Battery and electrical apparatus

Abstract

The present application discloses a battery and an electrical apparatus. The battery comprises: a positive electrode plate, the positive electrode plate comprising a lithium iron phosphate material; an electrolyte, the electrolyte comprising an additive, and the additive comprising: formula (1) as shown. In formula (1), X1, X2, X3, and X4 each independently comprise H, F, or a fluorine-substituted or unsubstituted alkyl having 1-3 carbon atoms; on the basis of the total mass of the electrolyte, the mass proportion of the compound represented by formula (1) is 2% to 10%. The battery of the present application can significantly improve capacity attenuation of the lithium iron phosphate battery at low temperatures.

Description

Batteries and electrical devices

[0001] Priority information

[0002] This application claims priority and benefits of patent application 202410405401.9 filed with the State Intellectual Property Office of China on April 3, 2024, and incorporates the entire text of it herein by reference. Technical Field

[0003] The present application belongs to the field of batteries, and specifically relates to a battery and an electrical device. Background Art

[0004] Secondary batteries are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As battery applications expand, the performance requirements for secondary batteries are becoming increasingly stringent, such as requiring them to maintain good performance at low temperatures. For example, lithium iron phosphate batteries, the active positive electrode material, have relatively poor conductivity and are prone to polarization, which can lead to battery capacity degradation, especially at low temperatures. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a battery, which aims to improve the capacity attenuation of lithium iron phosphate batteries at low temperatures.

[0006] In order to achieve the above objectives, the first aspect of the present application provides a battery, comprising:

[0007] A positive electrode plate, the positive electrode plate comprising a positive electrode active material, the positive electrode active material being a lithium iron phosphate material;

[0008] An electrolyte, the electrolyte comprising an additive, the additive comprising:

[0009] In Formula 1, X1, X2, X3 and X4 each independently include any one of H, F, fluorine-substituted or unsubstituted alkyl groups of 1-3 carbon atoms, and the mass proportion of the compound represented by Formula 1 is 2%-10% based on the total mass of the electrolyte.

[0010] The present application includes at least the following beneficial effects: in the battery of the present application, adding the additive shown in Formula 1 to the electrolyte and controlling its content can greatly improve the capacity attenuation of the lithium iron phosphate battery at low temperatures.

[0011] In some embodiments, the lithium iron phosphate material includes LiMn x Fe 1-x-y M yPO4, wherein 0≤x≤1, 0≤y≤0.04, and M comprises at least one of Ti, Mg, Ta, Sc, Cr, Y, Zr, Nb, Mo, La, Ta, W, Hf, V, Ni, Rh, or Os.

[0012] In some embodiments, based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 3%-8%, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0013] In some embodiments, based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 3% to 10%. This can significantly improve the capacity decay of the lithium iron phosphate battery at low temperatures.

[0014] In some embodiments, based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 2% to 8%, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0015] In some embodiments, the compound represented by Formula 1 includes at least one of fluoroethylene carbonate, bisfluoroethylene carbonate, 3,3,3-trifluoropropylene carbonate, or 4,4,5,5-tetrafluoro-1,3-dioxolane-2-one. Thus, the capacity decay of the lithium iron phosphate battery at low temperatures can be significantly improved.

[0016] In some embodiments, the battery further comprises a negative electrode plate, wherein the negative electrode plate comprises a silicon-based material, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0017] In some embodiments, the silicon-based material accounts for 2% to 10% of the total mass of the negative electrode active material, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0018] In some embodiments, the mass of the silicon-based material accounts for 4% to 8% of the total mass of the negative electrode active material, thereby effectively improving the charge and discharge capacity of the lithium-ion battery at low temperatures.

[0019] In some embodiments, the volume average particle size Dv50 of the silicon-based material is less than or equal to 6 μm, thereby greatly improving the capacity attenuation of the lithium iron phosphate battery at low temperatures.

[0020] In some embodiments, the volume average particle size Dv50 of the silicon-based material is 1 μm to 6 μm, thereby significantly improving the capacity attenuation of the lithium iron phosphate battery at low temperatures.

[0021] In some embodiments, the electrolyte further comprises a solvent, wherein the solvent comprises ethylene carbonate, and the weight percentage of the ethylene carbonate is 10%-25% based on the total weight of the electrolyte. This can significantly improve the capacity decay of the lithium iron phosphate battery at low temperatures.

[0022] In some embodiments, the mass proportion of the ethylene carbonate is 15%-20% based on the total mass of the electrolyte, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0023] In some embodiments, the solvent further comprises at least one of propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, dipropyl carbonate, ethylpropyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, or gamma-butyrolactone. Thus, the capacity fade of the lithium iron phosphate battery at low temperatures can be significantly improved.

[0024] In some embodiments, the electrolyte further comprises a lithium salt, and the lithium salt comprises lithium bis(fluorosulfonyl)imide. Thus, the capacity decay of the lithium iron phosphate battery at low temperatures can be greatly improved.

[0025] In some embodiments, the mass of the lithium bis(fluorosulfonyl)imide accounts for 3% to 8% of the total mass of the electrolyte, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0026] In some embodiments, the mass of the lithium bis(fluorosulfonyl)imide accounts for 5% to 8% of the total mass of the electrolyte, thereby significantly improving the capacity decay of the lithium iron phosphate battery at low temperatures.

[0027] In some embodiments, the volume average particle size Dv50 of the positive electrode active material is 1 μm to 3 μm, thereby significantly improving the capacity attenuation of the lithium iron phosphate battery at low temperatures.

[0028] In some embodiments, the compacted density of the positive electrode sheet is 2.3 g / cm 3 -2.8g / cm 3 Therefore, the capacity attenuation of lithium iron phosphate batteries at low temperatures can be greatly improved.

[0029] In a second aspect of the present application, the present application proposes an electrical device comprising the battery described in the first aspect of the present application.

[0030] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0032] FIG1 is a schematic diagram of a battery according to one embodiment of the present application.

[0033] FIG. 2 is an exploded view of the battery according to one embodiment of the present application shown in FIG. 1 .

[0034] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0035] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0036] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0037] FIG6 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0038] Explanation of reference numerals: 1 battery cell; 11 housing; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[0039] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0040] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] Currently, judging by market developments, the application of secondary batteries is becoming increasingly widespread. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace, among other fields.

[0046] As the application scope of secondary batteries becomes wider and wider, the requirements for secondary battery performance are also becoming increasingly stringent, such as maintaining good performance at low temperatures. As a common positive electrode active material, lithium iron phosphate materials have a wider source of raw materials, are cheaper, have no environmental pollution, and have good cycle performance. However, lithium iron phosphate materials themselves have relatively poor conductivity and are prone to polarization, which can easily lead to battery capacity decay. This phenomenon is especially obvious at low temperatures. After the positive electrode plate is made, the water therein includes bound water and adsorbed water. Among them, bound water is difficult to dry. After the battery is formed, the bound water will enter the electrolyte, react to produce acid, and then destroy the electrode interface, causing battery capacity decay and affecting the battery life.

[0047] In the present application, for the lithium iron phosphate material of the positive electrode, the additive shown in Formula 1 is added to the electrolyte and its content is controlled. During the battery production process, the adsorbed water in the battery pole piece is first released, which can promote the reaction of the additive shown in Formula 1 with the lithium salt in the electrolyte. The generated compound covers the surface of the lithium iron phosphate material particles, inhibiting the release of bound water in the lithium iron phosphate material during subsequent battery use, and can alleviate the corrosion of the battery pole piece by the acid generated by the bound water entering the electrolyte, thereby improving the battery life at low temperatures.

[0048] Controlling the content of the compound represented by Formula 1 within a range of 2% to 10% can not only reduce the amount of generated compounds caused by too little content, so that the compound represented by Formula 1 reacts with the lithium salt to generate sufficient compounds to block the release of bound water in the lithium iron phosphate material, but also reduce the excessive surface coverage of the lithium iron phosphate material particles caused by an excess of the compound represented by Formula 1, thereby reducing the increase in battery impedance, maintaining a high lithium ion transmission efficiency at low temperatures, and reducing battery capacity decay.

[0049] The battery disclosed in the embodiment of the present application includes a lithium-ion battery, and the battery disclosed in the embodiment of the present application can be used in electrical devices that use the battery as a power source or various energy storage systems that use the battery as an energy storage element. Electrical devices may include but are not limited to mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles and spacecraft, etc.

[0050] In a first aspect, the present application provides a battery, comprising a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises a lithium iron phosphate material, and the electrolyte comprises an additive, wherein the additive comprises:

[0051] In Formula 1, X1, X2, X3 and X4 each independently include any one of H, F, fluorine-substituted or unsubstituted alkyl groups of 1-3 carbon atoms, and the mass proportion of the compound represented by Formula 1 is 2%-10% based on the total mass of the electrolyte.

[0052] For example, when X1, X2, X3 and X4 each independently include any one of fluorine-substituted or unsubstituted alkyl groups of 1 to 3 carbon atoms, the number of carbon atoms in the alkyl group can be 1 to 2, 2 to 3, etc.

[0053] In the battery of the present application, the additive shown in Formula 1 is added to the electrolyte and its content is controlled. During the battery manufacturing process, high-temperature standing, high-temperature formation, and high-temperature aging are performed after liquid injection to first release the adsorbed water in the positive electrode plate, which can promote the reaction of the additive shown in Formula 1 with the lithium salt in the electrolyte. The generated compound covers the surface of the lithium iron phosphate material particles, inhibits the escape of bound water in the lithium iron phosphate material during subsequent battery use, and can alleviate the corrosion of the battery plate by the acid generated by the bound water entering the electrolyte, thereby improving the battery life at low temperatures.

[0054] It can be understood that lithium iron phosphate materials refer to at least one of lithium iron phosphate (LiFePO4) and its modified materials, and the modified materials may include coating, mixing or doping with other materials or elements.

[0055] In some embodiments of the present application, the mass percentage of the compound represented by Formula 1 is 2%-10% based on the total mass of the electrolyte. For example, the mass percentage of the compound represented by Formula 1 can be 2%-9.9%, 3%-9%, 4%-8%, 5%-7%, 6%-7%, etc. By controlling the mass percentage of the additive in the electrolyte within the above range, after the adsorbed water in the electrode is released, the additive represented by Formula 1 can be promoted to react with the lithium salt in the electrolyte. The resulting compound covers the surface of the lithium iron phosphate material particles, inhibiting the escape of bound water in the lithium iron phosphate material during subsequent battery use and alleviating the corrosion of the battery electrode by the acid generated by the bound water entering the electrolyte, thereby improving the battery life at low temperatures. In addition, the amount of compound generated due to too little content can be reduced, so that the compound generated by the reaction of the compound represented by Formula 1 with the lithium salt is sufficient to prevent the escape of bound water in the lithium iron phosphate material. The excessive surface coverage of the lithium iron phosphate material particles caused by excessive addition of the additive can also be reduced, thereby reducing the increase in battery impedance, maintaining high lithium ion transmission efficiency at low temperatures, and reducing battery capacity decay. In other embodiments of the present application, based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 3%-8%.

[0056] It can be understood that regardless of whether the battery has undergone formation treatment or not, as long as the mass proportion of the compound described in Formula 1 in the electrolyte is within the range defined in the claims of this application (2%-10%), it falls within the scope of protection of this application.

[0057] It is understood that “the mass proportion of the compound represented by Formula 1 based on the total mass of the electrolyte” is a definition known in the art and can be measured by methods known in the art, for example, the following method can be used for measurement:

[0058] The composition and content of the compound represented by Formula 1 were quantitatively analyzed by gas chromatography according to the reference standard GB / T9722-2006.

[0059] In some embodiments of the present application, the mass proportion of the compound represented by Formula 1 is 3%-10% based on the total mass of the electrolyte. It is understood that the mass proportion of the compound represented by Formula 1 in the electrolyte (3%-10%) can be the content of the compound represented by Formula 1 before the battery is formed, that is, the amount of the compound represented by Formula 1 added as a raw material during battery preparation. Controlling the mass proportion of the compound represented by Formula 1 within the above range can improve the life of the battery at low temperatures.

[0060] In some embodiments of the present application, the mass proportion of the compound represented by Formula 1 is 2%-8% based on the total mass of the electrolyte. In the electrolyte, the mass proportion of the compound represented by Formula 1 (2%-8%) can be the content of the compound represented by Formula 1 after the battery is formed. For example, the mass proportion of the compound represented by Formula 1 before formation is 3%. After formation, due to participation in the reaction, the mass proportion of the compound represented by Formula 1 can be reduced to 2%. Controlling the mass proportion of the compound represented by Formula 1 within the above range can improve the life of the battery at low temperatures.

[0061] In some embodiments of the present application, the lithium iron phosphate material includes LiMn x Fe 1-x-y M y PO4, wherein 0≤x≤1, 0≤y≤0.04, and M comprises at least one of Ti, Mg, Ta, Sc, Cr, Y, Zr, Nb, Mo, La, Ta, W, Hf, V, Ni, Rh, or Os. For example, x may be 0-0.99, 0.1-0.9, 0.2-0.8, 0.3-0.7, 0.4-0.6, etc., and y may be 0-0.04, 0.01-0.03, 0.01-0.02, 0.02-0.03, etc.

[0062] In some embodiments of the present application, the positive electrode active material includes LiMn x Fe 1-x-y M y Composite material of PO4 and carbon.

[0063] In some embodiments of the present application, the battery further comprises a negative electrode plate, which comprises a silicon-based material. Since lithium iron phosphate materials themselves have poor electrical conductivity and are prone to polarization, resulting in a large resistance to lithium ion shuttle, causing serious battery capacity decay. At low temperatures, the polarization of lithium iron phosphate materials will be more serious, and the battery capacity decay will be aggravated. The negative electrode active material is a silicon-based material. Due to the high capacity of silicon-based materials, the coating thickness of the negative electrode active material layer on the negative electrode plate can be reduced under the conditions of the same energy density, thereby effectively reducing the migration distance of lithium ions between the negative electrode active material layers, improving the efficiency of lithium ion transmission, and compensating for the negative effect of the high lithium ion shuttle resistance on the lithium ion transmission efficiency in lithium iron phosphate materials at low temperatures, so that the efficiency of lithium ion transmission at low temperatures is high, reducing the decay of battery capacity at low temperatures. In addition, since silicon-based materials have many hydroxyl groups on the surface, they are sensitive to water or HF generated by water and are easily corroded by water or HF. In the embodiment of the present application, the additive shown in Formula 1 is added to the electrolyte and its content is controlled to reduce the corrosion of water in the electrolyte on the silicon-based material and improve the cycle performance of the battery at low temperatures.

[0064] It can be understood that the resistance to the shuttle of lithium ions in the positive electrode and the negative electrode is the main factor affecting the efficiency of lithium ion transmission, which affects the capacity of the battery and further affects the capacity decay of the battery. The embodiment of the present application adds silicon-based materials to the negative electrode active material to make the transmission efficiency of lithium ions in the negative electrode higher at low temperatures, thereby compensating for the low transmission efficiency of lithium ions in the positive electrode at low temperatures, and thus reducing the capacity decay of the battery at low temperatures.

[0065] It can be understood that silicon-based materials refer to materials containing silicon. As an example, silicon-based materials include but are not limited to elemental silicon, silicon oxide compounds, silicon-carbon composites, lithium-containing silicon-carbon materials, lithium-containing silicon oxide materials, magnesium-containing silicon-carbon materials and magnesium-containing silicon oxide materials, silicon-nitrogen composites and at least one of silicon alloys.

[0066] In some embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of the silicon-based material is 2%-10%. For example, based on the total mass of the negative electrode active material, the mass proportion of the silicon-based material can be 2%-9.9%, 3%-9%, 4%-8%, 5%-7%, 6%-7%, etc. Specifically, the content of the silicon-based material is controlled within the above range. The silicon-based material has a high capacity and can reduce the coating thickness of the negative electrode active material layer on the negative electrode sheet under the same energy density. This effectively reduces the migration distance of lithium ions between the negative electrode active material layers, which can compensate for the effect of the high lithium ion shuttle resistance in lithium iron phosphate materials on the lithium ion transmission efficiency at low temperatures, thereby increasing the efficiency of lithium ion transmission at low temperatures, reducing the battery capacity decay at low temperatures, and reducing the reduction in negative electrode conductivity caused by excessive silicon content, thereby improving the capacity decay of lithium iron phosphate batteries at low temperatures. In other embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of the silicon-based material is 4%-8%.

[0067] It is understood that “the mass proportion of the silicon-based material based on the total mass of the negative electrode active material” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0068] The composition and content of silicon can be determined by elemental analysis using inductively coupled plasma optical emission spectrometry (ICP, Ametek, model: SPECTROARCOSICP-OES) with reference to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015.

[0069] In some embodiments of the present application, the compound represented by Formula 1 includes at least one of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate, 3,3,3-trifluoropropylene carbonate, or 4,4,5,5-tetrafluoro-1,3-dioxolane-2-one (CAS No.: 183301-46-4). Specifically, the above-mentioned additive can react with the lithium salt (such as LiPF6) in the electrolyte in the presence of a small amount of water, and the generated compound (such as lithium phosphorus oxyfluoride) covers the surface of the lithium iron phosphate material particles, thereby inhibiting the escape of bound water in the lithium iron phosphate material during subsequent battery use, and can alleviate the corrosion of the battery electrode by the acid generated by the bound water entering the electrolyte, thereby improving the battery life at low temperatures.

[0070] In some embodiments of the present application, the volume average particle size Dv50 of the silicon-based material is less than or equal to 6 μm. For example, the volume average particle size Dv50 of the silicon-based material can be 0.1 μm-5.9 μm, 0.5 μm-5.5 μm, 1 μm-5 μm, 1.5 μm-4.5 μm, 2 μm-4 μm, 2.5 μm-3.5 μm, etc. In other embodiments of the present application, the volume average particle size Dv50 of the silicon-based material is 1 μm-6 μm. Specifically, the volume average particle size Dv50 of the silicon-based material is controlled within the above range. At low temperatures, since the silicon-based material has many hydroxyl groups on its surface, it is sensitive to water or HF generated by water and is easily corroded by water or HF. The smaller the particle size of the silicon-based material, the more serious the corrosion. The present application adds the additive shown in Formula 1 to the electrolyte and controls its content, which can inhibit the increase of water in the electrolyte and reduce the corrosion of the silicon-based material by moisture. Therefore, small-particle silicon-based materials can be used in the battery system of the present application. The present application sets the particle size of the silicon-based material to be less than or equal to 6μm, which can shorten the diffusion path of lithium ions, reduce the impedance of the battery, increase the electrolyte infiltration area, and thus improve the low-temperature performance of the battery. It can also reduce the increase in the reaction area caused by the too low particle size of the silicon-based material, reduce the probability of side reactions, and extend the life of the battery.

[0071] It is understood that the “volume average particle size Dv50 of the silicon-based material” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0072] Referring to the standard GB / T 19077-2016, the volume average particle size Dv50 of the silicon-based material can be obtained by testing the silicon-based material using a laser particle size analyzer (such as Malvern Master Sizer 3000).

[0073] In some embodiments of the present application, the electrolyte further comprises a solvent, wherein the solvent comprises ethylene carbonate, and the mass proportion of the ethylene carbonate based on the total mass of the electrolyte is 10%-25%. For example, based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate can be 10%-24%, 11%-23%, 12%-22%, 13%-21%, 14%-20%, 15%-19%, 16%-18%, etc. Specifically, when the content of the additive shown in Formula 1 in the electrolyte is high, the battery life can be improved, but the battery dynamics may be reduced. Therefore, the addition of ethylene carbonate (EC) to the electrolyte can improve the battery dynamics. In addition, controlling the mass proportion of ethylene carbonate within the range of 10%-25% can, on the one hand, reduce the increase in electrolyte viscosity caused by excessive ethylene carbonate at low temperatures, maintain high electrolyte conductivity, reduce lithium ion migration resistance, increase lithium ion diffusion rate, and thus reduce battery capacity decay. On the other hand, it can reduce the effect of too little ethylene carbonate on the stability of the battery SEI film and improve the battery life. In summary, controlling the ethylene carbonate content in the electrolyte within the above range can reduce the capacity decay of the battery at low temperatures and further improve the battery life. In other embodiments of the present application, the weight proportion of the ethylene carbonate is 15%-20% based on the total weight of the electrolyte.

[0074] It is understood that "the mass proportion of ethylene carbonate based on the total mass of the electrolyte" is a definition well known in the art and can be measured by methods well known in the art, for example, the following method can be used for measurement:

[0075] The content of ethylene carbonate in the electrolyte was quantitatively analyzed by gas chromatography with reference to the standard GB / T9722-2006.

[0076] It is understood that based on the total mass of the electrolyte, the mass proportion of the compound represented by Formula 1 is 2%-10%, and the mass proportion of ethylene carbonate is 10%-25%. Within the above range, when the content of the additive represented by Formula 1 is relatively high, the content of EC can be appropriately reduced. A high content of the additive represented by Formula 1 can increase the battery life, but may reduce the battery dynamics. Reducing the EC content can further improve the battery dynamics.

[0077] In some embodiments of the present application, the solvent further comprises at least one of propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, dipropyl carbonate, ethylpropyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, or gamma-butyrolactone. Thus, the combination of solvents can produce an electrolyte system with an appropriate lithium salt concentration, higher conductivity, and better stability, which can better improve the capacity fade of lithium iron phosphate batteries at low temperatures.

[0078] In some embodiments of the present application, the electrolyte further includes a lithium salt, including lithium bis(fluorosulfonyl)imide. Lithium bis(fluorosulfonyl)imide (LiFSI) has a strong polarity and can further combine with a small amount of bound water released from the subsequent electrode, reducing the diffusion of water into the negative electrode and damaging the SEI film, thereby extending the battery life at low temperatures.

[0079] In some embodiments of the present application, the mass proportion of the lithium bis(fluorosulfonyl)imide based on the total mass of the electrolyte is 3%-8%. For example, based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide can be 3%-7.9%, 3.5%-7.5%, 4%-7%, 4.5%-6.5%, 5%-6%, etc. Thus, although the additive shown in Formula 1 can inhibit the bound water in the lithium iron phosphate material from entering the electrolyte, as the battery cycles, a small amount of bound water in the lithium iron phosphate material will still enter the electrolyte. By controlling the mass proportion of lithium bis(fluorosulfonyl)imide in the electrolyte within the above range, lithium bis(fluorosulfonyl)imide can further combine with the small amount of bound water escaping from the subsequent electrode, reducing the diffusion of water to the negative electrode to damage the SEI film, thereby improving the battery life at low temperatures, and reducing the risk of incompatibility between lithium bis(fluorosulfonyl)imide and the negative electrode interface caused by excessive lithium bis(fluorosulfonyl)imide, thereby avoiding damage to the negative electrode side interface and deteriorating the battery life. In other embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the lithium bis(fluorosulfonyl)imide is 5%-8%.

[0080] It is understood that “the mass proportion of lithium bis(fluorosulfonyl)imide based on the total mass of the electrolyte” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0081] The content of lithium bis(fluorosulfonyl)imide in the electrolyte was quantitatively analyzed by ion chromatography according to the reference standard JY / T020-1996.

[0082] It is understood that the mass proportion of the compound represented by Formula 1 is 2%-10%, and the mass proportion of lithium bis(fluorosulfonyl)imide is 3%-8%. Within the above range, when the content of the additive represented by Formula 1 is relatively high, the content of lithium bis(fluorosulfonyl)imide can be appropriately reduced. When the content of the additive represented by Formula 1 is high, the probability of bound water in the lithium iron phosphate material entering the electrolyte is reduced, and the amount of lithium bis(fluorosulfonyl)imide can be correspondingly reduced.

[0083] In some embodiments of the present application, the volume average particle size Dv50 of the positive electrode active material is 1 μm-3 μm. For example, the volume average particle size Dv50 of the positive electrode active material can be 1 μm-2.9 μm, 1.2 μm-2.7 μm, 1.5 μm-2.5 μm, 18 μm-2.2 μm, etc. Specifically, controlling the volume average particle size Dv50 of the positive electrode active material within the above range can, on the one hand, shorten the diffusion path of lithium ions and effectively reduce the migration distance of lithium ions between the positive electrode active material layers, thereby compensating for the negative effect of the high lithium ion shuttle resistance in lithium iron phosphate materials on the lithium ion transmission efficiency at low temperatures, thereby increasing the efficiency of lithium ion transmission at low temperatures and further reducing the attenuation of battery capacity at low temperatures. On the other hand, the lithium ion transmission efficiency of the negative electrode is high, and the lithium ion diffusion efficiency of the positive and negative electrodes of the battery is matched, thereby reducing the occurrence of the positive electrode's ability to deintercalate and deintercalate lithium being weaker than that of the negative electrode at low temperatures, thereby fully utilizing the battery's discharge capacity.

[0084] It is understood that the “volume average particle size Dv50 of the positive electrode active material” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0085] Referring to the standard GB / T 19077-2016, the volume average particle size Dv50 of the positive electrode active material can be obtained by testing the positive electrode active material using a laser particle size analyzer (such as Malvern Master Sizer 3000).

[0086] In some embodiments of the present application, the compaction density of the positive electrode sheet is 2.3 g / cm 3 -2.8g / cm 3 For example, the compaction density of the positive electrode sheet can be 2.3g / cm 3 -2.7g / cm 3 , 2.4g / cm 3 -2.7g / cm 3 , 2.5g / cm 3 -2.7g / cm 3 , 2.6g / cm 3 -2.7g / cm 3Specifically, controlling the compaction density of the positive electrode sheet within the above range can reduce the difficulty of lithium ion insertion or extraction caused by excessive or insufficient compaction density of the positive electrode sheet, increase the discharge capacity of the battery, reduce internal resistance, reduce polarization loss, and extend the cycle life of the lithium-ion battery.

[0087] It is understood that the “compacted density of the positive electrode sheet” is a well-known definition in the art and can be measured by methods well-known in the art. For example, it can be measured by the following method:

[0088] By measuring the mass of the positive electrode per unit area (g / cm 2 ) and the thickness of the positive electrode sheet (cm) (the number of collection points is greater than 14). Among them, the compaction density ρ of the positive electrode sheet c = Mass of positive electrode per unit area (g / cm 2 ) / thickness of positive electrode sheet (cm).

[0089] 1) Compaction density test of positive electrode:

[0090] Obtain a battery positive electrode sheet that meets the machinability requirements, use a punching machine to punch out a positive electrode sheet with a diameter of 14 mm, and use an electronic balance and a desktop digital thickness gauge to measure the mass m of the positive electrode sheet. c , thickness d c Use a punching machine to punch out a sufficient number of aluminum foil substrates with a diameter of 14 mm, and use an electronic balance and a desktop digital thickness gauge to measure the mass m of the aluminum foil substrates respectively Al , thickness d Al .

[0091] Positive electrode compaction density

[0092] Where: c is the positive electrode compaction density, in grams per cubic centimeter (g / cm 3 );

[0093] m c is the mass of the positive electrode, in grams (g);

[0094] m Al is the mass of the aluminum foil substrate, in grams (g);

[0095] is the diameter of the positive electrode, in millimeters (mm);

[0096] d c is the thickness of the positive electrode sheet, in micrometers (μm);

[0097] d Al is the thickness of the aluminum foil substrate, in micrometers (μm).

[0098] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active metal ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0099] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material described in the present application.

[0100] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0101] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0102] In some embodiments of the present application, the positive electrode active material may also include lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co0.1 Mn 0.1 O2 (also referred to as NCM 811 )), or lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) at least one.

[0103] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active materials refer to the initial state of the material, i.e., the state before addition of the materials. When the positive electrode active materials are used in a battery system, the molar Li content will change after charge and discharge cycles.

[0104] In the list of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0105] In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0106] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0107] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0108] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector.

[0109] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0110] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] In some embodiments, the negative electrode active material may also be a negative electrode active material commonly known in the art for use in batteries. For example, the negative electrode active material may include at least one of the following: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, and lithium titanate. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials; other conventional materials used as negative electrode active materials for batteries may also be used.

[0112] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0113] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0115] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0116] In some embodiments of the present application, the electrolyte includes an electrolyte salt, a solvent, and an additive.

[0117] In some embodiments of the present application, the electrolyte salt may further include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bistrifluoromethanesulfonyl imide, lithium fluorosulfonate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate or lithium tetrafluorooxalatophosphate.

[0118] In some embodiments of the present application, the solvent may further include at least one of sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0119] In some embodiments of the present application, the electrolyte may further include other additives. For example, the other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0120] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0121] In some embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0122] The battery of the present application includes a battery cell form, a battery module form and a battery pack form. The battery cell, battery module and battery pack of the present application are described below with reference to the accompanying drawings as appropriate.

[0123] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0124] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0125] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery may also be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0126] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 1 having a square structure as an example.

[0127] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0128] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0129] Figure 3 shows an example battery module 2. Referring to Figure 3 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0130] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0131] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0132] Figures 4 and 5 illustrate an example battery pack 3. Referring to Figures 4 and 5 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0133] In addition, the present application also provides an electric device, which includes the battery proposed in the first aspect of the present application. The battery cell, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0134] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0135] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0136] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0137] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0138] Example 1

[0139] 1. Preparation of positive electrode sheet

[0140] The positive electrode active material LiFePO4 (volume average particle size Dv50 is 1.5μm), the binder polyvinylidene fluoride, and the conductive agent super P are mixed in a weight ratio of 97.2:1.8:1, and the solvent N-methylpyrrolidone (NMP) is added and stirred to form a positive electrode slurry; then the slurry is coated on the current collector aluminum foil, dried, cold pressed, slit, and cut into pieces to form the positive electrode sheet of the lithium ion battery. The compaction density of the positive electrode sheet is 2.5g / cm 3 .

[0141] 2. Preparation of negative electrode sheet

[0142] The negative electrode active material (silicon carbon material (volume average particle size Dv50 is 5 μm): graphite = 5:95), conductive agent carbon black, thickener sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96.8:0.7:0.9:1.6, added into deionized water as a solvent, and stirred to form a negative electrode slurry. The negative electrode slurry is obtained under the action of a vacuum mixer; the slurry is then coated on a current collector copper foil, dried, and then cold pressed, striped, and cut into pieces to form a negative electrode sheet for a lithium ion battery. The compaction density of the negative electrode sheet is 1.6 g / cm 3 .

[0143] 3. Preparation of electrolyte

[0144] In an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, the non-aqueous solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed to obtain a mixed solvent, the additive FEC (fluoroethylene carbonate) was added to the mixed solvent, and finally the lithium salts LiFSI and LiPF6 were added and mixed and stirred until dissolved to complete the configuration of the electrolyte. Based on the total mass of the electrolyte, the mass proportion of EC was 18%, the mass proportion of EMC was 60%, the mass proportion of FEC was 5%, the mass proportion of LiFSI was 7%, and the mass proportion of LiPF6 was 10%.

[0145] 4. Isolation film

[0146] A polyethylene (PE) film with a thickness of 12 μm was used as the separator.

[0147] 5. Preparation of secondary batteries

[0148] Prepare the above-mentioned positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, then wind to obtain a bare battery cell, and weld the tabs; place the bare battery cell in an outer packaging shell, inject electrolyte after drying, and undergo vacuum packaging, standing, formation (charging the secondary battery at 0.1C constant current to 50% SOC), shaping and other processes to obtain a lithium-ion battery.

[0149] The preparation methods of the lithium-ion batteries of Examples 2-25 and Comparative Examples 1-2 are the same as those of Example 1, except that the processes for preparing the batteries are different, as shown in Table 1.

[0150] The thickness of the negative electrode sheets of each Example and Comparative Example was measured using a micrometer. Ten points were measured horizontally and vertically along the negative electrode sheet, and the average value was taken as the thickness. Comparing Examples 1-5 with Example 25 shows that the addition of silicon-based materials to the negative electrode sheet can reduce the coating thickness of the negative electrode active material layer on the negative electrode sheet, reducing the thickness of the negative electrode sheet while maintaining the same energy density, thereby effectively reducing the migration distance of lithium ions between the negative electrode active material layers. Furthermore, the greater the amount of silicon-based material added, the thinner the negative electrode sheet.

[0151] Table 1

[0152] It can be understood that the mass proportion of the compound represented by Formula 1 in Table 1 refers to the amount of the compound represented by Formula 1 added as a raw material. It has been determined that in the battery of Example 10, after formation, based on the total mass of the electrolyte, the mass proportion of the compound represented by Formula 1 is 1.4%, in the battery of Example 11, after formation, based on the total mass of the electrolyte, the mass proportion of the compound represented by Formula 1 is 2%, and in the battery of Example 13, after formation, based on the total mass of the electrolyte, the mass proportion of the compound represented by Formula 1 is 8%.

[0153] The batteries of Examples 1-25 and Comparative Examples 1-2 were subjected to low-temperature capacity retention tests and low-temperature cycle life tests. The test results are shown in Table 2.

[0154] (1) Low temperature capacity retention test:

[0155] At 25°C, discharge the battery at a constant current of 0.33C to 2.5V, then charge it at 0.33C to 3.65V. After standing for 10 minutes, discharge it at 0.33C to 2.5V. Record the discharge capacity, D1. Then, place the battery in a -10°C incubator and let it sit for 2 hours. Then, discharge it at a constant current of 0.33C to its full capacity, then charge it at 0.33C to 3.65V. After standing for 10 minutes, discharge it at 0.33C to 2.5V. Record the discharge capacity, D2. The battery's discharge capacity retention at -10°C is calculated as D2 / D1 × 100%.

[0156] (2) Low temperature cycle life test:

[0157] At -10°C, the battery was charged to 3.65V at a constant current of 0.2C, then charged at a constant voltage of 3.65V until the current dropped to 0.05C. After standing for 5 minutes, it was discharged to 2.5V at a constant current of 0.33C. This was the first charge / discharge cycle of the battery, and the discharge capacity at this time was recorded as the discharge capacity of the battery in the first cycle (C1). The above steps were repeated for the same battery, and the process capacity of the battery after the nth cycle (Cn) was recorded. The capacity retention rate after n cycles = Cn / C1×100%, and the cycle capacity retention rate when n = 300 was recorded.

[0158] Table 2

[0159] Conclusion: In Examples 1-25 of the present application, for the lithium iron phosphate material of the positive electrode, the additive shown in Formula 1 is added to the electrolyte and its content is controlled. During the battery production process, the adsorbed water in the battery pole piece is first released, which can promote the reaction of the additive shown in Formula 1 with the lithium salt in the electrolyte. The generated compound covers the surface of the lithium iron phosphate material particles, inhibiting the release of bound water in the lithium iron phosphate material during the subsequent use of the battery, and can alleviate the corrosion of the battery pole piece by the acid generated by the bound water entering the electrolyte, thereby improving the battery life at low temperatures.

[0160] Compared with Examples 1-25, in Comparative Example 1-2, the additive shown in Formula 1 is not added, or the content of the additive shown in Formula 1 is not within the scope of the present application, and the life of the battery at low temperatures is significantly reduced. It can be seen that the use of the additive of the present application and the control of its content can improve the life of the battery at low temperatures.

[0161] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery, wherein: include: A positive electrode plate, the positive electrode plate comprising a positive electrode active material, the positive electrode active material comprising a lithium iron phosphate material; An electrolyte, wherein the electrolyte includes an additive, wherein the additive includes: In Formula 1, X1, X2, X3 and X4 each independently include any one of H, F, fluorine-substituted or unsubstituted alkyl groups of 1-3 carbon atoms, and the mass proportion of the compound represented by Formula 1 is 2%-10% based on the total mass of the electrolyte.

2. The battery according to claim 1, wherein The lithium iron phosphate material includes LiMn x Fe 1-x-y M y PO4, wherein 0≤x≤1, 0≤y≤0.04, and M comprises at least one of Ti, Mg, Ta, Sc, Cr, Y, Zr, Nb, Mo, La, Ta, W, Hf, V, Ni, Rh, or Os.

3. The battery according to claim 1 or 2, wherein Based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 3%-8%.

4. The battery according to claim 1 or 2, wherein Based on the total mass of the electrolyte, the mass proportion of the compound represented by Formula 1 is 3%-10%.

5. The battery according to claim 1 or 2, wherein Based on the total mass of the electrolyte, the mass of the compound represented by Formula 1 accounts for 2%-8%.

6. The battery according to any one of claims 1 to 5, wherein The compound represented by Formula 1 includes at least one of fluoroethylene carbonate, bisfluoroethylene carbonate, 3,3,3-trifluoropropylene carbonate, or 4,4,5,5-tetrafluoro-1,3-dioxolane-2-one.

7. The battery according to any one of claims 1 to 6, wherein The battery further comprises a negative electrode plate, and the negative electrode plate comprises a silicon-based material.

8. The battery according to claim 7, wherein Based on the total mass of the negative electrode active material, the mass proportion of the silicon-based material is 2%-10%.

9. The battery according to claim 7 or 8, wherein Based on the total mass of the negative electrode active material, the mass proportion of the silicon-based material is 4%-8%.

10. The battery according to any one of claims 7 to 9, wherein The volume average particle size Dv50 of the silicon-based material is less than or equal to 6 μm.

11. The battery according to any one of claims 7 to 10, wherein The volume average particle size Dv50 of the silicon-based material is 1 μm-6 μm.

12. The battery according to any one of claims 1 to 11, wherein The electrolyte further includes a solvent, and the solvent includes ethylene carbonate. Based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate is 10%-25%.

13. The battery according to claim 12, wherein Based on the total mass of the electrolyte, the mass proportion of the ethylene carbonate is 15%-20%.

14. The battery according to claim 12 or 13, wherein The solvent further comprises at least one of propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, dipropyl carbonate, ethylpropyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate or γ-butyrolactone.

15. The battery according to any one of claims 1 to 14, wherein The electrolyte further includes a lithium salt, and the lithium salt includes lithium bis(fluorosulfonyl)imide.

16. The battery according to claim 15, wherein Based on the total mass of the electrolyte, the mass of the lithium bis(fluorosulfonyl)imide accounts for 3%-8%.

17. The battery according to claim 15 or 16, wherein Based on the total mass of the electrolyte, the mass of the lithium bis(fluorosulfonyl)imide accounts for 5%-8%.

18. The battery according to any one of claims 1 to 17, wherein The volume average particle size Dv50 of the positive electrode active material is 1 μm to 3 μm.

19. The battery according to any one of claims 1 to 18, wherein The compaction density of the positive electrode sheet is 2.3 g / cm 3 -2.8g / cm 3 .

20. An electrical device, wherein: A battery comprising the battery according to any one of claims 1 to 19.

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