JP5119182B2 - Method for producing lithium ion secondary battery - Google Patents

Description

The present invention relates to a method for producing a lithium ion secondary batteries.

  Lithium ion secondary batteries are attracting attention as power sources for portable devices and as power sources for electric vehicles and hybrid vehicles. Currently, a lithium ion secondary battery has a positive electrode active material made of a composite oxide containing lithium and a transition metal, a negative electrode active material made of a carbon material, and a non-aqueous electrolyte solution made of a Li salt and a non-aqueous solvent. The thing has become mainstream (for example, refer patent document 1, 2).

JP 2007-35356 A JP 2007-48464 A

  In the lithium ion secondary batteries of Patent Documents 1 and 2, a nonaqueous electrolyte solution containing a specific anion compound is used as the nonaqueous electrolyte solution. It is described that a high output can be maintained even when charging and discharging are repeated by including a specific anionic compound in the non-aqueous electrolyte.

Incidentally, LiPF ₆ is known as a Li salt to be contained in the nonaqueous electrolytic solution. By using LiPF ₆ , the output characteristics of the lithium ion secondary battery can be particularly improved. However, when LiPF ₆ is used, hydrofluoric acid may be generated due to the reaction between a small amount of moisture mixed in the battery during the manufacturing process (which is mixed into the non-aqueous electrolyte) and LiPF ₆ . The hydrofluoric acid causes corrosion of the positive electrode active material and a reaction in which components contained in the positive electrode active material are eluted into the electrolytic solution. For this reason, when charging and discharging are repeated, the discharge capacity is remarkably lowered and the internal resistance is greatly increased.

  On the other hand, the specific anionic compounds disclosed in Patent Documents 1 and 2 have a characteristic of capturing moisture mixed in the nonaqueous electrolyte and hydrofluoric acid generated in the nonaqueous electrolyte. . Therefore, it was thought that the said subject can be solved by using the nonaqueous electrolyte solution containing the specific anion compound currently disclosed by patent document 1,2.

  However, the specific anion compounds disclosed in Patent Documents 1 and 2 are gradually reduced and decomposed on the surface of the negative electrode active material made of a carbon material. For this reason, even if the specific anionic compound disclosed in Patent Documents 1 and 2 is contained in the non-aqueous electrolyte, it is sufficiently generated in the water mixed in the non-aqueous electrolyte or in the non-aqueous electrolyte. The hydrofluoric acid could not be captured. Therefore, in the lithium ion secondary batteries of Patent Documents 1 and 2, it was impossible to suppress a decrease in discharge capacity and an increase in internal resistance due to repeated charge and discharge.

The present invention provides such was made in view of the current situation, it aims to provide a method of manufacturing reduced and the internal resistance of lithium ion secondary batteries that increase is suppressed in the discharge capacity due to repeated charging and discharging And

｛Ｍは、遷移金属、周期律表のIII族、IV族、又はV族元素、ｂは１〜３、ｍは１〜４、ｎは０〜８、ｑは０又は１をそれぞれ表し、Ｒ¹は、Ｃ₁〜Ｃ₁₀のアルキレン、Ｃ₁〜Ｃ₁₀のハロゲン化アルキレン、Ｃ₆〜Ｃ₂₀のアリーレン、又はＣ₆〜Ｃ₂₀のハロゲン化アリーレン（これらのアルキレン及びアリーレンはその構造中に置換基、ヘテロ原子を持ってもよく、またｍ個存在するＲ¹はそれぞれが結合してもよい。）、Ｒ²は、ハロゲン、Ｃ₁〜Ｃ₁₀のアルキル、Ｃ₁〜Ｃ₁₀のハロゲン化アルキル、Ｃ₆〜Ｃ₂₀のアリール、Ｃ₆〜Ｃ₂₀のハロゲン化アリール、又はＸ³Ｒ³（これらのアルキル及びアリールはその構造中に置換基、ヘテロ原子を持ってもよく、またｎ個存在するＲ²はそれぞれが結合して環を形成してもよい。）、Ｘ¹、Ｘ²、Ｘ³は、Ｏ、Ｓ、又はＮＲ⁴、Ｒ³、Ｒ⁴は、それぞれが独立で、水素、Ｃ₁〜Ｃ₁₀のアルキル、Ｃ₁〜Ｃ₁₀のハロゲン化アルキル、Ｃ₆〜Ｃ₂₀のアリール、Ｃ₆〜Ｃ₂₀のハロゲン化アリールをそれぞれ示す（これらのアルキル及びアリールはその構造中に置換基、ヘテロ原子を持ってもよく、また複数個存在するＲ³、Ｒ⁴はそれぞれが結合して環を形成してもよい。）。｝ A positive electrode active material comprising a composite oxide containing Lithium and transition metals, and the negative electrode active material made of a carbon material, a lithium ion secondary battery and a nonaqueous electrolyte containing LiPF6, the non-aqueous electrolyte The liquid is preferably a lithium ion secondary battery containing an anion compound represented by the following general formula (1) and a carbonate.

{M is a transition metal, group III, group IV, or group V element in the periodic table, b is 1 to 3, m is 1 to 4, n is 0 to 8, q is 0 or 1; ¹ is C ₁ -C ₁₀ alkylene, C ₁ -C ₁₀ halogenated alkylene, C ₆ -C ₂₀ arylene, or C ₆ -C ₂₀ halogenated arylene (these alkylene and arylene are in the structure) R ¹ may have a substituent, a hetero atom, or m may be bonded to each other.), R ² is halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ halogen Alkyl, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ (these alkyls and aryls may have substituents, heteroatoms in their structure, and n pieces R ² each may combine with each other to form a ring ^{present.), X 1, X 2} , ^3, O, S, or NR ^4, R ^3, R ⁴ are, each independently, hydrogen, alkyl of C ₁ -C _10, alkyl halide C ₁ -C _10, aryl of C ₆ -C ₂₀ , C _{6 to} C ₂₀ each represents an aryl halide (these alkyls and aryls may have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ may be bonded to each other). To form a ring). }

In the above-described lithium ion secondary battery, a nonaqueous electrolytic solution containing a carbonate in addition to the anionic compound represented by the general formula (1) is used as the nonaqueous electrolytic solution. By using a nonaqueous electrolytic solution containing a carbonate ester, a carbonate ester-derived film can be formed on the surface of the carbon material that is the negative electrode active material. Due to the presence of this film, reductive decomposition of the anion compound represented by the general formula (1) can be suppressed. Thereby, the anion compound represented by the general formula (1) can appropriately capture a small amount of water mixed in the non-aqueous electrolyte and hydrofluoric acid generated in the non-aqueous electrolyte. Corrosion and elution reaction of substances can be suppressed. Therefore, in the above-described lithium ion secondary battery, a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge are suppressed.

  Here, the ligand part of the anion compound (ionic metal complex) represented by the general formula (1) will be described. Hereinafter, in the present specification, an organic or inorganic part bonded to M in the general formula (1) is referred to as a ligand.

R ¹ in general formula (1) is selected from C ₁ -C ₁₀ alkylene, C ₁ -C ₁₀ halogenated alkylene, C ₆ -C ₂₀ arylene, or C ₆ -C ₂₀ halogenated arylene. It consists of things. These alkylene and arylene may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen on alkylene and arylene, halogen, chain or cyclic alkyl group, aryl group, alkenyl group, alkoxy group, aryloxy group, sulfonyl group, amino group, cyano group, carbonyl group, acyl Examples thereof include a group, an amide group, a hydroxyl group, and a structure in which nitrogen, sulfur, or oxygen is introduced instead of carbon on alkylene and arylene. Furthermore, when a plurality of R ¹ are present (when q = 1 and m = 2 to 4), each may be bonded, and examples thereof include a ligand such as ethylenediaminetetraacetic acid.

R ² is selected from halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ It consists of things. Similarly to R ¹ , alkyl or aryl may have a substituent or a hetero atom in its structure. Also (if n = 2 to 8) when R ² there are a plurality, R ² may be each bonded to form a ring.
Preferably, R ² is an electron-withdrawing group, particularly fluorine. In this case, the solubility and dissociation degree of the salt of the anionic compound can be improved, and the effect of improving the ionic conductivity can be obtained. Furthermore, in this case, the oxidation resistance is improved, thereby preventing the occurrence of side reactions.

X ¹ , X ² , and X ³ are each independently O, S, or NR ⁴ , and the ligand is bonded to M through these heteroatoms. Here, it is not impossible to combine other than O, S, and N, but the synthesis becomes very complicated. As a feature of the compound represented by the general formula (1), there is a bond between X ¹ and M by X ² in the same ligand, and these ligands form a chelate structure with M. . The constant q in this ligand is 0 or 1. In the case of q = 0, the chelate ring becomes a five-membered ring and the complex structure of the anionic compound is stabilized, so that side reactions can be prevented from occurring.

R ³ and R ⁴ are each independently hydrogen, C _{1 to} C ₁₀ alkyl, C _{1 to} C ₁₀ alkyl halide, C _{6 to} C ₂₀ aryl, or C _{6 to} C ₂₀ aryl halide. These alkyls and aryls may have a substituent or a heteroatom in the structure, and when a plurality of R ³ and R ⁴ are present, they may be bonded to form a ring. Good.

The constants m and n related to the number of ligands described above are determined by the type of M at the center, and m is 1 to 4 and n is 0 to 8.
It in ^{R 1, R 2, R 3} , R 4 described above, C ₁ -C ₁₀ indicates 1 to 10 carbon atoms, C ₆ -C ₂₀ is 6 to 20 carbon atoms Indicates.

In addition, it is preferable to use 1 or more types of compounds represented by following formula (2)-(5) as an anion compound represented by General formula (1). By using these anionic compounds, the solubility and dissociation degree of the salt of the anionic compound can be improved, and the ionic conductivity of the nonaqueous electrolytic solution can be improved. Furthermore, oxidation resistance can be improved.

Moreover, it is preferable to use vinylene carbonate or vinyl ethylene carbonate as the carbonate ester.
Examples of the carbon material constituting the negative electrode active material include natural graphite, artificial graphite (such as mesocarbon microbeads), and non-graphitizable carbon material.

  Moreover, an aprotic organic solvent can be used as the solvent of the nonaqueous electrolytic solution. As such an organic solvent, for example, a mixed solvent composed of one or more selected from cyclic carbonates, chain carbonates, cyclic esters, cyclic ethers, chain ethers and the like can be used.

  Here, examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of the cyclic ester include gamma butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of the chain ether include dimethoxyethane and ethylene glycol dimethyl ether. As the organic solvent, any one of these can be used alone, or two or more kinds can be mixed and used.

  Furthermore, the lithium ion secondary battery may be a lithium ion secondary battery in which 30 mol% or more of the transition metal contained in the positive electrode active material is Mn.

In the above-described lithium ion secondary battery, 30 mol% or more of the transition metal contained in the positive electrode active material is Mn. Mn is cheaper than Co and Ni. Therefore, the above-described lithium ion secondary battery in which 30 mol% or more of the transition metal contained in the positive electrode active material is Mn is inexpensive.

  By the way, compared with Co and Ni, Mn reacts with a small amount of water mixed in the non-aqueous electrolyte or hydrofluoric acid generated in the non-aqueous electrolyte and is easily eluted in the electrolyte. For this reason, in the conventional lithium ion secondary battery, when 30 mol% or more of the transition metal contained in the positive electrode active material is Mn, the discharge capacity is remarkably reduced and the internal resistance is increased with the elution of Mn. There was a problem.

On the other hand, in the above-described lithium ion secondary battery, as described above, since the nonaqueous electrolytic solution containing the anion compound represented by the general formula (1) and the carbonate is used, Mn and moisture or The reaction with hydrofluoric acid can be suppressed, and Mn can be prevented from eluting into the non-aqueous electrolyte. Therefore, the above-described lithium ion secondary battery is an inexpensive lithium ion secondary battery in which a decrease in discharge capacity and an increase in internal resistance are suppressed.

Furthermore, in any of the above lithium ion secondary batteries, the non-aqueous electrolyte contains 0.1 to 30 mol% of the anion compound represented by the general formula (1) with respect to PF ⁶⁻ ions. A lithium ion secondary battery is preferable.

By containing 0.1 mol% or more of the anion compound represented by the general formula (1) with respect to PF ⁶⁻ ions, corrosion of the positive electrode active material can be appropriately suppressed. In addition, by suppressing the anion compound represented by the general formula (1) to 30 mol% or less with respect to PF ⁶⁻ ions, it is possible to suppress deterioration in battery characteristics (such as decrease in charge / discharge efficiency and increase in internal resistance). Can do.

  Furthermore, in any of the above lithium ion secondary batteries, the non-aqueous electrolyte may be a lithium ion secondary battery containing 0.01 to 5 mol% of the carbonate ester.

  By containing 0.01 mol% or more of carbonate in the non-aqueous electrolyte, a carbonate-derived film can be appropriately formed on the surface of the carbon material that is the negative electrode active material. Thereby, reductive decomposition of the anion compound represented by the general formula (1) can be appropriately suppressed.

By the way, as the carbonate ester content in the non-aqueous electrolyte is increased from 0.01 mol%, the carbonate ester-derived film formed on the surface of the carbon material that is the negative electrode active material becomes thicker. It can be expected to enhance the effect of suppressing the reductive decomposition of the anion compound represented by (1). However, if the carbonic acid ester-derived film is too thick, the internal resistance of the battery increases, and the output characteristics deteriorate. On the other hand, in the above-described lithium ion secondary battery, the carbonate ester contained in the non-aqueous electrolyte is suppressed to 5 mol% or less. Thereby, an increase in the internal resistance of the battery can be suppressed and the output characteristics of the battery can be kept good.

  Furthermore, in the above lithium ion secondary battery, the non-aqueous electrolyte may be a lithium ion secondary battery containing 0.1 to 1 mol% of the carbonate ester.

  By containing 0.1 mol% or more of carbonate in the non-aqueous electrolyte, a carbonate-derived film can be sufficiently formed on the surface of the carbon material that is the negative electrode active material. Thereby, reductive decomposition of the anion compound represented by the general formula (1) can be sufficiently suppressed. Moreover, by suppressing the carbonic acid ester contained in the nonaqueous electrolytic solution to 1 mol% or less, it is possible to sufficiently suppress the increase in the internal resistance of the battery and to keep the battery output characteristics favorable.

Preferably, in any one of the aforementioned lithium ion secondary battery, the positive electrode active material, a spinel structure _{Li (Mn 2-x M x} ) O 4 (M is, Ni, Co, Al, Ti , Cr, Fe , Zn, Mg, Li, and a lithium ion secondary battery including 0 ≦ x ≦ 0.5) as a main component.

Alternatively, in any one of the lithium ion secondary batteries, the positive electrode active material may be a layered structure of LiNi _{0.3 + x} Mn _{0.3 + y} Co _0.4-xy O ₂ (0 ≦ x ≦ 0.4, 0 ≦ y It is preferable to use a lithium ion secondary battery containing ≦ 0.4) as a main component.

Alternatively, in any one of the lithium ion secondary batteries, the positive electrode active material is mainly composed of a layered structure of LiNi _{0.5 + z} Mn _0.5-z O ₂ (−0.05 ≦ z ≦ 0.2). A lithium ion secondary battery is preferably included.

  Each of the composite oxides represented by the above composition formula is a positive electrode active material in which 30 mol% or more of the transition metal contained in the composite oxide (positive electrode active material) is Mn. Therefore, the lithium ion secondary battery can be made inexpensive by using any of these composite oxides as the main component of the positive electrode active material.

One embodiment of the present invention is a lithium ion secondary battery including a positive electrode active material made of a composite oxide containing lithium and a transition metal, a negative electrode active material made of a carbon material, and a nonaqueous electrolyte solution containing LiPF _6. The non-aqueous electrolyte includes a lithium ion dihydrate containing any one of anionic compounds represented by the following formulas (2) to (5) and 0.01 to 5 mol% of vinylene carbonate or vinyl ethylene carbonate. A method for producing a secondary battery, comprising: an initial charging step for performing initial charging on a battery having the positive electrode active material and the negative electrode active material until a voltage of the battery reaches an upper limit voltage value, among the voltage of the battery from the start of the initial charging period leading up to the upper limit voltage value, at least vinylene carbonate Natick the voltage of the battery is included in the non-aqueous electrolyte solution Or duration of up to the decomposition voltage of the vinyl ethylene carbonate, the equation (2) to (5) without including represented by anion compound, the first non containing the LiPF ₆ and the vinylene carbonate or vinyl ethylene carbonate This is a method for manufacturing a lithium ion secondary battery in which the battery is charged in a state where a water electrolyte is contained in the battery.

An anionic compound represented by the general formula (1) (for example, a compound represented by the formulas (2) to (5)) undergoes reductive decomposition at a lower voltage than a carbonate (for example, vinylene carbonate or vinyl ethylene carbonate). . For this reason, when the lithium ion secondary battery in which the non-aqueous electrolyte containing the anion compound represented by the general formula (1) and the carbonate ester is initially charged is charged, the negative electrode active material (carbon material) is decomposed by the decomposition of the carbonate ester. By the time a carbonic ester-derived film is formed on the surface, reductive decomposition of the anionic compound represented by the general formula (1) proceeds. Therefore, in the lithium ion secondary battery manufactured by performing the initial charging as described above, the anion compound represented by the general formula (1) is generated in the water mixed in the non-aqueous electrolyte or in the non-aqueous electrolyte. There was a possibility that hydrofluoric acid could not be sufficiently captured. For this reason, there exists a possibility that the fall of discharge capacity and the raise of internal resistance accompanying the repetition of charging / discharging of a lithium ion secondary battery cannot fully be suppressed.

On the other hand, in the production method of the present invention, in the initial charging step, the battery voltage is carbonate ester (specifically, vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte) at least from the start of the initial charging. In the period up to the decomposition voltage value, the vinylene is not contained without containing the anion compound represented by the general formula (1) (specifically, any one of the compounds represented by the formulas (2) to (5)). The battery is charged with the first non-aqueous electrolyte containing carbonate or vinyl ethylene carbonate and LiPF ₆ contained in the battery. That is, the non-aqueous electrolyte solution contains the first non-aqueous electrolyte solution containing vinylene carbonate or vinyl ethylene carbonate and LiPF ₆ without containing the anion compounds represented by the formulas (2) to (5) , and the formula (2). ) To (5) and the second non-aqueous electrolyte containing the anionic compound, and at least until the battery voltage reaches the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate , the first non-aqueous electrolyte and the second non-aqueous electrolyte The battery is charged with only the first nonaqueous electrolyte contained in the two nonaqueous electrolytes. Thereby, the film derived from carbonate ester can be appropriately formed on the surface of the negative electrode active material (carbon material).

Then, if the 2nd non-aqueous electrolyte containing any one of the anion compound represented by Formula (2)-(5) is inject | poured in a battery, the anion compound represented by Formula (2)-(5) Can be suppressed. Specifically, when the second non-aqueous electrolyte is injected, a coating derived from vinylene carbonate or vinyl ethylene carbonate is already formed on the surface of the negative electrode active material (carbon material). Even if the battery is charged and discharged after the injection of the electrolytic solution, reductive decomposition of the anion compounds represented by the formulas (2) to (5) can be suppressed. Thereby, by any one of the anion compounds represented by the formulas (2) to (5) , a small amount of water mixed in the non-aqueous electrolyte or hydrofluoric acid generated in the non-aqueous electrolyte is appropriately captured. Therefore, corrosion and elution reaction of the positive electrode active material can be suppressed.

As mentioned above, according to the manufacturing method of this invention, the lithium ion secondary battery by which the fall of the discharge capacity accompanying the repetition of charging / discharging and the raise of internal resistance was suppressed can be manufactured.
The decomposition voltage value of the carbonate ester is a value determined based on the type of the lithium ion secondary battery (a combination of the positive electrode active material and the negative electrode active material, the type of carbonate ester, etc.). Therefore, although the decomposition voltage value of the carbonate ester varies depending on the type of the lithium ion secondary battery, both values are in the range of 2.5V to 3.0V.

In addition, in the period from the start of the initial charging until the battery voltage reaches the upper limit voltage value, at least the voltage of the battery is equal to the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte. `` Period until '' is any period as long as the battery voltage is equal to or longer than the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte after starting the initial charging. good. Specifically, for example, the battery voltage may reach the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte after starting the initial charging, or after starting the initial charging. It may be until the battery voltage reaches the upper limit voltage value (that is, the entire initial charging period).

Furthermore, in the method for manufacturing the lithium ion secondary battery, the initial charging step is a state in which the first non-aqueous electrolyte is accommodated in the battery until the voltage of the battery reaches the upper limit voltage value. A second non-aqueous electrolyte containing any one of the anion compounds represented by the formulas (2) to (5) in the battery that has been initially charged after the initial charging step. Preferably, the method of manufacturing a lithium ion secondary battery includes a step of injecting.

In the production method of the present invention, the first non-aqueous electrolyte containing vinylene carbonate or vinyl ethylene carbonate and LiPF ₆ is contained in the battery without containing the anion compounds represented by the formulas (2) to (5). , Perform initial charging of the battery. Thereby, the film derived from carbonate ester can be appropriately formed on the surface of the negative electrode active material (carbon material).

Then, the 2nd nonaqueous electrolyte solution containing the anion compound represented by Formula (2)-(5) is inject | poured in a battery. At this time, since a film derived from a carbonate ester has already been formed on the surface of the negative electrode active material (carbon material), even if the battery is charged / discharged after the second non-aqueous electrolyte is injected, the formula (2) The reductive decomposition of the anionic compounds represented by (5) to (5) can be suppressed. Thereby, the anion compound represented by the formulas (2) to (5) can appropriately capture a small amount of water mixed in the non-aqueous electrolyte and hydrofluoric acid generated in the non-aqueous electrolyte. In addition, corrosion and elution reaction of the positive electrode active material can be suppressed.

Furthermore, in the method for manufacturing the lithium ion secondary battery, the initial charging step is performed by setting the voltage of the battery to a decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte for a predetermined time. It is preferable to use a method for manufacturing a lithium ion secondary battery that is maintained at a high level.

In the initial charging process, the battery voltage, the predetermined time period, by keeping the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the nonaqueous electrolyte solution, vinylene carbonate or vinyl ethylene carbonate in the first non-aqueous electrolyte By sufficiently decomposing, a film derived from vinylene carbonate or vinyl ethylene carbonate can be sufficiently formed on the surface of the negative electrode active material (carbon material).

The “predetermined time” for maintaining the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte is preferably at least 1 hour. Keeping the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte for 1 hour or longer (for example, 2 hours), the vinylene carbonate or vinyl ethylene carbonate decomposition reaction proceeds sufficiently. Can do.
In addition, as a method of keeping the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate for a predetermined time, for example, during the charging, the battery voltage value of vinylene carbonate or vinyl ethylene carbonate is changed for a predetermined time (for example, 2 hours). A method of maintaining the decomposition voltage value (for example, 2.8 V) can be given.

Also provided is a method of preparing the lithium ion secondary battery, the initial charging step, in a state where the first non-aqueous electrolyte was accommodated in the battery, at least the said nonaqueous electrolyte battery voltage A first charging step of charging until reaching a decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained therein, and after the first charging step, the battery is represented by the formulas (2) to (5). A second charging step of charging the battery until the voltage of the battery reaches the upper limit voltage value after injecting the second non-aqueous electrolyte containing any one of the anionic compounds. A manufacturing method is preferable.

In the manufacturing method of the present invention, the initial charging step is divided into a first charging step and a second charging step. Furthermore, the non-aqueous electrolyte solution includes a first non-aqueous electrolyte solution containing vinylene carbonate or vinyl ethylene carbonate and LiPF ₆ without containing an anion compound represented by the formulas (2) to (5) , and a formula (2) It divides into the 2nd non-aqueous electrolyte solution containing the anion compound represented by- (5) .

First, in the first charging step, at least the voltage of the battery is included in the non-aqueous electrolyte of the battery in which only the first non-aqueous electrolyte is injected among the first non-aqueous electrolyte and the second non-aqueous electrolyte. Charge until the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate is reached. Thereby, in a 1st charge process, the film derived from vinylene carbonate or vinyl ethylene carbonate can be appropriately formed in the surface of a negative electrode active material (carbon material).

“At least the voltage of the battery is charged until the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte ” means that the battery voltage is vinylene carbonate contained in the non-aqueous electrolyte. Or it means charging (performing the first charging step) until reaching a voltage value that is greater than or equal to the decomposition voltage value of vinyl ethylene carbonate and less than the upper limit voltage value. That is, in the first charging step, the battery voltage may be stopped at the decomposition voltage value (for example, 2.8 V) of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte , or vinylene carbonate or vinyl ethylene carbonate . You may charge to the voltage value (for example, 3.5V) exceeding a decomposition voltage value.

Then, in the second charging step, after injecting the second non-aqueous electrolyte containing the anionic compound represented by the formulas (2) to (5) into the battery that has finished the first charging step, the voltage of the battery Until the battery reaches the upper limit voltage value. At this time, since a coating derived from vinylene carbonate or vinyl ethylene carbonate has already been formed on the surface of the negative electrode active material (carbon material), reductive decomposition of the anion compound represented by the formulas (2) to (5) is performed. The initial charge of the lithium ion secondary battery can be appropriately performed while suppressing. In the battery that has been initially charged in this way, a small amount of water mixed in the non-aqueous electrolyte or hydrofluoric acid generated in the non-aqueous electrolyte is caused by the anion compounds represented by the formulas (2) to (5). Since it can capture | acquire appropriately, corrosion and elution reaction of a positive electrode active material can be suppressed.

  As mentioned above, according to the manufacturing method of this invention, the lithium ion secondary battery by which the fall of the discharge capacity accompanying the repetition of charging / discharging and the raise of internal resistance was suppressed can be manufactured.

Furthermore, in the method of manufacturing a lithium ion secondary battery, the first charging step is configured to reduce the voltage of the battery for a predetermined time, the decomposition voltage of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte. It is preferable to use a method for manufacturing a lithium ion secondary battery that maintains the value.

In the first charging step, the battery voltage is kept at a decomposition voltage value (for example, 2.8 V) of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte for a predetermined time. Vinylene carbonate or vinyl ethylene carbonate can be sufficiently decomposed to sufficiently form a film derived from vinylene carbonate or vinyl ethylene carbonate on the surface of the negative electrode active material (carbon material).

The “predetermined time” for keeping the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate is preferably at least 1 hour. By keeping the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate for 1 hour or longer (for example, 2 hours), the decomposition reaction of vinylene carbonate or vinyl ethylene carbonate can be sufficiently advanced.

  Furthermore, in any one of the above-described methods for manufacturing a lithium ion secondary battery, the predetermined time may be at least one hour or more.

Keeping the battery voltage at the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the nonaqueous electrolyte for at least 1 hour or more (for example, 2 hours), the vinylene carbonate or vinyl ethylene carbonate decomposition reaction proceeds sufficiently. be able to.

Furthermore, in any of the above-described methods for producing a lithium ion secondary battery, the anion compound represented by the formulas (2) to (5) is a lithium ion secondary battery added as a lithium salt of the anion compound. A manufacturing method is preferred.

By adding the anion compound represented by the formulas (2) to (5) into the electrolyte as a lithium salt of the anion compound, the anion compound was appropriately mixed in the non-aqueous electrolyte without impairing the battery characteristics. A small amount of water and hydrofluoric acid generated in the non-aqueous electrolyte can be appropriately captured.

It is a figure which shows the structure of a lithium ion secondary battery. It is a figure which shows the structure of a positive electrode plate. It is a figure which shows the structure of a negative electrode plate. It is a flowchart which shows the flow of the manufacturing method of the lithium ion secondary battery concerning Examples 1-6 . It is a flowchart which shows the flow of the manufacturing method of the lithium ion secondary battery concerning Examples 7-12 .

( Reference Example 1 )
Next, the lithium ion secondary battery 1 of the reference example 1 will be described.
As shown in FIG. 1, the lithium ion secondary battery 1 includes an electrode body 5, a nonaqueous electrolyte solution 8, and a battery case 6 that accommodates these. The battery case 6 is a 18650 type cylindrical battery case, and includes a cap 63 and an outer can 65. A gasket 59 is disposed inside the cap 63 of the battery case 6.

The electrode body 5 is a wound body obtained by winding a sheet-like positive electrode plate 2, a negative electrode plate 3, and a separator 4 into a cylindrical shape. Among these, the positive electrode plate 2 has the collector 22 which consists of aluminum foil, and the positive mix layer 21 arrange | positioned at the both surfaces, as shown in FIG. The positive electrode mixture layer 21 contains a positive electrode active material 25. In Reference Example 1 , LiMn _1.9 Al _0.1 O ₄ is used as the positive electrode active material 25.

As shown in FIG. 3, the negative electrode plate 3 includes a current collector 32 made of a copper foil, and a negative electrode mixture layer 31 disposed on both surfaces thereof. The negative electrode mixture layer 31 includes a negative electrode active material 35. In Reference Example 1 , MCMB (manufactured by Osaka Gas, graphitized mesocarbon microbeads) is used as the negative electrode active material 35.

The non-aqueous electrolyte 8 is prepared by mixing LiPF ₆ and an anion compound lithium salt (LiPF ₂ (C) in an organic solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 30:70. ₂ O ₄ ) ₂ (hereinafter also referred to as LPFO) and carbonate ester are dissolved in a total concentration of 1M.

In addition, the non-aqueous electrolyte 8 of the present Reference Example 1 has a ratio of LPFO to LiPF ₆ of 2.5 mol%. That is, the nonaqueous electrolytic solution 8 of Reference Example 1 contains 2.5 mol% of the anionic compound represented by the formula (4) with respect to PF ₆ ⁻ ions.
In addition, the nonaqueous electrolytic solution 8 of Reference Example 1 contains 0.5 mol% of carbonate. In Reference Example 1 , vinylene carbonate is used as the carbonate ester.

  As shown in FIG. 1, the positive electrode current collector lead 23 is welded to the positive electrode plate 2, and the negative electrode current collector lead 33 is welded to the negative electrode plate 3. The positive electrode current collecting lead 23 is welded to the positive electrode current collecting tab 235 arranged on the cap 63 side. Further, the negative electrode current collecting lead 33 is welded to a negative electrode current collecting tab 335 disposed on the bottom of the outer can 65.

Next, the manufacturing method of the lithium ion secondary battery 1 of the reference example 1 will be described.
First, the nonaqueous electrolytic solution 8 was produced as follows. Specifically, first, an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7, LiPF ₆ , LPFO, and vinylene carbonate are combined with a final final concentration of 1M. In addition, a nonaqueous electrolytic solution 8 was produced. In Reference Example 1 , the ratio of LPFO to LiPF ₆ is 2.5 mol%. That is, the anionic compound represented by the formula (4) is contained at 2.5 mol% with respect to PF ₆ ⁻ ions. Further, the carbonate concentration of the non-aqueous electrolyte 8 is 0.5 mol%.

Moreover, the positive electrode plate 2 was produced as follows. First, LiMn _1.9 Al _0.1 O ₄ was prepared as the positive electrode active material 25. Next, this positive electrode active material 25, carbon black as a conductive material, and polyvinylidene fluoride as a binder are mixed, and an appropriate amount of N-methyl-2-pyrrolidone is added as a dispersing agent, and dispersed to form a slurry-like positive electrode. A mixture was obtained. Note that the mixing ratio of the positive electrode active material 25, the conductive material, and the binder is, by weight ratio, positive electrode active material 25: conductive material: binder = 85: 10: 5.

Next, the positive electrode mixture obtained as described above was applied to both surfaces of a current collector 22 made of an aluminum foil having a thickness of 20 μm and dried to obtain a positive electrode mixture layer 21. Then, it densified with a roll press, cut out into the shape of width 52mm x length 450mm, and produced the sheet-like positive electrode plate 2. FIG. The amount of positive electrode active material deposited was about 7 mg / cm ² per side.

  Moreover, the negative electrode plate 3 was produced as follows. First, MCMB (manufactured by Osaka Gas, graphitized mesocarbon microbeads) was prepared as the negative electrode active material 35. Next, the negative electrode active material 35 and polyvinylidene fluoride (binder) were mixed, an appropriate amount of N-methyl-2-pyrrolidone was added as a dispersing agent, and dispersed to obtain a slurry-like negative electrode mixture. Note that the mixing ratio of the negative electrode active material 35 and the binder was, by weight, negative electrode active material 35: binder = 95: 5.

Next, the negative electrode mixture obtained as described above was applied to the surface of a current collector 32 made of a copper foil having a thickness of 10 μm and dried to obtain a negative electrode mixture layer 31. Then, it densified with the roll press, cut out in the shape of width 54mm x length 500mm, and produced the sheet-like negative electrode plate 3. FIG. In addition, the adhesion amount of the negative electrode active material was about 4 mg / cm ² per side.

  Next, the positive electrode current collector lead 23 was welded to the positive electrode plate 2 and the negative electrode current collector lead 33 was welded to the negative electrode plate 3 (see FIG. 1). Next, a cylindrical electrode body 5 was manufactured by sandwiching a polyethylene separator 4 having a width of 56 mm and a thickness of 25 μm between the positive electrode plate 2 and the negative electrode plate 3.

  Subsequently, the electrode body 5 was inserted into the outer can 65. At this time, the positive electrode current collecting lead 23 was welded to the positive electrode current collecting tab 235, and the negative electrode current collecting lead 33 was welded to the negative electrode current collecting tab 335 disposed at the bottom of the outer can 65. Next, a non-aqueous electrolyte 8 was injected into the battery case 6. Thereafter, the gasket 59 was disposed inside the cap 63, and the cap 63 was disposed in the opening of the outer can 65. Subsequently, the outer can 65 was sealed with the cap 63 by caulking the cap 63. At this time, the battery case 6 is formed by the cap 63 and the outer can 65, and the assembly of the lithium ion secondary battery is completed.

Then, initial charge etc. were performed to the lithium ion secondary battery, and the lithium ion secondary battery 1 was completed. Specifically, initial charging was performed as follows. After performing constant current charging until the battery voltage (inter-terminal voltage) reaches the upper limit voltage value of 4.3V, the current to be charged is then charged while holding the battery voltage at the upper limit voltage value of 4.3V. When the value dropped to 1/10 of the current value when starting constant voltage charging, the initial charging was terminated. In this reference example 1 , the lithium ion secondary battery 1 is initially charged after injecting the non-aqueous electrolyte 8 containing both LPFO and vinylene carbonate.

( Reference Examples 2 to 16)
Next, lithium ion secondary batteries 1 according to Reference Examples 2 to 16 were produced. In Reference Examples 2 to 16, as compared with Reference Example 1, the type of composite oxide used as the positive electrode active material 25 and / or the concentration of carbonate (vinylene carbonate) in the non-aqueous electrolyte 8 is higher. The only difference is that the rest is the same. Specific configurations of Reference Examples 2 to 16 are shown in Table 1 together with the configuration of Reference Example 1. In Table 1, the lithium salt of the anion compound represented by the formula (4) is expressed as LPFO, and the ratio of LPFO to LiPF ₆ is expressed in mol%. In addition, vinylene carbonate is expressed as VC, and the VC concentration in the nonaqueous electrolytic solution 8 is expressed in mol%.

As shown in Table 1, in Reference Example 2, LiMn _1.9 Al _0.1 O ₄ was used as the positive electrode active material 25 as in Reference Example 1, but the proportion of vinylene carbonate in the nonaqueous electrolytic solution 8 was 5 mol%. It is different. In Reference Example 2 as well, LiMn _1.9 Al _0.1 O ₄ is used as the positive electrode active material 25 as in Reference Example 1, and therefore the upper limit voltage value for initial charging or the like is 4.3V.

In Reference Examples 3 to 8, unlike Reference Example 1, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is used as the positive electrode active material 25. Furthermore, in Reference Examples 3 to 8, the proportion of vinylene carbonate in the nonaqueous electrolytic solution 8 is sequentially changed to 0.1, 0.3, 0.5, 1, 3, and 5 mol%. In Reference Examples 3 to 8, since LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is used as the positive electrode active material 25, the upper limit voltage value for initial charging or the like is set to 4.2V.

In Reference Examples 9 and 10, unlike Reference Example 1, LiMn _1.5 Ni _0.5 O ₄ is used as the positive electrode active material 25. Furthermore, in Reference Examples 9 and 10, the proportion of vinylene carbonate in the non-aqueous electrolyte 8 is sequentially changed to 0.5 and 5 mol%. In Reference Examples 9 and 10, since LiMn _1.5 Ni _0.5 O ₄ is used as the positive electrode active material 25, the upper limit voltage value for initial charging or the like is set to 4.9V.

Further, in Reference Examples 11 to 16, unlike Reference Example 1, LiNi _0.5 Mn _0.5 O ₂ is used as the positive electrode active material 25. Furthermore, in Reference Examples 11 to 16, the proportion of vinylene carbonate in the nonaqueous electrolytic solution 8 is sequentially changed to 0.1, 0.3, 0.5, 1, 3, 5 mol%. In Reference Examples 11 to 16, since LiNi _0.5 Mn _0.5 O ₂ is used as the positive electrode active material 25, the upper limit voltage value for initial charging or the like is set to 4.2V.

(Comparative Examples 1-12)
For comparison with the lithium ion secondary batteries 1 of Reference Examples 1 to 16, lithium ion secondary batteries according to Comparative Examples 1 to 12 were prepared. In Comparative Examples 1 to 12, compared with Reference Examples 1 to 16, the type of composite oxide used as the positive electrode active material, the ratio of LPFO to LiPF ₆ , and the concentration of vinylene carbonate in the non-aqueous electrolyte are different. Only the others are the same. Table 2 shows specific configurations of Comparative Examples 1 to 12.

In Comparative Examples 1 and 2, as in Reference Examples 1 and 2, LiMn _1.9 Al _0.1 O ₄ is used as the positive electrode active material. However, in Comparative Example 1, neither the LPFO nor vinylene carbonate is contained in the nonaqueous electrolytic solution. Moreover, in the comparative example 2, although the ratio of LPFO is contained in the ratio similar to the reference examples 1 and 2, vinylene carbonate is not contained.

In Comparative Examples 3 to 6, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is used as the positive electrode active material, as in Reference Examples 3 to 8. However, in Comparative Example 3, neither LPFO nor vinylene carbonate is contained in the nonaqueous electrolytic solution. In Comparative Examples 4 and 5, LPFO is not contained in the nonaqueous electrolytic solution, but vinylene carbonate is contained at 0.5 and 5 mol%. Moreover, in the comparative example 6, although the ratio of LPFO is contained in the ratio similar to the reference examples 3-8, vinylene carbonate is not contained.

In Comparative Examples 7 and 8, as in Reference Examples 9 and 10, LiMn _1.5 Ni _0.5 O ₄ is used as the positive electrode active material. However, in Comparative Example 7, neither the LPFO nor vinylene carbonate is contained in the nonaqueous electrolytic solution. Moreover, in the comparative example 8, although the ratio of LPFO is contained in the ratio similar to the reference examples 9 and 10, vinylene carbonate is not contained.

In Comparative Examples 9 to 12, LiNi _0.5 Mn _0.5 O ₂ is used as the positive electrode active material, as in Reference Examples 11 to 16. However, in Comparative Example 9, neither the LPFO nor vinylene carbonate is contained in the nonaqueous electrolytic solution. Moreover, in Comparative Examples 10 and 11, LPFO is not contained in the non-aqueous electrolyte, but vinylene carbonate is contained at 0.5 and 5 mol%. Moreover, in the comparative example 12, although the ratio of LPFO is included in the ratio similar to the reference examples 11-16, vinylene carbonate is not included.

(Charge / discharge cycle test)
Next, the lithium ion secondary battery 1 of Reference Examples 1 to 16 and the lithium ion secondary batteries of Comparative Examples 1 to 12 were subjected to a charge / discharge cycle test in a temperature environment of 60 ° C. Specifically, each lithium ion secondary battery was charged in a temperature environment of 60 ° C. with a constant current of a current density of ² mA / cm ² until the battery voltage reached the upper limit voltage value. Thereafter, the battery voltage was discharged to a lower limit voltage value of 3.0 V at a constant current of ² mA / cm ² . With this charging and discharging as one cycle, 500 cycles of charging / discharging cycles were performed for each lithium ion secondary battery.

The upper limit voltage value varies depending on the type of positive electrode active material contained in the lithium ion secondary battery. Specifically, in the lithium ion secondary batteries ( Reference Examples 1 and 2 and Comparative Examples 1 and 2) using LiMn _1.9 Al _0.1 O ₄ as the positive electrode active material, the upper limit voltage value is 4.3V. Further, in the battery using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material (Reference Example 3-8 and Comparative Example 3-6), and the upper limit voltage value 4.2 V. Moreover, in the battery ( Reference Examples 9 and 10 and Comparative Examples 7 and 8) using LiMn _1.5 Ni _0.5 O ₄ as the positive electrode active material, the upper limit voltage value is 4.9V. Also the battery (Reference Examples 11 to 16 and Comparative Examples 9-12) using LiNi _0.5 Mn _0.5 O ₂ as the positive electrode active material, the upper limit voltage value is set to 4.2 V.

(Capacity maintenance rate)
For each lithium ion secondary battery, the discharge capacity before the charge / discharge cycle test was taken as discharge capacity A, the discharge capacity after the charge / discharge cycle test was taken as discharge capacity B, and the capacity retention rate was calculated based on the following formula (a). . The results are shown in Tables 1 and 2.
Capacity maintenance ratio (%) = (discharge capacity B after test / discharge capacity A before test) × 100 (a)

The discharge capacity A and the discharge capacity B were calculated as follows. Specifically, for each lithium ion secondary battery in a temperature environment of 20 ° C., the battery voltage reaches from the upper limit voltage value to the lower limit voltage value of 3.0 V at a constant current of 0.2 mA / cm ^2. Discharge was performed. The discharge capacity A and the discharge capacity B were calculated by dividing the amount of discharge electricity (mAh) at this time by the weight (g) of the positive electrode active material in each lithium ion secondary battery.

(Initial resistance)
Moreover, before performing the above-mentioned charging / discharging cycle test, initial resistance (internal resistance) was calculated about each lithium ion secondary battery. Specifically, each battery is adjusted to a battery capacity of 50% (SOC 50%), and a current of 0.12A, 0.4A, 1.2A, 2.4A, 4.8A is applied for 10 seconds. The subsequent battery voltage was measured. The current and voltage passed through each battery were linearly approximated, and the initial resistance (IV resistance) was determined from the slope. The initial resistance value of each battery was calculated as a relative value when the initial resistance value of Comparative Example 1 was 1. That is, the result of the initial resistance value of each battery was expressed as a value normalized based on the initial resistance value of Comparative Example 1. The results are shown in Tables 1 and 2.

(Resistance increase rate)
Moreover, the internal resistance value (IV resistance value) of each lithium ion secondary battery was calculated in the same manner as the initial resistance value after the charge / discharge cycle test.
Then, for each lithium ion secondary battery, the resistance increase rate (%) is calculated based on the following formula (b), where the initial resistance value is the resistance value X and the resistance value after the charge / discharge cycle test is the resistance value Y. did. The results are shown in Tables 1 and 2.
Resistance increase rate (%) = {(resistance value Y−resistance value X) / resistance value X} × 100 (b)

Here, the results of each lithium ion secondary battery are compared and examined.
First, the results of the batteries of Reference Examples 3 to 8 and the batteries of Comparative Examples 3 to 6 are compared. These batteries are all batteries using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material.
The results of Comparative Examples 3 to 5 in which LPFO is not contained in the nonaqueous electrolytic solution will be considered. In Comparative Examples 3 and 4, the capacity retention rate was as low as 85 to 87%, and the resistance increase rate was extremely high as 120% or more. Further, in Comparative Example 5, the capacity retention rate was a good value of 91.9%, but the resistance increase rate was extremely high at 107.3%.
Further, in Comparative Example 6 in which vinylene carbonate was not contained in the nonaqueous electrolytic solution, the capacity retention rate was slightly low at 88.7%, and the resistance increase rate was extremely high at 102.6%.

In contrast, in Reference Examples 3 to 8 in which LPFO (specifically, an anion compound represented by the formula (4)) and vinylene carbonate were added to the non-aqueous electrolyte, the capacity retention rate was 91%. A good value was exhibited, and the resistance increase rate was as small as 71% or less. From this result, by using a non-aqueous electrolyte containing both LPFO (specifically, an anionic compound represented by formula (4)) and vinylene carbonate, the reduction in discharge capacity and the internal resistance due to repeated charge and discharge. It can be said that the rise of the can be suppressed.

This is considered to be due to the following reasons. By using a nonaqueous electrolytic solution containing vinylene carbonate, a film derived from vinylene carbonate can be formed on the surface of the negative electrode active material. In particular, in Reference Examples 3 to 8, it was considered that a film derived from vinylene carbonate could be sufficiently formed on the surface of the negative electrode active material by containing 0.1 mol% or more of carbonate in the nonaqueous electrolyte. . It is considered that the presence of this coating could suppress the reductive decomposition of the anion compound represented by the formula (4). Thereby, the anion compound represented by the formula (4) appropriately captures a small amount of water mixed in the non-aqueous electrolyte and hydrofluoric acid generated in the non-aqueous electrolyte, It is thought that the elution reaction could be suppressed.

Furthermore, when comparing the initial resistances of Reference Examples 3 to 8, as shown in Table 1, in Reference Examples 3 to 6, the values were 0.81 to 0.89, which was smaller than that of Comparative Example 1. . On the other hand, in Reference Examples 7 and 8, they were 1.08 and 1.12, which were larger than the initial resistance value of Comparative Example 1. This difference is considered to be caused by the difference in the proportion of vinylene carbonate added to the non-aqueous electrolyte. That is, in Reference Examples 3 to 6 in which the proportion of vinylene carbonate was reduced to 0.1 to 1 mol%, the initial resistance could be reduced, but Reference Example 7 in which the proportion of vinylene carbonate was increased to 3 to 5 mol%. In 8, the initial resistance increased.

In Reference Examples 7 and 8, it is considered that the vinylene carbonate-derived film formed on the surface of the negative electrode active material became too thick due to the excessive proportion of vinylene carbonate. That is, it is considered that the thick coating on the surface of the negative electrode active material hindered the charge / discharge reaction, and the internal resistance (initial resistance) of the battery increased. On the other hand, in Reference Examples 3 to 6, it was considered that the internal resistance (initial resistance) of the battery could be reduced because a thin film derived from vinylene carbonate could be formed on the surface of the negative electrode active material.
From the above results, it can be said that the ratio of the carbonate ester in the non-aqueous electrolyte is preferably 0.1 to 1 mol%.

Next, the results of the batteries of Reference Examples 11 to 16 and the batteries of Comparative Examples 9 to 12 are compared. These batteries are all batteries using LiNi _0.5 Mn _0.5 O ₂ as a positive electrode active material. The test results of these batteries were the same as the test results of the batteries of Reference Examples 3 to 8 and Comparative Examples 3 to 6 (see Tables 1 and 2).

Specifically, in Comparative Examples 9 and 10 in which the non-aqueous electrolyte did not contain LPFO, the capacity retention rate was low and the resistance increase rate was high. In Comparative Example 11 (without LPFO), the capacity retention ratio showed a good value, but the initial resistance was extremely high and the resistance increase rate was also high.
Moreover, in Comparative Example 12 in which vinylene carbonate was not contained in the nonaqueous electrolytic solution, the capacity retention rate was low and the resistance increase rate was also high.

On the other hand, in Reference Examples 11 to 16 in which LPFO (specifically, an anion compound represented by the formula (4)) and vinylene carbonate were contained in the nonaqueous electrolytic solution, the capacity retention rate was a good value. The resistance increase rate was extremely small. From this result, by using a non-aqueous electrolyte containing both LPFO (specifically, an anionic compound represented by formula (4)) and vinylene carbonate, the reduction in discharge capacity and the internal resistance due to repeated charge and discharge. It can be said that the rise of the can be suppressed.

Furthermore, when the initial resistances of Reference Examples 11 to 16 were compared, in Reference Examples 11 to 14 in which the proportion of vinylene carbonate was reduced to 0.1 to 1 mol%, the initial resistance could be reduced. On the other hand, in Reference Examples 15 and 16 in which the proportion of vinylene carbonate was increased to 3 to 5 mol%, the initial resistance was increased. From the above results, it can be said that the ratio of the carbonate ester in the non-aqueous electrolyte is preferably 0.1 to 1 mol%.

Next, the results of the batteries of Reference Examples 1 and 2 and the batteries of Comparative Examples 1 and 2 are compared. Each of these batteries is a battery using LiMn _1.9 Al _0.1 O ₄ as a positive electrode active material. The batteries of Reference Examples 1 and 2 showed a higher capacity retention rate than the batteries of Comparative Examples 1 and 2 (see Tables 1 and 2). Furthermore, in the batteries of Reference Examples 1 and 2, the resistance increase rate could be suppressed as compared with the batteries of Comparative Examples 1 and 2. Also from this result, by using a non-aqueous electrolytic solution containing both LPFO (specifically, an anionic compound represented by formula (4)) and vinylene carbonate, the discharge capacity decreases and the internal capacity increases due to repeated charge and discharge. It can be said that an increase in resistance can be suppressed.

Further, the results of the batteries of Reference Examples 9 and 10 and the batteries of Comparative Examples 7 and 8 are compared. These batteries are all batteries using LiMn _1.5 Ni _0.5 O ₄ as the positive electrode active material. The batteries of Reference Examples 9 and 10 showed a higher capacity retention rate than the batteries of Comparative Examples 7 and 8 (see Tables 1 and 2). Furthermore, in the batteries of Reference Examples 9 and 10, the resistance increase rate could be suppressed as compared with the batteries of Comparative Examples 7 and 8. Also from this result, by using a non-aqueous electrolytic solution containing both LPFO (specifically, an anionic compound represented by formula (4)) and vinylene carbonate, the discharge capacity decreases and the internal capacity increases due to repeated charge and discharge. It can be said that an increase in resistance can be suppressed.

(Example 1 )
In Example 1 , compared with Reference Example 5, the non-aqueous electrolyte 8 was divided into a first non-aqueous electrolyte and a second non-aqueous electrolyte and injected into the battery, and only the first non-aqueous electrolyte was used. The lithium ion secondary battery 1 was manufactured in the same manner as in Reference Example 5 except that initial charging was performed in the injected state. Specifically, in Example 1 , the lithium ion secondary battery 1 was manufactured as follows. This will be described with reference to FIG.

First, to the organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7, LiPF ₆ and the same amount of vinylene carbonate as in Reference Example 5 are added, and the first non-aqueous electrolyte is added. Was made. Thereafter, as shown in FIG. 4, the battery components were assembled in the same manner as in Reference Example 5 in step S <b> 1. Then, it progressed to step S2 and inject | pouring the 1st non-aqueous electrolyte in the battery, the lithium ion secondary battery was produced. At this time, the outer can 65 is closed with the cap 63 without caulking the cap 63.

Then, it progressed to step S3 (initial charge process), and the initial charge of the lithium ion secondary battery was performed. Specifically, after performing constant current charging until the battery voltage (terminal voltage) reaches the upper limit voltage value of 4.2 V, the constant voltage charging is continued while maintaining the battery voltage at the upper limit voltage value of 4.2 V. The initial charging was terminated when the current value to be charged was reduced to 1/10 of the current value when the constant voltage charging was started. Thus, in Example 1 , unlike Reference Example 5, the first non-aqueous electrolyte containing carbonate (vinylene carbonate) and LiPF ₆ was injected without containing the anion compound represented by Formula (4). In this state, the battery is initially charged.

In the first embodiment, in the initial charging step (step S3), the battery is charged without maintaining the battery voltage at the decomposition voltage value of vinylene carbonate (specifically, 2.8 V) for a predetermined time. ing.

Next, it progressed to step S4 and the lithium ion secondary battery was discharged until the battery voltage fell to 3V. Then, it progressed to step S5 and the 2nd non-aqueous electrolyte prepared beforehand was inject | poured in the battery which performed initial charge. The second non-aqueous electrolyte is non-aqueous obtained by adding LiPF ₆ and the same amount of LPFO as in Reference Example 5 to an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7. Electrolytic solution.

In Example 1 , when the first nonaqueous electrolyte and the second nonaqueous electrolyte are combined, the nonaqueous electrolyte 8 used in Reference Example 5 is obtained. That is, in Example 1 , the nonaqueous electrolyte 8 was divided into a first nonaqueous electrolyte and a second nonaqueous electrolyte and injected into the battery, and only the first nonaqueous electrolyte was injected, Charging is in progress.

Therefore, in view of the total amount of the non-aqueous electrolyte (first non-aqueous electrolyte and second non-aqueous electrolyte) injected into the battery, the ratio of LPFO to LiPF ₆ is 2.5 mol%. That is, the anionic compound represented by the formula (4) is contained at 2.5 mol% with respect to PF ⁶⁻ ions. Further, the carbonate concentration with respect to the total amount of the non-aqueous electrolyte (first non-aqueous electrolyte and second non-aqueous electrolyte) injected into the battery is 0.5 mol%.

Next, the process proceeds to step S <b> 6, and the outer can 65 is sealed with the cap 63 by caulking the cap 63. Thus, by sealing the battery case 6, a lithium ion secondary battery 1 of the first embodiment is completed.

(Examples 2 to 6 )
Next, the lithium ion secondary battery 1 concerning Examples 2-6 was produced. In Examples 2 to 6 , compared with Example 1 , only the type of composite oxide used as the positive electrode active material and / or the concentration of carbonate (vinylene carbonate) in the non-aqueous electrolyte is different. The rest is the same. Specific configurations of Examples 2 to 6 are shown in Table 3 together with the configuration of Example 1 . In Table 3, the lithium salt of the anionic compound represented by the formula (4) is expressed as LPFO, and LiPF _{6 in the} total amount of the non-aqueous electrolyte (first non-aqueous electrolyte and second non-aqueous electrolyte). The ratio of LPFO to is shown in mol%. Further, vinylene carbonate is expressed as VC, and the VC concentration in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) is expressed in mol%.

As shown in Table 3, in Examples 2 and 3 , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material 25 as in Example 1 . However, in Examples 2 and 3 , the proportion of vinylene carbonate in the non-aqueous electrolyte is different from that in Example 1 . Specifically, the proportion of vinylene carbonate in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) is set to 3.5 mol% in order.

Therefore, in the battery of Example 2 , compared with the battery of Reference Example 7, the non-aqueous electrolyte 8 is divided into the first non-aqueous electrolyte and the second non-aqueous electrolyte and injected into the battery. The only difference is that the initial charge was performed with only the non-aqueous electrolyte injected.
Further, in the battery of Example 3 , compared with the battery of Reference Example 8, the non-aqueous electrolyte 8 was divided into a first non-aqueous electrolyte and a second non-aqueous electrolyte and injected into the battery. The only difference is that the initial charge was performed with only the non-aqueous electrolyte injected.

In Examples 4 to 6 , unlike Example 1 , LiNi _0.5 Mn _0.5 O ₂ is used as the positive electrode active material 25. Furthermore, in Examples 4 to 6 , the proportion of vinylene carbonate in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) was made different in order from 0.5, 3, and 5 mol%. ing.

Therefore, in the battery of Example 4 , compared with the battery of Reference Example 13, the nonaqueous electrolyte 8 is divided into the first nonaqueous electrolyte and the second nonaqueous electrolyte and injected into the battery. The only difference is that the initial charge was performed with only the non-aqueous electrolyte injected.
Further, in the battery of Example 5 , compared with the battery of Reference Example 15, the nonaqueous electrolyte 8 was divided into a first nonaqueous electrolyte and a second nonaqueous electrolyte and injected into the battery. The only difference is that the initial charge was performed with only the non-aqueous electrolyte injected.
Further, in the battery of Example 6 , compared with the battery of Reference Example 16, the nonaqueous electrolyte 8 was divided into a first nonaqueous electrolyte and a second nonaqueous electrolyte and injected into the battery. The only difference is that the initial charge was performed with only the non-aqueous electrolyte injected.

Also in Examples 2 to 6 , in the initial charging step (step S3), the battery voltage is set to a predetermined time (1 hour or more) and the decomposition voltage value of vinylene carbonate (2.8 V in the batteries of Examples 2 to 6 ). The battery is being charged without keeping it.

(Charge / discharge cycle test)
Next, the lithium ion secondary battery 1 of Examples 1 to 6 was subjected to a charge / discharge cycle test in the same manner as in Reference Examples 1 to 16.

(Capacity maintenance rate)
About each lithium ion secondary battery of Examples 1-6 , it carried out similarly to Reference Examples 1-16, and computed the capacity | capacitance maintenance factor based on Formula (a). The results are shown in Table 3.

(Initial resistance)
Moreover, before performing the above-mentioned charging / discharging cycle test, initial resistance (internal resistance) was computed about each lithium ion secondary battery of Examples 1-6 similarly to Reference Examples 1-16. In addition, the initial resistance value of each battery is calculated as a relative value when the initial resistance value of Comparative Example 1 is 1, as in Reference Examples 1-16. The results are shown in Table 3.

(Resistance increase rate)
Further, as in Reference Examples 1 to 16, for the lithium ion secondary batteries of Examples 1 to 6 , the internal resistance value (IV resistance value) of each lithium ion secondary battery before and after the charge / discharge cycle test described above was used. Based on this, the rate of increase in resistance (%) was calculated using the formula (b). The results are shown in Table 3.

Here, the results of each lithium ion secondary battery are compared and examined.
First, the results of the batteries of Examples 1 to 3 (see Table 3) and the batteries of Reference Examples 5, 7, and 8 (see Table 1) are compared. As described above, in the batteries of Examples 1 to 3 , the non-aqueous electrolyte 8 is divided into the first non-aqueous electrolyte and the second non-aqueous electrolyte as compared with the batteries of Reference Examples 5, 7, and 8. The only difference is that the initial charging is performed in a state where the first nonaqueous electrolyte is injected only into the battery.

When the test results of Example 1 (see Table 3) and Reference Example 5 (see Table 1) were compared, the capacity retention rate of Example 1 was higher than that of Reference Example 5. Further, the initial resistance values were the same, but the rate of increase in resistance was smaller in Example 1 than in Reference Example 5. That is, in the battery of Example 1 , it was possible to suppress a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge, compared to the battery of Reference Example 5.

Next, comparing the test results of Example 2 (see Table 3) and Reference Example 7 (see Table 1), the capacity retention rate was higher in Example 2 than in Reference Example 7. The initial resistance, towards the second embodiment is smaller than the reference example 7, the resistance increase rate, towards the Example 2 is smaller than the reference example 7. That is, in the battery of Example 2 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, as compared with the battery in Reference Example 7.

Further, comparing the test results of Example 3 (see Table 3) and Reference Example 8 (see Table 1), the capacity retention rate was higher in Example 3 than in Reference Example 8. Further, although the rate of increase in resistance was the same, the initial resistance value was smaller in Example 3 than in Reference Example 8. That is, in the battery of Example 3 , it was possible to suppress a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge, compared to the battery in Reference Example 8.

This is considered to be due to the following reasons. The anionic compound represented by the formula (4) undergoes reductive decomposition at a lower voltage than vinylene carbonate. Therefore, as in Reference Examples 5, 7, and 8, when the lithium ion secondary battery 1 into which the nonaqueous electrolytic solution 8 containing the anion compound represented by the formula (4) and vinylene carbonate is injected is initially charged. Then, the decomposition of the anion compound represented by the formula (4) proceeds until the film derived from the carbonate ester is formed on the surface of the negative electrode active material by the decomposition of vinylene carbonate. Therefore, in the lithium ion secondary batteries 1 of Reference Examples 5, 7, and 8, moisture mixed in the non-aqueous electrolyte and hydrofluoric acid generated in the non-aqueous electrolyte by the anion compound represented by the formula (4) It is thought that it was not able to be captured sufficiently. For this reason, it is considered that a decrease in discharge capacity and an increase in internal resistance due to repeated charging and discharging of the lithium ion secondary battery 1 could not be sufficiently suppressed.

In contrast, in Examples 1-3, the cell was injected the first non-aqueous electrolyte solution containing vinylene carbonate and LiPF ₆ without containing anion compound represented by the formula (4) was subjected to initial charging. It is considered that a film derived from vinylene carbonate was appropriately formed on the surface of the negative electrode active material (carbon material) by this initial charging.

Furthermore, in Examples 1 to 3 , the second non-aqueous electrolyte containing the anion compound represented by the formula (4) was injected into the battery that had been initially charged. At this time, since a coating derived from vinylene carbonate has already been formed on the surface of the negative electrode active material, even if the battery is charged / discharged thereafter, the reductive decomposition of the anion compound represented by formula (4) is suppressed. can do. Thus, in Examples 1 to 3 , the anion compound represented by the formula (4) appropriately captures a small amount of water mixed in the non-aqueous electrolyte and hydrofluoric acid generated in the non-aqueous electrolyte. It is thought that corrosion and elution reaction of the positive electrode active material could be suppressed.

The results of the batteries of Examples 4 to 6 (see Table 3) and the batteries of Reference Examples 13, 15, and 16 (see Table 1) are compared. As described above, in the batteries of Examples 4 to 6 , as compared with the batteries of Reference Examples 13, 15, and 16, the non-aqueous electrolyte 8 is divided into the first non-aqueous electrolyte and the second non-aqueous electrolyte. The only difference is that the initial charging is performed in a state where the first nonaqueous electrolyte is injected only into the battery.

When the test results of Example 4 (see Table 3) and Reference Example 13 (see Table 1) were compared, the capacity retention rate was higher in Example 4 than in Reference Example 13. Moreover, although the initial resistance values were the same, the rate of increase in resistance was smaller in Example 4 than in Reference Example 13. That is, in the battery of Example 4 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, compared to the battery in Reference Example 13.

Next, comparing the test results of Example 5 (see Table 3) and Reference Example 15 (see Table 1), the capacity retention rate was higher in Example 5 than in Reference Example 15. The initial resistance, towards the Example 5 is smaller than the reference example 15, the resistance increase rate, more of Example 5 is smaller than the reference example 15. That is, in the battery of Example 5 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, compared with the battery in Reference Example 15.

Further, comparing the test results of Example 6 (see Table 3) and Reference Example 16 (see Table 1), the capacity retention rate of Example 6 was higher than that of Reference Example 16. The initial resistance, better of Example 6 is smaller than the reference example 16, the resistance increase rate, towards the Example 6 is smaller than the reference example 16. That is, in the battery of Example 6 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, as compared with the battery in Reference Example 16.

From these results, the battery in which the first nonaqueous electrolyte containing vinylene carbonate and LiPF ₆ was injected without containing the anion compound represented by the formula (4) was subjected to initial charging, and then the battery that was initially charged. Injecting the 2nd non-aqueous electrolyte containing the anion compound represented by Formula (4) in the inside, and manufacturing a lithium ion secondary battery, the anion compound represented by Formula (4), vinylene carbonate As compared with the case where a lithium ion secondary battery is manufactured by performing initial charging for a battery into which a nonaqueous electrolyte solution 8 containing LiPF ₆ is injected, the reduction in discharge capacity and internal resistance due to repeated charge and discharge are further increased. It can be said that the rise of the can be suppressed.

(Example 7 )
In Example 1 , the non-aqueous electrolyte 8 is divided into a first non-aqueous electrolyte and a second non-aqueous electrolyte and injected into the battery, and initial charging is performed with only the first non-aqueous electrolyte injected. It was. On the other hand, in Example 7 , the non-aqueous electrolyte 8 is the same as Example 1 in that the non-aqueous electrolyte 8 is divided into a first non-aqueous electrolyte and a second non-aqueous electrolyte and injected into the battery. The charging step includes a first charging step of charging until the battery voltage reaches a decomposition voltage value of vinylene carbonate (2.8 V) in a state where only the first non-aqueous electrolyte is injected, and then a second non-aqueous electrolyte in the battery. After the electrolyte solution is injected, the second charging step is different from the second charging step in which the battery is charged until the battery voltage reaches the upper limit voltage value (4.2 V).

Furthermore, in this Example 7 , unlike Example 1 , in the initial charging step (specifically, the first charging step), the battery voltage was changed to a predetermined time (1 hour or more, specifically 2 hours), and vinylene carbonate. The decomposition voltage value (specifically, 2.8 V) is maintained.

Next, a method for manufacturing the lithium ion secondary battery 1 according to Example 7 will be described with reference to FIG.
First, a first nonaqueous electrolytic solution was produced in the same manner as in Example 1 . Thereafter, as shown in FIG. 5, the battery components were assembled in the same manner as in Example 1 in Step T <b> 1. Then, it progressed to step T2 and inject | poured the 1st non-aqueous electrolyte in the battery, and produced the lithium ion secondary battery. At this time, the outer can 65 is closed with the cap 63 without caulking the cap 63.

  Then, it progressed to step T3 (1st charge process), and the initial charge of the lithium ion secondary battery was performed. Specifically, constant current charging is performed until the battery voltage (voltage between terminals) reaches 2.8 V at a current of 1/20 C, and then constant voltage charging while maintaining the battery voltage at 2.8 V. The battery voltage was kept at 2.8 V for 2 hours.

Next, it progressed to step T4 and the 2nd non-aqueous electrolyte similar to Example 1 was inject | poured in the battery which performed the 1st charging process. Then, it progresses to step T5 (2nd charge process), and after carrying out constant current charge until battery voltage (voltage between terminals) reaches 4.2V of upper limit voltage value, it continues and battery voltage is set to upper limit voltage value 4.2V. The initial charging was terminated when the current value to be charged decreased to 1/10 of the current value when the constant voltage charging was started.

In Example 7 , when the first nonaqueous electrolyte and the second nonaqueous electrolyte are combined, the nonaqueous electrolyte 8 used in Reference Example 5 is obtained. Therefore, in view of the total amount of the non-aqueous electrolyte (first non-aqueous electrolyte and second non-aqueous electrolyte) injected into the battery, the ratio of LPFO to LiPF ₆ is 2.5 mol%. That is, the anionic compound represented by the formula (4) is contained at 2.5 mol% with respect to PF ₆ ⁻ ions. Further, the carbonate concentration with respect to the total amount of the non-aqueous electrolyte (first non-aqueous electrolyte and second non-aqueous electrolyte) injected into the battery is 0.5 mol%.

Subsequently, it progressed to step T6 and the lithium ion secondary battery was discharged until the battery voltage fell to 3V. Then, it progressed to step T7 and the exterior can 65 was sealed with the cap 63 by giving the cap 63 a caulking process. Thereby, the battery case 6 is sealed, and the lithium ion secondary battery 1 of the present Example 7 is completed.

(Examples 8 to 12 )
Next, the lithium ion secondary battery 1 concerning Examples 8-12 was produced. In Examples 8 to 12 , compared with Example 7 , only the type of composite oxide used as the positive electrode active material and / or the concentration of carbonate (vinylene carbonate) in the non-aqueous electrolyte is different. The rest is the same. Specific configurations of Examples 8 to 12 are shown in Table 4 together with the configuration of Example 7 . In Table 4, the lithium salt of the anionic compound represented by the formula (4) is expressed as LPFO, and LiPF _{6 in the} total amount of the nonaqueous electrolyte (first nonaqueous electrolyte and second nonaqueous electrolyte). The ratio of LPFO to is shown in mol%. Further, vinylene carbonate is expressed as VC, and the VC concentration in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) is expressed in mol%.

As shown in Table 4, in Examples 8 and 9 , as in Example 7 , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the positive electrode active material 25. However, in Examples 8 and 9 , the proportion of vinylene carbonate in the non-aqueous electrolyte is different from that in Example 7 . Specifically, the proportion of vinylene carbonate in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) is set to 3.5 mol% in order.

Therefore, the battery of Example 8 differs from the battery of Example 2 only in the method of initial charging. That is, in Example 8 , unlike Example 2 , in the initial charging step (specifically, the first charging step), the battery voltage was set at a predetermined time (1 hour or more, specifically 2 hours), and vinylene carbonate was decomposed. The voltage value (specifically, 2.8 V) is maintained.

Further, the battery of Example 9 differs from the battery of Example 3 only in the method of initial charging. That is, in Example 9 , unlike Example 3 , in the initial charging step (specifically, the first charging step), the battery voltage was set at a predetermined time (1 hour or more, specifically 2 hours) for the decomposition of vinylene carbonate. The voltage value (specifically, 2.8 V) is maintained.

In Examples 10 to 12 , unlike Example 7 , LiNi _0.5 Mn _0.5 O ₂ is used as the positive electrode active material 25. Furthermore, in Examples 10 to 12 , the proportion of vinylene carbonate in the total amount of the non-aqueous electrolyte (the first non-aqueous electrolyte and the second non-aqueous electrolyte) was made different in order from 0.5, 3, and 5 mol%. ing.

Therefore, the battery of Example 10 differs from the battery of Example 4 only in the initial charging method. That is, in Example 10 , unlike Example 4 , in the initial charging step (specifically, the first charging step), the battery voltage was set at a predetermined time (1 hour or more, specifically 2 hours), and vinylene carbonate was decomposed. The voltage value (specifically, 2.8 V) is maintained.

Further, the battery of Example 11 differs from the battery of Example 5 only in the method of initial charging. That is, in Example 11 , unlike Example 5 , in the initial charging step (specifically, the first charging step), the battery voltage was set at a predetermined time (1 hour or more, specifically 2 hours), and vinylene carbonate was decomposed. The voltage value (specifically, 2.8 V) is maintained.

Further, the battery of Example 12 differs from the battery of Example 6 only in the method of initial charging. That is, in Example 12 , unlike Example 6 , in the initial charging step (specifically, the first charging step), the battery voltage was decomposed for a predetermined time (1 hour or more, specifically 2 hours) for the decomposition of vinylene carbonate. The voltage value (specifically, 2.8 V) is maintained.

(Charge / discharge cycle test)
Next, about each lithium ion secondary battery 1 of Examples 7-12 , it carried out similarly to Reference Examples 1-16 and Examples 1-6 , and performed the charging / discharging cycle test.

(Capacity maintenance rate)
About each lithium ion secondary battery of Examples 7-12 , it carried out similarly to Reference Examples 1-16 and Examples 1-6, and computed the capacity | capacitance maintenance factor based on the said Formula (a). The results are shown in Table 4.

(Initial resistance)
Moreover, before performing the above-mentioned charging / discharging cycle test, about each lithium ion secondary battery of Examples 7-12 , it is similar to Reference Examples 1-16 and Examples 1-6, and initial stage resistance (internal resistance) is set. Calculated. In addition, the initial resistance value of each battery is calculated as a relative value when the initial resistance value of Comparative Example 1 is set to 1, as in Reference Examples 1 to 16 and Examples 1 to 6 . The results are shown in Table 4.

(Resistance increase rate)
Further, as in Reference Examples 1 to 16 and Examples 1 to 6 , for each of the lithium ion secondary batteries of Examples 7 to 12 , the internal resistance value of each lithium ion secondary battery before and after the charge / discharge cycle test described above. Based on (IV resistance value), the rate of increase in resistance (%) was calculated using the formula (b). The results are shown in Table 4.

Here, the results of each lithium ion secondary battery are compared and examined.
First, the results of the batteries of Examples 7 to 9 (see Table 4) and the batteries of Examples 1 to 3 (see Table 3) are compared. As described above, the batteries of Examples 7 to 9 were compared with the batteries of Examples 1 to 3 in the initial charging step (specifically, the first charging step) by setting the battery voltage to a predetermined time (1 hour or more). , Specifically 2 hours), and the difference is that the decomposition voltage value of vinylene carbonate (specifically 2.8 V) was maintained.

When the test results of Example 7 (see Table 4) and Example 1 (see Table 3) were compared, the capacity retention rate was higher in Example 7 than in Example 1 . Moreover, although the initial resistance values were the same, the rate of increase in resistance was smaller in Example 7 than in Example 1 . That is, in the battery of Example 7 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, compared to the battery in Example 1 .

Next, comparing the test results of Example 8 (see Table 4) and Example 2 (see Table 3), the capacity retention rate was higher in Example 8 than in Example 2 . The initial resistance value becomes smaller than the example 2 towards the Example 8, the resistance increase rate, more of Example 8 is smaller than that of Example 2. That is, in the battery of Example 8 , it was possible to suppress a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge, compared to the battery of Example 2 .

Further, comparing the test results of Example 9 (see Table 4) and Example 3 (see Table 3), the capacity retention rate was higher in Example 9 than in Example 3 . The initial resistance value becomes smaller than the third embodiment more in Example 9, the resistance increase rate, more in Example 9 is smaller than that of Example 3. That is, in the battery of Example 9 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charge / discharge compared to the battery in Example 3 .

This, in Example 7-9, unlike the first to third embodiments, in the first charging step of the initial charging step (step T3), at least one hour (two hours specifically), the battery voltage, vinylene This is considered to be because the decomposition voltage value of carbonate (specifically, 2.8 V) was maintained. Thereby, in Examples 7-9 , the decomposition reaction of vinylene carbonate in the 1st nonaqueous electrolyte was fully advanced, and the film derived from vinylene carbonate was fully formed on the surface of the negative electrode active material. Conceivable. For this reason, in Examples 7-9 , the reductive decomposition of the anion compound represented by Formula (4) is suppressed, and the trace amount of water mixed in the non-aqueous electrolyte by the anion compound represented by Formula (4) It is considered that the hydrofluoric acid generated in the nonaqueous electrolyte solution was captured and the corrosion and elution reaction of the positive electrode active material could be sufficiently suppressed.

On the other hand, in Examples 1 to 3 , in the initial charging step (step S3), the battery was charged without maintaining the battery voltage at the decomposition voltage value of vinylene carbonate (2.8 V) for a predetermined time (at least 1 hour or more). It was considered that a film derived from vinylene carbonate could not be sufficiently formed on the surface of the negative electrode active material. For this reason, in the battery of Examples 1-3 , it is thought that the ability to suppress the reductive decomposition of the anion compound represented by Formula (4) was inferior to Examples 7-9 .

Further, the results of the batteries of Examples 10 to 12 (see Table 4) and the batteries of Examples 4 to 6 (see Table 3) are compared. As described above, the batteries of Examples 10 to 12 were compared with the batteries of Examples 4 to 6 in the initial charging step (specifically, the first charging step) by setting the battery voltage to a predetermined time (1 hour or more). , Specifically 2 hours), and the difference is that the decomposition voltage value of vinylene carbonate (specifically 2.8 V) was maintained.

When the test results of Example 10 (see Table 4) and Example 4 (see Table 3) were compared, the capacity retention rate of Example 10 was higher than that of Example 4 . The initial resistance value becomes smaller than the Example 4 towards the Example 10, the resistance increase rate, more of Example 10 is smaller than that of Example 4. That is, in the battery of Example 10 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charging and discharging, as compared with the battery in Example 4 .

Next, comparing the test results of Example 11 (see Table 4) and Example 5 (see Table 3), the capacity retention rate was higher in Example 11 than in Example 5 . The initial resistance value becomes smaller than the Example 5 towards the Example 11, the resistance increase rate, more of Example 11 is smaller than that of Example 5. That is, in the battery of Example 11 , it was possible to suppress the decrease in the discharge capacity and the increase in the internal resistance due to the repeated charge / discharge compared to the battery in Example 5 .

Further, when the test results of Example 12 (see Table 4) and Example 6 (see Table 3) were compared, the capacity retention rate was higher in Example 12 than in Example 6 . The initial resistance value becomes smaller than the Example 6 towards the Example 12, the resistance increase rate, towards the Example 12 is smaller than that of Example 6. That is, in the battery of Example 12 , it was possible to suppress a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge, compared to the battery of Example 6 .

  From these results, in the initial charging step (first charging step), the battery voltage is maintained at the decomposition voltage value of vinylene carbonate (specifically, 2.8 V) for at least 1 hour (specifically, 2 hours). By doing so, it can be said that the reduction in the discharge capacity and the increase in the internal resistance due to repeated charging and discharging can be further suppressed.

In the above, the present invention has been described with reference to the first to twelfth embodiments. However, the present invention is not limited to the above-described embodiments, and it can be applied as appropriate without departing from the scope of the present invention. Nor.

For example, in Example 1-12, was used vinylene carbonate as carbonate, may be used vinyl ethylene carbonate. Even if vinyl ethylene carbonate is used, a decrease in discharge capacity and an increase in internal resistance due to repeated charge / discharge can be suppressed to the same extent as when vinylene carbonate is used.

In Examples 7 to 12 , the initial charging step is divided into a first charging step and a second charging step, and in the first charging step, the battery voltage is set for a predetermined time (1 hour or more, specifically 2 hours), The decomposition voltage value of vinylene carbonate (specifically, 2.8 V) was maintained.
However, initial charging is completed with only the first non-aqueous electrolyte contained in the battery, and the battery voltage is decomposed to vinylene carbonate for a predetermined time (1 hour or more, for example, 2 hours) during the initial charging. You may make it hold | maintain to a value (specifically 2.8V). Then, after the completion of the initial charging, the second non-aqueous electrolyte may be injected into the battery that has been initially charged. Even if it does in this way, the fall of the discharge capacity accompanying the repetition of charging / discharging and the raise of internal resistance can be suppressed to the same extent as Examples 7-12 .

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode plate 3 Negative electrode plate 8 Non-aqueous electrolyte 25 Positive electrode active material 35 Negative electrode active material

Claims (6)

A lithium ion secondary battery comprising a positive electrode active material made of a composite oxide containing lithium and a transition metal, a negative electrode active material made of a carbon material, and a nonaqueous electrolyte solution containing LiPF ₆ ,
The non-aqueous electrolyte is
Any one of anionic compounds represented by the following formulas (2) to (5);
0.01-5 mol% vinylene carbonate or vinyl ethylene carbonate, and a method for producing a lithium ion secondary battery,
For the battery having the positive electrode active material and the negative electrode active material, an initial charging step of performing initial charging until the voltage of the battery reaches an upper limit voltage value,
The initial charging step is
Of the period from the start of the initial charging to the battery voltage reaching the upper limit voltage value, at least the battery voltage is the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte. The first non-aqueous electrolyte containing the vinylene carbonate or vinyl ethylene carbonate and the LiPF ₆ is contained in the battery without including the anion compound represented by the formulas (2) to (5) during the period until The manufacturing method of the lithium ion secondary battery which charges the said battery in the state which carried out.

It is a manufacturing method of the lithium ion secondary battery according to claim 1 ,
The initial charging step includes
Charging the first non-aqueous electrolyte in a state accommodated in the battery until the battery voltage reaches the upper limit voltage value;
Lithium comprising a step of injecting a second non-aqueous electrolyte containing any one of the anion compounds represented by the formulas (2) to (5) into the battery that has been initially charged after the initial charging step. A method for manufacturing an ion secondary battery. It is a manufacturing method of the lithium ion secondary battery according to claim 2 ,
The initial charging step includes
A method for producing a lithium ion secondary battery, wherein the battery voltage is maintained at a decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte for a predetermined time. It is a manufacturing method of the lithium ion secondary battery according to claim 1 ,
The initial charging step includes
First charging for charging the battery until at least the voltage of the battery reaches the decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte while the first non-aqueous electrolyte is contained in the battery. Process,
After the first charging step, after injecting a second nonaqueous electrolyte solution containing any one of the anion compounds represented by the formulas (2) to (5) into the battery, the voltage of the battery is the upper limit. And a second charging step of charging the battery until reaching a voltage value. It is a manufacturing method of the lithium ion secondary battery according to claim 4 ,
The first charging step includes
A method for producing a lithium ion secondary battery, wherein the battery voltage is maintained at a decomposition voltage value of vinylene carbonate or vinyl ethylene carbonate contained in the non-aqueous electrolyte for a predetermined time. It is a manufacturing method of the lithium ion secondary battery according to claim 3 or 5 ,
The said predetermined time is a manufacturing method of the lithium ion secondary battery which is at least 1 hour or more.

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