Secondary battery, battery pack, and vehicle

Abstract

The embodiment of the invention relates to a secondary battery, a battery pack and a vehicle. The present invention addresses the problem of providing a secondary battery, a battery pack, and a vehicle having excellent high-current performance, low-temperature performance, and high-temperature life performance. According to one embodiment, a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided. The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte containing lithium bis (fluorosulfonyl) imide, and the non-aqueous solvent contains a first solvent comprising at least one selected from the group consisting of ethyl propionate, propyl propionate, and ethyl butyrate, and a second solvent containing gamma-butyrolactone.

Description

Technical Field

[0001] Embodiments of the present invention relate to a secondary battery, a battery pack, and a vehicle. Background Art

[0002] Non-aqueous electrolyte batteries using lithium metal, lithium alloy, lithium compound or carbonaceous material as negative electrode are expected to be high energy density batteries, and research and development are being promoted. So far, lithium ion batteries with positive electrodes containing LiCoO2 or LiMn2O4 as active materials and negative electrodes containing carbonaceous materials for embedding / de-embedding lithium ions have been widely used in portable devices.

[0003] On the other hand, when mounted on cars, trams and other vehicles, in order to meet the battery performance (e.g., storage performance, cycle performance, high output, etc.) in a high temperature environment (e.g., above 60°C), it is expected that the constituent materials of the positive and negative electrodes are materials with excellent chemical and electrochemical stability, strength, and corrosion resistance. In addition, in order to achieve high performance in cold areas, it is required to improve the battery performance (e.g., high current performance, long life performance) in a low temperature environment (e.g., -40°C). On the other hand, as a non-aqueous electrolyte, from the perspective of improving safety performance, the development of non-volatile and non-flammable electrolytes is being promoted, but due to the decrease in output characteristics, low temperature performance or long life performance, it has not yet been put into practical use.

[0004] The above problems have become obstacles to the use of lithium-ion batteries as a substitute for lead-acid batteries and mounted in the engine room of automobiles. In order to mount lithium-ion batteries in automobiles, it is desired to improve high-temperature durability and high-current performance. Summary of the invention

[0005] The problem to be solved by the present invention 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.

[0006] According to an embodiment, a secondary battery including a positive electrode, a negative electrode and a non-aqueous electrolyte is provided. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte including lithium bis(fluorosulfonyl)imide, wherein the non-aqueous solvent includes a first solvent formed of at least one selected from the group consisting of ethyl propionate, propyl propionate and ethyl butyrate and a second solvent including γ-butyrolactone.

[0007] In addition, according to an embodiment, a battery pack including the secondary battery of the embodiment is provided.

[0008] According to an embodiment, a vehicle including at least one of the secondary battery or the battery pack according to the embodiment is provided.

[0009] According to the secondary battery having the above configuration, it is possible 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a partially cut-away cross-sectional view of a secondary battery according to an embodiment.

[0011] Figure 2 About Figure 1 Side view of a battery.

[0012] Figure 3 This is a cross-sectional view of the secondary battery according to the embodiment cut along a direction perpendicular to the direction in which the terminal extends.

[0013] Figure 4 yes Figure 3 An enlarged cross-sectional view of section A.

[0014] Figure 5 It is a perspective view showing an example of a battery pack including a secondary battery according to an embodiment.

[0015] Figure 6 It is an exploded perspective view of the battery pack according to the embodiment.

[0016] Figure 7 Yes means Figure 6 Block diagram of the electrical circuit of the battery pack.

[0017] Figure 8 It is a schematic diagram showing an example of a vehicle equipped with the secondary battery according to the embodiment.

[0018] Fig. 9 It is a diagram schematically showing another example of the vehicle according to the embodiment.

[0019] (Explanation of Reference Numerals)

[0020] 1…electrode group, 2…container (exterior component), 3…positive electrode, 3a…positive electrode current collector, 3b…positive electrode active material layer, 4…negative electrode, 4a…negative electrode current collector, 4b…negative electrode active material 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 component, 12…exterior component, 13…negative electrode terminal, 14…positive electrode terminal, 200…battery group, 1001 to 1005…secondary battery, 21…lead (bus bar), 300…battery pack, 100…unit battery, 200… battery pack, 34…printed wiring board, 345…thermistor, 346…protection circuit, 350…external terminal for power supply, 40…vehicle body, 300…battery pack, 400…vehicle, 41…power source for vehicle, 411…battery management device, 412…communication bus, 300a~c…battery pack, 301a~c…battery pack monitoring device, 200a~c…battery pack, 413…positive terminal, 414…negative terminal, 44…inverter, 45…drive motor, 43…external terminal, 42…vehicle ECU, L1, L2…connecting wires, W…drive wheel. DETAILED DESCRIPTION

[0021] <First embodiment>

[0022] According to a first embodiment, a secondary battery including a positive electrode, a negative electrode and a non-aqueous electrolyte is provided. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte including lithium bis(fluorosulfonyl)imide (LiN(FSO2)2: LiFSI), wherein the non-aqueous solvent includes a first solvent formed by 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.

[0023] Research is being conducted to improve non-aqueous electrolytes to balance high current discharge performance, low temperature performance, and high temperature life performance. Non-aqueous electrolytes with high ion conductivity in low temperature regions tend to react with the positive electrode at high temperatures, making it difficult to obtain excellent life performance. Therefore, it is difficult to balance high current discharge performance, low temperature performance, and high temperature life performance with non-aqueous electrolytes with previous compositions.

[0024] When a secondary battery including a positive electrode having a positive electrode current collector containing at least one of aluminum or an aluminum alloy has a positive electrode potential of 4 V (vs. Li / Li +) or above, the positive electrode collector corrodes and dissolves, and the positive electrode active material layer is peeled off from the positive electrode collector. As a result, the charging and discharging of the secondary battery becomes difficult, and the life performance is reduced. As a result of in-depth research by the inventors of the present invention, it was first discovered that: as a non-aqueous electrolyte, by using a non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI), the non-aqueous solvent comprises a first solvent formed by at least one selected from the group consisting of ethyl propionate (EP), propyl propionate (PP) and ethyl butyrate (EB) and a second solvent containing γ-butyrolactone (GBL), the corrosion of the positive electrode collector can be suppressed, and a secondary battery with excellent high current performance, low temperature performance and high temperature life performance can be obtained. According to the secondary battery of the embodiment, excellent high current performance and durability performance can be achieved over a wide range of temperatures from low temperature (e.g., -70°C) to high temperature (e.g., 70°C). The detailed mechanism is not clear, but it is speculated as follows.

[0025] The non-aqueous electrolyte of the above composition can inhibit the corrosion of the positive electrode collector. LiFSI can be highly soluble in GBL as the second solvent and dissolve to a high concentration, thereby improving the ionic conductivity of the non-aqueous electrolyte, and improving the large current performance of the secondary battery, such as the large current discharge performance. In addition, LiFSI is chemically stable at high temperatures in the non-aqueous electrolysis of the above composition, thereby improving the life performance of the secondary battery at high temperatures. On the other hand, the first solvent can reduce the viscosity of the non-aqueous electrolyte, thereby improving the low temperature performance of the secondary battery. In addition, the first solvent can improve the electrochemical stability of the non-aqueous electrolyte at high voltage and high temperature. Therefore, the electrochemical stability of the non-aqueous electrolyte relative to the high-voltage positive electrode can be improved, and the life performance of the secondary battery that can be used in a high-temperature and high-voltage charging state can be improved.

[0026] Therefore, by dissolving LiFSI in a nonaqueous electrolyte in a nonaqueous mixed solvent containing a first solvent and a second solvent, a secondary battery having excellent large current performance, low temperature performance, and high temperature life performance can be provided.

[0027] Hereinafter, the nonaqueous electrolyte, the positive electrode, and the negative electrode will be described.

[0028] (Non-aqueous electrolyte)

[0029] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI), wherein the non-aqueous solvent includes a first solvent formed of at least one selected from the group consisting of ethyl propionate (EP), propyl propionate (PP) and ethyl butyrate (EB) and a second solvent containing gamma-butyrolactone (GBL). The electrolyte is dissolved in the non-aqueous solvent.

[0030] The first solvent is a non-aqueous solvent that has excellent low temperature performance due to its low viscosity and is electrochemically stable even at high voltage and high temperature. Propyl propionate and ethyl butyrate have low melting points and high flash points and belong to the second petroleum group. The first solvent substantially formed of at least one of propyl propionate or ethyl butyrate is easy to handle and can improve the mass production of secondary batteries.

[0031] The second solvent is a non-aqueous solvent containing γ-butyrolactone. LiFSI has high solubility in γ-butyrolactone and excellent chemical stability to γ-butyrolactone. The second solvent may be composed only of γ-butyrolactone, or may contain other non-aqueous solvents (hereinafter referred to as the third solvent) in addition to γ-butyrolactone. Examples of the third solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), dimethyl carbonate (DMC), and trimethyl phosphate (TMP). TMP has a fire extinguishing effect, so it is preferred that the electrolyte can be flame retardant by adding it. Propylene carbonate is stable to high voltage, so it can improve the stability of the non-aqueous electrolyte at high voltage. In addition, propylene carbonate can form a film on at least a portion of the surface containing the negative electrode active material layer, thereby suppressing the reaction of the negative electrode active material with the non-aqueous electrolyte, and the reaction of the conductive agent with the non-aqueous electrolyte. As a result, the generation of gas at high temperature can be suppressed. The amount of the third solvent can be more than 5% by volume and less than 30% by volume of the total non-aqueous mixed solvent. This can improve the cycle life performance of the secondary battery.

[0032] The mixing ratio of the first solvent and 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. Within this range, a secondary battery with excellent large current discharge performance, low temperature discharge performance and high temperature cycle performance can be achieved. The more preferred range of the volume ratio is 4:1 to 1:2. Examples of preferred compositions of non-aqueous mixed solvents are: GBL and EP; GBL and PP; GBL and EB; GBL, EP and PP; GBL, PP and EB; GBL, PC and EP; GBL, PC and PP; GBL, PC and EB; GBL, EP and TMP; GBL, PP and TMP.

[0033] 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 within this range, the non-aqueous electrolyte can have a high ionic conductivity from low temperature to high temperature region, thereby improving the high current discharge performance of the secondary battery. By increasing the concentration of LiFSI, the generation of nitrogen-containing substances from LiFSI can be promoted. On the other hand, if the concentration of LiFSI is reduced, the generation of nitrogen-containing substances from nitric acid compounds can be promoted while improving the ionic conductivity of the non-aqueous electrolyte. The preferred range of the concentration of LiFSI as an electrolyte is 0.8M or more and 3M or less. A further preferred range is 1M or more and 2M or less.

[0034] An electrolyte is a substance that is soluble in a non-aqueous solvent. The electrolyte may be substantially formed of LiFSI, but may also contain other electrolytes (hereinafter referred to as the second electrolyte) in addition to LiFSI. Examples of the second electrolyte include LiBF4 and LiN(CF3SO2)2. LiBF4 has high chemical stability to GBL and can form an aluminum fluoride (AlF3) layer on the surface of the positive electrode collector. The aluminum fluoride layer can inhibit the corrosion of the positive electrode collector without hindering the conduction of lithium ions in the positive electrode, thereby improving the high temperature life performance of the secondary battery. The concentration of the second electrolyte in the non-aqueous electrolyte can be greater than 0.1M and less than 0.5M.

[0035] 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. Thus, a film or layer can be formed on at least one electrode in the positive electrode or the negative electrode, 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 is preferably 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.

[0036] As an example of a nitrogen-containing compound, a nitrate can be cited. For example, a nitrate can be dissolved in a non-aqueous electrolyte to provide NO3 -Salt of ions. Examples of nitrates include LiNO3, NaNO3, and KNO3. The type of nitrate used can be one or more than two. Nitrates can form nitrogen-containing substances on at least a portion of the surface of the positive electrode collector even when the concentration of LiFSI in the non-aqueous electrolyte is low. LiNO3 is also preferred among nitrates. Even if the concentration of LiFSI in the non-aqueous electrolyte is increased in a manner that does not contain nitrates, nitrogen-containing substances can be formed on at least a portion of the surface of the positive electrode collector. The nitrogen-containing substance can exist on the surface of the positive electrode collector as a coating. The nitrogen-containing substance can inhibit the corrosion of the positive electrode collector at high potential and high temperature, thereby inhibiting the peeling of the positive electrode active material layer from the positive electrode collector. The nitrogen-containing substance may also exist on at least a portion of the surface of at least one of the positive electrode active material layer or the negative electrode active material layer. The nitrogen-containing substance may be a nitrogen-containing inorganic substance. Examples of nitrogen-containing inorganic substances include nitric acid compounds, metal nitrides such as Li3N, and the like. Metal nitrides such as Li3N have lithium ion conductivity, and thus can reduce the resistance of the film containing the nitrogen-containing substance. Therefore, the metal nitride can improve the large current performance. On the other hand, the nitric acid compound can inhibit the decomposition of the non-aqueous electrolyte. Nitrate can form a nitrogen-containing substance containing at least one of the nitric acid compound or the metal nitride. In addition, the nitrate can form the nitrogen-containing substance in a manner that does not affect the ionic conductivity of the non-aqueous electrolyte.

[0037] An example of a sulfur-containing compound is 1,3-propane sultone (PS). 1,3-Propane sultone can form a film containing S on at least a portion of the surface of the positive electrode active material layer, the negative electrode active material layer, or both. This can suppress the decomposition of the nonaqueous solvent and thus suppress gas generation at high temperatures.

[0038] As examples of boron-containing compounds, there can be cited lithium difluoro(oxalate)borate (LiBF2C2O4: LiDFOB), lithium bis(oxalate)borate (LiB(C2O4)2: LiBOB), lithium tetrafluoroborate (LiBF4), etc. When the positive electrode collector contains Al, LiDFOB and LiBF4 can form films containing boron (B), oxygen (O), fluorine (F) and aluminum (Al) on the surface of the positive electrode collector, respectively. As a result, regardless of whether the LiFSI concentration in the non-aqueous electrolyte is low or high, and even at high voltage or high temperature, the dissolution reaction caused by the corrosion of Al can be suppressed. The film preferably contains a substance having an Al-F bond, a BO bond and a BF bond. As a result, the charge and discharge cycle performance of the battery can be improved.

[0039] 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 setting the content to 0.1% by weight or more, a film containing B is generated on the surface of the positive electrode collector and dissolution caused by corrosion of the positive electrode collector can be suppressed. By setting the content to 5% by weight or less, the ion conductivity of the non-aqueous electrolyte can be improved.

[0040] 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 it can inhibit the reduction and decomposition of the non-aqueous electrolyte. As a result, the charge and discharge efficiency of the negative electrode can be improved, thereby improving the cycle life performance of the battery.

[0041] An example of a phosphorus-containing compound is tris(trimethylsilyl) phosphate (TMSP). TMSP can form a film containing P on at least a portion of the surface of the positive electrode active material layer, the negative electrode active material layer, or both. This can inhibit the decomposition of the nonaqueous solvent and thus inhibit gas generation at high temperatures.

[0042] As an example of a fluorine-containing compound, fluoroethylene carbonate (FEC) can be cited. FEC can form a film containing F on at least a portion of the surface of the positive electrode active material layer, the negative electrode active material layer, or both. Thus, the decomposition of the non-aqueous solvent can be suppressed, thereby suppressing the generation of gas at high temperature. In addition, the film containing F can suppress the reduction and decomposition of GBL of the non-aqueous solvent on the surface of the negative electrode active material, thereby improving the cycle life performance of the battery.

[0043] The form of the non-aqueous electrolyte is not particularly limited, and can 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 can be a substance composed of a liquid non-aqueous electrolyte and a polymer material, in other words, it can be a composite of a liquid non-aqueous electrolyte and a polymer material. As polymer materials, for example, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), etc. can be cited.

[0044] The non-aqueous electrolyte may contain a room-temperature molten salt formed of a non-volatile and non-flammable ionic liquid. The liquid non-aqueous electrolyte can improve the low-temperature performance of the secondary battery.

[0045] The following is an example of a method for forming a film or layer on at least one of the positive electrode or the negative electrode (referred to as the first method). 0.1 to 10 wt % of 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, and a secondary battery having the non-aqueous electrolyte, a positive electrode and a negative electrode is assembled, and a positive electrode potential of 4 V (vs. Li / Li) is charged at a temperature of 45 to 80 ° C. + ) or more, and thereby a film or layer can be formed on the electrode. The film or layer contains at least one element (atom) selected from the group consisting of N, S, B, P and F.

[0046] In addition, the positive electrode and the negative electrode used in assembling the secondary battery can be produced, for example, by the following method. The positive electrode is produced, for example, by suspending the positive electrode active material, the conductive agent and the binder in an appropriate solvent, applying the suspension to the positive electrode collector, drying, and pressing. On the other hand, the negative electrode is produced, for example, by suspending the negative electrode active material, the conductive agent and the binder in an appropriate solvent, applying the suspension to the collector, drying, and pressing.

[0047] (negative electrode)

[0048] 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 surfaces of the negative electrode current collector and contains a negative electrode active material. The negative electrode active material-containing layer may also contain a binder, a conductive agent, or both.

[0049] The negative electrode active material may be, for example, a material that intercalates and deintercalates Li (e.g., lithium ions). Examples of materials that intercalate and deintercalate Li (e.g., lithium ions) include carbon materials, metal oxides, metal sulfides, Li alloys, and the like. The type of negative electrode active material used may be one or more than two.

[0050] Examples of carbon materials include graphite, carbon fiber, coke, and non-graphitizable carbon. Examples of metal sulfides include titanium sulfide, molybdenum sulfide, and iron sulfide. Examples of Li alloys include alloys containing Li and at least one element selected from the group consisting of Si, Al, Sn, Zn, and Pb.

[0051] The metal oxide can be, for example, 0.5V (vs. Li / Li + ) and above 3.0V(vs.Li / Li +) or less. Examples of the above metal oxides include titanium-containing oxides and niobium-containing oxides. The insertion and extraction potential of lithium ions in the negative electrode containing a negative electrode active material containing at least one of titanium-containing oxides and niobium-containing oxides is 0.5 to 3.0 V (vs. Li / Li + ), so that a film that is stable at high temperatures can be formed on the surface of the negative electrode active material layer. Therefore, the reduction and decomposition of the non-aqueous electrolyte can be suppressed, so that a non-aqueous electrolyte secondary battery with excellent life performance under high temperature environment can be obtained. The more preferred negative electrode potential range is 0.7 (vs. Li / Li + ) and above 2V(vs.Li / Li + )the following.

[0052] Examples of titanium-containing oxides include lithium-containing titanium oxides and titanium oxides. Examples of niobium-containing oxides include niobium-containing titanium oxides, niobium-containing tungsten oxides, and niobium-containing titanium-molybdenum oxides.

[0053] Examples of lithium-containing titanium oxides include lithium-containing titanium oxides having a spinel structure (e.g., general formula Li 4 / 3+ a Ti 5 / 3 O4 (0≤a≤2)), lithium-containing titanium oxides having a ramsdellite structure (e.g., general formula Li 2+a Ti3O7(0≤a≤1)), Li 1+b Lithium-containing titanium oxide represented by Ti2O4 (0≤b≤1), Li 1.1+b Ti 1.8 Lithium-containing titanium oxide represented by O4 (0≤b≤1), Li 1.07+b Ti 1.86 A lithium-containing titanium oxide represented by O4 (0≤b≤1), a lithium-containing titanium composite oxide containing at least one element selected from the group consisting of Nb, Mo, W, P, V, Sn, Cu, Ni and Fe, and the like.

[0054] In addition, examples of lithium-containing titanium oxides include 2+a A d Ti 6-b B b O 14-c (A is one or more elements selected from Na, K, Mg, Ca, and Sr, B is a metal element other than Ti, 0≤a≤5, 0≤b≤6, 0≤c≤0.6, 0≤d≤3) lithium-containing titanium composite oxide. 2+a A d Ti 6-b B b O 14-c The crystal structure has space group Cmca.

[0055] In addition, as another example of lithium-containing titanium oxide, an orthorhombic titanium oxide can be cited. As an example of an orthorhombic titanium oxide, a lithium-containing titanium oxide can be cited. 2+a M I 2-b Ti 6-c M II d O 14+σ Here, M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. II At least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni and Al. In the composition formula, each subscript is 0≤a≤6, 0≤b<2, 0≤c<6, 0≤d<6, -0.5≤σ≤0.5. As a specific example of the orthorhombic titanium-containing composite oxide, Li 2+a Na2Ti6O 14 (0≤a≤6).

[0056] Examples of titanium oxides include titanium oxides represented by the general formula LiaTiO2 (0≤a≤2). In this case, the composition formula before charging is TiO2. Examples of titanium oxides include titanium oxides with a monoclinic structure (bronze structure (B)), titanium oxides with a rutile structure, titanium oxides with anatase structure, and the like. TiO2(B) with a monoclinic structure (bronze structure (B)) is preferred. In addition, low-crystalline TiO2(B) with a heat treatment temperature of 300 to 600°C is also preferred.

[0057] Examples of the niobium-containing oxide include niobium oxide, niobium-containing titanium oxide, niobium-containing tungsten oxide, and niobium-containing titanium molybdenum oxide.

[0058] Examples of niobium oxides include Nb2O5.

[0059] Examples of niobium-containing titanium oxides include monoclinic niobium-containing titanium oxides, Ti2Nb2O9, Ti2Nb 10 O 29 、TiNb 14 O 37 、TiNb 24 O 62 Substituted niobium-titanium composite oxides in which at least a portion of Nb, 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 oxide may contain one substituting element or two or more substituting elements.

[0060] Examples of monoclinic niobium-containing titanium oxides include those having the general formula Li c TnB d O7 (0≤c≤5, 1≤d≤4). A more preferred composition is TiNb2O7.

[0061] Examples of monoclinic niobium-containing titanium oxides include Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ A compound represented by . 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. Each subscript in the composition formula is 0≤x≤5, 0≤y<1, 0≤z<2, -0.3≤δ≤0.3.

[0062] As another example of monoclinic niobium-containing titanium oxide, Ti 1-y M3 y+z Nb 2-z O 7-δ Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta and Mo. Each subscript in the composition formula is 0≤y<1, 0≤z<2, -0.3≤δ≤0.3.

[0063] Examples of tungsten oxides containing niobium include Nb 14 W3O 44 , Nb 16 W5W 55 , Nb 18 W8O 69 wait.

[0064] 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 (preferably, the subscripts a, b, c and d are in the range of 0≤a≤b+4+3c, 0.3≤b≤1.6, 0.3≤c<1.6 and 0≤d<0.4, respectively) a tetragonal titanium-niobium-molybdenum composite oxide represented by the general formula Li a M b Nb c O dIt means that M is any 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 is a composite oxide with 0≤a≤b+2+3c, 0≤b≤1.4, 0≤c≤0.5 and 2.33≤d / (1+b+c)≤2.50.

[0065] Contains Li 4 / 3+a Ti 5 / 3 O4(0≤a≤2) or Li c TnB d The negative electrode active material of at least one of O7 (0≤c≤5, 1≤d≤4) is electrochemically and chemically stable to the non-aqueous electrolyte because it can quickly embed and de-embed lithium ions in the active material, and thus has excellent high current discharge performance, fast charging performance and cycle life performance. In addition, the above-mentioned negative electrode active material is stable to the first solvent and the second solvent even at high temperature, and thus has excellent durable life performance.

[0066] The negative electrode active material particles may be in the form of primary particles or secondary particles formed by aggregation of primary particles. In addition, primary particles and secondary particles may exist in a mixed state.

[0067] The average particle size of the primary particles of the negative electrode active material is preferably set to a range of 0.05 to 1 μm. This can improve the high current performance. In addition, good performance can be obtained regardless of whether the particle shape is granular or fibrous. 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 also improve the cycle life performance.

[0068] The negative electrode active material preferably has an average particle size of 2 μm or less and a specific surface area of ​​2 to 50 m2 as measured by the N2 adsorption BET method. 2 This can further improve the affinity of the negative electrode with the non-aqueous electrolyte and the electrochemical stability.

[0069] The porosity of the negative electrode (excluding the current collector) is preferably in the range of 20 to 50%. This allows a negative electrode having excellent affinity with the non-aqueous electrolyte and a high density to be obtained. The porosity is more preferably in the range of 25 to 40%.

[0070] The negative electrode current collector varies depending on the type of negative electrode active material. When lithium alloy or carbon material is used as the negative electrode active material, copper foil can be used as the negative electrode current collector. +) when inserting a metal oxide separated from lithium ions at a potential of 100 ppm, the negative electrode current collector can contain at least one of aluminum or an aluminum alloy. A more preferred negative electrode current collector is aluminum foil or 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 less than 100 ppm.

[0071] The thickness of the negative electrode current collector is 20 μm or less, and more preferably 15 μm or less.

[0072] The negative electrode active material layer can contain a conductive agent. As a conductive agent, for example, carbon nanotubes, acetylene black, carbon black, coke (preferably with a heat treatment temperature of 800°C to 2000°C and an average particle size of 10 μm or less), carbon fiber, graphite, metal compound powders such as TiO, TiC, and TiN, metal powders such as Al, Ni, Cu, and Fe, etc. can be cited. The type of conductive agent can be one or more. By using carbon fibers with a fiber diameter of less than 1 μm, the electrode resistance is reduced and the cycle life performance is improved.

[0073] 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, cellulose nanofiber, etc. The type of binder may be one or more.

[0074] The mixing ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95 wt % of the negative electrode active material, 1 to 18 wt % of the conductive agent and 2 to 7 wt % of the binder.

[0075] The negative electrode is produced, for example, by suspending a negative electrode active material, a conductive agent, and a binder in an appropriate solvent, applying the suspension to a current collector, drying the suspension, and performing pressing (for example, hot pressing).

[0076] (positive electrode)

[0077] The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer that is supported on or in contact with one surface (one main surface) or both surfaces of the current collector and contains a positive electrode active material. The positive electrode active material-containing layer may also contain a binder, a conductive agent, or both.

[0078] Examples of positive electrode active materials include Li x M y O2 (0<x≤1, 0<y≤1, M is, for example, Mn), Li x M 2y O4 (0<x≤1, 0<y≤1, M is Mn, for example), lithium phosphorus oxide with olivine structure (for example, Lix M y PO4 (M is at least one element selected from Mn, Ni, Co, Fe, 0<x≤1.1, 0.8≤y≤1.1), Li x FePO4(0<x≤1.1), Li x Fe 1- y Mn y PO4(0<x≤1.1, 0≤y≤1), Li x CoPO4(0<x≤1.1), Li x MnPO4 (0<x≤1.1)), lithium nickel cobalt composite oxide (such as Li x Ni 1-a Co a O2, 0<x≤1, 0<a≤1), lithium cobalt composite oxide (such as Li x CoO2, 0<x≤1), lithium nickel manganese cobalt composite oxide (such as Li x Ni 1-a-b Mn a Co b O2, 0<x≤1, 0<1-ab<1, 0<a<1, 0<b<1), lithium manganese cobalt composite oxide (such as Li x Mn 1-a Co a O2, 0<x≤1, 0<a<1), spinel lithium manganese nickel composite oxide (such as Li x Mn 2-a Ni a O4, 0<x≤1, 0<a<2), fluorinated iron sulfate with hydroxyapatite structure (such as Li x M y SO4F (0<x≤1, 0<y≤1, M is at least one of Fe or Mn), Li x Fe 1-a Mn a SO4F (0<x≤1, 0<a≤1), etc. The type of the positive electrode active material may be one or two or more.

[0079] The positive electrode active material can obtain a high voltage of 4 V or more. The 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.

[0080] A positive electrode containing at least one of lithium cobalt composite oxide, lithium nickel manganese cobalt composite oxide, lithium manganese composite oxide, and lithium phosphorus oxide with 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 generated on the surface of the positive electrode is suppressed, and the resistance of the positive electrode becomes smaller. In addition, the stability in a high-temperature environment becomes higher, thereby improving the storage performance. A more preferred positive electrode active material is Li x CoO2、Li x Ni 1-a-b Mn a Co b O2、Li x M 2y O4 (0<x≤1, 0<y≤1, M contains Mn), Li x Fe 1-y Mn y PO4 forms a positive electrode active material.

[0081] The positive electrode active material particles may be in the form of primary particles or secondary particles formed by aggregation of primary particles. In addition, primary particles and secondary particles may exist in a mixed state.

[0082] Preferably, 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. Thus, the oxidation decomposition reaction of the non-aqueous electrolyte under high temperature environment can be suppressed, thereby suppressing the resistance increase. Therefore, the high temperature life performance can be improved.

[0083] Each element of Mg, Al, Ti, Nb, Sn, Zr, Ba, B, and N can be attached to the surface of the positive electrode active material particles in the form of metal oxide particles, phosphorus oxide particles, and nitride particles with a particle size of 0.001 to 1 μm, but the surface can also be coated with a metal oxide layer, a phosphorus oxide layer, a nitride layer, or a fluoride layer. Alternatively, it can also be dissolved near the surface of the positive electrode active material particles. As metal oxides, MgO, Al2O3, SnO, ZrO2, TiO2, BaO, B2O3, etc. can be mentioned. As phosphorus oxides, AlPO4, Mg3(PO4)2, Sn3(PO4)2, etc. can be mentioned. As nitrides, metal nitrides such as Li3N can be mentioned. As fluorides, metal fluorides such as LiF can be mentioned. In addition, as C, carbon particles with an average particle size of less than 1 μm are preferably 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 weight percent of the positive electrode active material. By setting it to this range, the reaction between the positive electrode and the non-aqueous electrolyte under a high temperature environment can be suppressed, and the rise of the interface resistance between the positive electrode and the non-aqueous electrolyte can be suppressed. Therefore, the output performance and life performance of the secondary battery can be improved.

[0084] A film or layer containing at least one of a fluoride or a nitrogen-containing substance may also be formed on at least a portion of the surface of the positive electrode active material layer. Thus, the oxidative decomposition of the non-aqueous electrolyte can be suppressed, thereby suppressing the generation of gas at high temperatures. Examples of fluorides include LiF, etc. In addition, examples of nitrogen-containing substances include Li3N, etc. The film (layer) of the above composition can be formed, for example, by a non-aqueous electrolyte containing 0.5 to 10 weight % of LiNO3.

[0085] The positive electrode current collector may contain at least one of aluminum and an aluminum alloy. For example, aluminum foil or aluminum alloy foil is used as the positive electrode current collector.

[0086] A nitrogen-containing substance may also exist on at least a portion of the surface of the positive electrode collector. This is because it is possible to suppress corrosion of the positive electrode collector when the positive electrode operating voltage becomes a high voltage of 4V or more at high temperature. By suppressing corrosion, the charge and discharge cycle proceeds smoothly, thereby improving the life performance. Examples of nitrogen-containing substances include nitric acid compounds, metal nitrides such as Li3N, and the like. The details of the nitrogen-containing substance are as described in relation to the non-aqueous electrolyte.

[0087] The nitrogen-containing substance is preferably present in 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. This can enhance the corrosion inhibition effect.

[0088] The following is an example of a method for forming a nitrogen-containing substance (referred to as the second method). 0.1 to 10 wt% of lithium nitrate (LiNO3) is added to a non-aqueous electrolyte, and a secondary battery having the non-aqueous electrolyte, a positive electrode, and a negative electrode is assembled. The battery is charged at a temperature of 45 to 80°C to a positive electrode potential of 4 V (vs. Li / Li + ) or more, thereby aging the battery to cover part or all of the surface of the positive electrode collector with the nitrogen-containing substance. Alternatively, the concentration of LiFSI in the non-aqueous electrolyte may be set to 1.5 M or more, and after assembling a secondary battery having the non-aqueous electrolyte, the positive electrode and the negative electrode, the battery charged to a positive electrode potential of 4 V (vs. Li / Li) at a temperature of 45 to 80 ° C may be aged. + ) or more batteries are aged. In this case, part or all of the surface of the positive electrode collector is covered with nitrogen-containing substances, and fluoride can also exist on the surface of the positive electrode collector. Lithium nitrate can form nitrogen-containing substances on the surface of the positive electrode collector without increasing the viscosity of the non-aqueous electrolyte and maintaining the ion conductivity of the non-aqueous electrolyte within a practical range.

[0089] In addition, the positive electrode and the negative electrode used in assembling the secondary battery can be produced by the following method, for example. The positive electrode is produced by, for example, suspending the positive electrode active material, the conductive agent and the binder in an appropriate solvent, applying the suspension to the positive electrode collector, drying, and pressing. On the other hand, the negative electrode is produced by, for example, suspending the negative electrode active material, the conductive agent and the binder in an appropriate solvent, applying the suspension to the collector, drying, and pressing.

[0090] It is preferred that a substance containing at least one element (atom) selected from the group consisting of N, B and F exists on at least a portion of the surface of the positive electrode collector. As the form that the substance can take, for example, a film-like substance and a layered substance can be cited. The substance can be a compound containing at least one element (atom) selected from the group consisting of N, B and F. The substance containing B has excellent stability. Therefore, in the case where the positive electrode collector contains at least one of aluminum or an aluminum alloy, the effect of suppressing the corrosion of the positive electrode collector when the positive electrode operating voltage becomes a high voltage of more than 4V at high temperature can be improved. In addition, in the case where the positive electrode collector contains at least one of aluminum or an aluminum alloy, F can form Al and fluoride, so that the substance containing F can stably exist on the surface of the positive electrode collector. As a result, the effect of suppressing the corrosion of the positive electrode collector can be improved.

[0091] As an example of a 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 portion of the surface of the positive electrode collector (referred to as the third method), the same method as described in the first method of forming a film or layer on at least one electrode of the positive electrode or the negative electrode can be cited. In addition, the method for forming a substance containing N (the second method) may also be the same method as the method for forming a nitrogen-containing substance.

[0092] The thickness of the positive electrode current collector can be 20 μm or less, and more preferably 15 μm or less.

[0093] The positive electrode active material-containing layer may also contain a conductive agent. Examples of the conductive agent include acetylene black, carbon black, and graphite. The type of the conductive agent may be one or more.

[0094] The positive electrode active material-containing layer may also contain a binder. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and acrylic materials. The type of the binder may be one or more.

[0095] The mixing ratio of the positive electrode active material, the conductive agent, and the binder is preferably in the range of 80 to 95 wt % of the positive electrode active material, 3 to 19 wt % of the conductive agent, and 1 to 7 wt % of the binder.

[0096] The specific surface area of ​​the positive electrode active material layer obtained by the BET method is preferably 0.1 to 2 m 2 / g range.

[0097] The positive electrode active material containing layer may be porous.

[0098] The positive electrode is produced, for example, by suspending a positive electrode active material, a conductive agent, and a binder in an appropriate solvent, applying the suspension to a positive electrode current collector, drying the suspension, and pressing the suspension.

[0099] The secondary battery of the embodiment may also include a separator and an outer component in addition to a non-aqueous electrolyte, a negative electrode and a positive electrode. The negative electrode, the positive electrode and the separator may constitute an electrode group. The non-aqueous electrolyte may be retained in the electrode group. The form of the electrode group is not particularly limited, and may be, for example, a stacked type, a winding type, etc.

[0100] (Diaphragm)

[0101] The separator is disposed between the positive electrode and the negative electrode. A portion of the separator may be opposed to or in contact with only the positive electrode, or may be opposed to or in contact with only the negative electrode.

[0102] Examples of the separator include synthetic resin nonwoven fabrics, polyethylene porous films, polypropylene porous films, cellulose nonwoven fabrics, and the like.

[0103] At least a part of the surface of the separator may be covered with a layer containing inorganic particles such as aluminum oxide.

[0104] (Exterior parts)

[0105] The outer casing contains at least a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode and the negative electrode may be contained in the outer casing in the form of an electrode group with a separator disposed therebetween.

[0106] As the exterior member, a metal container or a laminated film container can be used.

[0107] As the metal container, a metal can made of aluminum, aluminum alloy, iron, stainless steel, etc. and a square or cylindrical metal container can be used. The metal container may also have a lid. In addition, the plate thickness of the container is preferably 0.5 mm or less, and a further preferred range is 0.3 mm or less.

[0108] As the laminated film, for example, a multilayer film formed by covering an aluminum foil with a resin film can be cited. As the resin, a polymer such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. In addition, the thickness of the laminated film is preferably 0.2 mm or less. The purity of the aluminum foil is preferably 99.5% or more.

[0109] The metal can formed 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 formed of an aluminum alloy is significantly increased, and the wall thickness of the can can be reduced. As a result, a thin, light, high-output, and excellent heat dissipation battery can be realized.

[0110] Next, a method for confirming nitrogen-containing substances and the like will be described.

[0111] First, a method for removing an electrode (positive electrode or negative electrode) from a battery will be described.

[0112] The secondary battery was disassembled in an argon atmosphere, and the positive electrode collector, positive electrode or negative electrode to be measured were taken out. The measured object was washed with a solvent composed of dimethyl carbonate in an argon atmosphere, vacuum dried at 100° C., and then measured by the method described below.

[0113] <Confirmation method of nitrogen-containing substances>

[0114] Whether the nitrogen-containing compound exists on the surface of the positive electrode current collector or the positive electrode active material-containing layer is confirmed by X-ray photoelectron spectroscopy (XPS) under the conditions described below.

[0115] As an XPS device, Quantera SXM manufactured by ULVAC-PHI or a device having equivalent functions can be used. The excitation X-ray source uses a single crystal spectroscopic Al-Kα line (1486.6 eV). The X-ray output is 4 kW (13 kV × 310 mA), the photoelectron detection angle is 45°, and the analysis area is about 4 mm × 0.2 mm. The scan is performed at 0.10 eV / step.

[0116] For example, the presence of Li3N can be confirmed by detecting the spectrum from the Li-N bond (399 eV) in the state analysis of the surface (N1s) of the positive electrode collector (such as aluminum foil). On the other hand, nitric acid compounds can be detected by detecting the spectrum from NO3 in the state analysis of the surface (N1s) of the positive electrode collector (such as aluminum foil). - The presence of nitric acid compounds was confirmed by analyzing the spectrum of the nitric acid bond (407 eV).

[0117] Whether or not a fluorine-containing substance or a boron-containing substance exists on the surface of the positive electrode current collector can be confirmed by the method described below.

[0118] <Confirmation method of fluorine-containing substances>

[0119] Using the same experimental method and measuring apparatus as those for identifying nitrogen-containing substances, for example, AlF3 from the Al-F bond (686.3 eV) in the XPS pattern of F1s or LiF from the Li-F bond (685.01 eV) can be identified as fluorine-containing substances in the state analysis of the positive electrode collector.

[0120] <Method for confirming boron-containing substances>

[0121] Using the same experimental method and measuring apparatus as the method for identifying nitrogen-containing substances, for example, B2O3 or AlBO3 derived from the BO bond (193.1 eV) in the XPS pattern of B1s can be identified as a boron-containing substance in the state analysis of the positive electrode current collector.

[0122] <Measurement of average particle size of active material particles>

[0123] 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 having an equivalent function). About 0.1 g of sample, surfactant and 1 to 2 mL of distilled water are added to a beaker and stirred thoroughly, then poured into a stirring water tank, and the photometric distribution is measured 64 times at 2 second intervals to obtain the average particle size obtained from the obtained particle size distribution data.

[0124] <Measurement of BET specific surface area of ​​active material and electrode based on N2 adsorption>

[0125] When measuring the BET specific surface area of ​​the active material based on N2 adsorption, 1 g of active material powder is prepared as a sample. When measuring the BET specific surface area of ​​the electrode based on N2 adsorption, the electrode is cut into 2×2 cm 2 Two pieces of the same size were used as samples. A BET specific surface area measurement apparatus manufactured by Yuasa Ionics was used, and nitrogen was used as the adsorption gas.

[0126] <Method for measuring the porosity of the negative electrode>

[0127] The porosity of the negative electrode is calculated by comparing the volume of the negative electrode active material layer with the volume of the negative electrode active material layer when the porosity is 0%, and considering the increase in the volume of the negative electrode active material layer when the porosity is 0% as the pore volume. In addition, when the negative electrode active material layer is formed on both sides of the collector, the volume of the negative electrode active material layer is the value obtained by adding up the volumes of the negative electrode active material layers on both sides.

[0128] <Positive electrode active material>

[0129] The crystal structure and elemental composition of the positive electrode active material can be confirmed by powder X-ray diffraction (XRD: X-ray diffraction) measurement and inductively coupled plasma (ICP: Inductively Coupled Plasma) emission spectroscopy.

[0130] <Negative electrode active material>

[0131] The crystal structure and elemental composition of the negative electrode active material can be confirmed by powder X-ray diffraction (XRD: X-ray diffraction) measurement and inductively coupled plasma (ICP: Inductively Coupled Plasma) emission spectroscopy.

[0132] Reference Figure 1 to Figure 4 An example of the secondary battery according to the embodiment will be described.

[0133] Figure 1 and Figure 2 An example of a secondary battery using a metal container is shown.

[0134] 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 3 containing a positive electrode active material layer and a negative electrode 4 containing a negative electrode active material layer, and they are wound in a spiral shape to form a flat shape. The separator 5 covers the surface of the positive electrode active material layer or the negative electrode active material layer. Figure 2As shown, a plurality of strip-shaped positive electrode leads 6 are electrically connected to the end of the positive electrode 3 located at the end surface of the electrode group 1. In addition, a plurality of strip-shaped negative electrode leads 7 are electrically connected to the end of the negative electrode 4 located at the end surface. The plurality of positive electrode leads 6 are electrically connected to the positive electrode conductive tab 8 in a bundled state. The positive electrode lead 6 and the positive electrode conductive tab 8 constitute a positive terminal. In addition, the negative electrode lead 7 is connected to the negative electrode conductive tab 9 in a bundled state. The negative electrode lead 7 and the negative electrode conductive tab 9 constitute a negative terminal. A metal sealing plate 10 is fixed to the opening of the metal container 2 by welding or the like. The positive electrode conductive tab 8 and the negative electrode conductive tab 9 are respectively led out to the outside from the extraction holes provided in the sealing plate 10. In order to avoid short circuits caused by contact with the positive electrode conductive tab 8 and the negative electrode conductive tab 9, the inner peripheral surface of each extraction hole of the sealing plate 10 is covered with an insulating member 11.

[0135] Figure 3 and Figure 4 An example of a secondary battery using a laminate film exterior member is shown in FIG.

[0136] like Figure 3 and Figure 4 As shown, the flat wound electrode group 1 is contained in a bag-shaped outer member 12, and the outer member 12 is made of a laminated film in which a metal layer is sandwiched between two resin films. The flat wound electrode group 1 is formed by the following steps: a layered product formed by stacking the negative electrode 4, the separator 15, the positive electrode 3, and the separator 15 in order from the outside is wound into a spiral shape, and the layered product is stamped. The outermost negative electrode 4 has a Figure 4 The negative electrode 4 is formed with a negative electrode active material layer 4b containing a negative electrode active material on one side of the inner surface of the negative electrode collector 4a, and the other negative electrode 4 is formed with a negative electrode active material layer 4b formed on both sides of the negative electrode collector 4a. The positive electrode 3 is formed with a positive electrode active material layer 3b formed on both sides of the positive electrode collector 3a.

[0137] Near the outer peripheral end of the wound electrode group 1, the negative terminal 13 is connected to the negative electrode collector 4a of the outermost negative electrode 4, and the positive terminal 14 is connected to the positive electrode collector 3a of the inner positive electrode 3. The above-mentioned negative terminal 13 and positive terminal 14 extend outward from the opening of the bag-like outer packaging member 12. The wound electrode group 1 is sealed by heat-sealing the opening of the bag-like outer packaging member 12. When heat-sealing, the negative terminal 13 and the positive terminal 14 are clamped by the bag-like outer packaging member 12 at the opening.

[0138] The secondary battery of the embodiment described above comprises a non-aqueous solvent and a non-aqueous electrolyte containing LiFSI, wherein the non-aqueous solvent comprises a first solvent formed by at least one selected from the group consisting of EP, PP and EB and a second solvent containing GBL, thereby being able to suppress corrosion of the positive electrode collector and realizing a secondary battery with excellent high current performance, low temperature performance and high temperature life performance.

[0139] <Second embodiment>

[0140] The assembled battery of the second embodiment includes the secondary batteries of a plurality of embodiments.

[0141] Examples of assembled batteries include an assembled battery including a plurality of unit cells electrically connected in series and / or in parallel as constituent units, an assembled battery including a first unit formed of a plurality of unit cells electrically connected in series, or a second unit formed of a plurality of unit cells electrically connected in parallel, etc. The assembled battery may include at least one of these constituent units.

[0142] Examples of forms in which multiple secondary batteries are electrically connected in series and / or in parallel include forms in which multiple batteries each having an outer casing are electrically connected in series and / or in parallel, and forms in which multiple electrode groups or bipolar electrode bodies housed in a common housing are electrically connected in series and / or in parallel. A specific example of the former is a bus bar made of metal (e.g., aluminum, nickel, copper) that connects the positive terminal and the negative terminal of multiple secondary batteries. A specific example of the latter is to house multiple electrode groups or bipolar electrode bodies in an electrochemically insulated state through a partition in a housing, and electrically connect them in series. In the case of a secondary battery, the number of batteries electrically connected in series is set to a range of 5 to 7, thereby improving the voltage interchangeability with a lead-acid battery. In order to further improve the voltage interchangeability with a lead-acid battery, it is preferably configured to have 5 or 6 unit batteries connected in series.

[0143] The case for housing the assembled battery may be a metal can or a plastic container made of aluminum alloy, iron, stainless steel, etc. The thickness of the container is preferably 0.5 mm or more.

[0144] Reference Figure 5 An example of a battery pack will be described. Figure 5 The battery pack 200 shown has a plurality of Figure 1The rectangular secondary batteries 1001 to 1005 shown are used as unit batteries. The positive conductive tab 8 of the battery 1001 and the negative conductive tab 9 of the battery 1002 located next to it are electrically connected through a lead wire or a bus bar 21. In addition, the positive conductive tab 8 of the battery 1002 and the negative conductive tab 9 of the battery 1003 located next to it are electrically connected through a lead wire or a bus bar 21. In this way, the batteries 1001 to 1005 are connected in series.

[0145] Since the assembled battery of the embodiment described above includes the secondary battery of the embodiment, it is possible to realize an assembled battery having excellent large current performance, low temperature performance, and high temperature life performance.

[0146] <Third Embodiment>

[0147] The battery pack involved in the third embodiment can include one or more secondary batteries (single batteries) involved in the embodiment. Multiple secondary batteries can also be electrically connected in series, in parallel, or in a combination of series and parallel to form a battery pack. The battery pack involved in the embodiment can also include multiple battery packs.

[0148] The battery pack involved in the embodiment can further include a protection circuit. The protection circuit has the function of controlling the charge and discharge of the secondary battery. Alternatively, a circuit contained in a device (e.g., electronic equipment, automobile, etc.) that uses the battery pack as a power source can also be used as a protection circuit for the battery pack.

[0149] In addition, the battery pack involved in the embodiment can further include an external terminal for power supply. The external terminal for power supply is used to output the current from the secondary battery to the outside, and to input the current to the secondary battery. In other words, when the battery pack is used as a power source, the current is supplied to the outside through the external terminal for power supply. In addition, when the battery pack is charged, the charging current (including the regenerative energy of the power of a vehicle such as a car) is supplied to the battery pack through the external terminal for power supply.

[0150] Next, an example of a battery pack according to an embodiment will be described with reference to the drawings.

[0151] Figure 6 It is an exploded perspective view schematically showing an example of a battery pack according to an embodiment. Figure 7 Yes means Figure 6 A block diagram of an example of an electrical circuit of a battery pack is shown.

[0152] Figure 6 and Figure 7 The battery pack 300 shown includes a storage container 31 , a cover 32 , a protective sheet 33 , the battery module 200 , a printed wiring board 34 , wirings 35 , and an insulating plate (not shown).

[0153] Figure 6 The storage container 31 shown is a bottomed square container having a rectangular bottom surface. The storage container 31 is configured to be able to accommodate a protective sheet 33, a battery pack 200, a printed wiring substrate 34, and wiring 35. The cover 32 has a rectangular shape. The storage container 31 is covered by the cover 32 to accommodate the battery pack 200 and the like. Although not shown in the figure, an opening or a connection terminal for connecting to an external device or the like is provided in the storage container 31 and the cover 32.

[0154] The assembled battery 200 includes a plurality of unit cells 100 , a positive electrode lead 22 , a negative electrode lead 23 , and an adhesive tape 24 .

[0155] At least one of the plurality of cells 100 is a secondary battery according to the embodiment. Figure 7 The plurality of cells 100 may be electrically connected in parallel, or in a combination of series connection and parallel connection. If the plurality of cells 100 are connected in parallel, the battery capacity increases compared to the case of series connection.

[0156] The adhesive tape 24 fastens the plurality of cells 100. Instead of the adhesive tape 24, a heat shrink tape may be used to fix the plurality of cells 100. In this case, the protective sheets 33 are arranged on both sides of the battery pack 200, and the heat shrink tape is wrapped around the protective sheets 33, and then the heat shrink tape is heat-shrunk to bundle the plurality of cells 100.

[0157] One end of the positive electrode lead 22 is connected to the assembled battery 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 assembled battery 200. One end of the negative electrode lead 23 is electrically connected to the negative electrode of one or more cells 100.

[0158] The printed wiring substrate 34 is provided along one short side of the inner side surface of the storage container 31. The printed wiring substrate 34 includes a positive electrode side connector 342, a negative electrode side connector 343, a thermistor 345, a protection circuit 346, wirings 342a and 343a, an external terminal 350 for power supply, a positive electrode side wiring (positive side wiring) 348a, and a negative electrode side wiring (negative side wiring) 348b. One main surface of the printed wiring substrate 34 faces one side surface of the battery pack 200. An insulating plate (not shown) is interposed between the printed wiring substrate 34 and the battery pack 200.

[0159] The other end 22 a of the positive electrode lead 22 is electrically connected to the positive electrode connector 342 . The other end 23 a of the negative electrode lead 23 is electrically connected to the negative electrode connector 343 .

[0160] 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 sends the detection signal to the protection circuit 346 .

[0161] The external terminals 350 for power supply are fixed to the other main surface of the printed wiring board 34. The external terminals 350 for power supply are electrically connected to a device existing outside the battery pack 300. The external terminals 350 for power supply include a positive terminal 352 and a negative terminal 353.

[0162] The protection circuit 346 is fixed to the other main surface of the printed wiring substrate 34. The protection circuit 346 is connected to the positive terminal 352 via the positive wiring 348a. The protection circuit 346 is connected to the negative terminal 353 via the negative wiring 348b. In addition, the protection circuit 346 is electrically connected to the positive side connector 342 via the wiring 342a. The protection circuit 346 is electrically connected to the negative side connector 343 via the wiring 343a. Furthermore, the protection circuit 346 is electrically connected to each of the plurality of cells 100 and the wiring 35.

[0163] The protective sheet 33 is disposed on both inner side surfaces in the longitudinal direction of the storage container 31 and on the inner side surface in the transverse direction facing the printed wiring board 34 via the battery module 200. The protective sheet 33 is made of, for example, resin or rubber.

[0164] The protection circuit 346 controls the charge and discharge of the plurality of cells 100. In addition, based on a detection signal sent from the thermistor 345 or a detection signal sent from each cell 100 or the assembled battery 200, the protection circuit 346 cuts off the electrical connection between the protection circuit 346 and the external terminal 350 (positive terminal 352, negative terminal 353) for powering an external device.

[0165] As the detection signal sent from the thermistor 345, for example, a signal for detecting that the temperature of the single cell 100 is above a predetermined temperature can be cited. As the detection signal sent from each single cell 100 or the assembled battery 200, for example, a signal for detecting overcharge, overdischarge, and overcurrent of the single cell 100 can be cited. When detecting overcharge and the like for each single 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 serving as a reference electrode is inserted into each single cell 100.

[0166] Alternatively, as the protection circuit 346 , a circuit included in a device (eg, electronic equipment, automobile, etc.) that uses the battery pack 300 as a power source may be used.

[0167] In addition, the battery pack 300 has the external terminal 350 for power supply as described above. Therefore, the battery pack 300 can output the current from the assembled battery 200 to the external device via the external terminal 350 for power supply, and input the current from the external device to the assembled battery 200. 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 power supply. In addition, when the battery pack 300 is charged, the charging current from the external device is supplied to the battery pack 300 through the external terminal 350 for power supply. When the battery pack 300 is used as a vehicle-mounted battery, the regenerative energy of the power of the vehicle can be used as the charging current from the external device.

[0168] In addition, the battery pack 300 may also include a plurality of battery assemblies 200. In this case, the plurality of battery assemblies 200 may be connected in series, in parallel, or in a combination of series connection and parallel connection. In addition, the printed wiring substrate 34 and the wiring 35 may be omitted. In this case, the positive electrode side lead 22 and the negative electrode side lead 23 may be used as the positive side terminal and the negative side terminal of the external terminal for power supply, respectively.

[0169] Such a battery pack is used, for example, for applications requiring excellent cycle performance when a large current is taken out. Specifically, the battery pack is used, for example, as a power source for electronic equipment, a stationary battery, and a vehicle-mounted battery for various vehicles (including a railway vehicle battery). As an electronic device, for example, a digital camera can be cited. The battery pack is particularly suitable for use as a vehicle-mounted battery.

[0170] The battery pack according to the embodiment includes the secondary battery according to the embodiment or the assembled battery according to the embodiment. Therefore, it is possible to realize a battery pack having excellent large current performance, low temperature performance, and high temperature life performance.

[0171] <Fourth embodiment>

[0172] According to a fourth embodiment, a vehicle is provided. The vehicle is equipped with the battery pack according to the embodiment.

[0173] In the vehicle according to the embodiment, the battery pack recovers regenerative energy of the vehicle's power, for example. The vehicle may further include a mechanism (eg, a regenerator) that converts the vehicle's kinetic energy into regenerative energy.

[0174] Examples of the vehicle according to the embodiment include a two-wheeled or four-wheeled hybrid electric vehicle, a two-wheeled or four-wheeled electric vehicle, an assist bicycle, and a railway vehicle.

[0175] The mounting position of the battery pack of the vehicle according to the embodiment is not particularly limited. For example, when the battery pack is mounted on a car, the battery pack can be mounted in the engine room of the vehicle, behind the vehicle body, or under the seat.

[0176] The vehicle involved in the embodiment may also be equipped with multiple battery packs. In this case, the batteries contained in each battery pack may be electrically connected to each other in series, in parallel, or in a combination of series connection and parallel connection. For example, when each battery pack includes a battery pack, the battery packs may be electrically connected to each other in series, in parallel, or in a combination of series connection and parallel connection. Alternatively, when each battery pack includes a single battery, the batteries may be electrically connected to each other in series, in parallel, or in a combination of series connection and parallel connection.

[0177] Next, an example of a vehicle according to the embodiment will be described with reference to the drawings.

[0178] Figure 8 This is a partial perspective view schematically showing an example of a vehicle according to the embodiment.

[0179] Figure 8 The vehicle 400 shown includes a vehicle body 40 and a battery pack 300 according to the third embodiment. Figure 8 In the example shown, vehicle 400 is a four-wheeled automobile.

[0180] The vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the batteries (eg, single batteries or battery packs) included in the battery pack 300 may be connected in series, in parallel, or in a combination of series connection and parallel connection.

[0181] exist Figure 8 , the battery pack 300 is shown in the figure as an example in which the battery pack 300 is mounted in the engine room located in front of the vehicle body 40. As described above, the battery pack 300 may be mounted, for example, behind the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 400. In addition, the battery pack 300 can recover the regenerative energy of the power of the vehicle 400.

[0182] Next, refer to Fig. 9 An embodiment of a vehicle according to an embodiment will be described.

[0183] Fig. 9 This is a diagram schematically showing an example of a control system related to an electrical system of a vehicle according to an embodiment. Fig. 9 The illustrated vehicle 400 is an electric vehicle.

[0184] Fig. 9 The vehicle 400 shown includes: a vehicle body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42 as a higher-level control device of the vehicle power supply 41, an external terminal (a terminal for connecting to an external power supply) 43, an inverter 44 and a drive motor 45.

[0185] The vehicle 400 has a vehicle power supply 41 mounted in, for example, an engine room, a rear part of a vehicle body, or under a seat. Fig. 9 In the illustrated vehicle 400 , a mounting location of a vehicle power source 41 is schematically shown.

[0186] The vehicle power source 41 includes: a plurality of (eg, three) battery packs 300 a , 300 b , and 300 c ; a battery management unit (BMU) 411 ; and a communication bus 412 .

[0187] The battery pack 300a includes a battery pack 200a and a battery pack monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes a battery pack 200b and a battery pack monitoring device 301b. The battery pack 300c includes a battery pack 200c and a battery pack monitoring device 301c. The battery packs 300a to 300c are the same battery packs as the above-mentioned battery pack 300, and the battery packs 200a to 200c are the same battery packs as the above-mentioned battery pack 200. The battery packs 200a to 200c are electrically connected in series. The battery packs 300a, 300b and 300c can be removed independently and can be exchanged with other battery packs 300.

[0188] Each of the assembled batteries 200a to 200c includes a plurality of cells connected in series. At least one of the plurality of cells is a secondary battery of the embodiment. Each of the assembled batteries 200a to 200c is charged and discharged through a positive electrode terminal 413 and a negative electrode terminal 414.

[0189] The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c to collect information on the voltage and temperature of each cell 100 included in the assembled batteries 200a to 200c included in the vehicle power supply 41. Thus, the battery management device 411 collects information on maintenance of the vehicle power supply 41.

[0190] The battery management device 411 and the assembled battery monitoring devices 301a to 301c are connected via a communication bus 412. The communication bus 412 is a communication bus formed based on the CAN (Control Area Network) standard, for example, by sharing a set of communication lines with multiple nodes (the battery management device 411 and one or more assembled battery monitoring devices 301a to 301c).

[0191] The assembled battery monitoring devices 301a to 301c measure the voltage and temperature of each cell constituting the assembled batteries 200a to 200c based on a command generated by communication from the battery management device 411. However, the temperature may be measured at only a few locations in one assembled battery, and the temperature of all cells need not be measured.

[0192] The vehicle power supply 41 may further include an electromagnetic contactor (eg, Fig. 9 The switch device 415 is shown in the figure. The switch device 415 includes: a pre-charge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged; and a main switch (not shown) that is turned on when the output from the assembled batteries 200a to 200c is supplied to the load. The pre-charge switch and the main switch each include a relay circuit (not shown) that is switched on or off according to a signal provided to a coil arranged near the switching element. The electromagnetic contactor such as the switch device 415 is controlled based on a control signal from the vehicle ECU 42 that controls the operation of the battery management device 411 or the entire vehicle 400.

[0193] The inverter 44 converts the input DC voltage into a three-phase AC high voltage for motor driving. 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 vehicle ECU 42 for controlling the operation of the battery management device 411 or the entire vehicle. By controlling the inverter 44, the output voltage from the inverter 44 is adjusted.

[0194] The drive motor 45 is rotated by the electric power supplied from the inverter 44. The driving force generated by the rotation of the drive motor 45 is transmitted to the axle and the drive wheels W via a differential gear unit, for example.

[0195] In addition, although not shown, the vehicle 400 is provided with a regenerative braking mechanism. The regenerative braking mechanism rotates the drive motor 45 when braking the vehicle 400, converting 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.

[0196] One terminal of the 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 the negative input terminal 417 of the inverter 44. In the connection line L1, 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.

[0197] One terminal of the connection line L2 is connected to the positive terminal 413 of the vehicle power supply 41. The other terminal of the connection line L2 is connected to the positive input terminal 418 of the inverter 44. A switch device 415 is provided between the positive terminal 413 and the positive input terminal 418 in the connection line L2.

[0198] The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power source, for example.

[0199] The vehicle ECU 42 coordinates and controls the vehicle power supply 41, the switch device 415, the inverter 44, etc. together with other management devices and control devices including the battery management device 411 in response to the operation input of the driver, etc. The vehicle 400 is managed as a whole by controlling the output of power from the vehicle power supply 41 and the charging of the vehicle power supply 41 through the coordinated control of the vehicle ECU 42, etc. The battery management device 411 and the vehicle ECU 42 transfer data related to the maintenance of the vehicle power supply 41, such as the remaining capacity of the vehicle power supply 41, through the communication line.

[0200] The vehicle according to the embodiment is equipped with the battery pack according to the embodiment, so that a vehicle having excellent running performance in a wide temperature range from low temperature to high temperature can be realized.

[0201] Example

[0202] 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.

[0203] (Example 1)

[0204] The positive electrode active material used was a layered lithium nickel cobalt manganese composite oxide (LiNi 0.8 Co 0.1 Mn 0.1O2) particles. The positive electrode active material is mixed with graphite powder as a conductive agent, which is 8% by weight relative to the total positive electrode active material layer, and PVdF as a binder, which is 5% by weight relative to the total positive electrode active material layer, and dispersed in N-methylpyrrolidone (NMP) solvent to prepare a slurry. The slurry is applied to both sides of an aluminum alloy foil (purity 99%) with a thickness of 15 μm, dried, and pressed to produce a single-sided coating of 12.8 mg / cm 2 The thickness of the single-sided positive electrode active material layer is 43 μm, and the electrode density is 3.0 g / cm 3 The BET specific surface area of ​​the positive electrode active material layer is 0.5 m 2 / g.

[0205] In addition, the average particle size was 0.6 μm and the BET specific surface area was 8 m 2 / g, Li embedding potential is 1.55V (vs.Li / Li + ) spinel lithium titanate (Li4Ti5O 12 ) powder, average particle size 0.4 μm, BET specific surface area 50 m 2 / g of coke powder, acetylene black powder and PVdF as a binder were dispersed in N-methylpyrrolidone (NMP) solvent in a weight ratio of 90:6:2:2 to prepare a slurry. The obtained slurry was applied to an aluminum alloy foil (purity 99.3%) with a thickness of 15μm, dried, and pressed to produce a single-sided coating of 13mg / cm 2 The thickness of the negative electrode active material layer on one side is 59 μm, and the electrode density is 2.2 g / cm 3 The negative electrode has a porosity of 35% excluding the current collector. In addition, the BET specific surface area (surface area per 1g of the negative electrode active material layer) of the negative electrode active material layer is 10m 2 / g.

[0206] A diaphragm formed of a polyethylene porous film with a thickness of 20 μm is overlapped and covered on the positive electrode. The positive electrode covered by the diaphragm is overlapped on the negative electrode so that the positive electrode active material layer is opposite to the negative electrode active material layer through the diaphragm, and they are wound into a spiral to produce an electrode group. The electrode group is pressed and formed into a flat shape. The electrode group is stored in a container formed by a thin metal can formed of an aluminum alloy (Al purity 99%) with a thickness of 0.25 mm.

[0207] As a non-aqueous electrolyte, a first solvent formed of EP and a second solvent formed 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 bis(FSO2)2 was dissolved in the obtained mixed non-aqueous solvent as an electrolyte. A liquid non-aqueous electrolyte (non-aqueous electrolyte solution) was prepared by adding 1 wt% of LiNO3 and 1 wt% of PS as additives. The non-aqueous electrolyte was injected into the electrode group in the container to produce the above-mentioned Figure 1 The structure shown is a thin non-aqueous electrolyte secondary battery with a thickness of 4 mm, a width of 30 mm, and a height of 60 mm.

[0208] The prepared non-aqueous electrolyte battery was charged to 3.0 V at 0.7 A at 60°C before the charge and discharge test, so that the positive electrode potential was 4 V (vs. Li / Li + ) or higher. Then, a high temperature aging treatment at 60° C. for 24 hours was performed to obtain a non-aqueous electrolyte secondary battery.

[0209] The obtained secondary battery was confirmed by surface analysis using the above-mentioned X-ray photoelectron spectroscopy (XPS) to confirm the presence of Li3N and nitric acid compounds on a portion of the surface of the positive electrode collector that was in contact with the positive electrode active material layer. In addition, by the same surface analysis, it was confirmed that Li3N and nitric acid compounds were present on a portion of the surface containing the positive electrode active material layer. Li3N comes from the Li-N bond (399 eV). On the other hand, the nitric acid compound comes from NO3 - bond (407eV).

[0210] (Examples 2 to 22)

[0211] Except for the non-aqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Tables 1 to 3 below, a thin non-aqueous electrolyte battery was produced by the same operation as described in Example 1 above. In the non-aqueous solvent composition column shown in Tables 1 to 3, the upper layer represents the volume % of each non-aqueous solvent, and the lower layer represents the volume ratio of the first solvent to the second solvent. The electrolyte column represents the type and concentration (M (mol / L)) of the electrolyte used. On the other hand, the additive column represents the components in the non-aqueous electrolyte other than the non-aqueous solvent and their content (weight %).

[0212] For the secondary batteries of Examples 2 to 5, 8 to 13, 16 to 19, and 21, the surface analysis above confirmed the presence of Li3N and nitric acid compounds on a portion of the surface of the positive electrode collector in contact with the positive electrode active material layer. In addition, the surface analysis above confirmed the presence of Li3N and nitric acid compounds on a portion of the surface of the positive electrode active material layer.

[0213] On the other hand, for the secondary batteries of Examples 6, 7, 14, 15, and 22, the above-mentioned surface analysis confirmed the presence of nitrogen-containing compounds on a portion of the surface of the positive electrode collector that was in contact with the positive electrode active material layer. In addition, the above-mentioned surface analysis confirmed the presence of nitrogen-containing compounds on a portion of the surface containing the positive electrode active material layer. For the secondary battery of Example 20, the presence of fluoride and nitrogen-containing compounds on a portion of the surface of the positive electrode collector that was in contact with the positive electrode active material layer and a portion of the surface containing the positive electrode active material layer was confirmed.

[0214] The details of the positive and negative electrode active materials used in the examples are described below.

[0215] TiNb2O7 particles have a monoclinic structure, an average particle size of 1 μm, and a BET specific surface area of ​​3 m 2 / g, Li embedding potential is 1~2V (vs.Li / Li + ).

[0216] TiO2(B) particles have a monoclinic structure, an average particle size of 10 μm, and a BET specific surface area of ​​10 m 2 / g, Li embedding potential is 1~2V (vs.Li / Li + ).

[0217] Nb 16 W5W 55 The average particle size is 1 μm and the BET specific surface area is 3 m 2 / g, Li insertion potential is 0.8~2.2V (vs.Li / Li + ).

[0218] LiNi 0.5 Co 0.2 Mn 0.3 The O2 particles have a layered structure and the average particle size is 3 μm.

[0219] LiNi 0.5 Co 0.3 Mn 0.2 The O2 particles have a layered structure and the average particle size is 3 μm.

[0220] (Comparative Examples 1 to 9)

[0221] A thin nonaqueous electrolyte battery was produced in the same manner as in Example 1 except for the nonaqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Table 3. In addition, LiN(CF3SO2)2 is lithium bis(trifluoromethylsulfonyl)imide.

[0222] In the secondary battery of Comparative Example 1, the above-mentioned surface analysis confirmed the presence of Li3N and nitric acid compounds on a portion of the surface of the positive electrode collector that was in contact with the positive electrode active material layer. In addition, the above-mentioned surface analysis confirmed the presence of Li3N and nitric acid compounds on a portion of the surface of the positive electrode active material layer. On the other hand, regarding the secondary batteries of Comparative Examples 2 to 9, no nitrogen-containing substances were present on either the surface of the positive electrode collector or the surface of the positive electrode active material layer.

[0223] (Examples 23 to 29)

[0224] Except for the nonaqueous solvent composition, electrolyte, negative electrode active material, positive electrode active material, and additives shown in Table 6 below, a thin nonaqueous electrolyte battery was produced by the same operation as described in Example 1 above. In the nonaqueous solvent composition column shown in Table 6, the upper layer represents the volume % of each nonaqueous solvent, and the lower layer represents the volume ratio of the first solvent and the second solvent. The electrolyte column represents the type and concentration (M (mol / L)) of the electrolyte used. On the other hand, the additive column represents the components other than the nonaqueous solvent in the nonaqueous electrolyte and their content (weight %).

[0225] By performing 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) existed on a portion of the surface in contact with the positive electrode active material layer on the surface of the positive electrode collector. In addition, by this surface analysis, it was confirmed that a boron-containing compound existed on a portion of the surface of the positive electrode active material layer of Examples 23 to 29.

[0226] <Confirmation test of discharge capacity and high current performance>

[0227] The discharge capacity of the non-aqueous electrolyte battery of the embodiment and the comparative example was measured when the battery was 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 at 25° C. was obtained. In addition, as a large current performance test, the discharge capacity was measured when the battery was 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. The value of the 7A discharge capacity when the 0.7A discharge capacity was set to 100% is shown in Tables 4, 5, and 7 as the 25° C. 7A capacity retention rate.

[0228] <High temperature cycle test>

[0229] The following cycle test was performed: the non-aqueous electrolyte batteries of the examples and comparative examples were charged to 3.0 V at 70°C at a constant current of 0.7 A, and then repeatedly discharged at a constant current of 0.7 A 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, 5, and 7 as the cycle life at 70°C.

[0230] <Low temperature performance test>

[0231] The discharge capacity of the nonaqueous electrolyte batteries of Examples and Comparative Examples was measured when discharged at 0.7 A at -30°C. The values ​​of the 0.7 A discharge capacity at -30°C when the discharge capacity at 25°C at 0.7 A was set to 100% are shown in Tables 4, 5, and 7 as -30°C capacity retention rates.

[0232]

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239] According to Tables 1 to 5, the batteries of Examples 1 to 22 are superior to the batteries of Comparative Examples 1 to 9 in discharge capacity at low temperature of -30°C, capacity retention rate at high current discharge of 7A, and cycle life at 70°C. In particular, Examples 4, 9, 10, 11, 12, 13, 14, 17, and 18 all have excellent performance in terms of -30°C discharge performance, 7A high current discharge performance, and 70°C high temperature cycle life performance. This is because the non-aqueous electrolyte used in each example has excellent low temperature discharge performance, and excellent high temperature stability and life.

[0240] According to Tables 6 and 7, the batteries of Examples 23 to 29 are superior to the batteries of Comparative Examples 1 to 9 in terms of discharge capacity at a low temperature of -30°C, capacity retention rate at a high current discharge of 7A, and cycle life at 70°C. In addition, if Example 9 and Example 25 are compared, in which the non-aqueous solvent composition, electrolyte, positive electrode active material, and negative electrode active material are of the same type, respectively, the battery of Example 25 is superior to the battery of Example 9 in terms of discharge capacity at a low temperature of -30°C, capacity retention rate at a high current discharge of 7A, and cycle life at 70°C. 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 collector is highly stable, and the corrosion inhibition effect of the positive electrode collector is excellent.

[0241] On the other hand, for the battery of Comparative Example 1, although the nitrogen-containing substance exists on the surface of the positive electrode collector, the viscosity of the non-aqueous electrolyte is high, which makes the ion conductivity poor, so the -30°C discharge performance, 7A large current discharge performance, and 70°C high temperature cycle life performance are all low. In addition, for the batteries of Comparative Examples 2 to 4 and 8, the ion dissociation of LiFSI is reduced, which reduces the ion conductivity, so the -30°C discharge performance, 7A large current discharge performance, and 70°C high temperature cycle life performance are all low. On the other hand, for the batteries of Comparative Examples 5 to 7 and 9, no nitrogen-containing substance is formed on the surface of the positive electrode collector, nor is a substance containing any of N, B, and F atoms formed. Therefore, the corrosion of the positive electrode collector is aggravated, and the -30°C discharge performance, 7A large current discharge performance, and 70°C high temperature cycle life performance are all low. LiN (CF3SO2) 2 used in Comparative Example 9 does not form a nitrogen-containing substance, nor does it form a substance containing any of N, B, and F atoms. As a result, the positive electrode collector is corroded, and the cycle life is reduced.

[0242] According to at least one embodiment or example of the secondary battery described above, since it includes a non-aqueous electrolyte, the non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte containing LiFSI, and the non-aqueous solvent includes a first solvent formed by at least one selected from the group consisting of EP, PP and EB and a second solvent containing GBL, it is possible to realize a secondary battery with excellent high current performance, low temperature performance and high temperature life performance.

[0243] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are included in the invention described in the claims and the scope of their equivalents.

[0244] The above-mentioned embodiments can be summarized as the following technical solutions.

[0245] Technical Solution 1

[0246] A secondary battery comprising:

[0247] positive electrode;

[0248] a negative electrode; and

[0249] A non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte containing lithium bis(fluorosulfonyl)imide, wherein the non-aqueous solvent comprises 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 γ-butyrolactone.

[0250] Technical Solution 2

[0251] According to the secondary battery described in claim 1,

[0252] The nonaqueous electrolyte further includes at least one selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, boron-containing compounds, phosphorus-containing compounds, and fluorine-containing compounds.

[0253] Technical Solution 3

[0254] The secondary battery according to claim 1 or 2, wherein:

[0255] The non-aqueous electrolyte further includes at least one selected from the group consisting of 1,3-propane sultone, fluoroethylene carbonate, tris(trimethylsilyl)phosphate, and nitrate.

[0256] Technical Solution 4

[0257] The secondary battery according to any one of claims 1 to 3, wherein:

[0258] The positive electrode includes a positive electrode current collector. The positive electrode current collector contains at least one of aluminum or an aluminum alloy and has a nitrogen-containing substance present on at least a portion of the surface.

[0259] Technical Solution 5

[0260] The secondary battery according to any one of claims 1 to 4, wherein

[0261] The negative electrode contains a negative electrode active material including at least one of a titanium-containing oxide and a niobium-containing oxide.

[0262] Technical Solution 6

[0263] The secondary battery according to any one of claims 1 to 5, wherein

[0264] The negative electrode contains a negative electrode active material including at least one selected from the group consisting of lithium-containing titanium oxides, titanium oxides, niobium-containing titanium oxides, niobium-containing tungsten oxides, and niobium-containing titanium-molybdenum oxides.

[0265] Technical Solution 7

[0266] The secondary battery according to any one of claims 1 to 6, wherein:

[0267] The negative electrode contains Li 4 / 3+a Ti 5 / 3 O4(0≤a≤2) or Li c TnB d A negative electrode active material of at least one of O7 (0≤c≤5, 1≤d≤4).

[0268] Technical Solution 8

[0269] A battery pack comprises the secondary battery described in any one of technical solutions 1 to 7.

[0270] Technical Solution 9

[0271] According to the battery pack described in technical solution 8, it further comprises:

[0272] External terminals for electrical connection; and

[0273] Protection circuit.

[0274] Technical Solution 10

[0275] The battery pack according to claim 8 or 9 comprises a plurality of the above-mentioned secondary batteries.

[0276] The secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0277] Technical Solution 11

[0278] A vehicle is equipped with the battery pack described in any one of claims 8 to 10.

[0279] Technical Solution 12

[0280] According to the vehicle described in technical solution 11, it includes a mechanism for converting the kinetic energy of the above-mentioned vehicle into regenerative energy.

Claims

1. A secondary battery comprising: positive electrode; a negative electrode; and A non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte containing lithium bis(fluorosulfonyl)imide, wherein the non-aqueous solvent comprises 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 γ-butyrolactone.

2. The secondary battery according to claim 1, wherein The nonaqueous electrolyte further includes 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 claim 1, wherein The nonaqueous electrolyte further includes 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. The secondary battery according to claim 1, wherein The positive electrode includes a positive electrode current collector. The positive electrode current collector includes at least one of aluminum or an aluminum alloy and has a nitrogen-containing substance on at least a portion of the surface.

5. The secondary battery according to claim 1, wherein The positive electrode includes a positive electrode current collector including at least one of aluminum or an aluminum alloy, and a substance containing at least one element selected from the group consisting of N, B, and F is present on at least a portion of the surface of the positive electrode current collector.

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 and a niobium-containing oxide.

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

8. The secondary battery according to claim 1, wherein The negative electrode contains Li 4 / 3+a Ti 5 / 3 O4 or Li c TnB d The negative electrode active material is at least one of O7, 0≤a≤2, 0≤c≤5, 1≤d≤4. 9 . A battery pack comprising the secondary battery according to claim 1 .

10. The battery pack according to claim 9, further comprising: External terminals for electrical connection; and Protection circuit.

11. The battery pack according to claim 10, comprising a plurality of the secondary batteries, 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, comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

Images