JP2016131081A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery with a high energy density, capable of preventing the elusion of a positive electrode active material into an electrolyte even if a metal chloride is used as a positive electrode active material.SOLUTION: A secondary battery includes a negative electrode active material capable of taking in lithium ions by charging/discharging, a positive electrode having a positive electrode active material containing a metal chloride, and a nonaqueous electrolyte containing a lithium salt and a nonaqueous solvent. At least one kind of the nonaqueous solvent contains a halogenide of a carboxylic acid ester.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rechargeable battery that can be repeatedly charged and discharged.

In recent years, the demand for batteries has increased due to the downsizing, high performance, and portability of various electronic devices. Accordingly, the improvement and development of batteries are becoming increasingly active. New application areas for batteries are also expanding.
Nickel has a high energy density with the rapid spread of portable devices since around 1990 in the consumer secondary battery market, which was only lead batteries and nickel cadmium secondary batteries (hereinafter referred to as Ni / Cd secondary batteries). Hydrogen secondary batteries (hereinafter referred to as Ni / MH secondary batteries) and lithium ion secondary batteries (hereinafter referred to as Li ion secondary batteries) have been developed and rapidly spread mainly for power supplies for small portable electronic devices As a result, it has come to occupy a significant share (see, for example, Non-Patent Document 1).

By the way, in recent years, environmental protection, reduction of environmental load, and effective use of material energy have been screamed, and the importance of secondary batteries that can be reused more than disposable primary batteries has increased. In addition, from the viewpoint of reducing environmental impact, automobiles are also expected to be hybrid cars and electric cars, and in particular, application of Li ion secondary batteries having the highest energy density among commercial batteries is progressing. In addition, there is a strong demand for application to industrial batteries instead of lead batteries, and development of large batteries for Li-ion secondary batteries is underway. At the same time, there is an increasing demand for a high energy density secondary battery that surpasses the current Li ion secondary battery in order to achieve higher performance and wider application range.
Therefore, a search for a new secondary battery system is being performed in parallel with the increase in energy density by searching for a positive electrode active material and a negative electrode material of a Li ion secondary battery.

  The Li ion secondary battery constitutes a battery reaction by an intercalation reaction. In the intercalation reaction, guest Li ions are inserted into and desorbed from the active material of the negative electrode and the positive electrode in a host material such as carbon such as graphite and a transition metal oxide. As long as the host material is stable in the electrolytic solution and the crystal structure having a site accommodating Li does not collapse due to insertion / desorption, excellent charge / discharge cycle stability can be expected.

  However, since the proportion of the weight and volume occupied by the host material is relatively large, the proportion of the active material in the battery is reduced, limiting the increase in energy density, making it difficult to meet the demand for further energy density increase. It has become to.

As a measure for increasing the energy density, a Li ion secondary battery that constitutes a battery reaction by a conversion reaction has been proposed (see, for example, Non-Patent Document 1). This battery reaction is represented by the following reaction formula (1).
^{_{M a X b + nbLi + +}} nbe - ← → aM + bLi n X ··· (1)
Here, M represents a transition metal, and X represents an anionic species. N represents the oxidation state of the anionic species.

  As shown in the reaction formula (1), in the Li ion secondary battery based on the conversion reaction, not only the host material provides an active material accommodating site, but also the material itself can participate in the oxidation-reduction reaction. For this reason, higher energy density than the Li ion secondary battery by the intercalation reaction can be realized.

Further, as shown in the reaction formula (1), in the Li ion secondary battery by the conversion reaction, the positive electrode can be configured as (aM + bLi _n X). That is, since Li can be held in the positive electrode, the negative electrode material is not limited to only lithium metal. Therefore, the negative electrode may be any material that can occlude and release lithium, and in addition to lithium metal, carbon materials (such as graphite), silicon (such as silicon), germanium, and tin can be used.

  Thus, the Li ion secondary battery by the conversion reaction includes transition metal oxides (Non-Patent Document 1 and Non-Patent Document 2) and transition metal fluorides (Non-Patent Document 1, Non-Patent Document 3 and Non-Patent Document 4). It has been widely studied mainly.

  Here, when charging / discharging the battery, the difference between the charge voltage and the discharge voltage (electrochemical polarization) should be as small as possible. When the electrochemical polarization is small, charging / discharging is possible at a potential close to the standard electrode potential, so that the discharge capacity is high and surplus energy during charging can be reduced. For this reason, thermal damage to the battery can be suppressed and the capacity can be increased.

  However, when transition metal oxides and transition metal fluorides are used as positive electrode active materials, large electrochemical polarization is a major problem (for example, Non-Patent Document 1).

  In addition, in a Li ion secondary battery by a conversion reaction using transition metal oxide and transition metal fluoride as a positive electrode active material, it is difficult to realize charge / discharge at a high rate. The Li ion battery by the intercalation reaction can sufficiently charge and discharge 1C. However, it is difficult to realize charge and discharge equivalent to 1C in a Li-ion battery based on a conversion reaction (for example, Non-Patent Document 1).

  In a Li-ion secondary battery to which a conversion reaction is applied, there is a method of forming a positive electrode active material into fine particles as one of the strikers for suppressing electrochemical polarization and realizing charge / discharge at a high rate. Thereby, since the reaction overvoltage in the conversion reaction is reduced, a battery system with a small electrochemical polarization can be constructed. Further, by making the particles finer, the reaction area between the metal and the lithium salt is improved, and an increase in charge / discharge capacity and an improvement in cycle characteristics can be realized.

It has been reported that there is an optimum particle size for each active material in order to improve cycle characteristics by making the active material finer. For example, according to Non-Patent Document 2, in the case of Cu ₂ O with a particle size of 1 μm, the capacity is stable (about 360 mAh / g) even at the 100th cycle, whereas Cu ₂ O with a particle size of 0.15 μm is stable. In this case, the capacity gradually decreases, and it can be confirmed that the capacity has decreased to about 160 mAh / g in the 60th cycle.

  Moreover, in a Li ion secondary battery to which a conversion reaction is applied, application of transition metal chloride is one of the strikes for suppressing electrochemical polarization and realizing charge / discharge at a higher rate. In the case of transition metal chlorides, the binding energy of M-Cl is low. For this reason, it can be said that the electrochemical polarization in charging / discharging is kept low, and charging / discharging at a high rate can be realized.

In the case of a secondary battery using a conversion reaction with copper, cupric chloride and lithium ions, the battery reaction is represented by the following reaction formula.
← Charge Discharge →
The positive _{electrode: CuCl 2 + 2Li + + 2e} - ← → Cu + 2LiCl
Negative: 2Li ← → 2Li + + 2e -
All reactions: CuCl ₂ + 2Li ← → Cu + 2LiCl

The reaction of the secondary battery using the conversion reaction of copper and cupric chloride with lithium ions proceeds as follows. First, consider the case where the positive electrode is Cu. In this battery reaction, an electrolyte includes a negative electrode containing Cu and lithium as a positive electrode active material, and LiCl is contained in the positive electrode as a lithium salt. In this battery system, starting from a charging reaction, Cu + LiCl → CuCl + Li ⁺ + e ⁻ , Cu + 2LiCl → CuCl ₂ + 2Li ⁺ + 2e ⁻ and CuCl + LiCl → CuCl ₂ + Li ⁺ + e ⁻ occur, and Cu is oxidized to CuCl ₂ by LiCl. Thereafter, as a discharge reaction, CuCl ₂ + Li ⁺ + e ⁻ → CuCl + LiCl, CuCl ₂ + 2Li ⁺ + 2e ⁻ → Cu + 2LiCl and CuCl + Li ⁺ + e ⁻ → Cu + LiCl occur, and CuCl ₂ is reduced to Cu by Li ⁺ . By this oxidation-reduction reaction, the battery system functions as a secondary battery.

Next, consider the case where the positive electrode active material is cupric chloride (CuCl ₂ ). This battery configuration includes a negative electrode containing cupric chloride (CuCl ₂ ) and lithium as a positive electrode active material in an electrolyte. In this battery system, starting from a discharge reaction, CuCl ₂ + Li ⁺ + e ⁻ → CuCl + LiCl, CuCl ₂ + 2Li ⁺ + 2e ⁻ → Cu + 2LiCl and CuCl + Li ⁺ + e ⁻ → Cu + LiCl occur, and CuCl ₂ is reduced to Cu by Li ⁺ . . Thereafter, Cu + LiCl → CuCl + Li ⁺ + e ⁻ , Cu + 2LiCl → CuCl ₂ + 2Li ⁺ + 2e ⁻ and CuCl + LiCl → CuCl ₂ + Li ⁺ + e ⁻ occur as charging reactions, and Cu is oxidized to LiCl ₂ by LiCl. By this oxidation-reduction reaction, the battery system functions as a secondary battery.

A secondary battery using a conversion reaction between copper and cupric chloride and lithium ions is useful because of its high theoretical capacity per weight. Its theoretical capacity is 399 mAh / g- ^CuCl2, which is larger than that of a lithium ion battery (270 mAh / g). Further, since the theoretical potential of the battery is as high as 3.07 V (vs. Li / Li ⁺ ), its weight energy density is as large as 1112 Wh / kg ^{− (Cu + 2LiCl)} .

  Thus, Li ion secondary batteries based on the conversion reaction between metals and metal chlorides and lithium ions have high energy density, and can be applied to negative electrode materials such as graphite and silicon in addition to lithium metal, and electrochemically. There is usefulness that polarization is small and charging / discharging at a high rate is possible.

  However, the metal chloride has a property of being easily dissolved in the electrolytic solution. For this reason, self-discharge becomes large and it becomes a big subject that it becomes difficult to apply as a secondary battery.

For example, studies on lithium ion conversion reaction using cobaltous chloride (CoCl ₂ ) as a positive electrode have been reported (Non-patent Document 5). According to Non-Patent Document 5, electrolysis in which 1.0 M lithium hexafluorophosphate was dissolved in an organic solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1: 1: 1. Liquid is used. Further, pellets mixed at a ratio of CoCl ₂ : carbon black (CB): polytetrafluoroethylene = 65: 25: 10 are used as the positive electrode material, and lithium metal is used for the negative electrode. Referring to the charge / discharge curve (charge / discharge rate: 0.2 C) disclosed in this document, a discharge plateau is confirmed in the vicinity of 1.4 V (vs. Li / Li ⁺ ) in the first cycle. The theoretical potential of the electrode reaction CoCl ₂ + 2Li ⁺ + 2e ⁻ ← → Co + 2LiCl is 2.59 V (vs. Li / Li ⁺ ), and it can be confirmed that the discharge plateau is far away from this theoretical potential. For this reason, there is a high possibility that the discharge plateau near 1.4 V (vs. Li / Li ⁺ ) is not caused by the lithium ion conversion reaction using cobalt chloride (CoCl ₂ ) as the positive electrode. Further, when the charge curve is referred to, a clear plateau is hardly confirmed, and a clear charge / discharge plateau is not confirmed after the second cycle. Therefore, an electrolytic solution in which 1.0 M lithium hexafluorophosphate is dissolved in an organic solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1: 1: 1 is applied. Even in this case, it is confirmed that the lithium ion conversion reaction using cobaltous chloride (CoCl ₂ ) as a positive electrode hardly occurs.

A positive electrode prepared by spraying a solution in which anhydrous CuCl ₂ is dissolved in an ethanol solvent onto mesoporous carbon and removing the ethanol solvent by vacuum drying is used as a measure for the solubility of the metal chloride in the electrolytic solution. Thus, there has been reported an example in which the fixation of copper chloride to the positive electrode is promoted to suppress the solubility in the electrolyte (Non-patent Document 6).

Referring to the charge / discharge curve shown in Non-Patent Document 6, it is almost impossible to find a plateau corresponding to the theoretical potential of the conversion reaction between copper and cupric chloride and lithium ions. The theoretical potentials of the electrode reactions CuCl ₂ + Li ⁺ + e ⁻ ← → CuCl + LiCl, CuCl ₂ + 2Li ⁺ + 2e ⁻ ← → Cu + 2LiCl and CuCl + Li ⁺ + e ⁻ ← → Cu + LiCl are 3.41, 2.74 V and 3.07 V, respectively. . Since almost no plateau can be found in the vicinity of these potentials, it is considered that the conversion reaction between copper and cupric chloride and lithium ions hardly occurs.

  As another measure for the solubility of the metal chloride in the electrolytic solution, there is application of a conventionally known fluorinated carbonate or fluorinated ether (Patent Document 1).

  The inventors have evaluated the secondary battery characteristics using many non-aqueous electrolytes that use a conventionally known fluorinated carbonate or fluorinated ether recommended in Patent Document 1 as a solvent. However, even when these fluorinated carbonates and fluorinated carbonate derivatives were applied, the effect of elution of the active material was not improved. In addition, when fluorinated ethers and fluorinated ether derivatives were applied, in addition to the effect of elution of the active material, the support salt solubility was poor.

  On the other hand, according to the study by the inventors, a non-aqueous solution composed of an electrode containing a substance from which lithium ions are inserted and released in the negative electrode, an electrode containing a halide in the positive electrode active material, a lithium salt and a fluorinated carbonate ester. In a secondary battery using an electrolytic solution, there is a problem that when a conventionally used battery case made of stainless steel (SUS) is used, the battery voltage is drastically lowered, and the capacity drop due to charging / discharging becomes severe.

  In general Li ion secondary batteries, a battery case using a lightweight aluminum alloy case instead of a SUS case has been reported in order to cope with higher voltage and higher energy density (for example, patents). Reference 2 and Patent Reference 3). A battery case is also known in which a lid is sealed with a laser in order to complete sealing with an aluminum alloy case (see, for example, Patent Document 4). As described above, development of a battery case with high energy density, high voltage, chemical stability and high reliability suitable for a secondary battery using a highly reactive halide as an active material has become a major issue. .

JP 2004-047416 A JP-A-10-180438 JP 2000-011964 A JP 2000-123822 A

J. Cabana, L. Monconduit, D. Larcher, and MR Palacin (2010) “Beyond Intercalation-Based Li-Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions”, Adv. Mater., Vol. 22, pp. E170-E192. P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, and JM Tarascon (2000) “Nano-sized transition-metal oxides as negative-electrode materials for lithium-ion batteries”, Nature, vol. 407 (28) , pp. 496-499 H. Arai, S. Okada, Y. Sakurai, and J. Yamaki (1997) “Cathode performance and voltage estimation of metal trihalides”, J. Power Sources, vol. 68, pp. 716-719. F. Badway, N. Pereira, F. Cosandey, and GG Amatucci (2003) “Carbon-Metal Fluoride Nanocomposites Structure and Electrochemistry of FeF3: C”, J. Electrochem. Soc., Vol. 150 (9), pp. A1209 -A1218. J. L. Liu, W. J. Cui, C. X. Wang, and Y. Y Xia (2011) “Electrochemical reaction of lithium with CoCl2 in nonaqueous electrolyte”, Electrochem. Commun., Vol. 13, pp. 269-271. T. Li, Z. X. Chen, Y. L. Cao, X. P. Ai, and H. X. Yang (2012) “Transition-metal chlorides as conversion cathode materials for Li-ion batteries”, Electrochim. Acta, vol. 68, pp. 202-205.

  The present invention provides a high energy density secondary battery capable of preventing elution of a positive electrode active material into an electrolytic solution in a secondary battery using a conversion reaction between metal and metal chloride and lithium ions. The task is to do.

  It is another object of the present invention to provide a high energy density secondary battery using a metal chloride as a positive electrode active material and having a positive electrode case that is chemically stable with respect to a redox reaction of the positive electrode active material.

In order to solve the above problems, the present invention proposes the following means.
A secondary battery according to one embodiment of the present invention includes a negative electrode including a negative electrode active material capable of releasing lithium ions by an initial discharge and taking in and releasing lithium ions by subsequent charge and discharge, and a positive electrode active including a metal chloride. A positive electrode having a substance, and a non-aqueous electrolyte solution including a lithium salt and a non-aqueous solvent, wherein at least one of the non-aqueous solvents contains a halide of a carboxylic acid ester, and starts from discharge. .

  In one embodiment of the present invention, the positive electrode active material is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd. , Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, and at least one metal chloride.

In one embodiment of the present invention, the positive electrode active material includes at least one of FeCl ₂ , BiCl ₃ , and CuCl ₂ .

  In one embodiment of the present invention, the metal chloride contained in the positive electrode active material is in the form of particles, and the particle size thereof is 1 μm or less.

In one embodiment of the present invention, the negative electrode active material includes metallic lithium, a carbon material in which lithium is inserted, a Si-Li alloy, a Sn-Li alloy, a TiO ₂ titanium oxide that incorporates lithium, Li ₄ Ti ₅ O ₁₂ and hetero-element-substituted lithium titanium oxide, metal oxide incorporating lithium, amorphous tin composite oxide incorporating lithium, metal nitride incorporating lithium, metal phosphide incorporating lithium, lithium Low-grade oxide of silicon incorporated, conversion anode material incorporating lithium, Sn-M (however, M = Ni, Fe, Co, Cu, V, Ag, Sb) alloys incorporating lithium, composite materials incorporating lithium Among them, at least one is included.

  In one embodiment of the present invention, the negative electrode active material includes at least one of metallic lithium, a carbon material into which lithium is inserted, a Si—Li alloy, and a Sn—Li alloy.

  A secondary battery according to one embodiment of the present invention includes a negative electrode including a negative electrode active material capable of capturing lithium ions by first charging and releasing and capturing lithium ions by subsequent charging and a positive electrode active including metal and lithium chloride. A positive electrode having a substance; and a non-aqueous electrolyte solution including a lithium salt and a non-aqueous solvent, wherein at least one of the non-aqueous solvents includes a halide of a carboxylic acid ester, and starts from charging. .

  In one embodiment of the present invention, the positive electrode active material is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd. , Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, and Bi, at least one metal is included.

  In one embodiment of the present invention, the positive electrode active material includes at least one of Fe, Bi, and Cu.

  In one embodiment of the present invention, the metal chloride contained in the positive electrode active material is in the form of particles, and the particle size thereof is 1 μm or less.

In one embodiment of the present invention, the negative electrode active material is a carbon material, Si, Sn, TiO ₂ -based titanium oxide, metal oxide, amorphous tin composite oxide, metal nitride, metal phosphide, or lower of silicon. Among oxides, conversion anode materials, Sn-M (however, M = Ni, Fe, Co, Cu, V, Ag, Sb) alloys, Sn-Si-O based composite materials, Sn-Co-C based composite materials , Including at least one.

  In one embodiment of the present invention, the negative electrode active material includes at least one of a carbon material, Si, and Sn.

In one embodiment of the present invention, the halide of the carboxylic acid ester is a halide in which part or all of hydrogen in CHX ₂ COOR (where X = halogen atom, R = hydrocarbon group) is halogenated. It is characterized by.

In one embodiment of the present invention, the halide of the carboxylic acid ester is CHF ₂ COOCH ₃ (methyl-2,2-difluoroacetate).

In one aspect of the present invention, the lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF 6, LiTaF 6, LiNbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (CF 3 SO 2) 2 , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiBF ₃ (C ₂ F ₅ ), LiB (C ₆ F ₅ ) ₄ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiClO ₄ and at least one of LiB (C ₂ O ₄ ) ₂ is characterized.

In one embodiment of the present invention, the lithium salt includes at least one of LiPF ₆ , LiBF ₄ , and LiAsF ₆ .

  A secondary battery according to one embodiment of the present invention includes a negative electrode including a negative electrode active material capable of taking in lithium ions by charge and discharge, a positive electrode including a positive electrode active material including a metal halide, and a positive electrode case containing the positive electrode. A non-aqueous electrolyte containing a lithium salt and a non-aqueous solvent, and the inner surface of the positive electrode case is insoluble in the non-aqueous electrolyte, and the redox reaction of the positive electrode active material and the positive electrode active An inactive layer made of a material that is chemically inactive with respect to the positive electrode constituent material other than the substance is formed.

  In one aspect of the present invention, the positive electrode current collector is disposed between the inner surface of the positive electrode case and the positive electrode, and the inert layer is further formed on the surface of the positive electrode current collector. It is characterized by that.

  In one aspect of the present invention, the inactive layer is made of Al or an Al alloy.

  In one aspect of the present invention, the inactive layer is made of conductive carbon.

  In one aspect of the present invention, the inactive layer is made of Pt or a Pt alloy.

  In one aspect of the present invention, the inert layer is made of a ternary copolymer synthetic rubber having a C double bond in the polymer main chain.

  In one aspect of the present invention, the synthetic rubber constituting the inert layer is an ethylene / propylene / diene terpolymer.

  According to the present invention, even when a metal chloride is used as the positive electrode active material, the elution of the positive electrode active material into the electrolyte solution can be prevented, and a high energy density secondary battery that can be charged and discharged at a high rate is obtained. Can be provided.

  The present invention also provides a secondary battery capable of suppressing electrochemical polarization in an electrode reaction between copper chloride and lithium ions while using an electrolytic solution with low copper chloride solubility. be able to.

  In addition, according to the present invention, it is possible to provide a high energy density secondary battery including a positive electrode case that uses a halide as a positive electrode active material and is chemically stable with respect to a redox reaction of the positive electrode active material. .

It is a schematic sectional drawing which shows an example of a structure of the Li ion secondary battery of this invention. It is the graph which showed the initial stage discharge voltage profile of Li ion secondary battery of verification example 1-2. It is the graph which showed transition of the discharge capacity to the 3rd cycle of Li ion secondary battery of verification example 1-2. It is the graph which showed the change of the discharge capacity by the repetition of charging / discharging of the Li ion secondary battery of the verification example 1-3, and a charge capacity. It is the graph which showed the charging / discharging curve of the Li ion secondary battery of the verification example 1-3. It is a graph which shows the change of the discharge capacity by the self-discharge of verification example 1-5. It is a graph which shows the change of the weight energy density by the self-discharge of the verification example 1-5. It is a graph which shows the discharge curve according to the down time of verification example 1-6. It is a graph which shows the discharge curve according to the down time of verification example 1-6. It is a graph which shows the discharge curve according to the down time of verification example 1-6. It is a graph which shows the discharge curve at the time of changing the rate of the Li ion secondary battery of the verification example 1-7. It is a graph which shows the discharge curve of the Li ion secondary battery of verification example 1-8. It is a graph which shows the measurement result of the circuit voltage to 800 hours of the verification example 2-1. It is a graph which shows the measurement result of the circuit voltage to 800 hours of the verification example 2-2. It is a graph which shows a measurement result about the time-dependent change of the battery voltage of verification example 2-4.

  The secondary battery of the present invention will be described below with reference to the drawings. The following embodiments are specifically described for better understanding of the gist of the invention, and do not limit the configuration of the present invention unless otherwise specified. In addition, the specific substance names described in the following embodiments are examples of usable substances unless otherwise specified, and each component is not limited to these substances. . In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a Li ion secondary battery which is a secondary battery of the present invention.
The Li-ion secondary battery (secondary battery) 10 of this embodiment includes a battery case 13 including a positive electrode case 11 and a negative electrode case 12 that are engaged via a gasket 19 made of an insulating material. The internal space of the battery case 13 is partitioned by the separator 14 into a positive electrode side space E1 and a negative electrode side space E2. In the positive electrode side space E1 surrounded by the positive electrode case 11 and the separator 14, a positive electrode 15 made of a single positive electrode active material or a positive electrode mixture containing a positive electrode active material, and a positive electrode current collector 16 are arranged. The positive electrode mixture may contain a binder and a conductive auxiliary agent in addition to the positive electrode active material.

  Further, in the negative electrode side space E2 surrounded by the negative electrode case 12 and the separator 14, a negative electrode 17 made of a negative electrode active material alone or a negative electrode mixture containing a negative electrode active material, and a negative electrode current collector 18 are arranged. . The negative electrode mixture may contain a binder and a conductive additive in addition to the negative electrode active material. The separator 14 is impregnated with a non-aqueous electrolyte.

  An inert layer 22 is formed on the inner surface 11 a of the positive electrode case 11. An inert layer 22 is also formed on the outer surface 16 a of the positive electrode current collector 16.

The Li ion secondary battery 10 having such a configuration is started to be used from a charged state, for example. That is, when the Li ion secondary battery 10 is manufactured using cupric chloride (CuCl ₂ ) as the positive electrode active material of the Li ion secondary battery 10 and a material containing Li as the negative electrode active material, the Li ion secondary battery 10 is manufactured. The secondary battery 10 is charged immediately after manufacture. During discharge (during use), as is well known, Li ions escape from the negative electrode active material into the electrolytic solution and are taken into the positive electrode active material through the separator 14. Electric power is taken out in the process of such movement of Li ions. Further, at the time of charging, Li ions are extracted from the positive electrode active material into the electrolytic solution with the movement of electrons by an external charging power source, and are taken into the negative electrode active material through the separator 14. Discharge-charge can be repeated by such movement of Li ions.

Next, each configuration of the Li ion secondary battery (secondary battery) 10 of the present embodiment will be described in more detail.
In the present embodiment, as the nonaqueous electrolytic solution impregnated in the separator 14, a carboxylic acid halide (or fluorinated carboxylic acid ester) is used as a nonaqueous solvent. The halide of the carboxylic acid ester is a halide in which part or all of hydrogen of CHX ₂ COOR (where X = halogen atom, R = hydrocarbon group) is halogenated. In this embodiment, at least carboxylic acid A compound in which a part of the hydrogen of the alkyl group constituting is substituted with a halogen is used.

  By substituting some or all of the hydrogen atoms of the alkyl group constituting the carboxylic acid with fluorine, the carboxylic acid ester is prevented from being decomposed by Li by generating a —OH (hydroxyl group) by the keto-enol reaction. be able to.

As a specific example of the non-aqueous solvent constituting the non-aqueous electrolyte,
CHF ₂ COOCH ₃ (methyl-2,2-difluoroacetate), CHF ₂ COOCH ₂ CH ₃ (ethyl-2,2-difluoroacetate), CHF ₂ COOCH ₂ CH ₂ CH ₃ (propyl-2,2-difluoroacetate) CHF ₂ COOCH ₂ CH ₂ CH ₂ CH ₃ (butyl-2,2-difluoroacetate), CHCl ₂ COOCH ₃ (methyl-2,2-dichloroacetate), CHBr ₂ COOCH ₃ (methyl-2,2-dibromoacetate) ), Methyl pentafluoropropionate (CF ₃ CF ₂ COOCH ₃ ), ethyl pentafluoropropionate (CF ₃ CF ₂ COOC ₂ H ₅ ), methyl heptafluoroisobutyrate ((CF ₃ ) ₂ CFCOOCH ₃ ) hepta-n- Methyl butyrate (CF ₃ CF ₂ CF ₂ COOCH ₃ ), hepta-n-ethyl butyrate (CF ₃ CF ₂ CF ₂ COOC ₂ H ₅ ), ethyl heptafluorovalerate (CF ₃ (CF ₂ ) ₃ COOC ₂ H ₅ ) , pentadecyl fluoro caprylate ethyl _{(CF 3 (CF 2) 6} COOC 2 H 5) etc. It can be mentioned. The nonaqueous solvent of the nonaqueous electrolytic solution is not limited to these compounds as long as part or all of the hydrogen of the alkyl group constituting the carboxylic acid of the carboxylic acid ester is a halide.

  In the present embodiment, the carboxylic acid ester fluoride used as the non-aqueous solvent of the non-aqueous electrolyte is conventionally used as a non-aqueous electrolyte. For example, the fluorinated carbonate or fluorination disclosed in Patent Document 1 is used. It is a very difficult solvent to guess from ether. That is, as the conventionally used fluorinated carbonate, it is easily assumed that ethylene carbonate, propylene carbonate, dimethyl carbonate, and methyl ethyl carbonate are frequently used as the non-aqueous solvent of the non-aqueous electrolyte for Li ion secondary batteries. Fluorinated products of ester compounds such as diethyl carbonate, γ-butyrolactone and γ-valerolactone. These compounds have been used as effective non-aqueous solvents constituting electrolytes for Li ion secondary batteries.

In contrast, the carboxylic acid ester easily generates -OH (hydroxyl group) by the keto-enol reaction, which reacts with the Li ⁺ ion and decomposes. It was never applied to the solvent.

  However, the inventors have verified that some or all of hydrogen in solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate disclosed in Patent Document 1 have been fluorinated. According to the above, dissolution of the metal or metal chloride as the positive electrode active material could hardly be suppressed, and the battery characteristics were not good. That is, non-aqueous electrolyte solvents that can suppress the dissolution of chlorides by fluorination have been found among compounds that can be easily inferred from these carbonic acid ester compounds that are effective for Li-ion secondary batteries. Absent.

  In the non-aqueous solvent of the non-aqueous electrolyte of the present embodiment, the above-described carboxylic acid is used as long as the dissolution of the metal or metal chloride constituting the positive electrode active material is not promoted for the control and adjustment of viscosity, ion mobility and the like. It is also possible to add an organic solvent other than the halide of the ester. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, γ-valerolactone, methyl acetate, ethyl acetate, etc. used for non-aqueous electrolyte of Li ion secondary battery Carbonates, ester compounds and ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane In addition, an organic solvent such as acetonitrile, dimethyl sulfoxide, 1-methyl-2-pyrrolidinone (N-methylpyrrolidone), 1,3-methyl-2-imidazolidinone can also be mixed.

  That is, a non-aqueous solvent can be used by using one or more aprotic solvents that can withstand the potential of the Li ion secondary battery or can be stabilized by forming an ion conductive film at the electrode interface. Note that organic solvents other than those described above may be used as long as the solubility of the positive electrode active material is not significantly increased, and the present invention is not limited to these compounds.

Further, the non-aqueous electrolyte of the present embodiment contains a lithium salt of Lewis acid that can supply a sufficient amount of Li ions necessary for the battery reaction. Specific examples of such lithium salt, fluorine-containing salts _{LiPF 6, LiBF 4, LiAsF 6} , LiSbF 6, LiTaF 6, LiNbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (CF 3 SO 2 ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiBF ₃ (C ₂ F ₅ ), LiB (C ₆ F ₅ ) ₄ , LiPF ₃ (C ₂ F ₅ ) ₃ And LiClO ₄ which is a chlorine-containing salt and LiB (C ₂ O ₄ ) ₂ which is a carboxylic acid-containing salt.

The non-aqueous electrolyte of this embodiment is composed of a non-aqueous solvent containing such a carboxylate halide and a solute of lithium salt of these Lewis acids. In the present embodiment, methyl-2,2-difluoroacetate (CHF ₂ COOCH ₃ ), which is a fluoride of carboxylic acid ester, is used as the non-aqueous solvent constituting the non-aqueous electrolyte. When a non-aqueous electrolyte composed of such a compound is used, when a metal chloride is used as the positive electrode active material as described later, the excellent characteristics of the Li ion secondary battery are exhibited. In addition to methyl-2,2-difluoroacetate and a lithium salt, LiCl may be further added as a material constituting the non-aqueous electrolyte.

  The content of the lithium salt, which is a solute constituting the nonaqueous electrolytic solution, is generally 1 mol / L with respect to the nonaqueous solvent. However, if the required battery characteristics can be satisfied, the content of the lithium salt is particularly limited. Not. Similarly, lithium chloride is not limited as long as the required battery characteristics can be satisfied at a saturation dissolution amount or less. Further, in the nonaqueous electrolytic solution of the present embodiment, it is preferable to suppress the water content to 100 ppm or less. However, it is not limited to these conditions as long as the required battery characteristics are obtained.

  In the case of a positive electrode having a positive electrode active material containing a metal chloride, the positive electrode active material of the present embodiment is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, etc. can be used. Also, chlorides such as semi-metal Si, Ge, As, Sb and Te can be used. Furthermore, chlorides with non-metallic elements can be used, and chlorides such as P, S, and Se can also be used as positive electrode active materials. These compounds are premised on being the compounds in the highest oxidation state (ie, charged state).

In this embodiment, in particular, cupric chloride (CuCl ₂ ), bismuth chloride (BiCl ₃ ), and ferric chloride (FeCl ₂ ) can be mentioned.

    If these metal chlorides are in the form of particles, the reaction overvoltage in the conversion reaction is reduced, so that a battery system with a small electrochemical polarization can be constructed. Further, by making the particles finer, the reaction area of the metal chloride can be improved, and the charge / discharge capacity can be increased and the cycle characteristics can be improved. In the positive electrode of the present embodiment, the particle size of the metal chloride is preferably 1 μm or less, and preferably 0.1 μm or less. However, it is not limited to these conditions as long as the required battery characteristics are obtained.

  Moreover, it can also be set as the structure containing the element mentioned above and lithium chloride (LiCl) as another positive electrode active material. The Li ion secondary battery 10 including these metals and lithium chloride as a positive electrode active material is in a discharged state.

  In the present embodiment, when the above-described elements and LiCl are included in the positive electrode active material, it is preferable to use a metal having a low oxidation state. In particular, Cu and Bi can be mentioned as preferable positive electrode active materials. The content ratio of each element described above and LiCl may be, for example, about 1: 2 in molar ratio. The content ratio of each element and LiCl described above is preferably contained in a molar ratio of, for example, 1: 2. The content ratio of these elements and metal chlorides constituting the positive electrode active material can be appropriately constituted in consideration of elution into the non-aqueous electrolyte and the like in an appropriate ratio. That is, the secondary battery of the present invention is not limited to these ratios as long as the secondary battery can exhibit excellent characteristics.

  As metal elements in the positive electrode in the present embodiment, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, and the like can be used. Semimetals such as Si, Ge, As, Sb, and Te can also be used. Note that chlorides with nonmetallic elements can be used, and P, S, Se, and the like can also be active materials. These compounds are premised on being the compounds in the lowest oxidation state (ie, discharge state). These elements are preferably in the form of particles. Since the reaction overvoltage in the conversion reaction with Li ions is reduced, a battery system with small electrochemical polarization can be constructed. Further, by making the particles finer, the reaction area between the metal and the lithium salt is improved, and an increase in charge / discharge capacity and an improvement in cycle characteristics can be realized. In the positive electrode of this embodiment, the particle size of these elements is preferably 1 μm or less, and preferably 0.1 μm or less. However, it is not limited to these conditions as long as the required battery characteristics are obtained.

  In the present embodiment, examples of the positive electrode active material include copper (Cu) and lithium chloride (LiCl), bismuth (Bi) and lithium chloride (LiCl), and iron (Fe) and lithium chloride (LiCl).

  In the present embodiment, lithium chloride may be contained in any of the positive electrode, the nonaqueous electrolyte, and the negative electrode. However, since it is difficult to include a large amount of lithium chloride in the non-aqueous electrolyte, it is preferable to include lithium chloride in the positive electrode.

  It has been confirmed that by charging the Li ion secondary battery 10 using such a positive electrode active material, a chloride in the highest oxidation state can be effectively produced. That is, by using the cathode active material having a lower oxidation state, the Li ion secondary battery 10 according to the present embodiment including the cathode active material can be shipped in a lower charged state, thereby further improving safety during transportation. be able to.

  Moreover, in this embodiment, when each element mentioned above and LiCl are included in a positive electrode active material, it is preferable to use a metal with a low oxidation state. In particular, Cu and Bi can be mentioned as preferable positive electrode active materials. The content ratio of Cu and LiCl should just be about 1: 2 by molar ratio, for example. The content ratio of these elements and chlorides constituting the positive electrode active material can be appropriately constituted in consideration of elution into the non-aqueous electrolyte and the like in an appropriate ratio. That is, the secondary battery of the present invention is not limited to these ratios as long as the secondary battery can exhibit excellent characteristics.

  The positive electrode 15 of the present embodiment includes a positive electrode active material composed of the above-described elements and LiCl, a conductive carbon such as acetylene black (hereinafter referred to as AB), ketjen black and the like, and polyvinylidene fluoride ( Hereinafter, a binder such as PVdF) or polytetrafluoroethylene (Teflon (registered trademark)), and a dispersant such as N-methylpyrrolidone (hereinafter referred to as NMP) that disperses these powders as necessary. The slurry is used to prepare a slurry, which is applied to the positive electrode current collector 16 and dried, cut into a predetermined size, and used as the positive electrode 15.

  Lithium is used as the negative electrode active material, and the negative electrode active material is formed of a material capable of taking in and releasing Li ions with charge and discharge. Such a negative electrode active material can provide a stable and high-performance negative electrode active material by forming an appropriate film through which the non-aqueous electrolyte of this embodiment is decomposed by a non-progressive reaction and allows Li ions to pass therethrough.

When the positive electrode is composed of a positive electrode active material containing metal chloride, the negative electrode active material can be selected from graphite such as MPG (natural graphite) and IGC (artificial graphite), hard carbon, low crystalline carbon, and graphitization. Carbon materials such as coke, nanocarbon, TiO ₂ -based titanium oxide, Li ₄ Ti ₅ O ₁₂ and different elements substituted lithium titanium oxide, niobium pentoxide (Nb ₂ O ₅ ), tungsten oxide (WO ₂ ) , Oxides such as molybdenum oxide (MoO ₂ ), amorphous tin composite oxide (SnB _x P _y O _z (x = 0.44 to 0.6, y = 0.6 to 0.4, z = (2 + 3x + 5y) / 2 )), Nitrides such as Li ₇ MnN ₄ , Li ₃ FeN ₂ , Li ₁₅ Cr ₂ N ₉ , Li _2.6 Co _0.4 N, phosphides such as FeP ₂ , MnP ₄ and CoP ₃ , lower oxides of silicon (LixSiOy (X ≧ 0.2>y> 0)), conversion negative electrode materials such as CoO, NiO, FeO, Sn-M (M = Ni, Fe, Co, Cu, V, Ag, Sb) alloys, and further as composite materials, Sn-Si-O compound Materials, or the like can be used Sn-Co-C composite material. Examples of the negative electrode active material of the Li ion secondary battery 10 of the present embodiment include lithium metal or lithium alloys such as carbon, silicon, and tin incorporating lithium.

When the positive electrode is composed of a positive electrode active material containing metal and lithium chloride, the negative electrode active material includes carbon materials (MPG (natural graphite), IGC (artificial graphite)) such as graphite, hard carbon, and low crystalline carbon. , Graphitizable coke, nanocarbon, etc., Si, Sn, TiO ₂ titanium oxide, metal oxide (niobium pentoxide (Nb ₂ O ₅ ), tungsten oxide (WO ₂ ), molybdenum oxide (MoO ₂ ) Etc.), amorphous tin complex oxide (SnB _x P _y O _z (x = 0.44 to 0.6, y = 0.6 to 0.4, z = (2 + 3x + 5y) / 2)), metal nitride (Li ₇ MnN ₄ , Li ₃ FeN ₂ , Li ₁₅ Cr ₂ N ₉ , Li _2.6 Co _0.4 N, etc., metal phosphides (FeP ₂ , MnP ₄ , CoP ₃ etc.), lower oxides of silicon (LixSiOy (x ≧ 0.2>y> 0)), conversion anode materials (CoO, NiO, FeO, etc.), Sn-M (however, M = Ni, Fe, Co, Cu, V, Ag, Sb) alloys, composite materials (Sn-Si-O) Composite material, Sn-Co-C composite A composite material) can be applied.

  Note that the negative electrode 17 can also be manufactured by a manufacturing method according to the positive electrode 15 described above. The manufacturing method of these positive electrode 15 and negative electrode 17 is not particularly limited. If the battery performance of a required Li ion secondary battery is satisfy | filled, the manufacturing method of the positive electrode 15 and the negative electrode 17 will not be specifically limited.

The positive electrode case 11 constituting the Li-ion secondary battery 10 of the present embodiment is insoluble in the non-aqueous electrolyte on the inner surface 11a, and the oxidation-reduction reaction of the positive electrode active material constituting the positive electrode 15 and other than the positive electrode active material An inactive layer 22 made of a material that is chemically inactive with respect to the constituent material of the positive electrode 15 is formed. The inactive layer 22 may be integrally formed of the same material as that of the positive electrode case 11.
Similarly, it is preferable that the inactive layer 22 is formed on the surface 16 a of the positive electrode current collector 16. The inactive layer 22 may be integrally formed of the same material as the positive electrode current collector 16.

  As a specific example of the inactive layer 22, a configuration in which the inactive layer 22 made of pure aluminum or an aluminum alloy is formed in the inside 11 a of the positive electrode case 11 can be cited. For example, high-purity aluminum having a purity of 99.999% or more can be used as a material having excellent corrosion resistance. As the aluminum alloy constituting the inert layer 22, for example, an Al—Mg—Si based alloy which is considered to be excellent in strength and corrosion resistance can be preferably used.

  Among the Al-Mg-Si alloys, particularly those with JIS aluminum alloy number 6000 are suitable for Li ion secondary batteries, 6063 aluminum alloy (Mg: 0.45-0.9wt%, Si: 0.20-0.6wt%) ) And a 6061 aluminum alloy with a slight addition of Cu to the positive electrode case 11 and the inactive layer 22 of the positive electrode current collector 16 can be used. The inactive layer 22 may be any material that is insoluble in the non-aqueous electrolyte and chemically inactive with respect to the redox reaction of the positive electrode active material and the constituent material of the positive electrode 15 other than the positive electrode active material. However, it is not limited to these exemplified alloys.

  Pure aluminum or an aluminum alloy suitably used for the inert layer 22 is generally formed as a clad (bonding of different metals) on a base metal of a positive electrode case made of, for example, SUS. Pure aluminum or an aluminum alloy as the cladding layer is formed with a thickness of about several tens to 100 μm, for example. Note that such a thickness range is not particularly limited as long as it is a range that does not cause mechanical destruction such as cracks with respect to rolling of positive electrode case 11 or rolling such as caulking.

In the present embodiment, it is also preferable to use conductive carbon as the inactive layer 22 of the positive electrode case 11 or the positive electrode current collector 16. Formation of the inactive layer 22 made of conductive carbon on the inner surface 11a of the positive electrode case 11 and the surface 16a of the positive electrode current collector 16 is performed by, for example, LiCl—KCl or LiCl containing a carbide ion C ₂ ²⁻ source such as CaC _2. This can be realized by a method of electrolytic plating on the inner surface 11a of the positive electrode case 11 by positive polarization in a molten salt such as —KCl—CaCl _{2 at} a temperature of about 500 ° C.

As another method for forming conductive carbon, a carbon film can be formed on the inner surface 11a of the positive electrode case 11 by chemical vapor deposition (CVD) or RF magnetron sputtering. The carbon film formed in this way is subjected to heat treatment as necessary to be graphitized, and the like, so that the conductivity necessary for maintaining the battery characteristics of the Li ion secondary battery 10, preferably a conductivity of 10 ⁻¹ Ωcm level. Is granted. For the positive electrode current collector 16, the same material as that for the inactive layer 22 can be used to integrally form the positive electrode current collector 16 and the inactive layer 22 with conductive carbon.

  What is necessary is just to form the thickness of the inactive layer 22 when conductive carbon is used as the inactive layer 22 to a thickness of about several hundred nm to 1 μm. Such a thickness range is not particularly limited as long as it is a range that does not cause mechanical destruction such as cracks with respect to rolling of the positive electrode case 11 or rolling such as caulking.

  In the present embodiment, it is also preferable to use platinum as the inactive layer 22 of the positive electrode case 11 or the positive electrode current collector 16. For the positive electrode current collector 16, the same material as that for the inactive layer 22 can be used, and the positive electrode current collector 16 and the inactive layer 22 can be integrally formed of platinum.

  Formation of the inactive layer 22 made of platinum on the inner surface 11a of the positive electrode case 11 and the surface 16a of the positive electrode current collector 16 can be realized by, for example, vapor deposition or electrochemical plating. The thickness of the inactive layer 22 made of platinum is insoluble in the non-aqueous electrolyte and is chemically inactive with respect to the redox reaction of the positive electrode active material and the constituent material of the positive electrode 15 other than the positive electrode active material. The thickness of the positive electrode case 11 may be in a range that does not cause mechanical breakage such as cracks in rolling of the positive electrode case 11 or caulking. For example, the thickness is preferably several tens of nanometers or more.

  In the present embodiment, it is also preferable to use a three-component copolymer synthetic rubber having a carbon double bond in the polymer main chain as the inactive layer 22 of the positive electrode case 11 or the positive electrode current collector 16. By using a ternary copolymer synthetic rubber as the inactive layer 22, the positive electrode case 11 and the positive electrode current collector 16 are insoluble in the non-aqueous electrolyte, and the redox reaction of the positive electrode active material and the positive electrode active material It becomes chemically inactive with respect to the constituent material of the positive electrode 15 other than the above, and mechanical destruction such as cracks is suppressed against the cylindrical formation of the positive electrode case 11 and rolling such as caulking.

In the inert layer 22 of the present embodiment, ethylene and propylene are selected as two components so that the main chain has a carbon double bond, and ethylidene norbornene, 1,4-hexadiene, or 1,3 as the third component. It is preferable to use an ethylene-propylene-diene terpolymer (hereinafter referred to as EPDM) which is a polymer synthetic rubber obtained by copolymerizing dicyclopentadiene. The basic structural formula of such EPDM is as follows. However, X in a formula shows the monomer unit of the 3rd component, and l, m, and n show the number of repeating units of each group.
− (− CH ₂ −CH ₂ −) _l − (− CH ₂ −CH−) _m − (X) _n −
|
CH ₃

  As a method of forming the inert layer 22 of the positive electrode case 11 or the positive electrode current collector 16 using a ternary copolymer synthetic rubber having a carbon double bond in the polymer main chain, for example, a ternary system is used. An appropriate amount of the copolymer synthetic rubber is dissolved in a solvent such as toluene or cyclohexane, and this solution is dropped on the positive electrode case 11 or the positive electrode current collector 16 and dispersed by spin coating or the like, followed by drying. Can be mentioned.

  According to the Li ion secondary battery (secondary battery) 10 of the present embodiment configured as described above, by including a halide of a carboxylic acid ester in at least one of the nonaqueous solvents constituting the nonaqueous electrolytic solution, Even if a metal chloride or a metal and lithium chloride are used as the positive electrode active material, the elution of the positive electrode active material into the non-aqueous electrolyte can be suppressed or prevented. As a result, it is possible to suppress instability of the crystal structure due to elution of the positive electrode active material, and to prevent deterioration of battery characteristics such as a decrease in charge / discharge capacity.

  Further, according to the Li ion secondary battery (secondary battery) 10 of the present embodiment, the inner surface 11a of the positive electrode case 11 and the surface 16a of the positive electrode current collector 16 are insoluble in the nonaqueous electrolytic solution and are active in the positive electrode. A halide having a high reaction activity is used as a positive electrode active material by forming an inactive layer 22 made of a material that is chemically inert to the constituent materials of the positive electrode 15 other than the redox reaction of the material and the positive electrode active material. However, it is possible to prevent the positive electrode case 11 and the positive electrode current collector 16 from being chemically deteriorated. This makes it possible to suppress deterioration of battery characteristics such as a decrease in battery capacity due to repeated charging and discharging.

  For example, according to the Li ion secondary battery (secondary battery) 10 of the present embodiment, a discharge voltage of a high voltage flat portion of 3.0 V ± 0.2 V can be shown at a current value of at least 0.01 C. Such a high voltage discharge characteristic can be exhibited even when the Li ion secondary battery (secondary battery) 10 of the present embodiment uses a halide having a high reaction activity as a positive electrode active material. This is because the positive electrode case 11, the positive electrode current collector 16 and the like are chemically stable.

Hereinafter, the effect of the Li ion secondary battery (secondary battery) of the present invention was verified.
[Verification Example 1-1]
In a glove box in an argon atmosphere, LiPF ₆ powder (electrolyte grade methyl-2,2-difluoroacetate (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm, hereinafter referred to as MFA)) Manufacturer: Kishida Chemical Co., Reagent No .: LBG45864) was dissolved, and a 1M LiPF ₆ -MFA non-aqueous electrolyte (Invention Example 1-1) and a 2M LiPF6-MFA non-aqueous electrolyte (Invention Example 1) were dissolved. 2) were prepared respectively.
On the other hand, electrolyte grade propylene carbonate (manufacturer: Kishida Chemical, reagent number: LBG64955, water content: 23 ppm, hereinafter referred to as PC) and fluoroethylene carbonate (a kind of fluorinated carbonate described in Patent Document 1) Manufacturer: Kishida Chemical Co., Ltd., LBG32051, water content: 50 ppm or less, hereinafter referred to as FEC), LiPF ₆ powder (manufacturer: Kishida Chemical Co., reagent number: LBG45864) was dissolved respectively, and a concentration of 1M LiPF ₆ -PC (Comparative Example 1- 1), 1M LiPF ₆ -FEC (Comparative Example 1-2), 2M LiPF ₆ -PC (Comparative Example 1-3), 2M LiPF ₆ -FEC (Comparative Example 1-4) did.
An anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-) dried under reduced pressure at 80 ° C. all day and night in the non-aqueous electrolytes of Examples 1-1, 1-2 of the present invention and Comparative Examples 1-1 to 1-4. 50G, purity: 99.995% or more) was added over the saturated dissolution amount, and the mixture was stirred at room temperature for 15 hours.
Thereafter, the solution was centrifuged at 20,000 G for 2 hours, and the supernatant was collected and subjected to ICP-MS measurement to calculate the dissolution concentration of Cu. Prior to the preparation of the non-aqueous electrolyte, it has been confirmed in advance that the solvent does not contain Cu.
Table 1 shows the measurement results of the Cu dissolution concentration of the nonaqueous electrolytic solutions of Invention Examples 1-1 and 1-2 and Comparative Examples 1-1 to 1-4.

According to the results shown in Table 1, the non-aqueous electrolytes of Invention Example 1-1 and Invention Example 1-2 have a very low Cu concentration compared to Comparative Examples 1-1 to 1-4. It was confirmed that the non-aqueous electrolyte solution can effectively suppress the dissolution of the positive electrode active material CuCl ₂ .
On the other hand, in the case of the non-aqueous electrolytes of Comparative Examples 1-1 to 1-4 using PC and FEC that are conventionally used as solvents, compared with the MFA solvents used in Invention Examples 1-1 and 1-2. Thus, it was confirmed that a large amount of CuCl ₂ dissolved by two digits or more was not preferable as a non-aqueous electrolyte that suppresses dissolution of a positive electrode active material of metal chloride such as CuCl ₂ .

[Verification Example 1-2]
In order to obtain the Li ion secondary battery of Invention Example 1-3, in an argon atmosphere glove box, electrolyte grade MFA (Manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) LiPF ₆ powder (manufacturer: Kishida Chemical Co., reagent number: LBG45864) was dissolved in 1M LiPF ₆ -MFA non-aqueous electrolyte.
Anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) is pulverized for 10 minutes in an agate mortar as a positive electrode, and AB (acetylene black, manufacturer: Electrochemical Industry) as a conductive aid , Reagent name: Denka Black) and mixing for another 10 minutes, then add polytetrafluoroethylene (manufacturer: Mitsui DuPont Fluorochemical, reagent number: 6J, hereinafter referred to as PTFE) as a binder and knead for 20 minutes. A rough sheet was formed. This rough sheet was roll-pressed to produce a positive electrode sheet. The positive electrode sheet was punched into a circle with a diameter of 5 mm, a platinum net was placed on the back surface, and pressed with the sheet at a pressure of 10 MPa for 30 seconds to produce a positive electrode. The composition ratio of the positive electrode is CuCl ₂ 50 wt%, AB 30 wt%, and PTFE 20 wt%. A lithium foil (manufacturer: Honjo Metal Co., Ltd.) having a thickness of 0.5 mm was cut and used for the negative electrode and the reference electrode as counter electrodes.
Then, the electrolytic solution was housed in a Pyrex (registered trademark) glass container, and sealed with a lid equipped with a positive electrode, a negative electrode (counter electrode), and a reference electrode to assemble a test cell. All operations related to the fabrication of the positive electrode and the assembly of the test cell were performed in a glove box in an argon atmosphere. The Li ion secondary battery of Inventive Example 1-3 was obtained through the above steps.

To obtain Li-ion secondary batteries of Comparative Examples 1-5 and 1-6, in an argon atmosphere glove box, electrolyte-grade PC (manufacturer: Kishida Chemical, reagent number: LBG64955, water content: 23 ppm), And 1M LiPF ₆ -PC non-aqueous electrolyte and 1M LiPF ₆ -FEC non-aqueous electrolyte using FEC (Manufacturer: Kishida Chemical, LBG32051, water content: 50 ppm or less) described in Patent Document 1, A similar test cell was prepared using the same positive electrode, negative electrode, and reference electrode as in the test cell of Invention Example 1-3. Through the above steps, the Li ion secondary battery (PC solvent) of Comparative Example 1-5 and the Li ion secondary battery (FEC solvent) of Comparative Example 1-6 were obtained.

Using the Li ion secondary batteries of Invention Examples 1-3 and Comparative Examples 1-5 and 1-6 described above, a current value of 0.01 C per CuCl ₂ (399 mAh / g- (CuCl _{2 )} ) content of the positive electrode Then, a charge / discharge test was performed in a voltage range of 2.5V to 3.6V. FIG. 2 is a graph showing initial discharge voltage profiles of Li-ion secondary batteries of Inventive Example 1-3 and Comparative Examples 1-5 and 1-6. According to FIG. 2, the Li ion secondary battery of Example 1-3 of the present invention using MFA as the solvent of the non-aqueous electrolyte is Comparative Examples 1-5 and 1-6 using conventional solvents such as PC and FEC. Compared with the lithium ion secondary battery, it was confirmed that the specific capacity was much larger.

  Table 2 shows the discharge capacity and the charge capacity of 1 to 4 cycles in the charge / discharge test using the Li ion secondary battery of Inventive Example 1-3. Table 3 shows the discharge capacity and the charge capacity of 1 to 3 cycles in the charge / discharge test using the Li ion secondary battery of Comparative Example 1-5. Table 4 shows the discharge capacity and the charge capacity of 1 to 3 cycles in the charge / discharge test using the Li ion secondary battery of Comparative Example 1-6. In each of the charge and discharge tests shown in Tables 2 to 4, the discharge end voltage is 2.5V, and the charge end voltage is 3.7V.

FIG. 3 is a graph showing the transition of the discharge capacity up to the third cycle of the Li ion secondary batteries of Inventive Example 1-3 and Comparative Examples 1-5 and 1-6.
As is clear from the comparison of Tables 2 to 4 and FIG. 3, the Li ion secondary battery of Example 1-3 of the present invention using MFA as the solvent for the nonaqueous electrolytic solution has a discharge capacity even when the charge / discharge cycle is repeated. It was confirmed that the battery capacity was reduced and the battery characteristics were good. On the other hand, the Li-ion secondary batteries of Comparative Examples 1-5 and 1-6 in which PC and FEC that have been conventionally used are non-aqueous electrolyte solvents have already greatly decreased both in discharge capacity and charge capacity in the second cycle. In addition, it was confirmed that the battery characteristics were greatly inferior to those of Invention Example 1-3.

[Verification Example 1-3]
In the same manner as in Example 1-2 of the present invention, a 1M LiPF ₆ -MFA nonaqueous electrolytic solution having a concentration of MFA as a solvent was prepared.
Anhydrous LiCl (manufacturer: Aldrich, reagent number: 42957-25G) was pulverized in an agate mortar for 10 minutes, and Cu powder having a particle size of 60 to 80 nm (manufacturer: Aldrich, reagent number: 774103-25G, particle size 60) as a positive electrode active material. ˜80 nm) was added and mixed for 10 minutes, and AB (manufacturer: Denki Kagaku Kogyo, reagent name: Denka Black) was further added as a conductive additive and mixed for 10 minutes. A PTFE powder (manufacturer: Mitsui / DuPont Fluorochemical, reagent number: 6J) was added to the mixed powder as a binder, and kneaded for 20 minutes to prepare a coarse sheet. The coarse sheet was punched into a circle with a diameter of 5 mm, and behind this was pressed with a platinum mesh as a current collector at a pressure of 10 Mpa for 30 seconds to produce a positive electrode containing Cu and LiCl as a positive electrode active material. The composition ratio of the positive electrode is Cu 20 wt%, LiCl 30 wt%, AB 30 wt%, and PTFE 20 wt%.
A lithium foil having a thickness of 0.5 mm was cut and used for the negative electrode as a counter electrode and the reference electrode.
Using these positive electrode, negative electrode, and non-aqueous electrolyte, a Li ion secondary battery of Invention Example 1-4 was obtained in the same process as that of Invention Example 1-2.

In order to obtain the Li ion secondary battery of Comparative Example 1-7, a 1M LiPF ₆ -FEC nonaqueous electrolytic solution using FEC (water content of 50 ppm or less) as a solvent was prepared. And the Li ion secondary battery of the comparative example 1-7 using the positive electrode, negative electrode, and reference electrode which contain Cu and LiCl similar to this invention example 1-3 as a positive electrode active material was obtained.

  Using the Li ion secondary batteries of Invention Example 1-4 and Comparative Example 1-7, a charge / discharge test starting from the charged state was performed. All tests were performed in an argon atmosphere glove box.

FIG. 4 is a graph showing changes in discharge capacity and charge capacity due to repeated charge / discharge of Li ion secondary batteries of Invention Examples 1-4 and Comparative Examples 1-7.
As is apparent from the graph of FIG. 4, the Li ion secondary battery of Inventive Example 1-4 including the LiPF ₆ -MFA nonaqueous electrolytic solution includes the LiPF6-FEC nonaqueous electrolytic solution which is Comparative Example 1-7. Compared to the Li ion secondary battery, it was confirmed that both the discharge capacity and the charge capacity were large, and the battery characteristics were excellent with a small decrease in the discharge capacity and the charge capacity as the charge / discharge cycle progressed.

5 and 6 are graphs showing a charging curve and a discharging curve by repeated charging and discharging of the Li ion secondary battery of Inventive Example 1-4.
5 and 6, the horizontal axis indicates the capacity based on CuCl ₂ , and the vertical axis indicates the potential. According to these measurement results, it was confirmed that the electrochemical polarization of the Li ion secondary battery of Inventive Example 1-4 containing the LiPF ₆ -MFA non-aqueous electrolyte was as small as <0.1V. The theoretical potential of Cu + LiCl⇔CuCl + Li ⁺ + e ⁻ is 2.74 V (vs. Li / Li ⁺ ), and the charge plateau and discharge plateau can be confirmed in the range of 2.74 V (vs. Li / Li ⁺ ) ± 0.05 V. did it. The ^{_{CuCl + LiCl⇔CuCl 2 + Li + +}} e - theoretical potential of is 3.07V (vs. Li / Li ^+), check the charging plateau and discharge plateau in the range of 3.41V (vs. Li / Li ⁺⁾ ± 0.05V We were able to.

[Verification Example 1-4]
In an argon atmosphere glove box, electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) and LiPF ₆ powder (manufacturer: Kishida Chemical, reagent number: LBG45864), LiN (CF ₃ SO ₂ ) ₂ (LiTFSI) powder (Manufacturer: Kishida Chemical, reagent number: LBG43511), LiN (C ₂ F ₅ SO ₂ ) ₂ (LiBETI) powder (Manufacturer: Kishida Chemical, reagent number: LBG43531) After dissolution, a 1M LiPF ₆ -MFA nonaqueous electrolyte, a 1M LiTFSI-MFA nonaqueous electrolyte, and a 1M LiBETI-MFA nonaqueous electrolyte were prepared.
Then, the same process as verification Example 1-2, CuCl ₂ positive electrode and a lithium negative electrode (counter electrode), the reference electrode was produced, the Li-ion secondary battery of the present invention Examples 1-5,1-6,1-7 Obtained. And the charging / discharging test was done on the conditions similar to the verification example 1-2 using this Li ion secondary battery of this invention example 1-5, 1-6, 1-7.
Table 5 shows the measurement results of the initial specific capacities (CuCl ₂ weight basis) of Examples 1-5, 1-6, and 1-7 of the present invention.

According to the results shown in Table 5, it was confirmed that when a non-aqueous electrolyte using MFA as a solvent was used, an excellent Li ion secondary battery showing a large capacity of 300 mAh / g- ¹ or more was obtained.

[Verification Example 1-5]
In order to obtain the Li ion secondary battery of Invention Example 1-8, electrolyte grade MFA (Manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) in a glove box in an argon atmosphere. LiPF ₆ powder (manufacturer: Kishida Chemical Co., Reagent No .: LBG45864) was dissolved in a solution to prepare a 1M LiPF ₆ -MFA non-aqueous electrolyte.
Further, in order to obtain the Li ion secondary battery of Inventive Example 1-9, electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: in a glove box in an argon atmosphere. LiBETI (manufacturer: Kishida Chemical Co., reagent number: LBG43531) was dissolved in 50 ppm) to prepare a LiBETI-MFA non-aqueous electrolyte solution having a concentration of 1M.
In addition, in order to obtain the Li ion secondary battery of Invention Example 1-10, in an argon atmosphere glove box, electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: LiTFSI (manufacturer: Kishida Chemical Co., reagent number: LBG43511) was dissolved in 50 ppm) to prepare a LiTFSI-MFA non-aqueous electrolyte solution having a concentration of 1M.
Anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) is ground in an agate mortar for 10 minutes, and this is AB (manufacturer: Denki Kagaku Kogyo, reagent name: DENKA) Black) was added and further mixed for 10 minutes, and then PTFE (manufacturer: Mitsui / DuPont Fluorochemicals, reagent number: 6J) was added as a binder and kneaded for 20 minutes to form a rough sheet. This rough sheet was roll-pressed to produce a positive electrode sheet. The positive electrode sheet was punched into a circle with a diameter of 5 mm, a platinum net was placed on the back surface, and pressed with the sheet at a pressure of 10 MPa for 30 seconds to produce a positive electrode. The composition ratio of the positive electrode is CuCl ₂ 50 wt%, AB 30 wt%, and PTFE 20 wt%. A lithium foil having a thickness of 0.5 mm was cut and used for the negative electrode as a counter electrode and the reference electrode.
Each of the non-aqueous electrolytes described above was placed in a 5 ml Pyrex (registered trademark) glass container, and sealed with a lid equipped with a positive electrode, a negative electrode (counter electrode), and a reference electrode to assemble a test cell. All operations related to the fabrication of the positive electrode and the assembly of the test cell were performed in a glove box in an argon atmosphere. Through the above steps, Li-ion secondary batteries of Inventive Examples 1-8 to 1-10 were obtained.

Using the Li ion secondary batteries of Examples 1-8 to 1-10 of the present invention, self-discharge (spontaneous discharge) tests were conducted after the downtime of 6 h, 174 h, 342 h, and 678 h. The discharge rate is 0.01C.
FIG. 6 shows a change in discharge capacity due to self-discharge, and FIG. 7 shows a change in weight energy density due to self-discharge.

According to the results of Verification Example 1-5 shown in FIGS. 6 and 7, the Li ion secondary battery of Inventive Example 1-8 using LiPF ₆ -MFA as the non-aqueous electrolyte is the best, and self-discharge The rate tended to saturate at about 20% after about one month. It was also confirmed that the weight energy density was maintained at about 900 Wh kg ⁻¹ .
On the other hand, the Li ion secondary battery of Inventive Example 1-9 using LiBETI-MFA as a non-aqueous electrolyte or Inventive Example 1-10 using LiTFSI-MFA has a battery capacity of almost zero in about one month. Became.
Therefore, it was confirmed that the self-discharge characteristic of Example 1-8 of the present invention using LiPF ₆ -MFA as the nonaqueous electrolytic solution was excellent.

[Verification Example 1-6]
In order to obtain the Li ion secondary battery of Invention Example 1-11, in an argon atmosphere glove box, electrolyte grade MFA (Manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) LiPF ₆ powder (manufacturer: Kishida Chemical Co., Reagent No .: LBG45864) was dissolved in a solution to prepare a 1M LiPF ₆ -MFA non-aqueous electrolyte.
Moreover, in order to obtain the Li ion secondary battery of Comparative Example 1-8, in an argon atmosphere glove box, electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) LiBETI (manufacturer: Kishida Chemical Co., reagent number: LBG43531) was dissolved to prepare a LiBETI-MFA non-aqueous electrolyte solution having a concentration of 1M.
Moreover, in order to obtain the Li ion secondary battery of Comparative Example 1-9, electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) in a glove box in an argon atmosphere. LiTFSI (manufacturer: Kishida Chemical, reagent number: LBG43511) was dissolved in 1) to prepare a LiTFSI-MFA non-aqueous electrolyte solution having a concentration of 1M.
Anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) is ground in an agate mortar for 10 minutes, and this is AB (manufacturer: Denki Kagaku Kogyo, reagent name: DENKA) Black) was added and further mixed for 10 minutes, and then PTFE (manufacturer: Mitsui / DuPont Fluorochemicals, reagent number: 6J) was added as a binder and kneaded for 20 minutes to form a rough sheet. This rough sheet was roll-pressed to produce a positive electrode sheet. The positive electrode sheet was punched into a circle with a diameter of 5 mm, a platinum net was placed on the back surface, and pressed with the sheet at a pressure of 10 MPa for 30 seconds to produce a positive electrode. The composition ratio of the positive electrode is CuCl ₂ 50 wt%, AB 30 wt%, and PTFE 20 wt%. A lithium foil having a thickness of 0.5 mm was cut and used for the negative electrode as a counter electrode and the reference electrode.
Each of the non-aqueous electrolytes described above was placed in a 5 ml Pyrex (registered trademark) glass container, and sealed with a lid equipped with a positive electrode, a negative electrode (counter electrode), and a reference electrode to assemble a test cell. All operations related to the fabrication of the positive electrode and the assembly of the test cell were performed in a glove box in an argon atmosphere. Through the above steps, Li-ion secondary batteries of Invention Example 1-11 and Comparative Examples 1-8 and 1-9 were obtained.

Using the Li ion secondary batteries of Inventive Example 1-11 and Comparative Examples 1-8 and 1-9, self-discharge (spontaneous discharge) tests were conducted after downtime 6 h, 174 h, 342 h and 678 h. The discharge rate is 0.01C.
FIG. 8 shows discharge curves at respective pause times in Inventive Example 1-11. Moreover, the discharge curve in each rest time in Comparative Example 1-8 is shown in FIG. In addition, FIG. 10 shows the discharge curves at the respective rest times in Comparative Example 1-9.

According to the measurement results shown in FIG. 8, the Li ion secondary battery of Example 1-11 of the present invention using LiPF ₆ -MFA as the non-aqueous electrolyte is saturated with a self-discharge rate of about 20% (about 1 month). The tendency to do was seen. The capacity density is maintained at 320 mAh g ⁻¹ or more. In addition, it was confirmed that the discharge curve shape was almost constant regardless of the downtime. The cause of the self-discharge is considered to depend on the solubility of the positive electrode active material.
According to the measurement result shown in FIG. 9, it was confirmed that the capacity | capacitance of the Li ion secondary battery of Comparative Example 1-8 using LiBETI-MFA as a non-aqueous electrolyte becomes zero in about one month. It was also confirmed that the discharge curve shape was almost constant regardless of the downtime. The cause of self-discharge is thought to depend on the solubility of the active material.
According to the measurement result shown in FIG. 10, it was confirmed that the capacity | capacitance of the Li ion secondary battery of Comparative Example 1-9 using LiTFSI-MFA as a non-aqueous electrolyte becomes zero in about one month. It was also confirmed that the discharge curve shape was almost constant regardless of the downtime. The cause of self-discharge is thought to depend on the solubility of the active material.

[Verification Example 1-7]
In order to obtain the Li ion secondary battery of Inventive Example 1-12, an electrolyte grade MFA (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI Z4528, water content: 50 ppm) and LiPF ₆ powder (manufacturer: Kishida) Chemical, reagent number: LBG45864) was dissolved to prepare a LiPF ₆ -MFA nonaqueous electrolyte solution having a concentration of 1M.
Anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) is ground in an agate mortar for 10 minutes, and this is AB (manufacturer: Denki Kagaku Kogyo, reagent name: DENKA) Black) was added and further mixed for 10 minutes, and then PTFE (manufacturer: Mitsui / DuPont Fluorochemicals, reagent number: 6J) was added as a binder and kneaded for 20 minutes to form a rough sheet. This rough sheet was roll-pressed to produce a positive electrode sheet. The positive electrode sheet was punched into a circle with a diameter of 5 mm, a platinum net was placed on the back surface, and pressed with the sheet at a pressure of 10 MPa for 30 seconds to produce a positive electrode. The composition ratio of the positive electrode is CuCl ₂ 50 wt%, AB 30 wt%, and PTFE 20 wt%. A lithium foil having a thickness of 0.5 mm was cut and used for the negative electrode as a counter electrode and the reference electrode.
Each of the non-aqueous electrolytes described above was placed in a 5 ml Pyrex (registered trademark) glass container, and sealed with a lid equipped with a positive electrode, a negative electrode (counter electrode), and a reference electrode to assemble a test cell. All operations related to the fabrication of the positive electrode and the assembly of the test cell were performed in a glove box in an argon atmosphere. Through the above steps, a Li ion secondary battery of Inventive Example 1-12 was obtained.

  Using the Li ion secondary battery of Inventive Example 1-12, rate characteristic tests were conducted at discharge rates of 0.01 C, 0.1 C, 0.4 C, 1.0 C, and 2.0 C. The rest time was 6 h for each condition.

  FIG. 11 shows discharge curves at respective discharge rates in Inventive Example 1-12.

According to the measurement results shown in FIG. 11, the Li ion secondary battery of Inventive Example 1-12 using LiPF ₆ -MFA as the nonaqueous electrolyte solution has a capacity density of 400 mAh g ⁻¹ even at a discharge rate of 2.0 C. It was confirmed that the degree was maintained. The IR drop tends to be large because the distance between the electrodes is as large as about 5 mm. Since the distance between electrodes of a Li ion battery is usually about 50 μm, it is considered that IR drop is reduced by shortening the distance between electrodes.

[Verification Example 1-8]
In order to obtain the Li ion secondary battery of Invention Example 1-12, electrolyte grade propyl-2,2-difluoroacetate (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number: TCI) in a glove box under an argon atmosphere. LiPF ₆ powder (manufacturer: Kishida Chemical Co., reagent number: LBG45864) was dissolved in Z4549 (water content: 50 ppm) to prepare a non-aqueous electrolyte solution having a concentration of 1M.
In addition, in order to obtain the Li ion secondary battery of Invention Example 1-13, electrolyte grade butyl-2,2-difluoroacetate (manufacturer: Tokyo Kasei Kogyo Co., Ltd., reagent number) in a glove box in an argon atmosphere. : TCI Z4550, water content: 50 ppm) LiPF ₆ powder (manufacturer: Kishida Chemical Co., reagent number: LBG45864) was dissolved to prepare a non-aqueous electrolyte solution having a concentration of 1M.
Moreover, in order to obtain the Li ion secondary battery of Inventive Example 1-14, electrolyte grade methyl-2,2-dichloroacetate (manufacturer: Tokyo Chemical Industry Co., Ltd., reagent number) in a glove box in an argon atmosphere. : TCI Z4551, water content: 50 ppm) LiPF ₆ powder (manufacturer: Kishida Chemical, reagent number: LBG45864) was dissolved to prepare a 1M non-aqueous electrolyte solution.
Anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) is ground in an agate mortar for 10 minutes, and this is AB (manufacturer: Denki Kagaku Kogyo, reagent name: DENKA) Black) was added and further mixed for 10 minutes, and then PTFE (manufacturer: Mitsui / DuPont Fluorochemicals, reagent number: 6J) was added as a binder and kneaded for 20 minutes to form a rough sheet. This rough sheet was roll-pressed to produce a positive electrode sheet. The positive electrode sheet was punched into a circle with a diameter of 5 mm, a platinum net was placed on the back surface, and pressed with the sheet at a pressure of 10 MPa for 30 seconds to produce a positive electrode. The composition ratio of the positive electrode is CuCl ₂ 50 wt%, AB 30 wt%, and PTFE 20 wt%. A lithium foil having a thickness of 0.5 mm was cut and used for the negative electrode as a counter electrode and the reference electrode.
Each of the non-aqueous electrolytes described above was placed in a 5 ml Pyrex (registered trademark) glass container, and sealed with a lid equipped with a positive electrode, a negative electrode (counter electrode), and a reference electrode to assemble a test cell. All operations related to the fabrication of the positive electrode and the assembly of the test cell were performed in a glove box in an argon atmosphere. Through the above steps, Li-ion secondary batteries of Inventive Examples 1-13 to 1-15 were obtained.

Using the Li ion secondary batteries of Examples 1-13 to 1-15 of the present invention, a self-discharge (spontaneous discharge) test was conducted after 6 hours of downtime. The discharge rates are 0.01C for Invention Examples 1-13 and 1-14, and 0.1C for Invention Example 1-15.
FIG. 12 shows a discharge curve of the Li ion secondary battery of Inventive Examples 1-13 to 1-15.
According to the measurement results shown in FIG. 12, Example 1-13 of the present invention using propyl-2,2-difluoroacetate as the solvent of the non-aqueous electrolyte and Example of the present invention using butyl-2,2-difluoroacetate. It was confirmed that the 1-14 Li-ion secondary battery can be discharged with a capacity of almost 100%. Further, it was confirmed that the Li ion secondary battery of Inventive Example 1-15 using methyl-2,2-dichloroacetate as a solvent for the nonaqueous electrolytic solution can be discharged at a capacity of 85%.
It was confirmed that when a CX ₂ COOR organic solvent was applied as the solvent for these non-aqueous electrolytes, there was an effect of suppressing dissolution of the metal chloride.

[Verification Example 2-1]
In a glove box under an argon atmosphere, methyl electrolyte grade 2,2 difluoroacetate CHF ₂ COOCH ₃ (manufacturer: Tokyo Chemical Industry Co., Ltd., Reagent No.: TCI Z4549, water content: 50 ppm) to LiPF ₆ powder (manufacturer : Kishida chemistry, reagent number: LBG45864) was dissolved to prepare a 1M LiPF ₆ -MFA non-aqueous electrolyte.
As the negative electrode, a lithium foil having a thickness of 0.25 mm was punched into a circle having a diameter of 13 mm, and was pressed onto the negative electrode case.
For the positive electrode, anhydrous CuCl ₂ powder (manufacturer: Aldrich, reagent number: 451665-50G, purity: 99.995% or more) and AB (manufacturer: Denki Kagaku Kogyo, reagent name: Denka Black) as a conductive aid are used in an agate mortar. The mixture was mixed for 4 minutes with a stirrer, PTFE (manufacturer: Mitsui / DuPont Fluorochemical, reagent number: 6J) was added as a binder, and the mixture was further mixed for 40 seconds to prepare a coarse sheet. The composition ratio of the positive electrode is CuCl ₂ 70 wt%, AB 25 wt%, and PTFE 5 wt%. The rough sheet was passed through a forming roll machine to produce a positive electrode sheet having a thickness of 0.5 mm. A positive electrode having a diameter of 13 mm was produced by punching from the positive electrode sheet.
A positive electrode case and a positive electrode current collector were prepared in advance as follows.
Invention Example 2-1: A 12 mm platinum mesh was attached by spot welding to an aluminum clad positive electrode sheet in which a 6061 aluminum alloy was bonded to a SUS substrate as an inert layer.
Invention Example 2-2: A SUS positive electrode case was previously spot-welded with a 12 mm platinum mesh, diamond-like carbon (hereinafter referred to as DLC) forming an inert layer was CVD deposited, and a positive current collector The DLC deposited on the surface of the body was scraped with sandpaper.
Invention Example 2-3: A SUS positive electrode case was placed in a vacuum chamber, and the pressure was reduced until the pressure became 10 ⁻³ torr or less, and platinum serving as an inactive layer was deposited on the inner wall of the positive electrode case at 5 mA for 15 minutes. A 12 mm diameter platinum mesh was spot welded to the platinum vapor deposition case.
Invention Example 2-4: A polymer block of ethylene-propylene-diene terpolymer (hereinafter referred to as EPDM) is cut into small pieces with a cutter knife in an argon atmosphere glove box, dissolved little by little in toluene, and stirred for one day and night. About 1 wt% EPDM solution was prepared. On the other hand, a 12 mm diameter platinum mesh was spot welded to the SUS positive electrode case, and was carried into an argon atmosphere groove box. This EPDM was dropped on the inner wall of the positive electrode case other than the platinum mesh with a microsyringe and dried to form an EPDM layer as an inert layer on the inner wall of the positive electrode case.
Comparative Example 2-1: A SUS positive electrode case in which a 12 mm diameter platinum mesh was spot welded to the inner wall of the positive electrode case.
In these five types of positive electrode cases of Invention Examples 2-1 to 2-4 and Comparative Example 2-1, a positive electrode pellet was placed on a positive electrode current collector, and the pressure was 2 tons with a hand press machine. The pressure was applied for about a second, and the positive electrode was attached on the positive electrode current collector by pressure bonding. A gasket was attached to the negative electrode case attached with negative lithium.
A CR2023 type coin cell was manufactured by filling the prepared electrolyte in the positive electrode case and the negative electrode case and caulking with an automatic caulking machine.
A series of productions other than the preparation of the positive electrode case were all performed in a glove box in an argon atmosphere.
The coin cells (Li ion secondary batteries) of the present invention examples 2-1 to 2-4 and comparative example 2-1 were installed in a thermostat set to 21 ° C. and connected to an automatic charge / discharge test apparatus. The change over time in the circuit voltage (hereinafter referred to as OCV) was continuously measured.
The measurement results of the circuit voltage up to 800 hours of these inventive examples 2-1 to 2-4 and comparative example 2-1 are shown in FIG.

  According to the measurement results shown in FIG. 13, the coin cells of Examples 2-1 to 2-4 of the present invention in which the inactive layer was formed in the positive electrode case were all compared with the coin cell of Comparative Example 2-1 in which no inactive layer was formed. As a result, it was confirmed that the positive electrode case was chemically stable with respect to the used battery constituent materials.

[Verification Example 2-2]
In the same manner as in Verification Example 2-1, a lithium foil punched out into a circle having a diameter of 13 mm was pressed onto a SUS negative electrode case. In addition, a positive electrode material mixture pellet containing CuCl ₂ produced in Verification Example 2-1 as an active material and a LiPF ₆ -MFA nonaqueous electrolyte solution having a concentration of 1M were prepared.
A positive electrode case and a positive electrode current collector were prepared in advance as follows.
Invention Example 2-5: A platinum mesh having a diameter of 12 mm was attached by spot welding to an aluminum clad positive electrode sheet in which a 6061 aluminum alloy serving as an inert layer was bonded to a SUS substrate.
Invention Example 2-6: A SUS positive electrode case was placed in a vacuum chamber and the pressure was reduced until the pressure became 10 ⁻³ torr or less, and platinum was deposited on the inner wall of the positive electrode case as an inactive layer at 5 mA for 15 minutes. A platinum net having a diameter of 12 mm was spot welded to the platinum vapor deposition case.
Invention Example 2-7: A stainless steel positive electrode case was spot-welded to a platinum mesh with a diameter of 12 mm in advance, and a toluene solution of EPDM prepared in the same manner as in Invention Example 2-4 was added to the positive electrode case other than the platinum mesh with a microsyringe. The EPDM layer was dropped on the inner wall and dried to form an EPDM layer serving as an inactive layer on the inner wall of the positive electrode case.
In these three types of positive electrode cases of Invention Examples 2-5 to 2-7, a positive electrode pellet is placed on a positive electrode current collector, and is pressed by a hand press machine at a pressure of 2 tons for about 10 seconds. It attached by crimping on the positive electrode current collector. A gasket was attached to the negative electrode case attached with negative lithium. The positive electrode case and the negative electrode case were filled with the prepared electrolytic solution and caulked with an automatic caulking machine to produce a CR2023 type coin cell (Li ion secondary battery). A series of productions other than the preparation of the positive electrode case were all performed in a glove box in an argon atmosphere.

The produced coin cells of Examples 2-5 to 2-7 of the present invention were installed in a thermostat set to 21 ° C., and connected to an automatic charge / discharge test apparatus to perform a charge / discharge test. The test was performed in a voltage range of 2.4 V to 3.6 V at a current value of 0.01 C per CuCl ₂ (393 mAh / g) content of the positive electrode.

The results of these verification examples 2-2 are shown in FIG. That is, FIG. 14 is a diagram showing an initial discharge and charge voltage profile of each test cell, and a curve 2-5 in the diagram is a charge / discharge voltage profile of the test cell of Example 2-5 of the present invention. 2-6 is the charge / discharge voltage profile of the test cell of Inventive Example 2-6, and curve 2-7 is the charge / discharge voltage profile of the test cell of Inventive Example 2-7.
As can be seen from FIG. 14, it was found that when the positive electrode case of the present invention was used, a secondary battery having excellent characteristics having a high discharge voltage flat portion of 3 V or more can be realized.

[Verification Example 2-3]
A coin cell (Li ion secondary battery) of Invention Example 2-8 was prepared by the following procedure.
In the same manner as in Verification Example 2-1, a lithium foil punched out into a circle having a diameter of 13 mm was pressed onto a SUS negative electrode case. Moreover, the positive electrode mixture pellet containing CuCl ₂ produced in Verification Example 2-1 as an active material and the LiPF ₆ -MFA nonaqueous electrolyte solution having a concentration of 1 M were used for the test cell.
A 12 mm diameter platinum mesh was spot welded to the SUS positive electrode case in advance, and a toluene solution of EPDM prepared in the same manner as in Example 2-4 of the present invention was dropped on the inner wall of the positive electrode case other than the platinum mesh with a microsyringe and dried. Thus, an EPDM layer serving as an inactive layer was formed on the inner wall of the positive electrode case.
Then, in the same manner as in Verification Example 2-1, the positive electrode pellet was placed on the positive electrode current collector in the positive electrode case, and pressurized with a hand press machine at a pressure of 2 tons for about 10 seconds. It was crimped onto the body and attached. A gasket was attached to the negative electrode case attached with negative lithium.
The positive electrode case and the negative electrode case were filled with the prepared electrolytic solution and caulked with an automatic caulking machine to produce a CR2023 type coin cell (Li ion secondary battery). A series of production other than platinum coating on the inner wall of the positive electrode case was all performed in a glove box in an argon atmosphere.
Through the above steps, a coin cell (Li ion secondary battery) of Inventive Example 2-8 was obtained.

A coin cell (Li ion secondary battery) of Comparative Example 2-2 was prepared by the following procedure.
A positive electrode case in which a platinum mesh with a diameter of 12 mm was attached to the inner wall of a SUS case as a current collector was used. Further, in the same manner as in Invention Example 2-8, a lithium foil punched out into a circle having a diameter of 13 mm was pressure-bonded to a SUS negative electrode case. In addition, a positive electrode material mixture pellet containing CuCl ₂ as an active material, similar to Inventive Example 2-8, and a LiPF ₆ -MFA electrolyte solution having a concentration of 1 M were used in a test cell.
The positive electrode pellet is placed on the current collector in the positive electrode case, the positive electrode pellet is placed on the positive electrode current collector in the same manner as in Example 2-8 of the present invention, and about 10 seconds at a pressure of 2 tons by a hand press machine. The positive electrode was pressed onto the positive electrode current collector and attached. A gasket was attached to the negative electrode case attached with negative lithium.
The positive electrode case and the negative electrode case were filled with the prepared electrolytic solution and caulked with an automatic caulking machine to produce a CR2023 type coin cell (Li ion secondary battery). A series of production other than platinum coating on the inner wall of the positive electrode case was all performed in a glove box in an argon atmosphere.
Through the above steps, a coin cell (Li ion secondary battery) of Comparative Example 2-2 was obtained.

The produced coin cells of Invention Example 2-8 and Comparative Example 2-2 were placed in a thermostatic chamber set at 21 ° C., and connected to an automatic charge / discharge test apparatus to perform a charge / discharge test. The test was performed in a voltage range of 2.4 V to 3.6 V at a current value of 0.01 C per CuCl ₂ (393 mAh / g) content of the positive electrode.

Table 6 shows the specific capacity (per CuCl ₂ weight) of discharge and charge in 1 to 5 cycles in the charge / discharge test using the Li ion secondary battery of Inventive Example 2-8.
Table 10 shows the specific capacity (per CuCl ₂ weight) of 1 to 3 cycles of discharge and charge in the charge / discharge test using the Li ion secondary battery of Comparative Example 2-2.

  As is clear from the comparison between Table 9 and Table 10, the Li ion secondary battery of Example 2-8 of the present invention in which the inactive layer was formed was the Li ion secondary battery of Comparative Example 2-2 having no inactive layer. Comparing the transition of the charge / discharge specific capacity, it was confirmed that the decrease in capacity was small even when the number of cycles passed, and it was possible to provide a Li ion secondary battery having excellent battery characteristics. On the other hand, it was found that the Li-ion secondary battery of Comparative Example 2-2 had a charge / discharge specific capacity that decreased greatly with the passage of cycles, and was unable to be charged after the third cycle, and exhibited undesirable characteristics.

[Verification Example 2-4]
A coin cell (Li ion secondary battery) of Invention Example 2-9 was prepared by the following procedure.
In the same manner as in Invention Example 2-6, a SUS positive electrode case was put into a vacuum chamber and the pressure was reduced until the pressure became 10 ⁻³ torr or less, and platinum was deposited on the inner wall of the positive electrode case as an inactive layer at 5 mA for 15 minutes. did. A platinum net having a diameter of 12 mm was spot welded to the platinum vapor deposition case.
A positive electrode pellet containing CuCl ₂ as an active material was placed on the positive electrode current collector, and it was pressed for about 10 seconds at a pressure of 2 tons with a hand press machine, and the positive electrode was pressed onto the positive electrode current collector and attached. A gasket was attached to the negative electrode case attached with negative lithium. The positive electrode case and the negative electrode case were filled with the prepared electrolytic solution and caulked with an automatic caulking machine to produce a CR2023 type coin cell (Li ion secondary battery). A series of productions other than the preparation of the positive electrode case were all performed in a glove box in an argon atmosphere.
Through the above steps, a coin cell (Li ion secondary battery) of Inventive Example 2-9 was obtained.

A coin cell (Li ion secondary battery) of Comparative Example 2-3 was prepared by the following procedure.
In a glove box in an argon atmosphere, LiPF ₆ powder was dissolved in electrolyte grade FEC (manufacturer: Kishida Chemical Co., Ltd., LBG32051, water content: 50 ppm or less) to prepare a 1M concentration LiPF ₆ -FEC non-aqueous electrolyte.
Except for LiPF ₆ -FEC non-aqueous electrolyte, using the same battery material and the same positive electrode and negative electrode case as the test cell produced in Inventive Example 2-9, the same method as in Inventive Example 2-9, LiPF ₆ − A coin cell (Li ion secondary battery) of Comparative Example 2-3 containing an FEC nonaqueous electrolytic solution was obtained.

The produced coin cells of Invention Example 2-9 and Comparative Example 2-3 were installed in a thermostatic chamber set at 21 ° C., and connected to an automatic charge / discharge test apparatus to measure changes in battery voltage over time.
FIG. 15 shows the measurement results of changes over time in the battery voltage in Verification Example 2-4.
As is clear from the results shown in FIG. 15, as in Inventive Example 2-9, an inactive layer made of platinum is formed on the inner wall of the positive electrode case, and Li ion two-component electrolyte using LiPF ₆ -MFA nonaqueous electrolyte is used. The secondary battery is capable of realizing a Li-ion secondary battery having a stable battery characteristic with little change with time in voltage as compared with the Li-ion secondary battery of Comparative Example 2-3 in which an inactive layer is not formed in the positive electrode case. confirmed.

10 Li-ion secondary battery (secondary battery)
11 Positive electrode case 12 Negative electrode case 14 Separator 15 Positive electrode 16 Positive electrode current collector 17 Negative electrode 18 Negative electrode current collector

Claims (23)

A negative electrode including a negative electrode active material capable of releasing lithium ions by the first discharge and taking in and releasing lithium ions by subsequent charge and discharge, a positive electrode having a positive electrode active material including a metal chloride, a lithium salt, and a nonaqueous solvent A non-aqueous electrolyte containing
A secondary battery, wherein at least one of the non-aqueous solvents contains a halide of a carboxylic acid ester, and starts from discharge.   The positive electrode active material is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, 2. The secondary battery according to claim 1, comprising at least one metal chloride of Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, and Bi. The secondary battery according to claim ₂ , wherein the positive electrode active material includes at least one of FeCl ₂ , BiCl ₃ , and CuCl ₂ .   4. The secondary battery according to claim 2, wherein the metal chloride contained in the positive electrode active material is in the form of particles and has a particle size of 1 [mu] m or less. The negative electrode active material was substituted with metallic lithium, lithium-inserted carbon material, Si-Li alloy, Sn-Li alloy, TiO ₂ -based titanium oxide incorporating lithium, Li ₄ Ti ₅ O ₁₂ and different elements. Lithium titanium oxide, metal oxide incorporating lithium, amorphous tin composite oxide incorporating lithium, metal nitride incorporating lithium, metal phosphide incorporating lithium, lower oxide of silicon incorporating lithium , Conversion negative electrode material incorporating lithium, Sn-M (provided M = Ni, Fe, Co, Cu, V, Ag, Sb) alloy incorporating lithium, and composite material incorporating lithium The secondary battery according to claim 1, further comprising:   The secondary battery according to claim 5, wherein the negative electrode active material includes at least one of metallic lithium, a carbon material into which lithium is inserted, a Si—Li alloy, and a Sn—Li alloy. A negative electrode including a negative electrode active material capable of capturing lithium ions by first charging and then releasing and capturing lithium ions by subsequent charging, a positive electrode having a positive electrode active material including metal and lithium chloride, a lithium salt, and a nonaqueous solvent A non-aqueous electrolyte containing
A secondary battery characterized in that at least one of the non-aqueous solvents contains a halide of a carboxylic acid ester, and starts from charging.   The positive electrode active material is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, The secondary battery according to claim 7, comprising at least one metal selected from Sn, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, and Bi.   The secondary battery according to claim 8, wherein the positive electrode active material includes at least one of Fe, Bi, and Cu.   The secondary battery according to claim 8, wherein the metal chloride contained in the positive electrode active material is in the form of particles and has a particle size of 1 μm or less. The negative electrode active material is a carbon material, Si, Sn, TiO ₂ series titanium oxide, metal oxide, amorphous tin composite oxide, metal nitride, metal phosphide, lower oxide of silicon, conversion negative electrode material, Including at least one of Sn-M (however, M = Ni, Fe, Co, Cu, V, Ag, Sb) alloy, Sn-Si-O based composite material, Sn-Co-C based composite material The secondary battery according to claim 7, wherein:   The secondary battery according to claim 11, wherein the negative electrode active material includes at least one of a carbon material, Si, and Sn. 2. The halide of the carboxylic acid ester is a halide in which part or all of hydrogen in CHX ₂ COOR (where X = halogen atom, R = hydrocarbon group) is halogenated. The secondary battery as described in any one of thru | or 12. The secondary battery according to claim 13, wherein the halide of the carboxylic acid ester is CHF ₂ COOCH ₃ (methyl-2,2-difluoroacetate). The lithium salt is LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiTaF ₆ , LiNbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F _{5 SO 2) 2, LiC (CF} 3 SO 2) 3, LiBF 3 (C 2 F 5), LiB (C 6 F 5) 4, LiPF 3 (C 2 F 5) 3, LiClO 4, LiB (C 2 O ₄₎ of the _two, the secondary battery of claims 1 to 14 any one claim, characterized in that it comprises at least one. The secondary battery according to claim 15, wherein the lithium salt includes at least one of LiPF ₆ , LiBF ₄ , and LiAsF ₆ . A non-aqueous solution comprising a negative electrode containing a negative electrode active material capable of taking in lithium ions by charge and discharge, a positive electrode having a positive electrode active material containing a metal halide, a positive electrode case containing the positive electrode, a lithium salt and a non-aqueous solvent An electrolyte solution,
The inner surface of the positive electrode case is made of a material that is insoluble in the non-aqueous electrolyte and is made of a material that is chemically inactive with respect to the oxidation-reduction reaction of the positive electrode active material and positive electrode constituent materials other than the positive electrode active material. The secondary battery according to claim 1, wherein an active layer is formed.   The positive electrode current collector is disposed between an inner surface of the positive electrode case and the positive electrode, and the inert layer is further formed on the surface of the positive electrode current collector. The secondary battery according to 17.   The secondary battery according to claim 17, wherein the inactive layer is made of Al or an Al alloy.   The secondary battery according to claim 17, wherein the inactive layer is made of conductive carbon.   The secondary battery according to claim 17, wherein the inactive layer is made of Pt or a Pt alloy.   19. The secondary battery according to claim 17, wherein the inactive layer is made of a ternary copolymer synthetic rubber having a C double bond in a polymer main chain.   23. The secondary battery according to claim 22, wherein the synthetic rubber constituting the inactive layer is an ethylene / propylene / diene terpolymer.

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