JP2018116798A - Nonaqueous electrolyte and nonaqueous electrolyte power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte and a manufacturing method, capable of suppressing expansion of a nonaqueous electrolyte power storage device in accordance with a charge-discharge cycle.SOLUTION: A nonaqueous electrolyte according to an embodiment of the present invention is a nonaqueous electrolyte including: a fluorinated cyclic carbonate; and a zirconium salt or a calcium salt of which solubility to water is 0.01 g/100 mL or more. A manufacturing method of the nonaqueous electrolyte according to an embodiment of the present invention is a manufacturing method including the fluorinated cyclic carbonate, and the zirconium salt or the calcium salt of which solubility to water is 0.01 g/100 mL or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-aqueous electrolyte, a non-aqueous electrolyte storage element using the same, and a method for manufacturing a non-aqueous electrolyte storage element.

  Nonaqueous electrolyte secondary batteries typified by lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles and the like because of their high energy density. The non-aqueous electrolyte secondary battery generally includes an electrode body having a pair of electrodes electrically separated by a separator, and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between both electrodes. It is configured to charge and discharge by performing. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors are widely used as power storage elements other than secondary batteries.

  In order to increase the energy density of such a storage element, there is an attempt to use it at a higher voltage. Therefore, for the purpose of improving cycle characteristics by suppressing excessive decomposition of the electrolyte solution on the positive electrode surface and negative electrode exposed to a high charging voltage, a non-aqueous electrolyte containing fluoroethylene carbonate in the non-aqueous electrolyte is provided. It has been developed (see Patent Document 1).

JP 2009-123465 A

  However, as a result of research by the present inventors, it has been found that when a fluorinated cyclic carbonate such as fluoroethylene carbonate is used for the non-aqueous electrolyte, the non-aqueous electrolyte storage element expands with the charge / discharge cycle. .

  The present invention has been made based on the circumstances as described above, and the object thereof is to suppress the expansion of the nonaqueous electrolyte power storage element accompanying the charge / discharge cycle while using the fluorinated cyclic carbonate for the nonaqueous electrolyte. It is to provide a non-aqueous electrolyte and a manufacturing method thereof.

  A non-aqueous electrolyte according to one embodiment of the present invention, which has been made to solve the above-described problem, includes a fluorinated cyclic carbonate and a zirconium salt or a calcium salt having a solubility in water of 0.01 g / 100 mL or more. It is a water electrolyte.

A method for producing a non-aqueous electrolyte according to another aspect of the present invention includes a fluorinated cyclic carbonate, and
This is a method for producing a non-aqueous electrolyte containing a zirconium salt or a calcium salt having a solubility in water of 0.01 g / 100 mL or more.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte which can suppress the expansion | swelling of the nonaqueous electrolyte electrical storage element accompanying a charging / discharging cycle, and its manufacturing method can be provided.

FIG. 1 is an external perspective view showing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a power storage device configured by assembling a plurality of nonaqueous electrolyte secondary batteries according to an embodiment of the present invention.

  One embodiment of the present invention is a nonaqueous electrolyte containing a fluorinated cyclic carbonate and a zirconium salt or a calcium salt having a solubility in water of 0.01 g / 100 mL or more.

According to the nonaqueous electrolyte, it is possible to suppress the expansion of the nonaqueous electrolyte electricity storage element associated with the charge / discharge cycle. The reason for this is not clear, but the following is presumed.
In a storage element using a non-aqueous electrolyte containing a fluorinated cyclic carbonate, it is considered that the storage element expands because a large amount of carbon dioxide gas or the like is contained in the non-aqueous electrolyte with a charge / discharge cycle. ing.
Zirconium salts or calcium salts that are basic compounds have the property of easily capturing carbon dioxide, which is an acidic gas. On the other hand, the non-aqueous electrolyte used for the non-aqueous electrolyte storage element has a very low water content. Therefore, by using a relatively easily soluble zirconium salt or calcium salt having a solubility in water of 0.01 g / 100 mL or more, carbon dioxide dissolved in the non-aqueous electrolyte via a trace amount of water contained in the electrolytic solution, etc. It is considered that the expansion of the nonaqueous electrolyte storage element can be suppressed.

  The “water solubility” is a value measured according to EPA OPPTS 830.7840 (Water Solubility).

  The zirconium salt is preferably zirconium hydroxide, and the zirconium hydroxide content is preferably less than 2% by mass relative to the nonaqueous electrolyte. By setting the zirconium salt content to less than 2% by mass, it is considered that the influence of the zirconium salt or its decomposition product on the coating on the surface of the positive electrode or the negative electrode is reduced. Can be further suppressed.

  The calcium salt is calcium hydroxide, and the content of calcium hydroxide is preferably less than 2% by mass with respect to the nonaqueous electrolyte. By making the content of calcium hydroxide less than 2% by mass, it is considered that the influence of the calcium salt or its decomposition product on the coating on the surface of the positive electrode or the negative electrode is reduced, and therefore the expansion of the nonaqueous electrolyte storage element is further suppressed. be able to.

  One embodiment of the present invention is a method for producing a nonaqueous electrolyte containing a fluorinated cyclic carbonate and a zirconium salt or a calcium salt having a solubility in water of 0.01 mg / 100 mL or more. According to the manufacturing method, it is possible to obtain a nonaqueous electrolyte that can suppress the expansion of the nonaqueous electrolyte electricity storage element associated with the charge / discharge cycle.

<Nonaqueous electrolyte storage element>
The electrical storage element which concerns on one Embodiment of this invention has a positive electrode, a negative electrode, and a nonaqueous electrolyte. Hereinafter, a secondary battery will be described as an example of a power storage element. The positive electrode and the negative electrode usually form an electrode body that is laminated or wound via a separator. The electrode body is housed in a case, and the case is filled with the nonaqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. In addition, as the case, a known aluminum case that is usually used as a case of a secondary battery can be used.

(Positive electrode)
The positive electrode has a conductive base material and a positive electrode mixture layer laminated on the base material.

(Positive electrode base material)
As a material of the positive electrode base material, metals such as aluminum, titanium, and tantalum, or alloys thereof are used. Among these, aluminum and aluminum alloys are preferable from the balance of potential resistance, high conductivity and cost. That is, an aluminum foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H-4000 (2014).

  Although it does not specifically limit as average thickness of the said base material, As a minimum, 10 micrometers is preferable, 12 micrometers is more preferable, and 15 micrometers is further more preferable. On the other hand, as an upper limit, 30 micrometers is preferable, for example, and 20 micrometers is more preferable. By setting the average thickness of the base material within the above range, it is possible to secure sufficient strength and good electronic conductivity while reducing the film thickness.

(Positive electrode mixture layer)
The positive electrode mixture layer is formed of a so-called positive electrode mixture containing a positive electrode active material. Moreover, the positive electrode mixture which forms a positive electrode mixture layer can contain arbitrary components, such as a electrically conductive agent, a binder (binder), a thickener, and a filler as needed.

As the positive electrode active material, for example, a lithium transition metal composite oxide represented by Li _x MO _y (M represents at least one transition metal) (Li _x CoO ₂ , Li having a layered α-NaFeO ₂ type crystal structure) _{x NiO 2, Li x MnO 3} , Li x Ni α Co (1-α) O 2, Li x Ni α Mn β Co (1-α-β) O 2, Li 1 + w Ni α Mn β Co (1-α _-Β-w) O ₂ etc., such as Li _x Mn ₂ O ₄ having a spinel crystal structure, Li _x Ni _α Mn _(2-α) O ₄ ), Li _w Me _x (AO _y ) _z (Me is at least It represents a kind of transition metal, and A represents a polyanion compound represented by, for example, P, Si, B, V, etc. (LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ )) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F, etc.). The elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the electrode mixture layer, one kind of these compounds may be used alone, or two or more kinds may be mixed and used.

Among these, the Li _x Ni _α Mn _β Co _(1-α-β) O ₂ (x is a number of 0.8 or more and 1.3 or less. _Α and β are each independently greater than 0. It is an integer of less than 1).
The ratio of the number of moles of nickel contained in the lithium transition metal composite oxide is preferably more than 30%, more preferably 33% or more, and more preferably 50% or more with respect to the number of moles of transition metal. 60% or more is particularly preferable. On the other hand, when the ratio of the number of moles of nickel to the number of moles of transition metal in the lithium transition metal composite oxide exceeds 80%, the initial Coulomb efficiency of the lithium transition metal composite oxide tends to decrease. From these viewpoints, the ratio of the number of moles of nickel to the number of moles of transition metal in the lithium transition metal composite oxide is preferably 80% or less.
In addition, the lithium transition metal composite oxide having the above-mentioned molar ratio of nickel as described above has a high activity of nickel with respect to the solvent of the non-aqueous electrolyte, and tends to cause side reactions at the positive electrode. It is preferable to apply the nonaqueous electrolyte because the expansion associated with the charge / discharge cycle of the nonaqueous electrolyte storage element can be suppressed.

  The upper limit of the particle size of the positive electrode active material particles is preferably 50 μm, for example, and more preferably 20 μm. On the other hand, the lower limit of the particle size of the positive electrode active material particles is preferably 1 μm, and more preferably 2 μm.

  The conductive agent is not particularly limited as long as it is a conductive material that does not adversely affect the performance of the storage element. Examples of such a conductive agent include natural or artificial graphite, furnace black, acetylene black, ketjen black and other carbon blacks, metals, conductive ceramics, and the like. Examples of the shape of the conductive agent include powder and fiber.

  Examples of the binder (binder) include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyimide; ethylene-propylene-diene rubber (EPDM), Examples thereof include elastomers such as sulfonated EPDM, styrene butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like.

  Examples of the thickener include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like.

  The filler is not particularly limited as long as it does not adversely affect the performance of the storage element. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon.

  Moreover, as an upper limit of the porosity of the said positive electrode compound material layer, 35 volume% is preferable, 28 volume% is more preferable, and 26 volume% is further more preferable. Thus, by making the porosity of the positive electrode mixture layer relatively low, the amount of side reaction with the nonaqueous electrolyte in the positive electrode is reduced, and the charge / discharge cycle performance of the nonaqueous electrolyte storage element can be improved. On the other hand, the lower limit may be, for example, 20% by volume or 24% by volume.

The upper limit of the coating weight per one surface of the positive electrode composite material layer is preferably 25 mg / cm ^2, more preferably ^{20mg / cm 2, 17mg / cm} 2 is more preferred. On the other hand, the lower limit of the coating amount of the positive-electrode mixture layer is preferably 5 mg / cm ^2, more preferably ^{10mg / cm 2, 12mg / cm} 2 is more preferred. By setting it as the coating mass of such a positive mix layer, charging / discharging cycling performance can be improved, maintaining the energy density of a nonaqueous electrolyte electrical storage element.

The density of the positive electrode is not particularly limited, and the lower limit may be 2 g / cm ³ , but 3 g / cm ³ is preferable and 3.2 g / cm ³ is more preferable. Thus, by making the density of the positive electrode relatively high, it is possible to increase the energy density while reducing the influence on the charge / discharge cycle performance of the nonaqueous electrolyte storage element. On the other hand, the upper limit is preferably ^{4g / cm 3, 3.4g / cm} 3 is more preferable.

  The average thickness of the positive electrode can be, for example, 10 μm or more and 200 μm or less.

(Negative electrode)
The negative electrode has a negative electrode base material and a negative electrode mixture layer laminated on the negative electrode base material.

  As a material of the negative electrode base material, a metal such as copper, nickel, stainless steel, nickel-plated steel, or an alloy thereof is used, and copper or a copper alloy is preferable. That is, copper foil is preferable as the negative electrode substrate. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

  The negative electrode mixture layer is formed from a so-called negative electrode mixture containing a negative electrode active material. Moreover, the negative electrode composite material which forms a negative electrode composite material layer contains arbitrary components, such as a electrically conductive agent, a binder (binder), a thickener, and a filler as needed. Arbitrary components such as a conductive agent, a binder, a thickener, and a filler can be the same as those for the positive electrode mixture layer.

  As the negative electrode active material, a material that can occlude and release lithium ions is usually used. Specific negative electrode active materials include, for example, metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide and Sn oxide; polyphosphate compounds; graphite (graphite) and amorphous Examples thereof include carbon materials such as carbon (easily graphitizable carbon or non-graphitizable carbon).

  Further, the negative electrode mixture layer is composed of typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, and typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, and Ge. , Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W may be included.

(Separator)
The separator plays a role of isolating the positive electrode and the negative electrode and holding the nonaqueous electrolyte. As the material of the separator, for example, woven fabric, non-woven fabric, porous resin film or the like is used. Among these, a porous resin film is preferable. The main component of the porous resin film is preferably a polyolefin such as polyethylene or polypropylene from the viewpoint of strength. Moreover, you may use the porous resin film which compounded these resins and resin, such as an aramid and a polyimide.

(Nonaqueous electrolyte)
The non-aqueous electrolyte contains, in addition to the non-aqueous solvent and the electrolyte salt, a fluorinated cyclic carbonate and a zirconium salt or calcium salt having a solubility in water of 0.01 g / 100 mL or more. Furthermore, in order to improve the performance of the nonaqueous electrolyte electricity storage element, the nonaqueous electrolyte may contain an additive within a range that does not completely cancel the effects of the present invention.

As the fluorinated cyclic carbonate, fluoroethylene carbonate (FEC), fluorovinylene carbonate, fluoropropylene carbonate (FPC), trifluoroethylene carbonate (TFEC), difluoroethylene carbonate (DFEC), and the like can be used.
Among these, fluoroethylene carbonate (FEC) is preferable. By using fluoroethylene carbonate (FEC), the oxidative decomposition of the non-aqueous solvent at the positive electrode is suppressed, and the charge / discharge cycle characteristics of the non-aqueous electrolyte storage element can be improved.

As the zirconium salt, one having a water solubility of 0.01 g / 100 mL or more is used. Such zirconium salts include zirconium hydroxide (solubility 0.02 g / 100 mL), tetrakis (2,4-pentanedionato) zirconium (IV) (solubility 1.4 g / 100 mL), zirconium sulfate (IV) (solubility) 52.5 g / 100 mL), zirconium fluoride (solubility 1.32 g / 100 mL), zirconium chloride (solubility 0.2 g / 100 mL), and the like can be used.
Among these, it is preferable to use zirconium hydroxide.

  The upper limit of the content of zirconium hydroxide is preferably less than 2% by mass with respect to the nonaqueous electrolyte in order to reduce the influence of the zirconium salt and its decomposition product on the coating on the positive electrode and negative electrode surfaces. More preferably, it is 1.5 mass% or less, More preferably, it is 1 mass% or less. In addition, the lower limit is preferably 0.01% by mass or more with respect to the nonaqueous electrolyte in order to efficiently absorb carbon dioxide gas and the like in the nonaqueous electrolyte. More preferably, it is 0.1 mass% or more, More preferably, it is 0.5 mass% or more, Most preferably, it is more than 0.5 mass%. Especially, it is preferable for it to be more than 0.5% by mass and 1% by mass or less because the effect of suppressing the expansion of the nonaqueous electrolyte electricity storage device is particularly high. In addition, 0.5 mass% or more and 1 mass% or less are preferable since the charge / discharge cycle performance of the nonaqueous electrolyte storage element is also improved.

As the calcium salt, one having a water solubility of 0.01 g / 100 mL or more is used. As such a calcium salt, calcium hydroxide (solubility 0.17 g / 100 mL), calcium sulfate (solubility 0.21 g / 100 mL), and the like can be used.
Among these, it is preferable to use calcium hydroxide.

The upper limit of the content of calcium hydroxide is preferably less than 2% by mass with respect to the non-aqueous electrolyte in order to reduce the influence of the calcium salt or its decomposition product on the coating on the positive electrode or negative electrode surface. More preferably, it is 1.5 mass% or less, More preferably, it is 1 mass% or less. In addition, the lower limit is preferably 0.01% by mass or more with respect to the nonaqueous electrolyte in order to efficiently absorb carbon dioxide gas and the like in the nonaqueous electrolyte. More preferably, it is 0.1 mass% or more, More preferably, it is 0.5 mass% or more, Most preferably, it is more than 0.5 mass%.
Especially, it is preferable for it to be more than 0.5% by mass and 1% by mass or less because the effect of suppressing the expansion of the nonaqueous electrolyte electricity storage device is particularly high.

  As said non-aqueous solvent, the well-known non-aqueous solvent normally used as a non-aqueous solvent of the general non-aqueous electrolyte for electrical storage elements can be used. Examples of the non-aqueous solvent include cyclic carbonate, chain carbonate, ester, ether, amide, sulfone, lactone, and nitrile. Among these, it is preferable to use at least cyclic carbonate or chain carbonate, and it is more preferable to use cyclic carbonate and chain carbonate in combination.

  Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), styrene carbonate, catechol carbonate, 1-phenyl vinylene carbonate, 1 , 2-diphenyl vinylene carbonate, etc., among which EC is preferred.

  Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diphenyl carbonate. Among these, EMC is preferable.

  As said electrolyte salt, the well-known electrolyte salt normally used as an electrolyte salt of the general nonaqueous electrolyte for electrical storage elements can be used. Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, onium salt, and the like, and lithium salt is preferable.

Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ F) ₂ , LiSO ₃ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO Fluorohydrocarbon groups such as ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), LiC (SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) ₃ A lithium salt having Among these, inorganic lithium salts are preferable.

  As a minimum of content of the above-mentioned electrolyte salt in the above-mentioned nonaqueous electrolyte, 0.1M is preferred, 0.3M is more preferred, 0.5M is still more preferred, and 0.7M is especially preferred. On the other hand, the upper limit is not particularly limited, but is preferably 2.5M, more preferably 2M, and even more preferably 1.5M.

  Examples of the additive include sulfur-containing compounds such as propene sultone, diglycol sulfate, pentyl glycol sulfate and propylene sulfate, nitrile compounds such as succinonitrile, phosphorus-containing compounds such as lithium difluorophosphate and lithium tetrafluorooxalate phosphate. And boron-containing compounds such as lithium bisoxalate borate. Among these, from the viewpoint of charge / discharge cycle performance of the nonaqueous electrolyte storage element, a sulfur-containing compound is preferable, and propene sultone is more preferable.

<Method for Manufacturing Nonaqueous Electrolyte Storage Element>
The method for producing the nonaqueous electrolyte electricity storage device according to one embodiment of the present invention is as follows.
(1) Dissolving an electrolyte salt in a mixed solution of a non-aqueous solvent and a fluorinated cyclic carbonate (2) Adding a zirconium salt or a calcium salt to the solution so as to have a predetermined content (3) In (2) The obtained non-aqueous electrolyte is injected into a container of a non-aqueous electrolyte storage element to be described later.

In addition, the method for manufacturing the nonaqueous electrolyte electricity storage device according to one embodiment of the present invention includes:
(1) Add a zirconium salt or a calcium salt to a mixed solution of a nonaqueous solvent and a fluorinated cyclic carbonate. (2) Dissolve an electrolyte salt in the above solution. (3) A nonaqueous electrolyte obtained in (2) is obtained. Alternatively, it may be injected into a container of a non-aqueous electrolyte storage element to be described later. Here, the zirconium salt or calcium salt has a solubility in water of 0.01 g / 100 mL or more. Moreover, you may add both a zirconium salt and a calcium salt.

  The nonaqueous electrolyte can be obtained by a known method except for the steps (1) and (2).

<Other embodiments>
The present invention is not limited to the above-described embodiment, and can be implemented in a mode in which various changes and improvements are made in addition to the above-described mode. In the said embodiment, although demonstrated centering on the form whose electrical storage element is a secondary battery, another electrical storage element may be sufficient. Examples of other power storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like.

  FIG. 1 shows a schematic diagram of a rectangular nonaqueous electrolyte secondary battery 1 (secondary battery 1) which is an embodiment of a power storage device according to the present invention. In the figure, the inside of the container is seen through. In the secondary battery 1 shown in FIG. 1, an electrode body 2 is accommodated in a battery container 3. The electrode body 2 is formed by winding a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material via a separator. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4 ′, and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5 ′. Further, the nonaqueous electrolyte of the present invention is injected into the battery container 3. The specific configuration of each element such as the positive electrode is as described above.

  The configuration of the electricity storage device according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), a flat battery, and the like. The present invention can also be realized as a power storage device including a plurality of the above power storage elements. One embodiment of a power storage device is shown in FIG. In FIG. 2, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of secondary batteries 1. The power storage device 30 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
(Positive electrode)
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ was used as the positive electrode active material. Using this positive electrode active material, acetylene black (AB) as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a non-aqueous solvent, a positive electrode mixture paste is prepared. Produced. The mass ratio of the positive electrode active material, the binder, and the conductive agent was 93: 3: 4 (in terms of solid content). This positive electrode mixture paste was intermittently coated on both sides of an aluminum foil (thickness: 15 μm) as a positive electrode substrate, leaving a positive electrode mixture layer non-formed part, and dried to prepare a positive electrode mixture layer. Thereafter, the surface of the positive electrode mixture layer was roll-pressed to obtain a positive electrode. The coating mass per one side of the positive electrode was 17.7 mg / cm ² .

(Negative electrode)
A negative electrode mixture paste was prepared using graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC), and water as a solvent. The mass ratio of graphite, SBR, and CMC was 96.7: 2.1: 1.2. The negative electrode mixture paste was prepared through a kneading step using a multi-blender mill by adjusting the amount of water to adjust the solid content (mass%). This negative electrode paste was intermittently applied to both sides of a copper foil (thickness: 10 μm) leaving a negative electrode mixture layer non-formed part, and dried to prepare a negative electrode mixture layer. Thereafter, roll pressing was performed to prepare a negative electrode. The coating mass per one side of the positive electrode was 11.0 mg / cm ² .

(Nonaqueous electrolyte)
Dissolve lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate and ethyl methyl carbonate are mixed to 10% by volume and 90% by volume, respectively, so that the salt concentration is 1.0 mol / L. I let you. A non-aqueous electrolyte was prepared by adding propene sultone to this solution at 2 mass% with respect to the non-aqueous electrolyte and calcium hydroxide at 0.5 mass% with respect to the non-aqueous electrolyte. The amount of water in the nonaqueous electrolyte was less than 50 ppm.

(Separator)
As the separator, a polyethylene microporous membrane having a thickness of 21 μm was used.

(Battery assembly)
The positive electrode, the negative electrode, and the separator were laminated and wound. Thereafter, the positive electrode mixture layer non-forming part of the positive electrode and the negative electrode mixture layer non-forming part of the negative electrode are welded to the positive electrode lead and the negative electrode lead, respectively, and sealed in an aluminum rectangular container. Water electrolyte was injected and sealed. In this way, the battery of Example 1 was produced.

[Example 2]
Dissolve lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate and ethyl methyl carbonate are mixed to 10% by volume and 90% by volume, respectively, so that the salt concentration is 1.0 mol / L. I let you. A non-aqueous electrolyte was prepared by adding propene sultone to this solution at 2 mass% with respect to the non-aqueous electrolyte and zirconium hydroxide at 0.5 mass% with respect to the non-aqueous electrolyte. A battery of Example 2 was obtained in the same manner as Example 1 except that this nonaqueous electrolyte was used.

[Comparative Example 1]
Dissolve lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate and ethyl methyl carbonate are mixed to 10% by volume and 90% by volume, respectively, so that the salt concentration is 1.0 mol / L. I let you. A non-aqueous electrolyte was prepared by adding propene sultone to this solution so that it might become 2 mass% with respect to a non-aqueous electrolyte. A battery of Comparative Example 1 was obtained in the same manner as Example 1 except that this non-aqueous electrolyte was used.

[Comparative Example 2]
Dissolve lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate and ethyl methyl carbonate are mixed to 10% by volume and 90% by volume, respectively, so that the salt concentration is 1.0 mol / L. I let you. A nonaqueous electrolyte was prepared by adding propene sultone to this solution at 2% by mass with respect to the nonaqueous electrolyte and aluminum hydroxide at 0.5% by mass with respect to the nonaqueous electrolyte. A battery of Comparative Example 2 was obtained in the same manner as Example 1 except that this non-aqueous electrolyte was used.

[Evaluation]
(Capacity measurement)
For each of the batteries of Examples 1 and 2 and Comparative Examples 1 and 2 produced as described above, the following capacity measurement was carried out in a thermostat set at 25 ° C., and the electric capacity equivalent to the nominal capacity of the battery was measured. It was confirmed that an amount of charge / discharge was possible. The charging conditions for the capacity measurement were constant current and constant voltage charging with a current value of 1 CA and a voltage of 4.35 V. The charging time was 3 hours from the start of energization. The discharge conditions were a constant current discharge with a current of 1 CA and a final voltage of 2.75V. A 10 minute rest period was provided between charging and discharging. Note that 1CA, which is the current value, is a current value that provides the same amount of electricity as the nominal capacity of the battery when the battery is energized for one hour at a constant current.

(Battery thickness measurement before cycle test)
About each battery after capacity | capacitance measurement, the battery thickness was measured.
The center of the long side surface of the battery was sandwiched with calipers from a direction substantially perpendicular to the long side surface (in a direction substantially horizontal to the surface direction of the short side surface), and the battery thickness was measured. This value was recorded as “battery thickness before cycle-1 (mm)”.

(Charge / Discharge Cycle Test-1)
About each battery after battery thickness measurement, the charging / discharging cycle test was done in the thermostat set to 45 degreeC.
100 cycles of charging / discharging for repeating a constant current / constant voltage charging with a charging current of 1 CmA and a charging voltage of 4.35 V and a constant current discharging with a discharging current of 1 CmA and a discharge end voltage of 2.75 V were performed.

(Measurement of battery thickness after cycle test)
For each battery after the charge / discharge cycle test, the battery thickness was measured in the same manner as before the cycle test.
This value was recorded as “battery thickness after cycle-1 (mm)”.
The ratio of “battery thickness after cycle-1 (mm)” to “battery thickness before cycle-1 (mm)” (battery thickness after cycle-1 / battery thickness before cycle-1) is set to “battery thickness increase”. Rate-1 (%) ". Table 1 shows the value of “battery thickness increase rate−1 (%)”.

As shown in Table 1, in a non-aqueous electrolyte containing a fluorinated cyclic carbonate, a battery using a non-aqueous electrolyte containing a zirconium salt or a calcium salt having a solubility in water of 0.01 g / 100 mL or more (Examples) In Example 1 and Example 2), the rate of increase in battery thickness after the 45 ° C. cycle test is smaller compared to the battery using the non-aqueous electrolyte containing no zirconium salt or calcium salt (Comparative Example 1). I understand that.
Further, the batteries of Example 1 and Example 2 were not the zirconium salt or the calcium salt, but were compared with a battery using a nonaqueous electrolyte containing an aluminum salt (Comparative Example 2). It can be seen that the battery thickness increase rate is small.
From these results, in a non-aqueous electrolyte containing a fluorinated cyclic carbonate, a battery accompanying a cycle test can be obtained by using a non-aqueous electrolyte containing a zirconium salt or a calcium salt having a solubility in water of 0.01 g / 100 mL or more. Swelling can be suppressed.

[Example 3]
Dissolve lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which fluoroethylene carbonate and ethyl methyl carbonate are mixed to 10% by volume and 90% by volume, respectively, so that the salt concentration is 1.0 mol / L. I let you. A non-aqueous electrolyte was prepared by adding propene sultone to this solution at 2 mass% with respect to the non-aqueous electrolyte and zirconium hydroxide at 1 mass% with respect to the non-aqueous electrolyte. A battery of Example 3 was obtained in the same manner as Example 1 except that this nonaqueous electrolyte was used.

[Evaluation]
(Capacity measurement)
For each of the batteries of Examples 2 and 3 and Comparative Example 1 produced as described above, the following capacity measurement was performed in a thermostat set at 25 ° C., and the amount of electricity equivalent to the nominal capacity of the battery was measured. It was confirmed that charging / discharging was possible. The charging conditions for the capacity measurement were constant current and constant voltage charging with a current value of 1 CA and a voltage of 4.35 V. The charging time was 3 hours from the start of energization. The discharge conditions were a constant current discharge with a current of 1 CA and a final voltage of 2.75V. A 10 minute rest period was provided between charging and discharging. Note that 1CA, which is the current value, is a current value that provides the same amount of electricity as the nominal capacity of the battery when the battery is energized for one hour at a constant current.

(Battery thickness measurement before cycle test)
About each battery after capacity | capacitance measurement, the battery thickness was measured.
The center of the long side surface of the battery was sandwiched with calipers from a direction substantially perpendicular to the long side surface (in a direction substantially horizontal to the surface direction of the short side surface), and the battery thickness was measured. This value was recorded as “battery thickness before cycle-2 (mm)”.

(Charge / discharge cycle test-2)
About each battery after battery thickness measurement, the charging / discharging cycle test was done in the thermostat set to 45 degreeC.
500 cycles of charging and discharging were repeated for 1 CmA of charging current, constant current and constant voltage charging with a charging voltage of 4.35 V, and constant current discharging with discharging current of 1 CmA and an end-of-discharge voltage of 2.75 V.
The ratio of the discharge capacity (mAh) at the 500th cycle to the discharge capacity (mAh) at the first cycle in the cycle test is shown in Table 2 as “capacity maintenance ratio (%)”.

(Measurement of battery thickness after cycle test)
For each battery after the charge / discharge cycle test, the battery thickness was measured in the same manner as before the cycle test.
This value was recorded as “battery thickness after cycle-2 (mm)”.
The ratio of “battery thickness after cycle-2 (mm)” to “battery thickness before cycle-2 (mm)” (battery thickness after cycle-2 / battery thickness before cycle-2) is set to “battery thickness increase”. Rate-2 (%) ". Table 2 shows the value of “battery thickness increase rate−2 (%)”.

As shown in Table 2, in a nonaqueous electrolyte containing a fluorinated cyclic carbonate, a battery using a nonaqueous electrolyte containing 0.5% by mass and 1% by mass of zirconium hydroxide (Example 2 and Example 3) It can be seen that the rate of increase in the battery thickness after the 45 ° C. cycle test is smaller than that of the battery using the non-aqueous electrolyte containing no zirconium salt (Comparative Example 1).
Further, the battery using the non-aqueous electrolyte containing 1% by mass of zirconium hydroxide (Example 3) is 45 ° C. than the battery using the non-aqueous electrolyte containing 0.5% by mass of zirconium hydroxide (Example 2). It can be seen that the battery thickness increase rate after the cycle test is small.
Further, batteries using nonaqueous electrolytes containing 0.5% by mass and 1% by mass of zirconium hydroxide (Examples 2 and 3) are batteries using nonaqueous electrolytes not containing the zirconium salt (Comparative Example). Compared with 1), in the 45 ° C. cycle test, the capacity retention rate is large, and it is understood that the charge / discharge cycle performance is excellent.

  The present invention can be applied to non-aqueous electrolyte storage elements such as non-aqueous electrolyte secondary batteries used as power sources for personal computers, electronic devices such as communication terminals, and automobiles.

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Electrode body 3 Battery container 4 Positive electrode terminal 4 'Positive electrode lead 5 Negative electrode terminal 5' Negative electrode lead 20 Power storage unit 30 Power storage device

Claims (5)

A fluorinated cyclic carbonate, and
A non-aqueous electrolyte containing a zirconium salt or calcium salt having a solubility in water of 0.01 g / 100 mL or more.   The non-aqueous electrolyte according to claim 1, wherein the zirconium salt is zirconium hydroxide and the content of zirconium hydroxide is less than 2 mass% with respect to the non-aqueous electrolyte.   The nonaqueous electrolyte according to claim 1, wherein the calcium salt is calcium hydroxide, and the content of calcium hydroxide is less than 2 mass% with respect to the nonaqueous electrolyte.   The nonaqueous electrolyte electrical storage element using the nonaqueous electrolyte in any one of Claims 1-3. A fluorinated cyclic carbonate, and
The manufacturing method of the nonaqueous electrolyte electrical storage element containing the zirconium salt or calcium salt whose solubility to water is 0.01 g / 100mL or more.

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