Cylindrical lithium-ion battery

Abstract

The present application relates to the technical field of lithium-ion batteries, and specifically relates to a cylindrical lithium-ion battery having improved high-temperature storage performance and high-temperature cycle performance. The cylindrical lithium-ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte solution, wherein the negative electrode comprises a negative electrode material layer containing a negative electrode active material, the negative electrode active material comprising a silicon-based material; and the non-aqueous electrolyte solution comprises a lithium salt, an organic solvent and an additive, the organic solvent comprising dimethyl carbonate, and the additive comprising a silane compound represented by structural formula 1. The cylindrical lithium-ion battery satisfies the following condition: 0.04≤(100-D)×F / S≤5, wherein 50≤D≤75, 0.01≤F≤0.5, and 5≤S≤20. In the cylindrical lithium-ion battery of the present application, the electrolyte solution contains the silane compound represented by structural formula 1 as an additive and dimethyl carbonate as the organic solvent, and therefore the problem of battery failure caused by the expansion of the silicon-based negative electrode can be improved, the service life of the battery can be prolonged, the battery is ensured to have good high-temperature performance, and the effect of inhibiting gas production during high-temperature storage is obvious.

Description

A cylindrical lithium-ion battery Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a cylindrical lithium-ion battery with improved high-temperature storage and optimized high-temperature cycle performance. Background Art

[0002] Lithium-ion batteries have a broad application market in the fields of new energy vehicles and large-scale energy storage due to their advantages such as high operating voltage, wide operating temperature range, high energy density, high output power, no memory effect and long cycle life. Cylindrical batteries are particularly popular due to their simple design, standard manufacturing, simple process, low cost and strong application flexibility. Traditional cylindrical batteries do not have an advantage as power batteries due to their small size. To solve this problem, the size of existing cylindrical batteries is getting larger and larger. The diameter of cylindrical batteries has increased to 46mm, which has further increased the energy density of cylindrical battery cells. Because the pole pieces of cylindrical batteries are wound in a winding design, the pole pieces are bound by the winding tension after being wound layer by layer, which can effectively suppress the expansion of the pole pieces. They are more suitable for silicon negative electrodes that expand greatly after charging and discharging. The cell design of cylindrical batteries is suitable for high energy density material systems.

[0003] Silicon-containing anodes experience a significant volume effect. The lithium-silicon alloying and dealloying processes are accompanied by dramatic expansion and contraction of the anode, causing the solid electrolyte interface (SEI) film on its surface to constantly rupture and regenerate, leading to electrolyte consumption and loss of active lithium. This increases interfacial impedance, thus deteriorating cycle performance. Furthermore, as charge and discharge progress, the thickness of the anode plate increases, squeezing the battery's protective casing, potentially causing it to rupture and pose a safety hazard. Furthermore, the increased thickness impairs contact between the active material and the copper foil current collector, affecting electronic conductivity and causing a sharp decline in battery capacity in the later stages of the cycle, resulting in a "diving" phenomenon.

[0004] Currently, the industry's approach to increasing the energy density of cylindrical batteries is mostly achieved by using high-capacity cathode and anode materials. Silicon-based anodes have a theoretical capacity approximately 10 times that of currently used graphite anodes. Therefore, increasing the silicon content in the anode material of battery cells is a key development direction for achieving higher energy density. For every 10% increase in energy density, cycle life decreases by 25%. Battery cells made with high-energy-density materials suffer from a cycle life shortcoming, making it difficult to increase the cycle life of existing cylindrical batteries while maintaining high energy density.

[0005] Therefore, it is necessary to develop a cylindrical lithium ion battery to solve the above problems existing in the prior art.

[0006] Application Contents

[0007] In order to solve the above technical problems, the present application provides a cylindrical lithium-ion battery with improved high-temperature storage performance and high-temperature cycle performance.

[0008] This application adopts the following technical solutions:

[0009] A cylindrical lithium-ion battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte; the negative electrode comprises a negative electrode material layer containing a negative electrode active material, and the negative electrode active material comprises a silicon-based material;

[0010] The non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, wherein the organic solvent includes dimethyl carbonate, and the additive includes a silane compound shown in structural formula 1:

[0011] wherein R1, R2, R3 and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl and substituted or unsubstituted C2-C5 alkynyl, and at least one of R1-R4 is selected from substituted or unsubstituted C2-C5 alkenyl;

[0012] The cylindrical lithium-ion battery meets the following conditions:

[0013] 0.04≤(100-D)×F / S≤5, and 50≤D≤75, 0.01≤F≤0.5, 5≤S≤20;

[0014] Wherein, D is the mass percentage of dimethyl carbonate in the non-aqueous electrolyte, in wt%;

[0015] F is the mass percentage of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, in wt%;

[0016] S is the mass percentage of silicon element in the negative electrode material layer, in wt%.

[0017] The negative electrode of the present application adopts silicon-based materials, which can effectively improve the energy density of the battery; however, the huge volume effect of silicon-based materials cannot be ignored, especially as the silicon content increases, this negative effect will increase exponentially, and the high-strength shell of the cylindrical battery can, to a certain extent, inhibit the damage of the volume expansion of the silicon-based material to the battery body; and the stability of the silicon-based material negative electrode is insufficient, and the side reactions are more numerous and violent than other systems, while the silane compound shown in Structural Formula 1 contains an olefin group with an unsaturated carbon-carbon double bond, which can absorb unstable free radicals in the electrolyte and reduce side reactions; it can also form a film at the positive electrode to protect the battery with good high-temperature performance and inhibit high-temperature gas production. Cylindrical batteries are tightly wound structures with compact material structures and relatively small internal spaces. The premise for the electrolyte to work effectively is good wetting and fluidity. The viscosity of chain carbonates is lower than that of cyclic carbonates. Among the commonly used organic solvents, dimethyl carbonate has the lowest viscosity and the best effect on improving conductivity. The applicant, based on his own experience and extensive research, found that when dimethyl carbonate is used as the organic solvent for cylindrical batteries, and the mass percentage of dimethyl carbonate in the non-aqueous electrolyte, the mass percentage of the silane compound shown in structural formula 1 in the non-aqueous electrolyte, and the mass percentage of silicon element in the negative electrode material layer are controlled to meet 0.04≤(100-D)×F / S≤5, and 50≤D≤75, 0.01≤F≤0.5, 5≤S≤20, the battery failure problem caused by the expansion of the silicon-based negative electrode can be improved, and the battery life can be improved; and the battery can be ensured to have good high-temperature performance, and the effect of suppressing gas production during high-temperature storage is obvious.

[0018] Specifically, the value of (100-D)×F / S can be, but is not limited to, 0.04, 0.06, 0.08, 0.1, 1.2, 1.5, 1.8, 2, 2.2, 2.4, 2.5, 2.7, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.7, 4.8, 5; preferably, the value of (100-D)×F / S is 0.1 to 3, which can better improve the high temperature storage capacity and optimize the high temperature cycle performance of the lithium-ion battery.

[0019] In some specific embodiments of the present application, dimethyl carbonate is used as an organic solvent. Due to its low viscosity, it is more suitable for use in a cylindrical tightly wound structure, which can greatly improve the wettability and fluidity of the non-aqueous electrolyte and has a good effect on improving the conductivity. Specifically, the mass percentage D of the dimethyl carbonate in the non-aqueous electrolyte can be, but is not limited to, 50wt%, 52wt%, 55wt%, 57wt%, 59wt%, 60wt%, 62wt%, 64wt%, 65wt%, 67wt%, 70wt%, 72wt%, 73wt%, 75wt% or any range consisting of the above values; preferably, the mass percentage D of the dimethyl carbonate in the non-aqueous electrolyte is 55wt% to 67wt%.

[0020] In some specific embodiments of the present application, the silane compound shown in structural formula 1 contains an unsaturated carbon-carbon double bond, which can absorb unstable free radicals in the electrolyte, reduce side reactions caused by insufficient stability of silicon-based negative electrode materials, gain electrons on the negative electrode surface to generate organic carbonates to protect the negative electrode, and at the same time form a film on the positive electrode to ensure that the battery has good high-temperature performance, and the effect of inhibiting gas production during high-temperature storage is obvious. Specifically, the mass percentage F of the silane compound represented by the structural formula 1 in the non-aqueous electrolyte may be, but is not limited to, 0.01wt%, 0.02wt%, 0.03wt%, 0.05wt%, 0.07wt%, 0.09wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.16wt%, 0.18wt%, 0.2wt%, 0.24wt%, 0.25wt%, 0.27wt%, 0.3wt%, 0.35wt%, 0.38wt%, 0.4wt%, 0.42wt%, 0.45wt%, 0.48wt%, 0.5wt% or any range consisting of the above values; preferably, the mass percentage F of the silane compound represented by the structural formula 1 in the non-aqueous electrolyte is 0.01wt% to 0.3wt%.

[0021] In some specific embodiments of the present application, the silane compound represented by Structural Formula 1 contains at least one alkenyl group. The more unsaturated carbon-carbon double bonds there are, the better the absorption effect on unstable free radicals in the electrolyte. Preferably, in the silane compound represented by Structural Formula 1, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C5 alkenyl groups and substituted or unsubstituted C2-C5 alkynyl groups; more preferably, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C5 alkenyl groups.

[0022] Specifically, in some embodiments of the present application, the silane compound represented by Structural Formula 1 includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethylsilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane, and divinyldipropylsilane. More preferably, the silane compound represented by Structural Formula 1 is tetravinylsilane.

[0023] In some specific embodiments of the present application, the silicon-based material includes at least one of a silicon material, a silicon oxide material, a silicon-carbon material, and a silicon alloy material.

[0024] In some preferred embodiments of the present application, the silicon material is a nano-silicon material.

[0025] In some preferred embodiments of the present application, the silicon oxide material is SiO xMaterials, where 0≤x≤2.

[0026] In some preferred embodiments of the present application, the silicon-carbon material is a silicon-based material containing silicon and carbon material, and / or containing SiO y and a silicon-based material of a carbon material, wherein 0≤y≤2.

[0027] In some preferred embodiments of the present application, the silicon alloy material is a Mg2Si alloy material and / or a Fe2Si alloy material.

[0028] Silicon-based materials have high specific capacity, but their lithium insertion mechanism is highly susceptible to volume expansion, leading to electrode material cracking and failure. Carbon-based materials offer greater stability than silicon-based materials. In some preferred embodiments, the silicon-based material comprises a silicon-carbon material. The silicon and carbon in this silicon-carbon material form a complementary relationship. The high specific capacity of the silicon-based material combined with the cyclic stability of the carbon-based material can effectively address the issue of material expansion failure while also ensuring good cycling performance.

[0029] Specifically, the mass percentage S of the silicon element in the negative electrode material layer can be but is not limited to 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 12wt%, 13wt%, 15wt%, 17wt%, 18wt%, 20wt% or any range consisting of the above values.

[0030] In some preferred embodiments of the present application, the mass percentage S of silicon element in the negative electrode material layer is 7 wt % to 15 wt %.

[0031] In some specific embodiments of the present application, the organic solvent further comprises at least one of cyclic carbonates, chain carbonates other than dimethyl carbonate, carboxylates, and ethers.

[0032] In some preferred embodiments of the present application, the cyclic carbonate includes at least one of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate and butylene carbonate.

[0033] In some preferred embodiments of the present application, the linear carbonate includes at least one of diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

[0034] In some preferred embodiments of the present application, the carboxylic acid ester includes at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate and ethyl trimethylacetate.

[0035] In some preferred embodiments of the present application, the ethers include at least one of ethylene glycol dimethyl ether, 1,3-dioxolane and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0036] In some specific embodiments of the present application, the additive further includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds.

[0037] In some preferred embodiments of the present application, the cyclic sulfate ester compound includes at least one of diethyl thiosulfate (DTD), 4-methyldiethyl thiosulfate, and propylene sulfate.

[0038] In some preferred embodiments of the present application, the sultone compound includes at least one of 1,3-propane sultone (PS), 1,4-butane sultone, and propenyl-1,3-sultone.

[0039] In some preferred embodiments of the present application, the cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, fluoroethylene carbonate (FEC), trifluoromethyl ethylene carbonate, bisfluoroethylene carbonate and the compound represented by the following structural formula 2:

[0040] In the structural formula 2 shown, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

[0041] In some preferred embodiments of the present application, the compound represented by structural formula 2 includes at least one of the following compounds 2-1 to 2-6:

[0042] In some preferred embodiments of the present application, the phosphate compound includes at least one of tris(trimethylsilyl)phosphate (TMSP), tris(triethylsilyl)phosphate and the compound represented by the following structural formula 3:

[0043] In the structural formula 3, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated hydrocarbon group, unsaturated hydrocarbon group, halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 、R 32 、R 33At least one of the groups is an unsaturated hydrocarbon group; more preferably, the compound represented by structural formula 3 includes at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

[0044] In some preferred embodiments of the present application, the borate compound includes at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;

[0045] In some preferred embodiments of the present application, the nitrile compound includes at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0046] In some embodiments, based on the total mass of the non-aqueous electrolyte as 100%, the content of the additive is 0.01wt% to 10wt%. Preferably, the content is 0.1wt%-5wt%, and more preferably, the content is 0.1% to 2%. Specifically, the content of any one of the optional substances in the additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0047] In some specific embodiments of the present application, the lithium salt includes LiPF6, LiPO2F2, LiBF4, LiBOB, LiSbF6, LiAsF6, LiCF3SO3, LiDFOB, LiDFOP, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiN(SO2F)2, LiCl, LiBr, LiI, LiClO4, LiB 10 Cl 10 , LiAlCl4, lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenylborate and lithium imide.

[0048] In some specific embodiments of the present application, the positive electrode active material may include LiFe 1-x’ M' x’ PO4、LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' comprises at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, W, Zr, V or Ti, M comprises at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, W, Zr, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1, the positive electrode active material may further comprise at least one of sulfide, selenide, and halide. More preferably, the positive electrode active material may comprise LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.8 Co 0.15 Al 0.05 O2、 LiNi 0.9 Co 0.05 Mn 0.05 O2、LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2、LiNi 0.5 Co 0.2 Al 0.3 At least one of O2.

[0049] In some specific embodiments of the present application, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductor, and the positive electrode active material, the positive electrode binder and the positive electrode conductor are blended to obtain the positive electrode material layer.

[0050] The positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0051] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0052] In some specific embodiments of the present application, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer is disposed on the surface of the negative electrode current collector. The material of the negative electrode current collector may be the same as that of the positive electrode current collector, which will not be described in detail here.

[0053] In some specific embodiments of the present application, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent. The negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are blended together to form the negative electrode material layer. The negative electrode binder and the negative electrode conductive agent may be the same as the positive electrode binder and the positive electrode conductive agent, respectively, and are not further described here.

[0054] In some specific embodiments of the present application, the lithium-ion battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0055] The diaphragm can be an existing conventional diaphragm, which can be a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and three-layer PP / PE / PP diaphragms.

[0056] The cylindrical lithium-ion battery of the present application uses silicon-based materials to effectively improve the battery energy density; by adopting a cylindrical battery with a tightly wound structure, the volume expansion of the silicon-based material is suppressed to a certain extent; ethyl methyl carbonate is selected as an organic solvent to greatly improve the wettability and fluidity of the non-aqueous electrolyte; at the same time, a silane compound containing at least one carbon-carbon double bond shown in structural formula 1 is selected as an additive, which can absorb unstable free radicals in the electrolyte, reduce side reactions, and also form a film on the positive electrode to protect the battery from good high-temperature performance and suppress high-temperature gas production. When the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte of the cylindrical lithium-ion battery, the mass percentage F of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, and the mass percentage S of the silicon element in the negative electrode material layer satisfy 0.04≤(100-D)×F / S≤5, and 50≤D≤75, 0.01≤F≤0.5, and 5≤S≤20, the battery failure problem caused by the expansion of the silicon-based negative electrode can be improved, the battery life can be improved, and the battery can be ensured to have good high-temperature performance, and the effect of suppressing gas production during high-temperature storage is obvious. DETAILED DESCRIPTION

[0057] The following will be combined with the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0058] Example 1

[0059] The method for preparing a cylindrical lithium-ion battery in this embodiment includes the following steps:

[0060] 1) Preparation of positive electrode:

[0061] The positive electrode active material LiNi was mixed in a mass ratio of 97:1.5:1.5 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black Super-P, and a binder called polyvinylidene fluoride (PVDF) are then dispersed in N-methyl-2-pyrrolidone (NMP) to create a positive electrode slurry. The slurry is evenly coated on both sides of aluminum foil, dried, rolled, and vacuum-dried. Aluminum lead wires are then ultrasonically welded to create the positive electrode plate, which is between 120 and 150 μm thick.

[0062] 2) Preparation of negative electrode:

[0063] A silicon-carbon material (a mixture of silicon oxide and graphite, with a silicon content of 7% by weight), conductive carbon black Super-P, binders styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94.2:1.2:3.0:1.5 and dispersed in deionized water to create a negative electrode slurry. The slurry was then coated on both sides of a copper foil, dried, rolled, and vacuum-dried, and nickel lead wires were ultrasonically welded to form the negative electrode plate. The plate thickness ranged from 120 to 150 μm.

[0064] 3) Preparation of electrolyte:

[0065] Dimethyl carbonate (DMC), ethylene carbonate (EC), and fluoroethylene carbonate (FEC) were mixed in a certain mass ratio, and then lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1.0 mol / L. Then, tetravinylsilane was added. Based on the total weight of the non-aqueous electrolyte being 100%, the mass percentage D of dimethyl carbonate and the mass percentage F of the compound represented by structural formula 1 are shown in Table 1.

[0066] 4) Preparation of battery cells:

[0067] A three-layer separator with a thickness of 20 μm is placed between the positive plate and the negative plate, and then the sandwich structure consisting of the positive plate, negative plate and separator is wound. The wound body is then flattened and placed in a cylindrical aluminum metal shell.

[0068] 5) Injection and formation of battery cells:

[0069] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell and sealed using a sealing machine. After sealing, the surface electrolyte was cleaned with alcohol, the battery was coated with anti-rust oil, and packaged with heat shrink film and a surface pad to prevent the battery from short-circuiting.

[0070] Then, the conventional formation for the first charge was carried out according to the following steps: 0.02C constant current charging for 30 minutes, 0.05C constant current charging for 30 minutes, 0.1C constant current charging for 120 minutes, 0.2C constant current charging for 240 minutes, with the cut-off voltage set to 3.85V, and left for 1 hour. After leaving at room temperature for 24 hours (12 hours each for the forward and reverse directions), the battery was charged at 0.5C constant current to 4.2V and discharged at 0.2C constant current to 2.75V.

[0071] Examples 2-28, Comparative Examples 1-12

[0072] This embodiment and comparative example are used to illustrate the lithium-ion battery disclosed in the present application, and include most of the operating steps in the above embodiment. The differences are as follows: based on the total weight of the non-aqueous electrolyte being 100%, the content of the organic solvent dimethyl carbonate in the non-aqueous electrolyte, the type and content of the silane compound represented by Structural Formula 1, the composition of the negative electrode active material, and the silicon content in the negative electrode material layer are specifically shown in Table 1.

[0073] The lithium-ion batteries prepared in the examples and comparative examples were subjected to performance tests as follows:

[0074] Table 1

[0075] 1. High temperature storage performance

[0076] Charge the formed battery to 4.2V at room temperature using a constant current and constant voltage of 1C, then discharge it to 2.75V at a constant current of 1C, record the initial capacity, then charge it to 4.2V at a constant current and constant voltage of 1C, then store it at 85℃ for 12h, and after the battery cools to room temperature, discharge it to 2.75V at 1C, and measure the battery's retention capacity. The calculation formula is as follows:

[0077] Battery capacity retention rate (%) = retained capacity / initial capacity × 100%.

[0078] 2. High temperature cycle performance test

[0079] At 45°C, charge the formed battery to 4.2V at a constant current and constant voltage of 1C, then charge it at a constant voltage until the current drops to 0.02C, and then discharge it to 2.75V at a constant current of 1C. Repeat this cycle 1000 times, record the first discharge capacity and the last discharge capacity, and calculate the capacity retention rate at the 1000th cycle. The calculation formula is as follows:

[0080] Capacity retention rate at the 1000th cycle (%)=discharge capacity at the 1000th cycle / discharge capacity at the 1st cycle×100%.

[0081] (1) The test results of Examples 1-15 and Comparative Examples 1-12 are shown in Table 2.

[0082] Table 2

[0083] It can be seen from the test results of Examples 1-15 that the lithium-ion battery of the present application adopts silicon-based materials, which effectively improves the energy density of the battery; by adopting a cylindrical battery with a tightly wound structure, the volume expansion of the silicon-based material is suppressed to a certain extent; ethyl methyl carbonate is selected as an organic solvent to greatly improve the wettability and fluidity of the non-aqueous electrolyte; at the same time, a silane compound containing at least one carbon-carbon double bond as shown in structural formula 1 is selected as an additive, which can absorb unstable free radicals in the electrolyte, reduce side reactions, and also form a film on the positive electrode to protect the battery from having good high-temperature performance and suppress high-temperature gas production. When the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte of the cylindrical lithium-ion battery, the mass percentage F of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, and the mass percentage S of silicon in the negative electrode material layer satisfy 0.04≤(100-D)×F / S≤5, and 50≤D≤75, 0.01≤F≤0.5, 5≤S≤20, the battery failure problem caused by the expansion of the silicon-based negative electrode can be improved, the battery life can be improved, and the battery can be guaranteed to have good high-temperature performance. At the same time, from the comparison results of Example 1 with Examples 4-6, it can be seen that when the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte, the mass percentage F of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, and the mass percentage S of silicon in the negative electrode material layer further satisfy 55≤D≤67, 0.01≤F≤0.3, 7≤S≤15, the optimization effect on the high-temperature storage and high-temperature cycle performance of the battery is better.

[0084] The test results of Comparative Examples 5-12 show that when any of the following parameters (mass percentage D of dimethyl carbonate in the non-aqueous electrolyte, mass percentage F of the silane compound represented by Structural Formula 1 in the non-aqueous electrolyte, and mass percentage S of silicon in the negative electrode material layer) do not meet the specified range, or when the value of (100-D)×F / S is too large or too small, the lithium-ion battery cannot be guaranteed to have good high-temperature storage and high-temperature cycling performance. This shows that the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte, the mass percentage F of the silane compound represented by Structural Formula 1 in the non-aqueous electrolyte, and the mass percentage S of silicon in the negative electrode material layer have a strong correlation in improving the high-temperature performance of the battery.

[0085] From the test results of Example 1 and Comparative Examples 1-4, it can be seen that the use of no additives (Comparative Example 1) and the use of other additives alone (Comparative Examples 2-4) are compared with the addition of the compound represented by Structural Formula 1 (Example 1). The effect of improving the high-temperature storage and high-temperature cycle performance of the lithium-ion battery is not good, indicating that the mechanism of improving battery performance by other additives is different from that of the compound represented by Structural Formula 1. In the system of this application, the compound represented by Structural Formula 1 has a better effect on improving the high-temperature performance of the battery than other additives.

[0086] (2) The test results of Example 1 and Examples 16-20 are shown in Table 3.

[0087] Table 3

[0088] It can be seen from the test results of Example 1 and Examples 16-20 that in the battery system of the present application, when different types of silane compounds represented by structural formula 1 containing at least one carbon-carbon double bond are used as additives, when the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte, the mass percentage F of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, and the mass percentage S of silicon element in the negative electrode material layer meet the corresponding conditions, the high-temperature storage and high-temperature cycle performance of the lithium-ion battery can be improved, indicating that the battery system of the present application is universal for different compounds represented by structural formula 1.

[0089] (3) The test results of Example 1 and Examples 21-25 are shown in Table 4.

[0090] Table 4

[0091] It can be seen from the test results of Example 1 and Examples 21-25 that in the battery system of the present application, different silicon-based negative electrode materials are used. When the mass percentage D of dimethyl carbonate in the non-aqueous electrolyte, the mass percentage F of the silane compound shown in structural formula 1 in the non-aqueous electrolyte, and the mass percentage S of the silicon element in the negative electrode material layer meet the corresponding conditions, the high-temperature storage and high-temperature cycle performance of the lithium-ion battery can be improved, indicating that the battery system of the present application is universal for different silicon-based negative electrode materials.

[0092] (4) The test results of Example 1 and Examples 26-28 are shown in Table 5.

[0093] Table 5

[0094] It can be seen from the test results of Example 1 and Examples 26-28 that in the battery system provided in the present application, the additional addition of additives such as vinyl sulfate (DTD), 1,3-propane sultone (PS), and tripropargyl phosphate can further improve the high-temperature storage and high-temperature cycle performance of the lithium-ion battery, indicating that there is a complementary effect between the compound shown in Structural Formula 1 and other additives.

[0095] The present application is further described above with the help of specific embodiments, but it should be understood that the specific description here should not be construed as limiting the essence and scope of the present application. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of this application.

Claims

1. A cylindrical lithium-ion battery, characterized in that: including a positive electrode, a negative electrode and a non-aqueous electrolyte; The negative electrode comprises a negative electrode material layer comprising a negative electrode active material, wherein the negative electrode active material comprises a silicon-based material; The non-aqueous electrolyte includes a lithium salt, an organic solvent and an additive, wherein the organic solvent includes dimethyl carbonate, and the additive includes a silane compound shown in structural formula 1: wherein R1, R2, R3 and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl and substituted or unsubstituted C2-C5 alkynyl, and at least one of R1-R4 is selected from substituted or unsubstituted C2-C5 alkenyl; The cylindrical lithium-ion battery meets the following conditions: 0.04≤(100-D)×F / S≤5, and 50≤D≤75, 0.01≤F≤0.5, 5≤S≤20; Wherein, D is the mass percentage of dimethyl carbonate in the non-aqueous electrolyte, in wt%; F is the mass percentage of the silane compound represented by structural formula 1 in the non-aqueous electrolyte, in wt%; S is the mass percentage of silicon element in the negative electrode material layer, in wt%.

2. The cylindrical lithium-ion battery according to claim 1, characterized in that: The lithium ion battery meets the following condition: 0.1≤(100-D)×F / S≤3.

3. The cylindrical lithium-ion battery according to claim 1, characterized in that: The mass percentage D of the dimethyl carbonate in the non-aqueous electrolyte is 55wt% to 67wt%.

4. The cylindrical lithium-ion battery according to claim 1, characterized in that: The mass percentage F of the silane compound represented by the structural formula 1 in the non-aqueous electrolyte is 0.01 wt % to 0.3 wt %.

5. The cylindrical lithium-ion battery according to claim 1, characterized in that: The mass percentage S of silicon element in the negative electrode material layer is 7wt% to 15wt%.

6. The cylindrical lithium-ion battery according to claim 1, characterized in that: The silane compound shown in the structural formula 1 includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, trivinylethylsilane, vinyltriethylsilane, trivinylethynylsilane, tetrapropylenesilane, trivinylpropylsilane, tripropylenepropylsilane, dipropylenedipropylsilane and divinyldipropylsilane.

7. The cylindrical lithium-ion battery according to claim 1, characterized in that: The silicon-based material includes at least one of a silicon material, a silicon oxide material, a silicon-carbon material and a silicon alloy material.

8. The cylindrical lithium-ion battery according to claim 7, characterized in that: The silicon material is a nano silicon material; and / or, The silicon oxide material is SiO x Materials, wherein 0≤x≤2; and / or The silicon-carbon material is a silicon-based material containing silicon and carbon material and / or containing SiO y and a silicon-based material of a carbon material, wherein 0≤y≤2; and / or, The silicon alloy material is a Mg2Si alloy material and / or a Fe2Si alloy material.

9. The cylindrical lithium-ion battery according to claim 1, characterized in that: The organic solvent further comprises at least one of cyclic carbonates, chain carbonates other than dimethyl carbonate, carboxylates and ethers.

10. The cylindrical lithium-ion battery according to claim 9, characterized in that: The cyclic carbonate comprises at least one of ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate and butylene carbonate; and / or, The linear carbonate comprises at least one of diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate; and / or, The carboxylic acid ester comprises at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate and ethyl trimethylacetate; and / or, The ethers include at least one of ethylene glycol dimethyl ether, 1,3-dioxolane and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

11. The cylindrical lithium-ion battery according to claim 1, characterized in that: The additive further includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds.

12. The cylindrical lithium-ion battery according to claim 11, characterized in that: Based on the total mass of the non-aqueous electrolyte being 100%, the content of the additive is 0.01 wt % to 10 wt %.

13. The cylindrical lithium ion battery according to claim 11, characterized in that: The cyclic sulfate ester compound includes at least one of vinyl sulfate, 4-methylvinyl sulfate, and propylene sulfate; and / or, The sultone compound includes at least one of 1,3-propane sultone, 1,4-butane sultone and propenyl-1,3-sultone; and / or, The cyclic carbonate compound includes at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate and the compound shown in the following structural formula 2: In the structural formula 2 shown, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, a C1-C5 group; and / or, The phosphate compound includes at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate and the compound shown in the following structural formula 3: In the structural formula 3, R 31 , R 32 , R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 , R 32 , R 33 At least one of them is an unsaturated hydrocarbon group; and / or, The borate compounds include tris(trimethylsilyl)borate and tris(triethylsilyl)borate. at least one of; and / or, The nitrile compound includes at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebaconitrile.

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