JP4707312B2 - Non-aqueous solvent type secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous solvent secondary battery, and more particularly to a non-aqueous solvent secondary battery excellent in initial charge / discharge efficiency, rapid discharge efficiency, and charge storage characteristics.

  With the rapid spread of portable electronic devices, the required specifications for the batteries used for them are becoming stricter year by year, and in particular, small and thin, high capacity, excellent cycle characteristics, and stable performance are required. Yes. In the field of secondary batteries, lithium non-aqueous solvent secondary batteries, which have a higher energy density than other batteries, are attracting attention. The proportion of lithium non-aqueous solvent secondary batteries accounts for a significant increase in the secondary battery market. Is shown.

  This lithium non-aqueous solvent type secondary battery includes a negative electrode in which a negative electrode active material mixture is applied in a film form on both sides of a negative electrode core (current collector) made of an elongated sheet-like copper foil and the like, and an elongated sheet-like battery A separator made of a microporous polypropylene film or the like is placed between both sides of a positive electrode core made of aluminum foil or the like and coated with a positive electrode active material mixture in the form of a film, and the negative electrode and the positive electrode are insulated from each other by the separator. In the case of a rectangular battery, the wound electrode body is further crushed to form a flat shape, and a negative electrode lead and a positive electrode lead are respectively attached to predetermined portions of the negative electrode and the positive electrode. It has the structure which connected and accommodated in the exterior of a predetermined shape.

  The non-aqueous solvent used in such a non-aqueous solvent type secondary battery needs to have a high dielectric constant in order to ionize the electrolyte, and needs to have high ionic conductivity in a wide temperature range. Therefore, carbonates such as propylene carbonate and ethylene carbonate, lactones such as γ-butyrolactone, and other organic solvents such as ethers, ketones, and esters are used. Mixed solvents such as carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are widely used, but have a problem that the battery tends to swell when left at high temperature because of its low vapor pressure.

  On the other hand, the non-aqueous solvent containing propylene carbonate (PC) has an excellent effect that the gas generation is low because the vapor pressure is high and the oxidation potential is high, so that it is difficult to decompose and the battery is difficult to swell. Since the freezing point is low, the low temperature characteristics are also excellent.

Further, negative electrodes using carbonaceous materials such as graphite and amorphous carbon as negative electrode materials are widely used because of their low cost and excellent cycle life. When the electrolytic solution is used, the capacity of the battery is reduced due to reductive decomposition of PC during charging. In particular, a high-capacity carbonaceous material (natural graphite, artificial graphite) that has been graphitized has a problem that PC is decomposed more violently and charging does not proceed well.

  Therefore, conventionally, in order to suppress the reductive decomposition of the organic solvent, various compounds are added to the non-aqueous solvent electrolyte so that the negative electrode active material does not directly react with the organic solvent. Technology for controlling the negative electrode surface coating (SEI: Solid Electrolyte Interface. Hereinafter referred to as “SEI surface coating”) is important. For example, in Patent Document 1 below, at least one selected from vinylene carbonate and derivatives thereof is added to the electrolyte solution of a non-aqueous solvent secondary battery, and these additives add the negative electrode to the negative electrode by the first charge. It is disclosed that an SEI surface coating is formed on the negative electrode active material layer before insertion of lithium so as to function as a barrier that prevents insertion of solvent molecules around lithium ions.

  For the same purpose, the following Patent Document 2 includes a non-aqueous solvent based electrolyte added with a vinyl ethylene carbonate compound as an additive, and the following Patent Document 3 includes a ketone added with the same. The following Patent Document 4 contains vinyl ethylene carbonate, and further added with at least one kind of vinylene carbonate, cyclic sulfonic acid or cyclic sulfate, and cyclic acid anhydride. Similarly, the following patent document 6 discloses the addition of a cyclic acid anhydride and a vinyl ethylene carbonate compound.

  Among these, succinic anhydride or a succinic anhydride derivative, which is one of cyclic acid anhydrides, is excellent in suppressing the reductive decomposition of PC, but the resistance of the SEI film is increased, and the charge / discharge characteristics are greatly reduced. There was a problem. Similarly, diglycolic anhydride, which is a kind of cyclic acid anhydride, is reduced preferentially over PC at the negative electrode over PC as in the case of succinic anhydride, but has a slight effect on inhibiting PC decomposition. PC decomposition could not be completely suppressed. In addition, when a large amount of these succinic anhydride or succinic anhydride derivative, diglycolic anhydride, etc. is added, the ionic conductivity of the electrolytic solution is lowered, the resistance of the SEI film is further increased, and the charge / discharge characteristics are lowered. At the same time, there has been a problem that gas generation during charging and storage becomes significant and the battery swells greatly.

JP 08-045545 A (claims, paragraphs [0009] to [0012], [0023] to [0036]) JP 2001-006729 A (claims, paragraphs [0006] to [0014]) JP 2001-202991 A (claims, paragraphs [0006] to [0009]) JP 2003-151623 A (claims, paragraphs [0008] to [0009], [0022] to [0031]) JP 2000-268859 A (claims, paragraphs [0007] to [0008]) JP 2002-352852 A (claims, paragraphs [0010] to [0013])

  As a result of repeating various studies on the generation mechanism of the above-mentioned SEI surface coating, the present inventor simultaneously added an acid anhydride and diglycolic acid anhydride represented by the following chemical formula to a nonaqueous solvent electrolyte containing PC. The reductive decomposition of PC can be satisfactorily prevented, and the impedance of the SEI surface coating is reduced, the initial charge / discharge efficiency and the rapid discharge efficiency are not reduced, and the charge storage characteristics can be further improved. I found it. The reason why such a result is obtained is not clear at present, and it is necessary to wait for further research. However, the SEI coating formed at the negative electrode interface is probably caused by the preferential reduction and decomposition of diglycolic anhydride during charging. It is presumed that the SEI film having an excellent oxygen ion concentration and an excellent lithium ion conductivity was obtained.

（ただし、ｎ＝０〜４の整数であり、Ｒ_１〜Ｒ_４は、同じであっても異なっていても良く、Ｈもしくは有機基を示す。また、Ｒ_１〜Ｒ_４は、環を形成しても良い。）

(However, n is an integer of 0 to 4, and R _{1 to} R ₄ may be the same or different, and represents H or an organic group. R _{1 to} R ₄ form a ring. You may do it.)

  Accordingly, an object of the present invention is to provide a non-aqueous solvent secondary battery excellent in initial charge / discharge efficiency, rapid discharge efficiency, and charge storage characteristics by reducing the impedance of the SEI surface coating.

The above object of the present invention can be achieved by the following configurations. That is, the invention of the non-aqueous solvent secondary battery according to claim 1 of the present application includes a positive electrode including a positive electrode material capable of reversibly occluding and releasing lithium, and a carbonaceous material capable of reversibly occluding and releasing lithium. In a non-aqueous solvent secondary battery comprising a negative electrode containing, and a non-aqueous solvent electrolyte containing propylene carbonate, in the non-aqueous solvent electrolyte,
(1) an acid anhydride represented by the following chemical formula, and (2) diglycolic anhydride,
Containing,
The content of the acid anhydride represented by the following chemical formula in the non-aqueous solvent electrolyte is 0.01 mass% or more and 10 mass% or less,
The content of diglycolic anhydride of the non-aqueous solvent system electrolytic solution state, and are less than 10 wt% 0.01 wt%,
The mass ratio of the acid anhydride and diglycolic acid anhydride represented by the following chemical formula in the non-aqueous solvent electrolyte is in the range of 1: 2 to 2: 1 .

（ただし、ｎ＝０〜４の整数であり、Ｒ_１〜Ｒ_４は、同じであっても異なっていても良く、Ｈもしくは有機基を示す。また、Ｒ_１〜Ｒ_４は、環を形成しても良い。）

(However, n is an integer of 0 to 4, and R _{1 to} R ₄ may be the same or different, and represents H or an organic group. R _{1 to} R ₄ form a ring. You may do it.)

In the acid anhydride represented by the above chemical formula, when R _{1 to} R ₄ are organic groups, those having an alkyl group, a phenyl group, a cyclohexyl group, a cyclopentyl group, a vinyl group, and an aryl group are preferably used.

The present invention is characterized in that the mass ratio of the acid anhydride and diglycolic acid anhydride represented by the chemical formula in the non-aqueous solvent electrolyte is in the range of 1: 2 to 2: 1.
This is not preferable because the content of diglycolic anhydride with respect to the acid anhydride represented by the above chemical formula is low because the resistance of the SEI film increases and the charge / discharge characteristics are greatly reduced. This is because even if the content ratio with respect to the acid anhydride represented by the chemical formula is too large, the effect of suppressing the decomposition of PC is lowered, the generation of gas during rechargeable storage becomes remarkable, and the swelling of the battery increases.
Also, the non-aqueous solvent other than PC constituting the non-aqueous solvent electrolyte (organic solvent) is carbonates, lactones, ethers, esters, and aromatic hydrocarbons and the like, carbonates among these , Lactones, ethers, ketones, esters and the like are preferable, and carbonates are more preferably used.

  Specific examples of carbonates include ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, γ-valerolactone, γ-dimethoxyethane, tetrahydrofuran, anisole, and 1,4-dioxane. In view of increasing charge and discharge efficiency, ethylene carbonate and chain carbonate are preferably used. In addition to PC, two or more of these solvents can be mixed and used.

The electrolyte constituting the non-aqueous solvent electrolyte is lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), Examples thereof include lithium salts such as lithium trifluoromethylsulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ]. Of these, LiPF ₆ and LiBF ₄ are preferably used, and the amount dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / l.

As the positive electrode active material, a lithium transition metal composite oxide represented by LixMO ₂ (where M is at least one of Co, Ni, and Mn), that is, LiCoO ₂ , LiNiO ₂ , LiNiCo _1-y O ₂ ( y = 0.01-0.99), Li _0.5 MnO ₂ , LiMnO ₂ , LiCo _x Mn _y Ni _z O ₂ (x + y + z = 1) are used singly or in combination.

  The negative electrode active material may include a carbonaceous material capable of inserting and extracting lithium, and in addition, a mixture containing at least one selected from the group consisting of a siliconaceous material and a metal oxide may be used. The graphitized carbonaceous material is preferable because it has a high capacity and the effects of the present invention are more apparent.

  The invention according to claim 2 of the present application is the nonaqueous solvent secondary battery according to claim 1, wherein the acid anhydride represented by the chemical formula is succinic anhydride, methyl succinic anhydride, anhydrous 2, 2-dimethylsuccinic acid, glutaric anhydride, 1,2-cyclohexanedicarboxylic anhydride, cis-1,2,3,6-tetrahydrophthalic anhydride, cis-5-norbornene-endo-2, 3-dicarboxylic acid, It is at least one selected from phenyl succinic anhydride, 2-phenyl glutaric anhydride, and nonenyl succinic anhydride.

  In the acid anhydrides represented by the above chemical formulas, succinic anhydride is particularly preferable, and two or more kinds can be used in combination.

The invention according to claim 3 of the present application is the nonaqueous solvent secondary battery according to claim 1 , wherein the content of the acid anhydride represented by the chemical formula in the nonaqueous solvent electrolyte is 0.0 you wherein a 5% by mass to 5% by mass or more.

  When the content of the acid anhydride represented by the chemical formula is less than 0.01% by mass, the effect of addition of the acid anhydride represented by the chemical formula is not substantially recognized, and 10% by mass is added. Even if it exceeds, the dissolution amount of the electrolyte is reduced by that amount, the electrolyte concentration is lowered, and the electric conductivity of the nonaqueous solvent electrolyte is decreased, which is not preferable. More preferably, the content of the acid anhydride represented by the chemical formula is in the range of 0.05% by mass or more and 5% by mass or less in the non-aqueous solvent electrolyte.

In the invention, in the non-aqueous solvent secondary battery according to claim 1, content 0.0 5 mass of diglycolic anhydride of the nonaqueous solvent electrolyte solution according to claim 4 of the present application you wherein the percent 5 mass% or less.

  If the content of diglycolic anhydride in the non-aqueous solvent electrolyte is less than 0.01% by mass, an SEI film cannot be formed. This is not preferable because the ionic conductivity is reduced. More preferably, the content of diglycolic anhydride in the non-aqueous solvent electrolyte is 0.05% by mass or more and 5% by mass or less.

The invention according to claim 5 of the present application is the nonaqueous solvent secondary battery according to claim 1, wherein the content of propylene carbonate in the nonaqueous solvent electrolyte is 2 mass% or more and 65 mass%. The invention according to claim 6 is the nonaqueous solvent secondary battery according to claim 5 , wherein the content of propylene carbonate in the nonaqueous solvent electrolyte is 3 mass. % Or more and 60% by mass or less.

  When the PC content in the non-aqueous solvent electrolyte is less than 2% by mass, the boiling point of the electrolyte decreases, so the volatilization amount of the gas increases and the effect of suppressing the swelling of the battery decreases. If the PC content in the system electrolyte exceeds 65% by mass, the viscosity of the electrolyte increases and the rapid charge / discharge characteristics deteriorate. More preferably, the PC content in the non-aqueous solvent electrolyte is 3% by mass or more and 60% by mass or less.

The invention according to claim 7 of the present application is characterized in that, in the nonaqueous solvent secondary battery according to claim 1, the nonaqueous solvent electrolyte is gelled.

  When the electrolytic solution is gelled, the polymer component adheres to the surface of the negative electrode active material, so the resistance of the SEI film that usually occurs at the negative electrode interface increases, and the nonaqueous solvent secondary battery using a liquid electrolyte The resistance increase effect due to this gelation is caused by the addition of the acid anhydride represented by the above chemical formula and diglycolic anhydride to the nonaqueous solvent electrolyte containing PC. Since this cancels out the resistance lowering effect of the coating, a gelled non-aqueous solvent secondary battery having good characteristics can be obtained.

  Examples of the polymer that holds the electrolytic solution in the gel electrolyte include polymers such as an alkylene oxide polymer and a fluorine polymer such as a polyvinylidene fluoride-hexafluoropropylene copolymer. A method for forming a gel electrolyte using such a polymer material can be obtained by immersing the electrolytic solution in a polymer such as an isocyanate cross-linked product of polyethylene oxide, polypropylene oxide, or polyalkylene oxide.

  In addition, a method of subjecting an electrolytic solution containing a polymerizable gelling agent to a polymerization treatment such as ultraviolet curing or thermosetting, or a method of cooling a solution obtained by dissolving a polymer that forms a gel electrolyte at room temperature at a high temperature. Are also preferably used. When using a polymerizable gelling agent-containing electrolyte, examples of the polymerizable gelling agent include those having an unsaturated double bond such as acryloyl group, methacryloyl group, vinyl group, allyl group, epoxy, oxetane, Examples thereof include those having a cationic polymerizable cyclic ether group such as formal.

  Specifically, acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, ethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N, N- Diethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, trimethylolpropane alkoxylate Monomers having unsaturated double bonds such as totriacrylate, pentaerythritol alkoxylate triacrylate, pentaerythritol alkoxylate tetraacrylate, copolymer of methyl methacrylate and (3-ethyl-3-oxetanyl) methyl acrylate (molecular weight: 400,000) And cyclic ether group-containing compounds such as tetraethylene glycol bisoxetane.

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

Polymerization of the cyclic ether group-containing compound is initiated by heat or charge / discharge by Li ⁺ or a small amount of H ⁺ in the electrolyte.

  On the other hand, in the method of cooling a polymer that forms a gel electrolyte at room temperature and dissolved in an electrolyte at a high temperature, any gel that forms a gel with respect to the electrolyte and is stable as a battery material can be used. It may be a thing. For example, polymers having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone; acrylic derivative polymers such as methyl polyacrylate and polyethyl acrylate; fluorine-based resins such as polyvinyl fluoride and polyvinylidene fluoride; polyacrylonitrile CN group-containing polymers such as polyvinylidene cyanide; polyvinyl alcohol polymers such as polyvinyl acetate and polyvinyl alcohol; halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Moreover, it can be used even if it is a mixture with said polymer | macromolecule, a modified body, a derivative, a random copolymer, a graft copolymer, a block copolymer, etc. The weight average molecular weight of these polymers is usually in the range of 10,000 to 5,000,000. When the molecular weight is low, it is difficult to form a gel. If the molecular weight is high, the viscosity becomes too high and handling becomes difficult.

In the invention according to claim 8 of the present application, in the nonaqueous solvent secondary battery according to claim 7 , the content of the electrolyte in the gelled nonaqueous solvent electrolyte is gelled. 50% by mass or more and 99.5% by mass or less with respect to the total amount of the non-aqueous solvent electrolyte solution, and the invention according to claim 9 is the same as the non-aqueous solvent system 2 according to claim 11. In the secondary battery, the content of the electrolytic solution in the gelled nonaqueous solvent electrolyte is 75% by mass or more and 99.5% by mass or less based on the total amount of the gelled nonaqueous solvent electrolyte. It is characterized by being.

  If the content of the electrolytic solution in the gelled non-aqueous solvent electrolytic solution is too small, such as less than 50% by mass, the ionic conductivity decreases and the high load discharge capacity decreases. More preferably, it is 75 mass% or more with respect to the total amount of the gel electrolyte. Furthermore, when the content of the electrolytic solution exceeds 99.5% by mass, the mechanical strength of the gelled nonaqueous solvent-based electrolytic solution cannot be obtained.

The invention according to claim 10 of the present application is the nonaqueous solvent secondary battery according to claim 1, wherein the carbon material in the negative electrode has a d-value on the lattice plane (002 plane) in X-ray diffraction. It contains carbon material which is 0.340 nm or less.

  As the crystallization of the carbonaceous material proceeds, the d value of the lattice plane (002 plane) in X-ray diffraction becomes smaller, and natural graphite and artificial graphite that have been crystallized have the d value of 0.340 nm or less. The present invention can also be applied to the case where the negative electrode contains such a highly crystallized carbonaceous material. In this case, a high-capacity nonaqueous solvent secondary battery can be obtained.

The invention according to claim 11 of the present application is characterized in that the nonaqueous solvent secondary battery according to claim 1 further includes a laminate outer package. According to such a configuration, the mass of the exterior can be reduced, and the thickness can be reduced, so that a small and light non-aqueous solvent secondary battery can be obtained.

The present invention, in a non-aqueous solvent electrolyte containing propylene carbonate,
(1) Since the acid anhydride represented by the above chemical formula and (2) diglycolic anhydride are contained, the impedance of the SEI film becomes very low even if a negative electrode containing a carbonaceous material is used. As described in detail below, a nonaqueous solvent secondary battery excellent in initial charge / discharge efficiency, rapid discharge efficiency, and charge storage characteristics can be obtained.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail using examples and comparative examples. First, a specific method for producing a nonaqueous solvent secondary battery common to the examples and comparative examples will be described. Will be described.

<Preparation of positive electrode plate>
A positive electrode active material made of LiCoO _{2 is} a carbon-based conductive agent (for example, 5% by mass) such as acetylene black and graphite, and a binder (for example, 3% by mass) made of polyvinylidene fluoride (PVdF) is N-methyl. A material dissolved in an organic solvent made of pyrrolidone is mixed to obtain an active material slurry or an active material paste. These active material slurries or active material pastes, in the case of slurry using a die coater, a doctor blade, etc., in the case of paste, a positive electrode core (for example, an aluminum foil or aluminum mesh having a thickness of 20 μm) by a roller coating method or the like The positive electrode plate which apply | coated uniformly on both surfaces and apply | coated the active material layer is formed. Thereafter, the positive electrode plate coated with the active material layer is passed through a dryer to remove and dry the organic solvent necessary for slurry or paste preparation. After drying, the positive electrode plate is rolled by a roll press. The positive electrode plate has a thickness of 0.17 mm.

<Preparation of negative electrode plate>
Negative electrode active material made of natural graphite (d (002) value = 0.335 nm)), binder (eg 3% by mass) made of polyvinylidene fluoride (PVdF), etc., organic solvent made of N-methylpyrrolidone, etc. The material dissolved in is mixed into a slurry or paste. These slurries or pastes are uniformly applied over the entire surface of the negative electrode core (for example, a copper foil having a thickness of 20 μm) by using a die coater, a doctor blade or the like in the case of slurry, or by a roller coating method in the case of paste. The negative electrode plate which apply | coated and applied the active material layer is formed. Thereafter, the negative electrode plate coated with the active material layer is passed through a drier to remove the organic solvent that was necessary when the slurry or paste was prepared, and then dried. After drying, the dried negative electrode plate is rolled by a roll press to obtain a negative electrode plate having a thickness of 0.14 mm.

<Production of electrode body>
The positive electrode plate and the negative electrode plate produced as described above are sandwiched with a microporous film (for example, a thickness of 0.025 mm) made of a polyolefin resin having low reactivity with an organic solvent and low cost, and The center lines in the width direction of each electrode plate are aligned and overlapped. Then, it winds with a winder and tapes the outermost periphery, and it is set as the spiral electrode body of an Example and a comparative example. Next, the electrode bodies produced as described above are inserted into the exterior bodies made of aluminum laminate, and the positive electrode current collecting tab and the negative electrode current collection tab extending from the electrode bodies are welded together with the exterior body.

<Preparation of electrolyte>
A nonaqueous solvent electrolyte was prepared by dissolving in a nonaqueous solvent mixed at a mass ratio described in the table at a ratio of 1.0M-LiPF ₆ . The addition ratios of acid anhydride, diglycolic anhydride and the like represented by the chemical formula are as described in the table, and all are mass ratios with respect to the mass of the nonaqueous solvent electrolyte.

<Production of battery>
Next, a necessary amount of various nonaqueous solvent electrolytes were injected from the opening of the outer package and then sealed to prepare lithium ion secondary batteries having a design capacity of 750 mAh for all of the examples and comparative examples.

( Examples 1-2 , Reference Examples 1-2 , Comparative Examples 1-3)
First, the difference in the effect by the presence or absence of addition of succinic anhydride and diglycolic anhydride was confirmed. As an electrolytic solution, LiPF ₆ was dissolved in a mixed solvent composed of ethylene carbonate (EC) / propylene carbonate (PC) / ethyl methyl carbonate (EMC) = 30/30/40 (mass ratio), and 1.0M-LiPF ₆ It was made to become. The succinic anhydride content was kept constant at 0.5% by mass, and no diglycolic anhydride was added as Comparative Example 1, and the diglycolic anhydride was added at 0.1% by mass, 0.5% by mass, Reference examples 1, Examples 1 and 2 and Reference Example 2 were added in the order of 0.0 mass% and 2.0 mass%, respectively. Furthermore, what added 1.0 mass% and 3.0 mass% of addition amounts of diglycolic anhydride without adding succinic anhydride was made into Comparative Examples 2 and 3, respectively.

<Charging / discharging conditions>
For each of the nonaqueous solvent secondary batteries of Examples 1-2, Reference Examples 1-2, and Comparative Examples 1-3 produced as described above, various charge / discharge tests were performed under the following charge / discharge conditions. Went. The ambient temperature during the charge / discharge test is 25 ° C.

<Measurement of initial discharge capacity>
First, each battery is charged with a constant current of 1 It (1 C) = 750 mA, and after the battery voltage reaches 4.2 V, it is charged with a constant voltage of 4.2 V for 3 hours. The charge capacity was determined. Thereafter, discharging was performed at a constant current of 1 It until the battery voltage reached 2.75 V, the discharge capacity at this time was determined as the initial discharge capacity, and the initial charge and discharge efficiency was determined by the following equation. The results are shown in Table 1.
Initial charge / discharge efficiency (%) = 100 × (initial discharge capacity / initial charge capacity)

<Rapid discharge ability>
For each battery whose initial charge / discharge efficiency was measured, it was charged with a constant current of 1 It = 750 mA, and after the battery voltage reached 4.2 V, it was charged with a constant voltage of 4.2 V for 3 hours, and then 0.2 It = The battery is discharged at a constant current of 150 mA until the battery voltage reaches 2.75 V to obtain a 0.2 It discharge capacity, and is charged separately at a constant current of 1 It = 750 mA with a battery of the same specification, and the battery voltage is 4.2 V. Then, the battery is charged for 3 hours at a constant voltage of 4.2 V, and then discharged until the battery voltage reaches 2.75 V at a constant current of 3 It = 2250 mA to obtain a 3 It discharge capacity. The rapid discharge efficiency (%) was determined as the rapid discharge efficiency. The results are summarized in Table 1.
Rapid discharge efficiency (%) = (3 It discharge capacity / 0.2 It discharge capacity) × 100

<Gas generation during charge storage>
Each battery whose initial charge / discharge efficiency was measured was charged with a constant current of 1 It = 750 mA, and after the battery voltage reached 4.2 V, it was charged with a constant voltage of 4.2 V for 3 hours. Each battery was then allowed to stand at 80 ° C. for 24 hours, and the generated gas was collected and the volume was measured under normal pressure. The results are summarized in Table 1.

From the results of Table 1, based on the results of the nonaqueous solvent secondary battery of Comparative Example 1 containing succinic anhydride but not containing diglycolic anhydride in the nonaqueous solvent electrolyte, The following can be understood.
(A) Examples 1 and 2 containing both succinic anhydride and diglycolic anhydride and the nonaqueous solvent secondary batteries of Reference Examples 1 and 2 are comparative examples of initial charge and discharge efficiency and rapid discharge efficiency. The rapid discharge efficiency is much superior to that of Comparative Example 1 in particular. Further, the amount of gas generated during charge storage is similar to that in Comparative Example 1.
(B) The nonaqueous solvent type secondary batteries of Comparative Examples 2 and 3 that contain only diglycolic anhydride and no succinic anhydride have significantly lower initial charge / discharge efficiency than that of Comparative Example 1. However, the rapid discharge efficiency is almost the same as those in Examples 1-2 and Reference Examples 1-2 . Further, the amount of gas generated during charge storage is larger than that described in Comparative Example 1 and Examples 1 and 2 and Reference Examples 1 and 2, and the amount of diglycolic anhydride is the highest in Comparative Example 3. The amount of gas generation is the highest.
(C) From the results of (a) to (b) above, when a non-aqueous electrolyte containing PC is used, simultaneous addition of succinic anhydride and diglycolic anhydride as an additive is effective It can be seen that it is.

(Examples 3 to 8 and Comparative Examples 4 and 5)
Next, the influence by the difference in PC content was investigated about various non-aqueous solvents. As additive content, 0.5% by mass of succinic anhydride and 0.5% by mass of diglycolic anhydride were constant, and the solvent composition ratio was changed as shown in Table 2, and Examples 3 to 8 and Comparative Example 4 were used. 8 and 5 types of non-aqueous solvent type secondary batteries were prepared, and the initial charge / discharge efficiency, the rapid discharge efficiency, and the amount of gas generated during charge storage were measured under the same conditions as described above. The electrolyte concentration is 1.0M-LiPF ₆ in all cases, and DEC represents diethyl carbonate. The results are summarized in Table 2.

From the results in Table 2, the following can be understood.
(A ′) As for the initial charge / discharge efficiency, substantially the same efficiency is obtained in any of Examples 3 to 8 and Comparative Examples 4 and 5.
(B ′) As for the rapid discharge efficiency, the results of Comparative Examples 4 and 5 having 0 or less PC content are the best, and in Examples 3 to 8 , the rapid discharge efficiency gradually deteriorates as the PC content increases. is doing.
(C ′) The amount of gas generated during storage during charging is opposite to the result of (b ′), with the results of Comparative Examples 4 and 5 having the lowest or zero PC content being the most inferior. In Examples 3 to 8 , The amount of gas generated during charge storage decreases as the content increases (Examples 3 to 6 ). However, when the PC content exceeds 40% by mass (Examples 7 and 8 ), gas generation during charge storage occurs. The amount is increasing. (D ′) From the results of (a ′) to (c ′) above, the PC content in the non-aqueous solvent is preferably 2% by mass or more and 65% by mass or less, more preferably 3% by mass or more and 60% by mass or less. It can be seen that it is.

(Examples 9 to 15 and Comparative Examples 6 and 7)
Here, the effects of differences in succinic anhydride and other compounds were investigated. As the non-aqueous solvent electrolyte, the same EC / PC / EMC = 30/30/40 (mass ratio) as in Example 7 was dissolved in a solvent mixed at a ratio of 1.0M-LiPF ₆ . I used something. As additives, 0.5% by mass of the compound shown below and 0.5% by mass of diglycolic anhydride were added to the nonaqueous solvent electrolyte solution. The compounds used are as shown below. The maleic anhydride and phthalic anhydride used as Comparative Examples 6 and 7 are not the compounds represented by the above chemical formulas, but are acid anhydrides similar to succinic anhydride.
(1) Succinic anhydride (Example 9 )
(2) Methyl succinic anhydride (Example 10 )
(3) 2,2-dimethyl succinic anhydride (Example 11 )
(4) Glutaric anhydride (Example 12 )
(5) cis-1,2,3,6-tetrahydrophthalic anhydride (Example 13 )
(6) Phenyl succinic anhydride (Example 14 )
(7) 2-Phenylglutaric anhydride (Example 15 )
(8) Maleic anhydride (Comparative Example 6)
(9) Phthalic anhydride (Comparative Example 7)

Nine types of nonaqueous solvent secondary batteries prepared using the compounds of Examples 9 to 15 and Comparative Examples 6 and 7 were prepared, and the initial charge and discharge efficiency, the rapid discharge efficiency and the charge were performed under the same conditions as described above. The amount of gas generated during storage was measured. The results are summarized in Table 3.

From the results in Table 3, the following can be understood.
(A ") The initial charge and discharge efficiencies and rapid discharge efficiencies of Examples 9 to 15 using acid anhydrides represented by the above chemical formulas are compared with Comparative Examples 6 and 7 using maleic anhydride or phthalic anhydride. Is very good.
(B ″) The amount of gas generated during storage can be regarded as substantially the same in Examples 9 to 15 and Comparative Examples 6 and 7.
(C ″) From the results of (a ″) to (b ″) above, the additive added simultaneously with diglycolic anhydride is not only succinic anhydride but also compounds represented by other chemical formulas. It turns out that there is an effect.

Considering the results of Examples 1 to 15 above, Reference Examples 1 to 2 and Comparative Examples 1 to 7 in total, in the present invention, the non-aqueous solvent electrolyte containing PC is represented by the above chemical formula. By using two types of additives, acid anhydride and diglycolic anhydride, a non-aqueous solvent with superior initial charge / discharge efficiency, rapid discharge efficiency, and gas generation during charge storage compared to the conventional one A secondary battery is obtained.

In Examples 1 to 15 and Reference Examples 1 and 2 , only examples using liquid non-aqueous solvent electrolytes were shown, but the effect of the present invention is a phenomenon caused by SEI at the negative electrode interface. Since it does not change depending on the properties of the electrolytic solution, it will be obvious to those skilled in the art that the same effect can be obtained when the non-aqueous solvent electrolytic solution is gelled.

Claims (11)

A positive electrode including a positive electrode material capable of reversibly occluding and releasing lithium, a negative electrode including a carbonaceous material capable of reversibly occluding and releasing lithium, and a non-aqueous solvent electrolyte containing propylene carbonate In water-solvent secondary batteries,
In the non-aqueous solvent electrolyte,
(1) an acid anhydride represented by the following chemical formula, and (2) diglycolic anhydride,
Containing,
The content of the acid anhydride represented by the following chemical formula in the non-aqueous solvent electrolyte is 0.01 mass% or more and 10 mass% or less,
The content of diglycolic anhydride of the non-aqueous solvent system electrolytic solution state, and are less than 10 wt% 0.01 wt%,
The non-aqueous solvent characterized in that the mass ratio of acid anhydride and diglycolic anhydride represented by the following chemical formula in the non-aqueous solvent electrolyte is in the range of 1: 2 to 2: 1. Solvent-based secondary battery.

(However, n is an integer of 0 to 4, and R _{1 to} R ₄ may be the same or different, and represents H or an organic group. R _{1 to} R ₄ form a ring. You may do it.) The acid anhydride represented by the above chemical formula is succinic anhydride, methyl succinic anhydride, 2,2-dimethyl succinic anhydride, glutaric anhydride, 1,2-cyclohexanedicarboxylic anhydride, cis-1,2,3, It is at least one selected from 6-tetrahydrophthalic acid, cis-5-norbornene-endo-2, 3-dicarboxylic acid, phenyl succinic anhydride, 2-phenyl glutaric anhydride, and nonenyl succinic anhydride The non-aqueous solvent secondary battery according to claim 1. 2. The nonaqueous solvent system according to claim 1 , wherein the content of the acid anhydride represented by the chemical formula in the nonaqueous solvent electrolyte solution is 0.05% by mass or more and 5% by mass or less. Secondary battery. 2. The non-aqueous solvent secondary battery according to claim 1 , wherein the content of diglycolic anhydride in the non-aqueous solvent electrolyte is 0.05% by mass or more and 5% by mass or less.   2. The nonaqueous solvent secondary battery according to claim 1, wherein the content of propylene carbonate in the nonaqueous solvent electrolyte is 2% by mass or more and 65% by mass or less. The non-aqueous solvent secondary battery according to claim 5 , wherein the content of propylene carbonate in the non-aqueous solvent electrolyte is 3% by mass or more and 60% by mass or less.   The nonaqueous solvent secondary battery according to claim 1, wherein the nonaqueous solvent electrolyte is gelled. The content of the electrolytic solution in the gelled non-aqueous solvent electrolyte is 50% by mass or more and 99.5% by mass or less based on the total amount of the gelled non-aqueous solvent electrolyte. The non-aqueous solvent secondary battery according to claim 7 , wherein The content of the electrolytic solution in the gelled nonaqueous solvent-based electrolyte solution is 75% by mass or more and 99.5% by mass or less based on the total amount of the gelated nonaqueous solvent electrolyte solution. The nonaqueous solvent secondary battery according to claim 8 , wherein   2. The nonaqueous solvent secondary battery according to claim 1, wherein the carbon material in the negative electrode includes a carbon material having a d-value of 0.340 nm or less in a lattice plane (002 plane) in X-ray diffraction. . The nonaqueous solvent secondary battery according to claim 1, further comprising a laminate outer package.