Battery, battery apparatus, and electrical device

Abstract

A battery, a battery apparatus, and an electrical device. An electrolyte is used for the battery. The battery comprises an electrolyte and a negative electrode. The electrolyte comprises fluoroethylene carbonate. The negative electrode comprises a negative electrode active material. The negative electrode active material comprises silicon. The weight percentage of silicon in the negative electrode active material is x wt%, and the weight percentage of fluoroethylene carbonate in the electrolyte is b wt%, satisfying: 0.0872*x^2 - 0.0788*x + 0.5 ≤ b ≤ 0.412*x^1.46 + 0.5. By controlling the weight percentage b wt% of fluoroethylene carbonate in the electrolyte after formation and the weight percentage x wt% of silicon in the negative electrode to satisfy the above relationship, the battery can achieve a balance between energy density, cycling performance, and high-temperature storage performance.

Description

Batteries, battery devices and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202411209345.8, filed on August 30, 2024, entitled "Battery, Battery Device and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a battery, a battery device, and an electrical appliance. Background Technology

[0003] Secondary batteries have been widely used in recent years due to their advantages of high energy density, high operating voltage, long lifespan, and low self-discharge. To improve the energy density of a battery cell, the thickness of the electrode sheets is usually increased, thereby increasing the amount of active material per unit area and thus improving the energy density; alternatively, higher capacity active materials are used. For the latter, silicon, as a high-specific-capacity active material, is gradually being widely used.

[0004] However, due to the severe degradation of silicon materials during cycling, a matching electrolyte is required to ensure stable performance. Summary of the Invention

[0005] The purpose of this application is to provide a battery, battery device, and electrical equipment that balances battery energy density, cycle performance, and high-temperature storage performance.

[0006] To achieve the objectives of this application, the following technical solution is provided:

[0007] In a first aspect, this application provides a battery comprising an electrolyte and a negative electrode. The electrolyte comprises fluoroethylene carbonate, the negative electrode comprises a negative electrode active material, the negative electrode active material comprises silicon, the weight percentage of silicon in the negative electrode active material is x wt%, and the weight percentage of fluoroethylene carbonate in the electrolyte is b wt%, satisfying: 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5.

[0008] In one implementation, the following conditions are also met: 1.5 ≤ x ≤ 12.5; alternatively, the following conditions are also met: 3 ≤ x ≤ 7.5.

[0009] In one implementation, the following condition is also satisfied: 0.75≤b≤16; alternatively, the following condition is also satisfied: 1.05≤b≤7.

[0010] In one embodiment, the electrolyte includes a solvent, the solvent includes a cyclic organic compound, the cyclic organic compound includes the fluoroethylene carbonate, and the cyclic organic compound further includes ethylene carbonate and / or propylene carbonate.

[0011] In one embodiment, the solvent further includes a chain organic compound, which includes any one or a combination of ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.

[0012] In one embodiment, the weight of the cyclic organic compound is A, and the weight of the chain organic compound is B, satisfying: 1 / 4 ≤ A / B ≤ 2 / 3.

[0013] In one embodiment, the electrolyte further includes a lithium salt.

[0014] In one embodiment, the lithium salt is any one or a combination of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium sulfate, lithium difluorooxalate borate, lithium dioxalate borate, lithium bis(trifluoromethanesulfonate)imide, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium perchlorate, and lithium bis(fluorosulfonyl)imide.

[0015] In one embodiment, the concentration of the lithium salt is C, which satisfies: 0.8M ≤ C ≤ 1.2M.

[0016] In one embodiment, the electrolyte further includes any one or a combination of more of vinyl sulfite, propylene sulfite, and triargyl phosphate.

[0017] In one embodiment, the negative electrode includes a negative electrode current collector and a negative electrode material, the negative electrode material being loaded onto the negative electrode current collector, the negative electrode material including a binder, a conductive agent and the negative electrode active material, the negative electrode active material comprising 93%-96% by mass in the negative electrode material.

[0018] In one embodiment, the negative electrode active material includes a silicon-based negative electrode active material, which includes silicon oxide and / or silicon-carbon composite materials.

[0019] In one embodiment, the negative electrode active material further includes any one or a combination of graphite, hard carbon, soft carbon, and graphene.

[0020] Secondly, this application also provides a battery device, including a battery as described in any one of the various embodiments of the first aspect.

[0021] Thirdly, this application also provides an electrical device, including an electrical device and a battery as described in any one of the various embodiments of the first aspect or a battery device as described in the second aspect, wherein the battery or the battery device supplies power to the electrical device.

[0022] For batteries with the same silicon content in the negative electrode active material, by controlling the weight percentage b wt% of fluoroethylene carbonate in the electrolyte after formation and the weight percentage x wt% of silicon in the negative electrode active material to satisfy 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5, the battery can achieve a balance between energy density, cycle performance, and high-temperature storage performance. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0024] Figure 1 is a schematic diagram of a battery according to one embodiment;

[0025] Figure 2 is a flowchart of an embodiment of an electrolyte preparation method.

[0026] Explanation of reference numerals in the attached diagram: 100 - battery; 10 - negative electrode, 11 - negative electrode current collector, 12 - negative electrode material layer; 20 - positive electrode, 21 - positive electrode current collector, 22 - positive electrode material layer; 30 - separator. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0030] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] This application provides an electrical device, including an electrical device and a battery device in this application embodiment, wherein the battery device supplies power to the electrical device.

[0032] Optionally, the electrical device can be a pure electric vehicle, a hybrid electric vehicle, a base station, or a household electrical load. The battery device can be a battery pack, battery module, energy storage system, etc.

[0033] The electrical equipment uses the battery device described in the application embodiment, which balances energy density, cycle performance, and high-temperature storage performance.

[0034] This application also provides a battery device, including the battery described in this application embodiment. Optionally, the battery device includes multiple batteries. Each battery includes an electrode core and an electrolyte; the electrode core includes a positive electrode, a separator, and a negative electrode.

[0035] Optionally, batteries can be classified as stacked batteries or wound batteries based on the arrangement of the positive electrode, separator, and negative electrode in the core; in terms of battery shape, batteries can be square batteries or cylindrical batteries, etc., without limitation.

[0036] Optionally, the battery assembly also includes a housing, which comprises a base plate and multiple side plates connected to the base plate and enclosing a receiving cavity. The receiving cavity has an opening at one end opposite the base plate, and the battery is housed within the receiving cavity.

[0037] Optionally, the outer shell can be made of a material with high structural strength, specifically including metals, high-strength plastics, ceramics, carbon fiber, etc. Metals include aluminum, aluminum alloys, magnesium alloys, iron, and iron alloys. The outer shell can be a one-piece structure, meaning the base plate and side plates are manufactured using a single molding process, such as stamping or casting, without limitation. Alternatively, the outer shell can be a split structure, with the side plates and base plate connected and fixed by welding, bonding, snap-fitting, screwing, etc. The wall thickness of the outer shell can be approximately uniform throughout; that is, the side plates can have a roughly uniform thickness, and the base plate and side plates can also have roughly the same thickness.

[0038] Optionally, the battery assembly also includes a cover plate, which is attached to the opening in the housing to seal the cavity. The cover plate can be connected to the housing by welding, bonding, snap-fitting, screwing, etc., without limitation. The shape of the cover plate can be approximately the same as the base plate.

[0039] Optionally, the battery is a rechargeable battery. By employing the battery in the embodiments of this application, the battery device can achieve a balance between energy density, cycle performance, and high-temperature storage performance. In some embodiments of this application, the battery is a lithium-ion battery.

[0040] Referring to FIG. 1, an embodiment of the present application further provides a battery 100, which includes a negative electrode 10 and an electrolyte. The negative electrode 10 includes a negative electrode active material, and the negative electrode active material includes silicon element. In the negative electrode active material, the silicon element may exist in the form of a single substance or in the form of a compound.

[0041] Optionally, as shown in FIG. 1, the battery 100 further includes a positive electrode 20.

[0042] The positive electrode 20 includes a positive electrode current collector 21, and a positive electrode material layer 22 is provided on at least one side of the positive electrode current collector 21. The positive electrode material layer 22 includes components such as a positive electrode active material, a conductive agent, and a binder. The present application does not specifically limit these materials, and suitable materials can be selected according to actual application requirements. The positive electrode current collector 21 includes, but is not limited to, aluminum foil. The positive electrode active material may be a phosphate positive electrode active material and / or a transition metal oxide positive electrode active material. In specific embodiments, it includes lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadate phosphate, lithium titanate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, binary material LiNi k A (1-k) O2 (where A is selected from one of Co and Mn, 0 < k < 1), ternary material LiNi i E j M (1-i-j) O2 (where E and M are independently selected from at least one of Co, Al, and Mn, and E and M are different, 0 < i < 1, 0 < j < 1), or one or more of them. The conductive agent includes one or more of Super P, Super S, graphene, acetylene black, carbon fiber, Ketjen black, C60, and carbon nanotubes, and the content of the conductive agent in the positive electrode material layer 22 is 0.5 wt% - 5 wt%. The types of the binder include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives, and the content of the adhesive in the positive electrode material layer 22 is 2 wt% - 4 wt%.

[0043] The negative electrode 10 is a silicon-containing negative electrode 10 in this art. The negative electrode 10 includes a negative electrode current collector 11, with a negative electrode material loaded on at least one side of the negative electrode current collector 11 to form a negative electrode material layer 12. The negative electrode material layer 12 includes components such as a negative electrode active material, a conductive agent, and a binder. This application does not specifically limit these materials; suitable materials can be selected according to actual application requirements. In addition to silicon-based negative electrode active materials, the negative electrode active material may also include, but is not limited to, carbon-based negative electrode active materials. The carbon-based negative electrode active material may include any one or a combination of graphite, hard carbon, soft carbon, and graphene; the silicon-based negative electrode active material may include any one or a combination of silicon, silicon-carbon composite materials, silicon oxides, and silicon metal compounds. In some specific embodiments, the above-mentioned negative electrode active material is selected from at least one of silicon oxides and silicon-carbon composite materials. The silicon-carbon composite material includes porous carbon and silicon particles in the pores of the porous carbon. The silicon particles can be formed in the pores of the porous carbon by, for example, vapor deposition. Optionally, a conductive agent may be added to the negative electrode active material layer to improve the conductivity to the positive electrode active material. The conductive agent may include one or more of acetylene black, Ketjen black, Super P, Super S, carbon nanotubes, carbon nanofibers, activated carbon, and graphene. The negative electrode material layer 12 is composed of a negative electrode material, and in some embodiments, the negative electrode active material accounts for 93%-96% of the total mass.

[0044] Optionally, the battery 100 also includes a separator 30. The separator 30 can be any separator 30 known in the art. This application does not specifically limit these materials, and appropriate materials can be selected according to actual application needs.

[0045] There are several ways to improve the energy density of secondary batteries: one is to increase the thickness of the electrode, thereby increasing the amount of active material per unit area and thus improving the energy density; another is to use active materials with higher capacity. For the latter, silicon, as a high-capacity active material, is gradually being widely used.

[0046] However, due to the severe degradation of silicon materials during cycling, the development of suitable electrolytes is extremely important. A suitable electrolyte can enable batteries to balance energy density, cycle performance, and high-temperature storage performance.

[0047] The battery in this embodiment of the application, by employing a silicon-containing negative electrode and the electrolyte in this embodiment of the application, enables the battery to balance energy density, cycle performance and high-temperature storage performance.

[0048] This application provides a battery comprising an electrolyte and a negative electrode. The electrolyte comprises fluoroethylene carbonate, and the negative electrode comprises a negative electrode active material comprising silicon, satisfying: 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5.

[0049] x wt% represents the weight percentage of silicon in the negative electrode active material, and b wt% represents the weight percentage of fluoroethylene carbonate in the electrolyte. Optionally, b wt% represents the weight percentage of fluoroethylene carbonate in the electrolyte of the formed battery. 0.0872*x^2 - 0.0788*x + 0.5 ≤ b ≤ 0.412*x^1.46 + 0.5, i.e., 0.0872x 2 -0.0788x + 0.5 ≤ b ≤ 0.412x 1.46 +0.5.

[0050] Fluorinated ethylene carbonate (FEC) is crucial for the cycle performance of silicon. FEC forms a protective film on the surface of silicon particles, accommodating the volume expansion and contraction of silicon during charge and discharge, thereby reducing silicon pulverization and interfacial side reactions. Furthermore, FEC can immediately repair damaged interfaces, thus providing good cycle performance for the silicon system. However, at high temperatures and under the catalysis of lithium hexafluorophosphate, FEC easily decomposes and releases HF gas, leading to significant high-temperature degradation of the battery, particularly affecting gas production and storage capacity. Therefore, controlling the amount of FEC used is essential. A reasonable amount of FEC can ensure good battery cycle performance while maintaining high-temperature storage performance.

[0051] In this application, for batteries with the same silicon content in the negative electrode active material, by controlling the weight percentage b wt% of fluoroethylene carbonate in the electrolyte after formation and the weight percentage x wt% of silicon in the negative electrode to satisfy 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5, it is possible to ensure good energy density and cycle performance of the battery while maintaining its high-temperature storage performance. For example, for batteries with a silicon content of a wt% in the same negative electrode active material, batteries with a fluoroethylene carbonate weight percentage b wt% that satisfy 0.0872*a^2-0.0788*a+0.5≤b≤0.412*a^1.46+0.5 can better balance good energy density, cycle performance, and high-temperature storage performance compared to batteries that do not satisfy 0.0872*a^2-0.0788*a+0.5≤b≤0.412*a^1.46+0.5.

[0052] Optional, 1.5≤x≤12.5.

[0053] Optionally, the weight percentage (wt%) of silicon in the negative electrode can be 1.5wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7.5wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 12.5wt%, etc. Because silicon undergoes significant volume expansion and contraction during charging and discharging, the higher the silicon content, the more pronounced the volume change effect. Therefore, an excessively high weight percentage (wt%) of silicon in the negative electrode may lead to the cracking or pulverization of particles inside the electrode, thereby compromising the integrity of the electrode structure. Due to the damage to the electrode structure, the initially inserted lithium is more likely to lose activity in these damaged areas, causing irreversible reactions inside the electrode and resulting in a decline in battery performance. When the silicon content in the negative electrode is too high, it may cause a significant capacity decay in the first few battery cycles.

[0054] If the weight percentage (wt%) of silicon in the negative electrode active material is too low, the capacity of the negative electrode will decrease, failing to meet the requirements of high-energy-density batteries. Higher silicon content will also lead to decreased cycle stability and shortened battery life.

[0055] By controlling the weight percentage (x wt%) of silicon in the negative electrode active material to satisfy 1.5 ≤ x ≤ 12.5, good cycle performance of the battery can be guaranteed while meeting the requirements of high energy density batteries. Optionally, x satisfies: 3 ≤ x ≤ 7.5.

[0056] Optionally, 0.75 ≤ b ≤ 16; alternatively, it also satisfies: 1.05 ≤ b ≤ 7.

[0057] Optionally, the electrolyte includes a solvent, which includes a cyclic organic compound. In addition to the aforementioned fluoroethylene carbonate (FEC), the cyclic organic compound also includes ethylene carbonate (EC) and / or propylene carbonate (PC).

[0058] Optionally, the cyclic organic compound may include ethylene carbonate in addition to fluoroethylene carbonate; or, in addition to fluoroethylene carbonate, it may include propylene carbonate; or, in addition to fluoroethylene carbonate, it may include both ethylene carbonate and propylene carbonate. All of the above are acceptable and there is no specific limitation.

[0059] Cyclic organic compounds can dissolve lithium salts, helping to form a stable electrolyte system with good chemical stability, which helps extend the electrolyte's lifespan. PC (polycarbonate) exhibits excellent high and low temperature performance and anti-gas-swelling properties, improving the battery's high-temperature storage performance and capacity retention.

[0060] Optionally, the solvent may also include a chain organic compound, which is any one or a combination of more of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0061] Optionally, the chain organic compound in the solvent may be any one of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC); or, the chain organic compound in the solvent may include any two of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), with no limitation on the ratio of the two; or, the chain organic compound in the solvent may include ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). All of the above methods are acceptable and there is no specific limitation.

[0062] Chain carbonates (such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC)) have lower viscosity and better electrochemical stability than cyclic carbonates, thus improving the low-temperature performance and kinetic performance of electrolytes.

[0063] By including chain organic compounds in the solvent, such as any one or a combination of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), the electrochemical stability and low-temperature performance of the electrolyte can be improved.

[0064] Optionally, the weight of the cyclic organic compound is A, and the weight of the chain organic compound is B, satisfying: 1 / 4 ≤ A / B ≤ 2 / 3.

[0065] Optionally, the weights A of the cyclic organic compound and B of the chain organic compound satisfy: 1 / 4 ≤ A / B ≤ 3 / 7.

[0066] Specifically, the values ​​of A / B can be 1 / 4, 9 / 28, 5 / 14, 11 / 28, 3 / 7, etc., with no specific restrictions.

[0067] Cyclic and chain organic compounds possess different properties as solvent components in electrolytes. Chain organic compounds exhibit lower viscosity and better electrochemical stability, which helps improve the low-temperature performance and kinetic properties of the electrolyte. Cyclic organic compounds, on the other hand, have higher dielectric constants, which helps improve the ion-conducting capacity of the electrolyte. Therefore, by adjusting the ratio of chain and cyclic solvents, the performance of the electrolyte can be balanced to meet the needs of different batteries.

[0068] Optionally, the electrolyte may also include lithium salts.

[0069] Optionally, the lithium salt is any one or a combination of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium sulfate (Li2SO4), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium bis(trifluoromethanesulfonate) imide (LiTFSI), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiTFA or LiOTF), lithium perchlorate (LiClO4), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0070] Optionally, the lithium salt can also be other lithium salts commonly used in the art, without limitation.

[0071] In one embodiment, the lithium salt is lithium hexafluorophosphate (LiPF6).

[0072] As the main source of lithium ions in the electrolyte, lithium salts ensure that there are enough lithium ions to be transported during the charging and discharging process of the battery. At the same time, lithium salts can form a stable solution system with the solvent, providing a transport pathway for lithium ions and enabling stable charging and discharging of the battery. In addition, the anionic groups of lithium salts can also participate in the formation of films on the positive and negative electrodes, further improving the battery's lifespan.

[0073] Optionally, the concentration of the lithium salt is C, which satisfies: 0.8M≤C≤1.2M, where M represents moles per cubic decimeter.

[0074] Optionally, the concentration C of the lithium salt satisfies: 0.9M ≤ C ≤ 1.1M.

[0075] Specifically, the value of C can be 0.9M, 1M, 1.1M, etc., without any restrictions.

[0076] An appropriate concentration of lithium salt ensures sufficient lithium ions are transported in the electrolyte, thus maintaining good battery performance. If the lithium salt concentration is too low, lithium ion transport may be hindered, resulting in excessive concentration polarization of the electrolyte at high rates, reducing the battery's charge-discharge capability at high rates. On the other hand, if the concentration is too high, it may increase the viscosity of the electrolyte, which also increases the resistance to lithium ion diffusion in the electrolyte, causing a significant loss in the battery's ability to charge and discharge at high rates.

[0077] By setting the lithium salt concentration C to satisfy 0.8M≤C≤1.2M, the battery's performance, cycle life, and safety can be guaranteed.

[0078] Optionally, the electrolyte may also include additives.

[0079] Additives in electrolytes can improve the performance of the SEI film on the surface of the negative electrode active material, and can also change the physical properties of the electrolyte such as ionic conductivity and viscosity, which helps to optimize the electrochemical performance of the electrolyte and improve its electrochemical stability.

[0080] Optionally, the additive may be any one or a combination of more of vinyl sulfate (DTD), propylene sulfite (PS), and tripropionyl phosphate (TPP).

[0081] Optionally, the additive may be any one of vinyl sulfate (DTD), propylene sulfite (PS), and triargyl phosphate (TPP); or, the additive may be a combination of any two of vinyl sulfate (DTD), propylene sulfite (PS), and triargyl phosphate (TPP), with no specific limitation on the ratio of the two; or, the additive may include vinyl sulfate (DTD), propylene sulfite (PS), and triargyl phosphate (TPP). All of the above methods are acceptable and there are no specific limitations.

[0082] Optionally, the additive may also be other commonly used additives in the field, without limitation.

[0083] By setting the additives to be any one or a combination of ethylene sulfate (DTD), propylene sulfite (PS), and tripropionyl phosphate (TPP), the stability of the SEI and CEI films formed by the electrolyte during the formation stage can be improved.

[0084] Please refer to Figure 2. This application embodiment also provides a method for preparing an electrolyte, including:

[0085] Step S10, providing a solvent, the solvent including fluoroethylene carbonate, satisfying:

[0086] 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5,

[0087] x wt% represents the weight percentage of silicon in the negative electrode active material, and b wt% represents the weight percentage of fluoroethylene carbonate in the electrolyte.

[0088] Formation refers to the process of activating the positive and negative electrode materials inside a battery after it has been manufactured, through a certain charging and discharging method, in order to improve the overall performance of the battery.

[0089] By controlling the weight percentage b wt% of fluoroethylene carbonate in the electrolyte after formation and the weight percentage x wt% of silicon in the negative electrode to satisfy 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5, it is possible to ensure good energy density and cycle performance of the battery while maintaining its high-temperature storage performance.

[0090] In one embodiment, a solvent is provided, and the solvent further includes:

[0091] The invention provides cyclic organic compounds, including fluoroethylene carbonate, and further includes ethylene carbonate and / or propylene carbonate.

[0092] By incorporating cyclic organic compounds into the solvent, which includes ethylene carbonate, ethylene carbonate, and / or propylene carbonate in addition to fluoroethylene carbonate, a stable electrolyte system can be formed, exhibiting good high and low temperature performance and anti-gas expansion function, thereby improving battery capacity and cycle life.

[0093] In one embodiment, a solvent is provided, and the solvent further includes:

[0094] Provides a chain-like organic compound, wherein the chain-like organic compound is any one or a combination of more than one of methyl ethyl carbonate, dimethyl carbonate and diethyl carbonate;

[0095] Cyclic organic compounds and chain organic compounds are mixed.

[0096] Optionally, in one embodiment, the cyclic organic compound includes ethylene carbonate (EC) and fluoroethylene carbonate (FEC), and the chain organic compound includes ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), and the four are mixed in a weight ratio of ethylene carbonate (EC): fluoroethylene carbonate (FEC): chain organic compound including ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 25:5:60:10.

[0097] The solvent also includes chain organic compounds, which have lower viscosity and better electrochemical stability, helping to improve the kinetic performance of the electrolyte. Meanwhile, cyclic organic compounds help to increase the dissociation degree of lithium salt and enhance the ion transport capacity of the electrolyte. The combination of the two can balance the performance of the electrolyte to meet the needs of different batteries.

[0098] In one embodiment, it further includes:

[0099] Step S20: Add lithium salt to the solvent.

[0100] Optionally, the concentration of the lithium salt is C, which satisfies: 0.8M≤C≤1.2M.

[0101] In one embodiment, the lithium salt is lithium hexafluorophosphate (LiPF6), and the concentration of the lithium salt is 1M.

[0102] By adding lithium salt to the solvent, an appropriate concentration of lithium salt can ensure that there are enough lithium ions to be transported in the electrolyte, thereby maintaining the high efficiency of the battery.

[0103] In one embodiment, it further includes:

[0104] Step S30: Add additives to the solvent.

[0105] In one embodiment, 1 wt% of vinyl sulfate (DTD) is added to the solvent as an additive.

[0106] Adding additives to the solvent can improve the performance of the SEI film on the surface of the negative electrode active material, and also help optimize the electrochemical performance of the electrolyte and improve its electrochemical stability.

[0107] Optionally, steps S20 and S30 can be performed sequentially or simultaneously, without limitation. In one embodiment, as shown in Figure 2, step S20 is performed first, where lithium salt is added to the solvent and dissolved. Then, step S30 is performed, where additives are added to the solvent to complete the preparation of the electrolyte. In another embodiment, lithium salt and additives can be added to the solvent simultaneously and mixed to prepare the electrolyte, without limitation.

[0108] The technical solution of this application will be described in detail below through specific embodiments. Unless otherwise specified, materials with the same name in the following different embodiments / comparative examples have the same composition.

[0109] Example 1

[0110] This embodiment provides a battery, an electrolyte, and a method for preparing the same. The battery includes a negative electrode and an electrolyte; the negative electrode comprises silicon, and the electrolyte comprises fluoroethylene carbonate.

[0111] The preparation method of this negative electrode includes the following steps:

[0112] (1) Graphite, silicon-carbon composite material (silicon content 50wt%, purchased from Luoyang Lianchuang), conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber emulsion), and adhesive PAA (polyacrylic acid) were prepared into a slurry in a weight ratio of 97:3:1.5:0.8:0.7:2, wherein the weight percentage of silicon in the negative electrode active material (graphite and silicon-carbon composite material) was 1.5wt%, i.e., x = 1.5.

[0113] (2) After the mixed slurry is coated on both sides of the copper foil, it is dried at 85°C and then cold-pressed.

[0114] (3) Trim the edges, cut the pieces, and slit them. After slitting, dry them at 85°C for 4 hours under vacuum conditions, and then weld the tabs to obtain the negative electrode.

[0115] The preparation method of this electrolyte includes the following steps:

[0116] (a) Mix ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a weight ratio of 26.75:3.25:60:10.

[0117] (b) Add 1M lithium hexafluorophosphate (LiPF6) to the mixed solvent and dissolve it.

[0118] (c) Add 1 wt% vinyl sulfate (DTD) to a solvent to obtain an electrolyte.

[0119] Example 2

[0120] The difference between this and Example 1 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 26.5:3.5:60:10.

[0121] Example 3

[0122] The difference between this and Example 1 is that the weight ratio of graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber emulsion), and adhesive PAA in the negative electrode is 90:10:1.5:0.8:0.7:2, and the weight percentage of silicon in the negative electrode active material is 5wt%, i.e., x = 5.

[0123] The weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 24:6:60:10.

[0124] Example 4

[0125] The difference between this and Example 3 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 22:8:60:10.

[0126] Example 5

[0127] The difference between this and Example 3 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 21:9:60:10.

[0128] Example 6

[0129] The difference between this and Example 1 is that the weight ratio of graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber latex), and adhesive PAA in the negative electrode is 85:15:1.5:0.8:0.7:3, and the weight percentage of silicon in the negative electrode active material is 7.5wt%, i.e., x = 7.5.

[0130] The weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 20:10:60:10.

[0131] Example 7

[0132] The difference between this and Example 6 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 18:12:60:10.

[0133] Example 8

[0134] The difference between this and Example 6 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 17:13:60:10.

[0135] Example 9

[0136] The difference between this and Example 1 is that the weight ratio of graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber emulsion), and adhesive PAA in the negative electrode is 75:25:1.5:1:1.5:4, and the weight percentage of silicon in the negative electrode active material is 12.5wt%, i.e., x = 12.5.

[0137] The weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 10:20:60:10.

[0138] Example 10

[0139] The difference between this and Example 9 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 8:22:60:10.

[0140] Example 11

[0141] The difference between this and Example 1 is that the weight ratio of graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber latex), and adhesive PAA in the negative electrode is 98:2:1.5:0.8:0.7:2.

[0142] The weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 28:2:60:10.

[0143] Example 12

[0144] The difference between this and Example 1 is that the weight ratio of graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber latex), and adhesive PAA in the negative electrode is 70:30:1.5:1:1.5:4.

[0145] Example 13

[0146] The difference between this and Example 1 is that graphite, silicon-carbon composite material, conductive agent SuperP, thickener CMC (sodium carboxymethyl cellulose), binder SBR (styrene-butadiene rubber emulsion), and adhesive PAA (polyacrylic acid) are prepared into a slurry in a weight ratio of 97:3:3:0.8:1.2:2, wherein the weight percentage of silicon in the negative electrode active material (graphite and silicon-carbon composite material) is 1.5wt%, i.e., x = 1.5.

[0147] Comparative Example 1

[0148] The difference between this and Example 3 is that the weight ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 30:60:10.

[0149] Comparative Example 2

[0150] The difference between this and Example 1 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 27:3:60:10.

[0151] Comparative Example 3

[0152] The difference between this and Example 1 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 26:4:60:10.

[0153] Comparative Example 4

[0154] The difference between this and Example 3 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 25:5:60:10.

[0155] Comparative Example 5

[0156] The difference between this and Example 3 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 18:12:60:10.

[0157] Comparative Example 6

[0158] The difference between this and Example 6 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 25:5:60:10.

[0159] Comparative Example 7

[0160] The difference between this and Example 6 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 15:15:60:10.

[0161] Comparative Example 8

[0162] The difference between this and Example 9 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 15:15:60:10.

[0163] Comparative Example 9

[0164] The difference between this and Example 9 is that the weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 5:25:60:10.

[0165] The weight ratio of ethylene carbonate (EC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in the electrolyte is 5:25:60:10.

[0166] The battery also includes a positive electrode and a separator. The preparation process of the positive electrode is as follows: lithium nickel cobalt manganese oxide (NCM811), conductive agent Super P, binder PVDF, and carbon nanotubes (CNTs) are mixed evenly in a weight ratio of 95:2.3:2:0.7 to form a positive electrode slurry. The positive electrode slurry is then coated on both sides of an aluminum foil with a coating amount of 30 g / m². 2 After drying and rolling, the positive electrode is obtained.

[0167] Separator: Made of polypropylene (PP) ceramic film.

[0168] The positive electrode prepared according to the above process, the negative electrode and separator provided in the above examples and comparative examples, and the battery were stacked to form a battery with a thickness of 4.7 mm, a width of 55 mm, and a length of 60 mm. The battery was then vacuum-baked at 75°C for 10 hours, and the electrolyte provided in the above examples and comparative examples was injected at an injection coefficient of 2.2 Ah / g to complete battery assembly, followed by formation and capacity testing. The specific conditions for formation and capacity testing are as follows:

[0169] Formation: After standing at 45°C for 2 hours, charge at a constant current of 0.02C for 2 hours, then charge at a constant current of 0.05C for 2 hours, and then charge at a constant current of 0.1C for 5 hours to complete the formation.

[0170] Capacity grading: Charge the battery to 4.25V at a constant current and constant voltage of 1 / 3C, and cut off at 0.05C; after resting for 30 minutes, discharge the battery to 2.5V at a constant current of 1 / 3C to complete the capacity grading and obtain the battery to be tested.

[0171] The electrochemical performance of the above-mentioned battery was tested under the following conditions:

[0172] 25℃, 1.0C / 1.0C ambient temperature cycling test: At 25℃, charge at a constant current of 1.0C to 4.25V, charge at a constant voltage of 4.25V to the cutoff current of 0.05C, and then discharge the battery at a constant current of 1.0C to 2.5V. The discharge capacity is recorded as C0. Repeat the charge and discharge cycle to obtain the discharge capacity Cn of the nth cycle. The capacity retention rate is (Cn / C0)*100%. Record the number of cycles n when the capacity retention rate reaches 80%.

[0173] Gas production test after 28 days of storage at 60℃: After the battery is cycled 3 times at a charge-discharge rate of 1C (charge-discharge voltage range of 2.5V-4.25V), the initial volume is V1; after being stored at 60℃ for 28 days in a fully charged state, the volume obtained by water displacement test is V2; gas production = (V2-V1) / C0.

[0174] Energy density per unit weight test: At 25℃, charge at a constant current of 1 / 3C to 4.25V, then charge at a constant voltage of 4.25V to the cutoff current of 0.05C, and then discharge the battery at a constant current of 1 / 3C to 2.5V. Repeat this process 3 times. The discharge capacity of the third discharge is recorded as C. BOL The corresponding discharge energy is W Wh, the weight of the battery is m kg, and the energy density of the cell is W / m, with the unit being Wh / kg.

[0175] The test results are shown in Table 1 below. The weight percentage of fluoroethylene carbonate (b wt%) in the electrolyte after formation in the above embodiments, the weight percentage of silicon (x wt%) in the negative electrode active material, the range of the weight percentage of fluoroethylene carbonate (b wt%) in the electrolyte corresponding to the inequality 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5, and whether each embodiment satisfies 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.5 are shown in Table 2 below.

[0176] Table 1

[0177] Table 2

[0178] As can be seen from the test results of Examples 1 to 13 and Comparative Example 1 in Tables 1 and 2, adding fluoroethylene carbonate (FEC) to the electrolyte composition can effectively improve the cycle performance of the battery.

[0179] From the test results of Examples 1 to 13 and Comparative Examples 2 to 9 in Tables 1 and 2, it can be seen that for examples and comparative examples with the same weight percentage (x wt%) of silicon in the negative electrode, the examples whose weight percentage (b wt%) of FEC in the electrolyte after formation satisfies the relationship 0.0872*x^2 - 0.0788*x + 0.5 ≤ b ≤ 0.412*x^1.46 + 0.5 have more cycles to 80% capacity retention compared to the comparative examples with a smaller range, indicating that the examples satisfying the relationship range have better cycle retention performance. Furthermore, the examples satisfying the relationship range have less gas generation compared to the comparative examples with a larger range, indicating that the examples have better gas storage performance. This shows that controlling the amount of fluoroethylene carbonate in the electrolyte within a suitable range can enable the battery to have both good cycle performance and good gas storage performance.

[0180] In the description of the embodiments of this application, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0181] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. A battery (100), characterized in that, The device includes an electrolyte and a negative electrode (10). The electrolyte includes fluoroethylene carbonate, and the negative electrode (10) includes a negative electrode active material. The negative electrode active material includes silicon, and the weight percentage of silicon in the negative electrode active material is x wt%. The weight percentage of fluoroethylene carbonate in the electrolyte is b wt%, satisfying: 0.0872*x^2-0.0788*x+0.5≤b≤0.412*x^1.46+0.

5.

2. The battery (100) according to claim 1, characterized in that, 1.5≤x≤12.5; optionally, 3≤x≤7.

5.

3. The battery (100) according to claim 1 or 2, characterized in that, 0.75≤b≤16; optionally, 1.05≤b≤7.

4. The battery (100) according to any one of claims 1-3, characterized in that, The electrolyte includes a solvent, which includes a cyclic organic compound, including the fluoroethylene carbonate, and further includes ethylene carbonate and / or propylene carbonate.

5. The battery (100) according to claim 4, characterized in that, The solvent also includes chain organic compounds, which include any one or a combination of methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate.

6. The battery (100) according to claim 5, characterized in that, The weight of the cyclic organic compound is A, and the weight of the chain organic compound is B, satisfying: 1 / 4 ≤ A / B ≤ 2 / 3.

7. The battery (100) according to any one of claims 1-6, characterized in that, The electrolyte also includes lithium salt.

8. The battery (100) according to claim 7, characterized in that, The lithium salt includes any one or a combination of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium sulfate, lithium difluorooxalate borate, lithium dioxalate borate, lithium bis(trifluoromethanesulfonate)imide, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium perchlorate, and lithium bis(fluorosulfonylimide).

9. The battery (100) according to claim 7 or 8, characterized in that, The concentration of the lithium salt is C, which satisfies: 0.8M≤C≤1.2M.

10. The battery (100) according to any one of claims 1-9, characterized in that, The electrolyte also includes any one or a combination of vinyl sulfate, propylene sulfite, and triargyl phosphate.

11. The battery (100) according to any one of claims 1-10, characterized in that, The negative electrode (10) includes a negative electrode current collector (11) and a negative electrode material. The negative electrode material is loaded on the negative electrode current collector (11). The negative electrode material includes a binder, a conductive agent and the negative electrode active material. The negative electrode active material accounts for 93%-96% of the mass of the negative electrode material.

12. The battery (100) according to any one of claims 1-11, characterized in that, The negative electrode active material includes a silicon-based negative electrode active material, which includes silicon oxide and / or silicon-carbon composite materials.

13. The battery (100) according to any one of claims 1-12, characterized in that, The negative electrode active material also includes any one or a combination of graphite, hard carbon, soft carbon, and graphene.

14. A battery device, characterized in that, Includes the battery (100) as described in any one of claims 1-13.

15. An electrical appliance, characterized in that, It includes an electrical device and a battery (100) as claimed in any one of claims 1-13 or a battery device as claimed in claim 14, wherein the battery (100) or the battery device supplies power to the electrical device.

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