A battery, a battery pack, and an electric device

Abstract

The application provides a battery, a battery pack and an electric device, the battery comprising: a negative electrode sheet comprising a graphite material; a positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising a nickel-cobalt-manganese ternary positive electrode material containing a doping element; and an electrolyte comprising a solvent and an additive, the solvent comprising a carboxylic acid ester solvent, and the additive comprising a negative electrode protection additive and a positive electrode protection additive; the graphitization degree of the graphite material is A%, the molar ratio of the doping element to the sum of the doping element, a nickel element, a cobalt element and a manganese element in the positive electrode active material is B%, the mass fraction of the carboxylic acid ester solvent in the electrolyte is a%, the mass fraction of the negative electrode protection additive in the electrolyte is b%, and the mass fraction of the positive electrode protection additive in the electrolyte is c%; the battery satisfies 5≤(A-80+a) / b≤50 and 0.003≤(B+c) / a≤1; and the low-temperature rate performance and the high-temperature cycle stability of the battery can be improved simultaneously.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a battery, a battery pack, and an electrical device. Background Technology

[0002] Nickel-cobalt-manganese ternary lithium-ion batteries (NCM ternary batteries) are widely used in fields with extremely high requirements for energy density and adaptability to extreme environments due to their high energy density, high operating voltage, and long cycle life. For example, drones require batteries to operate stably in extreme temperature ranges from -50°C to 80°C, while new energy vehicles in frigid or tropical regions need batteries that can simultaneously achieve rapid charging / discharging at low temperatures and safe cycle performance at high temperatures. These application scenarios create an urgent need for NCM ternary lithium-ion batteries to simultaneously optimize both low-temperature power performance and high-temperature cycle stability, but current technologies struggle to achieve a synergistic improvement in both. Summary of the Invention

[0003] This invention provides a battery, a battery pack, and an electrical device that can simultaneously optimize the battery's low-temperature power performance and high-temperature cycle stability.

[0004] One aspect of the present invention provides a battery, comprising: a negative electrode sheet comprising graphite material; a positive electrode sheet comprising a positive electrode active material, wherein the positive electrode active material comprises a nickel-cobalt-manganese ternary positive electrode material containing doped elements; an electrolyte comprising a solvent and additives, wherein the solvent comprises a carboxylic acid ester solvent, and the additives comprise a negative electrode protection additive and a positive electrode protection additive; the graphitization degree of the graphite material is A%, the molar ratio of the doped element to the total of the doped element, nickel, cobalt, and manganese in the positive electrode active material is B%, the mass fraction of the carboxylic acid ester solvent in the electrolyte is a%, the mass fraction of the negative electrode protection additive in the electrolyte is b%, and the mass fraction of the positive electrode protection additive in the electrolyte is c%; the battery satisfies: 5≤(A-80+a) / b≤50, 0.003≤(B+c) / a≤1.

[0005] According to one embodiment of the present invention, A is 85~99, preferably 85~98; and / or, B is 0.001~10; and / or, a is 1~70; and / or, b is 0.1~10; and / or, c is 0.1~10.

[0006] According to one embodiment of the present invention, the doping element includes one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, and F.

[0007] According to one embodiment of the present invention, the carboxylic acid ester solvent includes one or more of ethyl acetate, ethyl propionate, propyl acetate, methyl acetate, and methyl propionate.

[0008] According to one embodiment of the present invention, the negative electrode protection additive includes one or more of ethylene carbonate and fluoroethylene carbonate.

[0009] According to one embodiment of the present invention, the positive electrode protection additive includes phosphate ester additives; preferably, the phosphate ester additives include one or more of tris(trimethyl)silane phosphate and tris(trimethylsilane) phosphite.

[0010] According to one embodiment of the present invention, the solvent further includes one or more of cyclic carbonate solvents and chain carbonate solvents.

[0011] According to one embodiment of the present invention, the additive further includes auxiliary additives, which include one or more of the following: methylene disulfonate, vinylene sulfate, vinylene disulfonate, propylene sulfonate lactone, 1,3-propane sulfonate lactone, vinyl sulfite, lithium difluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxaborate, and lithium tetrafluorooxalate phosphate.

[0012] According to one embodiment of the present invention, the battery further includes an electrolyte salt.

[0013] According to one embodiment of the present invention, the electrolyte salt includes a lithium salt; preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium trifluoromethylsulfonylimide, lithium difluorooxalate borate, and lithium difluorooxalate phosphate.

[0014] According to one embodiment of the present invention, the battery further includes a separator, the separator including a base layer and a functional layer disposed on at least one side of the base layer, the functional layer including a ceramic layer and an adhesive layer disposed between the ceramic layer and the base layer.

[0015] In another aspect, the present invention provides a battery pack comprising at least two batteries connected to each other.

[0016] In another aspect, the present invention provides an electrical device including the battery or the battery pack described above.

[0017] The battery, battery pack, and electrical device provided in this invention simultaneously introduce a negative electrode sheet containing graphite material, a ternary positive electrode material containing doped elements (nickel-cobalt-manganese), and an electrolyte containing a carboxylic acid ester solvent, a negative electrode protection additive, and a positive electrode protection additive. By optimizing the performance and proportion of the above components, the battery satisfies the following two relationships: 5≤(A-80+a) / b≤50 and 0.003≤(B+c) / a≤1. The carboxylic acid ester solvent and the graphite material with a high degree of graphitization can reduce the viscosity of the electrolyte, increase the conductivity, and improve lithium-ion diffusion. The positive electrode protection additive, the negative electrode protection additive, and the ternary positive electrode material containing doped elements can stabilize the positive electrode structure, stabilize the positive and negative electrode interface, reduce side reactions, and reduce impedance, thereby synergistically improving the high and low temperature performance of the battery and extending its service life. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Existing technologies mainly improve the low-temperature power performance or high-temperature cycle stability of NCM ternary batteries by optimizing electrolyte composition and positive and negative electrode materials.

[0020] Specifically, in optimizing electrolyte composition, adding low-viscosity solvents (such as carboxylic acid esters) can reduce the low-temperature viscosity of the electrolyte, promoting lithium-ion migration and thus improving the low-temperature power performance of NCM ternary batteries. However, low-viscosity solvents have poor compatibility with the negative electrode interface, easily triggering side reactions. Alternatively, adding fluorinated additives (such as FEC) or phosphate ester additives (such as TMSPO) can form a stable SEI / CEI film, inhibiting electrolyte decomposition at high temperatures and thus improving the high-temperature cycle stability of NCM ternary batteries. However, these additives will form films that increase battery impedance and reduce low-temperature power performance.

[0021] In optimizing cathode and anode materials, high-porosity graphite anodes can be used to enhance low-temperature ion diffusion efficiency, thereby improving the low-temperature power performance of NCM ternary batteries. However, excessively high anode porosity can reduce electrode compaction density, leading to capacity decay. Alternatively, doping the ternary cathode lattice structure with metal elements can reduce high-temperature oxygen release, thus improving the high-temperature cycle stability of NCM ternary batteries. However, multi-element doping may block lithium-ion diffusion channels, impairing the battery's low-temperature power performance.

[0022] In summary, there is a compatibility conflict between the low-temperature improvement methods and the high-temperature improvement methods in the existing improvement technologies, making it difficult to meet both requirements at the same time. Furthermore, there is a lack of systematic optimization of components such as positive and negative electrode materials and electrolytes in the battery, resulting in insignificant performance improvement.

[0023] In view of the above, embodiments of the present invention provide a battery, comprising: a negative electrode sheet comprising graphite material; a positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising a nickel-cobalt-manganese ternary positive electrode material containing doped elements; an electrolyte comprising a solvent and additives, the solvent comprising a carboxylic acid ester solvent, the additives comprising a negative electrode protection additive and a positive electrode protection additive; the graphitization degree of the graphite material is A%, the molar ratio of the doped element to the total of the doped element, nickel, cobalt and manganese elements in the positive electrode active material is B%, the mass fraction of the carboxylic acid ester solvent in the electrolyte is a%, the mass fraction of the negative electrode protection additive in the electrolyte is b%, and the mass fraction of the positive electrode protection additive in the electrolyte is c; the battery satisfies: 5≤(A-80+a) / b≤50, 0.003≤(B+c) / a≤1.

[0024] According to the inventors' research, a higher degree of graphitization (i.e., a larger A value) in graphite materials is more conducive to lithium-ion transport. At this level, lithium ions can be rapidly intercalated and deintercalated within the graphite material, reducing the Warburg impedance (Rw) during charge and discharge, thereby improving the battery's low-temperature power performance. However, a high degree of graphitization in the graphite material can exacerbate the volume expansion of the negative electrode and electrolyte side reactions during charge and discharge. Additionally, carboxylic acid ester solvents, due to their low viscosity and high conductivity, can reduce electrolyte viscosity at low temperatures, increase lithium-ion conductivity at low temperatures, and reduce the solution impedance (Rs) during charge and discharge, thus improving the battery's low-temperature power performance. However, carboxylic acid ester solvents have poor compatibility with negative electrodes (e.g., graphite negative electrodes), easily leading to reduction and gas generation near the negative electrode, damaging the negative electrode interface. Therefore, introducing negative electrode protective additives to protect the negative electrode interface can alleviate these problems. When the battery satisfies the formula 5≤(A-80+a) / b≤50, the graphitization degree of the graphite material, the proportion of carboxylic acid ester solvent, and the proportion of negative electrode protective additives can be controlled within a suitable range, thereby improving the high and low temperature performance of the battery.

[0025] Furthermore, elemental doping in positive electrode active materials (such as nickel-cobalt-manganese ternary cathode materials) can stabilize the cathode structure, reduce oxygen release and structural collapse, thereby improving the high-temperature cycle stability of the battery. However, elemental doping can block lithium-ion diffusion channels, reducing the battery's low-temperature power performance. Additionally, introducing cathode protective additives can reduce electrolyte corrosion of the cathode interface and synergistically improve the cathode's structural stability, thus enhancing the battery's high-temperature cycle performance. However, oxide film formation at the cathode interface typically increases battery impedance, reducing low-temperature power performance. In this case, carboxylic acid ester solvents in the electrolyte can improve the battery's low-temperature power performance, mitigating these adverse effects. When the battery satisfies the formula 0.003 ≤ (B+c) / a ≤ 1, the doping level of the positive electrode active material, the proportion of carboxylic acid ester solvent, and the proportion of cathode protective additives can be controlled within appropriate ranges, thereby improving the battery's high and low temperature performance.

[0026] In summary, when the battery satisfies the two relationships mentioned above, carboxylic acid ester solvents and graphite materials with high graphitization can improve the low-temperature power performance of the battery by reducing electrolyte viscosity, increasing conductivity, and improving lithium-ion diffusion. At the same time, elemental doping in positive electrode protection additives, negative electrode protection additives, and positive electrode active materials can improve the high-temperature cycle stability of the battery and extend its service life by stabilizing the positive electrode structure, stabilizing the positive and negative electrode interface, reducing side reactions, and reducing impedance.

[0027] For example, (A-80+a) / b can be a range consisting of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or any two of them; (B+c) / a can be a range consisting of 0.003, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any two of them.

[0028] In some embodiments, A can be 85 to 99, for example, it can be a range of 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or any two of these, preferably 85 to 98. When A is within the above range, it is more beneficial to improve the orderliness of the graphite crystal structure, increase electron mobility, reduce the Rw impedance of the battery, thereby improving the low-temperature power performance of the battery.

[0029] In this embodiment of the invention, the degree of graphitization of the graphite material can be measured by conventional techniques in the art, and there are no particular limitations. For example, it can be measured by X-ray diffraction (XRD). Specifically, it may include the following steps: testing the graphite material with an X-ray diffractometer to obtain the position of the diffraction peak of the (002) crystal plane of the graphite material, and then using Bragg's formula d 002=λ / 2sinθ to calculate the interplanar spacing (d) of the (002) crystal plane. 002 Then, according to the formula A%=(0.3440- d 002 The graphitization degree A of the graphite material is calculated by 100% of (0.3440-0.3354) / (0.3440-0.3354).

[0030] It should be noted that the graphite material used for XRD testing can be obtained from a battery. Specifically, the process may include the following steps: after the battery is completely discharged, the negative electrode sheet is disassembled, scraped to obtain a negative electrode coating, and then the negative electrode coating is ground and mixed with silicon powder. The resulting sample is then subjected to XRD testing. During the XRD analysis, the position of the graphite 002 peak needs to be corrected using the silicon elemental standard peak.

[0031] In some specific embodiments, the graphite material may include natural graphite.

[0032] In some embodiments, B can be 0.001 to 10, for example, it can be a range of 0.001, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any combination thereof. When B is within the above range, it is more beneficial to reduce the oxygen release in the positive electrode active material, reduce electrolyte corrosion, and improve the lattice structure stability of the positive electrode active material, thereby improving the high-temperature cycle performance of the battery.

[0033] In this embodiment of the invention, the molar ratio of the dopant element to the total of the dopant element, nickel, cobalt, and manganese in the positive electrode active material can be measured by conventional techniques in the art, and there are no particular limitations. For example, it can be measured by inductively coupled plasma mass spectrometry (ICP-MS). Specifically, it can include the following steps: using an inductively coupled plasma mass spectrometer (ICP-MS) to test the nickel-cobalt-manganese ternary positive electrode material to obtain the content of the dopant element, the content of nickel, the content of cobalt, and the content of manganese in the nickel-cobalt-manganese ternary positive electrode material, and then calculating the B value according to the formula B% = dopant element content / (dopant element content + nickel content + cobalt content + manganese content) × 100%.

[0034] It should be noted that the positive electrode active material used for ICP-MS testing can be obtained from the battery. Specifically, it can include the following steps: after the battery is completely discharged, the positive electrode sheet is disassembled, the positive electrode sheet is scraped to obtain the positive electrode coating, and the positive electrode coating sample is digested before it can be used for ICP-MS testing.

[0035] In some specific embodiments, the chemical formula of the nickel-cobalt-manganese ternary cathode material can be LiNi. x Co y Mn z L(100-x-y-z) O2, where 90≤x+y+z<100, and L is a dopant element.

[0036] Specifically, the doping elements may include one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, and F.

[0037] Preferably, the doping element may include at least two of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, and F; more preferably, the doping element may include at least three of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, and F.

[0038] In some embodiments, 'a' can be 1 to 70, for example, a range of 1, 10, 20, 30, 40, 50, 60, 70, or any combination thereof. When 'a' is within the above range, it is more advantageous to reduce the viscosity of the electrolyte, increase the ionic conductivity of the electrolyte, and reduce the Rs impedance of the battery under low-temperature conditions, thereby improving the low-temperature power performance of the battery.

[0039] In some specific embodiments, the carboxylic acid ester solvent may include one or more of ethyl acetate (EA), ethyl propionate (EP), propyl acetate (PA), methyl acetate (MA), and methyl propionate (MP).

[0040] In some embodiments, b can be 0.1 to 10, for example, a range of 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any combination thereof. When b is within the above range, it is more beneficial to reduce the negative electrode interface reaction, maintain the stability of the negative electrode interface, and thus improve the high-temperature cycle performance of the battery.

[0041] In some specific embodiments, the negative electrode protection additive may include one or more of ethylene carbonate and fluoroethylene carbonate, which can form an organic-inorganic composite SEI (solid electrolyte interface) / CEI (cathode electrolyte interface) film on the negative electrode surface. This is more conducive to reducing interfacial side reactions of the electrolyte, constructing a dense and stable protective layer, and also more conducive to reducing high-temperature gas generation and high-temperature impedance growth of the battery, thereby improving the high-temperature cycle performance of the battery.

[0042] In some embodiments, c can be 0.1 to 10, for example, it can be a range of 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any combination thereof. When c is within the above range, it is more beneficial to reduce the positive electrode interface reaction, maintain the stability of the positive electrode interface, and thus improve the high-temperature cycle performance of the battery.

[0043] In some specific embodiments, the positive electrode protection additive may include phosphate ester additives, which can form an organic-inorganic composite SEI (solid electrolyte interface) / CEI (cathode electrolyte interface) film on the positive electrode surface, which is more conducive to reducing high-temperature gas generation in the battery and stabilizing the positive electrode lattice structure, thereby improving the high-temperature cycle performance of the battery.

[0044] Specifically, phosphate ester additives may include one or more of tris(trimethyl)silane phosphate and tris(trimethylsilane) phosphite.

[0045] In some embodiments, the solvent may further include one or more of cyclic carbonate solvents and chain carbonate solvents. Cyclic carbonate solvents have a high dielectric constant, which is more conducive to dissolving electrolyte salts and promoting ion dissociation, thereby improving the ion transport capacity of the electrolyte and thus improving the low-temperature rate performance of the battery. Chain carbonate solvents, on the other hand, have low viscosity and good fluidity, which is more conducive to reducing electrolyte resistance and increasing lithium-ion migration rate, thereby improving the low-temperature rate performance of the battery.

[0046] In some specific embodiments, cyclic carbonate solvents may include one or more of ethylene carbonate (EC) and propylene carbonate (PC).

[0047] In some specific embodiments, the chain carbonate solvent may include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0048] In some embodiments, the additive may further include auxiliary additives, which may include one or more of the following: methylene disulfonate, vinylene sulfate, vinylene disulfonate, propylene sulfonate lactone, 1,3-propane sulfonate lactone, vinylene sulfite, lithium difluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxaborate, and lithium tetrafluorooxalate phosphate. This is more conducive to inhibiting electrolyte decomposition, improving ion conduction efficiency, and enhancing the stability of the positive and negative electrode interfaces, thereby improving the battery's cycle life, rate performance, safety performance, and high-temperature storage stability.

[0049] In some embodiments, the battery also includes an electrolyte salt that provides ions to the battery and acts as a carrier for ion conduction to ensure ion migration and charge balance during battery charging and discharging.

[0050] Specifically, the electrolyte salt includes one or more of the following: hexafluorophosphate, difluorosulfonylimide salt, trifluoromethylsulfonylimide salt, difluorooxalate borate, and difluorooxalate phosphate.

[0051] In some specific embodiments, the electrolyte salt may include a lithium salt.

[0052] Specifically, lithium salts may include one or more of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium trifluoromethanesulfonylimide, lithium difluorooxalateborate, and lithium difluorooxalate phosphate.

[0053] In some embodiments, the battery also includes a separator that separates the positive and negative electrodes, prevents short circuits, and allows lithium ions to pass through to ensure ion conduction.

[0054] In some specific embodiments, the separator may include a base layer and a functional layer disposed on at least one side of the base layer. The functional layer includes a ceramic layer and an adhesive layer disposed between the ceramic layer and the base layer. This is more advantageous in increasing the separator's liquid retention capacity while also improving its stress performance, reducing high-temperature corrosion and high-temperature shrinkage, thereby improving the battery's high and low temperature performance.

[0055] Specifically, the base layer may include one or more of polypropylene (PP) or polyethylene (PE); the adhesive layer may include one or more of surface-active macromolecules, such as polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, polyethylene glycol methacrylate, polystyrene-polyethylene glycol, polyacrylic acid, and polyacrylamide; and the ceramic layer may include one or more of alumina or silicon oxide.

[0056] The present invention also provides a battery pack comprising at least two interconnected batteries as described above. This battery pack has advantages corresponding to the batteries described above, which will not be elaborated further.

[0057] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0058] The present invention also provides an electrical device, including the battery or battery pack described above, which has advantages corresponding to the battery or battery pack described above, and will not be described in detail here.

[0059] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0060] The present invention will be further described below through specific embodiments. Unless otherwise specified, all raw materials and reagents used in the following embodiments and comparative examples are commercially available conventional types.

[0061] Example 1

[0062] (1) Preparation of electrolyte

[0063] The organic solvent, electrolyte salt, and additives were mixed at a mass ratio of 70.5:16:13.5 under dew point conditions to obtain the electrolyte solution. The concentration of the electrolyte salt in the electrolyte solution was 1.1 mol / L.

[0064] The organic solvent is a mixture of cyclic carbonate solvent ethylene carbonate (EC), chain carbonate solvent methyl ethyl ester (EMC), and carboxylic acid ester solvent ethyl acetate (EA) in a mass ratio of 19:16.5:35; the electrolyte salt is a mixture of lithium hexafluorophosphate (LiPF6) and lithium trifluoromethanesulfonate (LiFSI) in a molar ratio of 4:7; and the additives are a mixture of negative electrode protection additive (fluoroethylene carbonate, FEC), positive electrode protection additive (tris(trimethylsilane)phosphite, TMSPI), conventional additive (methylene methane disulfonate, MMDS), and lithium salt additive (lithium difluorophosphate, LiPO2F2) in a mass ratio of 1.5:10:1:1.

[0065] (2) Preparation of negative electrode sheet

[0066] The negative electrode active material (natural graphite, Gr), conductive agent (carbon nanotubes, CNT), binder (styrene-butadiene rubber, SBR), and thickener (sodium carboxymethyl cellulose, CMC) were mixed in a mass ratio of 100:2:3:2, and a solvent (water) was added to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of the negative electrode current collector (copper foil), dried under vacuum at 80°C for 24 hours, and then rolled and cut to obtain the negative electrode sheet. The graphitization degree of the natural graphite was 99%.

[0067] (3) Preparation of positive electrode sheet

[0068] The positive electrode active material (LiNi) 30 Co 30 Mn 30 Zr3Mg3AL4O2 (NCM), conductive agent (carbon black, Super-P), and binder (polyvinylidene fluoride, PVDF) are mixed in a mass ratio of 100:20:3. A solvent (N-methylpyrrolidone, NMP) is added to obtain a positive electrode slurry. The positive electrode slurry is coated on both sides of the positive electrode current collector (aluminum foil), dried under vacuum at 100°C for 24 hours, and then rolled and cut to obtain a positive electrode sheet.

[0069] (4) Battery preparation

[0070] After the above positive electrode sheet, separator (3D ceramic multilayer separator) and negative electrode sheet are slit, wound, hot pressed, baked, injected with liquid, sealed, formed and aged, a 5Ah finished lithium-ion battery is obtained.

[0071] Compared to Example 1, the differences between Examples 2-9 and Comparative Examples 1-4 include: the mass fraction of organic solvent in the electrolyte (denoted as w). 溶剂 The mass fraction of electrolyte salts in the electrolyte (denoted as w) 锂盐 The mass fraction of additives in the electrolyte (denoted as w) 添加剂 The following parameters are listed: the mass ratio of EC, EMC, and EA in the organic solvent (referred to as solvent mass ratio); the mass ratio of FEC, TMSPI, MMDS, and LiPO2F2 in the additives (referred to as additive mass ratio); the degree of graphitization of the negative electrode active material (natural graphite); and the chemical formula of the positive electrode active material. These parameters are summarized in Table 1.

[0072] Table 1

[0073]

[0074] In addition, the batteries prepared in the above embodiments and comparative examples were subjected to the following tests.

[0075] (1) X-ray diffraction (XRD) test

[0076] The graphite material was tested using an X-ray diffractometer (Bruker D8 ADVANCE) to obtain the positions of the diffraction peaks on the (002) crystal plane of the graphite material, and the results were obtained using Bragg's formula d. 002 =λ / 2sinθ to calculate the interplanar spacing (d) of the (002) crystal plane. 002 Then, according to the formula A%=(0.3440- d 002 The graphitization degree A% of the graphite material was calculated by (0.3440-0.3354) ×100%. The specific test data are shown in Table 2.

[0077] (2) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Test

[0078] The nickel-cobalt-manganese ternary cathode material sample was digested using a nitric acid-hydrofluoric acid mixed acid, then diluted to a fixed volume, and the ICP-MS instrument (Agilent 5800) was calibrated. The diluted sample solution was then injected into the ICP-MS instrument, where plasma ionization converted the elements into charged ions. After separation by a mass analyzer, the ion signal intensity was detected. Finally, the concentration of each element in the sample was calculated based on the calibration curve. Combined with the sample volume and dilution factor, the content of doping elements, nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary cathode material was obtained. Finally, the B value was calculated using the formula B% = doping element content / (doping element content + nickel content + cobalt content + manganese content) × 100%. The specific test data are shown in Table 2.

[0079] (3) Low-temperature charge and discharge power test

[0080] The battery was charged to 4.1V using a 1C constant current and constant voltage method with a cutoff current of 0.05C, and then discharged to 2.8V using a 1C method for capacity determination. After capacity determination, the battery was adjusted to 50% SOC (State of Charge) using a 1Cs current and capacity cutoff condition. After adjusting the SOC, the battery was placed in a low-temperature environment chamber and kept at -45℃ for 6 hours. A 6C rate current discharge test was then performed, and the discharge voltage of the battery under these conditions was recorded as the low-temperature 6C discharge voltage. The specific test data are shown in Table 3.

[0081] Battery high temperature performance test

[0082] The battery was placed in a 60-degree oven for high-temperature cycling. The battery was charged at a constant current and constant voltage of 1C to 4.1V, with a cutoff current of 0.05C, and then discharged at 1C to 2.8V. Every 250 cycles, the battery was placed at room temperature for capacity recovery. The high-temperature capacity retention rate of the battery after 1500 cycles was recorded as the high-temperature capacity retention rate. The specific test data are shown in Table 3.

[0083] The parameters A, B, a, b, c, (A-80+a) / b, and (B+c) / a of the batteries obtained in the above embodiments and comparative examples are summarized in Table 2.

[0084] Table 2

[0085]

[0086] The low-temperature 6C discharge voltage and high-temperature capacity retention of the batteries obtained in the above embodiments and comparative examples are summarized in Table 3.

[0087] Table 3

[0088]

[0089] Based on the data in Tables 1-3, compared to Comparative Examples 1-4, Examples 1-9 simultaneously introduce graphite-based negative electrode sheets, nickel-cobalt-manganese ternary positive electrode materials containing doped elements, and electrolytes including carboxylic acid ester solvents, negative electrode protection additives, and positive electrode protection additives into the battery. By optimizing the performance and proportion of the above components, the battery satisfies the two relationships 5≤(A-80+a) / b≤50 and 0.003≤(B+c) / a≤1. This ensures that the battery has good low-temperature power while also having excellent high-temperature cycle performance, thus balancing the battery's requirements for both low-temperature power and high-temperature cycle performance and effectively broadening the application range of ternary lithium-ion batteries.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery, characterized in that, include: Negative electrode sheet, including graphite material; A positive electrode sheet, including a positive electrode active material, wherein the positive electrode active material includes a nickel-cobalt-manganese ternary positive electrode material containing doped elements; An electrolyte, comprising a solvent and additives, wherein the solvent includes a carboxylic acid ester solvent, and the additives include a negative electrode protection additive and a positive electrode protection additive; The graphitization degree of the graphite material is A; the molar ratio of the dopant element to the total of the dopant element, nickel, cobalt, and manganese in the positive electrode active material is B; the mass fraction of the carboxylic acid ester solvent in the electrolyte is a%; the mass fraction of the negative electrode protective additive in the electrolyte is b%; and the mass fraction of the positive electrode protective additive in the electrolyte is c%. The battery satisfies: 5≤(A-80+a) / b≤50, 0.003≤(B+c) / a≤1.

2. The battery according to claim 1, characterized in that, The value of A is 85-99, preferably 85-98; And / or, the value of B is 0.001~10; And / or, the value of a is 1 to 70; And / or, the value of b is 0.1 to 10; And / or, the c is 0.1~10.

3. The battery according to claim 1 or 2, characterized in that, The doping element includes one or more of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, and F.

4. The battery according to any one of claims 1-3, characterized in that, The carboxylic acid ester solvent includes one or more of ethyl acetate, ethyl propionate, propyl acetate, methyl acetate, and methyl propionate.

5. The battery according to any one of claims 1-4, characterized in that, The negative electrode protection additive includes one or more of ethylene carbonate and fluoroethylene carbonate.

6. The battery according to any one of claims 1-5, characterized in that, The positive electrode protection additive includes phosphate ester additives; Preferably, the phosphate ester additive includes one or more of tris(trimethyl)silane phosphate and tris(trimethylsilane) phosphite.

7. The battery according to any one of claims 1-6, characterized in that, The solvent also includes one or more of cyclic carbonate solvents and chain carbonate solvents.

8. The battery according to any one of claims 1-7, characterized in that, The additives also include auxiliary additives, which include one or more of the following: methylene disulfonate, vinylene sulfate, vinylene disulfonate, propylene sulfonate lactone, 1,3-propane sulfonate lactone, vinyl sulfite, lithium difluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxaborate, and lithium tetrafluorooxalate phosphate.

9. The battery according to any one of claims 1-8, characterized in that, The battery also includes an electrolyte salt.

10. The battery according to claim 9, characterized in that, The electrolyte salt includes lithium salt; Preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium trifluoromethylsulfonylimide, lithium difluorooxalate borate, and lithium difluorooxalate phosphate.

11. The battery according to any one of claims 1-10, characterized in that, The battery further includes a separator, which includes a base layer and a functional layer disposed on at least one side of the base layer. The functional layer includes a ceramic layer and an adhesive layer disposed between the ceramic layer and the base layer.

12. A battery pack, characterized in that, It includes at least two interconnected batteries as described in any one of claims 1-11.

13. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1-11 or the battery pack as described in claim 12.

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