, 3-R-thiophene, 3-chlorothiophene, furan is used to generate gas by polymerization of biphenyl or the like at a voltage exceeding the maximum operating voltage of the battery, There has been proposed a method for ensuring the safety of a battery against overcharging by causing an internal short circuit by operating an internal electrical disconnecting device. In Patent Document 4, similarly, biphenyl, 3-R-thiophene, 3-chlorothiophene, and furan are used to polymerize a conductive polymer by polymerizing biphenyl at a voltage exceeding the maximum operating voltage of the battery. There has been proposed a method for ensuring the safety of a battery against overcharging by causing an internal short circuit.

However, in Patent Document 5, in a battery to which biphenyl or the like is added, the cycle is repeated until the upper limit of the voltage exceeds 4.1 V, or in a charge / discharge state in which the battery is exposed for a long time at a high temperature of 40 ° C. or higher. It is described that there is a problem that the characteristics tend to be deteriorated, and the tendency becomes remarkable as the addition amount increases. Therefore, an electrolytic solution to which 2,2-diphenylpropane or the like is added has been proposed, and 2,2-diphenylpropane or the like is polymerized at a voltage exceeding the maximum operating voltage of the battery, thereby generating a gas and an internal electric cutting device. There have been proposed methods for ensuring the safety of a battery against overcharging by causing an internal short circuit by operating or generating a conductive polymer.
JP-A-7-302614 JP-A-9-106835 JP-A-9-171840 JP-A-10-32258 Japanese Patent Laid-Open No. 11-162512

  However, the anisole derivative proposed in Patent Document 1 has a problem of adversely affecting cycle characteristics and storage characteristics while effectively acting on overcharge by the redox shuttle. The proposed anisole derivative, when used at a high temperature of 40 ° C. or higher or at a normal operating voltage, gradually decomposes with charge / discharge when exposed to a slightly high voltage, and the original battery characteristics There is a problem that decreases. Therefore, since the anisole derivative gradually decomposes and decreases with normal charge and discharge, if an overcharge test is performed after 300 cycles, safety may not be sufficiently secured.

  Similarly, biphenyl, 3-R-thiophene, 3-chlorothiophene, and furan proposed in Patent Document 2, Patent Document 3, and Patent Document 4 work effectively against overcharge, As pointed out in Patent Document 5, the cycle characteristics and the storage characteristics are adversely affected, resulting in a problem that it becomes conspicuous with the amount of biphenyl added. This is because, since biphenyl and the like are oxidatively decomposed at a potential of 4.5 V or lower, even when used at a high temperature of 40 ° C. or higher or a normal operating voltage, Since biphenyl and the like are decomposed and reduced, the cycle life is reduced. Furthermore, since biphenyl and the like gradually decompose and decrease with charge and discharge, if an overcharge test is performed after 300 cycles, safety may not be sufficiently secured.

  Furthermore, although the battery added with 2,2-diphenylpropane proposed in Patent Document 5 is not as safe as overcharged as the battery added with biphenyl, it is safer than overcharged batteries. is good. In addition, it is described that the battery added with 2,2-diphenylpropane can have better cycle characteristics than the battery added with biphenyl, but the cycle characteristics are worse than the battery not added with anything. Therefore, it is stated that it is acceptable to sacrifice a part of safety in order to obtain better cycle characteristics than a battery to which biphenyl is added. For this reason, the present situation is that battery characteristics such as safety such as overcharge prevention and cycle characteristics, electric capacity, and storage characteristics are not always satisfactory.

  The present invention solves the above-mentioned problems relating to the electrolyte for a lithium secondary battery, and provides a lithium secondary battery having excellent battery characteristics such as safety such as overcharge prevention, cycle characteristics, electric capacity, and storage characteristics. The purpose is to provide.

  In the present invention, an electrolyte is dissolved in a positive electrode made of a composite metal oxide containing cobalt or nickel and lithium, a negative electrode made of lithium metal, a lithium alloy or a material capable of occluding and releasing lithium, and a non-aqueous solvent. A lithium secondary battery comprising a non-aqueous electrolyte, wherein the non-aqueous solvent includes a chain carbonate and two or more cyclic carbonates, and the non-aqueous electrolyte has a total content with respect to the electrolyte The lithium secondary battery includes 0.1 to 10% by mass of cyclohexylbenzene and a tert-alkylbenzene derivative.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium secondary battery excellent also in battery characteristics, such as safety, such as battery overcharge prevention, cycling characteristics, an electrical capacity, and a storage characteristic, can be provided.

  Examples of the tert-alkylbenzene derivative contained in the electrolytic solution of the present invention include the following compounds. In addition, the oxidation potential with respect to lithium measured by the method described in the examples described later is shown in parentheses.

  tert-butylbenzene (4.9V), 1-fluoro-4-tert-butylbenzene (4.9V), 1-chloro-4-tert-butylbenzene (4.9V), 1-bromo-4-tert- Butylbenzene (4.9V), 1-iodo-4-tert-butylbenzene (4.9V), 5-tert-butyl-m-xylene (4.6V), 4-tert-butyltoluene (4.7V) 3,5-di-tert-butyltoluene (4.8V), 1,3-di-tert-butylbenzene (4.9V), 1,4-di-tert-butylbenzene (4.9V), 1 , 3,5-tri-tert-butylbenzene (5.0V) and tert-butylbenzene derivatives, and tert-pentylbenzene (4.8V), 1-methyl-4-tert-pentyl Benzene, (4.7V), 5-tert-pentyl-m-xylene (4.6V), 1-ethyl-1- (methylpropyl) benzene (4.8V), (1,1-diethylpropyl) benzene ( 4.8V), 1,3-di-tert-pentylbenzene (4.7V), 1,4-di-tert-pentylbenzene (4.7V) and the like.

  That is, the tert-alkylbenzene derivative and cyclohexylbenzene (4.7 V) as described above are contained in the electrolyte solution of the lithium secondary battery of the present invention. Then, by replacing a part of the tert-alkylbenzene derivative such as tert-butylbenzene having a oxidation potential of 4.8 to 5.0 V with a low oxidation potential of 4.7 V, the overcharge prevention effect is improved. be able to. For example, when a part of the tert-alkylbenzene derivative is replaced with cyclohexylbenzene, the content of the tert-alkylbenzene derivative (particularly the tert-butylbenzene derivative) is preferably 4 times or less the weight of cyclohexylbenzene, more preferably Is preferably 0.3 to 3 times, particularly 0.5 to 2.5 times. As described above, the effect of preventing overcharge can be enhanced by using tert-alkylbenzene derivative, which is at least two kinds of organic compounds having different oxidation potentials, and cyclohexylbenzene in combination.

  If the total content of the tert-alkylbenzene derivative and cyclohexylbenzene in the electrolyte solution of the lithium secondary battery of the present invention is excessively large, the conductivity of the electrolyte solution may change, and the battery performance may be deteriorated. If the amount is too small, a sufficient overcharge effect cannot be obtained. Therefore, the range of 0.1 to 10% by weight, particularly 1 to 5% by weight, based on the weight of the electrolytic solution is preferable.

  Examples of the non-aqueous solvent used in the electrolyte of the lithium secondary battery of the present invention include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC). Lactones such as γ-butyrolactone, chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC), tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1, Ethers such as 2-dimethoxyethane, 1,2-diethoxyethane and 1,2-dibutoxyethane, nitriles such as acetonitrile, esters such as methyl propionate, methyl pivalate, octyl pivalate, dimethylformamide Include amides such as is.

  These nonaqueous solvents may be used alone or in combination of two or more. The combination of the non-aqueous solvent is not particularly limited. For example, there are various combinations such as a combination of cyclic carbonates and chain carbonates, a combination of cyclic carbonates and lactones, a combination of three types of cyclic carbonates and chain carbonates, and the like. The combination of is mentioned.

Examples of the electrolyte used in the electrolyte solution of the lithium secondary battery of the present invention include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC. (SO ₂ CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso -C ₃ F _7), and the like. These electrolytes may be used alone or in combination of two or more. These electrolytes are used by being dissolved in the non-aqueous solvent usually at a concentration of 0.1 to 3M, preferably 0.5 to 1.5M.

  The electrolyte solution of the lithium secondary battery of the present invention can be obtained, for example, by mixing the non-aqueous solvent, dissolving the electrolyte therein, and dissolving the tert-alkylbenzene derivative and cyclohexylbenzene therein.

  In the lithium secondary battery of the present invention, constituent members other than the electrolytic solution are not particularly limited, and various conventionally used constituent members can be used.

For example, a composite metal oxide with lithium containing cobalt or nickel is used as the positive electrode active material. Examples of such composite metal oxides include LiCoO ₂ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1). Further, LiCoO ₂ and LiMn ₂ O ₄ , LiCoO ₂ and LiNiO ₂ , LiMn ₂ O ₄ and LiNiO ₂ may be appropriately mixed and used.

  The positive electrode is composed of a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), a copolymer of acrylonitrile and butadiene. After kneading with a binder such as a polymer (NBR) or carboxymethylcellulose (CMC) to form a positive electrode mixture, the positive electrode material is rolled into an aluminum or stainless steel foil or lath plate as a current collector, It is produced by heat treatment under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.

As the negative electrode (negative electrode active material), lithium metal, lithium alloy, or carbon material capable of inserting and extracting lithium (pyrolytic carbons, cokes, graphite (artificial graphite, natural graphite, etc.), organic polymer compound combustion Body, carbon fiber], or composite tin oxide. In particular, it is preferable to use a carbon material having a graphite-type crystal structure in which the lattice spacing ( ₀₀₂ ) has an interplanar spacing (d ₀₀₂ ) of 0.335 to 0.340 nm (nanometer). Powder materials such as carbon materials are ethylene propylene diene terpolymer (EPDM), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), and a copolymer of acrylonitrile and butadiene. Kneaded with a binder such as a polymer (NBR) or carboxymethylcellulose (CMC) and used as a negative electrode mixture.

  The structure of the lithium secondary battery is not particularly limited, and has a single-layer or multiple-layer positive electrode, negative electrode, and separator having a separator, a coin-type battery or a polymer battery, and a roll-shaped positive electrode, negative electrode, and roll-shaped separator. Examples include a cylindrical battery and a square battery. A known polyolefin microporous film, woven fabric, non-woven fabric or the like is used as the separator.

  The lithium secondary battery in the present invention has excellent cycle characteristics over a long period of time even when the maximum operating voltage is greater than 4.2V, and particularly excellent when the maximum operating voltage is 4.3V. Cycle characteristics. The cut-off voltage can be set to 2.0V or higher, and further can be set to 2.5V or higher. Although it does not specifically limit about an electric current value, Usually, it is used by 0.1-3C constant current discharge. Moreover, although the lithium secondary battery in this invention can be charged / discharged in a wide range with -40-100 degreeC, Preferably it is 0-80 degreeC.

Next, an Example and a comparative example are given and this invention is demonstrated concretely.
[Comparative Example 1]
[Measurement of oxidation potential]
An electrolyte solution was prepared by dissolving LiPF ₆ in a non-aqueous solvent of propylene carbonate to a concentration of 1 M, and then tert-butylbenzene was added to the electrolyte solution so as to be 2% by weight. The oxidation potential was measured at room temperature (20 ° C.) using an ALS electrochemical analyzer (model 608A). A metal lithium foil was used for the reference electrode, and a platinum rod electrode (diameter 1 mm) was used for the working electrode. Sweep from + 3V to + 6V at a rate of 10 mV per second. The value of the potential when a current change of 0.1 mA was observed was defined as the oxidation potential. However, the second decimal place is rounded off. As a result, the oxidation potential of tert-butylbenzene was 4.9V.

(Preparation of electrolyte)
After preparing a non-aqueous solvent of EC / PC / DEC (volume ratio) = 30/5/65, LiPF ₆ was dissolved in this to a concentration of 1M to prepare an electrolyte, and further tert-butylbenzene Was added so that it might become 2 weight% with respect to electrolyte solution.

[Production of lithium secondary battery and measurement of battery characteristics]
90% by weight of LiCoO ₂ (positive electrode active material), 5% by weight of acetylene black (conductive agent), and 5% by weight of polyvinylidene fluoride (binder) are mixed, and this is mixed with 1-methyl-2-pyrrolidone. Was added to form a slurry and coated on an aluminum foil. Then, this was dried and pressure-molded to prepare a positive electrode. 95% by weight of artificial graphite (negative electrode active material) and 5% by weight of polyvinylidene fluoride (binder) are mixed, and 1-methyl-2-pyrrolidone is added to this to form a slurry on a copper foil. Applied. Then, this was dried and pressure-molded to prepare a negative electrode. And using the separator of a polypropylene microporous film, said electrolyte solution was inject | poured and the cylindrical battery (diameter 18mm, height 65mm) of 18650 size was produced. The battery was provided with a pressure release port and an internal current interrupt device.

In order to perform a cycle test using this 18650 battery, after charging to 4.2 V at a constant current of 1.45 A (1 C) at a high temperature (45 ° C.), a final voltage of 4.2 V was obtained under the constant voltage. Charged for hours. Next, the battery was discharged to a final voltage of 2.5 V under a constant current of 1.45 A (1 C), and charging and discharging were repeated. The initial discharge capacity was equivalent to that in the case where 1M LiPF ₆ + EC / PC / DEC (capacity ratio) = 30/5/65 was used as the electrolyte (Comparative Example 1). When the battery characteristics after 300 cycles were measured, the discharge capacity retention rate when the initial discharge capacity was 100% was 85.5%. Moreover, the high temperature storage characteristics were also good. Furthermore, an overcharge test was performed by continuously charging the battery at a constant current of 2.9 A (2 C) from a fully charged state at room temperature (20 ° C.) using an 18650 battery in which the cycle test was repeated 300 times. At this time, the current interruption time was 25 minutes, and the maximum surface temperature of the battery after the current interruption was 68 ° C. Table 1 shows material conditions and battery characteristics of the 18650 size cylindrical battery.

[Example 1]
Oxidation was performed in the same manner as in Comparative Example 1 except that tert-butylbenzene and cyclohexylbenzene (oxidation potential: 4.7 V) were used in an amount of 1% by weight with respect to the electrolyte instead of 2% by weight of tert-butylbenzene. The potential was measured. The results are shown in Table 1. Table 1 shows the material conditions of the 18650 size cylindrical battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption. It can be seen that the temperature after current interruption is lower than that of Comparative Example 1 and the current interruption time is shorter, and the effect of preventing overcharge is further superior to that of Comparative Example 1.

[Comparative Example 2]
The oxidation potential was measured in the same manner as in Comparative Example 1 except that no tert-butylbenzene was added. The results are shown in Table 1. Table 1 shows the material conditions of the 18650 size cylindrical battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Table 1
────────────────────────────────────
Additive compound (wt%) Current interruption Battery discharge capacity
Time Maximum temperature Maintenance rate ────────────────────────────────────
Comparative Example 1 t-Butylbenzene (2) 25 minutes 68 ° C. 85.5%
────────────────────────────────────
Example 1 t-Butylbenzene (1) 18 minutes 64 ° C. 85.3%
Cyclohexylbenzene (1)
────────────────────────────────────
Comparative Example 2 None 31 minutes Thermal runaway 82.8%
────────────────────────────────────
Positive electrode: LiCoO ₂
Negative electrode: Artificial graphite Electrolyte composition (capacity ratio): 1M LiPF ₆
EC / PC / DEC (30/5/65)

[Comparative Example 3]
As the positive electrode active material, LiNi _0.8 Co _0.2 O ₂ was used instead of LiCoO _2, and a non-aqueous solvent of EC / PC / VC / DEC (capacity ratio) = 30/5/2/63 was prepared. An 18650 size cylinder was prepared in the same manner as in Comparative Example 1 except that LiPF ₆ was dissolved to a concentration of 1M to prepare an electrolytic solution, and tert-butylbenzene was further used in an amount of 3% by weight based on the electrolytic solution. Type batteries were prepared and the battery performance was measured. Table 2 shows the material conditions and battery characteristics of the 18650 size cylindrical battery.

[Example 2]
As the positive electrode active material, LiNi _0.8 Co _0.2 O ₂ was used instead of LiCoO _2, and a non-aqueous solvent of EC / PC / VC / DEC (capacity ratio) = 30/5/2/63 was prepared. In addition, LiPF ₆ was dissolved to a concentration of 1M to prepare an electrolytic solution, and then 2% by weight of tert-butylbenzene and 1% by weight of cyclohexylbenzene were used for the electrolytic solution. Produced a 18650 size cylindrical battery in the same manner as in Comparative Example 1, and measured the battery performance. Table 2 shows the material conditions and battery characteristics of the 18650 size cylindrical battery.

[Comparative Example 4]
A 18650-size cylindrical battery was prepared and the battery performance was measured in the same manner as in Comparative Example 2 except that LiNi _0.8 Co _0.2 O ₂ was used instead of LiCoO ₂ as the positive electrode active material. Table 2 shows the material conditions and battery characteristics of the 18650 size cylindrical battery.

Table 2
────────────────────────────────────
Additive compound (wt%) Current interruption Battery discharge capacity
Time Maximum temperature Maintenance rate ────────────────────────────────────
Comparative Example 3 t-Butylbenzene (3) 24 minutes 67 ° C. 84.7%
────────────────────────────────────
Example 2 t-Butylbenzene (2) 19 minutes 65 ° C. 84.3%
Cyclohexylbenzene (1)
────────────────────────────────────
Comparative Example 4 None 31 minutes Thermal runaway 80.4%
────────────────────────────────────
Positive electrode: LiNi _0.8 Co _0.2 O ₂
Negative electrode: Artificial graphite Electrolyte composition (capacity ratio): 1M LiPF ₆
EC / PC / VC / DEC (30/5/2/63)
(However, in Comparative Example 4, EC / PC / DEC (30/5/65))

[Comparative Example 5]
A 18650 size cylindrical battery was prepared in the same manner as in Comparative Example 1 except that tert-pentylbenzene (oxidation potential: 4.8 V) was used in an amount of 2% by weight with respect to the electrolyte instead of tert-butylbenzene. Performance was measured. Table 3 shows material conditions and battery characteristics of a 18650 size cylindrical battery.

[Example 3]
18650 size cylindrical battery as in Comparative Example 1 except that tert-pentylbenzene and cyclohexylbenzene were used in an amount of 2% by weight and 1% by weight, respectively, instead of 2% by weight of tert-butylbenzene. The battery performance was measured. Table 3 shows material conditions and battery characteristics of a 18650 size cylindrical battery.

[Example 4]
Comparative Example 1 except that tert-butylbenzene, tert-pentylbenzene and cyclohexylbenzene were used in an amount of 2% by weight, 2% by weight and 1% by weight, respectively, in place of 2% by weight of tert-butylbenzene. Similarly, a 18650 size cylindrical battery was produced, and the battery performance was measured. Table 3 shows material conditions and battery characteristics of a 18650 size cylindrical battery.

Table 3
────────────────────────────────────
Additive compound (wt%) Current interruption Battery discharge capacity
Time Maximum temperature Maintenance rate ────────────────────────────────────
Comparative Example 5 t-pentylbenzene (2) 22 minutes 66 ° C. 85.3%
────────────────────────────────────
Example 3 t-pentylbenzene (2) 17 minutes 63 ° C. 84.7%
Cyclohexylbenzene (1)
────────────────────────────────────
Example 4 t-Butylbenzene (2) 17 minutes 63 ° C. 84.9%
t-pentylbenzene (2)
Cyclohexylbenzene (1)
────────────────────────────────────
Positive electrode: LiCoO ₂
Negative electrode: Artificial graphite Electrolyte composition (capacity ratio): 1M LiPF ₆
EC / PC / DEC (30/5/65)

  In the above examples, sufficient cobalt or nickel was deposited on the negative electrode in all overcharges.

  In addition, this invention is not limited to the Example described, The various combination which can be easily guessed from the meaning of invention is possible. In particular, the combination of solvents in the above examples is not limited. Furthermore, although the said Example is related with a cylindrical battery of 18650 size, this invention is applied also to a square-type, an aluminum laminate type, and a coin-type battery.

Claims (10)

  A positive electrode made of a composite metal oxide containing cobalt or nickel and lithium, a negative electrode made of lithium metal, a lithium alloy or a material capable of occluding and releasing lithium, and a non-aqueous electrolyte in which an electrolyte is dissolved in a non-aqueous solvent The non-aqueous solvent includes a chain carbonate and two or more types of cyclic carbonate, and the non-aqueous electrolyte has a total content of 0.1 to 0.1 with respect to the electrolyte. A lithium secondary battery comprising 10% by mass of cyclohexylbenzene and a tert-alkylbenzene derivative.   The lithium secondary battery according to claim 1, wherein the cyclic carbonate contains two or more cyclic carbonates selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.   The lithium secondary battery according to claim 1 or 2, wherein the chain carbonate is selected from the group consisting of dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.   The lithium secondary battery according to claim 1 or 2, wherein the cyclic carbonate contains vinylene carbonate.   The lithium secondary battery according to any one of claims 1 to 4, wherein the negative electrode contains a carbon material as a negative electrode active material. 6. The lithium secondary battery according to claim 5, wherein the carbon material is a carbon material having a graphite type crystal structure with a lattice spacing ( ₀₀₂ ) spacing (d ₀₀₂ ) of 0.335 to 0.340 nm.   The lithium secondary battery according to any one of claims 1 to 6, wherein the tert-alkylbenzene derivative is a tert-butylbenzene derivative or a tert-pentylbenzene derivative.   The lithium secondary battery according to claim 1, wherein the tert-alkylbenzene derivative is tert-butylbenzene, 1-bromo-4-tert-butylbenzene, or tert-pentylbenzene.   The lithium secondary battery according to any one of claims 1 to 8, wherein the tert-alkylbenzene derivative is tert-pentylbenzene.   The lithium secondary battery according to any one of claims 1 to 9, wherein the content of the tert-alkylbenzene derivative is in the range of 0.3 to 4 times the content of cyclohexylbenzene.