JP2010192165A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with excellent charge storage characteristics and low-temperature cycle characteristics. <P>SOLUTION: In the nonaqueous electrolyte secondary battery, a nonaqueous electrolyte contains 0.005-1.0 mass% of a chelate compound and 0.2 mass% or more of at least one kind of compound selected from the group consisting of a cyclic ether compound, a sultone compound, cyclohexylbenzene, tert-alkylbenzene, a nitrile compound, and 4-fluoro-1,3-dioxolan-2-on. The chelate compound has a structure represented by formula: M-[O-CR2=C(COR1)]<SB>n</SB>(wherein M is any one metal atom selected from Al, Zr and Co; R1 and R2 are each 18C or lower alkyl or alkoxy group, and may be same or different while the alkyl or alkoxy group may have a straight chain structure or a branched structure; and n is a natural number from 1 to 4). Examples of the chelate compound include aluminum ethylacetoacetate diisopropylate or the like. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in a non-aqueous electrolyte secondary battery.

  In recent years, mobile information terminals such as mobile phones and notebook personal computers have been rapidly advanced in function, size and weight. As a driving power source for these mobile information terminals, non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries having high energy density and high capacity are widely used.

  However, when stored in a charged state, the lithium ion secondary battery has a problem that the positive electrode and the electrolytic solution react, and the electrolytic solution is oxidized and decomposed to generate gas.

  In order to solve this problem, various additives have been added to the non-aqueous electrolyte. However, the addition of the additive has a problem that the low-temperature cycle characteristics are deteriorated.

  The following patent documents 1-9 are mentioned as a technique regarding a nonaqueous electrolyte battery.

JP 2000-294277 JP JP 2006-172726 A Special table 2007-510270 JP 2003-86247 A Japanese Patent Laid-Open No. 2003-308875 JP 2004-179146 A JP 2004-265680 A JP 2007-149535 A Japanese Patent Laid-Open No. 2008-186792

  Patent Document 1 is a technique in which an aluminum tris (2,4-pentanedionate) derivative is contained in a nonaqueous electrolyte. According to this technique, it is said that a battery excellent in battery life, low-temperature characteristics and the like can be obtained.

  Patent Document 2 is a technique using a non-aqueous electrolyte containing a compound having a β-diketone partial structure and at least one metal complex selected from iron, nickel, copper, cobalt and zinc of β-diketone. According to this technique, a battery capable of suppressing the generation of dendrites is obtained.

  Patent Document 3 is a technique relating to an electrochemical device including a positive electrode in which a protective film is formed by a complex between the surface of a positive electrode active material and an aliphatic nitrile compound. According to this technique, it is possible to prevent the transition metal in the positive electrode active material from being eluted by charge and discharge, and to suppress side reactions and gas generation between the electrolytic solution and the positive electrode.

  Patent Document 4 is a technique in which an electrolytic solution contains a nitrile compound having a carbon-carbon unsaturated bond. According to this technique, it is said that a non-aqueous electrolyte secondary battery with little decomposition of the electrolyte, high charge / discharge efficiency, and excellent storage characteristics and cycle characteristics at high temperatures can be obtained.

  Patent Document 5 is a technique in which sultone or cycloalkylbenzene is included in a nonaqueous electrolyte. According to this technique, it is said that a non-aqueous electrolyte secondary battery having excellent high-temperature storage characteristics can be obtained.

  Patent Document 6 is a technique of adding a nitrile compound and an S═O group-containing compound or a small amount of a dinitrile compound to the non-aqueous electrolyte. According to this technique, a lithium secondary battery excellent in battery characteristics such as cycle characteristics, battery capacity, and storage characteristics can be obtained.

  Patent Document 7 is a technique for including an organic titanate in an electrolytic solution. According to this technique, a non-aqueous secondary battery having excellent cycle characteristics is obtained.

  Patent Document 8 is a technique in which 4-fluoro-1,3-dioxolan-2-one is included in an electrolytic solution. According to this technique, a battery having excellent charge / discharge efficiency is obtained.

  Patent Document 9 is a technique in which cycloalkylbenzene or tert-amylbenzene is included in the nonaqueous electrolyte. According to this technology, a nonaqueous electrolyte secondary battery excellent in overcharge safety and high-temperature cycle characteristics is obtained.

  However, a battery that can suppress the reaction between the positive electrode and the non-aqueous electrolyte and has excellent cycle characteristics in a low temperature environment has not yet been realized.

  This invention is made | formed in view of the above, Comprising: It aims at providing the nonaqueous electrolyte secondary battery which had the reaction suppression function of a positive electrode and a nonaqueous electrolyte, and the outstanding low-temperature cycle characteristic.

  The present invention for solving the above-mentioned problems is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte having a non-aqueous solvent and an electrolyte salt. 1.0% by mass of a chelate compound having a structure represented by the following general formula (I), 0.2% by mass or more of a cyclic ether compound, a sultone compound, cyclohexylbenzene, tert-alkylbenzene, a nitrile compound, and 4- And at least one compound selected from the group consisting of fluoro-1,3-dioxolan-2-one.

（Ｍは、Ａｌ，Ｚｒ，Ｃｏのいずれかの金属原子であり、Ｒ１，Ｒ２は、それぞれ炭素数１８以下のアルキル基またはアルコキシ基を示す。Ｒ１，Ｒ２は同一であってもよく、異なっていてもよい。また、アルキル基、アルコキシ基は、直鎖状、分枝状のいずれであってもよい。また、ｎは４以下の自然数である。）

(M is any metal atom of Al, Zr, and Co, and R1 and R2 each represent an alkyl group or an alkoxy group having 18 or less carbon atoms. R1 and R2 may be the same or different. In addition, the alkyl group and the alkoxy group may be linear or branched, and n is a natural number of 4 or less.)

  In this configuration, at least one selected from the group consisting of a cyclic ether compound, a sultone compound, a cyclohexylbenzene, a tert-alkylbenzene, a nitrile compound, and 4-fluoro-1,3-dioxolan-2-one contained in the nonaqueous electrolyte. This compound (hereinafter referred to as the additive of the present invention) forms a good film on the surface of the positive electrode and suppresses the reaction between the positive electrode and the nonaqueous solvent, so that the storage characteristics are improved. In addition, the chelate compound acts to enhance the low temperature cycle characteristics. Therefore, these effects act synergistically to obtain a nonaqueous electrolyte secondary battery having high charge storage characteristics and excellent low-temperature cycle characteristics.

  Here, the said effect is not fully acquired as content of the said chelate compound is less than 0.005 mass%. On the other hand, when the amount is more than 1.0% by mass, the amount of the acid component in the non-aqueous electrolyte becomes excessive, and the positive electrode tends to deteriorate. Therefore, it is preferable to regulate within the above range.

  Moreover, the said effect is not fully acquired as content of the said invention additive is less than 0.2 mass%. Moreover, when there is more content of this invention additive than 7.0 mass%, the upper limit of an effect will be reached and the addition beyond it will lead to high cost. Therefore, Preferably the upper limit of content of this invention additive shall be 7.0 mass%. More preferably, the addition amount of the additive of the present invention is 0.5 to 2.0% by mass, and more preferably 0.5 to 1.0% by mass.

  Here, the mass ratio of the chelate compound and the additive of the present invention in the non-aqueous electrolyte is the whole non-aqueous electrolyte (non-aqueous solvent + electrolyte salt + chelate compound + additive of the present invention (if necessary + other additives) )) Means the proportion of the mass. When a polymer electrolyte is used, the polymer component is included in the above other additives.

  The metal atom M in the general formula (I) is more preferably Al since the effect of improving the high temperature characteristics is great.

  Moreover, since the effect which improves a high temperature characteristic is large, it is more preferable that at least one of R1, R2 in the said general formula (I) is made into an alkoxy group.

  Moreover, since the effect of improving the high temperature characteristics is great, it is more preferable to employ a configuration in which at least one alkoxy group is bonded to the metal atom M in the general formula (I).

  According to the present invention, a nonaqueous electrolyte secondary battery having high storage characteristics and excellent low temperature characteristics can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

Example 1
<Preparation of positive electrode>
Lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, carbon black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder at a mass ratio of 95: 2.5: 2.5 These were mixed with N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode active material slurry.

  Next, this positive electrode active material slurry was applied with a uniform thickness on both surfaces of a positive electrode core body made of a strip-shaped aluminum foil (thickness: 12 μm) using a doctor blade. This electrode plate was passed through a dryer to remove the organic solvent (NMP) used during slurry adjustment, and a dried electrode plate was produced. The dried electrode plate was rolled using a roll press to produce a positive electrode plate. The positive electrode plate thus prepared was cut into a predetermined size to obtain a positive electrode.

<Production of negative electrode>
Artificial graphite (d = 0.335 nm) as a negative electrode active material, carbon powder as a conductive agent, styrene butadiene rubber as a binder, and carboxymethyl cellulose as a thickener are in a mass ratio of 95: 3: These were mixed at a ratio of 1: 1 and mixed with water to prepare a negative electrode active material slurry.

  Next, this negative electrode active material slurry was applied to both surfaces of a negative electrode core made of a strip-shaped copper foil (thickness: 8 μm) with a uniform thickness using a doctor blade. This electrode plate was passed through a drier to remove the water used during slurry adjustment, and a dried electrode plate was produced. Then, this dry electrode plate was rolled with a roll press to produce a negative electrode plate. The negative electrode plate thus produced was cut into a predetermined size to obtain a negative electrode.

<Production of electrode body>
The positive electrode, the negative electrode and a separator made of a polyethylene microporous film (thickness: 12 μm) are superposed, wound by a winder, provided with an insulating winding tape, and then pressed to form a flat spiral The electrode body was completed.

<Preparation of non-aqueous electrolyte>
In a non-aqueous solvent in which ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 2: 1: 7 (when converted to 1 atm and 25 ° C.), the electrolyte An electrolyte solution was prepared by dissolving LiPF ₆ as a salt at a rate of 1.0 M (mol / liter).

  The above electrolytic solution, aluminum ethyl acetoacetate diisopropylate (Compound 1), and propiononitrile were mixed at a mass ratio of 99.7: 0.1: 0.2 to obtain a nonaqueous electrolyte.

<Battery assembly>
A commercially available aluminum laminate was folded to form the bottom. Thereafter, the laminate material was molded into a cup shape to provide a storage space. The electrode body was housed in the housing space, and the portions other than the portion to be injected were thermally welded. Thereafter, the non-aqueous electrolyte was injected and thermally welded to produce a battery according to Example 1 having a design capacity of 1500 mAh.

(Example 2)
Except for using the non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and propiononitrile at a mass ratio of 99.4: 0.1: 0.5, the above examples In the same manner as in Example 1, a battery according to Example 2 was produced.

(Example 3)
The above examples except that the non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and succinonitrile at a mass ratio of 98.9: 0.1: 1.0 was used. In the same manner as in Example 1, a battery according to Example 3 was produced.

Example 4
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and adiponitrile at a mass ratio of 99.7: 0.1: 0.2 was used. Similarly, a battery according to Example 4 was produced.

(Example 5)
Example 1 except that a nonaqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 99.4: 0.1: 0.5 was used. Similarly, a battery according to Example 5 was produced.

(Example 6)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate / diisopropylate and adiponitrile at a mass ratio of 98.9: 0.1: 1.0 was used. Similarly, a battery according to Example 6 was produced.

(Example 7)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate / diisopropylate and adiponitrile at a mass ratio of 97.9: 0.1: 2.0 was used. Similarly, a battery according to Example 7 was produced.

(Example 8)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 96.9: 0.1: 3.0 was used. Similarly, a battery according to Example 8 was produced.

Example 9
Example 1 except that a non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and sebaconitrile at a mass ratio of 99.7: 0.1: 0.2 was used. Similarly, a battery according to Example 9 was produced.

(Example 10)
Example 1 except that a non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and sebaconitrile at a mass ratio of 98.9: 0.1: 1.0 was used. Similarly, a battery according to Example 10 was produced.

(Example 11)
Example 1 except that a non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and sebaconitrile at a mass ratio of 98.4: 0.1: 1.5 was used. Similarly, a battery according to Example 11 was produced.

Example 12
The above implementation was performed except that a nonaqueous electrolyte in which the above electrolyte solution, aluminum ethyl acetoacetate diisopropylate, and tert-amylbenzene were mixed at a mass ratio of 99.7: 0.1: 0.2 was used. A battery according to Example 12 was made in the same manner as Example 1.

(Example 13)
The above implementation was performed except that a non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and tert-amylbenzene were mixed at a mass ratio of 99.4: 0.1: 0.5 was used. A battery according to Example 13 was made in the same manner as Example 1.

(Example 14)
The above implementation was performed except that a non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and tert-amylbenzene were mixed at a mass ratio of 98.9: 0.1: 1.0 was used. A battery according to Example 14 was made in the same manner as Example 1.

(Example 15)
The above implementation was performed except that a non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and tert-amylbenzene were mixed at a mass ratio of 97.9: 0.1: 2.0 was used. A battery according to Example 15 was made in the same manner as Example 1.

(Example 16)
Except for using the non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane in a mass ratio of 99.6: 0.1: 0.3, A battery according to Example 16 was made in the same manner as Example 1.

(Example 17)
Except for using the non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane at a mass ratio of 99.4: 0.1: 0.5, A battery according to Example 17 was made in the same manner as Example 1.

(Example 18)
Except for using the non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane in a mass ratio of 98.9: 0.1: 1.0 A battery according to Example 18 was made in the same manner as Example 1.

(Example 19)
Except for using the non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane in a mass ratio of 98.4: 0.1: 1.5, A battery according to Example 19 was made in the same manner as Example 1.

(Example 20)
Except for using the non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane at a mass ratio of 97.9: 0.1: 2.0, A battery according to Example 20 was made in the same manner as Example 1.

(Example 21)
Except for using the non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-dioxane at a mass ratio of 96.9: 0.1: 3.0 A battery according to Example 21 was made in the same manner as Example 1.

(Example 22)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and cyclohexylbenzene at a mass ratio of 98.9: 0.1: 1.0 was used. In the same manner as described above, a battery according to Example 22 was fabricated.

(Example 23)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and cyclohexylbenzene in a mass ratio of 98.4: 0.1: 1.5 was used. In the same manner as described above, a battery according to Example 23 was produced.

(Example 24)
Except for using a non-aqueous electrolyte in which the above electrolyte, aluminum ethyl acetoacetate diisopropylate, and 1,3-propane sultone were mixed at a mass ratio of 99.4: 0.1: 0.5, In the same manner as in Example 1, a battery according to Example 24 was produced.

(Example 25)
Except for using a non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 1,3-propene sultone were mixed at a mass ratio of 99.4: 0.1: 0.5, In the same manner as in Example 1, a battery according to Example 25 was produced.

(Example 26)
A non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 99.7: 0.1: 0.2 A battery according to Example 26 was made in the same manner as Example 1 except that was used.

(Example 27)
A non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 99.4: 0.1: 0.5 A battery according to Example 27 was made in the same manner as Example 1 except that was used.

(Example 28)
A non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 98.9: 0.1: 1.0 A battery according to Example 28 was made in the same manner as Example 1 except that was used.

(Example 29)
A non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 97.9: 0.1: 2.0 A battery according to Example 29 was made in the same manner as Example 1 except that was used.

(Example 30)
Nonaqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 94.9: 0.1: 5.0 A battery according to Example 30 was made in the same manner as Example 1 except that was used.

(Comparative Example 1)
A battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that the above electrolytic solution was used as a nonaqueous electrolyte (not including a chelate compound and vinylene carbonate).

(Comparative Example 2)
Comparative Example 2 was performed in the same manner as in Example 1 except that a nonaqueous electrolyte in which the above electrolytic solution and aluminum ethyl acetoacetate / diisopropylate were mixed at a mass ratio of 99.9: 0.1 was used. The battery which concerns on was produced.

(Comparative Example 3)
The above examples except that the non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and propiononitrile at a mass ratio of 99.8: 0.1: 0.1 was used. In the same manner as in Example 1, a battery according to Comparative Example 3 was produced.

(Comparative Example 4)
A battery according to Comparative Example 4 was produced in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and succinonitrile were mixed at a mass ratio of 99.0: 1.0 was used. did.

(Comparative Example 5)
Example 1 except that a non-aqueous electrolyte prepared by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 99.8: 0.1: 0.1 was used. Similarly, a battery according to Comparative Example 5 was produced.

(Comparative Example 6)
A battery according to Comparative Example 6 was produced in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and adiponitrile were mixed at a mass ratio of 99.0: 1.0 was used.

(Comparative Example 7)
A battery according to Comparative Example 7 was produced in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and sebacononitrile were mixed at a mass ratio of 99.0: 1.0 was used.

(Comparative Example 8)
The above implementation was performed except that a nonaqueous electrolyte in which the above electrolyte solution, aluminum ethyl acetoacetate diisopropylate, and tert-amylbenzene were mixed at a mass ratio of 99.8: 0.1: 0.1 was used. A battery according to Comparative Example 8 was produced in the same manner as Example 1.

(Comparative Example 9)
A battery according to Comparative Example 9 was obtained in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and tert-amylbenzene were mixed at a mass ratio of 99.0: 1.0 was used. Produced.

(Comparative Example 10)
A battery according to Comparative Example 10 in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and 1,3-dioxane were mixed at a mass ratio of 98.5: 1.5 was used. Was made.

(Comparative Example 11)
A battery according to Comparative Example 11 was produced in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolyte solution and cyclohexylbenzene were mixed at a mass ratio of 99.0: 1.0 was used. .

(Comparative Example 12)
According to Comparative Example 12 in the same manner as in Example 1 except that a non-aqueous electrolyte in which the electrolytic solution and 1,3-propane sultone were mixed at a mass ratio of 99.5: 0.5 was used. A battery was produced.

(Comparative Example 13)
According to Comparative Example 13, except that a nonaqueous electrolyte obtained by mixing the electrolytic solution and 1,3-propene sultone at a mass ratio of 99.5: 0.5 was used. A battery was produced.

(Comparative Example 14)
A non-aqueous electrolyte in which the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate, and 4-fluoro-1,3-dioxolan-2-one are mixed at a mass ratio of 99.8: 0.1: 0.1 A battery according to Comparative Example 14 was produced in the same manner as in Example 1 except that was used.

(Comparative Example 15)
Except having used the non-aqueous electrolyte which mixed the said electrolyte solution and 4-fluoro- 1, 3- dioxolan-2-one by mass ratio 99.0: 1.0, it is the same as that of the said Example 1, and the same. Thus, a battery according to Comparative Example 15 was produced.

[Measurement of charge storage characteristics]
Two batteries were respectively produced under the same conditions as in Examples 1 to 30 and Comparative Examples 1 to 15, and these batteries were charged and discharged under the following conditions, and then charged again. Thereafter, the battery was left in a constant temperature bath at 80 ° C. for 96 hours. One side of the battery after storage was partially opened, and the amount of gas generated was measured. The other battery was discharged under the following conditions, and the capacity remaining rate was calculated according to the following formula. These results are shown in Table 1 below.
Charging: Until the voltage reaches 4.2 V at a constant current of 1 It (1500 mA), then discharge until the current reaches 130 mA at a constant voltage of 4.2 V: Capacity remains until the voltage reaches 2.75 V at a constant current of 1 It (1500 mA) Rate (%) = discharge capacity after storage ÷ discharge capacity before storage x 100
In addition, the said charging / discharging was performed in 23 degreeC environment.

[Measurement of low-temperature cycle characteristics]
Batteries were produced under the same conditions as in Examples 1 to 30 and Comparative Examples 1 to 15, and these batteries were charged and discharged under the following conditions to measure low-temperature cycle characteristics. The results are shown in Table 1 below.
Charging: Until the voltage reaches 4.2 V at a constant current of 1 It (1500 mA), and then discharge until the current reaches 130 mA at a constant voltage of 4.2 V: Until the voltage reaches 2.75 V at a constant current of 1.0 It (1500 mA) Low temperature cycle characteristics (%) = 300th cycle discharge capacity / first cycle discharge capacity × 100
In addition, the said charging / discharging was performed in 5 degreeC environment.

  From Table 1 above, Examples 1 to 30 containing 0.2% by mass or more of the additive of the present invention and aluminum ethyl acetoacetate diisopropylate in the nonaqueous electrolyte had a gas generation amount of 0.4 to 3 .6 ml, capacity remaining rate of 60 to 84%, low temperature cycle characteristics of 67 to 82%, while the content of the additive of the present invention is 0.1% by mass or less, Comparative Examples 1 to 3, 5, 8 and 14, it can be seen that the amount of gas generated is 4.7 to 5.3 ml, the capacity remaining rate is 30 to 41%, and the low temperature cycle characteristic is 77 to 84%.

  This is considered as follows. When the content of the additive of the present invention is less than 0.2% by mass, it is not possible to suppress the reaction between the positive electrode and the nonaqueous electrolyte during charge storage. Therefore, in 1 to 3, 5, 8, and 14, when charged and stored, the positive electrode and the nonaqueous electrolyte react to generate gas, and the generated gas stays in the battery so that the positive and negative electrodes face each other. Since it worsens, the discharge capacity (capacity remaining rate) after storage decreases. For this reason, it is preferable to contain 0.2 mass% or more of this invention additive in a non-aqueous electrolyte. More preferably, it is 0.2-7.0 mass%, More preferably, it is 0.5-2.0 mass%, Most preferably, it is 0.5-1.0 mass%.

  From Table 1 above, Examples 1 to 30 containing 0.2% by mass or more of the additive of the present invention and aluminum ethyl acetoacetate diisopropylate in the nonaqueous electrolyte have a gas generation amount of 0.4. -3.6 ml, capacity remaining rate is 60-84%, low temperature cycle characteristics are 67-82%, while containing 0.5-1.5% by mass of the additive of the present invention, and aluminum ethyl acetoacetate Comparative Examples 4, 6, 7, 9 to 13 and 15 not containing diisopropylate have a gas generation amount of 0.5 to 2.4 ml, a capacity remaining rate of 64 to 82%, and a low temperature cycle characteristic of 31 to 51. It can be seen that the low-temperature cycle characteristics are greatly inferior.

  This is considered as follows. When the additive of the present invention is contained in the non-aqueous electrolyte, the charge storage characteristics can be improved by suppressing the reaction between the positive electrode and the non-aqueous electrolyte, but the low-temperature cycle characteristics are deteriorated. Here, when a chelate compound is further contained in the nonaqueous electrolyte, the low temperature cycle characteristics can be improved without impairing the effect of improving the charge storage characteristics by the additive of the present invention.

  From Table 1 above, it is more preferable to use a nitrile compound (propiononitrile, succinonitrile, adiponitrile, sebaconitrile), a cyclic ether compound (1,3-dioxane), or cyclohexylbenzene as the additive of the present invention. I understand.

(Examination of chelate compounds)
In order to examine the type and content of the chelate compound, batteries according to Examples 31 to 40 and Comparative Examples 16 to 20 were produced, and the performance was evaluated.

(Example 31)
Except for using the non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate (compound 1), and adiponitrile at a mass ratio of 98.995: 0.005: 1.0 A battery according to Example 31 was made in the same manner as Example 1.

(Example 32)
Example 1 except that a nonaqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 98.975: 0.025: 1.0 was used. Similarly, a battery according to Example 32 was produced.

(Example 33)
Example 1 except that a nonaqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 98.5: 0.5: 1.0 was used. Similarly, a battery according to Example 33 was produced.

(Example 34)
Example 1 except that a nonaqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 98.0: 1.0: 1.0 was used. Similarly, a battery according to Example 34 was produced.

(Example 35)
A battery according to Example 35 was made in the same manner as in Example 6 except that aluminum monoisopropoxymonooleoxyethyl acetoacetate (Compound 2) was used instead of aluminum ethylacetoacetate diisopropylate. did.

(Example 36)
A battery according to Example 36 was made in the same manner as in Example 6 except that aluminum bisethyl acetoacetate monoacetyl acetate (Compound 3) was used instead of aluminum ethyl acetoacetate diisopropylate. .

(Example 37)
A battery according to Example 37 was made in the same manner as Example 6 except that aluminum trisethyl acetoacetate (Compound 4) was used instead of aluminum ethyl acetoacetate diisopropylate.

(Example 38)
A battery according to Example 38 was made in the same manner as Example 6 except that aluminum trisacetylacetonate (Compound 5) was used instead of aluminum ethyl acetoacetate diisopropylate.

(Example 39)
A battery according to Example 39 was made in the same manner as Example 6 except that zirconium tetrakisacetylacetonate (Compound 6) was used instead of aluminum ethyl acetoacetate diisopropylate.

(Example 40)
A battery according to Example 40 was made in the same manner as in Example 6 except that cobalt bisacetylacetonate (Compound 7) was used instead of aluminum ethyl acetoacetate / diisopropylate.

(Comparative Example 16)
Example 1 except that a nonaqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate diisopropylate and adiponitrile at a mass ratio of 98.997: 0.003: 1.0 was used. Similarly, a battery according to Comparative Example 16 was produced.

(Comparative Example 17)
Example 1 except that a non-aqueous electrolyte obtained by mixing the above electrolytic solution, aluminum ethyl acetoacetate / diisopropylate and adiponitrile at a mass ratio of 97.0: 2.0: 1.0 was used. Similarly, a battery according to Comparative Example 17 was produced.

(Comparative Example 18)
A battery according to Comparative Example 18 was produced in the same manner as in Example 6 except that titanium diisopropoxide bisacetylacetonate (Compound 8) was used instead of aluminum ethyl acetoacetate / diisopropylate. .

(Comparative Example 19)
A battery according to Comparative Example 19 was prepared in the same manner as in Example 6 except that titanium bis (ethylacetoacetate) diisopropoxide (Compound 9) was used instead of aluminum ethylacetoacetate / diisopropylate. Produced.

(Comparative Example 20)
A battery according to Comparative Example 20 was produced in the same manner as in Example 6 except that iron trisacetylacetonate (Compound 10) was used instead of aluminum ethyl acetoacetate / diisopropylate.

[Measurement of battery characteristics]
Batteries were produced under the same conditions as in Examples 31 to 40 and Comparative Examples 16 to 20, and the charge storage characteristics and low temperature cycle characteristics were measured for these batteries in the same manner as described above. These results are shown in Table 3 below together with the results of Example 6.

  The structure of the chelate compound (the functional group bonded to M, R1, R2, n, and M in the general formula (I)) is as shown in Table 2 below.

  From Table 3 above, Examples 6, 31 to 34, in which the content of aluminum ethyl acetoacetate diisopropylate is 50 to 10,000 ppm (0.005 to 1.0 mass%), the gas generation amount is 0.4 to 0.4. Comparative Example 16 in which the content of aluminum ethyl acetoacetate and diisopropylate is 30 ppm, while 0.6 ml, the residual capacity rate is 76 to 82%, and the low temperature cycle characteristic is 61 to 82% Is 0.5 ml, the residual capacity rate is 81%, the low-temperature cycle characteristics are 43%, a decrease in low-temperature cycle characteristics is seen, and the content of aluminum ethyl acetoacetate diisopropylate is 20000 ppm. Generated volume is 0.7ml, capacity remaining rate is 51%, low temperature cycle characteristics are 81%, and capacity remaining rate is inferior

  This is considered as follows. When the content of aluminum ethyl acetoacetate / diisopropylate is less than 50 ppm, the effect of aluminum ethylacetoacetate / diisopropylate cannot be sufficiently obtained, so that the low-temperature cycle characteristics deteriorate. On the other hand, when the content of aluminum ethyl acetoacetate / diisopropylate is more than 10,000 ppm, the amount of the acid component in the non-aqueous electrolyte becomes excessive, and the positive electrode tends to be deteriorated, so that the capacity remaining rate is lowered. For this reason, it is preferable that content of aluminum ethyl acetoacetate diisopropylate (chelate compound which has a structure shown by the said general formula (I)) is 50-10000 ppm. More preferably, it is 500-2000 ppm, More preferably, it is 100-1000 ppm.

  Further, from Table 3 above, Examples 6 and 35 to 35 contain 1000 ppm of any one of Compounds 1 to 7 in which the metal atom M in the structure represented by the general formula (I) is Al, Zr, or Co in the nonaqueous electrolyte. No. 40 has a gas generation amount of 0.4 to 0.9 ml, a capacity remaining rate of 70 to 81%, and a low temperature cycle characteristic of 64 to 82%, whereas a metal atom in the structure represented by the above general formula (I) Comparative Examples 18 to 20 containing any of compounds 8 to 10 in which M is Ti or Fe in the nonaqueous electrolyte have a gas generation amount of 1.3 to 1.7 ml, a capacity remaining rate of 48 to 53%, and a low temperature. It turns out that cycling characteristics are inferior with 53-60.

  This is considered to be because a chelate compound in which the metal atom M is Ti and Fe cannot obtain the effect as the compound having the structure shown in the general formula (I). Therefore, the metal atom M is preferably any one of Al, Zr, and Co.

  Further, from Table 3 above, Examples 6, 35 to 38 using 100 ppm of compounds 1 to 5 in which the metal atom M of the chelate compound is Al have a gas generation amount of 0.4 to 0.6 ml and a capacity remaining rate. The amount of gas generated was 0.9 ml, the residual capacity rate was 70%, and the low temperature cycle of Example 39 using 73 to 81%, low temperature cycle characteristics of 70 to 82%, and the compound 6 in which the metal atom M of the chelate compound is Zr. It can be seen that the characteristics of 64%, Example 40 using the compound 7 in which the metal atom M of the chelate compound is Co, are superior to the gas generation amount of 0.8 ml, the capacity remaining rate of 71%, and the low temperature cycle characteristics of 67%. . From this, the metal atom M is more preferably Al.

  From Table 3 above, Examples 6, 35 to 37 using compounds 1 to 4 in which at least one of the side chains R1 and R2 of the chelate compound is an alkoxy group have a low temperature cycle characteristic of 74 to 82%, It can be seen that the low-temperature cycle characteristics of Example 38 using Compound 5 in which both side chains R1 and R2 of the chelate compound are methyl groups are superior to 70%. From this, it is more preferable that at least one of the side chains R1 and R2 is an alkoxy group.

  From Table 3 above, Examples 6 and 35 using compounds 1 and 2 in which an alkoxy group is bonded to the metal atom M of the chelate compound have a capacity remaining rate of 81%, 80%, and a low temperature cycle characteristic of 82. %, 81%, and Examples 36 to 38 using compounds 3 to 5 in which the alkoxy group is not bonded to the metal atom M of the chelate compound, capacity remaining rate 73 to 76%, low temperature cycle characteristics 70 to 76% It turns out that it is excellent. Therefore, it is more preferable to use a compound in which an alkoxy group is bonded to the metal atom M.

(extra content)
As the cyclic ether compound, oxetane, tetrahydrofuran, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, isopropyldimethyl-1,3-dioxane, crown ether and the like can be used. 1,3-dioxane is preferred.

  Examples of nitrile compounds include acetonitrile, propiononitrile, butyronitrile, valeronitrile, hexanenitrile, octanenitrile, undecanenitrile, cyclohexanecarbonitrile, benzonitrile, succinonitrile, glutaronitrile, 2-methylglutaronitrile, adiponitrile, and pimelonitrile. , Suberonitrile, Azeronitrile, Sebacononitrile, Undecandinitrile, Dodecanedinitrile, 1,2,3-propanetricarbonitrile, 1,2,3-Tris (2-cyanoethoxy) propane, 1,3,5-cyclohexanetricarb Nitrile, 1,3,5-pentanetricarbonitrile, tert-butylmalononitrile, malononitrile, 3,3′-oxydipropiononitrile, 3,3′-thiodipropio Nitrile, 1,2-dicyanobenzene, 1,3-dicyanobenzene, and 1,4-dicyanobenzene, and the like. Of these, dinitrile compounds are preferred. As the dinitrile compound, adiponitrile, pimelonitrile, succinonitrile, and glutaronitrile are particularly preferable.

  As the tert-alkylbenzene, tert-amylbenzene, tert-butylbenzene and the like are preferable.

  As the sultone compound, 1,3-propane sultone, 1,3-propene sultone, pentane-2,5-sultone, 1,4-butane sultone, 1,8-naphtho sultone, or the like can be used. Among these, 1,3-propane sultone and 1,3-propene sultone are preferable.

As the positive electrode active material, it is preferable to use a lithium transition metal composite oxide, a lithium transition metal phosphate compound having an olivine structure, or the like. Examples of the lithium transition metal composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiNi _x Mn _1-x O ₂ (0 <x <1), LiNi _x Co _1-x O ₂ (0 < _{x <1), LiNi x Mn} y Co 1-xy O 2 (0 <x <1,0 <y <1,0 <x + y <1) and the like are preferable. Moreover, as a lithium transition metal phosphate compound having an olivine structure, LiFePO ₄ or the like is preferable. These can be used alone, or can be used in combination of two or more. In order to suppress gas generation, a known additive such as lithium phosphate may be added to the positive electrode.

As the negative electrode active material, it is preferable to use a carbon material, a titanium oxide, a metalloid element, an alloy, or the like. As the carbon material, natural graphite, artificial graphite, non-graphitizable carbon and the like are preferable. As the titanium oxide, LiTiO ₂ , TiO ₂ or the like is preferable. As the metalloid element, silicon, tin and the like are preferable. As the alloy, a Sn—Co alloy or the like is preferable. These can be used alone, or can be used in combination of two or more.

  Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; lactones such as γ-butyrolactone and γ-valerolactone; dimethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, dinormal butyl carbonate, and the like. Chain carbonates, carboxylic acid esters such as methyl pivalate, ethyl pivalate, methyl isobutyrate, methyl propionate, chain ethers such as 1,2-dimethoxyethane, N, N′-dimethylformamide It is preferable to use amides such as N-methyloxazolidinone, sulfur-containing compounds such as sulfolane, room temperature molten salts such as 1-ethyl-3-methylimidazolium tetrahydroborate, etc., or a mixture thereof. Among these, cyclic carbonates, chain carbonates, and tertiary carboxylic acid esters are more preferable.

  Also, one or more known additives such as vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, glycolic anhydride, ethylene sulfite, divinyl sulfone, vinyl acetate, vinyl pivalate, catechol carbonate, biphenyl, etc. It may be added to the seed non-aqueous electrolyte.

As the electrolyte salt, LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₂ CF ₃ SO ₂ ) ₂ or the like may be mixed. It is preferable to use it. Moreover, it is preferable that the density | concentration of electrolyte salt shall be 0.5-2.0M (mol / liter).

  As the separator, it is preferable to use a microporous film made of a polyolefin resin material such as polyethylene or polypropylene. In addition, in order to ensure shutdown response, a resin having a low melting point (150 ° C. or lower) is mixed, a resin having a high melting point (higher than 150 ° C.) is laminated to support heat resistance, or inorganic particles are supported. You may let them.

  The present invention can also be applied to a polymer electrolyte secondary battery. As the polymer electrolyte, a gel polymer electrolyte is preferable. The polymer component used in the polymer electrolyte is preferably an alkylene oxide polymer or a fluorine polymer such as polyvinylidene fluoride-hexafluoropropylene copolymer.

  As a method for producing a polymer electrolyte, for example, a monomer having an unsaturated double bond such as an acryloyl group, a methacryloyl group, a vinyl group or an allyl group, or a cationically polymerizable cyclic ether group such as an epoxy, oxetane or formal is used. A method of polymerizing the monomer after the monomer is contained in the nonaqueous electrolyte can be employed. The polymerization of the monomer may be performed after the battery is assembled.

  Monomers having an unsaturated double bond include acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, ethoxyethyl methacrylate, polyethylene glycol Monomethacrylate, N, N-diethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, polyalkylene glycol Dimethacrylate, polyalkylene glycol dimethacrylate, trimethylol propane alkoxylate triacrylate, pentaerythritol alkoxylate tetraacrylate, can be used pentaerythritol alkoxylate tetraacrylate. As the monomer having a cyclic ether group, a copolymer of methyl methacrylate and (3-ethyl-3-oxetanyl) methyl acrylate, tetraethylene glycol bisoxetane, polyvinyl formal, or the like can be used.

  The monomer having an unsaturated double bond can be polymerized by heat, ultraviolet light, electron beam or the like, but a polymerization initiator may be added to the non-aqueous electrolyte in order to make the reaction proceed effectively. Examples of the polymerization initiator include organic compounds such as benzoyl peroxide, t-butyl peroxycumene, lauroyl peroxide, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, and t-hexyl peroxyisopropyl monocarbonate. Peroxides can be used.

A monomer having a cyclic ether group can be polymerized by heat or charge / discharge with Li ⁺ or a small amount of H ⁺ in the nonaqueous electrolyte.

  As another method for producing the polymer electrolyte, a method in which a polymer component is dissolved in a high temperature non-aqueous electrolyte and cooled can be employed. In this case, any polymer component may be used as long as it is in a gel state containing a nonaqueous electrolyte at room temperature and is stable as a battery material. Examples of such a polymer component include polymers having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone, acrylic derivative polymers such as polymethyl acrylate and polyethyl acrylate, fluorine-based compounds such as polyvinyl fluoride and polyvinylidene fluoride. Examples thereof include resins, polyvinyl alcohol polymers such as polyvinyl acetate and polyvinyl alcohol, and halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Moreover, a mixture with said polymer etc., a modified body, a derivative, a random copolymer, a graft copolymer, a block copolymer, etc. may be sufficient. The weight average molecular weight of these polymer components is usually in the range of 10,000 to 5,000,000.

When a monomer having an unsaturated bond is polymerized by heat, ultraviolet light, electron beam, etc. to form a polymer electrolyte, its added amount ((non-aqueous solvent + electrolyte salt + chelate compound + additive of the present invention + monomer (necessary If present, the proportion of the polymerization initiator and other additives)) in the mass) is preferably 1.5 to 15% by mass, more preferably 3 to 7% by mass, and further preferably 4.5 to 5.%. 8% by mass.
When using a polymerization initiator, the addition amount is preferably 500 ppm to 1% by mass, more preferably 1000 ppm to 5000 ppm, based on the total electrolytic mass.

  When using the compound which has cyclic ether groups, such as polyvinyl formal, the addition amount becomes like this. Preferably it is 0.5-5 mass%, More preferably, it is 1-2.5 mass%, More preferably, it is 1.5-2. 0% by mass.

  When a polymer is dissolved in a high temperature non-aqueous electrolyte and cooled to prepare a polymer electrolyte, the addition amount is preferably 10 to 35% by mass, more preferably 15 to 30% by mass, Preferably it is 20-25 mass%.

  As described above, according to the present invention, a nonaqueous electrolyte secondary battery excellent in charge storage characteristics and low temperature cycle characteristics can be realized. Therefore, industrial applicability is great.

Claims (4)

In a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte having a non-aqueous solvent and an electrolyte salt,
The nonaqueous electrolyte includes 0.005 to 1.0% by mass of a chelate compound having a structure represented by the following general formula (I), 0.2% by mass or more of a cyclic ether compound, a sultone compound, cyclohexylbenzene, tert-alkylbenzene, a nitrile compound, and at least one compound selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one,
A non-aqueous electrolyte secondary battery.

(M is any metal atom of Al, Zr, and Co, and R1 and R2 each represent an alkyl group or an alkoxy group having 18 or less carbon atoms. R1 and R2 may be the same or different. In addition, the alkyl group and the alkoxy group may be linear or branched, and n is a natural number of 4 or less.) The nonaqueous electrolyte secondary battery according to claim 1,
The metal atom M is Al;
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1 or 2,
At least one of R1 and R2 is an alkoxy group,
A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3,
At least one alkoxy group is bonded to the metal atom M,
A non-aqueous electrolyte secondary battery.