Secondary battery, battery pack, and vehicle

Abstract

To provide a secondary battery, a battery pack, and a vehicle with excellent high current performance, low temperature performance, and high temperature life performance.SOLUTION: A secondary battery according to an embodiment includes a positive electrode 3, a negative electrode 4, and a non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent including a first solvent including at least one selected from the group consisting of ethyl propionate, propyl propionate, and ethyl butyrate, and a second solvent including γ-butyrolactone, and an electrolyte including lithium bisfluorosulfonylimide.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] Non-aqueous electrolyte batteries using lithium metal, lithium alloys, lithium compounds, or carbonaceous materials as the negative electrode are expected to have high energy density, and research and development is being conducted. 2 or LiMn 2 O 4 Lithium ion batteries having a positive electrode containing a carbonaceous material and a negative electrode containing a carbonaceous material that absorbs and releases lithium ions have been widely put to practical use in portable devices.

[0003] On the other hand, when the battery is mounted on a vehicle such as an automobile or train, in order to satisfy the battery performance (e.g., storage performance, cycle performance, high output, etc.) in a high-temperature environment (e.g., 60°C or higher), it is desirable that the constituent materials of the positive and negative electrodes are materials with excellent chemical and electrochemical stability, strength, and corrosion resistance. Furthermore, in order to realize high performance even in cold regions, improvement of the battery performance (e.g., high current performance, long life performance) in a low-temperature environment (e.g., -40°C) is required. On the other hand, as a non-aqueous electrolyte, development of non-volatile, non-flammable electrolyte solutions is being promoted from the viewpoint of improving safety performance, but they have not yet been put into practical use because they are accompanied by a decrease in output characteristics, low-temperature performance, or long life performance.

[0004] The above problems are obstacles to installing lithium-ion batteries in the engine compartment of automobiles as a replacement for lead-acid batteries. To install lithium-ion batteries in automobiles, improvements in high-temperature durability and large-current performance are required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-146306 A Summary of the Invention [Problem to be solved by the invention]

[0006] The object is to provide a secondary battery, a battery pack, and a vehicle that are excellent in large current performance, low temperature performance, and high temperature life performance. [Means for solving the problem]

[0007] According to an embodiment, a secondary battery is provided that includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent including a first solvent including at least one selected from the group consisting of ethyl propionate, propyl propionate, and ethyl butyrate, and a second solvent including γ-butyrolactone, and an electrolyte including lithium bisfluorosulfonylimide.

[0008] According to the embodiment, a battery pack including the secondary battery of the embodiment is provided.

[0009] According to the embodiment, a vehicle including at least one of the secondary battery and the battery pack of the embodiment is provided. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a partially cutaway cross-sectional view of a secondary battery according to the embodiment. [Diagram 2] FIG. 2 is a side view of the battery of FIG. 1 . [Diagram 3] 2 is a cross-sectional view of the secondary battery according to the embodiment, taken in a direction perpendicular to the terminal extending direction. [Figure 4] FIG. 4 is an enlarged cross-sectional view of part A in FIG. 3 . [Diagram 5] FIG. 2 is a perspective view showing an example of a battery pack including the secondary battery according to the embodiment; [Figure 6] FIG. 2 is an exploded perspective view of the battery pack according to the embodiment. [Figure 7] FIG. 7 is a block diagram showing an electrical circuit of the battery pack of FIG. 6. [Figure 8] 1 is a schematic diagram showing an example of a vehicle equipped with a secondary battery according to an embodiment; [Figure 9]FIG. 13 is a diagram illustrating another example of a vehicle according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <First embodiment> According to the first embodiment, a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided. The non-aqueous electrolyte is a mixture of a non-aqueous solvent including a first solvent including at least one selected from the group consisting of ethyl propionate (EP), propyl propionate (PP), and ethyl butyrate (EB), and a second solvent including γ-butyrolactone, and lithium bisfluorosulfonylimide (LiN(FSO 2 ) 2 and an electrolyte comprising LiFSI.

[0012] It has been considered to improve the non-aqueous electrolyte to achieve both high-current discharge performance, low-temperature performance, and high-temperature life performance. Since non-aqueous electrolytes with high ionic conductivity in the low-temperature region tend to react easily with the positive electrode at high temperatures, it is difficult to obtain excellent life performance. Therefore, with non-aqueous electrolytes of the conventional composition, it has been difficult to achieve both high-current discharge performance, low-temperature performance, and high-temperature life performance.

[0013] A secondary battery including a positive electrode having a positive electrode current collector including at least one of aluminum and an aluminum alloy is provided, and the positive electrode potential is 4 V (vs. Li / Li) in a high temperature environment. +), the positive electrode collector corrodes and dissolves, and the positive electrode active material-containing layer peels off from the positive electrode collector. As a result, it becomes difficult to charge and discharge the secondary battery, and the life performance decreases. As a result of intensive research, the present inventors have found for the first time that a secondary battery having excellent large current performance, low temperature performance, and high temperature life performance can be obtained by using a non-aqueous electrolyte containing a first solvent consisting of at least one selected from the group consisting of ethyl propionate (EP), propyl propionate (PP), and ethyl butyrate (EB), a non-aqueous solvent containing a second solvent containing γ-butyrolactone (GBL), and an electrolyte containing lithium bisfluorosulfonylimide (LiFSI). According to the secondary battery of the embodiment, excellent large current performance and durability can be achieved in a wide range of temperatures from low temperature (for example, -70°C) to high temperature (for example, 70°C). Although the detailed mechanism is not clear, it is presumed to be as follows.

[0014] The non-aqueous electrolyte of the above composition can suppress the corrosion of the positive electrode current collector. LiFSI has high solubility in the second solvent GBL and can be dissolved to a high concentration, so that the ionic conductivity of the non-aqueous electrolyte can be increased, and the high current performance such as the high current discharge performance of the secondary battery can be improved. In addition, LiFSI is chemically stable at high temperatures in the non-aqueous electrolyte of the above composition, so that the life performance of the secondary battery at high temperatures can be improved. On the other hand, the first solvent can reduce the viscosity of the non-aqueous electrolyte, so that the low temperature performance of the secondary battery can be improved. In addition, the first solvent can increase the electrochemical stability of the non-aqueous electrolyte at high voltage and high temperature. Therefore, the electrochemical stability of the non-aqueous electrolyte with respect to the high voltage positive electrode can be increased, and the life performance of the secondary battery that can be used in a high temperature and high voltage charged state can be improved.

[0015] Therefore, a secondary battery excellent in large current performance, low temperature performance, and high temperature life performance can be provided by using a nonaqueous electrolyte in which LiFSI is dissolved in a nonaqueous mixed solvent containing the first solvent and the second solvent.

[0016] The nonaqueous electrolyte, the positive electrode, and the negative electrode will be described below. (Non-aqueous electrolyte) The electrolyte includes a non-aqueous solvent containing a first solvent consisting of at least one selected from the group consisting of ethyl propionate (EP), propyl propionate (PP) and ethyl butyrate (EB), a second solvent containing γ-butyrolactone (GBL), and an electrolyte containing lithium bisfluorosulfonylimide (LiFSI). The electrolyte is dissolved in the non-aqueous solvent.

[0017] The first solvent is a non-aqueous solvent that has excellent low-temperature performance due to its low viscosity, and is also electrochemically stable even at high voltages and high temperatures. Propyl propionate and ethyl butyrate have low melting points and high flash points, and belong to the second petroleum category. The first solvent, which is essentially composed of at least one of propyl propionate and ethyl butyrate, is easy to handle and can increase the mass production of secondary batteries.

[0018] The second solvent is a non-aqueous solvent containing γ-butyrolactone. LiFSI has high solubility in γ-butyrolactone and has excellent chemical stability to γ-butyrolactone. The second solvent may be composed of only γ-butyrolactone, or may contain a non-aqueous solvent other than γ-butyrolactone (hereinafter referred to as a third solvent). Examples of the third solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), methyl-ethyl-carbonate (MEC), dimethyl carbonate (DMC), and trimethyl phosphate (TMP). TMP is preferable because it has a fire-extinguishing effect and can make the electrolyte flame-retardant by adding it. Propylene carbonate is stable at high voltages, so it can increase the stability of the non-aqueous electrolyte at high voltages. In addition, propylene carbonate can form a coating on at least a part of the surface of the negative electrode active material-containing layer, thereby suppressing the reaction between the negative electrode active material and the non-aqueous electrolyte and the reaction between the conductive agent and the non-aqueous electrolyte. As a result, gas generation at high temperatures can be suppressed. The amount of the third solvent can be 5% by volume or more and 30% by volume or less in the total non-aqueous mixed solvent. This can improve the cycle life performance of the secondary battery.

[0019] The mixing ratio of the first solvent to the second solvent in the non-aqueous mixed solvent is preferably in the range of 9:1 to 1:3 in terms of the volume ratio of the first solvent:the second solvent. This range makes it possible to realize a secondary battery that is excellent in large current discharge performance, low temperature discharge performance, and high temperature cycle performance. The volume ratio is more preferably in the range of 4:1 to 1:2. Examples of preferred compositions of the non-aqueous mixed solvent are GBL and EP, GBL and PP, GBL and EB, GBL and EP and PP, GBL and PP and EB, GBL and PC and EP, GBL and PC and PP, GBL and PC and EB, GBL and EP and TMP, and GBL and PP and TMP.

[0020] The concentration of LiFSI in the non-aqueous electrolyte can be 0.8M (mol / L) or more and 4M (mol / L) or less. By setting it in this range, the non-aqueous electrolyte can have high ionic conductivity from low to high temperatures, so that the large current discharge performance of the secondary battery can be improved. By increasing the LiFSI concentration, it is possible to promote the generation of nitrogen-containing substances derived from LiFSI. On the other hand, by decreasing the LiFSI concentration, it is possible to promote the generation of nitrogen-containing substances derived from nitric acid compounds while increasing the ionic conductivity of the non-aqueous electrolyte. The preferred range of the LiFSI concentration as the electrolyte is 0.8M or more and 3M or less. A more preferred range is 1M or more and 2M or less.

[0021] The electrolyte can be dissolved in a non-aqueous solvent. The electrolyte may consist essentially of LiFSI, or may contain an electrolyte other than LiFSI (hereinafter referred to as a second electrolyte). An example of the second electrolyte is LiBF 4 , LiN(CF 3 SO 2 ) 2 Contains: LiBF 4 has high chemical stability against GBL, and aluminum fluoride (AlF 3) layer can be formed. The aluminum fluoride layer can suppress corrosion of the positive electrode current collector without inhibiting lithium ion conduction in the positive electrode, thereby improving the high-temperature life performance of the secondary battery. The concentration of the second electrolyte in the nonaqueous electrolyte can be 0.1M or more and 0.5M or less.

[0022] The non-aqueous electrolyte may contain at least one compound selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, boron-containing compounds, phosphorus-containing compounds, and fluorine-containing compounds. This allows a film or layer to be formed on at least one of the positive and negative electrodes, thereby achieving excellent cycle life performance not only near room temperature but also at high temperatures. The content of the at least one compound in the non-aqueous electrolyte may be 0.1% by weight or more and 10% by weight or less. A more preferred range is 0.5% by weight or more and 10% by weight or less.

[0023] An example of the nitrogen-containing compound is a nitrate. The nitrate dissolves in a non-aqueous electrolyte to produce NO 3 - It can be a salt that provides ions. An example of a nitrate is LiNO 3 , NaNO 3 , KNO 3 The type of nitrate used may be one or more. The nitrate can form a nitrogen-containing substance on at least a part of the surface of the positive electrode current collector even when the LiFSI concentration in the non-aqueous electrolyte is low. Among the nitrates, LiNO 3is preferable. Even if the LiFSI concentration in the non-aqueous electrolyte is increased without containing nitrate, the nitrogen-containing material can be formed on at least a part of the surface of the positive electrode current collector. The nitrogen-containing material can be present as a coating on the surface of the positive electrode current collector. The nitrogen-containing material can suppress corrosion of the positive electrode current collector at high potential and high temperature, and therefore can suppress peeling of the positive electrode active material-containing layer from the positive electrode current collector. The nitrogen-containing material can also be present on at least a part of the surface of at least one of the positive electrode active material-containing layer or the negative electrode active material-containing layer. The nitrogen-containing material can be a nitrogen-containing inorganic material. Examples of nitrogen-containing inorganic materials include nitric acid compounds, Li 3 Examples of metal nitrides include metal nitrides such as Li 3 Metal nitrides such as N have lithium ion conductivity, so the resistance of the coating containing the nitrogen-containing material can be reduced. Therefore, the metal nitride can improve the high current performance. On the other hand, the nitrate compound can suppress the decomposition of the non-aqueous electrolyte. The nitrate can form a nitrogen-containing material containing at least one of the nitrate compound and the metal nitride. The nitrate can form a nitrogen-containing material without affecting the ion conductivity of the non-aqueous electrolyte.

[0024] An example of a sulfur-containing compound is 1,3-propane sultone (PS). 1,3-propane sultone can form a coating containing S on at least a part of the surface of the positive electrode active material-containing layer, the negative electrode active material-containing layer, or both. This can suppress decomposition of the non-aqueous solvent, thereby suppressing gas generation at high temperatures.

[0025] An example of a boron-containing compound is lithium difluoro(oxalato)borate (LiBF 2 C 2 O 4 : LiDFOB), lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 LiBOB), Lithium tetrafluoroborate (LiBF 4 When the positive electrode current collector contains Al, LiDFOB, LiBF 4can form a film containing boron (B), oxygen (O), fluorine (F) and aluminum (Al) on the surface of the positive electrode current collector. As a result, even when the LiFSI concentration in the non-aqueous electrolyte is low or high, and even under high voltage or high temperature, the dissolution reaction due to corrosion of Al can be suppressed. This film preferably contains a substance having an Al-F bond, a BO bond and a BF bond. As a result, the charge-discharge cycle performance of the battery can be improved. The content of the boron-containing compound in the non-aqueous electrolyte is preferably 0.1% by weight or more and 5% by weight or less. By making the content 0.1% by weight or more, a film containing B is formed on the surface of the positive electrode current collector, and dissolution of the positive electrode current collector due to corrosion can be suppressed. By making the content 5% by weight or less, the ionic conductivity of the non-aqueous electrolyte can be increased. In addition, the boron-containing compound can form a film containing B on the surface of the negative electrode active material. The film containing B is stable, so that the reductive decomposition of the non-aqueous electrolyte can be suppressed. As a result, the charge / discharge efficiency of the negative electrode can be increased, and the cycle life performance of the battery can be improved.

[0026] An example of a phosphorus-containing compound is tris(trimethylsilyl) phosphate (TMSP). TMSP can form a coating containing P on at least a portion of the surface of the positive electrode active material-containing layer, the negative electrode active material-containing layer, or both. This can suppress decomposition of the non-aqueous solvent, thereby suppressing gas generation at high temperatures.

[0027] An example of a fluorine-containing compound is fluoroethylene carbonate (FEC). FEC can form a coating containing F on at least a part of the surface of the positive electrode active material-containing layer, the negative electrode active material-containing layer, or both. This can suppress the decomposition of the non-aqueous solvent, thereby suppressing gas generation at high temperatures. In addition, the film containing F can suppress the reductive decomposition of GBL in the non-aqueous solvent on the surface of the negative electrode active material, thereby improving the cycle life performance of the battery.

[0028] The form of the non-aqueous electrolyte is not particularly limited, and may be, for example, liquid, gel, solid, etc. The liquid non-aqueous electrolyte is substantially composed of a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. The gel or solid non-aqueous electrolyte may be a composite of a liquid non-aqueous electrolyte and a polymer material, in other words, a composite of a liquid non-aqueous electrolyte and a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), etc.

[0029] The non-aqueous electrolyte may contain a room temperature molten salt made of a non-volatile, non-flammable ionic liquid. The liquid non-aqueous electrolyte can improve the low temperature performance of the secondary battery.

[0030] An example of a method for forming a film or layer on at least one of the positive and negative electrodes (referred to as the first method) is described below. At least one compound selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, boron-containing compounds, phosphorus-containing compounds, and fluorine-containing compounds is added to a non-aqueous electrolyte in an amount of 0.1 to 10% by weight. A secondary battery is assembled comprising this non-aqueous electrolyte, a positive electrode, and a negative electrode. When the positive electrode potential is increased to 4 V (vs. Li / Li + A film-like or layer-like material can be formed on the electrode by aging a battery charged to 45° C. or higher at a temperature of 45 to 80° C. The film-like or layer-like material contains at least one element (atom) selected from the group consisting of N, S, B, P, and F.

[0031] The positive and negative electrodes used in assembling the secondary battery can be prepared, for example, by the following method. The positive electrode is prepared, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a positive electrode current collector, drying, and pressing. On the other hand, the negative electrode is prepared, for example, by suspending a negative electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a current collector, drying, and pressing. (Negative electrode) The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer that is supported on or in contact with one or both sides of the negative electrode current collector and contains a negative electrode active material. The negative electrode active material-containing layer may contain a binder, a conductive agent, or both.

[0032] The negative electrode active material may be, for example, a material that absorbs and releases (inserts and releases) Li (e.g., lithium ions). Examples of materials that absorb and release (inserts and releases) Li (e.g., lithium ions) include carbon materials, metal oxides, metal sulfides, Li alloys, etc. The type of negative electrode active material used may be one or more types.

[0033] Examples of carbon materials include graphite, carbon fiber, coke, non-graphitizable carbon, etc. Examples of metal sulfides include titanium sulfide, molybdenum sulfide, iron sulfide, etc. Examples of Li alloys include alloys containing at least one element selected from the group consisting of Si, Al, Sn, Zn, and Pb and Li.

[0034] Metal oxides, for example, can charge lithium ions at 0.5V (vs. Li / Li + ) or more 3.0V (vs.Li / Li + ) or less. Examples of the metal oxide include titanium-containing oxides and niobium-containing oxides. A negative electrode containing a negative electrode active material containing at least one of a titanium-containing oxide and a niobium-containing oxide has a lithium ion insertion / extraction potential of 0.5 to 3.0 V (vs. Li / Li + ), a stable coating film can be formed on the surface of the negative electrode active material-containing layer at high temperatures. This makes it possible to suppress the reductive decomposition of the nonaqueous electrolyte, thereby making it possible to obtain a nonaqueous electrolyte secondary battery with excellent life performance in a high-temperature environment. A more preferable range of the negative electrode potential is 0.7 (vs. Li / Li + ) or more 2V (vs.Li / Li + ) or less.

[0035] Examples of the titanium-containing oxide include lithium titanium-containing oxide and titanium oxide. Examples of the niobium-containing oxide include niobium titanium-containing oxide, niobium tungsten-containing oxide and niobium titanium molybdenum-containing oxide.

[0036] Examples of lithium titanium-containing oxides include those having a spinel structure (e.g., those having the general formula Li 4 / 3+a Ti 5 / 3 O 4 (0≦a≦2)), those having a ramsdellide structure (e.g., those having the general formula Li 2+a Ti 3 O 7 (0≦a≦1)), Li 1+b Ti 2 O 4 Lithium titanium-containing oxide represented by (0≦b≦1), Li 1.1+b Ti 1.8 O 4 Lithium titanium-containing oxide represented by (0≦b≦1), Li 1.07+b Ti 1.86 O 4 Examples of the lithium-titanium-containing oxide include a lithium-titanium-containing oxide represented by the formula (0≦b≦1) and a lithium-titanium-containing composite oxide containing at least one element selected from the group consisting of Nb, Mo, W, P, V, Sn, Cu, Ni, and Fe.

[0037] In addition, examples of lithium titanium-containing oxides include Li 2+a A d Ti 6-b B b O 14ーc (A is one or more elements selected from Na, K, Mg, Ca, and Sr, B is a metal element other than Ti, and 0≦a≦5, 0≦b≦6, 0≦c≦0.6, and 0≦d≦3) are included. 2+a A d Ti 6-b B b O 14ーc has a crystal structure in the space group Cmca.

[0038] Another example of the lithium titanium-containing oxide is an orthorhombic titanium-containing oxide. 2+a M I 2-b Ti 6-c M II d O 14+σ In this case, the compound represented by M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+a Na 2 Ti 6 O 14 (0≦a≦6).

[0039] Examples of titanium oxides include those with the general formula Li a TiO 2 (0≦a≦2). In this case, the composition before charging is TiO 2 Examples of titanium oxide include titanium oxide with a monoclinic structure (bronze structure (B)), titanium oxide with a rutile structure, titanium oxide with anatase structure, etc. TiO with a monoclinic structure (bronze structure (B)) 2 (B) is preferred. In addition, low-crystalline TiO 2 (B) is also preferred.

[0040] Examples of the niobium-containing oxide include niobium oxide, niobium titanium-containing oxide, niobium tungsten-containing oxide, and niobium titanium molybdenum-containing oxide.

[0041] Examples of niobium oxide include Nb 2 O 5 Includes:

[0042] Examples of niobium titanium oxides include monoclinic niobium titanium oxides, Ti 2 Nb 2 O 9 , Ti 2 Nb 10 O 29 , TiNb 14 O 37 , TiNb 24 O 62 The substituted niobium titanium composite oxides include those in which at least a portion of Nb and / or Ti is substituted with a different element. Examples of the substituting element include Na, K, Ca, Co, Ni, Si, P, V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Pb, and Al. The substituted niobium titanium composite oxides may contain one type of substituting element, or may contain two or more types of substituting elements.

[0043] Examples of monoclinic niobium titanium oxides include those represented by the general formula Li c TiNb d O 7 (0≦c≦5, 1≦d≦4). The more preferred composition is TiNb 2 O 7 It is.

[0044] As an example of a monoclinic niobium titanium oxide, Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0045] Another example of a monoclinic niobium titanium oxide is Ti 1-y M3 y+z Nb 2-z O 7-δHere, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦y<1, 0≦z<2, and -0.3≦δ≦0.3.

[0046] Examples of niobium-tungsten oxides include Nb 14 W 3 O 44 , Nb 16 W 5 O 55 ,Nb 18 W 8 O 69 etc.

[0047] Examples of niobium titanium molybdenum-containing oxides include those having the general formula Li a Ti b Nb 2-2d Mo c+2d O 2b+5+3c (wherein the subscripts a, b, c, and d are preferably within the ranges of 0≦a≦b+4+3c, 0.3≦b≦1.6, 0.3≦c<1.6, and 0≦d<0.4, respectively), and a tetragonal titanium-niobium-molybdenum composite oxide represented by the general formula Li a M b NbMo c O d where M is one or more selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si, and includes composite oxides in which 0≦a≦b+2+3c, 0≦b≦1.4, 0≦c≦0.5, and 2.33≦d / (1+b+c)≦2.50 are satisfied.

[0048] Li 4 / 3+a Ti 5 / 3 O 4 (0≦a≦2) or Li c TiNb d O 7The negative electrode active material containing at least one of (0≦c≦5, 1≦d≦4) can rapidly absorb and release lithium ions inside the active material and is electrochemically and chemically stable to the non-aqueous electrolyte, and therefore has excellent large current discharge performance, rapid charge performance, and cycle life performance. In addition, the negative electrode active material is stable to the first and second solvents even at high temperatures, and therefore has excellent durability and life performance.

[0049] The negative electrode active material particles may be in the form of primary particles, or may be in the form of secondary particles formed by agglomeration of primary particles, or may be a mixture of primary particles and secondary particles.

[0050] The average particle size of the primary particles of the negative electrode active material is preferably in the range of 0.05 to 1 μm. This can improve the large current performance. In addition, the particle shape can be either granular or fibrous to obtain good performance. In addition, when the negative electrode active material forms secondary particles, the average particle size of the secondary particles is preferably 2 to 20 μm. This can increase the electrode density and improve the cycle life performance.

[0051] The negative electrode active material has an average particle size of 2 μm or less and 2 The specific surface area measured by the BET method using adsorption is 2 to 50 m 2 / g, it is possible to further increase the affinity of the negative electrode with the non-aqueous electrolyte and the electrochemical stability.

[0052] The porosity of the negative electrode (excluding the current collector) is preferably in the range of 20 to 50%. This allows a high-density negative electrode to be obtained that has excellent affinity between the negative electrode and the non-aqueous electrolyte. The porosity is more preferably in the range of 25 to 40%.

[0053] The negative electrode current collector is different depending on the type of negative electrode active material. When a lithium alloy or a carbon material is used as the negative electrode active material, a copper foil can be used as the negative electrode current collector. Lithium ions can be added to the negative electrode active material at a voltage of 0.5 to 3.0 V (vs. Li / Li +When a metal oxide that is inserted and removed at a potential of 0.1 V is used, the negative electrode current collector can contain at least one of aluminum and an aluminum alloy. More preferred negative electrode current collectors are aluminum foil and aluminum alloy foil. The purity of the aluminum foil is preferably 99.99% or more. As the aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferred. On the other hand, transition metals such as iron, copper, nickel, and chromium are preferably 100 ppm or less.

[0054] The thickness of the negative electrode current collector is preferably 20 μm or less, and more preferably 15 μm or less.

[0055] The negative electrode active material-containing layer may contain a conductive agent. Examples of the conductive agent include carbon nanotubes, acetylene black, carbon black, coke (preferably with an average particle size of 10 μm or less at a heat treatment temperature of 800° C. to 2000° C.), carbon fiber, graphite, metal compound powders such as TiO, TiC, and TiN, and metal powders such as Al, Ni, Cu, and Fe. The conductive agent may be one or more kinds. By using carbon fiber with a fiber diameter of 1 μm or less, the electrode resistance is reduced and the cycle life performance is improved.

[0056] The negative electrode active material-containing layer may contain a binder. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, acrylic rubber, styrene butadiene rubber, core-shell binder, polyimide, and cellulose nanofiber. The type of binder may be one or more.

[0057] The compounding ratio of the negative electrode active material, conductive agent and binder is preferably in the range of 80 to 95% by weight of the negative electrode active material, 1 to 18% by weight of the conductive agent and 2 to 7% by weight of the binder.

[0058] The negative electrode is produced, for example, by suspending the negative electrode active material, the conductive agent, and the binder in a suitable solvent, applying the suspension to a current collector, drying, and pressing (for example, by hot pressing). (Positive Electrode) This positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer that is carried on or in contact with one side (one main surface) or both sides of the current collector and contains a positive electrode active material. The positive electrode active material-containing layer may contain a binder, a conductive agent, or both.

[0059] Examples of positive electrode active materials include Li x M y O 2 (0 < x ≤ 1, 0 < y ≤ 1, M is, for example, Mn), Li x M 2y O 4 (0 < x ≤ 1, 0 < y ≤ 1, M is, for example, Mn), lithium phosphate oxide having an olivine structure (for example, Li x M y PO 4 (M is at least one element selected from Mn, Ni, Co, and Fe, 0 < x ≤ 1.1, 0.8 ≤ y ≤ 1.1), Li x FePO 4 (0 < x ≤ 1.1), Li x Fe 1-y Mn y PO 4 (0 < x ≤ 1.1, 0 ≤ y ≤ 1), Li x CoPO 4 (0 < x ≤ 1.1), Li x MnPO 4 (0 < x ≤ 1.1)), lithium nickel cobalt composite oxide (for example, LixNi 1-a Co a O 2 (0 < x ≤ 1, 0 < a ≤ 1), lithium cobalt composite oxide (for example, Li x CoO 2 (0 < x ≤ 1), lithium nickel manganese cobalt composite oxide (for example, Li x Ni 1-a-b Mn a Co b O 2 (0 < x ≤ 1, 0 < 1 - a - b < 1, 0 < a < 1, 0 < b < 1), lithium manganese cobalt composite oxide (for example, Li x Mn 1-a Co a O 2 (0 < x ≤ 1, 0 < a < 1), spinel-type lithium manganese nickel composite oxide (for example, Lix Mn 2-a Ni a O 4 (where 0 < x ≤ 1, 0 < a < 2), fluorinated iron sulfate having a tabularite structure (e.g., Li x M y SO 4 F (0 < x ≤ 1, 0 < y ≤ 1, M is at least one of Fe or Mn), Li x Fe 1-a Mn a SO 4 F (0 < x ≤ 1, 0 < a ≤ 1), etc. are included. The type of the positive electrode active material can be one or more than one type.

[0060] The above positive electrode active material can obtain a high voltage of 4 V or more. Lithium nickel manganese cobalt composite oxide can obtain a high voltage of 4 V or more and can increase the energy density of the positive electrode.

[0061] A positive electrode containing at least one of lithium cobalt composite oxide, lithium nickel manganese cobalt composite oxide, lithium manganese composite oxide, and lithium phosphate having an olivine structure can improve the low-temperature output performance and high-temperature life performance of the secondary battery. This is because the growth of the film formed on the surface of the positive electrode is suppressed and the resistance of the positive electrode becomes small. In addition, since the stability in a high-temperature environment is increased, the storage performance can be improved. A more preferable positive electrode active material is Li x CoO 2 、Li x Ni 1-a-b Mn a Co b O 2 、Li x M 2y O 4 (0 < x ≤ 1, 0 < y ≤ 1, M contains Mn) 、 Li x Fe 1-y Mn y PO 4 It is a positive electrode active material composed of at least one of them.

[0062] The positive electrode active material particles may be in the form of primary particles, or may be in the form of secondary particles formed by agglomeration of primary particles, or may be a mixture of primary particles and secondary particles.

[0063] It is preferable that at least one element selected from Mg, Al, Ti, Nb, Sn, Zr, Ba, B, N, and C is present on the surface of the particles of the positive electrode active material. This makes it possible to suppress the oxidative decomposition reaction of the non-aqueous electrolyte in a high-temperature environment, thereby suppressing an increase in resistance. As a result, it is possible to improve the high-temperature life performance.

[0064] Each element of Mg, Al, Ti, Nb, Sn, Zr, Ba, B, and N may be attached to the surface of the positive electrode active material particles in the form of metal oxide particles, phosphate particles, or nitride particles having a particle diameter of 0.001 to 1 μm, or the surface may be coated with a metal oxide layer, a phosphate layer, a nitride layer, or a fluoride layer. Alternatively, the element may be dissolved in the vicinity of the surface of the positive electrode active material particles. Examples of metal oxides include MgO, Al 2 O 3 , SnO, ZrO 2 ,TiO 2 ,BaO,B 2 O 3 Examples of phosphorus oxide include AlPO 4 , Mg 3 (PO 4 ) 2 , Sn 3 (PO 4 ) 2 Nitrides include Li 3 Examples of the metal nitride include N. Examples of the fluoride include LiF and other metal fluorides. As for C, it is preferable that carbon particles having an average particle size of 1 μm or less are attached to the particle surface of the active material. The amount of the compound containing at least one element selected from the group consisting of Mg, Al, Ti, Nb, Sn, Zr, Ba, B, N, and C is preferably 0.001 to 3 wt % of the positive electrode active material. By setting it in this range, it is possible to suppress the reaction between the positive electrode and the non-aqueous electrolyte in a high-temperature environment and to suppress an increase in the interface resistance between the positive electrode and the non-aqueous electrolyte. Therefore, it is possible to improve the output performance and life performance of the secondary battery.

[0065] A film or layer containing at least one of a fluoride and a nitrogen-containing material may be formed on at least a part of the surface of the positive electrode active material-containing layer. This can suppress the oxidative decomposition of the non-aqueous electrolyte, thereby suppressing gas generation at high temperatures. Examples of fluorides include LiF, etc. Examples of nitrogen-containing materials include Li 3 N, etc. The film (layer) of the above composition is, for example, LiNO 3 The electrolyte may be formed from a non-aqueous electrolyte containing 0.5 to 10% by weight of the above.

[0066] The positive electrode current collector may contain at least one of aluminum and an aluminum alloy, and may be, for example, an aluminum foil or an aluminum alloy foil.

[0067] Nitrogen-containing substances may be present on at least a portion of the surface of the positive electrode current collector. This is because it is possible to suppress corrosion of the positive electrode current collector when the positive electrode operating voltage becomes high voltage of 4V or more under high temperature. By suppressing corrosion, the charge / discharge cycle proceeds smoothly, and the life performance can be improved. Examples of nitrogen-containing substances include nitric acid compounds, Li 3 Examples of the nitrogen-containing material include metal nitrides such as N. Details of the nitrogen-containing material are as described above in the non-aqueous electrolyte.

[0068] The nitrogen-containing substance is preferably present on at least a portion of the surface of the positive electrode current collector that is in contact with the positive electrode active material-containing layer, which can enhance the corrosion inhibition effect.

[0069] An example of a method for forming a nitrogen-containing material (hereinafter referred to as the second method) is described below. 3 A secondary battery having this non-aqueous electrolyte, a positive electrode, and a negative electrode was assembled, and then the positive electrode potential was increased to 4 V (vs. Li / Li +) or higher and aging the battery at a temperature of 45 to 80°C, a part or the whole of the surface of the positive electrode current collector can be covered with a nitrogen-containing material. In addition, after making the concentration of LiFSI in the non-aqueous electrolyte 1.5M or higher and assembling a secondary battery including this non-aqueous electrolyte, a positive electrode, and a negative electrode, when the positive electrode potential is 4V (vs. Li / Li + ) or more may be aged at a temperature of 45 to 80°C. In this case, in addition to the surface of the positive electrode current collector being partially or entirely covered with a nitrogen-containing material, a fluoride can also be present on the surface of the positive electrode current collector. Lithium nitrate can form a nitrogen-containing material on the surface of the positive electrode current collector without increasing the viscosity of the non-aqueous electrolyte and while maintaining the ionic conductivity of the non-aqueous electrolyte within a practical range.

[0070] The positive and negative electrodes used in assembling the secondary battery can be prepared, for example, by the following method. The positive electrode is prepared, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a positive electrode current collector, drying, and pressing. On the other hand, the negative electrode is prepared, for example, by suspending a negative electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a current collector, drying, and pressing.

[0071] It is desirable that at least a part of the surface of the positive electrode current collector contains a substance containing at least one element (atom) selected from the group consisting of N, B, and F. Examples of the form that the substance can take include a film-like substance and a layer-like substance. The substance can be a compound containing at least one element (atom) selected from the group consisting of N, B, and F. A substance containing B has excellent stability. Therefore, when the positive electrode current collector contains at least one of aluminum or an aluminum alloy, the effect of suppressing corrosion of the positive electrode current collector when the positive electrode operating voltage becomes a high voltage of 4V or more under high temperature can be enhanced. In addition, when the positive electrode current collector contains at least one of aluminum or an aluminum alloy, F can form a fluoride with Al, so that the substance containing F can be stably present on the surface of the positive electrode current collector. As a result, the effect of suppressing corrosion of the positive electrode current collector can be enhanced.

[0072] An example of the method (referred to as the third method) for forming a substance containing at least one element (atom) selected from the group consisting of N, B, and F on at least a part of the surface of the positive electrode current collector is the same method as described in the first method for forming a film-like or layer-like substance on at least one of the positive and negative electrodes. The method for forming the substance containing N may be the same as the method for forming a nitrogen-containing substance (second method).

[0073] The thickness of the positive electrode current collector can be 20 μm or less, and more preferably 15 μm or less.

[0074] The positive electrode active material-containing layer may contain a conductive agent. Examples of the conductive agent include acetylene black, carbon black, graphite, etc. The conductive agent may be one type or two or more types.

[0075] The positive electrode active material-containing layer may contain a binder. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and acrylic materials. The type of binder may be one or more types.

[0076] The compounding ratio of the positive electrode active material, conductive agent, and binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 19% by weight of the conductive agent, and 1 to 7% by weight of the binder.

[0077] The specific surface area of ​​the positive electrode active material-containing layer by the BET method is 0.1 to 2 m 2 It is preferable that the range is / g.

[0078] The positive electrode active material-containing layer may be porous.

[0079] The positive electrode is produced, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying this suspension to a positive electrode current collector, drying, and pressing.

[0080] The secondary battery of the embodiment may include a separator and an exterior member in addition to the non-aqueous electrolyte, the negative electrode, and the positive electrode. The negative electrode, the positive electrode, and the separator can constitute an electrode group. The non-aqueous electrolyte can be held in the electrode group. The form of the electrode group is not particularly limited, and can be, for example, a stacked type or a wound type. (Separator) The separator is disposed between the positive electrode and the negative electrode. A part of the separator may face or be in contact with only the positive electrode or only the negative electrode.

[0081] Examples of the separator include synthetic resin nonwoven fabric, polyethylene porous film, polypropylene porous film, cellulose nonwoven fabric, and the like.

[0082] At least a portion of the surface of the separator may be covered with a layer containing inorganic particles such as alumina. (Exterior materials) At least a positive electrode, a negative electrode, and a non-aqueous electrolyte are housed in the exterior member. The positive electrode and the negative electrode may be housed in the exterior member in the form of an electrode group with a separator or the like disposed between them.

[0083] The exterior member may be a metal container or a laminated film container.

[0084] The metal container may be a rectangular or cylindrical metal can made of aluminum, aluminum alloy, iron, stainless steel, etc. The metal container may be provided with a lid. The thickness of the container is preferably 0.5 mm or less, more preferably 0.3 mm or less.

[0085] The laminate film may be, for example, a multi-layer film in which an aluminum foil is coated with a resin film. Polymers such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used as the resin. The thickness of the laminate film is preferably 0.2 mm or less. The purity of the aluminum foil is preferably 99.5% or more.

[0086] The metal can made of an aluminum alloy is preferably an alloy containing elements such as manganese, magnesium, zinc, and silicon with an aluminum purity of 99.8% or less. The strength of the metal can made of an aluminum alloy is dramatically increased, allowing the can wall thickness to be reduced. As a result, a battery that is thin, lightweight, high-power, and excellent in heat dissipation can be realized.

[0087] Next, a method for checking nitrogen-containing substances will be explained.

[0088] First, a method for removing an electrode (positive or negative electrode) from a battery will be described.

[0089] The secondary battery is disassembled under an argon atmosphere, and the positive electrode collector, positive electrode, or negative electrode to be measured is taken out. The measurement objects are washed with a solvent consisting of dimethyl carbonate under an argon atmosphere, vacuum dried at 100°C, and then measured using the method described below. <How to check for nitrogen content> Whether or not a nitrogen-containing compound is present on the surface of the positive electrode current collector and the positive electrode active material-containing layer can be confirmed by X-ray Photoelectron Spectroscopy (XPS) under the conditions described below.

[0090] The XPS device used may be a Quantera SXM manufactured by ULVAC-PHI, Inc., or a device with equivalent functions. Single crystal spectroscopic Al-Kα radiation (1486.6 eV) is used as the excitation X-ray source. The X-ray output is 4 kW (13 kV x 310 mA), the photoelectron detection angle is 45°, and the analysis area is approximately 4 mm x 0.2 mm. Scanning is performed at 0.10 eV / step.

[0091] For example, Li 3 N was detected by detecting the spectrum originating from the Li-N bond (399 eV) in the state analysis of the surface (N1s) of the positive electrode current collector (e.g., aluminum foil). 3 On the other hand, nitrate compounds can be detected by analyzing the state of the surface (N1s) of the positive electrode current collector (e.g., aluminum foil) and can be found as NO 3 - The presence of nitrate compounds can be confirmed by detecting the spectrum resulting from the bond (407 eV).

[0092] Whether or not a fluorine-containing substance or a boron-containing substance is present on the surface of the positive electrode current collector can be confirmed by the method described below. <How to check for fluorine content> Using the same experimental method and measuring equipment as the method for confirming nitrogen content, for example, in the state analysis of the positive electrode current collector, AlF originating from the Al-F bond (686.3 eV) in the XPS pattern of F1s was identified. 3 Alternatively, LiF derived from the Li-F bond (685.01 eV) can be identified as a fluorine-containing material. <How to check for boron content> Using the same experimental method and measuring equipment as the method for confirming nitrogen content, for example, in the state analysis of the positive electrode current collector, B originating from the BO bond (193.1 eV) in the B1s XPS pattern was identified. 2 O 3 or AlBO 3 can be identified as containing boron. <Measurement of the average particle size of active material particles> The average particle size of the active material particles is measured using a laser diffraction particle size distribution measuring device (Shimadzu SALD-300 manufactured by Shimadzu Corporation or a device with equivalent functions). After adding about 0.1 g of the sample, a surfactant, and 1 to 2 mL of distilled water to a beaker and stirring thoroughly, the mixture is poured into a stirring water tank, and the light intensity distribution is measured 64 times at 2-second intervals, and the average particle size is obtained from the obtained particle size distribution data. <N of active materials and electrodes 2 Measurement of BET specific surface area by adsorption> N in active material 2 When measuring the BET specific surface area by adsorption, 1 g of the active material powder is prepared as a sample. 2 When measuring the BET specific surface area by adsorption, the electrode is 2x2cm 2 Two pieces of the sample were cut to the size of 100 mm. The BET specific surface area was measured using a Yuasa Ionics Co., Ltd. device, and nitrogen gas was used as the adsorption gas. <Method for measuring the porosity of the negative electrode> The porosity of the negative electrode is calculated by comparing the volume of the negative electrode active material-containing layer with the volume of the negative electrode active material-containing layer when the porosity is 0%, and regarding the increase from the volume of the negative electrode active material-containing layer when the porosity is 0% as the pore volume. Note that, when the negative electrode active material-containing layer is formed on both sides of the current collector, the volume of the negative electrode active material-containing layer is the total volume of the negative electrode active material-containing layer on both sides. <Cathode active material> The crystal structure and elemental composition of the positive electrode active material can be confirmed by powder X-ray diffraction (XRD) measurement and inductively coupled plasma (ICP) emission spectroscopy. <Negative electrode active material> The crystal structure and elemental composition of the negative electrode active material can be confirmed by powder X-ray diffraction (XRD) measurement and inductively coupled plasma (ICP) emission spectroscopy.

[0093] An example of a secondary battery according to an embodiment will be described with reference to FIGS.

[0094] 1 and 2 show an example of a secondary battery using a metal container.

[0095] The electrode group 1 is housed in a rectangular cylindrical metal container 2. The electrode group 1 has a structure in which a separator 5 is interposed between a positive electrode active material-containing layer of a positive electrode 3 and a negative electrode active material-containing layer of a negative electrode 4, and these are wound in a spiral shape to form a flat shape. The separator 5 covers the surface of the positive electrode active material-containing layer or the negative electrode active material-containing layer. As shown in FIG. 2, a strip-shaped positive electrode lead 6 is electrically connected to each of a plurality of points on the end of the positive electrode 3 located on the end face of the electrode group 1. In addition, a strip-shaped negative electrode lead 7 is electrically connected to each of a plurality of points on the end of the negative electrode 4 located on this end face. The plurality of positive electrode leads 6 are electrically connected to a positive electrode conductive tab 8 in a bundled state. The positive electrode lead 6 and the positive electrode conductive tab 8 constitute a positive electrode terminal. In addition, the negative electrode lead 7 is connected to a negative electrode conductive tab 9 in a bundled state. The negative electrode lead 7 and the negative electrode conductive tab 9 constitute a negative electrode terminal. A metallic sealing plate 10 is fixed to the opening of the metallic container 2 by welding or the like. The positive electrode conductive tab 8 and the negative electrode conductive tab 9 are each pulled out to the outside through an extraction hole provided in the sealing plate 10. The inner circumferential surface of each extraction hole in the sealing plate 10 is covered with an insulating member 11 to prevent a short circuit due to contact with the positive electrode conductive tab 8 and the negative electrode conductive tab 9.

[0096] 3 and 4 show an example of a secondary battery using an exterior member made of a laminate film.

[0097] As shown in FIG. 3 and FIG. 4, the flat wound electrode group 1 is housed in a bag-shaped exterior member 12 made of a laminate film in which a metal layer is interposed between two resin films. The flat wound electrode group 1 is formed by spirally winding a laminate in which a negative electrode 4, a separator 15, a positive electrode 3, and a separator 15 are laminated from the outside in this order, and press-molding the laminate. The outermost negative electrode 4 has a configuration in which a negative electrode active material-containing layer 4b containing a negative electrode active material is formed on one side of the inner surface side of a negative electrode current collector 4a as shown in FIG. 4, and the other negative electrodes 4 are configured by forming a negative electrode active material-containing layer 4b on both sides of a negative electrode current collector 4a. The positive electrode 3 is configured by forming a positive electrode active material-containing layer 3b on both sides of a positive electrode current collector 3a.

[0098] Near the outer peripheral end of the wound electrode group 1, the negative electrode terminal 13 is connected to the negative electrode current collector 4a of the outermost negative electrode 4, and the positive electrode terminal 14 is connected to the positive electrode current collector 3a of the inner positive electrode 3. These negative electrode terminal 13 and positive electrode terminal 14 extend outward from an opening of the bag-shaped exterior member 12. The opening of the bag-shaped exterior member 12 is heat-sealed to seal the wound electrode group 1. When heat-sealing, the negative electrode terminal 13 and positive electrode terminal 14 are sandwiched by the bag-shaped exterior member 12 at this opening.

[0099] The secondary battery of the embodiment described above contains a nonaqueous solvent containing a first solvent consisting of at least one selected from the group consisting of EP, PP, and EB, a second solvent containing GBL, and a nonaqueous electrolyte containing an electrolyte containing LiFSI. Therefore, corrosion of the positive electrode current collector can be suppressed, and a secondary battery excellent in large current performance, low temperature performance, and high temperature life performance can be realized. <Second embodiment> The battery pack of the second embodiment includes a plurality of the secondary batteries of the embodiment.

[0100] Examples of the assembled battery include one including a plurality of unit cells electrically connected in series and / or in parallel as a constituent unit, one including a first unit including a plurality of unit cells electrically connected in series or a second unit including a plurality of unit cells electrically connected in parallel, etc. The assembled battery may include at least one of these configurations.

[0101] Examples of the configuration in which a plurality of secondary batteries are electrically connected in series and / or in parallel include a configuration in which a plurality of batteries each having an exterior member are electrically connected in series and / or in parallel, and a configuration in which a plurality of electrode groups or bipolar electrode bodies housed in a common case are electrically connected in series and / or in parallel. A specific example of the former is a configuration in which the positive and negative terminals of a plurality of secondary batteries are connected by a metal bus bar (e.g., aluminum, nickel, copper). A specific example of the latter is a configuration in which a plurality of electrode groups or bipolar electrode bodies are housed in one case in a state in which they are electrochemically insulated by a partition wall, and these are electrically connected in series. In the case of a secondary battery, by setting the number of batteries electrically connected in series to the range of 5 to 7, the voltage compatibility with a lead-acid battery is improved. In order to further increase the voltage compatibility with a lead-acid battery, a configuration in which 5 or 6 unit cells are connected in series is preferable.

[0102] The case that houses the battery pack can be a metal can made of aluminum alloy, iron, stainless steel, etc., a plastic container, etc. The plate thickness of the container is preferably 0.5 mm or more.

[0103] An example of a battery pack will be described with reference to Fig. 5. The battery pack 200 shown in Fig. 5 is a rectangular secondary battery 100 shown in Fig. 1 ~100 5 The battery 100 includes a plurality of unit cells. 1 The positive electrode conductive tab 8 of the battery 100 located next to it. 2 The negative electrode conductive tab 9 is electrically connected to the negative electrode conductive tab 9 by a lead or bus bar 21. 2 The positive electrode conductive tab 8 and the battery 100 located next to it 3 The negative electrode conductive tab 9 is electrically connected to the negative electrode conductive tab 9 by a lead or bus bar 21. 1 ~100 5 are connected in series.

[0104] The battery pack of the embodiment described above includes the secondary battery of the embodiment, and therefore it is possible to realize a battery pack that is excellent in large current performance, low temperature performance, and high temperature life performance. <Third embodiment> The battery pack according to the third embodiment may include one or more secondary batteries (single cells) according to the embodiment. The secondary batteries may be electrically connected in series, in parallel, or in a combination of series and parallel to form a battery pack. The battery pack according to the embodiment may include a plurality of battery packs.

[0105] The battery pack according to the embodiment may further include a protection circuit. The protection circuit has a function of controlling charging and discharging of the secondary battery. Alternatively, a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack as a power source may be used as the protection circuit for the battery pack.

[0106] The battery pack according to the embodiment may further include an external terminal for current flow. The external terminal for current flow is for outputting current from the secondary battery to the outside and inputting current to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for current flow. When charging the battery pack, a charging current (including regenerative energy of the power of a vehicle such as an automobile) is supplied to the battery pack through the external terminal for current flow.

[0107] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0108] Fig. 6 is an exploded perspective view showing an example of a battery pack according to an embodiment of the present invention, and Fig. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 6.

[0109] The battery pack 300 shown in Figs. 6 and 7 includes a container 31, a lid 32, a protective sheet 33, a battery pack 200, a printed wiring board 34, wiring 35, and an insulating plate (not shown).

[0110] 6 is a bottomed, square container having a rectangular bottom. The container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring board 34, and wiring 35. The lid 32 has a rectangular shape. The lid 32 covers the container 31 to accommodate the battery pack 200 and the like. Although not shown, the container 31 and the lid 32 are provided with openings or connection terminals for connection to an external device or the like.

[0111] The battery pack 200 includes a plurality of cells 100, a positive electrode lead 22, a negative electrode lead 23, and an adhesive tape 24.

[0112] At least one of the plurality of unit cells 100 is a secondary battery according to the embodiment. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. 7. The plurality of unit cells 100 may be electrically connected in parallel, or may be connected in a combination of series and parallel connections. When the plurality of unit cells 100 are connected in parallel, the battery capacity is increased compared to when they are connected in series.

[0113] The adhesive tape 24 fastens the plurality of unit cells 100. The plurality of unit cells 100 may be fixed using heat shrink tape instead of the adhesive tape 24. In this case, the protective sheets 33 are disposed on both side surfaces of the battery pack 200, the heat shrink tape is wrapped around the battery pack 200, and the heat shrink tape is then thermally shrunk to bind the plurality of unit cells 100 together.

[0114] One end of the positive electrode lead 22 is connected to the battery pack 200. One end of the positive electrode lead 22 is electrically connected to the positive electrode of one or more cells 100. One end of the negative electrode lead 23 is connected to the battery pack 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0115] The printed wiring board 34 is disposed along one of the short side surfaces of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 342, a negative connector 343, a thermistor 345, a protection circuit 346, wiring 342a and 343a, an external terminal 350 for supplying electricity, a positive wiring (positive wiring) 348a, and a negative wiring (negative wiring) 348b. One main surface of the printed wiring board 34 faces one side of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring board 34 and the battery pack 200.

[0116] The other end 22a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342. The other end 23a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343.

[0117] The thermistor 345 is fixed to one main surface of the printed wiring board 34. The thermistor 345 detects the temperature of each of the cells 100, and transmits a detection signal to the protection circuit 346.

[0118] The external terminal 350 for current supply is fixed to the other main surface of the printed wiring board 34. The external terminal 350 for current supply is electrically connected to a device present outside the battery pack 300. The external terminal 350 for current supply includes a positive terminal 352 and a negative terminal 353.

[0119] The protection circuit 346 is fixed to the other main surface of the printed wiring board 34. The protection circuit 346 is connected to the positive terminal 352 via a positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via a negative wiring 348b. The protection circuit 346 is also electrically connected to the positive electrode connector 342 via a wiring 342a. The protection circuit 346 is electrically connected to the negative electrode connector 343 via a wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

[0120] The protective sheet 33 is disposed on both inner surfaces in the long side direction of the container 31 and on the inner surface in the short side direction that faces the printed wiring board 34 via the battery pack 200. The protective sheet 33 is made of, for example, resin or rubber.

[0121] The protection circuit 346 controls charging and discharging of the multiple cells 100. In addition, the protection circuit 346 cuts off electrical connection between the protection circuit 346 and external terminals 350 (positive terminal 352, negative terminal 353) for supplying electricity to an external device, based on a detection signal transmitted from the thermistor 345, or a detection signal transmitted from each of the cells 100 or the battery pack 200.

[0122] An example of the detection signal transmitted from the thermistor 345 is a signal that detects that the temperature of the cell 100 is equal to or higher than a predetermined temperature. An example of the detection signal transmitted from each cell 100 or the battery pack 200 is a signal that detects overcharging, overdischarging, and overcurrent of the cell 100. When detecting overcharging or the like for each cell 100, 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 cell 100.

[0123] The protection circuit 346 may be a circuit included in a device (such as an electronic device or an automobile) that uses the battery pack 300 as a power source.

[0124] As described above, the battery pack 300 includes the external terminal 350 for current supply. Therefore, the battery pack 300 can output a current from the assembled battery 200 to an external device and input a current from the external device to the assembled battery 200 via the external terminal 350 for current supply. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 350 for current supply. When the battery pack 300 is charged, a charging current from the external device is supplied to the battery pack 300 through the external terminal 350 for current supply. When the battery pack 300 is used as an in-vehicle battery, regenerative energy of the vehicle's power can be used as the charging current from the external device.

[0125] The battery pack 300 may include a plurality of assembled batteries 200. In this case, the plurality of assembled batteries 200 may be connected in series, in parallel, or in a combination of series and parallel connections. The printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode lead 22 and the negative electrode lead 23 may be used as a positive terminal and a negative terminal, respectively, of the external terminals for current supply.

[0126] Such a battery pack is used in applications that require excellent cycle performance, for example, when a large current is drawn. Specifically, the battery pack is used, for example, as a power source for electronic devices, a stationary battery, or an on-board battery for various vehicles (including a battery for railway vehicles). An example of the electronic device is a digital camera. The battery pack is particularly suitable for use as an on-board battery.

[0127] The battery pack according to the embodiment includes the secondary battery according to the embodiment or the battery pack according to the embodiment, and therefore it is possible to realize a battery pack that has excellent large current performance, low temperature performance, and high temperature life performance. <Fourth embodiment> According to a fourth embodiment, a vehicle is provided. The vehicle is equipped with a battery pack according to the embodiment.

[0128] In the vehicle according to the embodiment, the battery pack, for example, recovers regenerative energy of the vehicle's motive power. The vehicle may include a mechanism (for example, a regenerator) that converts the kinetic energy of the vehicle into regenerative energy.

[0129] Examples of vehicles according to the embodiment include two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, power-assisted bicycles, and rail vehicles.

[0130] The mounting position of the battery pack in the vehicle according to the embodiment is not particularly limited. For example, when the battery pack is mounted in an automobile, the battery pack can be mounted in the engine compartment, the rear of the vehicle body, or under the seat of the vehicle.

[0131] The vehicle according to the embodiment may be equipped with a plurality of battery packs. In this case, the batteries included in each battery pack may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections. For example, when each battery pack includes a battery pack, the battery packs may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections. Alternatively, when each battery pack includes a single battery, the batteries may be electrically connected in series, electrically connected in parallel, or electrically connected by a combination of series and parallel connections.

[0132] Next, an example of a vehicle according to an embodiment will be described with reference to the drawings.

[0133] FIG. 8 is a partial see-through view that illustrates an example of a vehicle according to the embodiment.

[0134] A vehicle 400 shown in Fig. 8 includes a vehicle body 40 and a battery pack 300 according to the third embodiment. In the example shown in Fig. 8, the vehicle 400 is a four-wheeled automobile.

[0135] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (e.g., single cells or assembled batteries) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0136] 8 illustrates an example in which the battery pack 300 is mounted in an engine room located in the front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, in the rear of the vehicle body 40 or under a seat. This battery pack 300 can be used as a power source for the vehicle 400. In addition, this battery pack 300 can recover regenerative energy for the motive power of the vehicle 400.

[0137] Next, an embodiment of a vehicle according to the present embodiment will be described with reference to FIG.

[0138] Fig. 9 is a diagram illustrating an example of a control system for an electrical system in a vehicle according to an embodiment. A vehicle 400 illustrated in Fig. 9 is an electric vehicle.

[0139] The vehicle 400 shown in FIG. 9 comprises a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 which is a higher-level control device of the vehicle power supply 41, an external terminal (terminal for connecting to an external power supply) 43, an inverter 44, and a drive motor 45.

[0140] The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine compartment, the rear of the vehicle body, or under a seat. Note that in the vehicle 400 shown in Fig. 9, the mounting location of the vehicle power supply 41 is shown diagrammatically.

[0141] The vehicle power supply 41 includes a plurality of (eg, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

[0142] The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300a to 300C are battery packs similar to the above-mentioned battery pack 300, and the assembled batteries 200a to 200c are assembled batteries similar to the above-mentioned battery pack 200. The assembled batteries 200a to 200c are electrically connected in series. The battery packs 300a, 300b, and 300c can be removed independently and replaced with another battery pack 300.

[0143] Each of the assembled batteries 200a to 200c includes a plurality of unit cells connected in series. At least one of the plurality of unit cells is a secondary battery according to the embodiment. The assembled batteries 200a to 200c are charged and discharged via a positive terminal 413 and a negative terminal 414, respectively.

[0144] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c, and collects information on the voltage, temperature, and the like of each of the cells 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. In this way, the battery management device 411 collects information on the maintenance of the vehicle power supply 41.

[0145] The battery management unit 411 and the assembled battery monitoring units 301a to 301c are connected via a communication bus 412. In the communication bus 412, one set of communication lines is shared by a plurality of nodes (the battery management unit 411 and one or more assembled battery monitoring units 301a to 301c). The communication bus 412 is a communication bus configured based on, for example, the CAN (Control Area Network) standard.

[0146] The battery pack monitoring devices 301a to 301c measure the voltage and temperature of each of the cells constituting the battery packs 200a to 200c based on commands communicated from the battery management device 411. However, the temperature can be measured at only a few points per battery pack, and it is not necessary to measure the temperatures of all the cells.

[0147] The vehicle power supply 41 may also have an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) that switches between the presence and absence of an electrical connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a pre-charge switch (not shown) that is turned on when the assembled batteries 200a-200c are charged, and a main switch (not shown) that is turned on when the output from the assembled batteries 200a-200c is supplied to a load. Each of the pre-charge switch and the main switch includes a relay circuit (not shown) that is switched on or off by a signal supplied to a coil disposed in the vicinity of the switch element. The electromagnetic contactor such as the switch device 415 is controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 that controls the operation of the entire vehicle 400.

[0148] The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 is controlled based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0149] The drive motor 45 rotates by electric power supplied from the inverter 44. A driving force generated by the rotation of the drive motor 45 is transmitted to the axles and drive wheels W via, for example, a differential gear unit.

[0150] Although not shown, the vehicle 400 is also provided with a regenerative braking mechanism. The regenerative braking mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to the inverter 44 and converted into a direct current. The converted direct current is input to the vehicle power supply 41.

[0151] One terminal of a connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41. The other terminal of the connection line L1 is connected to a negative input terminal 417 of the inverter 44. A current detection unit (current detection circuit) 416 in the battery management device 411 is provided between the negative terminal 414 and the negative input terminal 417 on the connection line L1.

[0152] One terminal of a connection line L2 is connected to the positive electrode terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to a positive electrode input terminal 418 of the inverter 44. A switch device 415 is provided in the connection line L2 between the positive electrode terminal 413 and the positive electrode input terminal 418.

[0153] The external terminal 43 is connected to the battery management unit 411. The external terminal 43 can be connected to, for example, an external power source.

[0154] In response to operational inputs from the driver or the like, the vehicle ECU 42 coordinates with other management devices and control devices including the battery management device 411 to control the vehicle power supply 41, the switch device 415, the inverter 44, etc. Through the coordinated control of the vehicle ECU 42, etc., the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 are controlled, and the entire vehicle 400 is managed. Data relating to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, is transferred between the battery management device 411 and the vehicle ECU 42 via a communication line.

[0155] The vehicle according to the embodiment is equipped with the battery pack according to the embodiment, and therefore, it is possible to realize a vehicle that has excellent running performance in a wide temperature range from low to high temperatures. EXAMPLES

[0156] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the embodiments described below.

[0157] Example 1 The positive electrode active material is a layered lithium nickel cobalt manganese composite oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) particles were used. 8% by weight of graphite powder was added as a conductive agent to the positive electrode active material-containing layer, and 5% by weight of PVdF was added as a binder to the positive electrode active material-containing layer. The mixture was dispersed in n-methylpyrrolidone (NMP) solvent to prepare a slurry. The slurry was applied to both sides of a 15 μm-thick aluminum alloy foil (purity 99%), dried, and pressed to obtain a coating amount of 12.8 mg / cm on one side. 2 The thickness of the positive electrode active material-containing layer on one side is 43 μm, and the electrode density is 3.0 g / cm 3 The BET specific surface area of ​​the positive electrode active material-containing layer was 0.5 m 2 / g.

[0158] In addition, the average particle size is 0.6 μm and the BET specific surface area is 8 m 2 / g, Li absorption potential is 1.55V (vs. Li / Li + ) spinel type lithium titanate (Li 4 Ti 5 O 12 ) powder with an average particle size of 0.4 μm and a BET specific surface area of ​​50 m 2 A mixture of coke powder (1.0 g / g), acetylene black powder, and PVdF as a binder was mixed in a weight ratio of 90:6:2:2 and dispersed in n-methylpyrrolidone (NMP) solvent to prepare a slurry. The obtained slurry was applied to an aluminum alloy foil (purity 99.3%) with a thickness of 15 μm, dried, and pressed to obtain a coating amount of 13 mg / cm on one side. 2 The thickness of the negative electrode active material-containing layer on one side is 59 μm, and the electrode density is 2.2 g / cm3 The negative electrode porosity excluding the current collector was 35%. The BET specific surface area of ​​the negative electrode active material-containing layer (surface area per 1 g of the negative electrode active material-containing layer) was 10 m 2 / g.

[0159] A separator made of a 20 μm thick polyethylene porous film was placed on the positive electrode to cover it. The separator-covered positive electrode was placed on the negative electrode, with the positive electrode active material-containing layer facing the negative electrode active material-containing layer via the separator, and these were spirally wound to prepare an electrode group. This electrode group was pressed to form a flat shape. The electrode group was stored in a container made of a thin metal can made of an aluminum alloy (Al purity 99%) with a thickness of 0.25 mm.

[0160] As a non-aqueous electrolyte, a first solvent made of EP and a second solvent made of GBL were mixed so that the volume ratio of the first solvent to the second solvent was 7:3 (70 volume%:30 volume%). 1.2 M (mol / L) of lithium bisfluorosulfonylimide (LiN(FSO 2 ) 2 ) was dissolved in the solution. 1% by weight of LiNO was added as an additive. 3 A liquid nonaqueous electrolyte (nonaqueous electrolytic solution) was prepared by adding 1% by weight of PS to the electrolyte. This nonaqueous electrolyte was poured into the electrode group in the container to fabricate a thin nonaqueous electrolyte secondary battery having the structure shown in Figure 1 and measuring 4 mm in thickness, 30 mm in width, and 60 mm in height.

[0161] Before the charge-discharge test, the fabricated nonaqueous electrolyte battery was charged at 0.7 A to 3.0 V in a 60°C environment, and the positive electrode potential was 4 V (vs. Li / Li + After that, a high-temperature aging treatment was performed at 60° C. for 24 hours to obtain a non-aqueous electrolyte secondary battery.

[0162] The obtained secondary battery had Li on a part of the surface of the positive electrode current collector that was in contact with the positive electrode active material-containing layer. 3The presence of N and nitrate compounds was confirmed by the surface analysis using the above-mentioned X-ray photoelectron spectroscopy (XPS). In addition, the same surface analysis confirmed that Li was present on a part of the surface of the positive electrode active material-containing layer. 3 The presence of N and nitrate compounds was confirmed. 3 N originates from the Li-N bond (399 eV). On the other hand, the nitrate compound is NO 3 - This was due to the bond (407 eV).

[0163] (Examples 2 to 22) A thin nonaqueous electrolyte battery was fabricated in the same manner as described in Example 1 above, except for the nonaqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Tables 1 to 3 below. In the nonaqueous solvent composition columns shown in Tables 1 to 3, the volume percentage of each nonaqueous solvent is shown in the upper row, and the volume ratio of the first solvent to the second solvent is shown in the lower row. The electrolyte column shows the type and concentration (M (mol / L)) of the electrolyte used. Meanwhile, the additive column shows the components other than the nonaqueous solvent in the nonaqueous electrolyte and their contents (wt%).

[0164] In the secondary batteries of Examples 2 to 5, 8 to 13, 16 to 19, and 21, Li was added to a portion of the surface of the positive electrode current collector that was in contact with the positive electrode active material-containing layer. 3 The above-mentioned surface analysis confirmed the presence of N and nitrate compounds. The above-mentioned surface analysis also confirmed that Li was present on a part of the surface of the positive electrode active material-containing layer. 3 The presence of N and nitrate compounds was confirmed.

[0165] On the other hand, in the secondary batteries of Examples 6, 7, 14, 15, and 22, the presence of a nitrogen-containing compound was confirmed by the above-mentioned surface analysis on a part of the surface of the positive electrode current collector that contacts the positive electrode active material-containing layer. Also, the above-mentioned surface analysis confirmed the presence of a nitrogen-containing compound on a part of the surface of the positive electrode active material-containing layer. In the secondary battery of Example 20, the presence of a fluoride and a nitrogen-containing compound was confirmed on a part of the surface of the positive electrode current collector that contacts the positive electrode active material-containing layer and on a part of the surface of the positive electrode active material-containing layer.

[0166] The positive and negative electrode active materials used in the examples are described in detail below.

[0167] TiNb 2 O 7 The particles have a monoclinic structure, an average particle size of 1 μm, and a BET specific surface area of ​​3 m 2 / g, Li absorption potential is 1 to 2 V (vs. Li / Li + ) was.

[0168] TiO 2 (B) The particles have a monoclinic structure, an average particle size of 10 μm, a BET specific surface area of ​​10 m 2 / g, Li absorption potential is 1 to 2 V (vs. Li / Li + ) was.

[0169] Nb 16 W 5 O 55 The particles have an average particle size of 1 μm and a BET specific surface area of ​​3 m 2 / g, Li absorption potential is 0.8 to 2.2 V (vs. Li / Li + ) was.

[0170] LiNi 0.5 Co 0.2 Mn 0.3 O 2 The particles had a layered structure and an average particle size of 3 μm.

[0171] LiNi 0.5 Co 0.3 Mn 0.2 O 2 The particles had a layered structure and an average particle size of 3 μm. (Comparative Examples 1 to 9) A thin nonaqueous electrolyte battery was fabricated in the same manner as described in Example 1, except for the nonaqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Table 3 below. 3 SO 2 ) 2 is lithium bistrifluoromethylsulfonylimide.

[0172] In the secondary battery of Comparative Example 1, Li was charged to a part of the surface of the positive electrode current collector that was in contact with the positive electrode active material-containing layer. 3The above-mentioned surface analysis confirmed the presence of N and nitrate compounds. The above-mentioned surface analysis also confirmed that Li was present on a part of the surface of the positive electrode active material-containing layer. 3 It was confirmed that N and nitric acid compounds were present. On the other hand, in the secondary batteries of Comparative Examples 2 to 9, no nitrogen-containing substances were present on the surface of the positive electrode current collector or on the surface of the positive electrode active material-containing layer. (Examples 23 to 29) A thin nonaqueous electrolyte battery was fabricated in the same manner as described in Example 1 above, except for the nonaqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Table 6 below. In the nonaqueous solvent composition column in Table 6, the volume percentage of each nonaqueous solvent is shown in the upper row, and the volume ratio of the first solvent to the second solvent is shown in the lower row. The electrolyte column shows the type and concentration (M (mol / L)) of the electrolyte used. Meanwhile, the additive column shows the components other than the nonaqueous solvent in the nonaqueous electrolyte and their contents (wt%).

[0173] By carrying out the above-mentioned surface analysis on the secondary batteries of Examples 23 to 29, it was confirmed that a substance containing boron (B) and fluorine (F) was present on a part of the surface of the positive electrode current collector that was in contact with the positive electrode active material-containing layer. In addition, by this surface analysis, it was confirmed that a boron-containing compound was present on a part of the surface of the positive electrode active material-containing layer of Examples 23 to 29. <Confirmation test of discharge capacity and high current performance> The nonaqueous electrolyte batteries of the Examples and Comparative Examples were charged to 3.0 V at a constant current of 0.7 A at 25° C., and then discharged to 1.5 V at 0.7 A, and the discharge capacity was measured to obtain the discharge capacity at 25° C. Furthermore, as a high current performance test, the batteries were charged to 3.0 V at a constant current of 0.7 A at 25° C., and then discharged to 1.5 V at 7 A, and the discharge capacity was measured. The value of the 7 A discharge capacity when the 0.7 A discharge capacity is taken as 100% is shown in Tables 4 and 5 as the 25° C. 7 A capacity maintenance rate. <High temperature cycle test> A cycle test was carried out on the nonaqueous electrolyte batteries of the Examples and Comparative Examples by repeatedly charging them at a constant current of 0.7 A at 70° C. up to 3.0 V, and then discharging them at a constant current of 0.7 A down to 1.5 V. The number of cycles at which the discharge capacity in the cycle test reached 80% of the initial capacity is shown in Tables 4 and 5 as the cycle life at 70° C. <Low temperature performance test> The nonaqueous electrolyte batteries of the Examples and Comparative Examples were measured for discharge capacity at 0.7 A at −30° C. The discharge capacity at 0.7 A at −30° C., when the discharge capacity at 0.7 A at 25° C. is taken as 100%, is shown in Tables 4 and 5 as the −30° C. capacity maintenance rate.

[0174] [Table 1]

[0175] [Table 2]

[0176] [Table 3]

[0177] [Table 4]

[0178] [Table 5]

[0179] [Table 6]

[0180] [Table 7]

[0181] As is clear from Tables 1 to 5, the batteries of Examples 1 to 22 are superior in discharge capacity at a low temperature of -30°C, capacity retention rate at a large current discharge of 7 A, and cycle life at 70°C compared to the batteries of Comparative Examples 1 to 9. In particular, Examples 4, 9, 10, 11, 12, 13, 14, 17, and 18 exhibited excellent performance in all of discharge performance at -30°C, large current discharge performance at 7 A, and high temperature cycle life performance at 70°C. This is because the nonaqueous electrolyte used in each Example exhibits excellent low-temperature discharge performance and excellent high-temperature stability and life.

[0182] As is clear from Tables 6 and 7, the batteries of Examples 23 to 29 are superior in discharge capacity at a low temperature of -30°C, capacity retention rate at a large current discharge of 7A, and cycle life at 70°C compared to the batteries of Comparative Examples 1 to 9. In addition, when comparing Example 9 and Example 25, which have the same non-aqueous solvent composition, electrolyte, positive electrode active material, and negative electrode active material, the battery of Example 25 is superior in discharge capacity at a low temperature of -30°C, capacity retention rate at a large current discharge of 7A, and cycle life at 70°C compared to the battery of Example 9. The non-aqueous electrolyte of the battery of Example 25 contains a boron-containing compound and a fluorine-containing compound. Therefore, it is presumed that the substance (film) present on the surface of the positive electrode current collector is highly stable and has an excellent effect of inhibiting corrosion of the positive electrode current collector.

[0183] On the other hand, in the battery of Comparative Example 1, although nitrogen-containing substances were present on the surface of the positive electrode current collector, the viscosity of the non-aqueous electrolyte was high and the ion conductivity was poor, so that all of the -30°C discharge performance, the 7A large current discharge performance, and the 70°C high temperature cycle life performance were low. In addition, in the batteries of Comparative Examples 2-4 and 8, the ion dissociation of LiFSI was reduced, and the ion conductivity was reduced, so that all of the -30°C discharge performance, the 7A large current discharge performance, and the 70°C high temperature cycle life performance were low. On the other hand, in the batteries of Comparative Examples 5-7 and 9, neither nitrogen-containing substances nor substances containing any of the atoms of N, B, and F were formed on the surface of the positive electrode current collector. Therefore, the corrosion of the positive electrode current collector progressed, and all of the -30°C discharge performance, the 7A large current discharge performance, and the 70°C high temperature cycle life performance were low. The LiN(CF 3 SO 2 ) 2In the experiment, neither nitrogen-containing substances nor substances containing any of the atoms of N, B, and F were formed. As a result, the positive electrode current collector was corroded, and the cycle life was reduced.

[0184] According to at least one of the secondary batteries of the embodiments or examples described above, a nonaqueous electrolyte containing a first solvent consisting of at least one selected from the group consisting of EP, PP, and EB, a second solvent containing GBL, and an electrolyte containing LiFSI can be realized, thereby realizing a secondary battery having excellent large current performance, low temperature performance, and high temperature life performance.

[0185] Although some embodiments of the present invention have been described, these embodiments are presented as examples 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 spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0186] The following describes the embodiments of the invention. (1) A positive electrode and A negative electrode; A secondary battery comprising: a non-aqueous solvent containing a first solvent consisting of at least one selected from the group consisting of ethyl propionate, propyl propionate, and ethyl butyrate, and a second solvent containing gamma-butyrolactone; and a non-aqueous electrolyte containing an electrolyte containing lithium bisfluorosulfonylimide. (2) The secondary battery according to (1), wherein the non-aqueous electrolyte further contains at least one selected from the group consisting of a nitrogen-containing compound, a sulfur-containing compound, a boron-containing compound, a phosphorus-containing compound, and a fluorine-containing compound. (3) The secondary battery according to (1) or (2), wherein the non-aqueous electrolyte further contains at least one selected from the group consisting of 1,3-propane sultone, fluoroethylene carbonate, tris(trimethylsilyl)phosphate, and nitrates. (4) The secondary battery according to any one of (1) to (3), wherein the positive electrode includes a positive electrode current collector that contains at least one of aluminum and an aluminum alloy and has a nitrogen-containing material present on at least a portion of a surface thereof. (5) The secondary battery according to any one of (1) to (4), wherein the negative electrode contains a negative electrode active material containing at least one of a titanium-containing oxide and a niobium-containing oxide. (6) The secondary battery according to any one of (1) to (5), wherein the negative electrode contains a negative electrode active material including at least one selected from the group consisting of a lithium titanium-containing oxide, a titanium oxide, a niobium titanium-containing oxide, a niobium tungsten-containing oxide, and a niobium titanium molybdenum-containing oxide. (7) The negative electrode is Li 4 / 3+a Ti 5 / 3 O 4 (0≦a≦2) or Li c TiNb d O 7 The secondary battery according to any one of (1) to (6), comprising a negative electrode active material containing at least one of (0≦c≦5, 1≦d≦4). (8) A battery pack including the secondary battery according to any one of (1) to (7). (9) An external terminal for supplying electricity; Protection circuit and The battery pack according to (8) further comprising: (10) A battery comprising a plurality of the secondary batteries, The battery pack according to (8) or (9), wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. (11) A vehicle equipped with a battery pack according to any one of (8) to (10). (12) The vehicle according to claim 11, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy. [Explanation of symbols]

[0187] Reference Signs List 1...electrode group, 2...container (exterior member), 3...positive electrode, 3a...positive electrode current collector, 3b...positive electrode active material-containing layer, 4...negative electrode, 4a...negative electrode current collector, 4b...negative electrode active material-containing layer, 5...separator, 6...positive electrode lead, 7...negative electrode lead, 8...positive electrode conductive tab, 9...negative electrode conductive tab, 10...sealing plate, 11...insulating member, 12...exterior member, 13...negative electrode terminal, 14...positive electrode terminal, 200...battery pack, 100 1 ~100 5 ...secondary battery, 21...lead (bus bar), 300...battery pack, 100...unit cell, 200...battery assembly, 34...printed wiring board, 345...thermistor, 346...protection circuit, 350...external terminal for energization, 40...vehicle body, 300...battery pack, 400...vehicle, 41...vehicle power supply, 411...battery management device, 412...communication bus, 300a-c...battery packs, 301a-c...battery assembly monitoring device, 200a-c...battery assembly, 413...positive terminal, 414...negative terminal, 44...inverter, 45...driving motor, 43...external terminal, 42...vehicle ECU, L1, L2...connection line, W...driving wheel.

Claims

1. A positive electrode and A negative electrode; A secondary battery comprising: a non-aqueous solvent containing a first solvent consisting of at least one selected from the group consisting of ethyl propionate, propyl propionate, and ethyl butyrate, and a second solvent containing gamma-butyrolactone; and a non-aqueous electrolyte containing an electrolyte containing lithium bisfluorosulfonylimide.

2. 2. The secondary battery according to claim 1, wherein the non-aqueous electrolyte further comprises at least one selected from the group consisting of a nitrogen-containing compound, a sulfur-containing compound, a boron-containing compound, a phosphorus-containing compound, and a fluorine-containing compound.

3. 2. The secondary battery according to claim 1, wherein the non-aqueous electrolyte further contains at least one selected from the group consisting of 1,3-propane sultone, fluoroethylene carbonate, tris(trimethylsilyl)phosphate, nitrate, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate.

4. 2. The secondary battery according to claim 1, wherein the positive electrode comprises a positive electrode current collector that includes at least one of aluminum or an aluminum alloy and has nitrogen-containing material present on at least a portion of a surface thereof.

5. 2. The secondary battery according to claim 1, wherein the positive electrode comprises a positive electrode current collector that contains at least one of aluminum or an aluminum alloy and has a material containing at least one element selected from the group consisting of N, B, and F present on at least a portion of a surface thereof.

6. The secondary battery according to claim 1 , wherein the negative electrode contains a negative electrode active material including at least one of a titanium-containing oxide or a niobium-containing oxide.

7. 2. The secondary battery according to claim 1, wherein the negative electrode contains at least one negative electrode active material selected from the group consisting of lithium titanium-containing oxide, titanium oxide, niobium titanium-containing oxide, niobium tungsten-containing oxide, and niobium titanium molybdenum-containing oxide.

8. The negative electrode is Li 4 / 3+a Ti 5 / 3 O 4 (0≦a≦2) or Li c TiNb ｄ O 7 2. The secondary battery according to claim 1, comprising a negative electrode active material containing at least one of (0≦c≦5, 1≦d≦4).

9. A battery pack comprising the secondary battery according to any one of claims 1 to 8.

10. An external terminal for supplying electricity; Protection circuit and The battery pack of claim 9 further comprising:

11. A battery comprising a plurality of the secondary batteries, The battery pack according to claim 10 , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

12. A vehicle equipped with the battery pack according to claim 9.

13. The vehicle of claim 12, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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