JP2017157400A - Nonaqueous secondary battery, gas-generation inhibitor and nonaqueous electrolyte which are used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a nonaqueous secondary battery in which gas generation can be suppressed while it is stored under a high-temperature condition; and a gas-generation inhibitor and a nonaqueous electrolyte which are used for the nonaqueous secondary battery.SOLUTION: A nonaqueous secondary battery of the invention comprises: a positive electrode; a Si-based negative electrode; and a nonaqueous electrolyte. The nonaqueous electrolyte includes a gas-generation inhibitor having dioxanes.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-aqueous secondary battery, a gas generation inhibitor and a non-aqueous electrolyte solution used therefor.

  Non-aqueous secondary batteries such as lithium ion secondary batteries are used in a wide range of fields such as mobile phones, notebook computers, and vehicle drive sources. For example, a silicon-based material having a large theoretical capacity is used as the negative electrode active material of the lithium ion secondary battery, and a lithium metal composite oxide is used as the positive electrode active material (Patent Document 1).

However, when a battery using a lithium metal composite oxide as a positive electrode active material is stored in a charged state at a high temperature, the lithium metal composite oxide is deteriorated and the organic component in the electrolyte is oxidized to generate CO ₂ gas. There was a problem.

  Therefore, Patent Documents 2 and 3 propose improving battery characteristics by adding a silicon compound to the electrolytic solution. Patent Document 4 proposes to suppress gas generation during high-temperature storage by adding a halogen-containing phosphate ester compound.

Japanese Patent Application Laid-Open No. 2011-165583 Japanese Patent Laying-Open No. 2015-118859 Japanese Patent Laying-Open No. 2015-18802 JP 2011-96462 A

  The inventor has eagerly searched for a technique for suppressing gas generation during high-temperature storage by using a method different from the conventional technique for non-aqueous secondary batteries.

  This invention is made | formed in view of this situation, and provides the non-aqueous secondary battery which can suppress the gas generation at the time of high temperature storage, the gas generation inhibitor used for this, and a non-aqueous electrolyte. Let it be an issue.

  The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery comprising a positive electrode, a Si-based negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte includes a dioxane. including.

  The gas generation inhibitor of the present invention is a gas generation inhibitor for a non-aqueous secondary battery provided with a Si-based negative electrode, and the gas generation inhibitor has dioxanes.

  The non-aqueous electrolyte solution of the present invention is a non-aqueous electrolyte solution for a non-aqueous secondary battery having a Si-based negative electrode, and the non-aqueous electrolyte solution includes a halogen-containing lithium salt and dioxanes for suppressing gas generation. And a non-aqueous solvent.

  According to the said structure, the non-aqueous secondary battery which can suppress the gas generation at the time of high temperature storage, the gas generation inhibitor used for this, and a non-aqueous electrolyte can be provided.

It is a figure which shows the relationship between the storage days of the high temperature storage test of the batteries E1 and C1, and the gas amount generated from the batteries. It is a figure which shows the relationship between the storage days of a high temperature storage test of a battery E1, C1, and a capacity | capacitance maintenance factor. It is a figure which shows the Mn elution amount after the high temperature storage test of battery E2-E4, C1.

  The gas generation inhibitor, non-aqueous electrolyte and non-aqueous secondary battery according to the embodiment of the present invention will be described in detail.

(Gas generation inhibitor)
The gas generation inhibitor for a nonaqueous secondary battery according to an embodiment of the present invention has dioxanes.

  When the gas generation inhibitor of this embodiment is included in an electrolyte and used in a non-aqueous secondary battery, gas generation can be suppressed when the non-aqueous secondary battery is stored at a high temperature. The reason is considered as follows.

In general, when a non-aqueous secondary battery is manufactured and stored at a high temperature, a halogen-containing lithium salt (for example, a fluorine-containing lithium salt) in the electrolytic solution is decomposed to generate HF (hydrofluoric acid). HF degrades the positive electrode active material and generates oxygen from the components of the positive electrode active material. Oxygen oxidizes the organic matter in the electrolyte to generate CO ₂ .

The gas generation inhibitor of this embodiment has dioxanes. When this gas generation inhibitor is added to the non-aqueous electrolyte, a stable film is formed on the surface of the positive electrode active material by the dioxanes. Deterioration of the positive electrode active material due to HF generated during high temperature storage is suppressed, and release of oxygen contained in the positive electrode active material is suppressed. It is considered that the organic matter in the electrolyte solution is suppressed by oxygen and the generation of CO ₂ gas is suppressed.

  The Si-based negative electrode includes a negative electrode active material having Si. Since Si has a high capacity, it is excellent as a negative electrode active material for non-aqueous secondary batteries. In general, when a non-aqueous secondary battery using a Si-based negative electrode is stored at a high temperature, gas is generated. However, in this embodiment, the electrolytic solution has dioxanes. In a secondary battery using an electrolytic solution having dioxanes, gas generation from a negative electrode active material having Si can be suppressed.

  In the present embodiment, dioxanes contained in the gas generation inhibitor are compounds having dioxane. Examples of the dioxane include 1,3-dioxanes and 1,4-dioxanes. Among these, the dioxane is preferably composed of 1,3-dioxane represented by the following general formula (1).

(R ¹ , R ² , R ³ and R ⁴ are each independently selected from a hydrogen group or a hydrocarbon group. R ¹ , R ² , R ³ and R ⁴ may be bonded to each other. .)
Examples of the hydrocarbon group include one or more selected from the group of an alkyl group, a cycloalkyl group, an unsaturated alkyl group, an unsaturated cycloalkyl group, and an aromatic group. Of these, the hydrocarbon group is preferably an alkyl group. The number of carbon atoms of the alkyl group as the hydrocarbon group for R ¹ , R ² , R ³ , and R ⁴ is preferably 1 or more and 10 or less, more preferably 1 or more and 6 or less, and more preferably 4 or less.

In the general formula (1), R ¹ , R ² , R ³ , and R ⁴ are preferably hydrogen groups. In this case, 1,3-dioxane is 1,3-dioxane. 1,3-dioxane is represented by the following chemical formula (2).

(Electrolyte for non-aqueous secondary batteries)
The electrolyte solution of this embodiment is a non-aqueous electrolyte solution for non-aqueous secondary batteries provided with a Si-based negative electrode. The electrolytic solution may include a gas generation inhibitor having dioxanes, a halogen-containing lithium salt, and a non-aqueous solvent in which these are dissolved.

  The concentration of dioxane when the electrolytic solution of this embodiment is 100% by mass is preferably 0.2 to 1% by mass, and more preferably 0.2 to 0.7% by mass. 0.2 to 0.5% by mass is preferable. In this case, gas generation during high-temperature storage of the nonaqueous secondary battery can be further suppressed.

  It is preferable that the electrolyte solution of this embodiment further contains a fluorine-containing cyclic carbonate. The fluorine-containing cyclic carbonate contributes to the improvement of the cycle characteristics of the secondary battery.

  Here, the fluorine-containing cyclic carbonate only needs to contain at least one fluorine, and may contain other halogens. The fluorine-containing cyclic carbonate is preferably represented by the following chemical formula (3).

(In the chemical formula (3), each R ¹³ is independently hydrogen, fluorine, an alkyl group or a fluorinated alkyl group, and at least one of them represents a fluorine or fluorinated alkyl group)
In the chemical formula (3), when R ¹³ is an alkyl group or a fluorinated alkyl group, the carbon number thereof is preferably 1 or 2. Particularly preferably, the fluorine-containing cyclic carbonate having a structure in which at least one fluorine is bonded to one or more carbons constituting the cyclic structure as represented by the following chemical formulas (4-1) to (4-3). is there.

  Of these, 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate: FEC) represented by the chemical formula (4-1) is preferable from the viewpoint of oxidation resistance.

  It is preferable that the non-aqueous solvent in the electrolyte solution of this embodiment uses a cyclic carbonate and a chain carbonate in combination. The cyclic carbonate may have the fluorine-containing cyclic carbonate. Cyclic carbonate has a high dielectric constant, and chain carbonate has low viscosity. For this reason, when electrolyte solution contains both a cyclic carbonate and a chain carbonate, the movement of electrolyte ion can be made smooth and battery capacity can be improved.

  When the total amount of the non-aqueous solvent in the electrolytic solution is 100% by volume, the cyclic carbonate content is 20 to 40% by volume, further 25 to 35% by volume, and the chain carbonate content is 60 to 80% by volume, It is good that it is 65-75 volume%. The cyclic carbonate increases the dielectric constant of the electrolytic solution, while having a high viscosity. Cyclic carbonate has a high dielectric constant and improves the conductivity of the electrolyte. If the viscosity is high, the movement of the electrolyte ions is hindered and the conductivity is deteriorated. Chain carbonate has a low dielectric constant but low viscosity. By blending them in a well-balanced range within the above-described blending ratio, the dielectric constant of the non-aqueous solvent can be increased to some extent and the viscosity can be decreased to adjust the solvent with good conductivity, and the battery capacity can be improved. .

  As cyclic carbonate, in addition to fluorine-containing cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, γ-butyrolactone, vinylene carbonate, 2-methyl-gammabutyrolactone, acetyl-gammabutyrolactone, or gamma valero Examples include lactones.

  The chain carbonate is not particularly limited as long as it is a chain. Examples of the chain carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dibutyl carbonate, dipropyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. It is done.

The halogen-containing lithium salt contained in the electrolytic solution functions as an electrolyte. The halogen-containing lithium salt is preferably a fluorine-containing lithium salt. As the fluorine-containing lithium salt, LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ or the like can be used. As the halogen-containing lithium salt, in addition to the fluorine-containing lithium salt, a chlorine-containing lithium salt such as LiClO ₄ or LiAlCl ₄ may be used. The concentration of the halogen-containing lithium salt in the electrolytic solution is preferably 0.5 mol / L to 1.7 mol / L.

(Non-aqueous secondary battery)
The non-aqueous secondary battery of the present embodiment has the above-described non-aqueous secondary battery electrolyte, a positive electrode, and a Si-based negative electrode.

  The positive electrode has a current collector and a positive electrode active material layer covering the surface of the current collector. The positive electrode may have a lithium metal composite oxide.

  The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel, etc. Metal materials can be exemplified. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  The positive electrode active material layer includes a positive electrode active material and, if necessary, a conductive additive and / or a binder.

The lithium metal composite oxide often functions as a positive electrode active material. Lithium metal composite oxide is a layered compound of Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu , Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, at least one element, 1.7 ≦ f ≦ 3), Li ₂ MnO ₃ can be mentioned. Further, as a lithium metal composite oxide of a positive electrode active material, a solid solution composed of a spinel such as LiMn ₂ O ₄ and a mixture of a spinel and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (where M is a formula) And a polyanionic compound represented by (for example, selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the lithium-metal composite oxide of the positive electrode active _{material, LiFePO 4 F LiMPO 4 F (} M is a transition metal) tavorite based compound represented by such as, Limbo ₃ such LiFeBO ₃ (M is a transition metal) are represented by Borate compounds. Any lithium metal composite oxide used as a positive electrode active material may have the above composition formula as a basic composition, and a material obtained by substituting a metal element contained in the basic composition with another metal element can also be used as a positive electrode active material. It is.

Further, as the positive electrode active material, a positive electrode active material that does not contain lithium ions that contribute to charge / discharge other than the lithium metal composite oxide can be used instead of or together with the lithium metal composite oxide. . Examples of the positive electrode active material include, for example, sulfur alone, a compound in which sulfur and carbon are combined, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ and MnO ₂ , polyaniline and anthraquinone, and aromatics thereof. A compound included in the chemical structure, a conjugated material such as a conjugated diacetate-based organic substance, and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material. When using a positive electrode active material that does not contain lithium, it is necessary to add ions to the positive electrode and / or the negative electrode in advance by a known method. Here, in order to add the ion, a metal or a compound containing the ion may be used.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, such as carbon black, graphite, acetylene black, ketjen black (registered trademark), vapor grown carbon fiber (Vapor Grown Carbon). Fiber: VGCF) and various metal particles are exemplified. These conductive assistants can be added to the active material layer alone or in combination of two or more.

  The blending ratio of the conductive additive in the active material layer is preferably a mass ratio of active material: conductive additive = 1: 0.005 to 1: 0.5, and 1: 0.01 to 1: 0. .2 is more preferable, and 1: 0.03 to 1: 0.1 is even more preferable. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

  The binder plays a role of securing an active material or a conductive auxiliary agent to the surface of the current collector and maintaining a conductive network in the electrode. As binders, fluorine-containing resins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins Examples thereof include acrylic resins such as poly (meth) acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose. These binders may be used singly or in plural.

  The blending ratio of the binder in the active material layer is preferably a mass ratio of active material: binder = 1: 0.001 to 1: 0.3, and 1: 0.005 to 1: 0. .2 is more preferable, and 1: 0.01 to 1: 0.15 is still more preferable. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The Si-based negative electrode includes a negative electrode active material having Si. The Si-based negative electrode has a current collector and a negative electrode active material layer covering the surface of the current collector. What is necessary is just to employ | adopt suitably what was demonstrated with the positive electrode about a collector. The negative electrode active material layer includes a negative electrode active material having Si, and, if necessary, a conductive additive and / or a binder.

  Si functions as a negative electrode active material. Si is an element that can occlude and release lithium ions and can be alloyed with lithium. The negative electrode active material having Si may be a simple substance or a silicon compound having Si and another element.

  As the negative electrode active material having Si, a silicon material is preferably used, and only a silicon material may be employed, or a silicon material and a known negative electrode active material may be used in combination.

  The silicon material preferably has a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. This structure can be confirmed by observation with a scanning electron microscope or the like. In consideration of using a silicon material as an active material of a lithium ion secondary battery, the plate-like silicon body has a thickness in the range of 10 nm to 100 nm for efficient insertion and desorption reaction of lithium ions. A thing in the range of 20 nm-50 nm is more preferable. The length of the plate-like silicon body in the major axis direction is preferably in the range of 0.1 μm to 50 μm. Moreover, it is preferable that (length in the major axis direction of the plate-like silicon body) / (thickness of the plate-like silicon body) in the plate-like silicon body is in the range of 2 to 1,000.

  The silicon material may be pulverized or classified to form particles having a certain particle size distribution. As a preferable particle size distribution of the silicon material, D50 can be exemplified within a range of 1 to 30 μm when measured with a general laser diffraction particle size distribution measuring apparatus. It is preferable to use a silicon material coated with carbon.

  The size of the silicon crystallite of the silicon material is preferably nano-sized. Specifically, the silicon crystallite size is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The silicon crystallite size is calculated from Scherrer's equation using X-ray diffraction measurement (XRD measurement) on the silicon material and using the half width of the diffraction peak of the Si (111) plane of the obtained XRD chart. Note that the silicon crystallite described here means that observed as a broad peak on the XRD chart, and can be distinguished from the crystalline silicon described above in terms of the peak shape.

The method for producing a silicon material includes a reaction step of reacting CaSi ₂ with an acid.

  Acids include hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, methanesulfonic acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluoroarsenic acid, fluoro Examples include antimonic acid, hexafluorosilicic acid, hexafluorogermanic acid, hexafluorotin (IV) acid, trifluoroacetic acid, hexafluorotitanic acid, hexafluorozirconic acid, trifluoromethanesulfonic acid, and fluorosulfonic acid. These acids may be used alone or in combination.

  In addition, the acid is preferably used as an aqueous solution from the viewpoints of easy work and safety, and removal of by-products.

Acid used in the reaction step, may be used in an amount capable of providing 2 or more equivalents of protons relative CaSi _2. Therefore, if it is a monovalent acid, it may be used in an amount of 2 mol or more per 1 mol of CaSi ₂ .

  The reaction conditions of the reaction step are preferably reduced pressure conditions such as vacuum or an inert gas atmosphere, and are preferably temperature conditions of room temperature or lower such as an ice bath. What is necessary is just to set the reaction time of the same process suitably.

  In the reaction step, the reaction formula when hydrogen chloride is used as the acid is as follows.

3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂
Si ₆ H ₆ which is polysilane corresponds to an ideal layered silicon compound. It can be considered that this reaction forms Si—H bonds while Ca in the layered CaSi ₂ is substituted with 2H. CaSi ₂ has a structure in which a Ca layer and a Si layer are laminated. The layered silicon compound is layered because the basic skeleton of the Si layer in the raw material CaSi ₂ is maintained.

In the reaction step, the acid is preferably used as an aqueous solution as described above. Here, since Si ₆ H ₆ can react with water, the layered silicon compound is rarely obtained only with a compound of Si ₆ H ₆ , and contains an element derived from oxygen or an acid.

  After the reaction step, a filtration step for filtering the layered silicon compound, a washing step for washing the layered silicon compound, a drying step for drying the layered silicon compound, and a step for pulverizing or classifying the layered silicon compound are performed as necessary. It is preferable to do this.

Further, the negative electrode active material having Si is preferably a silicon oxide represented by SiOx (0.3 ≦ x ≦ 2.3). SiOx preferably contains a Si phase and a SiO ₂ phase. The Si phase is composed of simple silicon and is a phase that can occlude and release electrolyte ions. The Si phase has a large theoretical discharge capacity, and expands and contracts as electrolyte ions are stored and released. The SiO ₂ phase is made of SiO ₂ and relaxes expansion / contraction of the Si phase. By Si phase is covered by SiO ₂ phase, it may form a negative electrode active material composed of a Si phase and SiO ₂ phase. Furthermore, it is preferable that a plurality of miniaturized Si phases are covered with a SiO ₂ phase and integrated to form one particle, that is, a negative electrode active material. In this case, the volume change of the whole negative electrode active material particle can be suppressed effectively.

The mass ratio of the SiO ₂ phase to the Si phase at the negative electrode is preferably 1 to 3. In this case, expansion / contraction of the negative electrode active material accompanying charge / discharge is suppressed, and the charge / discharge capacity of the negative electrode active material can be maintained high.

A raw material powder containing silicon monoxide may be used as a raw material for silicon oxide. In this case, silicon monoxide in the raw material powder is disproportionated into two phases of SiO ₂ phase and Si phase. In the disproportionation of silicon monoxide, silicon monoxide, which is a homogeneous solid having an atomic ratio of Si to O of approximately 1: 1, is separated into two phases of SiO ₂ phase and Si phase by reaction inside the solid. . The silicon oxide powder obtained by disproportionation includes a SiO ₂ phase and a Si phase. The disproportionation of silicon monoxide in the raw material powder proceeds by applying energy to the raw material powder. Examples of disproportionation include methods such as heating and milling the raw material powder.

When the raw material powder is heated, it is generally said that almost all silicon monoxide is disproportionated and separated into two phases at 800 ° C. or higher if oxygen is removed. Specifically, a raw material powder containing amorphous silicon monoxide powder is subjected to heat treatment at 800 to 1200 ° C. for 1 to 5 hours in an inert atmosphere such as in a vacuum or an inert gas. A silicon oxide powder containing two phases of an amorphous SiO ₂ phase and a crystalline Si phase is obtained.

  When milling the raw material powder, part of the mechanical energy of the milling contributes to chemical atomic diffusion at the solid phase interface of the raw material powder, and generates an oxide phase, a silicon phase, and the like. In milling, the raw material powder may be mixed using a V-type mixer, a ball mill, an attritor, a jet mill, a vibration mill, a high energy ball mill or the like in an inert gas atmosphere such as vacuum or argon gas. Further heat treatment may be performed after milling to further promote disproportionation of silicon monoxide.

  The silicon oxide is preferably in the form of powder, and its average particle size is preferably 1 to 10 μm. The silicon oxide powder is preferably used after being classified to 2 μm or less, further 4 μm or less.

  About the conductive support agent and binder used for a negative electrode, what was demonstrated in the positive electrode should just be employ | adopted suitably suitably with the same mixture ratio.

  In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, an active material, a solvent, and, if necessary, a binder and / or a conductive aid are mixed to prepare a slurry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The slurry is applied to the surface of the current collector and then dried. In order to increase the electrode density, the dried product may be compressed.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit due to contact between the two electrodes. As separators, natural resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramide (Aromatic polyamide), polyester, polyacrylonitrile, etc., polysaccharides such as cellulose, amylose, fibroin, keratin, lignin, suberin, etc. Examples thereof include porous bodies, nonwoven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. The separator may have a multilayer structure.

  Next, the manufacturing method of a lithium ion secondary battery is demonstrated.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal that communicate with the outside using a lead for current collection, etc., an electrolyte is added to the electrode body and a lithium ion secondary Use batteries. Moreover, the lithium ion secondary battery should just be charged / discharged in the voltage range suitable for the kind of active material contained in an electrode.

  The shape of the lithium ion secondary battery of the present embodiment is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed.

  The lithium ion secondary battery of this embodiment may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or a part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. In addition, lithium ion secondary batteries can be used for wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships, etc. and / or power supplies for auxiliary equipment, aircraft, spacecraft, etc. Power source for power and / or auxiliary equipment, auxiliary power source for vehicles not using electricity as a power source, power source for mobile home robots, power source for system backup, power source for uninterruptible power supply, for electric vehicles You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in a charging station.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Below, various batteries were produced and the characteristics of the batteries were evaluated.

(Battery E1)
<Production of silicon material>
As CaSi ₂ containing crystalline silicon, calcium silicon (hereinafter, sometimes referred to as “crude CaSi ₂ ”) manufactured by Nippon Heavy Chemical Industry Co., Ltd. was employed. The crude CaSi ₂ is in the form of powder that has passed through a sieve having an opening of 250 μm.

-Contacting process A sodium hydroxide aqueous solution of pH 13.4 was prepared as an alkaline aqueous solution.

Crude CaSi ₂ and pH 13.4 aqueous sodium hydroxide solution were charged at a mass ratio of 1: 28.5 into a reaction vessel in a thermostat controlled at 25 ° C., and these were stirred at a stirring speed of 150 rpm for 20 hours. After completion of the stirring, the reaction solution was filtered and the residue was dried under reduced pressure to obtain CaSi ₂ of Example 1.

Reaction step under an argon atmosphere, to a concentration of 35 wt% aqueous HCl 500g which was 10 ° C., a CaSi ₂ of 50g was added and stirred. After confirming that foaming disappeared from the reaction solution, the reaction solution was further stirred for 4 hours under the same conditions. Then, it heated up to room temperature and filtered. The residue was washed with 300 mL of distilled water three times, then with 300 mL of ethanol, and dried under reduced pressure to obtain 39.4 g of a solid. The solid was used as a layered silicon compound.

-Silicon material manufacturing process The layered silicon compound was heated at 900 ° C. for 1 hour in an argon atmosphere containing O ₂ in an amount of 1% by volume or less to obtain a silicon material.

<Manufacture of lithium ion secondary batteries>
45 parts by mass of a silicon material as a negative electrode active material, 40 parts by mass of natural graphite as a negative electrode active material, 5 parts by mass of acetylene black as a conductive additive, 10 parts by mass of polyamideimide as a binder, and N-methyl-2-pyrrolidone as a solvent Mix to prepare a slurry. The slurry was applied to the surface of an electrolytic copper foil having a thickness of about 20 μm as a current collector using a doctor blade and dried to form a negative electrode active material layer on the copper foil. Thereafter, the current collector and the negative electrode active material layer were firmly and closely joined by a roll press. This was dried under reduced pressure at 200 ° C. for 2 hours to obtain a negative electrode having a negative electrode active material layer thickness of 30 μm.

In order to produce a positive electrode, LiNi _0.5 Co _0.3 Mn _0.2 O ₂ as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and acetylene black (AB) as a conductive auxiliary agent. , LiNi _0.5 Co _0.3 Mn _0.2 O ₂ , PVDF and AB are mixed so that the mass ratio is 94: 3: 3, and N-methyl-2-pyrrolidone (NMP) as a solvent is mixed. Was added to obtain a paste-like positive electrode material. The paste-like positive electrode material was applied to the surface of the current collector using a doctor blade to form a positive electrode active material layer. The positive electrode active material layer was dried at 80 ° C. for 20 minutes to remove NMP by volatilization. The aluminum foil with the positive electrode active material layer formed on the surface was compressed using a roll press machine, and the aluminum foil and the positive electrode active material layer were firmly bonded. The joined product was heated in a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape, and a positive electrode was obtained.

  A polyethylene porous membrane was used as the separator.

In order to prepare the electrolytic solution, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are mixed so that the volume ratio is EC / EMC / DMC = 3/3/4. A non-aqueous solvent was prepared by mixing. LiPF ₆ and 1,3-dioxane as an electrolyte were dissolved in a non-aqueous solvent to prepare an electrolytic solution. The chemical formula of 1,3-dioxane is shown in the following chemical formula (2). The concentration of LiPF ₆ in the electrolytic solution was 1 mol / L, and the concentration of 1,3-dioxane was 0.5% by mass.

  An electrode body was produced by sandwiching a polypropylene porous film as a separator between the positive electrode and the negative electrode. This electrode body was sealed with an aluminum film together with an electrolytic solution to obtain a laminate cell. At the time of sealing, two aluminum films are formed into a bag shape by heat-sealing except for a part of the periphery of the aluminum film. The part was completely hermetically sealed. At this time, the tips of the current collector on the positive electrode side and the negative electrode side were protruded from the edge of the film so that they could be connected to external terminals. Thus, a battery E1 made of a laminate cell was obtained.

<High temperature storage test>
The battery E1 was subjected to a high temperature storage test. In the high temperature storage test, the battery E1 was charged using a charger until the state of charge (SOC) was 80% and the voltage was 4.24V. Thereafter, the battery E1 was removed from the charger, and the battery E1 was stored in a 60 ° C. constant temperature bath.

<Gas volume measurement>
Before and after the high temperature storage test, the volume of the battery E1 was measured by the aluminum medes method. Specifically, from the volume A of the battery E1 after storage for an arbitrary number of days (discharged to 3 V after the high temperature storage test), the volume B of the battery E1 before storage (80% SOC before the high temperature storage test, voltage 4. The amount of increase in the volume of the battery E1, which is the difference (A−B), was calculated by subtracting the voltage that was charged to 24V and then discharged to 3V. The volume increase amount of the battery E1 is equal to the amount of gas generated in the battery during the high temperature storage test. The difference (AB) was taken as the gas amount. The measured gas amount is shown in FIG.

<Capacity retention measurement>
About the battery E1, it implemented before the high temperature storage test, the high temperature storage test 6 days, 12 days, and 30 days after, respectively. Each battery was charged until the state of charge (SOC) was 100% and the voltage was 4.5V. Thereafter, each battery was discharged at a constant current of 1 C to a voltage of 2.5 V, and the discharge capacity at the time of discharge was measured. Assuming that the discharge capacity of the battery E1 before the high temperature storage test is C and the discharge capacity of the battery E1 after the high temperature storage test is D, a solution of a calculation formula of 100 × (C−D) / C was obtained. This solution was taken as the capacity maintenance rate of the battery E1, and this is shown in FIG.

(Battery C1)
Battery C1 is the same as Battery E1, except that the electrolyte does not contain 1,3-dioxane. For the battery C1, the same high temperature storage test as the <high temperature storage test> of the battery E1 is performed, and the gas amount and the capacity maintenance ratio before and after the high temperature storage test are measured in the same manner as the <gas amount measurement> and <capacity maintenance ratio measurement>. did. Two batteries were prepared and measured. The measurement results are shown in FIGS.

  As shown in FIG. 1, the battery E1 provided with the electrolytic solution containing 1,3-dioxane is a gas generated during the high-temperature storage test as compared with the battery C1 provided with the electrolytic solution not containing 1,3-dioxane. The amount was remarkably small, and the capacity retention rate after the high temperature storage test was high. Both the amount of gas and the capacity maintenance rate were provided with a battery having an electrolyte solution having 1,3-dioxane and an electrolyte solution not having 1,3-dioxane as the storage days of the high-temperature storage test increased. The difference between the batteries has increased.

(Batteries E2 to E4)
The batteries E2 to E4 are the same as the battery E1 except that the concentration of 1,3-dioxane in the electrolytic solution is different. The density | concentrations of 1, 3- dioxane in the electrolyte solution of battery E2-E4 were 0.2 mass%, 0.5 mass%, and 1 mass% in order.

<Mn elution confirmation>
The batteries E2 to 4 and C1 were subjected to a high temperature storage test in the same manner as the battery E1. The preservation period was 30 days. Each battery after the high temperature storage test was disassembled, and the negative electrode was taken out. The amount of Mn eluted from the positive electrode into the electrolyte and deposited on the surface of the negative electrode was measured with an ICP (High Frequency Inductively Coupled Plasma) emission spectrometer. The measurement results are shown in FIG. The amount of Mn (mass%) in FIG. 3 represents the mass of Mn per gram of the negative electrode active material layer in%.

As shown in FIG. 3, when dioxane was present in the electrolytic solution, the elution amount of Mn was smaller than when no dioxane was present (battery C1). In particular, when the dioxane concentration was 0.2% by mass and 0.5% by mass, the elution amount of Mn was small. From this, the deterioration of the positive electrode was suppressed by the presence of dioxane in the electrolytic solution. It is considered that deterioration of the positive electrode was suppressed, oxygen release was suppressed, oxidation of the electrolyte component was suppressed, and the amount of generated CO ₂ gas was suppressed.

Claims (8)

A non-aqueous secondary battery comprising a positive electrode, a Si-based negative electrode, and a non-aqueous electrolyte solution,
The non-aqueous electrolyte solution is a non-aqueous secondary battery containing a gas generation inhibitor having dioxanes. The non-aqueous secondary battery according to claim 1, wherein the dioxane comprises 1,3-dioxane represented by the following general formula (1).
(R ¹ , R ² , R ³ and R ⁴ are each independently selected from a hydrogen group or a hydrocarbon group. R ¹ , R ² , R ³ and R ⁴ may be bonded to each other. .)   The non-aqueous secondary battery according to claim 2, wherein the hydrocarbon group has one or more groups selected from an alkyl group, a cycloalkyl group, an unsaturated alkyl group, an unsaturated cycloalkyl group, and an aromatic group.   The non-aqueous secondary battery according to claim 1, wherein the Si-based negative electrode includes a silicon material having a structure in which a plurality of plate-like silicon bodies are stacked in a thickness direction.   The non-aqueous secondary battery according to claim 1, wherein the non-aqueous electrolyte has a halogen-containing lithium salt.   The non-aqueous secondary battery according to claim 1, wherein the positive electrode has a lithium metal composite oxide. A gas generation inhibitor for a non-aqueous secondary battery including a Si-based negative electrode,
The gas generation inhibitor is a gas generation inhibitor having dioxanes. A non-aqueous electrolyte for a non-aqueous secondary battery having a Si-based negative electrode,
The non-aqueous electrolyte includes a halogen-containing lithium salt, a gas generation inhibitor having dioxanes, and a non-aqueous solvent.