Electrolyte, battery, battery pack and electric device

Abstract

This invention provides an electrolyte, a battery, a battery pack, and an electrical device. The electrolyte includes additives, including fluorocarbonate, unsaturated carbonate, a first sulfide additive, a second sulfide additive, and an anhydride additive. The first sulfide additive includes sulfonate compounds; the second sulfide additive includes sulfite compounds and / or sulfate compounds. Based on the mass of the electrolyte, the mass percentage of each component is as follows: fluorocarbonate m1%, 1.5≤m1≤5; unsaturated carbonate m2%, 1.5≤m2≤3; first sulfide additive m3%, 0.5≤m3≤2; second sulfide additive m4%, 0.5≤m4≤2; anhydride additive m5%, 0.3≤m5≤0.8; and satisfies 1≤(m1+m2) / (m3+m4+m5)≤3. This invention can effectively suppress gas generation at high temperatures in the battery and improve the cycle performance and storage performance of the battery under high-temperature conditions.

Description

Technical Field

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

[0002] In the evolution of battery technology, electrolyte optimization plays a crucial role in improving overall battery performance. The electrolyte is not only the core medium for ion conduction in the battery, but also directly affects battery safety, cycle life, and adaptability under different temperature conditions. With the rapid development of electric vehicles, portable electronic devices, and large-scale energy storage systems, the demand for high-performance batteries is constantly increasing. However, in current technologies, the cycle performance and storage performance of batteries under high-temperature conditions are generally poor, easily leading to problems such as rapid capacity decay and shortened cycle life, seriously affecting the stability and service life of the battery. Therefore, how to effectively improve the cycle performance and storage performance of batteries under high-temperature conditions has become an important direction for current research and development in the battery field. Summary of the Invention

[0003] This invention provides an electrolyte, a battery, a battery pack, and an electrical device. This invention can effectively suppress gas generation in the battery at high temperatures and improve the battery's cycle performance and storage performance under high-temperature conditions.

[0004] This invention provides an electrolyte comprising additives, including fluorocarbonate, unsaturated carbonate, a first sulfide additive, a second sulfide additive, and an anhydride additive; the first sulfide additive includes sulfonate compounds; the second sulfide additive includes sulfite compounds and / or sulfate compounds; based on the mass of the electrolyte, the mass percentage of the fluorocarbonate is m1%, wherein 1.5 ≤ m1 ≤ 5; the mass percentage of the unsaturated carbonate is m2%, wherein 1.5 ≤ m2 ≤ 3; the mass percentage of the first sulfide additive is m3%, wherein 0.5 ≤ m3 ≤ 2; the mass percentage of the second sulfide additive is m4%, wherein 0.5 ≤ m4 ≤ 2; the mass percentage of the anhydride additive is m5%, wherein 0.3 ≤ m5 ≤ 0.8; and satisfying 1 ≤ (m1 + m2) / (m3 + m4 + m5) ≤ 3.

[0005] According to one embodiment of the present invention, the sulfonate compound includes methylene disulfonate; and / or, the sulfite compound includes propylene sulfite; and / or, the sulfate compound includes vinyl sulfate; and / or, the fluorocarbonate includes fluoroethylene carbonate and / or difluoroethylene carbonate; and / or, the unsaturated carbonate includes vinylene carbonate and / or ethylene ethylene carbonate; and / or, the anhydride additive includes one or more of maleic anhydride, citrate anhydride, and phenylsuccinic anhydride.

[0006] According to one embodiment of the present invention, the electrolyte further includes an electrolyte salt and / or an organic solvent.

[0007] According to one embodiment of the present invention, the electrolyte salt includes a first lithium salt and a second lithium salt; the first lithium salt includes lithium hexafluorophosphate; the second lithium salt includes one or more of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorodioxarate phosphate.

[0008] According to one embodiment of the present invention, the mass ratio of the second lithium salt to the first lithium salt is (2%~16%):1; and / or, the mass percentage content of the first lithium salt in the electrolyte is 12%~15%; and / or, the mass percentage content of the second lithium salt in the electrolyte is 0.3%~1.5%.

[0009] According to one embodiment of the present invention, the electrolyte contains 80% to 86% by mass of organic solvent; and / or, the organic solvent includes one or more of carbonate solvents, fluorinated ether solvents, and carboxylic acid ester solvents.

[0010] The present invention also provides a battery, comprising a positive electrode, a negative electrode, and an electrolyte; the electrolyte comprising the electrolyte described above.

[0011] According to one embodiment of the present invention, the negative electrode sheet comprises a silicon-based negative electrode active material.

[0012] The present invention also provides a battery pack comprising at least two batteries as described above.

[0013] The present invention also provides an electrical device, including the battery or the battery pack described above.

[0014] This invention provides an electrolyte, a battery, a battery pack, and an electrical device. The electrolyte includes additives, which include fluorocarbonate, unsaturated carbonate, a first sulfide additive, a second sulfide additive, and an anhydride additive. The first sulfide additive includes sulfonate compounds; the second sulfide additive includes sulfite compounds and / or sulfate compounds. Based on the mass of the electrolyte, the mass percentage of each component is as follows: fluorocarbonate m1%, 1.5≤m1≤5; unsaturated carbonate m2%, 1.5≤m2≤3; first sulfide additive m3%, 0.5≤m3≤2; second sulfide additive m4%, 0.5≤m4≤2; anhydride additive m5%, 0.3≤m5≤0.8; and satisfies 1≤(m1+m2) / (m3+m4+m5)≤3. By controlling the various additives within a suitable content and specific ratio range, the additives work synergistically to form a dense, low-resistance, and highly tough SEI film on the electrode surface, reducing active ion loss and side reactions, while removing moisture, inhibiting the generation of acidic corrosion gases and the dissolution of metal ions, thereby significantly suppressing high-temperature gas generation in the battery and improving the battery's high-temperature cycling and high-temperature storage performance. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0016] In related technologies, batteries generally exhibit poor cycle performance and storage performance under high-temperature conditions, easily leading to problems such as rapid capacity decay and shortened cycle life, which seriously affect the battery's stability and service life. Therefore, effectively improving the cycle performance and storage performance of batteries under high-temperature conditions has become an important direction for current battery research and development.

[0017] Taking silicon-based anode active materials as an example, the large volume change of silicon-based anode active materials during charge and discharge can easily lead to SEI film rupture. This exposes the anode surface back into the electrolyte, causing the anode to react with the electrolyte to repair the SEI film. This results in increased SEI film impedance, reduced active lithium ions, accelerated lifespan decay, and the generation of a large amount of gas. Electrolyte additives can form a thin film on the surfaces of both the positive and negative electrodes. By designing a reasonable electrolyte, the density and toughness of the SEI film can be improved, delaying its rupture during charge and discharge, reducing side reactions between the electrolyte and the anode, thereby improving the lifespan of silicon-based anode batteries and reducing high-temperature gas generation.

[0018] In view of this, embodiments of the present invention provide an electrolyte comprising additives, including fluorocarbonates, unsaturated carbonates, a first sulfide additive, a second sulfide additive, and an anhydride additive; the first sulfide additive includes sulfonate compounds; the second sulfide additive includes sulfite compounds and / or sulfate compounds, wherein the first sulfide additive includes methylene disulfonate (MMDS); the second sulfide additive includes propylene sulfite (PS) and / or vinyl sulfate (DTD); the electrolyte... Based on mass, the mass percentage of fluorocarbonate is m1%, where 1.5≤m1≤5; the mass percentage of unsaturated carbonate is m2%, where 1.5≤m2≤3; the mass percentage of the first sulfur-based additive is m3%, where 0.5≤m3≤2; the mass percentage of the second sulfur-based additive is m4%, where 0.5≤m4≤2; the mass percentage of acid anhydride additive is m5%, where 0.3≤m5≤0.8; and satisfies 1≤(m1+m2) / (m3+m4+m5)≤3.

[0019] This invention utilizes a combination of various functional additives and controls the amount and proportion of each additive to significantly suppress gas generation at high temperatures by leveraging the individual effects and synergistic effects of different additives, thereby improving the cycle performance and storage performance of the battery under high-temperature conditions. The specific analysis is as follows: 1) The mass percentage of fluorinated carbonate is m1% (1.5≤m1≤5), which helps to reduce the generation of acidic corrosive gases such as HF while reducing the SEI film impedance; 2) The mass percentage of unsaturated carbonate is m2% (1.5≤m2≤3), which helps to form a SEI film with excellent toughness and dense structure, reducing the consumption of active lithium and gas generation; 3) The mass percentage of the first sulfide additive is m3% (0.5≤m3≤2), and the mass percentage of the second sulfide additive is m4% (0.5≤m4≤2). The two are combined to synergistically suppress battery gas generation, suppress metal ion dissolution, and significantly improve the high-temperature performance of the battery; 4) The mass percentage of acid anhydride additive is m5% (0.3≤m5≤0.8), which can react with water in the electrolyte, reduce the generation of acidic corrosive gases such as HF, avoid the electrode being corroded by acidic gases, and thus suppress side reactions and gas generation. 5) The mass percentage content of each of the above additive components satisfies the ratio of 1 ≤ (m1 + m2) / (m3 + m4 + m5) ≤ 3, which is beneficial for achieving a balance between film stability, gas generation suppression, and water and acid removal capabilities. This ensures both a dense and low-impedance SEI film and continuous suppression of gas generation and metal ion dissolution at high temperatures. Therefore, by controlling the dosage and proportion of each additive, and leveraging the individual effects and synergistic effects of different additives, high-temperature gas generation in the battery can be effectively suppressed, thereby improving the battery's cycle performance and storage performance under high-temperature conditions.

[0020] For example, the mass percentage m1 of fluorocarbonate in the electrolyte can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, etc.

[0021] For example, the mass percentage m2 of unsaturated carbonate in the electrolyte can be 1.5, 1.7, 2, 2.3, 2.5, 2.7 or 3, etc.

[0022] For example, the mass percentage m3 of the first sulfide additive in the electrolyte can be 0.5, 0.7, 1, 1.3, 1.5, 1.7 or 2, etc.

[0023] For example, the mass percentage m4 of the second sulfide additive in the electrolyte can be 0.5, 0.7, 1, 1.3, 1.5, 1.7 or 2, etc.

[0024] For example, the mass percentage m5 of the second sulfide additive in the electrolyte can be 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, etc.

[0025] For example, (m1+m2) / (m3+m4+m5) can be 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or 3, etc.

[0026] In some embodiments, the sulfonate compound includes methylene methane disulfonate (MMDS). MMDS has excellent film-forming properties and can participate in the formation of the SEI film on the electrode surface, significantly reducing the impedance of the SEI film. At the same time, it can effectively suppress gas generation reactions under high-temperature battery conditions, reduce the generation of acidic corrosive gases such as HF, and inhibit the dissolution of metal ions, thereby synergistically improving the high-temperature cycle performance and storage performance of the battery. In addition, its good chemical stability can further suppress the occurrence of side reactions.

[0027] In some embodiments, sulfite compounds include propylene sulfite (PS). PS facilitates preferential reduction reactions on the electrode surface, forming a tough, dense, and stable SEI film that effectively blocks contact between the electrolyte and the electrode active materials, reducing the consumption of active ions and gas generation. Furthermore, PS also possesses a certain water-removing capacity, thereby suppressing side reactions and further improving the battery's stability and cycle life at high temperatures.

[0028] In some embodiments, the sulfate ester compound includes vinyl sulfate (DTD). DTD has strong redox activity and can rapidly form a dense and uniform SEI film on the electrode surface, effectively inhibiting electrolyte decomposition and high-temperature gas generation. At the same time, it can significantly inhibit metal ion dissolution and reduce electrode material corrosion and pulverization. In addition, DTD can improve the interfacial wettability of the electrolyte, enhance ion migration rate, and optimize the balance between film formation stability and water and acid removal capabilities, thereby further improving the battery's cycle performance and long-term storage performance.

[0029] In this embodiment of the invention, the fluorocarbonate includes fluoroethylene carbonate (FEC) and / or difluoroethylene carbonate (DFEC). It can preferentially participate in film formation on the negative electrode surface, effectively reducing SEI film impedance, while simultaneously inhibiting electrolyte decomposition, reducing the generation of acidic substances such as HF, and further improving the high-temperature stability of the battery.

[0030] In some embodiments, the unsaturated carbonate includes vinylene carbonate (VC) and / or ethylene ethylene carbonate (VEC). This facilitates the formation of a tough and dense SEI film, suppresses solvent co-intercalation and active lithium loss, and further improves interface stability and cycle life.

[0031] In some embodiments, the anhydride additives include one or more of maleic anhydride (MA), citrate anhydride (CA), and phenylsuccinic anhydride (PA). This facilitates better removal of trace amounts of moisture from the electrolyte and electrode surfaces, inhibits the generation of acidic corrosion gases, reduces side reaction gas production, and thus significantly improves the battery's high-temperature storage performance.

[0032] In this embodiment of the invention, the characterization method for the additives used in the battery is as follows: The fully discharged battery is disassembled, and the positive and negative electrode sheets are removed separately. They are then cleaned by immersion in dimethyl carbonate (DMC) or anhydrous ethanol to remove residual electrolyte and electrolyte salts from the surface. X-ray photoelectron spectroscopy (XPS) is performed on the dried electrode sheets to analyze the main components of the CEI film on the positive electrode surface and the SEI film on the negative electrode surface. Based on this, the film-forming behavior and types of additives in the electrolyte are qualitatively determined. Specifically, the main film-forming product of VC in the SEI film is polyvinyl carbonate, and the main film-forming product of DTD is... The main film-forming products of MMDS are .

[0033] In this embodiment of the invention, the electrolyte further includes electrolyte salts and / or organic solvents. Electrolyte salts provide high ionic conductivity, ensuring efficient ion conduction within the battery, and also contribute to the formation of stable SEI and CEI films on the electrode surface, protecting the electrode materials and extending battery life. Organic solvents effectively dissolve electrolyte salts, forming a uniform electrolyte and improving ionic conductivity. They also improve battery performance at low temperatures, maintain chemical stability at high temperatures, reduce decomposition and side reactions, and enhance battery safety.

[0034] In some embodiments, the electrolyte salt includes a first lithium salt and a second lithium salt. The first lithium salt includes lithium hexafluorophosphate; the second lithium salt includes one or more of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate phosphate. Lithium hexafluorophosphate, as the first lithium salt, imparts high ionic conductivity to the electrolyte, thus improving both the rate performance and cycle stability of the battery. Combining one or more of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalate phosphate as the second lithium salt allows it to participate in the formation of a stable, dense, and low-resistivity interfacial film on the electrode surface, suppressing electrolyte decomposition and side reaction gas generation, and improving the battery's high-temperature cycling and storage performance. The synergistic effect of the first and second lithium salts, while ensuring high ionic conductivity of the electrolyte, further optimizes the electrode interface structure, significantly improving the battery's cycle performance and storage performance under high-temperature conditions.

[0035] In some embodiments, the mass ratio of the second lithium salt to the first lithium salt is (2%~16%):1, which can ensure that the electrolyte has high ionic conductivity and form a stable and dense interface film on the electrode surface, further improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0036] For example, the mass ratio of the second lithium salt to the first lithium salt can be 2%:1, 5%:1, 7%:1, 9%:1, 12%:1, 14%:1, or 16%:1, etc.

[0037] This invention, through controlling the mass percentages of the first and second lithium salts in the electrolyte, ensures that the electrolyte possesses sufficient and stable ionic conductivity. This facilitates the formation of a stable, dense, and low-resistance SEI / CEI film on the electrode surface, effectively suppressing side reactions and high-temperature gas generation, thereby further improving the battery's high-temperature cycle performance and high-temperature storage performance. In some embodiments, the mass percentage of the first lithium salt is 12%~15%, and the mass percentage of the second lithium salt is 0.3%~1.5%.

[0038] For example, the mass percentage of the first lithium salt in the electrolyte can be 12%, 12.2%, 12.4%, 12.6%, 12.8%, 13%, 13.2%, 13.4%, 13.6%, 13.8%, 14%, 14.2%, 14.4%, 14.6%, 14.8%, or 15%, etc.

[0039] For example, the mass percentage of the second lithium salt in the electrolyte can be 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, or 1.5%, etc.

[0040] In this embodiment of the invention, the mass percentage of organic solvent in the electrolyte is 80%~86%. This helps improve the stability of the electrolyte system, keeps the electrolyte viscosity moderate, and enhances ion transport efficiency.

[0041] For example, the mass percentage of organic solvent in the electrolyte can be 80%, 81%, 82%, 83%, 84%, 85%, or 86%, etc.

[0042] In this embodiment of the invention, the organic solvent includes one or more of carbonate solvents, fluorinated ether solvents, and carboxylic acid ester solvents. Carbonate solvents provide good solubility and electrochemical stability, fluorinated ether solvents improve the battery's flame retardancy and high-temperature stability, and carboxylic acid ester solvents enhance the electrolyte's wettability and low-temperature performance. By combining these organic solvents, the solubility, conductivity, wettability, and safety of the electrolyte can be synergistically balanced, providing favorable conditions for the formation of a stable and dense interfacial film, further suppressing high-temperature gas generation, and improving the battery's high-temperature cycling and high-temperature storage performance.

[0043] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0044] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate (EC) combined with ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). Further, the mass percentage of EC in the electrolyte is 15-30%.

[0045] In some embodiments, the carboxylic acid ester solvent can be linear. The linear structure is beneficial for further reducing electrolyte viscosity, increasing ion transport rate, and improving electrode wettability, thereby synergistically improving the rate performance and low-temperature discharge performance of the battery.

[0046] This invention also provides a method for preparing the above-mentioned electrolyte, which is a common method used by those skilled in the art. The method involves mixing the electrolyte salt, organic solvent and additives evenly.

[0047] This invention also provides a battery comprising a positive electrode, a negative electrode, and the aforementioned electrolyte. This battery offers advantages corresponding to the aforementioned electrolyte, which will not be elaborated further.

[0048] In this embodiment of the invention, the battery may be a liquid battery, specifically a lithium-ion secondary battery, but is not limited thereto.

[0049] In addition to the electrolyte, positive electrode, and negative electrode, the battery of the present invention also includes a separator. The present invention does not limit the specific types and structures of the positive electrode, negative electrode, and separator.

[0050] Optionally, the positive electrode sheet includes a positive current collector and a positive active material layer located on one or both sides of the positive current collector, the positive active material layer including a positive active material. The positive current collector used includes aluminum foil; the positive active material includes at least one of lithium iron manganese phosphate (LFMP), ternary materials (NCM), and lithium iron phosphate (LFP), wherein lithium iron manganese phosphate includes LiFe... 0.4 Mn 0.6 PO4, NCM including LiNi 0.7 Co 0.1 Mn 0.2 O2; the positive electrode active material layer also includes a positive electrode binder, a positive electrode conductive agent, or other optional positive electrode additives. The positive electrode binder may be selected from at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride, water-based acrylic resin, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polyacryl alcohol, ethylene-vinyl acetate copolymer (EVA), polyethylene ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB); the positive electrode conductive agent may be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, Ketjen black, carbon dots, conductive graphite, carbon nanotubes, Super P (SP), and carbon nanofibers.

[0051] In some embodiments, the bifacial areal density of the positive electrode is 290~450 g / m³. 2 .

[0052] For example, the bifacial areal density of the positive electrode can be 290 g / m². 2 310 g / m 2 330 g / m 2 350 g / m 2 370 g / m2 390 g / m 2 410 g / m 2 430 g / m 2 Or 450g / m 2 wait.

[0053] In some embodiments, the compaction density of the positive electrode sheet is 2.3~3.4 g / cm³. 3 .

[0054] For example, the compaction density of the positive electrode can be 2.3 g / cm³. 3 2.5 g / cm 3 2.7 g / cm 3 2.9 g / cm 3 3.1g / cm 3 Or 3.4g / cm 3 wait.

[0055] In this embodiment of the invention, the bifacial areal density of the positive electrode sheet refers to the mass of the bifacial positive electrode active material layer per unit area (excluding the positive electrode current collector). Bifacial areal density = (mass of the positive electrode sheet - mass of the positive electrode current collector) / area of ​​the positive electrode sheet. The area of ​​the positive electrode sheet is the single-sided area of ​​the positive electrode active material layer coating region.

[0056] In this embodiment of the invention, the compaction density of the positive electrode sheet refers to the mass of the double-sided positive electrode active material layer per unit volume. The compaction density of the positive electrode sheet = the double-sided surface density of the positive electrode sheet / (the thickness of the positive electrode sheet - the thickness of the positive electrode current collector).

[0057] Optionally, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material. The negative electrode current collector includes at least one of copper foil, nickel foil, or carbon-based current collector; the negative electrode active material includes silicon-based negative electrode active material; the negative electrode active material includes a mixture of graphite and silicon oxide (SiO) material or a mixture of graphite and silicon carbon (SiC) material; the negative electrode active material layer also includes a negative electrode binder, a negative electrode conductive agent, or other optional negative electrode additives. The negative electrode binder may be selected from at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride, water-based acrylic resin, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyvinylpyrrolidone, hydroxypropyl methylcellulose, polytetrafluoroethylene (PTFE), polyacryl alcohol, ethylene-vinyl acetate copolymer (EVA), polyethylene ether, polyacrylate, polyacrylic acid (PAA), polyurethane, polyacrylate, styrene-acrylate copolymer, carboxymethyl cellulose (CMC), epoxy resin, polyvinyl alcohol (PVA), polyhexafluoropropylene, styrene-butadiene copolymer, sodium polymethyl cellulose, and polyvinyl butyral (PVB); the negative electrode conductive agent may be selected from at least one of superconducting carbon, graphene, acetylene black, conductive carbon black, Ketjen black, carbon dots, conductive graphite, carbon nanotubes, Super P (SP), and carbon nanofibers.

[0058] In some embodiments, the bifacial areal density of the negative electrode is 160~230 g / m³. 2 .

[0059] For example, the bifacial areal density of the negative electrode can be 160 g / m². 2 170 g / m 2 180 g / m 2 190 g / m 2 200 g / m 2 210 g / m 2 220 g / m 2 Or 230g / m 2 wait.

[0060] In some embodiments, the compaction density of the negative electrode sheet is 1.3~1.65 g / cm³. 3 .

[0061] For example, the compaction density of the negative electrode can be 1.3 g / cm³. 3 1.35 g / cm 3 1.4 g / cm 3 1.5 g / cm 3 1.55g / cm 3 Or 1.65g / cm 3 wait.

[0062] In this embodiment of the invention, the double-sided areal density of the negative electrode sheet refers to the mass of the double-sided negative electrode active material layer per unit area (excluding the positive electrode current collector). Double-sided areal density = (mass of the negative electrode sheet - mass of the positive electrode current collector) / area of ​​the negative electrode sheet. The area of ​​the negative electrode sheet is the single-sided area of ​​the negative electrode active material layer coating region.

[0063] In this embodiment of the invention, the compaction density of the negative electrode sheet refers to the mass of the double-sided negative electrode active material layer per unit volume. The compaction density of the negative electrode sheet = the double-sided surface density of the negative electrode sheet / (the thickness of the negative electrode sheet - the thickness of the negative electrode current collector).

[0064] Alternatively, the membrane material can be selected from polypropylene membrane (PP), polyethylene membrane (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun membrane (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven membrane, and membrane with ceramic coating.

[0065] The battery of the present invention can be prepared using conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and the cell can be obtained by stacking or winding. Then, the battery can be obtained by baking, liquid injection, formation and packaging.

[0066] During the battery manufacturing process, the baking temperature is 80~120℃, the baking time is 12~24h, the electrolyte injection temperature is 25~40℃, the formation current is 0.05C~0.2C, and the formation time is 4~6h.

[0067] It should be noted that during the preparation process of the battery provided by the present invention, the amount of each substance added may deviate from the content of each substance obtained from the electrolyte obtained after disassembling the battery, but it is within the error range. Therefore, the amount of each substance added during the battery preparation process is basically consistent with the content of each substance in the electrolyte.

[0068] This invention also provides a battery pack comprising at least two batteries as described above. This battery pack has advantages corresponding to the batteries described above, which will not be elaborated further.

[0069] The battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0070] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the battery described above, which will not be elaborated further.

[0071] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), automobile chassis, electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations.

[0072] The present invention will be further described below through specific embodiments.

[0073] Example 1

[0074] 1. Preparation of positive electrode sheet

[0075] Lithium manganese iron phosphate (chemical formula LiFe) 0.4 Mn 0.6 PO4) and ternary materials (chemical formula LiNi) 0.7 Co 0.1 Mn 0.2 O2) is uniformly mixed at a mass ratio of 8:2 to serve as the positive electrode active material; the above positive electrode active material, positive electrode binder polyvinylidene fluoride (PVDF), conductive agent carbon black, and carbon nanotubes are added to NMP at a mass ratio of 95.5:2:1.5:1, and mixed uniformly to prepare a positive electrode slurry; the positive electrode slurry is coated on both sides of an aluminum foil, and after baking and rolling, a positive electrode sheet is obtained, with a double-sided areal density of 400 g / m². 2 The compaction density of the positive electrode is 2.6 g / cm³. 3 .

[0076] 2. Preparation of negative electrode sheet

[0077] Artificial graphite (anode active material), silicon carbide, styrene-butadiene rubber (SBR) binder, carboxymethyl cellulose (CMC) thickener, carbon black (conductive agent), and single-walled carbon nanotubes were mixed uniformly in water at a mass ratio of 91.5:8.5:2:1.5:1:0.1 to obtain a cathode slurry. This cathode slurry was then coated onto both sides of a copper foil, and the resulting sheet was prepared by baking and rolling. The anode sheet had a double-sided areal density of 180 g / m². 2 The compaction density of the negative electrode is 1.6 g / cm³. 3 .

[0078] 3. Preparation of electrolyte

[0079] In an argon atmosphere glove box, 12.5 wt% lithium hexafluorophosphate ( ) with 0.5wt% lithium difluorophosphate ( The electrolyte is dissolved in 30 wt% ethylene carbonate (EC) and 50.5 wt% ethyl methyl carbonate (EMC) of the total electrolyte mass. Then, 2 wt% fluoroethylene carbonate (FEC), 2 wt% vinylene carbonate (VC), 1 wt% methanedisulfonate (MMDS), 1 wt% ethylene sulfate (DTD) and 0.5 wt% maleic anhydride (MA) are added to the system. After stirring and dissolving, the electrolyte is obtained. The mass percentages of the above electrolyte salts, organic solvents and additives are based on the mass of the electrolyte.

[0080] 4. Battery manufacturing

[0081] The above-mentioned positive electrode sheet, PP separator, and negative electrode sheet are stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After drying the packaged battery, the electrolyte is injected into the dried battery. After resting, formation, and secondary sealing, the lithium-ion battery is completed. The battery's design capacity is 1.7Ah (the rated capacity that the battery is expected to output according to the design specifications is 1.7Ah). The formation mechanism is as follows: constant current charging at 0.05C for 4 hours, constant current charging at 0.2C for 3 hours, constant current and constant voltage charging at 0.33C to 4.3V, and the cutoff current is 0.05C. The capacity grading mechanism is as follows: constant current and constant voltage charging at 0.33C to 4.3V, cutoff current at 0.05C, resting for 10 minutes, and then discharging at 0.33C constant current to 2.5V.

[0082] Example 2

[0083] The battery preparation method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out by replacing FEC with an equal amount of difluoroethylene carbonate (DFEC).

[0084] Example 3

[0085] The battery preparation method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the DTD is replaced with an equal amount of propylene sulfite (PS) in the preparation of the electrolyte.

[0086] Example 4

[0087] The battery preparation method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out by replacing VC with an equal amount of ethylene ethylene carbonate (VEC).

[0088] Example 5

[0089] The battery preparation method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the preparation of the electrolyte is done by replacing MA with an equal amount of phenylsuccinic anhydride (PA).

[0090] Example 6

[0091] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, MA is replaced with an equal amount of citrate anhydride (CA).

[0092] Example 7

[0093] The battery preparation method in this embodiment is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out by replacing LiPO2F2 with lithium bisfluorosulfonylimide (LiFSI) in equal amounts.

[0094] Example 8

[0095] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, LiPO2F2 is replaced by an equal amount of lithium difluorodioxalate phosphate (LiDFOP).

[0096] Example 9

[0097] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of electrolyte, the mass percentage of FEC is increased from 2% to 5%, and the mass percentage of EMC is 47.5%.

[0098] Example 10

[0099] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of electrolyte, the mass percentage of FEC is increased from 2% to 4%, and the mass percentage of EMC is 48.5%.

[0100] Example 11

[0101] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, the mass percentage of VC is increased from 2% to 3%, and the mass percentage of EMC is 49.5%.

[0102] Example 12

[0103] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, the mass percentage of VC is reduced from 2% to 1.5%, and the mass percentage of EMC is 51%.

[0104] Example 13

[0105] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, the mass percentage of the first sulfur-based additive MMDS is increased from 1% to 1.5%, and the mass percentage of EMC is 50%.

[0106] Example 14

[0107] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, the mass percentage of the second sulfur-based additive DTD is increased from 1% to 1.5%, and the mass percentage of EMC is 50%.

[0108] Example 15

[0109] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of the electrolyte, the mass percentage of the first sulfur-based additive MMDS is reduced from 1% to 0.5%, and the mass percentage of EMC is 51%.

[0110] Example 16

[0111] The battery preparation method in this embodiment is basically the same as that in embodiment 1. The difference is that in step 3) the preparation of electrolyte, the mass percentage of MA is increased from 0.5% to 0.8%, and the mass percentage of EMC is 50.2%.

[0112] Example 17

[0113] The preparation method of the battery in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the content of LiPO2F2 is 2% and the content of EMC is 49% based on the total mass of the electrolyte.

[0114] Example 18

[0115] The method is basically the same as in Example 1, except that the mass percentage of FEC in the electrolyte is reduced from 2% to 1.5%, and the mass percentage of EMC is 51%.

[0116] Example 19

[0117] The method is basically the same as in Example 1, except that the mass percentage of MMDS in the electrolyte is increased from 1% to 2%, and the mass percentage of EMC is 49.5%.

[0118] Example 20

[0119] The method is basically the same as in Example 1, except that the mass percentage of DTD in the electrolyte is reduced from 1% to 0.5%, and the mass percentage of EMC is 51%.

[0120] Example 21

[0121] The method is basically the same as in Example 1, except that the mass percentage of DTD in the electrolyte is increased from 1% to 2%, and the mass percentage of EMC is 49.5%.

[0122] Example 22

[0123] The method is basically the same as in Example 1, except that the mass percentage of MA in the electrolyte is reduced from 0.5% to 0.3%, and the mass percentage of EMC is 50.7%.

[0124] Comparative Example 1

[0125] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation method is based on the total mass of the electrolyte, the mass percentage of FEC is 6% and the mass percentage of EMC is 46.5%.

[0126] Comparative Example 2

[0127] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3) electrolyte preparation, based on the total mass of the electrolyte, the mass percentage of FEC is 1% and the mass percentage of EMC is 51.5%.

[0128] Comparative Example 3

[0129] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation method is based on the total mass of the electrolyte, the mass percentage of VC is 4% and the mass percentage of EMC is 49.5%.

[0130] Comparative Example 4

[0131] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation method is based on the total mass of the electrolyte, the mass percentage of FEC is 1%, the mass percentage of VC is 0.5%, and the mass percentage of EMC is 53%.

[0132] Comparative Example 5

[0133] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out without adding MMDS, and the mass percentage of EMC is 51.5% based on the total mass of the electrolyte.

[0134] Comparative Example 6

[0135] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out without adding DTD, and the mass percentage of EMC is 51.5% based on the total mass of the electrolyte.

[0136] Comparative Example 7

[0137] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3) electrolyte preparation, based on the total mass of the electrolyte, the mass percentage of MA is 1.5% and the mass percentage of EMC is 50%.

[0138] Comparative Example 8

[0139] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the electrolyte preparation is carried out without adding MA, and the mass percentage of EMC is 51% based on the total mass of the electrolyte.

[0140] Comparative Example 9

[0141] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3), the mass percentage of MA is 0.15% and the mass percentage of EMC is 50.65% based on the total mass of the electrolyte.

[0142] Comparative Example 10

[0143] The preparation method of the battery in this comparative example is basically the same as that in Example 1. The difference is that in step 3) preparation of electrolyte, based on the total mass of electrolyte, the mass percentage of the first sulfur-based additive MMDS is 3%, the mass percentage of the second sulfur-based additive DTD is 0.3%, and the mass percentage of EMC is 49.2%.

[0144] Comparative Example 11

[0145] The battery preparation method in this comparative example is basically the same as that in Example 1. The difference is that in step 3) electrolyte preparation, based on the total mass of the electrolyte, the mass percentage of MMDS is 0.3%, the mass percentage of the second sulfide additive DTD is 3%, and the mass percentage of EMC is 49.2%.

[0146] Table 1 summarizes the types of the first lithium salt, the mass percentage of the first lithium salt in the electrolyte, the types of the second lithium salt, the mass percentage of the second lithium salt in the electrolyte, the types of fluorocarbonates, the mass percentage of fluorocarbonates in the electrolyte, the types of unsaturated carbonates, the mass percentage of unsaturated carbonates in the electrolyte, the types of the first sulfide additive, the mass percentage of the first sulfide additive in the electrolyte, the types of the second sulfide additive, the mass percentage of the second sulfide additive in the electrolyte, and the types of acid anhydride additives, and the mass percentage of acid anhydride additives in the electrolyte, for each embodiment and comparative example. Except for the differences shown in Table 1, the other conditions are basically the same.

[0147] Table 1

[0148]

[0149] The (m1+m2) / (m3+m4+m5) (hereinafter referred to as Y value) in the electrolytes of the above examples and comparative examples are summarized in Table 2.

[0150] The high-temperature cycling performance and high-temperature storage performance of the batteries prepared in the above embodiments and comparative examples were tested as follows, and the results are shown in Table 2:

[0151] 1) High-temperature cycling performance (capacity retention rate after 500 cycles at 45℃)

[0152] Place the battery in an ambient temperature of 45°C until the battery body temperature matches the ambient temperature. Charge it at a constant current and constant voltage rate of 0.5C to 4.25V, then discharge it at a constant current rate of 0.5C to 2.5V. Record the initial charge capacity and discharge capacity. Repeat the aforementioned charge and discharge cycle. Record the capacity retention rate after 500 cycles. If the capacity retention rate after 500 cycles is greater than 90%, the required 1000-cycle lifespan is achieved.

[0153] 2) High-temperature storage performance (capacity recovery rate after 196 days of storage at 60℃)

[0154] The battery was charged at a constant current and constant voltage of 0.33C to 4.3V, with a cutoff current of 0.05C, and then discharged at a constant current of 0.33C to 2.5V, yielding the initial discharge capacity C0. The battery was then charged at a constant current and constant voltage of 0.33C0 to 4.3V, with a cutoff current of 0.05C0, resulting in a fully charged battery. This fully charged battery was placed in a 60℃ constant temperature chamber, and its capacity was calibrated every 28 days. After 196 days of storage, the battery was discharged at a constant current of 0.33C0 to 2.5V, yielding the remaining capacity C1. The previously discharged battery was then charged at a constant current and constant voltage of 0.33C0 to 4.3V, with a cutoff current of 0.05C0; this charging and discharging cycle was repeated three times, and the discharge capacity of the third cycle was taken as the recovered capacity C1. 196The capacity recovery rate (%) after 196 days of storage at 60℃ is calculated as follows: (C...) 196 -C0) / C0×100%. Excellent high-temperature storage performance should meet the requirement that the capacity recovery rate is greater than 80% after 196 days of storage.

[0155] 3) Gas production volume after 84 days of storage at 60℃

[0156] Using Archimedes' principle, the battery is suspended by a dynamometer, and the dynamometer obtains a pulling force F0. Then, the battery is completely immersed in water, and the dynamometer obtains a pulling force F1. After being stored at 60°C for 84 days, the battery is suspended by a dynamometer and immersed in water again, and the dynamometer obtains a pulling force F2. The increase in unit capacity volume of the battery at this time is the gas production volume V (mL / Ah) after 84 days of storage at 60°C = (F1-F2) / (9.8C0), where C0 is the initial discharge capacity of the battery obtained from the above high-temperature storage performance test.

[0157] Table 2

[0158]

[0159] Analysis of Table 2 shows that, compared to Comparative Examples 1-11, the batteries in Examples 1-22 exhibit higher cycle performance, storage performance, or lower gas production. Specifically, the battery in Example 2 retained 92.1% of its capacity after 500 cycles at 45°C, and 81.4% of its capacity after 196 days of storage at 60°C. Furthermore, the gas production volume after 84 days of storage at 60°C was only 1.18 mL / Ah. In contrast, the comparative examples showed poor storage and cycle performance, and some even exhibited high gas production. Therefore, the electrolyte in this invention demonstrates high stability under high-voltage conditions, effectively improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0160] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to what has been described above. Various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An electrolyte, characterized in that, It includes additives, including fluorocarbonates, unsaturated carbonates, first sulfide additives, second sulfide additives, and acid anhydride additives; The first sulfur-based additive includes sulfonate compounds; the second sulfur-based additive includes sulfite compounds and / or sulfate compounds; Based on the mass of the electrolyte, the mass percentage of the fluorocarbonate is m1%, wherein 1.5 ≤ m1 ≤ 5; The mass percentage of the unsaturated carbonate is m2%, where 1.5 ≤ m2 ≤ 3; The mass percentage of the first sulfur-based additive is m3%, where 0.5 ≤ m3 ≤ 2; The second sulfur-based additive has a mass percentage content of m4%, where 0.5 ≤ m4 ≤ 2; The mass percentage of the acid anhydride additive is m5%, where 0.3 ≤ m5 ≤ 0.

8. And it satisfies 1≤(m1+m2) / (m3+m4+m5)≤3.

2. The electrolyte according to claim 1, characterized in that, The sulfonate compounds include methylene methane disulfonate; And / or, the sulfite compounds include propylene sulfite; And / or, the sulfate ester compounds include vinyl sulfate; And / or, the fluorocarbonate includes fluoroethylene carbonate and / or difluoroethylene carbonate; And / or, the unsaturated carbonates include vinylene carbonate and / or ethylene ethylene carbonate; And / or, the anhydride additives include one or more of maleic anhydride, citrate anhydride, and phenylsuccinic anhydride.

3. The electrolyte according to claim 1 or 2, characterized in that, The electrolyte also includes electrolyte salts and / or organic solvents.

4. The electrolyte according to claim 3, characterized in that, The electrolyte salt includes a first lithium salt and a second lithium salt; The first lithium salt includes lithium hexafluorophosphate; The second lithium salt includes one or more of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium difluorodioxarate phosphate.

5. The electrolyte according to claim 4, characterized in that, The mass ratio of the second lithium salt to the first lithium salt is (2%~16%):1; And / or, the mass percentage of the first lithium salt in the electrolyte is 12% to 15%; And / or, the mass percentage of the second lithium salt in the electrolyte is 0.3% to 1.5%.

6. The electrolyte according to any one of claims 3-5, characterized in that, The electrolyte contains 80% to 86% by mass of organic solvent. And / or, the organic solvent includes one or more of carbonate solvents, fluoroether solvents, and carboxylic acid ester solvents.

7. A battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte; the electrolyte includes the electrolyte according to any one of claims 1-6.

8. The battery according to claim 7, characterized in that, The negative electrode sheet includes a silicon-based negative electrode active material.

9. A battery pack, characterized in that, It includes at least two batteries as described in claim 7 or 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 7 or 8, or the battery pack as described in claim 9.

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