Sodium-ion battery and electric device

Abstract

The application relates to the technical field of sodium ion batteries, in particular to a sodium ion battery and a power utilization device, the sodium ion battery comprising an electrolyte, the electrolyte comprising a first additive, the first additive comprising a compound shown in formula 1: in the sodium ion battery, the fluorophosphate compound shown in formula 1 added into the electrolyte can reduce the consumption of irreversible sodium ions in the sodium ion battery, thereby improving the first coulomb efficiency of the battery, improving the high and low temperature performance and cycle stability of the sodium ion battery, and reducing the internal resistance of the sodium ion battery.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, specifically to sodium-ion batteries and electrical devices. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage due to their high energy density and cycle performance. However, rising lithium salt prices have limited the development of lithium-ion batteries due to limited lithium resources. Sodium, an element in the same group as lithium, has very similar physical and chemical properties. Moreover, sodium is more abundant on Earth than lithium and has a lower cost, making sodium-ion batteries a better choice for large-scale energy storage. To date, research on sodium-ion battery technology has attracted widespread attention in both academic and industrial fields.

[0003] However, sodium-ion batteries suffer from drawbacks such as low energy density and poor cycle stability, which hinders their large-scale application. The electrolyte, as a regulator of electrochemical behavior and a stabilizer of the ion conductors between the interface and electrodes, significantly impacts the performance of sodium-ion batteries. Electrolytes used in sodium-ion batteries exhibit poor thermal stability and are prone to severe oxidative decomposition at high voltages, leading to a deterioration in capacity and cycle performance. Therefore, sodium-ion battery electrolyte technologies still require improvement. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a sodium-ion battery that can improve operating voltage or SEI film stability, and an electrical device containing the same.

[0005] In a first aspect of this application, a sodium-ion battery is provided. According to an embodiment of this application, the sodium-ion battery includes an electrolyte comprising a first additive, the first additive comprising a compound of formula 1:

[0006]

[0007] Among them, R1, R2 and R3 each independently include any one of H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, R4 substituted phenyl and R5 substituted benzyl;

[0008] R4 and R5 are each independently selected from any one of F, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl.

[0009] In the sodium-ion battery of this application embodiment, the addition of the fluorophosphate compound shown in Formula 1 to the electrolyte can reduce the irreversible consumption of sodium ions in the sodium-ion battery, thereby improving the initial coulombic efficiency of the sodium-ion battery, enhancing the high and low temperature performance and cycle stability of the sodium-ion battery, and reducing the internal resistance of the sodium-ion battery.

[0010] According to the embodiments of this application, R1, R2, and R3 are each independently selected from any one of F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, phenyl, and fluorophenyl.

[0011] According to embodiments of this application, R1, R2, and R3 are each independently selected from any one of F, methyl, ethyl, propyl, isopropyl, cyclohexyl, vinyl, ethynyl, butynyl, phenyl, fluorophenyl, 3,3,3-trifluoropropenyl, perfluoroethyl, p-methylbenzyl, and 4,4,4-trifluoro-2-butynyl.

[0012] According to embodiments of this application, the first additive comprises at least one of the following compounds:

[0013]

[0014]

[0015] Using the specific compounds mentioned above, the effect of suppressing the hydrolysis of the main salt in the electrolyte of sodium-ion batteries is better, which can form a more stable interface film and provide more and more stable channels for sodium ion insertion and extraction. This results in sodium-ion batteries having excellent high and low temperature performance and cycle stability, lower internal resistance and higher initial coulombic efficiency.

[0016] According to embodiments of this application, the first additive has a mass percentage content of 0.1% to 5% in the electrolyte. In some specific embodiments, the first additive has a mass percentage content of 0.3% to 2% in the electrolyte. Within the above content range, the first additive can effectively inhibit the hydrolysis of the main salt, construct a stable interface film, and provide sodium ion transport channels, while having virtually no negative impact on the electrolyte. This can effectively improve the high and low temperature performance and cycle stability of the sodium-ion battery, and significantly reduce the internal resistance of the sodium-ion battery.

[0017] According to embodiments of this application, the electrolyte further includes a sodium salt as the main salt and an organic solvent. In some embodiments, the sodium salt as the main salt includes at least one selected from sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium difluorooxalatoborate, sodium difluorodioxalatophosphate, sodium bis(fluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. In some specific embodiments, the sodium salt as the main salt may include at least one selected from sodium hexafluorophosphate and sodium bis(fluoromethanesulfonyl)imide. Therefore, better ion transport performance, suitable conductivity, stability, and compatibility with electrode materials can be provided, resulting in better electrochemical performance of the sodium-ion battery.

[0018] According to embodiments of this application, the sodium salt main salt comprises sodium hexafluorophosphate, and the mass percentage of sodium hexafluorophosphate in the electrolyte is 1% to 20%. Using sodium hexafluorophosphate with the above-mentioned content as the main salt results in superior ion transport performance, conductivity, stability, and compatibility with electrode materials.

[0019] According to embodiments of this application, the sodium salt main salt comprises sodium bis(fluorosulfonyl)imide, and the sodium bis(fluorosulfonyl)imide in the electrolyte has a mass percentage content of 1% to 12%. Using sodium bis(fluorosulfonyl)imide with the above-mentioned content as the main salt results in better ion transport performance, conductivity, stability, and compatibility with electrode materials.

[0020] According to embodiments of this application, the organic solvent includes at least one of cyclic compounds and linear compounds.

[0021] In some embodiments, the cyclic compound includes at least one of propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, and fluoroethylene carbonate; specifically, it may be at least one of propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

[0022] In some embodiments, the linear compound includes at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl propionate, ethyl propionate, propyl acetate, methyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2-difluoroethyl acetate.

[0023] The solvent described above has a better solvation effect, which is beneficial to optimizing the performance of sodium-ion batteries. It also has better sodium-ion transport performance, which in turn makes sodium-ion batteries have better electrochemical performance.

[0024] According to embodiments of this application, the organic solvent in the electrolyte has a mass percentage content of 10% to 90%.

[0025] According to embodiments of this application, the electrolyte may further include a second additive, which includes at least one of 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), sodium trifluoromethanesulfonate, vinylene carbonate (VC), ethylene ethylene carbonate (VEC), vinyl sulfate (DTD), fluoroethylene carbonate, tris(trimethylsilyl)phosphite, hexamethylene diisocyanate, and sodium saccharin. The aforementioned second additive can form a stable SEI film at the negative electrode, reducing electrolyte side reactions. Specifically, sodium trifluoromethanesulfonate and sodium saccharin have good electrochemical reactivity; they can not only improve the thermal stability of the electrolyte but also provide sodium ions to replenish some of the lost active sodium ions at the positive and negative electrodes. The introduction of VC can reduce the initial capacity loss of sodium-ion batteries and significantly improve the stability of the SEI film under high-temperature conditions. Hexamethylene diisocyanate can react with HF to produce polyurethane, avoiding the generation of fluorosilanes and imparting excellent elasticity to the interfacial film.

[0026] According to an embodiment of this application, the second additive has a mass percentage content of 0.1% to 3% in the electrolyte, specifically 0.3% to 1%. Within the above content range, the second additive can fully exert its function while having virtually no negative impact on the electrolyte, thereby further improving the high and low temperature performance and cycle stability of the sodium-ion battery.

[0027] According to embodiments of this application, the sodium-ion battery further includes: a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive and negative electrode. The positive electrode includes a positive active material, which comprises at least one of layered oxides, Prussian compounds, polyanionic compounds, and sodium metal oxides. In some specific embodiments, the positive active material includes NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Na3V2(PO4)3, Na 0.9 Mn 0.6 Fe 0.4 At least one of PO4, Na4Fe3(PO4)2(P2O7), and sodium ferrocyanide. Therefore, it can synergistically work with the first additive in the electrolyte to form a highly stable SEI film, resulting in excellent high and low temperature performance and cycle stability of the sodium-ion battery.

[0028] According to an embodiment of this application, the negative electrode sheet includes a negative electrode active material, which includes one or more of carbonaceous materials, silicon-carbon materials, alloy materials, and sodium-containing metal composite oxides.

[0029] In a second aspect, this application provides an electrical device. According to an embodiment of this application, the electrical device includes the sodium-ion battery described above. This electrical device possesses all the features and advantages of the sodium-ion battery described above, which will not be repeated here. Detailed Implementation

[0030] This application is based on the inventor's following discoveries and understandings:

[0031] Currently used sodium-ion battery electrolytes have poor thermal stability and are prone to severe oxidative decomposition at high voltages, leading to deterioration in battery capacity and cycle performance. Therefore, there is an urgent need to develop an electrolyte system that is stable under high voltage. The inventors discovered that the working mechanism of sodium-ion batteries is as follows: during charging and discharging, sodium ions work in two parts. One part involves insertion and extraction at the positive and negative electrodes, while the other part involves adsorption and separation at the negative electrode. Due to their larger size and greater insertion and extraction losses, sodium ions exhibit worse cycle reversibility and interface film stability compared to lithium-ion batteries. Therefore, sodium-ion batteries require higher ion transport capabilities. Based on these findings, this invention proposes adding fluorophosphate compounds as additives to the electrolyte of sodium-ion batteries. This electrolyte can effectively improve the operating voltage and SEI film stability, thereby enhancing the high and low temperature performance and cycle stability of sodium-ion batteries.

[0032] In view of this, in a first aspect of this application, a sodium-ion battery is provided. According to an embodiment of this application, the sodium-ion battery includes an electrolyte, the electrolyte including a first additive, the first additive including a compound of Formula 1:

[0033]

[0034] Among them, R1, R2 and R3 each independently include any one of H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkanes, R4-substituted phenyl and R5-substituted benzyl;

[0035] R4 and R5 are each independently selected from any one of F, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl.

[0036] In the sodium-ion battery of this application, by adding a first additive to the electrolyte, the fluorophosphate compound shown in Formula 1 can reduce the irreversible consumption of sodium ions in the sodium-ion battery, thereby improving the initial coulombic efficiency of the sodium-ion battery, enhancing the high and low temperature performance and cycle stability of the sodium-ion battery, and reducing the internal resistance of the sodium-ion battery.

[0037] Specifically, the fluorophosphate compounds shown in Formula 1 can decompose and combine with sodium ions to produce inorganic sodium salts such as sodium fluoride, sodium fluoride-containing phosphate, or sodium phosphate. On the one hand, this can inhibit the hydrolysis of the main sodium salt in the electrolyte and improve the stability of the electrolyte. On the other hand, the inorganic components such as sodium salts produced can participate in the construction of the positive / negative electrode interface film. For the positive electrode, the constructed positive electrode CEI film can stabilize the transition metal in the positive electrode material and inhibit its dissolution at the positive electrode. For the negative electrode, inorganic components such as sodium fluoride-containing phosphate and sodium phosphate, as well as organic components such as polysiloxane, give the interface film better rigidity and flexibility, avoid the corrosion and decomposition of the negative electrode by solvated sodium ions during the adsorption-separation process, and inhibit the deposition of transition metal ions at the negative electrode. At the same time, the inorganic sodium salt components can reduce the binding energy of sodium ions and provide channels for sodium ion insertion and extraction, which facilitates the stable progress of the sodium ion adsorption-separation-insertion (extraction) process and reduces the risk of sodium dendrites caused by the large size of sodium ions and large insertion and extraction losses.

[0038] The silicon-based structure enhances the reactivity of the decomposition reaction in the electrolyte, and the siloxane compounds produced by the reaction stabilize the interfacial film, thereby improving its mechanical toughness and surface smoothness.

[0039] Based on the combined effects of the above, the sodium-ion battery of this application has better low-temperature performance and cycle stability, lower internal resistance and higher initial coulombic efficiency.

[0040] It should be noted that the term "C1-C4 alkyl" used in this application refers to a saturated straight-chain or branched monovalent hydrocarbon group containing 1-4 carbon atoms. Examples of C1-C4 alkyl groups include, but are not limited to, methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), isobutyl (-CH2CH(CH3)2), sec-butyl (-CH(CH3)CH2CH3), tert-butyl (-C(CH3)3), etc.

[0041] The term "C1-C4 fluoroalkyl" refers to a C1-C4 alkyl group in which at least one hydrogen atom is replaced by a fluorine atom.

[0042] The term "C2-C4 alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group containing 2-4 carbon atoms, wherein there is at least one unsaturated site, i.e., a carbon-carbon sp2 double bond. Examples of C2-C4 alkenyl include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), 1-propenyl (-CH=CH-CH3), etc.

[0043] The term "C2-C4 fluoroalkenyl" refers to a C2-C4 alkenyl group in which at least one hydrogen atom is replaced by a fluorine atom.

[0044] The term "C2-C4 alkynyl" refers to a straight-chain or branched monovalent hydrocarbon group containing 2-4 carbon atoms, with at least one unsaturated site, i.e., a carbon-carbon sp triple bond. Examples of C2-C4 alkynyl groups include, but are not limited to, ethynyl (-C≡CH), propynyl (-CH2C≡CH), 1-propynyl (-C≡C-CH3), etc.

[0045] The term "C2-C4 fluoroalkynyl" refers to a C2-C4 alkynyl group in which at least one hydrogen atom is replaced by a fluorine atom.

[0046] The term "R4-substituted phenyl" means that one or more of the five hydrogen atoms on a phenyl group are replaced by R4, and the substitution positions include ortho, meta, para, etc.; "R5-substituted benzyl" means that one or more of the four hydrogen atoms on the benzene ring of a benzyl group are replaced by R5, and the substitution positions include ortho, meta, para, etc.

[0047] The description "R1, R2, R3 are independent of each other..." in this article means that R1, R2, and R3 are independent of each other and do not affect each other. They can be the same or different.

[0048] According to the embodiments of this application, R1, R2, and R3 are each independently selected from any one of F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C2-C4 fluoroalkynyl, C5-C7 cycloalkyl, phenyl, and fluorophenyl.

[0049] According to embodiments of this application, R1, R2, and R3 are each independently selected from F, methyl, ethyl, propyl, isopropyl, cyclohexyl, vinyl, ethynyl, butynyl, phenyl, fluorophenyl, 3,3,3-trifluoropropenyl, perfluoroethyl, p-methylbenzyl, and 4,4,4-trifluoro-2-butynyl.

[0050] According to embodiments of this application, the first additive comprises at least one of the following compounds:

[0051]

[0052]

[0053] Using the specific compounds mentioned above, the effect of suppressing the hydrolysis of the main salt in the electrolyte is better, which can form a more stable interface film and provide more and more stable channels for sodium ion insertion and extraction. This results in sodium-ion batteries having excellent high and low temperature performance and cycle stability, lower internal resistance and higher initial coulombic efficiency.

[0054] According to embodiments of this application, the first additive has a mass percentage content of 0.1% to 5% in the electrolyte. In some specific embodiments, the first additive has a mass percentage content of 0.3% to 2% in the electrolyte. Specifically, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%. Within the above content range, the first additive can effectively inhibit the hydrolysis of the main salt, construct a stable interface film, and provide sodium ion transport channels, while having virtually no negative impact on the sodium-ion battery. This effectively improves the high and low temperature performance and cycle stability of the sodium-ion battery, and significantly reduces its internal resistance.

[0055] According to embodiments of this application, the electrolyte further includes a sodium salt main salt and an organic solvent.

[0056] In some embodiments, the sodium salt main salt includes at least one selected from sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium difluorooxalatoborate, sodium difluorodioxalatophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. In some specific embodiments, the sodium salt main salt may include at least one selected from sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide. This provides superior ion transport performance, suitable conductivity, stability, and compatibility with electrode materials, resulting in better electrochemical performance of the sodium-ion battery.

[0057] According to embodiments of this application, the sodium salt main salt comprises sodium hexafluorophosphate, and the mass percentage of sodium hexafluorophosphate in the electrolyte is 1% to 20%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 7%, 18%, 19%, 20%, etc. Using sodium hexafluorophosphate with the above-mentioned content as the main salt results in superior ion transport performance, conductivity, stability, and compatibility with electrode materials.

[0058] According to embodiments of this application, the sodium salt main salt comprises sodium bis(fluorosulfonyl)imide, and the mass percentage of sodium bis(fluorosulfonyl)imide in the electrolyte is 1% to 12%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc. Using sodium bis(fluorosulfonyl)imide with the above-mentioned content as the main salt results in superior ion transport performance, conductivity, stability, and compatibility with electrode materials.

[0059] According to embodiments of this application, the organic solvent includes at least one of cyclic compounds and linear compounds.

[0060] In some embodiments, the cyclic compound includes at least one selected from propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, and fluoroethylene carbonate; specifically, it may be at least one selected from propylene carbonate, methyl ethyl carbonate, and diethyl carbonate. As an example, the cyclic compound comprises propylene carbonate: methyl ethyl carbonate: diethyl carbonate in a mass ratio of 3:6:1.

[0061] In some embodiments, the linear compound includes at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl propionate, ethyl propionate, propyl acetate, methyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2-difluoroethyl acetate.

[0062] The solvent described above has a better solvation effect, which is beneficial to optimizing battery performance. It also has better sodium ion transport performance, which in turn makes the sodium ion battery have better electrochemical performance.

[0063] According to embodiments of this application, the organic solvent in the electrolyte has a mass percentage content of 10% to 90%, specifically such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc.

[0064] According to embodiments of this application, the electrolyte may further include a second additive, which includes at least one of 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), sodium trifluoromethanesulfonate, vinylene carbonate (VC), ethylene ethylene carbonate (VEC), vinyl sulfate (DTD), fluoroethylene carbonate, tris(trimethylsilyl)phosphite, hexamethylene diisocyanate, and sodium saccharin. The aforementioned second additive can form a stable SEI film at the negative electrode, reducing electrolyte side reactions. Specifically, sodium trifluoromethanesulfonate and sodium saccharin have good electrochemical reactivity; they can not only improve the thermal stability of the electrolyte but also provide sodium ions to replenish some of the lost active sodium ions at the positive and negative electrodes. The introduction of VC can reduce the initial capacity loss of sodium-ion batteries and significantly improve the stability of the SEI film under high-temperature conditions. Hexamethylene diisocyanate can react with HF to produce polyurethane, avoiding the generation of fluorosilanes and imparting excellent elasticity to the interfacial film.

[0065] According to embodiments of this application, the second additive has a mass percentage content of 0.1% to 3% in the electrolyte, specifically 0.3% to 1%; more specifically, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc. Within the above content range, the second additive can fully exert its function while having virtually no negative impact on the electrolyte, thereby further improving the high and low temperature performance and cycle stability of the sodium-ion battery.

[0066] According to an embodiment of this application, the sodium-ion battery further includes: a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode includes a positive active material, wherein the positive active material includes at least one of layered oxides, Prussian compounds, and polyanionic compounds.

[0067] Specifically, layered oxide cathode materials have a layered structure, allowing sodium ions to insert and extract during charging and discharging. These materials typically have the chemical formula Na. x MO n , where M represents a transition metal (such as nickel, cobalt, manganese, etc.).

[0068] In some specific embodiments, the positive electrode active material includes NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Na3V2(PO4)3, Na 0.9 Mn 0.6 Fe 0.4At least one of PO4, Na4Fe3(PO4)2(P2O7), and sodium ferrocyanide. Therefore, it can synergistically work with the first additive in the electrolyte to form a highly stable SEI film, particularly suitable for the working mechanism of sodium-ion batteries where some sodium ions are inserted / extracted at the positive and negative electrodes, while others are adsorbed / separated at the negative electrode. This results in excellent high and low temperature performance and cycle stability for sodium-ion batteries.

[0069] In some embodiments, the positive electrode sheet may include a positive current collector, a positive active layer located on at least one side of the surface of the positive current collector, and the positive active material layer may include a positive active material, a binder, and a conductive agent.

[0070] As an example, the positive electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). According to embodiments of this application, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, and carbon fiber. The binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide, and polyvinyl alcohol.

[0071] According to embodiments of this application, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a binder, and a conductive agent, etc.

[0072] According to embodiments of this application, the negative electrode active material includes one or more of carbonaceous materials, silicon-carbon materials, alloy materials, and sodium-containing metal composite oxides. In some specific embodiments, the negative electrode active material can be hard carbon, graphite, etc. This facilitates synergistic action with the first additive to generate a more stable SEI film, thereby improving the low-temperature performance and cycle stability of the sodium-ion battery.

[0073] According to embodiments of this application, the conductive agent in the negative electrode active material layer can be at least one of acetylene black, conductive carbon black, carbon nanotubes, conductive graphite, graphene, and carbon fiber. The binder in the negative electrode active material layer can be styrene-butadiene rubber, etc. The negative electrode current collector can be a metal foil, for example, copper foil.

[0074] According to embodiments of this application, the separator can be a separator known in the art that can be used in batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0075] It is understandable that in this sodium-ion battery, the positive electrode, separator, and negative electrode can be made into an electrode assembly by stacking or winding, and the electrode assembly and electrolyte are contained in the outer packaging.

[0076] It is understandable that there are no particular restrictions on the specific type of battery; it can be a primary battery or a secondary battery. The shape of the battery can be cylindrical, square, or any other shape. According to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc.

[0077] In a second aspect, this application provides an electrical device. According to an embodiment of this application, the electrical device includes the sodium-ion battery described above. This electrical device possesses all the features and advantages of the sodium-ion battery described above, which will not be repeated here.

[0078] It is understood that there are no particular restrictions on the specific types of electrical devices, including but not limited to electric vehicles, power tools, electric bicycles, electric tricycles, electric toys, game consoles, wearable devices, mobile terminals (such as mobile phones, tablets, laptops, etc.), etc. In addition to the sodium-ion batteries mentioned above, the electrical device also has the necessary structures and components of conventional devices. Taking a car as an example, it may include the body, chassis, tires, windows, interior, etc., which are the essential structures and components of a conventional car. This application will not elaborate on them one by one.

[0079] The embodiments of this application are described in detail below.

[0080] The first additive used in the following examples can be purchased directly or prepared in-house. Specifically,

[0081] Compound 1 (CAS No.: 4419-25-9), Compound 2 (CAS No.: 2708941-25-5), Compound 3 (CAS No.: 13683-39-1), Compound 4 (CAS No.: 4414-27-1), Compound 5 (CAS No.: 4414-26-0), Compound 6 (CAS No.: 4480-02-8), Compound 7 (CAS No.: 2577172-95-1), Compound 8 (CAS No.: 13683-40-4), Compound 9 (CAS No.: 2577172-93-9) Compounds 10 (CAS No.: 2708941-27-7), 11 (CAS No.: 2287283-36-5), 12 (CAS No.: 6231-57-8), 13 (CAS No.: 1386-54-9), 14 (CAS No.: 2708941-26-6), 15 (CAS No.: 6231-58-9), 16 (CAS No.: 6231-59-0), and 17 (CAS No.: 2577172-94-0) can be purchased directly.

[0082] Compounds 18 to 22 were prepared according to the preparation method of Example 14 in patent CN114728992A, specifically, the dichlorophenylsilane in the reference document was replaced with the raw materials shown below.

[0083] Raw material: trivinylchlorosilane (1871-21-2);

[0084] The raw material is dimethylethynyl butylchlorosilane (2069196-19-4);

[0085] The raw material is dimethyl(trifluoropropylene)chlorosilane (89705-02-2);

[0086] The raw material is tris(pentafluoroethyl)chlorosilane (1620665-21-5);

[0087] The raw material is dimethyl(p-methylbenzyl)chlorosilane (1833-28-9).

[0088] Example 1:

[0089] The electrolyte provided in this embodiment comprises, by mass percentage: 18% sodium salt, 80.5% organic solvent, 1% fluorophosphate additive (compound 1), and 0.5% sodium trifluoromethanesulfonate as a second additive. The sodium salt comprises 12% sodium hexafluorophosphate (NaPF6) and 8% sodium difluorosulfonamide (NaFSI). The organic solvent is composed of propylene carbonate (PC), ethyl methyl carbonate (EC), and diethyl carbonate (DEC) in a mass ratio of PC:EMC:DEC = 3:6:1.

[0090] During preparation, the solvents were first mixed evenly in a nitrogen-filled glove box according to the mass ratio PC:EMC:DEC = 3:6:1. 77g of the mixed solution was taken, and 12g of NaPF6 and 8g of NaFSI were slowly added to the mixed solvent in sequence while stirring until completely dissolved. Then, 1g of compound 1 and 0.5g of sodium trifluoromethanesulfonate were added in sequence while stirring until completely dissolved. Finally, the mixed solution was added to bring the final weight to 100g to obtain the sodium-ion battery electrolyte.

[0091] NaNi, the positive electrode active material 1 / 3 Mn 1 / 3 Fe 1 / 3 O2 powder, conductive agent acetylene black, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are dispersed in solvent NMP at a mass ratio of 95:2:0.5:2 to obtain a positive electrode active material layer slurry. The positive electrode active material layer slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil. After drying, rolling, baking, slitting, and spot welding of electrode tabs, a positive electrode sheet is obtained with a total thickness of 134 μm.

[0092] The negative electrode active material hard carbon, conductive agent conductive carbon black super-p, binder SBR, and dispersant CMC-Na are dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 and stirred evenly to obtain a negative electrode active material layer slurry. The negative electrode active material layer slurry is uniformly coated on the surface of the negative electrode current collector aluminum foil. After drying, rolling, baking, slitting, and spot welding of electrode tabs, a negative electrode sheet is obtained with a total thickness of 150μm.

[0093] The prepared positive electrode, negative electrode, and 16μm three-layer polyethylene separator were stacked in sequence. The separator was placed between the positive and negative electrode. After winding, the wound body was flattened and placed in an aluminum-plastic film packaging bag. It was vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte. Then, the electrolyte was injected into the cell in a glove box. After encapsulation, formation, aging, and capacity testing, the sodium-ion battery was completed with a designed capacity of 950mAh.

[0094] Examples 2-40

[0095] Same as Example 1, with specific differences shown in Table 1.

[0096] Comparative Example 1

[0097] Same as Example 1, except that the electrolyte contains 80% organic solvent and does not contain the first and second additives.

[0098] Comparative Example 2

[0099] Similar to Example 1, except that the electrolyte contains 79.5% organic solvent and does not contain the first additive.

[0100] Performance testing:

[0101] The sodium-ion batteries in each embodiment and comparative example were subjected to the following performance tests, and the test results are shown in Table 1:

[0102] 1. Room temperature cycling performance test:

[0103] The battery was charged at 1C constant current to 4.0V at room temperature (25°C), and then charged at 4.0V constant voltage to the cutoff current of 0.05C. The battery was then discharged at 1C. This charge-discharge cycle was repeated for 500 cycles. The discharge capacity of the 500th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0104] 2. High-temperature cycling performance test:

[0105] The battery was charged at a constant current of 1C to 4.0V at a high temperature of 45℃, and then charged at a constant voltage of 4.0V to the cutoff current of 0.05C. The battery was then discharged at 1C. This charge-discharge cycle was repeated for 400 cycles. The discharge capacity of the 400th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0106] 3. Low-temperature discharge performance test:

[0107] The battery was charged at room temperature (25℃) with a constant current of 1C to 4.0V, and then charged at a constant voltage of 4.0V to a cutoff current of 0.05C. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C0. At room temperature (25℃), the battery was charged at a constant current of 1C to 4.0V, and then charged at a constant voltage of 4.0V to a cutoff current of 0.05C. The battery was then transferred to a low temperature of -20℃ and left to stand for 240 minutes. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C1. The discharge capacity retention rate at -20℃ = C1 / C0 × 100%.

[0108] 4. High-temperature storage performance test:

[0109] The battery was charged at room temperature (25℃) with a constant current of 1C to 4.0V, and then charged at a constant voltage of 4.0V to a cutoff current of 0.05C. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C2. At room temperature (25℃), the battery was charged at a constant current of 1C to 4.0V, and then charged at a constant voltage of 4.0V to a cutoff current of 0.05C. The thickness was measured and recorded as d0. The battery was then transferred to a high temperature of 60℃ and left to stand for 28 days. The thickness was measured and recorded as d1. The thickness expansion rate was calculated as (d1-d0) / d0 × 100%. The battery was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C3. The capacity retention rate at 60℃ was calculated as C3 / C2 × 100%.

[0110] 5. DC Impedance (DCR) Test:

[0111] The battery was placed in a 25°C environment and discharged at a constant current of 1C to the cutoff voltage of 2.0V. After resting for 5 minutes, it was charged at a constant current and constant voltage of 1C to the upper limit voltage of 4.0V, with a cutoff current of 0.05C. Then, it was discharged at a constant current of 1C for 30 minutes. The battery, adjusted to 50% SOC, was placed in a 25°C environment and allowed to rest for 5 minutes. Then, it was discharged at a constant current of 2C for 30 seconds. The discharge current during the 2C discharge was I. 2C Record the initial voltage V0 and the voltage V1 after 30 seconds of discharge. The formula for calculating the DC internal resistance of discharge at 50% SOC is as follows: DCR(Ω)=(V0-V1) / I 2C .

[0112] Table 1

[0113]

[0114]

[0115]

[0116] As can be seen from the test data in Table 1, by adding the first additive to the electrolyte of the sodium-ion battery, a more stable interface film is generated in the working environment of the sodium-ion battery, which better meets the stability requirements of large-size sodium ion insertion-extraction, thereby improving the low-temperature performance and cycle stability of the sodium-ion battery.

[0117] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0118] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0119] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A sodium-ion battery, characterized in that, It includes an electrolyte, a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, and the positive electrode includes a positive electrode active material; The electrolyte is composed of a sodium salt as the main salt, an organic solvent, and additives. The additives are composed of a first additive and a second additive. The first additive has a mass percentage of 0.1% to 5% in the electrolyte; the second additive has a mass percentage of 0.3% to 1% in the electrolyte; and the sodium salt has a mass percentage of 9% to 23% in the electrolyte. The first additive includes at least one of the following compounds: Compound 1, Compound 2, Compound 3, Compound 4, Compound 5, Compound 6, Compound 7, Compound 8, Compound 9, Compound 10, Compound 11, Compound 12, Compound 13, Compound 14, Compound 15, Compound 16, Compound 17, Compound 18, Compound 19, Compound 20, Compound 21, Compound 22; The second additive is selected from at least one of sodium trifluoromethanesulfonate and hexamethylene diisocyanate; The sodium salt main salt includes sodium hexafluorophosphate and sodium difluorosulfonyl imide; The positive electrode active material includes NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Na3V2 (PO4)3, Na 0.9 Mn 0.6 Fe 0.4 At least one of PO4, Na4Fe3(PO4)2(P2O7) and sodium ferrocyanide.

2. The sodium-ion battery according to claim 1, characterized in that, The first additive has a mass percentage content of 0.3% to 2% in the electrolyte.

3. The sodium-ion battery according to claim 1, characterized in that, The electrolyte satisfies at least one of the following conditions: (a) The organic solvent comprises at least one of cyclic compounds and linear compounds, wherein the cyclic compounds comprise at least one of propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, and fluoroethylene carbonate; and the linear compounds comprise at least one of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl propionate, ethyl propionate, propyl acetate, methyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2-difluoroethyl acetate. (b) The sodium hexafluorophosphate in the electrolyte has a mass percentage content of 1% to 20%; (c) The sodium difluorosulfonamide in the electrolyte has a mass percentage content of 1% to 12%; (d) The organic solvent in the electrolyte has a mass percentage content of 10% to 90%.

4. The sodium-ion battery according to claim 3, characterized in that, The organic solvent includes at least one of propylene carbonate, ethyl methyl carbonate, and diethyl carbonate.

5. The sodium-ion battery according to claim 1, characterized in that, The second additive has a mass percentage content of 0.5% in the electrolyte.

6. The sodium-ion battery according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode active material, which includes one or more of carbonaceous materials, silicon-carbon materials, alloy materials, and sodium-containing metal composite oxides.

7. An electrical device, characterized in that, The sodium-ion battery includes any one of claims 1 to 6.

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