Lithium ion battery and electric device

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery and an electric device. The lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the positive electrode comprises a positive electrode active material; the positive active material comprises lithium iron phosphate; the negative electrode comprises a negative electrode active material; the negative active material comprises graphite and a silicon-carbon composite material; the electrolyte comprises a lithium salt, a solvent and an additive, the additive comprises fluoroethylene carbonate and an acesulfamide compound. Compared with the prior art, the lithium ion battery provided by the invention not only can solve the problem of insufficient energy density of the current lithium iron phosphate battery, but also can optimize the system expansion problem after silicon is doped in the negative electrode of the lithium iron battery core, obviously reduces the expansion of the negative electrode plate by more than 20%, prolongs the cycle life, improves the storage performance and reduces the gas production in the cycle process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and more particularly to a lithium ion battery and an electrical device. Background Art

[0002] Lithium-ion batteries are the core devices for new energy storage, and the choice of their cathode materials directly determines the performance limit of the battery. Lithium iron phosphate (LiFePO4, LFP) has become the mainstream choice for power batteries and energy storage batteries due to its high safety, long cycle life (>2000 times @ 80% capacity retention) and low cost. However, the theoretical specific capacity of LFP material is only 170mAh / g, and the operating voltage platform (3.2V vs. Li + / Li) limits the improvement of energy density. The industry generally adopts the method of increasing compaction density (>2.5g / cm 3 ) and electrode thinning (<120μm) and other process optimization measures, but the energy density of single cells is still difficult to exceed 180Wh / kg, which seriously restricts its application in the field of high-end passenger cars.

[0003] To increase energy density, the industry has attempted to incorporate high-capacity silicon materials (theoretical specific capacity of 3579 mAh / g, 10 times that of graphite) into the anode. A typical approach involves doping a graphite anode with 5-15% silicon-carbon composite material. This design can increase the anode specific capacity to 450-600 mAh / g, theoretically pushing the energy density of LFP batteries above 200 Wh / kg. However, silicon materials have a fatal flaw: the volume expansion effect: silicon expands by 280% when fully lithiated, leading to delamination of the active material from the current collector (sheet resistance increases by >300% after 100 cycles). Particle fragmentation triggers continuous SEI film growth, exacerbating interfacial side reactions. While existing technologies can improve electrolyte additives, such as adding more fluoroethylene carbonate (FEC), to form a LiF-rich layer on the silicon surface, enhancing the flexibility and reducing expansion, high FEC levels can produce significant gassing during high-temperature cycling. Excessive FEC additions can actually be detrimental to battery performance, resulting in a cycle life of silicon-doped anode cells plummeting to just 4-500 cycles. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a lithium-ion battery and an electrical device. The lithium-ion battery provided by the present invention can not only solve the problem of insufficient energy density of current lithium iron phosphate batteries, but also optimize the system expansion problem after the negative electrode of the iron-lithium battery cell is doped with silicon, significantly reducing the expansion of the negative electrode sheet by more than 20%, thereby increasing the cycle life, improving storage performance, and reducing gas production during the cycle.

[0005] The present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte:

[0006] The positive electrode includes a positive electrode active material; the positive electrode active material includes lithium iron phosphate;

[0007] The negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and silicon-carbon composite material;

[0008] The electrolyte comprises: a lithium salt, a solvent and an additive; the additive comprises fluoroethylene carbonate and sulfacetamide;

[0009] And the following conditions are met:

[0010] W1×W2≥β×(S1 / 5%) γ ;

[0011] Among them, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetylsulfonamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.5.

[0012] Preferably, the W1% is 5% to 10%; and / or the W2% is 0.2% to 1%; and / or the S1 is 1% to 7.5%.

[0013] Preferably, the D50 particle size of the lithium iron phosphate is 2 to 5 μm;

[0014] And / or, the surface of the lithium iron phosphate is coated with a nitrogen-doped carbon layer;

[0015] and / or, the thickness of the nitrogen-doped carbon layer is 2 to 8 nm;

[0016] and / or, the nitrogen doping concentration of the nitrogen-doped carbon layer is 3 to 8 at %;

[0017] And / or, the coating completeness of the nitrogen-doped carbon layer is ≥95%.

[0018] Preferably, the positive electrode further comprises a conductive agent and a binder;

[0019] And / or, in the positive electrode, the mass ratio of lithium iron phosphate, conductive agent and binder is (90-99): (0.5-5): (0.5-5).

[0020] Preferably, the silicon-carbon composite material includes a carbon-coated silicon composite material; the carbon-coated silicon composite material includes porous silicon microspheres and a carbon coating layer coated on the surface of the porous silicon microspheres; and / or the thickness ratio of the porous silicon microspheres to the carbon coating layer is (900~1100):1.

[0021] Preferably, the negative electrode further comprises a conductive agent, a thickener and a binder;

[0022] And / or, in the negative electrode, the mass ratio of graphite, silicon-carbon composite material, conductive agent, thickener and binder is (84.5-97.4): (1-10): (0.5-2): (0.1-0.5): (1-3).

[0023] Preferably, the lithium salt includes lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide;

[0024] And / or, the mass percentage of the lithium salt in the electrolyte is 4% to 26%.

[0025] Preferably, the solvent is a superconducting fast-charging solvent; and / or the superconducting fast-charging solvent has a kinematic viscosity of ≤5 mPa·s at room temperature; and / or the superconducting fast-charging solvent has a room temperature conductivity of ≥10 mS / cm;

[0026] And / or, the mass percentage of the solvent in the electrolyte is 60% to 90%.

[0027] Preferably, the additives further include other additives; the other additives include one or more of vinylene carbonate, vinyl ethylene carbonate, difluoroethylene carbonate, bisethylene carbonate, vinyl sulfate, propylene sulfate, 1,3-propanesulfonate, 1,4-butanesulfonate, vinyl bissulfate, dimethyl methanesulfonate, vinyl bissulfate, lithium difluorophosphate, lithium nitrate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorooxalatophosphate, lithium tetrafluorooxalatophosphate, lithium tetrafluoroborate, lithium difluorosulfonylimide, lithium fluorosulfonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, and tetravinylsilane;

[0028] And / or, the mass percentage of the other additives in the electrolyte is 0.8% to 3%.

[0029] The present invention also provides an electrical device comprising the lithium-ion battery described in the above technical solution.

[0030] The present invention provides a lithium ion battery and an electrical device; the lithium ion battery includes a positive electrode, a negative electrode, a separator and an electrolyte; the positive electrode includes a positive electrode active material; the positive electrode active material includes lithium iron phosphate; the negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and a silicon-carbon composite material; the electrolyte includes: a lithium salt, a solvent and an additive; the additive includes fluoroethylene carbonate and an acetamide compound; and the following conditions are met: W1×W2≥β×(S1 / 5%) γ; Wherein, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.5. Compared with the prior art, the lithium-ion battery provided by the present invention uses lithium iron phosphate as the positive electrode material, selects an electrolyte including specific component additives, and cooperates with the negative electrode including silicon-carbon composite material to achieve better overall interaction, which can not only solve the problem of insufficient energy density of current lithium iron phosphate batteries, but also optimize the system expansion problem after the negative electrode of the lithium iron phosphate battery cell is doped with silicon, significantly reducing the expansion of the negative electrode plate by more than 20%, increasing the cycle life, improving storage performance, and reducing gas production during the cycle. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the present application, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0032] In the description of this application, "same chemical composition" should be understood in a broad sense, that is, the main components of the two have the same chemical composition, or the chemical composition of the two is basically the same, and may have errors within the allowable range in the field that are understandable to those skilled in the art or contain impurities within the allowable range.

[0033] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0034] Unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. All patents and publications referred to in this application are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning that they include the contents specified in this application but do not exclude contents elsewhere.

[0035] At present, the energy density of lithium iron phosphate batteries in existing technology is insufficient. Although the energy density of the battery can be improved by introducing high-capacity silicon materials, the problem of silicon volume expansion effect limits the further application of lithium iron phosphate-silicon carbon batteries; although by improving the electrolyte additives, such as adding more fluoroethylene carbonate (FEC), a LiF-rich layer can be formed on the silicon surface to enhance the flexibility of the silicon negative electrode and improve expansion; however, under high-temperature cycles, high FEC produces a large amount of gas, and adding too much is harmful to battery performance, resulting in the cycle life of the negative electrode silicon-doped battery cell plummeting to only 4 to 500 weeks. On this basis, the present invention provides a lithium-ion battery, specifically a high-energy-density lithium iron phosphate-silicon-carbon battery (a lithium-ion battery with a lithium iron phosphate positive electrode and a graphite-doped silicon negative electrode). By controlling the components and dosage of electrolyte additives and coordinating the addition amount of silicon-carbon composite materials in the silicon-carbon negative electrode, on the basis of meeting certain conditions, it can not only solve the current problem of insufficient energy density of lithium iron phosphate batteries, but also optimize the system expansion problem after the negative electrode of the iron-lithium battery cell is doped with silicon, significantly reducing the expansion of the negative electrode sheet by more than 20%, thereby increasing the cycle life, improving the storage performance, reducing the gas production during the cycle, and ultimately improving the battery performance.

[0036] The present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte:

[0037] The positive electrode includes a positive electrode active material; the positive electrode active material includes lithium iron phosphate;

[0038] The negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and silicon-carbon composite material;

[0039] The electrolyte comprises: a lithium salt, a solvent and an additive; the additive comprises fluoroethylene carbonate and sulfacetamide;

[0040] And the following conditions are met:

[0041] W1×W2≥β×(S1 / 5%) γ ;

[0042] Among them, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetylsulfonamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.5.

[0043] In the present invention, the lithium-ion battery includes a positive electrode, a negative electrode, a separator and an electrolyte; the positive electrode includes a positive electrode active material; and the positive electrode active material includes lithium iron phosphate (LiFePO4).

[0044] In the present invention, the D50 particle size of the lithium iron phosphate is preferably 2 to 5 μm; specifically, it can be: 2 μm, 3 μm, 4 μm, 5 μm, and more preferably 3 to 4 μm.

[0045] In the present invention, the surface of the lithium iron phosphate is preferably coated with a nitrogen-doped carbon layer; the thickness of the nitrogen-doped carbon layer is preferably 2 to 8 nm; specifically, it can be: 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, and more preferably 4 to 6 nm.

[0046] In the present invention, the nitrogen doping concentration of the nitrogen-doped carbon layer is preferably 3-8 at %, specifically 3 at %, 4 at %, 5 at %, 6 at %, 7 at %, 8 at %, and more preferably 5-6 at %.

[0047] In the present invention, the coating completeness of the nitrogen-doped carbon layer is preferably ≥95%.

[0048] The present invention uses the positive electrode active material including the above-mentioned lithium iron phosphate, which can ensure that the positive electrode obtained further has good electrochemical performance.

[0049] In the present invention, the positive electrode preferably includes, in addition to lithium iron phosphate, a conductive agent and a binder. The present invention does not particularly limit the type and source of the conductive agent and binder, and conventional commercially available conductive agents and binders for preparing positive electrodes, which are well known to those skilled in the art, can be used. In a preferred embodiment of the present invention, the conductive agent in the positive electrode is conductive carbon black (Super P), and the binder is polyvinylidene fluoride (PVDF).

[0050] In the present invention, in the positive electrode, the mass ratio of lithium iron phosphate, conductive agent and binder is preferably (90-99): (0.5-5): (0.5-5), more preferably (95.5-96): (2-2.5):2.

[0051] The present invention has no special restrictions on the preparation method of the positive electrode, and the preparation method of the lithium iron phosphate positive electrode sheet well known to those skilled in the art can be adopted; in a preferred embodiment of the present invention, the preparation method of the positive electrode includes the following steps: dissolving the positive electrode active material lithium iron phosphate, the conductive agent, and the adhesive in a solvent (such as N-methylpyrrolidone) and mixing them evenly to form a positive electrode slurry, and then evenly coating the positive electrode slurry on the positive electrode collector (such as aluminum foil), drying, and then cold pressing, trimming, cutting, striping, vacuum drying, and finally welding the pole ears to make a positive electrode of a lithium ion battery that meets the requirements.

[0052] In the present invention, the negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and a silicon-carbon composite material; the present invention has no special restrictions on the type and source of the graphite, and commercially available natural graphite and / or artificial graphite well known to those skilled in the art can be used.

[0053] In the present invention, the silicon-carbon composite material preferably includes a carbon-coated silicon composite material.

[0054] In the present invention, the carbon-coated silicon composite material preferably comprises porous silicon microspheres and a carbon coating layer coated on the surface of the porous silicon microspheres; the thickness ratio of the porous silicon microspheres to the carbon coating layer is preferably (900-1100):1.

[0055] The present invention has no special limitation on the source of the silicon-carbon composite material, and any commercially available product or homemade product known to those skilled in the art can be used.

[0056] In the present invention, in addition to graphite and silicon-carbon composite materials, the negative electrode preferably also includes a conductive agent, a thickener and a binder; the present invention has no special restrictions on the types and sources of the conductive agent, thickener and binder, and conventional commercially available types of conductive agents, thickeners and binders for preparing negative electrodes that are well known to those skilled in the art can be used.

[0057] In a preferred embodiment of the present invention, the conductive agent in the negative electrode includes conductive carbon black (Super P) and / or carbon nanotubes (CNTs), preferably conductive carbon black (Super P) and carbon nanotubes (CNTs), the two forming a composite conductive network, which is beneficial to improving the performance of the negative electrode; the thickener includes carboxymethyl cellulose (CMC), and the binder includes one or more of lithium polyacrylate (PAA-Li), sodium carboxymethyl cellulose (CMC-Na) and styrene-butadiene rubber (SBR), preferably a PAA+SBR composite system, wherein the mass ratio of PAA to SBR is (3 to 10):1.

[0058] In the present invention, in the negative electrode, the mass ratio of graphite, silicon-carbon composite material, conductive agent, thickener and binder is preferably (84.5-97.4): (1-10): (0.5-2): (0.1-0.5): (1-3).

[0059] The present invention has no special restrictions on the preparation method of the negative electrode, and the preparation method of graphite-doped silicon negative electrode sheets well known to those skilled in the art can be adopted; in a preferred embodiment of the present invention, the preparation method of the negative electrode comprises the following steps: dissolving the negative electrode active material graphite, silicon-carbon composite material, conductive agent, thickener, and adhesive in a solvent (such as deionized water) and mixing them evenly to form a negative electrode slurry, and then evenly coating the negative electrode slurry on the negative electrode collector (such as copper foil), drying, and then cold pressing, trimming, cutting, and striping are carried out in sequence, and then vacuum drying is carried out, and finally the pole ears are welded to form a negative electrode of a lithium ion battery that meets the requirements.

[0060] In the present invention, the electrolyte includes: a lithium salt, a solvent and an additive; wherein the lithium salt can dissociate into lithium ions in the electrolyte, preferably including lithium hexafluorophosphate (LiPF6) and / or lithium bis(fluorosulfonyl)imide (LiFSI), more preferably lithium hexafluorophosphate; the present invention has no special restrictions on the source of the lithium salt, and commercially available products familiar to those skilled in the art can be used.

[0061] In the present invention, the mass percentage of the lithium salt in the electrolyte is preferably 4% to 26%, more preferably 12% to 13%.

[0062] In the present invention, the solvent is preferably a superconducting fast-charging solvent; the kinematic viscosity of the superconducting fast-charging solvent at room temperature is preferably ≤5mPa·s, and the room temperature conductivity is preferably ≥10mS / cm. In a preferred embodiment of the present invention, the solvent is specifically composed of cyclic carbonate: chain carbonate: ultra-low viscosity solvent, wherein the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate, wherein typical combinations but non-limiting examples include: a combination of ethylene carbonate and propylene carbonate, and a combination of propylene carbonate and butylene carbonate; the chain carbonate includes one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate, wherein typical combinations but non-limiting examples include: dimethyl carbonate and diethyl carbonate, a combination of ethyl methyl carbonate and methyl propyl carbonate, a combination of ethyl propyl carbonate and methyl formate; the ultra-low viscosity solvent can be a carbonate, a carboxylate, a nitrile or an ether, and their halogenated derivatives, preferably one or more of dimethyl carbonate, ethyl acetate, ethyl propionate, methyl acetate, methyl formate, methyl propionate, acetonitrile, propionitrile, butyronitrile, and ethylene glycol dimethyl ether; the mass ratio of the cyclic carbonate, the chain carbonate, and the ultra-low viscosity solvent is preferably (15-35): (5-40): (5-80), more preferably 30:30:40.

[0063] The present invention has no particular limitation on the source of the solvent, and commercially available products known to those skilled in the art may be used.

[0064] In the present invention, the mass percentage of the solvent in the electrolyte is preferably 60% to 90%, more preferably 73% to 82%.

[0065] In the present invention, the additive includes fluoroethylene carbonate (FEC) and an acetamide compound; the acetamide compound preferably includes acetamide salt and / or a derivative of acetamide salt, more preferably one or more of acetamide potassium, acetamide lithium, and acetamide sodium, and even more preferably acetamide potassium (AK). The present invention does not particularly limit the sources of the fluoroethylene carbonate (FEC) and acetamide compound; commercially available products known to those skilled in the art may be used.

[0066] In the present invention, in addition to fluoroethylene carbonate (FEC) and acetylsulfonamide compounds, the additives preferably also include other additives for high temperature protection; the other additives preferably include vinylene carbonate, vinyl ethylene carbonate, difluoroethylene carbonate, bisethylene carbonate, vinyl sulfate, propylene sulfate, 1,3-propanesulfone, 1,4-butanesulfone, vinyl bissulfate, dimethyl methanesulfonate, vinyl bissulfate, lithium difluorophosphate, lithium nitrate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorooxalatophosphate, lithium tetrafluorooxalatophosphate, lithium tetrafluoroborate, lithium difluorosulfonylimide, lithium fluorosulfonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tetravinylsilane, more preferably vinylene carbonate and lithium difluorophosphate; the present invention has no special restrictions on the source of the other additives, and commercially available products well known to those skilled in the art can be used.

[0067] In the present invention, the mass percentage of the other additives in the electrolyte is preferably 0.8% to 3%, more preferably 2%.

[0068] The present invention has no particular limitation on the type and source of the separator, and commercially available products known to those skilled in the art, such as PE film, can be used.

[0069] The present invention adopts the above-mentioned positive electrode, negative electrode, separator and electrolyte, and can obtain a lithium-ion battery according to a preparation method well known to those skilled in the art (such as a conventional lamination process), and the present invention has no special limitation on this.

[0070] The present invention improves battery performance by using an electrolyte solution containing a sulfonamide compound and fluoroethylene carbonate in a lithium iron phosphate positive electrode-silicon-doped carbon negative electrode system. In the present invention, the lithium-ion battery needs to meet the following conditions:

[0071] W1×W2≥β×(S1 / 5%) γ ;

[0072] Among them, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetylsulfonamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.5.

[0073] In the present invention, the W1% is preferably 5% to 10%, specifically 5%, 6%, 7%, 8%, 9%, and 10%; the W2% is preferably 0.2% to 1%, specifically 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%; the S1 is preferably 1% to 7.5%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 7.5%.

[0074] In the present invention, in a lithium-ion battery system with a graphite-doped silicon negative electrode (S1), fluoroethylene carbonate (FEC, W1%) and sulfacetamide compound (W2%) and other additives are simultaneously added to the electrolyte. At the same time, the synergistic effect of FEC and sulfacetamide compound is used to improve the expansion behavior, cycle life and high-temperature storage performance of the silicon-carbon negative electrode, and significantly reduce the gas production. Its mechanism of action is as follows: FEC preferentially decomposes on the silicon surface through reduction to form an inorganic-organic composite SEI film rich in LiF. The high mechanical strength of LiF can resist the stress generated by the volume expansion of silicon (300%) and prevent the active material from pulverizing due to the rupture of the SEI film. At the same time, the sulfonamide group (-SO2-NH-) contained in the acetylsulfonamide compound forms a stable coordination bond with the silicon surface through chemical adsorption, thereby enhancing the interfacial bonding between the silicon particles and the graphite matrix and inhibiting the structural stratification during the expansion process. Together, the two control the thickness expansion rate of the negative electrode graphite-doped silicon full battery to ≤8% (conventional system>15%). In addition, the fluorine-containing components (such as LiF) in the FEC decomposition products have high thermal stability (decomposition temperature>300℃), while the sulfonamide groups in the acetylsulfonamide compound can scavenge free radicals in the electrolyte (such as PF5 - ), inhibiting the hydrolysis reaction of LiPF6 at high temperature, and the two synergistically reduce gas production. FEC inhibits the oxidative decomposition of EC solvents, and acetylsulfonamide compounds capture dissolved transition metal ions (such as Fe) through sulfonic acid groups. 2+ ), blocking the catalytic gas production chain reaction, and combined with FEC to make the gas production less than 0.5mL / Ah after storage at high temperature (60℃) for 7 days (traditional system>2mL / Ah).

[0075] The present invention also provides an electrical device comprising the lithium-ion battery described in the above technical solution. Specifically, the lithium-ion battery can serve as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships, satellites, and energy storage systems.

[0076] The present invention provides a lithium ion battery and an electrical device; the lithium ion battery includes a positive electrode, a negative electrode, a separator and an electrolyte; the positive electrode includes a positive electrode active material; the positive electrode active material includes lithium iron phosphate; the negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and a silicon-carbon composite material; the electrolyte includes: a lithium salt, a solvent and an additive; the additive includes fluoroethylene carbonate and an acetamide compound; and the following conditions are met: W1×W2≥β×(S1 / 5%) γ ; Wherein, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.5. Compared with the prior art, the lithium-ion battery provided by the present invention uses lithium iron phosphate as the positive electrode material, selects an electrolyte including specific component additives, and cooperates with the negative electrode including silicon-carbon composite material to achieve better overall interaction, which can not only solve the problem of insufficient energy density of current lithium iron phosphate batteries, but also optimize the system expansion problem after the negative electrode of the lithium iron phosphate battery cell is doped with silicon, significantly reducing the expansion of the negative electrode plate by more than 20%, increasing the cycle life, improving storage performance, and reducing gas production during the cycle.

[0077] To further illustrate the present invention, the following examples are provided for detailed description. The raw materials used in the following examples of the present invention are all commercially available; wherein, the D50 particle size of lithium iron phosphate is 3-4 μm, the surface of the lithium iron phosphate particles is coated with a nitrogen-doped carbon layer with a thickness of 4-6 nm, a nitrogen doping concentration of 5-6 at%, and a carbon layer coating completeness of ≥95%; the silicon-carbon composite material adopts a gradient CVD method to deposit silicon in porous carbon, and then introduce a carbon source gas (methane) to vapor-deposit the carbon coating layer on the surface of the porous silicon microspheres. The surface deposition process is divided into three stages (300°C / 0.5 kPa→450°C / 5 kPa→ 380℃ / 3kPa), forming a gradient porous structure of 60-70nm, and obtaining a carbon-coated silicon composite material; the carbon nanotubes are single-arm carbon nanotubes (SWCNTs), meeting the following conditions: tube diameter 1-2nm, length 5-20μm, aspect ratio ≥5000, and surface carboxylation treatment (-COOH content 0.5-3at%), the carboxylation treatment improves dispersibility and forms hydrogen bonds with acesulfame in the electrolyte. In the embodiment of the present invention, the addition of the following amount of carbon nanotubes also helps to balance conductivity and slurry viscosity.

[0078] Example 1

[0079] This embodiment provides a non-aqueous electrolyte, which includes lithium hexafluorophosphate, an additive, and a solvent. The additive includes potassium acesulfame, fluoroethylene carbonate, vinylene carbonate, and lithium difluorophosphate.

[0080] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of potassium acesulfame is 0.5%, the mass percentage of fluoroethylene carbonate is 5%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 80%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0081] This embodiment also provides a method for preparing the non-aqueous electrolyte, which comprises the following steps:

[0082] When the oxygen content is less than 0.1 ppm and the water content is less than 0.1 ppm, the above components are mixed according to the formula amount and stirred evenly to obtain the non-aqueous electrolyte.

[0083] Example 2

[0084] This embodiment provides a non-aqueous electrolyte, which includes lithium hexafluorophosphate, an additive, and a solvent. The additive includes potassium acesulfame, fluoroethylene carbonate, vinylene carbonate, and lithium difluorophosphate.

[0085] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of potassium acesulfame is 0.2%, the mass percentage of fluoroethylene carbonate is 5%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 80.3%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0086] The preparation method of the non-aqueous electrolyte in this embodiment is the same as that in Example 1.

[0087] Example 3

[0088] This embodiment provides a non-aqueous electrolyte, which includes lithium hexafluorophosphate, an additive, and a solvent. The additive includes potassium acesulfame, fluoroethylene carbonate, vinylene carbonate, and lithium difluorophosphate.

[0089] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of acesulfame potassium is 1%, the mass percentage of fluoroethylene carbonate is 5%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 79.5%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0090] The preparation method of the non-aqueous electrolyte in this embodiment is the same as that in Example 1.

[0091] Example 4

[0092] This embodiment provides a non-aqueous electrolyte, which includes lithium hexafluorophosphate, an additive, and a solvent. The additive includes potassium acesulfame, fluoroethylene carbonate, vinylene carbonate, and lithium difluorophosphate.

[0093] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of potassium acesulfame is 0.5%, the mass percentage of fluoroethylene carbonate is 10%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 75%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0094] The preparation method of the non-aqueous electrolyte in this embodiment is the same as that in Example 1.

[0095] Example 5

[0096] The difference between this embodiment and embodiment 1 is that the composition of the solvent includes ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7, and the rest is the same as embodiment 1.

[0097] Example 6

[0098] The difference between this embodiment and embodiment 1 is that acesulfame potassium is replaced by acesulfame lithium of the same content, and the rest is the same as embodiment 1.

[0099] Example 7

[0100] The difference between this embodiment and embodiment 1 is that acesulfame potassium is replaced by acesulfame sodium in an equal amount, and the rest is the same as embodiment 1.

[0101] Example 8

[0102] This embodiment provides a non-aqueous electrolyte, which includes lithium hexafluorophosphate, an additive, and a solvent. The additive includes potassium acesulfame, fluoroethylene carbonate, vinylene carbonate, and lithium difluorophosphate.

[0103] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of acesulfame potassium is 0.8%, the mass percentage of fluoroethylene carbonate is 8%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 76.7%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0104] The preparation method of the non-aqueous electrolyte in this embodiment is the same as that in Example 1.

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 1 is that acesulfame potassium is not added, and the content of the solvent is adjusted so that the mass percentage of the total system is 100%. Other aspects are the same as Example 1.

[0107] Comparative Example 2

[0108] The difference between this comparative example and Example 1 is that acesulfame potassium is replaced by an equal amount of vinyl sulfate, and the other contents are the same as those in Example 1.

[0109] Comparative Example 3

[0110] The difference between this embodiment and embodiment 1 is that the fluoroethylene carbonate is replaced by an equal amount of acesulfame potassium, and the other contents are the same as those in embodiment 1.

[0111] Application Examples 1 to 8 and Application Comparative Examples 1 to 3

[0112] The electrolytes provided in Examples 1 to 8 and Comparative Examples 1 to 3 are assembled into lithium-ion batteries, comprising the following steps:

[0113] (1) Preparation of positive electrode sheets for lithium-ion batteries:

[0114] The positive electrode active material lithium iron phosphate (LFP), conductive agent Super-P, and binder PVDF were dissolved in solvent N-methylpyrrolidone at a mass ratio of 95.8:2.2:2.0 and mixed evenly to prepare the positive electrode slurry. The positive electrode slurry was evenly coated on the current collector aluminum foil with a coating amount of 18 mg / cm 2 Then, after drying at 90°C, cold pressing, trimming, cutting, and striping are carried out, and then drying is carried out at 90°C under vacuum conditions for 4 hours, and the tabs are welded to produce a positive electrode sheet for a lithium-ion secondary battery that meets the requirements.

[0115] (2) Preparation of negative electrode sheets for lithium-ion batteries:

[0116] The negative electrode active material artificial graphite, silicon-carbon composite material, conductive agent Super-P, carbon nanotube CNT, thickener CMC, and adhesive PAA+SBR were dissolved in solvent deionized water at a mass ratio of 92.5:4.0:1.0:0.04:0.2:1.76:0.5 and mixed evenly to prepare the negative electrode slurry. The negative electrode slurry was evenly coated on the current collector copper foil with a coating amount of 9.1 mg / cm 2 Then, after drying at 90°C, cold pressing, trimming, cutting, and striping are carried out, and then drying under vacuum conditions at 110°C for 4 hours, and the tabs are welded to produce the negative electrode sheet of the lithium-ion secondary battery that meets the requirements.

[0117] (3) Preparation of lithium-ion batteries:

[0118] The positive electrode sheet, negative electrode sheet and separator (PE film) of the lithium ion secondary battery prepared according to the above process were laminated to form a battery with a thickness of 8 mm, a width of 60 mm and a length of 130 mm, and vacuum baked at 90°C for 10 h, injected with the electrolyte in Examples 1 to 8 and Comparative Examples 1 to 3, and allowed to stand for 24 h. Thereafter, the battery was charged to 4.4 V at a constant current of 0.1 C (200 mA), then charged at a constant voltage of 4.4 V until the current dropped to 0.05 C (100 mA), and then discharged to 2.5 V at a constant current of 0.1 C (200 mA). The charge and discharge were repeated twice, and finally charged to 3.8 V at a constant current of 0.1 C (200 mA). The preparation of the lithium ion secondary battery was completed.

[0119] Application Example 9

[0120] The electrolyte provided in Example 1 is assembled into a lithium-ion battery using the preparation method in the above-mentioned Application Example 1, except that: in step (2), the mass ratio of artificial graphite, silicon-carbon composite material, conductive agent Super-P, carbon nanotubes CNT, thickener CMC, and adhesive PAA+SBR is 95.53:0.97:1.0:0.04:0.2:1.76:0.5.

[0121] Application Example 10

[0122] The electrolyte provided in Example 1 is assembled into a lithium-ion battery using the preparation method in the above-mentioned Application Example 1, except that: in step (2), the mass ratio of artificial graphite, silicon-carbon composite material, conductive agent Super-P, carbon nanotubes CNT, thickener CMC, and adhesive PAA+SBR is 89.26:7.24:1.0:0.04:0.2:1.76:0.5.

[0123] Application Example 11

[0124] (1) A non-aqueous electrolyte is provided, comprising lithium hexafluorophosphate, an additive and a solvent, wherein the additive comprises potassium acesulfame, fluoroethylene carbonate, vinylene carbonate and lithium difluorophosphate.

[0125] Based on the total mass of the non-aqueous electrolyte being 100%, the mass percentage of lithium hexafluorophosphate is 12.5%; the mass percentage of potassium acesulfame is 0.4%, the mass percentage of fluoroethylene carbonate is 6%, the mass percentage of vinylene carbonate is 1%, and the mass percentage of lithium difluorophosphate is 1%; the mass percentage of the solvent is 79.1%, and the specific composition includes ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 30:30:40.

[0126] The preparation method of the above non-aqueous electrolyte is the same as that of Example 1.

[0127] (2) The electrolyte provided in step (1) is assembled into a lithium-ion battery using the preparation method in the above-mentioned application example 1, except that: in step (2), the mass ratio of artificial graphite, silicon-carbon composite material, conductive agent Super-P, carbon nanotubes CNT, thickener CMC, and adhesive PAA+SBR is 90.71:5.79:1.0:0.04:0.2:1.76:0.5.

[0128] After calculation, the application of Examples 1 to 11 can meet the following conditions:

[0129] W1×W2≥β×(S1 / 5%) γ , where β=0.2~0.5 and γ=1.2~1.5.

[0130] The results are shown in Table 1 below.

[0131] Table 1 Parameter calculation results of application examples 1 to 11 and application comparative examples 1 to 3

[0132]

[0133]

[0134] Note: β takes the maximum value of 0.5, γ: when S1 / 5% is greater than or equal to 1, take 1.5, when less than 1, take 1.2, so as to ensure that the value of W1×W2 can be greater than or equal to β×(S1 / 5%) γ The upper limit value of .

[0135] The lithium-ion batteries prepared in the above-mentioned application examples 1 to 11 and application comparative examples 1 to 3 were tested for high-temperature storage performance, cycle performance, and high-temperature storage gas generation performance. The test methods are as follows:

[0136] (1) High temperature storage performance test of lithium-ion secondary batteries:

[0137] At 25°C, the lithium ion secondary batteries prepared in application examples 1 to application examples 11 and application comparative examples 1 to application comparative examples 3 were first charged to 3.65V at a constant current of 0.05C, and then further charged at a constant voltage of 3.65V to a current of 0.05C, and then discharged to 2.5V at a constant current of 0.5C. The discharge capacity of this time is the discharge capacity of the lithium ion secondary battery before high temperature storage; then the lithium ion secondary battery was charged to 3.65V at a constant current of 0.5C, and the lithium ion secondary battery was discharged to 2.5V. The lithium-ion secondary battery is stored at 60°C for 90 days. After the storage period, the lithium-ion secondary battery is placed in a 25°C environment and then discharged to 2.5V at a constant current of 0.5C. The lithium-ion secondary battery is then charged to 3.65V at a constant current of 0.5C. The battery is further charged at a constant voltage of 3.65V until the current reaches 0.05C. The lithium-ion secondary battery is then discharged to 2.5V at a constant current of 0.5C. The last discharge capacity is the discharge capacity of the lithium-ion secondary battery after high-temperature storage. The capacity retention rate (%) of the lithium-ion secondary battery after high-temperature storage = [discharge capacity of the lithium-ion secondary battery after high-temperature storage / discharge capacity of the lithium-ion secondary battery before high-temperature storage] × 100%.

[0138] (2) High temperature cycle performance test of lithium-ion secondary batteries:

[0139] The high-temperature cycling performance of the lithium-ion secondary batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 was tested. The specific method was as follows: at 45°C, the lithium-ion secondary batteries were first charged to 3.65V at a constant current of 0.5C, then charged at a constant voltage of 3.65V until the current reached a cutoff of 0.05C, and then discharged to 2.5V at a constant current of 0.5C. This constituted one charge-discharge cycle, and the discharge capacity was the discharge capacity of the first cycle. The lithium-ion secondary batteries were subjected to a cyclic charge-discharge test in the above manner, and the discharge capacity of the 1000th cycle was taken. The capacity retention (%) of the lithium-ion secondary battery after 1000 cycles = [discharge capacity of the 1000th cycle / discharge capacity of the first cycle] × 100%.

[0140] (3) High temperature cycling expansion growth rate test of silicon-doped graphite negative electrode of lithium-ion secondary battery:

[0141] The high-temperature cycling performance of the lithium-ion secondary batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 was tested. The specific method was as follows: at 45°C, the lithium-ion secondary batteries were first charged to 3.65V at a constant current of 0.5C, then charged at a constant voltage of 3.65V until the current reached a cutoff of 0.05C. At 100% SOC, the cells were disassembled and the thickness of the fully charged silicon-doped graphite negative electrode sheet was measured using a micrometer. This thickness was measured after the cells were first removed from the production line. The lithium-ion secondary batteries were subjected to cyclic charge and discharge tests as described above, and the cells after the 1000th cycle were sampled. The expansion growth rate (%) of the fully charged negative electrode sheet of the lithium-ion secondary battery after 1000 cycles = [thickness of the negative electrode sheet at the 1000th cycle / thickness of the fully charged negative electrode sheet before the cycle] × 100% - 100%.

[0142] (4) High-temperature storage gas production performance test of lithium-ion secondary batteries:

[0143] At 25°C, the lithium-ion secondary batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were first charged to 3.65V at a constant current of 0.5C. They were then charged at a constant voltage of 3.65V until the current reached 0.05C, and then discharged at a constant current of 0.5C to 2.5V. This discharge capacity represents the discharge capacity of the lithium-ion secondary battery before high-temperature storage. The lithium-ion secondary batteries were then charged to 3.65V at a constant current of 0.5C, and then charged at a constant voltage of 3.65V until the current reached 0.05C, fully charging the batteries. The volume of the batteries was measured using the water displacement method, and the thickness of the batteries was measured using a micrometer.

[0144] The lithium-ion batteries were then stored at 60°C for 90 days using the above experimental method. After storage, the lithium-ion secondary batteries were placed in a 25°C environment and the battery volume was measured using the water displacement method. Specifically, a beaker of pure water was placed on a balance and weighed, recording it as reading 1. The battery before storage (fresh battery) or after storage was then immersed in the water in the beaker and weighed, recording it as reading 2. The volume of the battery before storage (fresh battery) or after storage was subtracted from reading 1. The density of water is 1 mg / mL, and a reading of 1 mL corresponds to a volume of 1 mL before storage (fresh battery) or after storage. Therefore, if the battery immersed in water is before storage, then reading 2 minus reading 1 is the volume of the battery before storage, and if the battery immersed in water is after storage, then reading 2 minus reading 1 is the volume of the battery after storage. The volume after storage / volume before storage is the ratio of the volume of the battery after storage to the volume of the battery before storage. The thickness of the battery was measured with a micrometer. The lithium-ion secondary battery was then discharged at a constant current of 0.5C to 2.5V. It was then charged at a constant current of 0.5C to 3.65V. It was further charged at a constant voltage of 3.65V until the current dropped to 0.05C. The battery was then discharged at a constant current of 0.5C to 2.5V. The final discharge capacity was the discharge capacity of the lithium-ion secondary battery after high-temperature storage. Battery volume expansion (%) = (volume after storage / volume before storage - 1) × 100%.

[0145] The test results are shown in Table 2.

[0146] Table 2 Lithium-ion battery performance test results corresponding to different electrolytes

[0147]

[0148] It can be seen from the above table that ① Examples 1 to 11 of the present invention achieve overall good electrochemical performance under the conditions of satisfying the above W1, W2, and S1 relationships: in the lithium ion battery system of the graphite-doped silicon negative electrode (S1), fluoroethylene carbonate (FEC, W1%) and acetylsulfonamide compound (W2%) and other additives are added to the electrolyte at the same time, and the expansion behavior, cycle life and high-temperature storage performance of the silicon-carbon negative electrode are improved through the synergistic effect of FEC and acetylsulfonamide compound, and the gas production is significantly reduced; ② From the comparison between Example 1 and Comparative Example 1, it can be seen that compared with the system without adding potassium acesulfame, the system has a relatively good electrochemical performance. Compared with the battery with the addition of potassium acesulfame, the capacity retention rate of the lithium-ion secondary battery stored at 60°C increases, the storage gas production decreases, the cycle capacity retention rate is improved, and the expansion rate of the negative electrode plate in the later stage of the cycle is also reduced, which is beneficial to improving the battery life; ③ Comparing Example 1 with Examples 6 and 7, the main active group is the acesulfame root, so the sodium salt of acesulfame and the lithium salt and potassium salt can be tried in the lithium-ion battery respectively, all of which can improve the performance of the battery; ④ Comparing Example 1 with Comparative Example 3, it can be obtained that the combination of potassium acesulfame and fluoroethylene carbonate in the battery plays a vital role in the battery performance.

[0149] In the above description of this specification, the description with reference to the terms "one embodiment", "another embodiment" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are mutually inconsistent. In addition, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0150] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The positive electrode includes a positive electrode active material; the positive electrode active material includes lithium iron phosphate; The negative electrode includes a negative electrode active material; the negative electrode active material includes graphite and silicon-carbon composite material; The electrolyte comprises: a lithium salt, a solvent and an additive; the additive comprises fluoroethylene carbonate and sulfacetamide; And the following conditions are met: W1×W2≥β×(S1 / 5%) γ ; Among them, W1% is the mass percentage of fluoroethylene carbonate in the electrolyte, W2% is the mass percentage of acetylsulfonamide compound in the electrolyte, S1 is the mass percentage of silicon-carbon composite material in the negative electrode active material, β=0.2~0.5, γ=1.2~1.

5.

2. The lithium-ion battery according to claim 1, wherein The W1% is 5% to 10%; and / or, the W2% is 0.2% to 1%; and / or, the S1 is 1% to 7.5%.

3. The lithium-ion battery according to claim 1, wherein The D50 particle size of the lithium iron phosphate is 2 to 5 μm; And / or, the surface of the lithium iron phosphate is coated with a nitrogen-doped carbon layer; and / or, the thickness of the nitrogen-doped carbon layer is 2 to 8 nm; and / or, the nitrogen doping concentration of the nitrogen-doped carbon layer is 3 to 8 at %; And / or, the coating completeness of the nitrogen-doped carbon layer is ≥95%.

4. The lithium-ion battery according to claim 1, wherein The positive electrode further includes a conductive agent and a binder; And / or, in the positive electrode, the mass ratio of lithium iron phosphate, conductive agent and binder is (90-99): (0.5-5): (0.5-5).

5. The lithium-ion battery according to claim 1, wherein The silicon-carbon composite material includes a carbon-coated silicon composite material; the carbon-coated silicon composite material includes porous silicon microspheres and a carbon coating layer coated on the surface of the porous silicon microspheres; and / or the thickness ratio of the porous silicon microspheres to the carbon coating layer is (900-1100):

1.

6. The lithium-ion battery according to claim 1, wherein The negative electrode further comprises a conductive agent, a thickener and a binder; And / or, in the negative electrode, the mass ratio of graphite, silicon-carbon composite material, conductive agent, thickener and binder is (84.5-97.4): (1-10): (0.5-2): (0.1-0.5): (1-3).

7. The lithium-ion battery according to claim 1, wherein The lithium salt includes lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide; And / or, the mass percentage of the lithium salt in the electrolyte is 4% to 26%.

8. The lithium-ion battery according to claim 1, wherein The solvent is a superconducting fast-charging solvent; and / or the superconducting fast-charging solvent has a kinematic viscosity of ≤5 mPa·s at room temperature; and / or the superconducting fast-charging solvent has a room temperature conductivity of ≥10 mS / cm; And / or, the mass percentage of the solvent in the electrolyte is 60% to 90%.

9. The lithium-ion battery according to claim 1, wherein The additives also include other additives; the other additives include vinylene carbonate, vinyl ethylene carbonate, difluoroethylene carbonate, bisethylene carbonate, vinyl sulfate, propylene sulfate, 1,3-propanesulfonate, 1,4-butanesulfonate, vinyl bissulfate, dimethyl methanesulfonate, vinyl bissulfate, lithium difluorophosphate, lithium nitrate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorooxalatophosphate, lithium tetrafluorooxalatophosphate, lithium tetrafluoroborate, lithium difluorosulfonylimide, lithium fluorosulfonate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tetravinylsilane or one or more; And / or, the mass percentage of the other additives in the electrolyte is 0.8% to 3%.

10. An electrical device, characterized in that: A lithium-ion battery comprising the lithium-ion battery according to any one of claims 1 to 9.

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