Secondary battery and power consuming device

Abstract

The present application provides a secondary battery and a power consuming device. The secondary battery includes a positive electrode piece, a negative electrode piece, a separator, and an electrolyte. The positive electrode piece includes a positive electrode current collector, and a positive electrode active material layer and an inorganic coating layer are provided on the surface of the positive electrode current collector. The electrolyte includes an additive, and the additive includes at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, and 1,2,3-tris(2-oxoethoxy)propane. The mass per unit area of ​​the inorganic coating layer is expressed as Ag / m2. 2 and the mass percentage of the additive relative to the mass of the electrolyte is B%, A and B satisfy 0.01≦B / A≦5. By selecting the additive and adjusting B / A within the above range, it is advantageous to improve the high-temperature safety characteristics at high voltage of the secondary battery.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application filed with the China Patent Office on March 31, 2023, bearing application number 202310340241.X and entitled "Secondary Battery and Power Consumption Device," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of energy storage devices, and in particular to secondary batteries and power consuming devices. [Background technology]

[0003] In recent years, secondary batteries such as lithium ion batteries have been widely used in the fields of smartphones, tablets, smart wear, power tools, and electric vehicles.

[0004] As secondary batteries are widely used, market demands for the energy density and usage environment of secondary batteries, such as high-temperature safety characteristics of secondary batteries at high voltages (e.g., voltages of 4.7 V or higher), are increasing. Therefore, how to improve the high-temperature safety characteristics of secondary batteries at high voltages has become an urgent issue. Summary of the Invention

[0005] SUMMARY OF THE DISCLOSURE The present application aims to provide a secondary battery and a power consuming device for improving the high-temperature safety characteristics of the secondary battery at high voltages.

[0006] The detailed technical solutions are as follows:

[0007] In a first aspect of the present application, there is provided a secondary battery comprising a positive electrode piece, a negative electrode piece, a separator, and an electrolyte, the positive electrode piece comprising a positive electrode current collector, and a positive electrode active material layer and an inorganic coating layer provided on a surface of the positive electrode current collector, the electrolyte containing an additive, the additive containing at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, and 1,2,3-tris(2-oxoethoxy)propane, and a mass per unit area of ​​the inorganic coating layer of at least one of Ag g / m 2 and the mass percentage of the additive relative to the mass of the electrolyte is B%, A and B satisfy 0.01≦B / A≦5. By adopting the above-mentioned structure of the positive electrode piece, selecting the above-mentioned electrolyte additive, and adjusting B / A within the above-mentioned range, it is advantageous to reduce the side reaction between the positive electrode piece and the electrolyte, thereby improving the high-temperature safety characteristics of the secondary battery. It is also advantageous to improve the film formation quality of the positive electrode electrolyte interface (CEI) film and the negative electrode electrolyte interface (SEI) film, and to improve the permeability and flame retardancy of the electrolyte, thereby improving the thermal stability and overcharge characteristics of the secondary battery. On the other hand, it is advantageous to enhance the protective effect of the inorganic coating layer on the positive electrode piece, to reduce the risk of short circuit occurrence in the secondary battery, and further to improve the high-temperature safety characteristics of the secondary battery at high voltage.

[0008] In some embodiments of the present application, A satisfies 1≦A≦20, which is advantageous to reduce the risk of short circuit occurrence in the secondary battery, and can further reduce the loss of energy density of the secondary battery.

[0009] In some embodiments of the present application, B satisfies 0.01≦B≦10, which is advantageous to improve the thermal stability and overcharge characteristics of the secondary battery, and can further reduce the kinetic loss of the secondary battery.

[0010] In some embodiments of the present application, the inorganic coating layer is provided on at least one surface of the positive electrode current collector, and when the length of the inorganic coating layer in the longitudinal direction of the positive electrode piece is W mm, the W satisfies 5≦W≦300. By setting the length of the inorganic coating layer provided on at least one surface of the positive electrode current collector to W mm, the protective effect of the inorganic coating layer on the positive electrode piece can be further enhanced and the risk of short circuit occurrence in the secondary battery can be reduced, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0011] In some embodiments of the present application, the inorganic coating layer is provided on two surfaces of the positive electrode current collector, and when the length of the inorganic coating layer on one surface of the positive electrode current collector in the length direction of the positive electrode piece is W1 mm ​​and the length of the inorganic coating layer on the other surface of the positive electrode current collector is W2 mm, the W1 satisfies 5≦W1≦35, and the W2 satisfies 30≦W2≦300. By providing inorganic coating layers with lengths W1 mm ​​and W2 mm on both sides of the current collector, the protective effect of the inorganic coating layer on the positive electrode piece can be further enhanced and the risk of short circuit occurrence in the secondary battery can be reduced, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0012] In some embodiments of the present application, when the thickness of the inorganic coating layer in the thickness direction of the positive electrode piece is H μm, the H satisfies 1≦H≦20, which is advantageous for further enhancing the protective effect of the inorganic coating layer on the positive electrode piece, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0013] In some embodiments of the present application, the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece is 0.1% to 20%, which is advantageous in further enhancing the protective effect of the inorganic coating layer on the positive electrode piece and reducing the risk of short circuit occurrence in the secondary battery, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0014] In some embodiments of the present application, the inorganic coating layer includes an inorganic substance and a binder, the inorganic substance is 70% to 80% by mass percentage, the binder is 20% to 30% by mass percentage, the inorganic substance includes at least one of aluminum oxide, magnesium oxide, calcium oxide, magnesium hydroxide, boehmite, and zirconium oxide, and the binder includes at least one of polyvinylidene fluoride, polypropylene, and polyacrylic acid ester, which is advantageous in improving the adhesion at the interface between the inorganic coating layer and the positive electrode current collector, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0015] In some embodiments of the present application, the Dv99 of the inorganic material is 0.5 μm to 2 μm, which is advantageous for increasing the mixing uniformity between the inorganic material and the binder and improving the adhesion at the interface between the inorganic coating layer and the positive electrode current collector, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0016] In some embodiments of the present application, the secondary battery comprises: (1) When the length of the inorganic coating layer in the longitudinal direction of the positive electrode piece is W mm, the W satisfies 40≦W≦160; (2) When the thickness of the inorganic coating layer in the thickness direction of the positive electrode piece is H μm, the H satisfies 3≦H≦14; At least one of the conditions is met.

[0017] Adjusting W and H within the above ranges is advantageous in enhancing the protective effect of the inorganic coating layer on the positive electrode pieces, thereby further improving the high-temperature safety characteristics of the secondary battery at high voltages.

[0018] In some embodiments of the present application, the secondary battery comprises: (1) The above A satisfies 2≦A≦14, (2) The above B satisfies 0.02≦B≦7.5, (3) The above A and B satisfy 0.2≦B / A≦3, At least one of the conditions is met.

[0019] By adjusting A, B and B / A within the above ranges, it is advantageous to further enhance the protective effect of the inorganic coating layer on the positive electrode piece and reduce the risk of short circuit in the secondary battery, and it is also advantageous to obtain a more uniform CEI film and SEI film, which can ensure the movement of lithium ions in the lithium ion battery and reduce the impedance, thereby further improving the high temperature safety characteristics of the secondary battery at high voltage.

[0020] In a second aspect of the present application, there is provided a power consuming device including the secondary battery according to any one of the above embodiments. Since the secondary battery provided by the present application has good high-temperature safety characteristics at high voltages, the resulting power consuming device has good high-temperature safety characteristics at high voltages.

[0021] The present application provides a secondary battery and a power consumption device, in which a positive electrode active material layer and an inorganic coating layer are provided on the surface of a positive electrode current collector of a positive electrode piece in the secondary battery. The electrolyte solution in the present application contains an additive, and the additive contains at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, and 1,2,3-tris(2-oxoethoxy)propane. The mass per unit area of ​​the inorganic coating layer is expressed as Ag / m 2and the mass percentage of the additive relative to the mass of the electrolyte is B%, A and B satisfy 0.01≦B / A≦5. The present application adopts the above-mentioned structure of the positive electrode piece, selects the above-mentioned electrolyte additive, and adjusts B / A within the above range, which is advantageous for reducing the side reaction between the positive electrode piece and the electrolyte, reducing the overflow of inorganic matter, and improving the warping and deformation of the secondary battery, thereby improving the high-temperature safety characteristics of the secondary battery. It is also advantageous for improving the film formation quality of the CEI film and the SEI film, improving the permeability and flame retardancy of the electrolyte, reducing the oxidation-reduction decomposition of the electrolyte at the interface between the positive electrode and the negative electrode, improving the movement of lithium ions, and reducing impedance, thereby improving the thermal stability and overcharge characteristics of the secondary battery. On the other hand, it is advantageous for enhancing the protective effect of the inorganic coating layer on the positive electrode piece, reducing the risk of short circuit occurrence in the secondary battery, and further improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0022] Of course, it is not necessary for the practice of any product or method herein to achieve all of the above advantages simultaneously. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In order to make the objectives, technical solutions and advantages of the present application clearer, examples are listed below to further describe the present application. It is clear that the described examples are only a part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0024] In the details of the present application, a lithium ion battery is taken as an example of a secondary battery to explain the present application, but the secondary battery of the present application is not limited to a lithium ion battery.

[0025] The inventors have discovered that conventional lithium-ion batteries may be prone to thermal runaway when used in extreme environments such as sustained high temperatures. This is believed to be because, under high temperature and pressure (e.g., temperature of 85°C or higher, voltage of 4.48V or higher), the electrolyte is prone to undergo an oxidation-reduction decomposition reaction with the positive electrode pieces, the CEI film on the surface of the positive electrode pieces is destroyed, and the impedance of the lithium-ion battery continues to increase, causing local deformation, warping, and short circuits in the lithium-ion battery.

[0026] In view of the above, a first aspect of the present application is a secondary battery comprising a positive electrode piece, a negative electrode piece, a separator, and an electrolyte, the positive electrode piece comprising a positive electrode current collector, and a positive electrode active material layer and an inorganic coating layer provided on a surface of the positive electrode current collector, the electrolyte containing an additive, the additive containing at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, and 1,2,3-tris(2-oxoethoxy)propane, and the mass per unit area of ​​the inorganic coating layer is preferably at least one of A g / m 2 and the mass percentage of the additive relative to the mass of the electrolyte is B%, A and B satisfy 0.01≦B / A≦5. In one embodiment of the present application, A and B satisfy 0.2≦B / A≦3. The present application employs the above-mentioned structure of the positive electrode piece, selects the above-mentioned electrolyte additive, and adjusts B / A within the above range, which is advantageous for reducing the side reaction between the positive electrode piece and the electrolyte, thereby improving the high-temperature safety characteristics of the secondary battery. It is also advantageous for improving the film formation quality of the CEI film and the SEI film, and improving the permeability and flame retardancy of the electrolyte, thereby improving the thermal stability and overcharge characteristics of the secondary battery. On the other hand, it is advantageous for enhancing the protective effect of the inorganic coating layer on the positive electrode piece, reducing the risk of short circuit occurrence in the secondary battery, and further improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0027] In some embodiments of the present application, A satisfies 1≦A≦20. In other embodiments of the present application, A satisfies 2≦A≦14. In other embodiments of the present application, A satisfies 2≦A≦8. For example, A is 1 g / m2 , 3.1g / m 2 , 5.2g / m 2 , 7.6g / m 2 , 10g / m 2 , 14.5g / m 2 , or 20 g / m 2 or may be within a range consisting of any two of these values. By adjusting A within the above range, the protective effect of the inorganic coating layer on the positive electrode piece is enhanced, which is advantageous in reducing the risk of short circuit occurrence in the secondary battery, and furthermore, the loss of energy density of the secondary battery can be reduced.

[0028] In some embodiments of the present application, B satisfies 0.01≦B≦10. In another embodiment of the present application, B satisfies 0.02≦B≦7.5. In another embodiment of the present application, B satisfies 0.02≦B≦6. For example, B may be 0.01, 1.2, 2.4, 3.6, 4.7, 7.3, 8.5, or 10, or may be within a range consisting of any two of these values. Adjusting B within the above range is advantageous for improving the thermal stability and overcharge characteristics of the secondary battery, and can further reduce the kinetic loss of the secondary battery.

[0029] In some embodiments of the present application, the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece is 0.1% to 20%. In another embodiment of the present application, the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece is 0.1% to 10%. In another embodiment of the present application, the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece is 1% to 15%. For example, the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece may be 0.1%, 1%, 1.5%, 3%, 5%, 7%, 13%, 16%, or 20%, or may be within a range consisting of any two of these values. By adjusting the ratio of the length of the inorganic coating layer to the total length of the positive electrode piece, it is advantageous to enhance the protective effect of the inorganic coating layer on the positive electrode piece and reduce the risk of short circuit occurrence in the secondary battery, thereby improving the high temperature safety characteristics of the secondary battery at high voltage. The length of the inorganic coating layer can be adjusted according to the size of the entire electrode assembly. That is, when the size of the entire electrode assembly is small, the length of the entire positive electrode piece included in the electrode assembly is short, and in that case, the length of the inorganic coating layer is short. When the size of the entire electrode assembly is large, the length of the positive electrode piece included in the electrode assembly is long, and in that case, the length of the inorganic coating layer is long.

[0030] In some embodiments of the present application, the inorganic coating layer is provided on at least one surface of the positive electrode current collector, and when the length of the inorganic coating layer in the length direction of the positive electrode piece is W mm, the W satisfies 5≦W≦300. In some embodiments of the present application, W satisfies 5≦W≦160. In some embodiments of the present application, W satisfies 40≦W≦160. In some embodiments of the present application, W satisfies 120≦W≦300. For example, W may be 5, 25, 55, 120, 140, 180, 220, 255, 270, or 300, or may be within a range consisting of any two of these values. By setting the length of the inorganic coating layer provided on at least one surface of the positive electrode current collector to W mm, the protective effect of the inorganic coating layer on the positive electrode piece can be further enhanced, and the risk of short circuit occurrence in the secondary battery can be reduced, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0031] In some embodiments of the present application, the inorganic coating layer is provided on two surfaces of the positive electrode current collector, and when the length of the inorganic coating layer on one surface of the positive electrode current collector in the length direction of the positive electrode piece is W1 mm ​​and the length of the inorganic coating layer on the other surface of the current collector is W2 mm, the W1 satisfies 5≦W1≦35, and the W2 satisfies 30≦W2≦300. In some embodiments of the present application, W1 satisfies 5≦W≦35, and W2 satisfies 30≦W≦150. In some embodiments of the present application, W1 satisfies 5≦W≦35, and W2 satisfies 120≦W≦300. By providing inorganic coating layers with lengths W1 mm ​​and W2 mm on both sides of the positive electrode current collector, the protective effect of the inorganic coating layer on the positive electrode piece can be significantly enhanced, and the risk of short circuit occurrence in the secondary battery can be reduced, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0032] In some embodiments of the present application, when the thickness of the inorganic coating layer in the thickness direction of the positive electrode piece is H μm, H satisfies 1≦H≦20. In another embodiment of the present application, H satisfies 3≦H≦14. In another embodiment of the present application, H satisfies 3≦H≦9. For example, H may be 1, 3, 5, 7, 11, 15, 17, or 20, or may be within a range consisting of any two of these values. By adjusting H within the above range, it is advantageous to enhance the protective effect of the inorganic coating layer on the positive electrode piece and reduce the risk of short circuit occurrence in the secondary battery, thereby improving the high temperature safety characteristics of the secondary battery at high voltage. In some embodiments of the present application, inorganic coating layers are provided on both sides of the positive electrode current collector, and the thickness of the inorganic coating layer may be the thickness of the inorganic coating layer on either surface of the positive electrode current collector.

[0033] In some embodiments of the present application, the inorganic coating layer includes an inorganic substance and a binder, the inorganic substance is 70% to 80% by mass percentage, the binder is 20% to 30% by mass percentage, the inorganic substance includes at least one of aluminum oxide, magnesium oxide, calcium oxide, magnesium hydroxide, boehmite, and zirconium oxide, and the binder includes at least one of polyvinylidene fluoride, polypropylene, and polyacrylic acid ester, based on the mass percentage of the inorganic coating layer and the binder, and the mass percentage and the binder are adjusted within the range of the present application, which is advantageous in improving the adhesion at the interface between the inorganic coating layer and the positive electrode current collector, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage.

[0034] In some embodiments of the present application, the Dv99 of the inorganic material is 0.5 μm to 2 μm. By adjusting the Dv99 of the inorganic material within the range of the present application, it is advantageous to increase the mixing uniformity of the inorganic material and the binder during preparation of the inorganic coating layer and to improve the adhesion at the interface between the inorganic coating layer and the positive electrode current collector, thereby improving the high-temperature safety characteristics of the secondary battery at high voltage. In the present application, Dv99 means a particle size at which the cumulative volume calculated from the small diameter side is 99% in the volume-based particle size distribution.

[0035] In the present application, the secondary battery is not particularly limited and may include a device that causes an electrochemical reaction. For example, the secondary battery includes, but is not limited to, a lithium ion secondary battery or a sodium ion secondary battery.

[0036] In the present application, the positive electrode current collector is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode current collector may include an aluminum foil or an aluminum alloy foil. The positive electrode active material layer of the present application includes a positive electrode active material. The positive electrode active material includes lithium and at least one transition metal. For example, the positive electrode active material may include a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound. The lithium transition metal composite oxide may be LiCoO 2 , LiMn 2 O 4, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 , and LiMn 1.5 Ni 0.5 O 4 The lithium-containing transition metal phosphate compound includes, but is not limited to, at least one of LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LifeP 2 O 7 , and LiCoPO 4 The thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm. The thickness of the positive electrode active material layer on one side is 30 μm to 120 μm. Here, the thickness of the inorganic coating layer is equal to or less than the thickness of the positive electrode active material layer. The positive electrode active material layer in the present application may contain a conductive agent and a binder.

[0037] In the present application, the negative electrode sheet is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. In the present application, the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode current collector may include a copper foil, a copper alloy foil, a nickel foil, a titanium foil, a nickel foam, a copper foam, or the like. The negative electrode active material layer in the present application contains a negative electrode active material. In the present application, the type of the negative electrode active material is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode active material includes natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), and may include at least one of lithium metal and the like. In the present application, the thicknesses of the negative electrode current collector and the negative electrode active material layer are not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the negative electrode active material layer on one side is 30 μm to 130 μm. In the present application, the negative electrode active material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on two surfaces in the thickness direction of the negative electrode current collector. Note that the above "surface" may be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector, but is not particularly limited as long as the object of the present application can be achieved.

[0038] The negative electrode active material layer in the present application may include a conductive agent and a binder. In the present application, the conductive agent and the binder are not particularly limited as long as the object of the present application can be achieved. For example, the conductive agent may include at least one of acetylene black, amorphous carbon, conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fiber, flake graphite, carbon dots, and graphene. The binder may include at least one of polypropylene glycol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamide-imide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), aqueous acrylic resin, carboxymethyl cellulose (CMC), and sodium carboxymethyl cellulose (CMC-Na).

[0039] The negative electrode piece in the present application may include an undercoat layer, and the undercoat layer is located between the negative electrode current collector and the negative electrode active material layer, and is provided on at least a part of the surface of the negative electrode current collector. The undercoat layer includes a conductive agent and a binder. The conductive agent includes at least one of carbon fiber, ketjen black, acetylene black, carbon nanotubes, and graphene. The binder includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, acrylic acid ester, and epoxy resin. In the present application, the thickness of the undercoat layer is 0.1 μm to 2.0 μm. An undercoat layer having an appropriate thickness can conduct electrons and at the same time improve the adhesion between the active material layer and the current collector, thereby reducing the peeling of the active material layer during cycling. As a result, the charge transfer resistance of the secondary battery tends to be lowered and the kinetics are improved, and the high-temperature safety characteristics of the secondary battery at high voltages can be improved.

[0040] In the present application, the separator is not particularly limited as long as it can achieve the object of the present application. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film, or a composite membrane having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited, and may be, for example, at least one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate, etc. The binder is not particularly limited, and may be, for example, at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), polytetrafluoroethylene, polyhexafluoropropylene, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, etc. The polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylic ester polymer, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene), and the like.In the present application, the thickness of the separator is not particularly limited as long as the object of the present application can be achieved, and the thickness of the separator is, for example, 5 μm to 50 μm.

[0041] In the present application, the electrolyte may contain other additives, and the other additives include at least one of 1,3-propane sultone, glutaronitrile, and lithium tetrafluoroborate. The content of the other additives is 0.01% to 20% by mass based on the mass of the electrolyte.

[0042] In the present application, the electrolyte further includes an organic solvent and a lithium salt. The organic solvent is 60% to 90% by mass, and the lithium salt is 8% to 15% by mass, based on the mass of the electrolyte. In the present application, the types of the organic solvent and the lithium salt are not particularly limited as long as the object of the present application can be achieved. For example, the organic solvent may include at least one of a carbonate ester compound, a carboxylate compound, an ether compound, and other organic solvents, but is not limited thereto. The carbonate ester compound may include at least one of a chain carbonate compound, a cyclic carbonate compound, and a fluorocarbonate compound, but is not limited thereto. The chain carbonate compound may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. The cyclic carbonate compound may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinyl ethylene carbonate (VEC).The above fluorocarbonate compounds include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, fluoro-2-methylethylene carbonate, fluoromethylethylene carbonate, 1,2-difluoromethylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, The carboxylic acid ester compound may include at least one of, but is not limited to, a chain carboxylic acid ester compound, a fluorocarboxylic acid ester compound, and the like. The carboxylic acid ester compound may include at least one of, but is not limited to, a chain carboxylic acid ester compound, a fluorocarboxylic acid ester compound, and the like. The chain carboxylate compound may include at least one of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate (PP), isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate, but is not limited thereto. The fluorocarboxylate compound may include at least one of methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate, but is not limited thereto. The ether compound may include at least one of chain ether, cyclic ether, and the like, but is not limited thereto.The chain ether may include, but is not limited to, at least one of dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane. The cyclic ether may include, but is not limited to, at least one of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane. The other organic solvent may include, but is not limited to, at least one of phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents. The phosphorus-containing organic solvent may include, but is not limited to, at least one of trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate. The sulfur-containing organic solvent may include, but is not limited to, at least one of sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. The aromatic fluorine-containing solvent may include, but is not limited to, at least one of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene, etc. For example, the lithium salt is LiTFSI, LiPF. 6 , LiBF 4 , LiAsF 6 , LiClO 4, LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiC(SO 2 CF 3 ) 3 , Li 2 SiF 6 , lithium bis(oxalato)borate (LiBOB), and lithium difluoroborate.

[0043] The manufacturing process of the secondary battery of the present application is generally known to those skilled in the art and is not particularly limited in the present application. For example, the manufacturing process includes, but is not limited to, the steps of stacking a positive electrode piece, a separator, and a negative electrode piece in order, and winding or folding them as necessary to obtain an electrode assembly having a wound structure, placing the electrode assembly in a packaging bag, injecting an electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, in order to prevent an increase in pressure inside the secondary battery and overcharging and discharging, an overcurrent protection element, a lead plate, etc. can be placed in the packaging bag as necessary. Here, the packaging bag is a packaging bag known in the art, but is not limited in the present application.

[0044] In a second aspect of the present application, a power consumption device is provided that includes the secondary battery described in the above embodiment. In the present application, the power consumption device is not particularly limited and may be a known power consumption device used in the prior art. For example, the power consumption device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile, a portable copy machine, a portable printer, a stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable tape recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, an electric-assisted bicycle, a bicycle, a lighting device, a toy, a game machine, a clock, an electric tool, a strobe, a camera, a large-scale household storage battery, and a lithium-ion capacitor.

[0045] Working Example Hereinafter, the embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations are performed according to the following methods. Note that, unless otherwise specified, "parts" and "%" are based on mass.

[0046] Measurement methods and devices Inorganic particle size measurement: The Dv99 of inorganic matter was measured using a particle size analyzer.

[0047] Measurement of short circuit deformation rate: The lithium-ion battery is left at 25°C for 30 minutes, and then the lithium-ion battery is charged at a constant current of 0.5 C until the voltage reaches 4.7 V. Then, the battery is charged at a constant voltage of 0.05 C at 4.7 V, and the battery is left at rest for 60 minutes. The thickness of the lithium-ion battery is measured by T 1 Next, the lithium-ion battery was left at rest at 25°C for 30 minutes, and one 100mΩ external current wire was connected to the tab position to generate an external short circuit in the battery. After 1 hour, the thickness of the lithium-ion battery was measured as T 2 The short circuit deformation rate was measured as follows: 2 -T 1 ) / T 1]×100%.

[0048] Overcharge deformation rate measurement: The lithium-ion battery is left at 25°C for 30 minutes, and then the lithium-ion battery is charged at a constant current of 0.5C until the voltage reaches 4.7V. Then, the lithium-ion battery is charged at a constant voltage of 4.7V until the current reaches 0.05C. The battery is left at rest for 60 minutes, and the thickness of the lithium-ion battery is measured. 3 Then, the lithium-ion battery was charged at a constant current of 0.1C for 60 minutes and left to stand for 30 minutes. The above steps were repeated five times to bring the lithium-ion battery to a 150% state of charge (SOC), and the thickness of the lithium-ion battery was measured as T 4 The overcharge deformation rate was measured as follows: Overcharge deformation rate = [(T 4 -T 3 ) / T 3 ]×100%.

[0049] Voltage drop measurement: At 25°C, a lithium-ion battery was charged at 1C with a constant current until the voltage reached 4.7V, then charged at a constant voltage of 0.05C at 4.7V, and discharged at a constant current of 1C until the voltage reached 3.2V. The battery was then left to stand for 5 minutes, and the voltage was measured as the voltage before storage. The battery was then stored at -20°C for 24 hours, and the voltage was measured again as the voltage after storage. Voltage drop = voltage before storage - voltage after storage.

[0050] Thermal stability measurements: The lithium-ion battery was left at 25°C for 30 minutes to keep the temperature constant, and the initial thickness was measured. 0 Then, the temperature was increased to 130°C at a rate of 5°C / min, maintained at 130°C for 30 minutes, and then cooled to room temperature. The thickness of the lithium-ion battery was measured as T 5 The thermal stability deformation rate was measured as follows: 5 -T 0 ) / T 0 ]×100%.

[0051] Example 1-1 <Preparation of positive electrode piece> Lithium cobalt oxide (LiCoO) as a positive electrode active material 2), Super-P as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were mixed in a mass ratio of 97:1:2, N-methylpyrrolidone (NMP) was added, and the mixture was stirred with a vacuum stirrer until it was uniform, to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly applied to one surface of an aluminum foil as a positive electrode current collector with a thickness of 12 μm, and the aluminum foil was dried at 120 ° C for 1 hour to obtain a positive electrode active material layer with a thickness of 80 μm on one side. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode piece with a positive electrode active material layer applied on both sides. After cold pressing and cutting, the tab was welded, and then dried under vacuum conditions at 120 ° C for 1 hour, and a positive electrode piece with a size of 74 mm (width) x 854 mm (length) was obtained, which had an uncoated current collector area at the end of the positive electrode piece.

[0052] Aluminum oxide (Dv99 is 0.7 μm) and PVDF as a binder were mixed in a mass ratio of 80:20, N-methylpyrrolidone (NMP) was added, and the mixture was stirred with a vacuum stirrer until it became uniform, to obtain an inorganic coating layer slurry with a solid content of 30 wt%. First, the inorganic coating layer slurry was uniformly applied to one surface (the surface is designated as a-side, and the other surface of the current collector is designated as b-side) of an aluminum foil serving as a positive electrode current collector located at the end of the positive electrode piece, and dried at 120° C. for 1 hour to obtain a positive electrode piece having an inorganic coating layer provided on the a-side, which is one surface of the current collector. The length of the inorganic coating layer was 95 mm, and the thickness of the inorganic coating layer was 2.5 μm.

[0053] <Preparation of negative electrode piece> Acetylene black, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener were mixed in a mass ratio of 50:45:5, deionized water was added, and a negative electrode undercoat layer slurry with a solid content of 30 wt% was obtained using a vacuum mixer. The negative electrode undercoat layer slurry was uniformly applied to one surface of a copper foil as a negative electrode current collector with a thickness of 8 μm, and the copper foil was dried at 120° C. to obtain a negative electrode undercoat layer with a thickness of 1 μm. The above steps were then repeated on the other surface of the copper foil to obtain a negative electrode current collector with a negative electrode undercoat layer applied to both sides.

[0054] Next, artificial graphite, SBR as a binder, and carboxymethylcellulose sodium (CMC-Na) as a thickener were mixed in a mass ratio of 97.4:1.2:1.4, deionized water was added, and a negative electrode slurry with a solid content of 75 wt% was obtained by a vacuum agitator. The negative electrode slurry was uniformly applied to one surface of the negative electrode current collector having the above-mentioned negative electrode undercoat layer, and the copper foil was dried at 120 ° C. to obtain a negative electrode active material layer with a thickness of 100 μm on one side. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode piece with a negative electrode active material layer applied on both sides. After cold pressing, cutting, and slitting, it was dried under vacuum conditions at 120 ° C. for 1 hour to obtain a negative electrode piece with a size of 76 mm × 867 mm.

[0055] <Preparation of electrolyte> In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propyl propionate (PP), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1 to obtain an organic solvent. Then, LiPF as a lithium salt was added to the organic solvent. 6 and lithium difluorophosphate as an additive to obtain an electrolyte. 6 The mass percentage of lithium difluorophosphate was 12.5%, the mass percentage of lithium difluorophosphate was 0.15%, and the balance was an organic solvent, and the mass percentage of each substance was calculated based on the mass of the electrolyte.

[0056] <Preparation of separator> A porous polyethylene film with a thickness of 7 μm was used.

[0057] <Making a lithium-ion battery> The positive electrode pieces, separator, and negative electrode pieces prepared as above were stacked and wound in order so that the separator was interposed between the positive electrode pieces and the negative electrode pieces to provide an insulating effect, and the electrode assembly was obtained. The electrode assembly was placed in an aluminum plastic film packaging bag, dried to remove moisture, and then an electrolyte was injected into the aluminum plastic film packaging bag, and a lithium ion battery was obtained through processes such as vacuum packaging, standing, formation, deaeration, and trimming.

[0058] Examples 1-2 to 1-16 In <Preparation of Positive Electrode Pieces>, the thickness of the inorganic coating layer was adjusted according to Table 1 to adjust the mass per unit area of ​​the inorganic coating layer, and in <Preparation of Electrolyte>, the type and content of the electrolyte additives were adjusted according to Table 1, and the content of the organic solvent was changed accordingly. 6 The results were the same as in Example 1-1, except that the content of was not changed.

[0059] Examples 2-1 to 2-6 The procedure was the same as in Example 1-2, except that the length of the inorganic coating layer was adjusted in <Preparation of the positive electrode piece>. The length of the inorganic coating layer on the a-side is shown in Table 2.

[0060] Examples 2-7 to 2-8 In <Preparation of Positive Electrode Pieces>, the size of the positive electrode piece was adjusted to 163 mm × 2275 mm, the size of the negative electrode piece was adjusted to 167 mm × 2283 mm, and the length of the inorganic coating layer was adjusted, but the same procedure was followed as in Example 1-2. The length of the inorganic coating layer on side a is shown in Table 2.

[0061] Examples 2-9 In <Preparation of positive electrode pieces>, the inorganic coating layer was prepared as follows, but the procedure was the same as in Example 1-2. Aluminum oxide (Dv99 is 0.7 μm) and PVDF as a binder were mixed in a mass ratio of 80:20, N-methylpyrrolidone (NMP) was added, and the mixture was stirred until homogeneous using a vacuum stirrer to obtain an inorganic coating layer slurry with a solid content of 30 wt%. First, the inorganic coating layer slurry was uniformly applied to the a-side of the aluminum foil, which is the positive electrode current collector located at the end of the positive electrode piece, and dried at 120 ° C. for 1 hour. After that, the above steps were repeated on the b-side of the positive electrode piece, and the positive electrode piece was dried to obtain a positive electrode piece in which an inorganic coating layer was applied to two surfaces of the current collector. Here, the lengths of the inorganic coating layers on the a-side and the b-side are shown in Table 2.

[0062] Example 2-10 In <Preparation of Positive Electrode Pieces>, the size of the positive electrode piece was adjusted to 163 mm × 2275 mm, the size of the negative electrode piece was adjusted to 167 mm × 2283 mm, and the lengths of the inorganic coating layers on the a-side and b-side of the positive electrode current collector were adjusted, but the same procedure was followed as in Example 2-9. The lengths of the inorganic coating layers on the a-side and b-side are shown in Table 2.

[0063] Examples 2-11 to 2-14 The <Preparation of Positive Electrode Pieces> was the same as in Example 1-2, except that the thickness of the inorganic coating layer was adjusted. Here, the thickness of the inorganic coating layer is shown in Table 2.

[0064] Examples 3-1 to 3-7 In <Preparation of Positive Electrode Pieces>, the type, content, and Dv99 of inorganic substances and the type and content of binders were adjusted according to Table 3, and the same was true for Example 1-1.

[0065] Comparative Example 1 In <Preparation of electrolyte>, the type and content of electrolyte additives were adjusted according to Table 1, and the content of organic solvent was changed accordingly. 6 The results were the same as in Example 1-2, except that the content of was not changed.

[0066] Comparative Example 2 In <Preparation of Positive Electrode Pieces>, the thickness of the inorganic coating layer was adjusted according to Table 1 to adjust the mass per unit area of ​​the inorganic coating layer, and in <Preparation of Electrolyte>, the type and content of the electrolyte additives were adjusted according to Table 1, and the content of the organic solvent was changed accordingly. 6 The same as in Example 1-2, except that the content of is not changed.

[0067] [Table 1]

[0068] As can be seen from Examples 1-1 to 1-16 and Comparative Examples 1 and 2, by adopting the structure of the positive electrode piece in the present application, selecting the electrolyte additive within the range of the present application, and adjusting B / A within the range of the present application, the overcharge deformation rate, short circuit deformation rate, voltage drop, and thermal stability deformation rate of the obtained lithium ion battery are significantly reduced. This shows that the lithium ion battery according to the present application has excellent high temperature safety characteristics at high voltage.

[0069] [Table 2]

[0070] As can be seen from Examples 2-1 to 2-10, by adjusting the length of the inorganic coating layer in the length direction of the positive electrode piece within the range of the present application, the overcharge deformation rate, short circuit deformation rate, voltage drop, and thermal stability deformation rate of the obtained lithium ion battery are reduced. This shows that the lithium ion battery has excellent high-temperature safety characteristics at high voltage. As can be seen from Examples 1-2 and 2-11 to 2-14, by adjusting the thickness of the inorganic coating layer within the range of the present application, the lithium ion battery not only has excellent high-temperature safety characteristics at high voltage, but also ensures high energy density.

[0071] [Table 3]

[0072] The type and content of inorganic materials and binders generally affect the high-temperature safety characteristics of lithium-ion batteries at high voltages. As can be seen from Examples 3-1 to 3-7, by adjusting the above parameters within the ranges of the present application, the overcharge deformation rate, short circuit deformation rate, voltage drop, and thermal stability deformation rate of the lithium-ion battery are reduced, and the lithium-ion battery has excellent high-temperature safety characteristics at high voltages.

[0073] Since the embodiments in this specification are described in relation to each other, identical or similar parts between the embodiments can be referred to each other. In each embodiment, the differences from other embodiments will be mainly described.

[0074] The above are only preferred embodiments of the present application, and do not limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included within the protection scope of the present application.

Claims

1. A secondary battery comprising a positive electrode piece, a negative electrode piece, a separator, and an electrolyte, The positive electrode piece includes a positive electrode current collector, and a positive electrode active material layer and an inorganic coating layer are provided on a surface of the positive electrode current collector, the electrolyte solution includes an additive, the additive including at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, and 1,2,3-tris(2-oxoethoxy)propane; The mass per unit area of ​​the inorganic coating layer is represented by Ag g / m ２ and when a mass percentage of the additive with respect to the mass of the electrolyte is B%, A and B satisfy 0.01≦B / A≦5.

2. The secondary battery according to claim 1 , wherein A satisfies 1≦A≦20.

3. The secondary battery according to claim 1 , wherein B satisfies 0.01≦B≦10.

4. The secondary battery according to any one of claims 1 to 3, wherein when the thickness of the inorganic coating layer in the thickness direction of the positive electrode piece is H μm, H satisfies 1≦H≦20.

5. The secondary battery according to any one of claims 1 to 4, wherein the length of the inorganic coating layer in the longitudinal direction of the positive electrode piece accounts for 0.1% to 20% of the total length of the positive electrode piece.

6. the inorganic coating layer is provided on at least one surface of the positive electrode current collector, The secondary battery according to any one of claims 1 to 5, wherein when the length of the inorganic coating layer in the longitudinal direction of the positive electrode piece is W mm, W satisfies 5≦W≦300.

7. the inorganic coating layer is provided on two surfaces of the positive electrode current collector, 7. The secondary battery according to claim 1, wherein, when a length of the inorganic coating layer on one surface of the positive electrode current collector is W1 mm ​​and a length of the inorganic coating layer on the other surface of the positive electrode current collector is W2 mm, W1 satisfies 5≦W1≦35 and W2 satisfies 30≦W2≦300.

8. The inorganic coating layer contains an inorganic substance and a binder, With respect to the mass of the inorganic coating layer, the inorganic substance is present in a mass percentage of 70% to 80% and the binder is present in a mass percentage of 20% to 30%; The inorganic material includes at least one of aluminum oxide, magnesium oxide, calcium oxide, magnesium hydroxide, boehmite, and zirconium oxide; the binder includes at least one of polyvinylidene fluoride, polypropylene, and polyacrylic ester; The secondary battery according to any one of claims 1 to 7, wherein the inorganic material has a Dv99 of 0.5 µm to 2 µm.

9. (1) When the length of the inorganic coating layer in the longitudinal direction of the positive electrode piece is W mm, W satisfies 40≦W≦160; (2) When the thickness of the inorganic coating layer in the thickness direction of the positive electrode piece is H μm, H satisfies 3≦H≦14; (3) The A satisfies 2≦A≦14; (4) The B satisfies 0.02≦B≦7.5; (5) A and B satisfy 0.2≦B / A≦3; The secondary battery according to any one of claims 1 to 8, which satisfies at least one of the above conditions.

10. A power consuming device comprising the secondary battery according to any one of claims 1 to 9.

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