WO2019003440A1

WO2019003440A1 - Nonaqueous electrolyte battery and battery pack

Info

Publication number: WO2019003440A1
Application number: PCT/JP2017/024228
Authority: WO
Inventors: 大山本; 亜希長谷川
Original assignee: 株式会社東芝; 東芝インフラシステムズ株式会社
Priority date: 2017-06-30
Filing date: 2017-06-30
Publication date: 2019-01-03
Also published as: JP6946429B2; JPWO2019003440A1

Abstract

One embodiment of the present invention provides a nonaqueous electrolyte battery. This battery is provided with: a positive electrode that comprises a positive electrode material layer; a negative electrode; and a nonaqueous electrolyte. The nonaqueous electrolyte is held by at least the positive electrode material layer. The positive electrode material layer contains a positive electrode active material and a first group that is selected from among PF2(=O)O-, PF(=O)(O-)2 and a combination thereof. The nonaqueous electrolyte contains LiPF6 and a second group that is selected from among PF2(=O)O-, PF(=O)(O-)2 and a combination thereof. The content rate C1 of the first group in the positive electrode material layer is from 0.3% by mass to 2% by mass (inclusive). The content rate C2 of the second group in the nonaqueous electrolyte is from 0.1% by mass to 1.5% by mass (inclusive). The content rate C1 is higher than the content rate C2.

Description

Non-aqueous electrolyte battery and battery pack

Embodiments of the present invention relate to non-aqueous electrolyte batteries and battery packs.

In recent years, non-aqueous electrolyte secondary batteries in which charge and discharge are performed by the movement of Li ions between the negative electrode and the positive electrode are electric vehicles (EVs) and hybrid vehicles (HEVs) from the viewpoint of energy problems and environmental problems. It is expected as a large power storage device for stationary power generation systems such as solar power generation and solar power generation.

Such non-aqueous electrolyte secondary batteries are also envisioned for use in cold regions. Therefore, in the non-aqueous electrolyte secondary battery, improvement of output performance in a low temperature environment is required so that large current can be input / output even in a low temperature environment.

Unexamined-Japanese-Patent No. 2015-198006

It is an object of the present invention to provide a non-aqueous electrolyte battery capable of exhibiting excellent output performance under a low temperature environment, and a battery pack provided with the non-aqueous electrolyte battery.

According to a first embodiment, a non-aqueous electrolyte battery is provided. This non-aqueous electrolyte battery comprises a positive electrode including a positive electrode material layer, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte is held at least in the positive electrode material layer. The positive electrode material layer includes a positive electrode active material, and a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The non-aqueous electrolyte comprises lithium hexafluorophosphate and a _second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof . The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less. The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less. The content ratio C1 is larger than the content ratio C2.

According to a second embodiment, a battery pack is provided. The battery pack includes the non-aqueous electrolyte battery according to the first embodiment.

FIG. 1 is a cross-sectional view of a non-aqueous electrolyte battery of a first example according to the first embodiment cut in the thickness direction. FIG. 2 is an enlarged cross-sectional view of a portion A of FIG. FIG. 3 is a partially cutaway perspective view of a non-aqueous electrolyte battery of a second example according to the first embodiment. FIG. 4 is an enlarged cross-sectional view of a portion B of FIG. FIG. 5 is an exploded perspective view of an example battery pack according to the second embodiment. FIG. 6 is a block diagram showing an electric circuit of the battery pack shown in FIG.

Embodiments will be described below with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the embodiment, and there are places where the shape, size, ratio, etc. are different from those of the actual device. The design can be changed as appropriate.

First Embodiment
According to a first embodiment, a non-aqueous electrolyte battery is provided. This non-aqueous electrolyte battery comprises a positive electrode including a positive electrode material layer, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte is held at least in the positive electrode material layer. The positive electrode material layer includes a positive electrode active material, and a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The non-aqueous electrolyte comprises lithium hexafluorophosphate and a _second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof . The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less. The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less. The content ratio C1 is larger than the content ratio C2.

The inventors of the present invention conducted intensive studies to enhance the output performance of the battery in a low temperature environment. As one approach, it has been studied to add an additive to the non-aqueous electrolyte to promote dissociation of Li salt at the positive electrode interface and to suppress metal elution from the positive electrode. However, when added to the non-aqueous electrolyte, the additive that exerts an effect in the positive electrode does not necessarily all act on the positive electrode, and a part thereof moves to the negative electrode side, so the effect corresponding to the addition amount It turned out that it can not be used enough. As a result of earnestly researching in view of such a problem, the present inventors have realized the nonaqueous electrolyte battery according to the first embodiment.

In the non-aqueous electrolyte battery according to the first embodiment, the first group and the second group can promote the dissociation of Li ions from the non-aqueous electrolyte. Since the non-aqueous electrolyte is held at least in the positive electrode material layer, the first group and the second group can efficiently supply Li ions in the vicinity of the interface between the positive electrode material layer and the non-aqueous electrolyte. The interface between the positive electrode material layer containing the positive electrode active material and the non-aqueous electrolyte can be a reaction site of the positive electrode. The Li ions supplied near the reaction field of the positive electrode need to move a short distance when participating in the positive electrode reaction at this interface. As a result, the resistance value at the time of charge and discharge in a low temperature environment can be lowered.

In addition, the first group and the second group can promote the positive electrode reaction at the interface between the positive electrode material layer and the non-aqueous electrolyte. In the nonaqueous electrolyte battery according to the first embodiment, the content ratio C1 of the first group in the positive electrode material layer is 0.3 mass% or more and 2 mass% or less, and the content ratio of the second group in the nonaqueous electrolyte C2 is 0.1 mass% or more and 1.5 mass% or less, and the content rate C1 is larger than the content rate C2. In the non-aqueous electrolyte battery in which the content ratios C1 and C2 satisfy this condition, the first group contained in the positive electrode material layer can be prevented from migrating into the non-aqueous electrolyte. Therefore, in the nonaqueous electrolyte battery according to the first embodiment, a sufficient amount of the first group can be kept near the reaction site of the positive electrode. Therefore, the nonaqueous electrolyte battery according to the first embodiment can fully utilize the effect corresponding to the content ratio C1 of the first group.

And, the first group contained in the positive electrode material layer at the content ratio C1 and the second group contained in the non-aqueous electrolyte at the content ratio C2 suppress the decomposition of lithium hexafluorophosphate contained in the non-aqueous electrolyte It can also be done. The decomposition product of lithium hexafluorophosphate adheres on the electrode and becomes the battery's resistive component. Particularly in a low temperature environment, when the movement distance of Li increases due to the generation of the resistance component, the battery resistance increases. Since generation of such a resistance component can be prevented, the non-aqueous electrolyte battery according to the first embodiment can exhibit a lower resistance value.

Thus, in the non-aqueous electrolyte battery according to the first embodiment, Li ions can be supplied to the vicinity of the reaction site of the positive electrode, and the positive electrode reaction can be promoted. In addition, it is possible to suppress the generation of the resistance component that causes the increase in battery resistance. As a result, the non-aqueous electrolyte battery according to the first embodiment can exhibit excellent output performance under a low temperature environment.

Hereinafter, the nonaqueous electrolyte battery according to the first embodiment will be described in more detail.
Lithium hexafluorophosphate contained in the non-aqueous electrolyte can be represented, for example, by the chemical formula LiPF ₆ . In the non-aqueous electrolyte, at least a portion of lithium hexafluorophosphate may be dissociated into Li ion (Li ⁺ ) and hexafluorophosphate anion (PF ₆ ⁻ ). The first group and the second group included in the non-aqueous electrolyte battery according to the first embodiment can, for example, promote this dissociation. In addition, as described above, the first group and the second group can also suppress the decomposition of lithium hexafluorophosphate. Here, the decomposition of lithium hexafluorophosphate is not a Li ⁺ dissociation from LiPF _6, means the change in the structure of the hexafluorophosphate anion. The decomposition of lithium hexafluorophosphate can be, for example, a reaction to form at least one selected from the group consisting of HF, PF ₅ , POF ₃ and LiF.

The first group contained in the positive electrode material layer is selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The first group may be either PF ₂ (= O) O ⁻ or PF (= O) (O ⁻ ) ₂ , or PF ₂ (= O) O ⁻ and PF (= O) It may be a combination of (O ⁻ ) ₂ .

The positive electrode material layer can include, for example, a first compound having a first group. Alternatively, the positive electrode active material may contain the first group.

The second group contained in the non-aqueous electrolyte is selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The second group may be either PF ₂ (= O) O ⁻ or PF (= O) (O ⁻ ) ₂ , or PF ₂ (= O) O ⁻ and PF (= O) It may be a combination of (O ⁻ ) ₂ .

The non-aqueous electrolyte can include, for example, a second compound having a second group.

The first compound and the second compound may be the same or different. The first compound and / or the second compound may further contain, as a compound, an element of hydrogen and / or an alkali metal element such as lithium. In addition, the first compound and the second compound can further include at least one group selected from the group consisting of an alkyl group, a carbonyl group, a hydroxyl group and an alkyllithium group as the compound. In addition, the first compound and / or the second compound may contain a phosphate ester moiety or the like. The first compound and / or the second compound may be in the form of a compound in the battery. Alternatively, the first compound and / or the second compound may be at least partially dissociated in the battery. The fact that the positive electrode material layer includes the first group also includes, for example, a state in which the positive electrode material layer includes a first group formed by dissociation of at least a part of the first compound. Similarly, the non-aqueous electrolyte containing the second group also includes, for example, a state in which the non-aqueous electrolyte contains the second group formed by the dissociation of at least a part of the second compound. .

The non-aqueous electrolyte battery according to the first embodiment including the first group and the second group in the positive electrode material layer and the non-aqueous electrolyte at the content ratios C1 and C2 described above, respectively, from the non-aqueous electrolyte It is possible to achieve the promotion of the supply of Li ions to the vicinity of the reaction field of the positive electrode by the promotion of the dissociation of Li ions, the promotion of the positive reaction and the suppression of the decomposition of lithium hexafluorophosphate in the non-aqueous electrolyte . While not wishing to be bound by theory, it is expected that the mechanism of lithium hexafluorophosphate decomposition inhibition is mainly similar to the mechanism of Li ion dissociation promotion. The first group and the second group can also contribute to the stable supply of Li ions to the positive electrode reaction site by suppressing the decomposition of lithium hexafluorophosphate, which is a source of Li ions it can.

In a non-aqueous electrolyte battery in which the content ratio C1 of the first group in the positive electrode material layer is less than 0.3% by mass, the first group present in the positive electrode material layer is too small. In such a battery, the suppression of the decomposition of lithium hexafluorophosphate near the reaction site of the positive electrode and the dissociation promoting effect of the Li salt are not sufficiently exhibited. On the other hand, in the non-aqueous electrolyte battery in which the content ratio C1 exceeds 2% by mass, the ratio of the portion not directly involved in the electrode reaction in the first group contained in the positive electrode material layer is too high. In such a battery, in the positive electrode material layer, a portion of the first group not directly involved in the electrode reaction inhibits the electrode reaction, and the resistance in a low temperature environment increases. Here, as one of the reasons why the electrode reaction is inhibited, for example, a portion of the first group which does not directly participate in the electrode reaction is a distance between the positive electrode active material and the conductive agent which may be contained in the positive electrode material layer. It can be mentioned that it spreads out.

In addition, in a non-aqueous electrolyte battery in which the content ratio C2 of the second group in the non-aqueous electrolyte is less than 0.1% by mass, the second group present in the non-aqueous electrolyte is too small. In such cells, migration of the first group from the positive electrode material layer to the non-aqueous electrolyte is induced. The moved first group diffuses in the non-aqueous electrolyte. As a result, the amount of the first group present in the vicinity of the interface between the positive electrode material layer and the non-aqueous electrolyte is reduced, and supply of Li ions to the vicinity of the reaction field of the positive electrode and promotion of positive electrode reaction at this interface It can not express the effect. Moreover, in such a battery, the decomposition of lithium hexafluorophosphate in the non-aqueous electrolyte can not be sufficiently suppressed. On the other hand, in a non-aqueous electrolyte battery in which the content ratio C2 in the non-aqueous electrolyte exceeds 1.5% by mass, a large amount of second groups are present in the interface between the positive electrode material layer and the non-aqueous electrolyte and in the non-aqueous electrolyte. There is. In such a battery, involvement of lithium hexafluorophosphate in the positive electrode reaction is inhibited, and resistance increases. In addition, when the content ratio C2 in the non-aqueous electrolyte exceeds 1.5% by mass, not only the viscosity of the non-aqueous electrolyte increases but also a component that inhibits the battery reaction is present in the non-aqueous electrolyte. Therefore, in such a non-aqueous electrolyte battery, the low temperature resistance is increased, and as a result, the output performance is reduced.

The content rates C1 and C2 differ in the mass and specific gravity of the positive electrode material layer and the non-aqueous electrolyte, which are denominators. However, since the positive electrode material layer can contain, for example, a transition metal, it can have a specific gravity greater than that of the non-aqueous electrolyte. Therefore, the fact that the content ratio C1 is greater than the content ratio C2 means that the group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and a combination thereof is the reaction of the positive electrode. It can be said that the non-aqueous electrolyte in the same volume near the field and the positive electrode material layer are more contained in the positive electrode material layer than in the non-aqueous electrolyte.

Furthermore, in this preferred embodiment, for example, a group in which the content ratio C1 in the positive electrode material layer is selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof It can exceed the solubility in non-aqueous electrolytes. In such an embodiment, a sufficient amount of the compound continues to be present at the interface between the positive electrode material layer and the non-aqueous electrolyte even if part of the first group moves from the positive electrode material layer to the non-aqueous electrolyte It is possible to further reduce the resistance of the battery in a low temperature environment.

On the other hand, a non-aqueous electrolyte battery in which the content ratio C2 of the second group is the content ratio C1 or more of the first group exhibits high resistance. While not wishing to be bound by theory, it is believed that the reason such non-aqueous electrolyte cells exhibit high resistance is as follows.

First, in a non-aqueous electrolyte battery in which the content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more, the first material in an amount sufficient to promote the positive electrode reaction is It can be said that it exists. However, in the nonaqueous electrolyte battery in which the content ratio C2 of the second group is the content ratio C1 or more of the first group, the second group in the nonaqueous electrolyte is an interface between the nonaqueous electrolyte and the positive electrode material layer. Move to the vicinity. In such a non-aqueous electrolyte battery, the first group is present in a sufficient amount in the portion in contact with the non-aqueous electrolyte in the positive electrode material layer, and the second group in the portion in contact with the positive electrode material layer in the non-aqueous electrolyte. Become ubiquitous. The second group unevenly distributed in the non-aqueous electrolyte in the vicinity of the reaction field of the positive electrode inhibits the movement of Li to the vicinity of the positive electrode reaction field. As a result, such non-aqueous electrolyte batteries exhibit high resistance.

Lithium hexafluorophosphate can exhibit a high degree of dissociation in nonaqueous solvents compared to other lithium salts. This means that lithium hexafluorophosphate can provide more Li ions in the non-aqueous electrolyte as compared to other Li salts. A non-aqueous electrolyte containing more Li in the ion state can exhibit higher Li ion conductivity. This is due not only to the large amount of Li ions that can be moved, but also to the fact that Li ions can move smoothly. Therefore, the non-aqueous electrolyte containing lithium hexafluorophosphate can exhibit higher Li ion conductivity than the non-aqueous electrolyte containing no lithium hexafluorophosphate. Therefore, the non-aqueous electrolyte containing lithium hexafluorophosphate can promote the supply of Li near the reaction site of the positive electrode. In the non-aqueous electrolyte battery in which the non-aqueous electrolyte does not contain lithium hexafluorophosphate, not only the decomposition suppressing effect of the Li supporting salt by the first group and the second group can not be utilized, but also the first group and The second group may act as a resistance component and may exhibit high resistance in a low temperature environment.

Next, the nonaqueous electrolyte battery according to the first embodiment will be described in more detail.

The non-aqueous electrolyte battery according to the first embodiment includes a positive electrode, a negative electrode, and a non-aqueous electrolyte.

The positive electrode includes a positive electrode material layer.
The positive electrode material layer further includes a positive electrode active material. That is, the positive electrode material layer can also be referred to as a positive electrode active material-containing layer. In addition, the positive electrode material layer further includes a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The positive electrode material layer can further contain a conductive agent and a binder, as needed.

The positive electrode can further include a positive electrode current collector. The positive electrode material layer can be formed on the positive electrode current collector. The positive electrode current collector can have, for example, a first surface and a second surface as its back surface. The positive electrode material layer may be formed on both surfaces of the positive electrode current collector, or may be formed on one surface.

The positive electrode current collector can include a portion not carrying the positive electrode material layer on the surface. This portion can, for example, serve as the positive electrode tab. Alternatively, the positive electrode can further comprise a positive electrode tab separate from the positive electrode current collector.

The negative electrode can include a negative electrode current collector and a negative electrode material layer formed on the negative electrode current collector.

The negative electrode current collector can have, for example, a first surface and a second surface as its back surface. The negative electrode material layer may be formed on both surfaces of the negative electrode current collector, or may be formed on one surface.

The negative electrode current collector can include a portion not carrying the negative electrode material layer on the surface. This portion can, for example, serve as the negative electrode tab. Alternatively, the negative electrode can further comprise a negative electrode tab separate from the negative electrode current collector.

The negative electrode material layer can include a negative electrode active material. That is, the negative electrode material layer can also be called a negative electrode active material containing layer. The negative electrode material layer can include, for example, a negative electrode active material having an operating potential of 0.7 V (vs. Li ^/ Li ⁺ ) or more. The negative electrode material layer may contain one kind of such negative electrode active material, or may contain a combination of a plurality of such negative electrode active materials. The negative electrode material layer can optionally further include a conductive agent and a binder.

The positive electrode and the negative electrode can constitute an electrode group. For example, in the electrode group, the positive electrode material layer and the negative electrode material layer can face each other through the separator. The structure of the electrode group is not particularly limited, and various structures can be adopted. For example, the electrode group can have a stacked structure. The stack-type electrode group is obtained, for example, by laminating a plurality of positive electrodes and negative electrodes with a separator interposed between a positive electrode material layer and a negative electrode material layer. Alternatively, the electrode group can have, for example, a wound structure. The wound electrode group is obtained, for example, by spirally winding the positive electrode, the separator and the negative electrode.

The non-aqueous electrolyte includes lithium hexafluorophosphate and a _second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof.

The non-aqueous electrolyte is held at least in the positive electrode material layer. For example, the positive electrode material layer described above can have pores. For example, part of the non-aqueous electrolyte may be retained in the positive electrode material layer in a state of being infiltrated (in an impregnated state) in the pores of the positive electrode material layer. The negative electrode material layer and the separator can also have pores. The other part of the non-aqueous electrolyte can be retained in the negative electrode material layer, for example, in a state (impregnated state) in which the pores of the negative electrode material layer enter. The other part of the non-aqueous electrolyte can be retained in the separator, for example, in a state of being infiltrated in the pores of the separator (in an impregnated state). As a result of these, the non-aqueous electrolyte can be held by the electrode group.

The non-aqueous electrolyte battery according to the first embodiment can further include a negative electrode terminal and a positive electrode terminal. The negative electrode terminal can function as a conductor for moving electrons between the negative electrode and the external terminal by electrically connecting a part of the negative electrode terminal to a part of the negative electrode. The negative electrode terminal can, for example, be connected to the negative electrode current collector, in particular to the negative electrode tab. Similarly, the positive electrode terminal can function as a conductor for moving electrons between the positive electrode and the external circuit by electrically connecting a part of the positive electrode terminal to a part of the positive electrode. The positive electrode terminal can, for example, be connected to a positive electrode current collector, in particular to a positive electrode tab.

The nonaqueous electrolyte battery according to the first embodiment can further include an exterior member. The exterior member can accommodate the electrode group and the non-aqueous electrolyte. The non-aqueous electrolyte can be held by the electrode group in the exterior member. A part of each of the positive electrode terminal and the negative electrode terminal can be extended from the exterior member.

Hereinafter, the material of each member which can be equipped with the non-aqueous electrolyte battery according to the embodiment will be described in detail.

(1) Positive electrode As a positive electrode collector, metal foils, such as aluminum and copper, can be used, for example. When a positive electrode tab separate from the positive electrode current collector is used, the material of the positive electrode tab is preferably the same as the material of the positive electrode current collector in order to suppress the contact resistance with the positive electrode current collector.

The positive electrode active material is not particularly limited as long as it can occlude and release lithium or lithium ions. Examples of the positive electrode active material include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium cobalt composite oxide (for example, Li _x CoO ₂ , 0 <x ≦ 1), lithium nickel composite oxide (for example, , Li _x NiO ₂ , 0 <x ≦ 1), lithium nickel cobalt manganese complex oxide (eg, Li _x Ni _1-abc Co _a Mn _b M 1 _c O ₂ can have a composition represented by the general formula M 1 is at least one selected from the group consisting of Mg, Al, Si, Ti, Zn, Zr, Ca, W, Nb and Sn, and each subscript is −0.2 ≦ x ≦ 0.5 , 0 <a <0.4 (preferably 0.25 <a <0.4), 0 <b <0.5, 0 ≦ c <0.1), lithium nickel cobalt composite oxide (For example, Li _x Ni _{1 -e} Co _e O ₂ , 0 <x ≦ 1, 0 <e <1), lithium manganese cobalt composite oxide (for example, Li _x Mn _f Co _1-f O ₂ , 0 <x ≦ 1, 0 <f <1), lithium nickel cobalt aluminum composite oxide (for example, Li _x Ni _1-gh Co _g Al _h O ₂ , 0 <x ≦ 1, 0 <g <1, 0 <h <1), lithium manganese complex oxide (eg Li _x Mn ₂ O ₄ , Li _x MnO ₂ , 0 <x ≦ 1), lithium phosphorus oxide having an olivine structure (for example, Li _x FePO ₄ , Li _x MnPO ₄ , Li _x Mn _1-i Fe _i PO ₄ , Li _x CoPO ₄ , 0 <x ≦ 1, 0 <i <1), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), and vanadium oxide (eg, V ₂ O ₅ ). The type of the positive electrode active material contained in the positive electrode material layer may be one, or two or more.

The positive electrode active material may be a mixed phase with a phase including a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof.

The conductive agent that can be contained in the positive electrode material layer preferably contains a carbon material. Examples of the carbon material include acetylene black, ketjen black, furnace black, graphite, carbon nanotubes and the like. The positive electrode material layer can include one or more of the above-described carbon materials, or can further include another conductive agent.

Moreover, the binder which the positive electrode material layer can contain is not particularly limited. For example, as a binder, a polymer well dispersed in a mixing solvent for slurry preparation, such as n-methylpyrrolidone (NMP) can be used. Examples of such a polymer include polyvinylidene fluoride, hexafluoropropylene and polytetrafluoroethylene.

Specific examples of the first compound which can be contained in the positive electrode material layer in the preparation of the positive electrode include monofluorophosphoric acid (PF (= O) (OH) ₂ ) and lithium monofluorophosphate (PF (= O) ( OLi) ₂ ), sodium monofluorophosphate (PF (= O) (ONa) ₂ ), potassium monofluorophosphate (PF (= O) (OK) ₂ ), dimethyl monofluorophosphate (PF (= O) (OCH ₃ ) ₂ ), diethyl monofluorophosphate (PF (= O) (OC ₂ H ₅ ) ₂ ), ethyl methyl monofluorophosphate (PF (= O) (OCH ₃ ) (OC ₂ H ₅ )) , Difluorophosphoric acid (PF ₂ (= O) (OH)), difluorophosphoric acid 0.5 hydrate (PF ₂ (= O) (OH) · 0.5H ₂ O), lithium difluorophosphate (PF ₂ (= O) (OLi)), sodium difluorophosphate _{PF 2 (= O) (ONa} )), potassium difluorophosphate _{(PF 2 (= O) (} OK)), methyl difluoro phosphate _{(PF 2 (= O) (} OCH 3)), and ethyl difluorophosphate ( _{PF 2 (= O) (OC} 2 H 5)) and the like.

The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less. The content ratio C1 is the mass of the group PF ₂ (= O) O ⁻ , the mass of the group PF (= O) (O ⁻ ) ₂ , or the group contained in the positive electrode material layer, where the mass of the positive electrode material layer is 100%. The sum of the mass of PF ₂ (= O) O ^{− and} the mass of the group PF (= O) (O ⁻ ) ₂ is shown as a percentage. The content ratio C1 is preferably more than 0.5% by mass and 2% by mass or less, and more preferably 1% by mass or more and 2% by mass or less.

The content of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer is 80% by mass or more and 97% by mass or less, respectively, with respect to the mass of the positive electrode material layer (100%) % Or more and 10 mass% or less and 0.5 mass% or more and 10 mass% or less, 90 mass% or more and 96 mass% or less, 1 mass% or more and 8 mass% or less, and 1 mass% or more and 8 mass% or less It is more preferable that

(2) Negative electrode As a negative electrode collector, metal foil, such as aluminum and copper, can be used, for example. When a negative electrode tab separate from the negative electrode current collector is used, the material of the negative electrode tab is preferably the same as the material of the negative electrode current collector in order to suppress the contact resistance with the negative electrode current collector. .

The negative electrode active material is not particularly limited as long as it can occlude and release lithium or lithium ions. As an example of the negative electrode active material, for example, lithium titanate having a crystal structure of spinel type (for example, Li _{4 + y} Ti ₅ O ₁₂ (y is in the range of 0 ≦ y ≦ 3 depending on the state of charge) Can vary in composition), lithium titanate with a ramsdellite type crystal structure (eg, Li _{2 + z} Ti ₃ O ₇ ) (z is 0 ≦ z ≦ 2 depending on the state of charge) Can vary in the following ranges), anatase-type, rutile-type or bronze-type titanium-containing oxide, a niobium titanium composite oxide having a monoclinic crystal structure, and an orthorhombic-type Examples include Na-containing niobium-titanium composite oxides having a crystal structure. These negative electrode active materials can exhibit an operating potential of 0.7 V (vs. Li ^/ Li ⁺ ) or more. By using the negative electrode active material having an operating potential of 0.7 V (vs. Li ^/ Li ⁺ ) or more, it is possible to prevent the formation of lithium dendrite in low temperature operation. The type of the negative electrode active material contained in the negative electrode material layer may be one, or two or more.

As the conductive agent and the binder which the negative electrode material layer can contain, those similar to those which the positive electrode material layer can contain can be used.

The content of the negative electrode active material, the conductive agent, and the binder in the negative electrode material layer is 80% by mass or more and 98% by mass or less, 1% by mass or more and 10% by mass or less, based on the mass of the negative electrode material layer. % Or more and 10% by mass or less is preferable, and 90% by mass or more and 94% by mass or less, 2% by mass or more and 8% by mass or less, and 1% by mass or more and 5% by mass or less.

(3) Nonaqueous Electrolyte The nonaqueous electrolyte can include, for example, a nonaqueous solvent, an electrolyte (Li supporting salt) dissolved in the nonaqueous solvent, and an additive.

Lithium hexafluorophosphate (LiPF ₆ ) can be included in the non-aqueous electrolyte, for example, as an electrolyte. As the electrolyte, lithium hexafluorophosphate may be used alone, or a combination of lithium hexafluorophosphate and one or more other electrolytes may be used. Examples of electrolytes other than lithium hexafluorophosphate include, for example, lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethanesulfonic acid Lithium salts such as lithium (LiCF ₃ SO ₃ ) can be mentioned.

It is preferable that 50 mass% or more of mass of electrolyte is lithium hexafluorophosphate, and it is more preferable that it is 90 mass% or more.

As non-aqueous solvents, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ) And -BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like.

As the non-aqueous solvent, one type of solvent may be used alone, or a mixed solvent in which two or more types of solvents are mixed may be used.

The amount of electrolyte dissolved in the non-aqueous solvent is preferably 0.5 mol / L to 3 mol / L. If the amount of dissolution is too high, it may not be completely soluble in the electrolyte.

The second compound having a second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and a combination thereof is, for example, non-aqueous as an additive. It may be included in the electrolyte.

Specific examples of the second compound that can be included in the preparation of the non-aqueous electrolyte can include the same compounds as the specific examples that can be used as the first compound described above.

The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less. The content ratio C2 is the mass of the group PF ₂ (= O) O ⁻ , the mass of the group PF (= O) (O ⁻ ) ₂ , or the group contained in the non-aqueous electrolyte, where the mass of the non-aqueous electrolyte is 100%. The sum of the mass of PF ₂ (= O) O ^{− and} the mass of the group PF (= O) (O ⁻ ) ₂ is shown as a percentage. The content ratio C2 is preferably 0.3% by mass or more and 1.4% by mass or less, and more preferably 0.5% by mass or more and 1.3% by mass or less.

The non-aqueous electrolyte can further include one or more additives other than the second compound. As an additive other than the second compound, for example, vinylene carbonate (VC), fluorovinylene carbonate, methylvinylene carbonate, fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene Carbonate, dipropylvinylene carbonate, vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate, propane sultone, butane sultone, lithium trifluoromethane sulfonate (LiCF ₃ SO ₃ ), lithium bisoxalatoborate (LiBOB), lithium bis (fluorosulfonyl) imide _{_{[LiN (SO 2 F) 2}} ], bi Trifluoromethylsulfonyl imide _{_{[LiN (CF 3 SO 2)}} 2] , and the like. These additives are preferably contained in the non-aqueous electrolyte in a content ratio of 5% by mass or less, and more preferably in a content ratio of 3% by mass or less. Also, these additives can be contained, for example, in the non-aqueous electrolyte in an amount of 0.1% by mass or more.

(4) Separator The separator is not particularly limited, and, for example, a microporous membrane, a woven fabric, a non-woven fabric, or a laminate of the same material or different materials among them can be used. Examples of the material forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, and cellulose.

(5) Exterior member As the exterior member, for example, a metal container or a laminate film container can be used, but it is not particularly limited.

By using a metal container as the exterior member, a non-aqueous electrolyte battery excellent in impact resistance and long-term reliability can be realized. By using a laminate film container as the container, it is possible to realize a non-aqueous electrolyte battery excellent in corrosion resistance and to reduce the weight of the non-aqueous electrolyte battery.

As the metal container, for example, one having a wall thickness of 0.2 mm or more and 1 mm or less can be used. The metal container more preferably has a wall thickness of 0.3 to 0.8 mm or less.

The metal container preferably contains at least one selected from the group consisting of Fe, Ni, Cu, Sn and Al. The metal container can be made of, for example, aluminum, aluminum alloy, iron, nickel (Ni) plated iron, stainless steel (SUS) or the like. The aluminum alloy is preferably an alloy containing an element such as magnesium, zinc or silicon. When the alloy contains a transition metal such as iron, copper, nickel, or chromium, the content is preferably 1% by mass or less. As a result, long-term reliability and heat dissipation in a high temperature environment can be dramatically improved.

As the laminate film container, for example, one having a thickness in the range of 0.1 or more and 2 mm or less can be used. The thickness of the laminate film is more preferably 0.2 mm or less.
As a laminate film, for example, a multilayer film including a metal layer and a resin layer sandwiching the metal layer is used. The metal layer preferably contains a metal containing at least one selected from the group consisting of Fe, Ni, Cu, Sn and Al. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. As a material of a resin layer, polymeric materials, such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET), can be used, for example. The laminated film can be molded into the shape of the exterior member by sealing by heat fusion.

The shape of the exterior member may be flat (thin), square, cylindrical, coin, button or the like. The exterior member can have various dimensions depending on the application. For example, when the non-aqueous electrolyte battery according to the first embodiment is used for a use of a portable electronic device, the exterior member can be miniaturized according to the size of the mounted electronic device. Alternatively, in the case of a non-aqueous electrolyte battery loaded on a two- or four-wheeled automobile, the exterior member may be a container for a large battery.

(6) Positive Electrode Terminal and Negative Electrode Terminal The positive electrode terminal and the negative electrode terminal are desirably formed of, for example, aluminum or an aluminum alloy.

<Manufacturing method>
Below, the example of the manufacturing method of the non-aqueous electrolyte battery which concerns on 1st Embodiment is demonstrated.

_{PF 2 (= O) O -} , PF (= O) (O -) 2 and a compound having a group selected from the group consisting of not included in the positive electrode material layer, added to the non-aqueous electrolyte In the non-aqueous electrolyte battery prepared by including it as an agent, the content ratio C1 of the first group in the positive electrode material layer in the range of 0.3 mass% or more and 2 mass% or less and 0.1 mass% or more. The content ratio C2 of the second group in the nonaqueous electrolyte which is within the range of 5% by mass or less and smaller than the content ratio C1 can not be compatible. The reason is as follows. In such a battery, the supply of the compound having a group selected from the group consisting of PF ₂ (OO) O ⁻ , PF (OO) (O ⁻ ) ₂ and a combination thereof to the positive electrode material layer is not Only through the water electrolyte. The positive electrode material layer can have, for example, pores, and these pores can be channels of the non-aqueous electrolyte and can retain the non-aqueous electrolyte. In such cells, compounds having a group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (PFO) (O ⁻ ) ₂ and combinations thereof can be present only in the pores. Therefore, in such a battery, PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof in the cathode material layer which may further contain the cathode active material, the conductive agent and the binder. The content ratio C1 of the first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof in the non-aqueous electrolyte It becomes smaller than the content rate C2 of the 2nd group selected more.

In addition, a first group selected from the group consisting of PF ₂ (OO) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof is used in the positive electrode material layer, for example, 0.5 mass% or less Even in the case of a nonaqueous electrolyte battery which is contained in an amount and which does not contain such a group in the nonaqueous electrolyte, the contents C1 and C2 within the above range can not be compatible. In such a non-aqueous electrolyte battery, a part of the first group moves from the positive electrode material layer to the non-aqueous electrolyte. As a result, the content ratio of the first group selected from the group consisting of PF ₂ (OO) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof in the positive electrode material layer It will be less than 0.3% by mass with respect to the mass.

On the other hand, in the manufacturing method of the example described here, the first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and a combination thereof in the positive electrode material layer Selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof as an additive to the non-aqueous electrolyte as well. A compound having a second group (second compound) is added. Here, the blending ratio P1 (mass%) of the first compound to the mass of the slurry for preparing a positive electrode for preparing the positive electrode material layer, and the blending ratio P2 (mass%) of the second compound to the mass of the non-aqueous electrolyte Make it bigger.

The manufacturing method of this example will be specifically described below.
First, a positive electrode and a negative electrode are produced. The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a positive electrode mixture. Subsequently, for example, a powdery first compound is charged into the positive electrode mixture in a charging amount P1 (mass%). The first compound input amount P1 is a first compound selected from the group consisting of PF ₂ (= O) O ⁻ , PF (PFO) (O ⁻ ) _2, and a combination thereof in the nonaqueous electrolyte battery to be completed The content ratio C1 of the group is adjusted to be 0.3% by mass or more and 2% by mass or less. Subsequently, the obtained positive electrode mixture is added to a suitable solvent such as N-methylpyrrolidone. The mixture thus obtained is stirred to obtain a slurry for producing a positive electrode. The slurry for producing a positive electrode thus obtained is applied onto a positive electrode current collector, and the coated film is dried. By pressing the dried coating film, it is possible to obtain a positive electrode including the positive electrode current collector and the positive electrode material layer formed on the positive electrode current collector.

The negative electrode can be produced, for example, by the following procedure. First, a negative electrode active material, a conductive agent, and a binder are mixed to obtain a negative electrode mixture. The negative electrode mixture thus obtained is added to a suitable solvent such as N-methyl pyrrolidone, and the mixture is stirred to obtain a slurry for producing a negative electrode. The slurry for producing a negative electrode is applied to a negative electrode current collector, and the coating is dried. By pressing the dried coating film, it is possible to obtain a negative electrode provided with a negative electrode current collector and a negative electrode material layer formed on the negative electrode current collector.

Then, an electrode group is produced using the produced positive electrode and negative electrode, and, if necessary, a separator. Next, the produced electrode group is accommodated in an exterior member.

Meanwhile, a non-aqueous electrolyte is prepared. The non-aqueous electrolyte can be prepared by dissolving the electrolyte (Li salt) and the second compound and, if necessary, additional additives in a non-aqueous solvent. Here, the input amount P2 of the second compound in preparing the non-aqueous electrolyte is smaller than the input amount P1 of the first compound. Also, input amount P2 are, PF ₂ in the non-aqueous electrolyte battery is completed (= O) O - containing ₂ and a second group selected from the group consisting of ^{^{-, PF (= O) (}} O) The ratio C2 is adjusted to be 0.1% by mass or more and 1.5% by mass or less.

Next, the non-aqueous electrolyte is introduced into the exterior member containing the electrode group. Finally, the non-aqueous electrolyte is obtained by sealing the exterior member.

Although the example in which the first compound is added to the positive electrode mixture has been described above, the method of including the first group in the positive electrode material layer is not limited to this method. For example, after preparing a slurry for producing a positive electrode, the slurry for producing a positive electrode may contain a powder of the first compound or a solution thereof.

Alternatively, after a positive electrode mixture layer is formed on a positive electrode current collector using a slurry for producing a positive electrode, a solution containing a first compound having a first group is coated on the surface of the positive electrode mixture layer, and then coated. By drying the film, a positive electrode material layer containing the first group can be obtained. In this example, if necessary, it is preferable to subject the coating to heating before subjecting to drying. The heating can be performed, for example, at a temperature of 60 ° C. to 150 ° C. for 1 minute to 60 minutes. By this heating, the first compound can be fixed inside the pores of the positive electrode mixture layer. Note that part of the first compound may be denatured by this heating.

Alternatively, the positive electrode mixture layer is formed on the positive electrode current collector, and then the positive electrode mixture layer is impregnated with a solution of the first compound having a first group, and then the positive electrode mixture layer is dried. You may obtain the positive electrode material layer containing 1st group. Also in this example, it is preferable to subject it to heating before subjecting the positive electrode mixture layer to drying as required. The heating can be performed, for example, at a temperature of 50 ° C. to 80 ° C. for 1 minute to 120 minutes. This heating may be performed, for example, by impregnating the positive electrode mixture layer in the pressure reducing device with the first compound, bringing the pressure reducing device to a temperature within the above range, and maintaining the state for the above time. . The first compound can be fixed to the inside of the pores of the positive electrode mixture layer. Note that part of the first compound may be denatured by this heating.

Alternatively, by using the positive electrode prepared slurry powder impregnated with the LiPF ₆ to form a positive-electrode mixture layer, then it is also possible to synthesize a compound having a first base in the positive electrode composite material layer. For example, water is contained in the positive electrode mixture layer, and the positive electrode mixture layer is heated in this state, whereby a positive electrode material layer containing a first group can be obtained. In this method, for example, the first additive in the positive electrode material layer is controlled by combining the additive amount of LiPF _{6 in} preparation of the slurry for preparing the positive electrode, the additive amount of water to the positive electrode mixture layer, the heating temperature and the heating time The content ratio C1 of the groups of

The content ratio C1 and the content ratio C2 may change, for example, due to the transfer of a part of the first group to the non-aqueous electrolyte, and the charge and discharge of the non-aqueous electrolyte battery. However, for example, in the battery produced by the procedure described in the following example, the content ratio C1 of the first group in the positive electrode material layer can be maintained in the range of 0.3% by mass or more and 2% by mass or less The content ratio C2 of the second group in the non-aqueous electrolyte can be maintained in the range of 0.1% by mass or more and 1.5% by mass or less.

<Various analysis methods>
(Quantification of content ratio C1 and content ratio C2)
The content ratio C1 (mass%) of the first group in the positive electrode material layer and the content ratio C2 (mass%) of the second group in the non-aqueous electrolyte can be quantified, for example, by the following method.

First, a non-aqueous electrolyte battery to be tested is prepared. The target non-aqueous electrolyte battery is a battery having a capacity of 80% or more of the rated capacity. The capacity retention rate of the battery is determined by the following method. First, the battery is charged to the operating upper limit voltage. The current value at this time is a current value corresponding to the 1 C rate obtained from the rated capacity. Hold the voltage for 3 hours after reaching the operating upper limit voltage. After charging and holding voltage, discharge to the lower limit of the operating voltage at a rate of 0.2 C and measure the discharge capacity. The ratio of the obtained capacity to the rated capacity is defined as a capacity maintenance rate. After measurement of capacity retention rate, the battery is kept discharged.

Next, the battery is disassembled in an inert gas atmosphere. Next, a part of the positive electrode and a part of the non-aqueous electrolyte are collected from the disassembled battery. For example, in a glove box under an argon gas atmosphere, the battery is disassembled, the non-aqueous electrolyte is removed from the disassembled battery, and the positive electrode in the electrode group is cut off.

The excised positive electrode is then washed with solvent. As the solvent, linear carbonates (eg, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate etc.) and acetonitrile can be used. After washing, the positive electrode is dried under vacuum while maintaining an inert gas atmosphere. Drying of the positive electrode can be performed, for example, under a vacuum of 50 ° C. for 10 hours.

Next, part of the positive electrode material layer is peeled off from the dried positive electrode. At this time, the positive electrode material layer is peeled off from the positive electrode current collector so that the surface of the positive electrode current collector is exposed. Next, the mass of the peeled positive electrode material layer is measured.

Subsequently, the peeled positive electrode material layer is immersed in heavy water to extract the components contained in the positive electrode material layer. Next, this extract is introduced into an NMR apparatus as a measurement sample, and 19 F-NMR and 31 P-NMR measurements are performed. From the ratio of the peak of the measurement result to that of the standard substance, it is possible to quantify each component contained in the measurement sample. By performing 19F-NMR and 31P-NMR measurements in this way, it is composed of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ contained in the measurement sample, and a combination thereof The mass of the group selected from the group can be measured. By dividing the measured mass by the mass of the measurement sample, the content ratio C1 [mass%] of the first group in the positive electrode material layer can be calculated.

The content ratio C2 can be calculated by the following procedure. First, a part of the non-aqueous electrolyte is extracted as a measurement sample from the non-aqueous electrolyte disassembled as described above, and weighed. The sample is subjected to 19 F-NMR and 31 P-NMR. From the measurement results obtained, the mass of a group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof contained in the measurement sample is measured be able to. By dividing the measured mass by the weight value of the measurement sample, the content ratio C2 [mass%] of the second group in the non-aqueous electrolyte can be calculated.

(Method of identifying components contained in non-aqueous electrolyte)
The identification method of the component of the solvent contained in a non-aqueous electrolyte is demonstrated below.
First, the nonaqueous electrolyte battery to be measured is discharged at 1 C until the battery voltage becomes 1.0V. The discharged non-aqueous electrolyte battery is disassembled in an inert atmosphere glove box.

Then, the non-aqueous electrolyte contained in the battery and the electrode group is extracted. When the non-aqueous electrolyte can be taken out from the location where the non-aqueous electrolyte battery is opened, the non-aqueous electrolyte is sampled as it is. On the other hand, in the case of being held by the electrode group, the electrode group is further disassembled and, for example, the separator impregnated with the non-aqueous electrolyte is taken out. The non-aqueous electrolyte impregnated in the separator can be extracted using, for example, a centrifuge or the like. Thus, non-aqueous electrolyte sampling can be performed. When the amount of the non-aqueous electrolyte contained in the non-aqueous electrolyte battery is small, the non-aqueous electrolyte can also be extracted by immersing the electrode and the separator in an acetonitrile liquid. The mass of the acetonitrile solution can be measured before and after extraction to calculate the amount of extraction.

The sample of the non-aqueous electrolyte thus obtained is subjected to, for example, gas chromatography mass spectrometry (GC-MS) or nuclear magnetic resonance spectroscopy (NMR) to conduct compositional analysis. Thus, it can be determined whether lithium hexafluorophosphate is contained in the non-aqueous electrolyte.

Moreover, according to this method, lithium hexafluorophosphate can also be quantified. In the determination, first, a calibration curve of lithium hexafluorophosphate is prepared. The amount of lithium hexafluorophosphate in the non-aqueous electrolyte can be calculated by comparing the prepared calibration curve with the peak intensity or area in the result obtained by measuring the non-aqueous electrolyte sample. .

(Method of identifying positive electrode active material and negative electrode active material)
The positive electrode active material contained in the non-aqueous electrolyte battery can be identified according to the following method.
First, the non-aqueous electrolyte battery is discharged at 1 C until the battery voltage becomes 1.0V. Next, the battery in such a state is disassembled in an argon-filled glove box. Take out the positive electrode from the disassembled battery. The removed positive electrode is washed with an appropriate solvent. For example, ethyl methyl carbonate is preferably used. If the washing is insufficient, an impurity phase such as lithium carbonate or lithium fluoride may be mixed due to the influence of lithium ions remaining in the positive electrode. In that case, it is advisable to use an airtight container in which the measurement can be performed in an inert gas atmosphere. After washing, the positive electrode is subjected to vacuum drying. After drying, the positive electrode material layer is peeled off from the current collector using a spatula or the like to obtain a powdery positive electrode material layer.

The powder structure of the compound contained in this powder can be identified by conducting powder X-ray diffraction measurement (XRD) on the powder thus obtained. The measurement is performed using a CuKα ray as a radiation source in a measurement range of 2θ of 10 to 90 °. By this measurement, an X-ray diffraction pattern of a compound contained in the powder can be obtained. As an apparatus for powder X-ray diffraction measurement, for example, SmartLab manufactured by Rigaku Corporation is used. The measurement conditions are as follows: Cu target; 45 kV 200 mA; solar slit: 5 ° both for incidence and light reception; step width: 0.02 deg; scan rate: 20 deg / min; semiconductor detector: D / teX Ultra 250; Plate holder: Flat glass sample plate holder (thickness 0.5 mm); Measurement range: 10 ° ≦ 2θ ≦ 90 °. When other devices are used, measurement is performed using standard Si powder for powder X-ray diffraction so that the measurement results equivalent to the above can be obtained, under the conditions that the peak intensity and peak top position coincide with the above device Do.

In the measurement results, the mixed state of the active material can be determined by whether or not peaks attributed to a plurality of crystal structures appear.

Subsequently, the positive electrode material layer is observed by a scanning electron microscope (SEM). Also for sample sampling, do not touch the air, and perform in an inert atmosphere such as argon or nitrogen.

Several particles in the form of primary particles or secondary particles identified in the field of view are selected in a 3000 × SEM observation image. At this time, the particle size distribution of the selected particles is selected as wide as possible. For the active material particles that can be observed, the type and composition of the constituent elements of the active material are specified by energy dispersive X-ray spectroscopy (EDX). This makes it possible to specify the type and amount of elements other than Li among the elements contained in each of the selected particles. The same operation is performed on each of the plurality of active material particles to determine the mixed state of the active material particles.

Subsequently, the positive electrode material layer is weighed. The weighed powder is dissolved in hydrochloric acid and diluted with ion exchange water, and then the content of metal is calculated by inductively coupled plasma atomic emission spectroscopy (ICP-AES). When multiple types of active materials exist, the mass ratio is estimated from the content ratio of elements unique to each active material. The ratio of the specific element to the mass of the active material is determined from the composition of the constituent element obtained by energy dispersive X-ray spectroscopy.

Thus, the active material contained in the positive electrode of the non-aqueous electrolyte battery can be identified.

The negative electrode active material contained in the non-aqueous electrolyte battery can also be identified by the same procedure as described above. However, here, in order to grasp the crystalline state of the negative electrode active material, lithium ions are separated from the active material to be measured. For example, the non-aqueous electrolyte battery is discharged at 1 C until the battery voltage is 1.0V. However, even when the battery is discharged, lithium ions remaining in the active material may be present.

(Method of measuring working potential of active material)
First, the battery is placed in an inert gas atmosphere such as, for example, in a glove box under an argon gas atmosphere, in order to prevent the battery components from reacting with atmospheric components and moisture during disassembly. Next, open the non-aqueous electrolyte battery in such a glove box. For example, heat seal parts around each of the positive electrode current collection tab and the negative electrode current collection tab can be cut to cut open the non-aqueous electrolyte battery. The electrode group is taken out of the cut-off non-aqueous electrolyte battery. When the electrode group taken out includes the positive electrode lead and the negative electrode lead, the positive electrode lead and the negative electrode lead are cut while being careful not to short the positive and negative electrodes.

Next, the weight of the part which was facing the positive electrode among the negative electrodes taken out from the dismantled electrode group is measured. Thereafter, for example, a 3 cm square negative electrode sample is cut out from the negative electrode. The state of charge of the battery may be any state. The negative electrode sample is cut out from the portion of the negative electrode facing the positive electrode.

Next, the weight of the cut-off negative electrode sample is measured. After the measurement, a negative electrode sample is used as a working electrode, and a bipolar or tripolar electrochemical measurement cell using a lithium metal foil as a counter electrode and a reference electrode is prepared. The prepared electrochemical measurement cell is charged to a lower limit potential of 1.0 V (vs. Li / Li ⁺ ). The current value at this time is obtained by multiplying the ratio of the weight of the cut negative electrode sample to the weight of the portion of the negative electrode contained in the battery facing the positive electrode by the rated capacity of the battery. After charging and voltage holding, discharge is performed until the negative electrode potential reaches 2.0 V (vs. Li / Li ⁺ ) at the same current value as charging. A total of 3 cycles of the above charging and discharging are performed. The average potential in charging in the final third cycle and the average potential in discharging are determined, and the average of the two is taken as the operating potential of the negative electrode.

The nonaqueous electrolyte battery according to the first embodiment will be more specifically described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a non-aqueous electrolyte battery of a first example according to the first embodiment cut in the thickness direction. FIG. 2 is an enlarged cross-sectional view of a portion A of FIG.

The nonaqueous electrolyte battery 10 shown in FIGS. 1 and 2 includes a flat wound electrode group 1. The flat wound electrode group 1 is housed in a bag-like exterior member 2 made of a laminate film including a metal layer and two resin films sandwiching the metal layer.

The flat wound electrode group 1 is formed by spirally winding and pressing a laminate obtained by stacking the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 in this order from the outside. The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode material layer 3b formed on the negative electrode current collector 3a. In the portion located in the outermost layer of the negative electrode 3, as shown in FIG. 2, the negative electrode material layer 3b is formed on one surface of the inner surface side of the negative electrode current collector 3a. In the other part of the negative electrode 3, the negative electrode material layer 3 b is formed on both surfaces of the negative electrode current collector 3 a. The positive electrode 5 includes a positive electrode current collector 5a and a positive electrode material layer 5b formed on both surfaces of the positive electrode current collector 5a.

As shown in FIG. 1, the negative electrode terminal 6 is connected to the negative electrode current collector 3 a of the negative electrode 3 near the outer peripheral end of the wound electrode group 1, and the positive electrode terminal 7 is connected to the positive electrode current collector 5 a of the positive electrode 5. It is done. The negative electrode terminal 6 and the positive electrode terminal 7 are extended from one end of the bag-like exterior member 2 to the outside.

The nonaqueous electrolyte battery 10 shown in FIG. 1 and FIG. 2 further includes a nonaqueous electrolyte not shown. The non-aqueous electrolyte is accommodated in the exterior member 2 in a state of being held by the electrode group 1, for example, the negative electrode material layer 3 b, the positive electrode material layer 5 b, and the separator 4.

The non-aqueous electrolyte can be injected, for example, from the opening of the bag-like exterior member 2. After injecting the non-aqueous electrolyte, the opening of the bag-like exterior member 2 is heat-sealed with the negative electrode terminal 6 and the positive electrode terminal 7 interposed therebetween, whereby the wound electrode group 1 and the non-aqueous electrolyte can be completely sealed.

The nonaqueous electrolyte battery according to the first embodiment is not limited to the configuration shown in FIG. 1 and FIG. 2 described above, and can be configured as shown in FIG. 3 and FIG. 4, for example.

FIG. 3 is a partially cutaway perspective view of a non-aqueous electrolyte battery of a second example according to the first embodiment. FIG. 4 is an enlarged cross-sectional view of a portion B of FIG.

The non-aqueous electrolyte battery 10 of the example shown in FIGS. 3 and 4 includes a stacked electrode group 11. The laminated electrode group 11 is accommodated in an exterior member 12 formed of a laminate film including a metal layer and two resin films sandwiching the metal layer.

As shown in FIG. 4, the stacked electrode group 11 has a structure in which the positive electrode 13 and the negative electrode 14 are alternately stacked with the separator 15 interposed therebetween. A plurality of positive electrodes 13 exist, each including a current collector 13a and a positive electrode material layer 13b supported on both sides of the current collector 13a. A plurality of negative electrodes 14 exist, each including a current collector 14a and a negative electrode material layer 14b supported on both sides of the current collector 14a. A portion 14 c of the current collector 14 a of each negative electrode 14 protrudes from one end of the positive electrode 13. A portion 14 c of the current collector 14 a is electrically connected to the strip-like negative electrode terminal 16. The tip end of the strip-like negative electrode terminal 16 is pulled out from the exterior member 12 as shown in FIG. Although not shown, a portion of the current collector 13a of the positive electrode 13 opposite to the portion 14c of the current collector 14a protrudes from one end of the negative electrode 14. A portion of the current collector 13 a that protrudes from the negative electrode 14 is electrically connected to the strip-like positive electrode terminal 17. The end of the strip-like positive electrode terminal 17 is located on the opposite side to the negative electrode terminal 16 as shown in FIG. 3 and is drawn out from the side of the exterior member 12.

Examples of the shape of the battery include flat type, square type, cylindrical type, coin type, button type, sheet type and laminated type. Of course, in addition to the small battery loaded on the portable electronic device etc., a large battery loaded on a two- or four-wheeled automobile etc. may be used.

The non-aqueous electrolyte battery according to the first embodiment includes a positive electrode including a positive electrode material layer, a negative electrode, and a non-aqueous electrolyte. The positive electrode material layer includes a positive electrode active material and a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The non-aqueous electrolyte comprises lithium hexafluorophosphate and a _second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof . The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less. The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less, and is smaller than the content ratio C1. In a non-aqueous electrolyte battery satisfying such content ratios C1 and C2, the supply of Li ions to the vicinity of the reaction site of the positive electrode can be promoted, the positive electrode reaction can be promoted, and the decomposition of lithium hexafluorophosphate is prevented. Can. As a result, the non-aqueous electrolyte battery according to the first embodiment can exhibit excellent output performance under a low temperature environment.

Second Embodiment
According to a second embodiment, a battery pack is provided. The battery pack includes the non-aqueous electrolyte battery according to the first embodiment.

The battery pack according to the second embodiment can also include a plurality of non-aqueous electrolyte batteries. The plurality of non-aqueous electrolyte batteries can be electrically connected in series or electrically connected in parallel. Alternatively, a plurality of nonaqueous electrolyte batteries can be electrically connected in a combination of series and parallel. The electrically connected non-aqueous electrolyte battery can constitute an assembled battery. That is, the battery pack according to the second embodiment can also include an assembled battery.

The battery pack according to the second embodiment can include a plurality of battery packs. A plurality of battery packs can be connected in series, in parallel, or in combination of series and parallel.

An example of the battery pack of the second embodiment will be described with reference to the drawings.

FIG. 5 is an exploded perspective view of an example battery pack according to the second embodiment. FIG. 6 is a block diagram showing an electric circuit of the battery pack shown in FIG. For the unit cell, for example, the flat battery shown in FIGS. 1 and 2 can be used.

The plurality of unit cells 21 configured from the flat type non-aqueous electrolyte battery shown in FIG. 1 and FIG. 2 described above are laminated so that the negative electrode terminal 6 and the positive electrode terminal 7 extended to the outside are aligned in the same direction, The battery pack 23 is configured by fastening the tape 22. These single cells 21 are electrically connected in series to each other as shown in FIG.

The printed wiring board 24 is disposed to face the side surface of the unit cell 21 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. As shown in FIG. 6, a thermistor 25, a protection circuit 26, and a terminal 27 for energization to an external device are mounted on the printed wiring board 24. An insulating plate (not shown) is attached to the surface of the printed wiring board 24 facing the battery assembly 23 in order to avoid unnecessary connection with the wiring of the battery assembly 23.

The positive electrode side lead 28 is connected to the positive electrode terminal 7 of the unit cell 21 located in the lowermost layer of the assembled battery 23, and the tip thereof is inserted into the positive electrode side connector 29 of the printed wiring board 24 and is electrically connected. The negative electrode side lead 30 is connected to the negative electrode terminal 6 of the unit cell 21 positioned in the uppermost layer of the assembled battery 23, and the tip thereof is inserted into the negative electrode side connector 31 of the printed wiring board 24 and is electrically connected. These

connectors

29 and 31 are connected to the protective circuit 26 through the

wirings

32 and 33 formed on the printed wiring board 24.

The thermistor 25 detects the temperature of the unit cell 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the plus side wire 34 a and the minus side wire 34 b between the protection circuit 26 and the current-carrying terminal 27 to the external device under a predetermined condition. The predetermined condition is, for example, when the detected temperature of the thermistor 25 becomes equal to or higher than a predetermined temperature. Further, the predetermined condition is, for example, when overcharge, overdischarge, overcurrent, or the like of the single battery 21 is detected. The detection of the overcharge and the like is performed on the individual single cells 21 or the entire assembled battery 23. When detecting each single battery 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single battery 21. In the case of the battery pack 20 shown in FIG. 5 and FIG. 6, a wire 35 for voltage detection is connected to each of the single cells 21. Detection signals relating to respective voltages of the cells 21 are transmitted to the protection circuit 26 through the wires 35.

Protective sheets 36 made of rubber or resin are respectively disposed on the three side surfaces of the assembled battery 23 except the side surfaces from which the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

The battery assembly 23 is stored in the storage container 37 together with the protective sheets 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on both the inner side in the long side direction of the storage container 37 and the inner side in the short side direction, and the printed wiring board 24 is disposed on the inner side opposite to the short side. The battery assembly 23 is located in a space surrounded by four sides by the protective sheet 36 and the printed wiring board 24. The lid 38 is attached to the upper surface of the storage container 37.

A heat shrink tape may be used in place of the adhesive tape 22 for fixing the battery assembly 23. Fixing of the assembled battery in this case can be performed, for example, by the following procedure. First, protective sheets are disposed on both side surfaces of the battery pack 23. Next, the assembled battery 23 is wound with a heat shrink tape from above the protective sheet. The assembled battery 23 can be bound by thermally shrinking the wound heat shrinkable tape.

Although the form which connected the cell 21 in series was shown in FIG.5 and FIG.6, in order to increase battery capacity, you may connect in parallel. The assembled battery packs can also be connected in series or in parallel.

In addition, the aspect of the battery pack is appropriately changed depending on the application. As a use of a battery pack, what the cycle characteristic in a large current characteristic is desired is preferred. Specifically, for example, a two-wheel or four-wheel hybrid electric vehicle, a two- or four-wheel electric vehicle, an on-vehicle such as an assist bicycle, a train, etc. may be mentioned. In particular, automotive applications are preferred.

The battery pack according to the second embodiment includes the non-aqueous electrolyte battery according to the first embodiment, and thus can exhibit excellent output performance under a low temperature environment.

[Example]
EXAMPLES Examples are described below, but the present invention is not limited to the examples listed below, as long as the gist of the present invention is not exceeded.

Example 1
In Example 1, a non-aqueous electrolyte battery was manufactured by the following procedure.

<Fabrication of negative electrode>
As a negative electrode active material, a powder of lithium titanium complex oxide (Li ₄ Ti ₅ O ₁₂ : LTO) having a spinel structure capable of absorbing and releasing lithium at an operating potential of 1.55 V (vs. Li / Li ⁺ ) is used It was. A negative electrode mixture containing 90 parts by mass of this negative electrode active material, 5 parts by mass of carbon black as a conductive agent, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder Prepared. This negative electrode mixture was added to N-methylpyrrolidone (NMP) to prepare a slurry for producing a negative electrode. The slurry for negative electrode preparation thus prepared was applied to both sides of an aluminum foil (negative electrode current collector) having a thickness of 20 μm. Under the present circumstances, the part in which the slurry for negative electrode preparation was not apply | coated on the surface remained on the negative electrode collector. The coatings were then dried and then subjected to pressing. Thus, a negative electrode including the negative electrode current collector and the negative electrode material layer formed on the negative electrode current collector was obtained.

<Fabrication of positive electrode>
A powder of lithium cobalt composite oxide (LiCoO ₂ : LCO) was used as a positive electrode active material. A positive electrode mixture containing 90 parts by mass of this positive electrode active material, 5 parts by mass of carbon black as a conductive agent, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder. Prepared. Furthermore, a powder of lithium monofluorophosphate (PF (= O) (OLi) ₂ ) as a first compound was mixed with this positive electrode mixture so that the compounding ratio P1 was 1.1% by mass. Next, this positive electrode mixture was added to NMP to prepare a slurry for producing a positive electrode.

This positive electrode preparation slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 20 μm. Under the present circumstances, the part in which the slurry for positive electrode preparation was not apply | coated on the surface remained on the positive electrode collector. The coating was then dried and then subjected to pressing. Thus, a positive electrode including the positive electrode current collector and the positive electrode material layer formed on the positive electrode current collector was obtained.

<Preparation of electrode group>
A laminate obtained by laminating, in this order, the positive electrode manufactured as described above, a separator made of a polyethylene porous film having a thickness of 20 μm, the negative electrode manufactured as described above, and another separator I got By heat-pressing this at 50 ° C., a flat electrode group having a width of 58 mm, a height of 95 mm and a thickness of 3.0 mm was produced. Next, an exterior member made of a laminate film constituted of an aluminum foil and a polypropylene layer formed on both sides thereof was prepared. The electrode group obtained as described above was accommodated in the exterior member.

<Preparation of Nonaqueous Electrolyte>
Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed in a volume ratio of 2: 3 to prepare a mixed solvent.

In this mixed solvent, lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a concentration of 1.0 mol / L as an electrolyte. In addition, a powder of lithium monofluorophosphate (PF (= O) (OLi) ₂ ) as the second compound in a mixed solvent so that the blending ratio P2 with respect to the mass of the non-aqueous electrolyte is 0.5 mass% Mix and dissolve. Thus, a non-aqueous electrolyte was prepared.

Injection of non-aqueous electrolyte
10 g of the non-aqueous electrolyte prepared as described above was injected into the exterior member containing the electrode group, and then the exterior member was sealed. Thus, a non-aqueous electrolyte battery was produced.

<First charge and recharge>
First, the non-aqueous electrolyte battery was charged at a rate of 0.2 C to a battery voltage of 2.9 V in a 25 ° C. environment. Subsequently, the battery was left for 3 hours while keeping the voltage of the non-aqueous electrolyte battery at 2.9 V as it was. The charging rate of the non-aqueous electrolyte battery in this state was 100%, ie, fully charged. Thereafter, the non-aqueous electrolyte battery was discharged at a 0.2 C rate until the battery voltage was 1.2 V. Next, this non-aqueous electrolyte battery was charged at a 0.2 C rate so as to have a charge rate of 50%. Thus, the non-aqueous electrolyte battery was completed.

<Measurement of initial discharge capacity>
Subsequently, the completed non-aqueous electrolyte battery was subjected to one charge and discharge cycle at a 0.2 C rate in a 25 ° C. environment. The charge termination voltage was 2.9V. The discharge end voltage was 1.2 V. A 30 minute rest was performed between charge and discharge under a 25 ° C. environment. The discharge capacity at the time of discharge here was measured, and it was set as the first time discharge capacity. Thereafter, the non-aqueous electrolyte battery was charged at a rate of 1 C to adjust the charging rate to 50%.

<Low temperature performance test>
Subsequently, the non-aqueous electrolyte battery was charged in a 25 ° C. environment at a 0.2 C rate until the battery voltage was 2.9 V. Subsequently, the non-aqueous electrolyte battery was left to stand for 3 hours while keeping the voltage of the non-aqueous electrolyte battery at 2.9 V as it was. Thereafter, the non-aqueous electrolyte battery was discharged at a 1 C rate until the battery voltage was 1.2 V in a 25 ° C. environment. The discharge capacity during this discharge was recorded as a 25 ° C. 1 C discharge capacity.

Subsequently, the non-aqueous electrolyte battery was charged in a 25 ° C. environment at a 0.2 C rate until the battery voltage was 2.9 V. Subsequently, the non-aqueous electrolyte battery was left to stand for 3 hours while keeping the voltage of the non-aqueous electrolyte battery at 2.9 V as it was. Thereafter, the non-aqueous electrolyte battery was left in an environment of −20 ° C. for 3 hours. Thereafter, the non-aqueous electrolyte battery was discharged at a 1 C rate until the battery voltage was 1.2 V in a -20 ° C. environment. The discharge capacity during this discharge was recorded as −20 ° C. 1 C discharge capacity.

The percentage (%) of -20 ° C. 1 C discharge capacity to 25 ° C. 1 C discharge capacity was taken as the low temperature performance index of this non-aqueous electrolyte. The low temperature performance index indicates that the higher the value, the higher the output performance in a low temperature environment.

(Examples 2 to 5 and Comparative Examples 1 to 5)
In Examples 2 to 5 and Comparative Examples 1 to 5, the mixing ratio P1 of the first compound added to the positive electrode mixture and / or the mixing ratio P2 of the second compound added to the non-aqueous electrolyte are shown in Table 1 below. Each non-aqueous electrolyte battery was produced by the same procedure as Example 1 except having changed it from that of Example 1 as shown to.

(Example 6)
According to the same procedure as in Example 1, except that a powder of lithium nickel cobalt manganese composite oxide (LiNi _0.33 Co _0.33 Mn _0.33 O ₂ : NCM) was used instead of lithium cobalt composite oxide as the positive electrode active material. A non-aqueous electrolyte battery was produced.

The positive electrode active material, the conductive agent, and the binder were mixed in a ratio of 90 parts by weight, 5 parts by weight, and 5 parts by weight, respectively, as in Example 1, to prepare a positive electrode mixture. The mixing ratio P1 of the lithium monofluorophosphate powder as the first compound to the positive electrode mixture was also 1.1 mass% with respect to the mass of the positive electrode mixture, as in Example 1.

(Example 7)
A non-aqueous electrolyte battery was manufactured in the same manner as in Example 1, except that lithium manganese composite oxide (LiMn ₂ O ₄ : LMO) powder was used instead of lithium cobalt composite oxide as the positive electrode active material. did.

(Example 8)
The same as Example 1, except that a powder of niobium titanium composite oxide (TiNb ₂ O ₇ : NTO) having a monoclinic crystal structure was used as the negative electrode active material instead of the lithium titanium composite oxide powder. A non-aqueous electrolyte battery was produced by the following procedure. The working potential of this niobium titanium composite oxide is in the range of 0.8 V (vs. Li ^/ Li ⁺ ) to 2.0 V (vs. Li ^/ Li ⁺ ).

(Example 9)
As a negative electrode active material, a powder of Na-containing niobium titanium composite oxide (Li ₂ Na _1.7 Ti _5.7 Nb _0.3 O ₁₄ : LNT) having a orthorhombic crystal structure was used instead of the lithium titanium composite oxide powder. A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except for the above. The working potential of this Na-containing niobium titanium composite oxide is in the range of 0.8 V (vs. Li ^/ Li ⁺ ) to 2.0 V (vs. Li ^/ Li ⁺ ).

(Example 10)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte prepared in the following procedure was used.

A mixed solvent was prepared by mixing ethylene carbonate (EC) and methyl ethyl carbonate solvent (EMC) in a volume ratio of 2: 3.

In this mixed solvent, lithium hexafluorophosphate (LiPF ₆ ) is dissolved as an electrolyte at a concentration of 0.5 mol / L, and lithium tetrafluoroborate (LiBF ₄ ) is dissolved at a concentration of 0.5 mol / L. I did. In addition, a powder of lithium monofluorophosphate (PF (= O) (OLi) ₂ ) as the second compound in a mixed solvent so that the blending ratio P2 with respect to the mass of the non-aqueous electrolyte is 0.5 mass% Mix and dissolve. Thus, a non-aqueous electrolyte was prepared.

(Example 11)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the positive electrode produced in the following procedure was used.

First, a powder of lithium cobalt composite oxide (LiCoO ₂ : LCO) was used as a positive electrode active material. A positive electrode mixture containing 90 parts by mass of this positive electrode active material, 5 parts by mass of carbon black as a conductive agent, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder. Prepared. Next, this positive electrode mixture was added to NMP to prepare a slurry for producing a positive electrode.

This positive electrode preparation slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 20 μm. Under the present circumstances, the part in which the slurry for positive electrode preparation was not apply | coated on the surface remained on the positive electrode collector. The coating was then dried and then subjected to pressing. Thus, a positive electrode intermediate having the positive electrode current collector and the positive electrode mixture layer formed on the positive electrode current collector was obtained.

Next, in an inert atmosphere, ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed at a volume ratio of 2: 3 to prepare a mixed solvent. In this mixed solvent, lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte at a concentration of 3.2 mol / L. Furthermore, pure water was added to this mixed solution so as to be 1% by mass to obtain a treatment solution.

The positive electrode intermediate prepared above was immersed in the treatment solution thus prepared. Next, the container containing the solution in which the positive electrode intermediate was immersed was placed in a vacuum device, and the pressure therein was reduced. Thus, the inside of the positive electrode mixture layer was impregnated with the treatment solution. The container was then sealed and left at 60 ° C. for 1 hour. The positive electrode intermediate was then removed from the vessel, washed with methyl ethyl carbonate solvent and subjected to vacuum drying. Thus, a positive electrode was produced.

(Example 12)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the positive electrode produced in the following procedure was used.

First, in the same manner as in Example 11, a positive electrode intermediate was produced. Next, in an inert atmosphere, ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed at a volume ratio of 2: 3 to prepare a mixed solvent. Lithium hexafluorophosphate (LiPF ₆ ) was dissolved in this mixed solvent as an electrolyte at a concentration of 0.5 mol / L. Furthermore, lithium difluorophosphate (PF ₂ (= O) (OLi)) was added to this solution. Thus, the treatment solution was prepared. Lithium difluorophosphate was introduced in an amount of 2.0% by weight with respect to the weight of the treatment solution.

The positive electrode intermediate prepared above was immersed in this treatment solution. Then, the container containing the solution in which the positive electrode intermediate was immersed was placed in a pressure reducing device, and the pressure therein was reduced. Thus, the inside of the positive electrode mixture layer was impregnated with the treatment solution. The container was then sealed and left at 60 ° C. for 1 hour. The positive electrode intermediate was then removed, washed with methyl ethyl carbonate solvent and subjected to vacuum drying. Thus, a positive electrode was produced.

(Comparative example 6)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte prepared in the following procedure was used.

In this mixed solvent, lithium tetrafluoroborate (LiBF ₄ ) was dissolved as an electrolyte at a concentration of 1.0 mol / L. In addition, a powder of lithium monofluorophosphate (PF (= O) (OLi) ₂ ) as the second compound in a mixed solvent so that the blending ratio P2 with respect to the mass of the non-aqueous electrolyte is 0.5 mass% Mix and dissolve. Thus, a non-aqueous electrolyte was prepared.

(Comparative example 7)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except for the following points.

First, during the preparation of the positive electrode, lithium monofluorophosphate powder was not mixed in the positive electrode mixture. That is, the mixture ratio P1 was set to 0 mass%.

Moreover, in the case of negative electrode preparation, the powder of lithium monofluorophosphate was mixed with the negative electrode mixture so that the compounding ratio with respect to the mass of the negative electrode mixture was 2.0 mass%.

Further, in the preparation of the non-aqueous electrolyte, lithium monofluorophosphate was added to the mixed solvent so that the blending ratio P2 with respect to the mass of the non-aqueous electrolyte was 0.7 mass%.

(Comparative example 8)
The lithium monofluorophosphate powder was not mixed with the positive electrode mixture in the preparation of the positive electrode, and in preparing the non-aqueous electrolyte, the blending ratio P2 with respect to the mass of the non-aqueous electrolyte was 0.7 mass%. A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that lithium monofluorophosphate was mixed in the mixed solvent.

(Comparative example 9)
In Comparative Example 9, a non-aqueous electrolyte battery was produced in the same manner as in Comparative Example 8, except that the blend ratio P2 of the second compound to the non-aqueous electrolyte was changed to 1.7% by mass.

Table 2 below shows the coated amounts of the positive electrode preparation slurry and negative electrode preparation slurry per one side of the current collector in the production of the non-aqueous electrolyte batteries of Examples 1 to 12 and Comparative Examples 1 to 9 [g / g m ² ] and the density [g / cm ³ ] of the positive electrode material layer and the negative electrode material layer after pressing are collectively shown.

[Evaluation]
The non-aqueous electrolyte batteries of Examples 2 to 12 and Comparative Examples 1 to 9 were tested in the same procedure as the non-aqueous electrolyte battery of Example 1. Moreover, regarding the nonaqueous electrolyte batteries of Examples 1 to 12 and Comparative Examples 1 to 9, a group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) ₂ and combinations thereof in the positive electrode material layer PF ₂ in more content C1 and a non-aqueous electrolyte of a first group selected ^{(= O) O -, PF} (= O) (O -) second selected from ₂ and a combination thereof The content ratio C2 of the groups was quantified by the procedure described above. As a result of the analysis, it was found that the positive electrode material layer of the positive electrode of the non-aqueous electrolyte battery of Example 11 contained a compound having a group PF (= O) (O ⁻ ) ₂ . Further, as a result of analysis, it was found that the positive electrode material layer of the positive electrode of the non-aqueous electrolyte battery of Example 11 contains a compound having a group PF ₂ (= O) (O ⁻ ).

Regarding the content ratios C1 and C2, the relationship between C1 and C2, the composition of the positive electrode active material, the composition of the negative electrode active material, the type of electrolyte used, and the low temperature performance index for the non-aqueous electrolyte batteries of each Example and Comparative Example, The results are summarized in Table 3 below.

(Examples 13 to 16 and Comparative Examples 10 and 11)
In Examples 13 to 16 and Comparative Examples 10 and 11, the first compound and / or the second compound are changed to those described in Table 4 below, and the first compound and the second compound are shown in Table 4 below. A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except for adding the amounts described in the blending ratios P1 and P2 described.

Table 5 below shows coating amounts of the positive electrode production slurry and the negative electrode production slurry per one side of the current collector in the production of the nonaqueous electrolyte batteries of Examples 13 to 16 and Comparative Examples 10 and 11 [g / g m ² ] and the density [g / cm ³ ] of the positive electrode material layer and the negative electrode material layer after pressing are collectively shown.

[Evaluation]
The nonaqueous electrolyte batteries of Examples 13 to 16 and Comparative Examples 10 and 11 were tested in the same procedure as the nonaqueous electrolyte battery of Example 1. Further, the content ratio C1 and the content ratio C2 of the non-aqueous electrolyte batteries of Examples 13 to 16 and Comparative Examples 10 and 11 were quantified by the procedure described above.

The relationship between the content ratios C1 and C2, C1 and C2, and the low temperature performance index for the non-aqueous electrolyte batteries of Examples and Comparative Examples are summarized in Tables 4 and 6 below.

[result]
As apparent from the results in the table, the batteries of Examples 1 to 16 had a large low temperature performance index, ie, a large ratio of −20 ° C. 1 C discharge capacity to 25 ° C. 1 C discharge capacity. That is, it can be seen that the batteries of Examples 1 to 16 were able to exhibit excellent output performance under a low temperature environment. On the other hand, Comparative Example 1 in which the content ratio C1 of the first group in the positive electrode material layer exceeds 2% by mass, Comparative Example 2 in which the content ratio C1 is less than 0.3% by mass, and In each of Comparative Example 3 in which the content ratio C2 of the group exceeds 1.5% by mass, Comparative Example 4 in which the content ratio C2 is less than 0.1% by mass, and Comparative Example 5 in which the content ratio C2 is higher than the content ratio C1. The battery had a low temperature performance index and had poor output performance in a low temperature environment.

From the comparison of the results of Example 1, Example 6, and Example 7, even if the positive electrode active material is different, the content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less In a battery in which the content ratio C2 of the second group in the non-aqueous electrolyte is in the range of 0.1% by mass to 1.5% by mass and the content ratio C1 is larger than the content ratio C2 It can be seen that a high low temperature performance index can be shown, and excellent output performance can be shown in a low temperature environment. Similarly, also from the comparison of the results of Example 1, Example 8 and Example 9, even if the negative electrode active material is different, the battery in which the content ratios C1 and C2 satisfy the above conditions has a high low temperature performance index. It can be shown that it was possible to show excellent output performance in a low temperature environment.

In Example 1, only lithium hexafluorophosphate was used as the electrolyte. In Example 10, lithium hexafluorophosphate and lithium tetrafluoroborate were used as the electrolyte. In Comparative Example 6, only lithium tetrafluoroborate was used as the electrolyte. From the comparison of the results of these examples, the decomposition suppression effect of the electrolyte and the dissociation promoting effect of Li ion due to the presence of the first group and the second group are obtained when the non-aqueous electrolyte contains lithium hexafluorophosphate. It turns out that it is effective.

The batteries of Examples 11 and 12 differ from those of Example 1 in the method of adding the first compound to the positive electrode material layer. From the comparison of the results of Example 1 with Examples 11 and 12, regardless of the method of adding the first compound, a battery in which the content ratios C1 and C2 satisfy the above conditions exhibits a high low temperature performance index. It can be seen that it was possible to show excellent output performance in a low temperature environment.

On the other hand, in Comparative Example 7, the first compound was not added to the positive electrode mixture, but was added to the negative electrode mixture. Further, in Comparative Examples 8 and 9, the first compound was not added to the positive electrode mixture. From the results shown in Table 3, in these comparative examples in which the first compound was not added to the positive electrode mixture, it was not possible to produce a battery in which the content ratio C1 of the first group is 0.3% by mass or more I understand that. Therefore, the batteries of Comparative Examples 7 to 9 had a low temperature performance index and a poor output performance under a low temperature environment.

Further, in the non-aqueous electrolyte battery of Comparative Example 9, lithium monofluorophosphate which was not completely dissolved in the non-aqueous solvent of the non-aqueous electrolyte was present. That is, the non-aqueous electrolyte used in Comparative Example 9 was a saturated solution of lithium monofluorophosphate. However, in the positive electrode material layer of the nonaqueous electrolyte battery of Comparative Example 9, a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof Content of less than 0.3% by mass. That is, from the result of Comparative Example 9, the positive electrode material layer is caused to contain a compound having a group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. If not, it is understood that the content ratio C1 of the first group in the positive electrode material layer can not be 0.3 mass% or more even if the non-aqueous electrolyte in a saturated state for such a compound is used. Furthermore, in the non-aqueous electrolyte battery of Comparative Example 9, the content ratio C2 in the non-aqueous electrolyte exceeded 1.5% by mass, so it is considered that the second group was present in excess in the non-aqueous electrolyte. Therefore, in the non-aqueous electrolyte battery of Comparative Example 9, involvement of lithium hexafluorophosphate in the positive electrode reaction is inhibited, and it is considered that the low temperature resistance is increased.

The non-aqueous electrolyte batteries of Examples 12 to 16 are the ones obtained by changing the first compound and / or the second compound from Example 1. However, it can be seen from the results of Examples 1 and 12 to 16 that the nonaqueous electrolyte batteries of Example 1 and Examples 12 to 16 were similarly able to exhibit excellent output performance under a low temperature environment. Further, from the results of Example 12 and Examples 14 to 16, even if the first compound and the second compound are different compounds, the nonaqueous electrolyte batteries of these examples are excellent in a low temperature environment. It can be seen that the output performance was able to be shown.

On the other hand, it is understood from the results of Comparative Examples 10 and 11 that when the content ratio C1 and the content ratio C2 are equal, the output performance in a low temperature environment is poor.

According to one or more embodiments and examples described above, a non-aqueous electrolyte battery is provided. This non-aqueous electrolyte battery comprises a positive electrode including a positive electrode material layer, a negative electrode, and a non-aqueous electrolyte. The positive electrode material layer includes a positive electrode active material and a first group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The non-aqueous electrolyte includes lithium hexafluorophosphate and a _second group selected from the group consisting of PF ₂ (= O) O ⁻ , PF (= O) (O ⁻ ) _2, and a combination thereof. The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less. The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less, and is smaller than the content ratio C1. In a non-aqueous electrolyte battery satisfying such content ratios C1 and C2, the supply of Li ions to the vicinity of the reaction site of the positive electrode can be promoted, the positive electrode reaction can be promoted, and the decomposition of lithium hexafluorophosphate is prevented. Can. As a result, the non-aqueous electrolyte battery can exhibit excellent output performance under a low temperature environment.

While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Claims

A positive electrode including a positive electrode material layer,
A negative electrode,
And at least a non-aqueous electrolyte held in the positive electrode material layer,
The positive electrode material layer includes a positive electrode active material, and a first group selected from the group consisting of PF 2 (OO) O − , PF (OO) (O − ) 2, and a combination thereof.
The non-aqueous electrolyte comprises lithium hexafluorophosphate and a second group selected from the group consisting of PF 2 (= O) O − , PF (= O) (O − ) 2, and a combination thereof Including
The content ratio C1 of the first group in the positive electrode material layer is 0.3% by mass or more and 2% by mass or less,
The content ratio C2 of the second group in the non-aqueous electrolyte is 0.1% by mass or more and 1.5% by mass or less,
The nonaqueous electrolyte battery in which the content ratio C1 is larger than the content ratio C2.
The positive electrode material layer includes a first compound having the first group,
The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte comprises a second compound having the second group.
The nonaqueous electrolyte battery according to claim 2, wherein the first compound is the same as or different from the second compound.
The negative electrode includes a negative electrode material layer,
The non-aqueous electrolyte battery according to any one of claims 1 to 3, wherein the negative electrode material layer contains a negative electrode active material having an operating potential of 0.7 V (vs. Li / Li + ) or more.
A battery pack comprising the non-aqueous electrolyte battery according to any one of claims 1 to 4.