Battery and electrical device

Abstract

A battery and an electrical device. The battery comprises a negative electrode plate and an electrolyte. The negative electrode plate comprises a negative electrode active material, the negative electrode active material comprising a hard carbon material. The electrolyte comprises a sulfate additive. The battery satisfies following formula 1: [equation 1], wherein the mass percentage of the sulfate additive in the electrolyte is Z%, the specific surface area of the hard carbon material is Em2 / g, the percentage of oxygen atoms in the hard carbon material to the total number of atoms of the hard carbon material is X%, and the percentage of nitrogen atoms in the hard carbon material to the total number of atoms of the hard carbon material is Y%.

Description

A battery and an electrical device

[0001] This application claims priority to Chinese Patent Application No. 202510324055.6, filed on March 17, 2025, entitled “A Battery and an Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] In the development of secondary batteries, electrolyte optimization is one of the key factors in improving battery performance. Additives have attracted widespread attention because they can improve the formation of the solid electrolyte interphase (SEI) film.

[0004] However, the application of additives in battery electrolytes in existing technologies still has some shortcomings. For example, the dosage of additives depends on experience, which lacks theoretical guidance and leads to poor additive compatibility, resulting in poor initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance of secondary batteries. Summary of the Invention

[0005] The main objective of this application is to provide a battery with superior initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0006] This application also provides an electrical device including the aforementioned battery, therefore, the battery performance of the electrical device is superior.

[0007] In a first aspect, this application provides a battery comprising a negative electrode sheet and an electrolyte, wherein the negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises a hard carbon material, and the electrolyte comprises a sulfate ester additive, and the battery satisfies the following formula 1:

[0008] k ranges from -0.5 to 0.5;

[0009] The sulfate ester additive accounts for Z% of the mass percentage of the electrolyte; the specific surface area of ​​the hard carbon material is Em. 2 / g; the percentage of oxygen atoms in the hard carbon material relative to the total number of atoms in the hard carbon material is X%; the percentage of nitrogen atoms in the hard carbon material relative to the total number of atoms in the hard carbon material is Y%.

[0010] In the battery described above, the specific surface area of ​​the hard carbon material is 3m². 2 / g~100m 2 / g.

[0011] In the battery described above, the percentage of oxygen atoms in the hard carbon material is 1.0% to 15.0% of the total number of atoms in the hard carbon material.

[0012] In the battery described above, the nitrogen atoms in the hard carbon material account for 0.1% to 0.5% of the total number of atoms in the hard carbon material.

[0013] In the battery described above, the sulfate ester additive accounts for 0.01% to 6.8% of the electrolyte by mass.

[0014] For the battery as described above, E satisfies 80 < E ≤ 100.

[0015] In the battery described above, the electrolyte further includes a stabilizer;

[0016] The stabilizer includes at least one of monofluorophosphate, difluorophosphate, pentafluoroethyl trifluoroborate, tetraphenylborate, difluorooxalate borate, dioxalate borate, and tetrafluoroborate.

[0017] In the battery described above, the stabilizer accounts for 0.2% to 0.8% of the mass percentage of the electrolyte.

[0018] In the battery described above, the sulfate ester additive includes at least one of vinyl sulfate (DTD), propylene sulfate (PES), dimethyl sulfate (DMS), diethyl sulfate (DES), dipropyl sulfate (DPS), dibutyl sulfate (DBS), pentaerythritol bicyclic sulfate (TDT), bicyclic [2.2.1]heptane-5-sulfate, dicyclopentadienyl sulfate, and tricyclic decyl sulfate.

[0019] The battery described above includes a sodium-ion battery.

[0020] Secondly, this application provides an electrical device including the battery described above.

[0021] The battery provided in this application satisfies Formula 1, that is, by introducing sulfate ester additives into the electrolyte of the battery and combining them with the characteristics of hard carbon materials, this application provides an optimized battery design that can significantly improve the overall performance of the battery, namely, improve the battery's initial coulombic efficiency, cycle stability, impedance, rate performance and storage performance. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] In the development of sodium-ion batteries, electrolyte optimization is one of the key factors in improving battery performance. Sulfate-based additives have attracted widespread attention due to their ability to improve the formation of the solid electrolyte interphase (SEI) film. The quality of the SEI film directly affects the overall performance of the battery. However, there are still some shortcomings in the current technology regarding the application of sulfate-based additives in sodium-ion battery electrolytes.

[0024] For example, the determination of additive dosage lacks theoretical guidance. Existing research typically relies on empirical experiments to determine the dosage of sulfate ester additives. This often overlooks the influence of material properties on additive consumption, leading to poor additive compatibility.

[0025] The inventors of this application have discovered that while sulfate ester additives can improve the quality of the SEI film, the amount of additive consumed may increase significantly in hard carbon materials with high specific surface areas. Furthermore, the functional groups on the surface of hard carbon materials also affect the reaction pathway and efficiency of the additives. Ignoring these factors may lead to insufficient or excessive additive usage, thereby affecting the overall performance of the battery. Therefore, establishing a theoretical guidance method that combines the characteristics of the negative electrode active material to optimize the amount of additives can improve the overall performance of the battery.

[0026] Based on this, in a first aspect, this application provides a battery, including a negative electrode sheet and an electrolyte, wherein the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a hard carbon material, and the electrolyte includes a sulfate ester additive, and the battery satisfies the following formula 1:

[0027] k ranges from -0.5 to 0.5;

[0028] Among them, sulfate ester additives account for Z% of the electrolyte by mass; the specific surface area of ​​hard carbon material is Em. 2 / g; The percentage of oxygen atoms in the total number of atoms in hard carbon materials is X%; The percentage of nitrogen atoms in the total number of atoms in hard carbon materials is Y%.

[0029] This application provides an optimized battery design by introducing sulfate ester additives into the battery electrolyte and combining them with the characteristics of hard carbon materials. This design significantly improves the overall battery performance, specifically enhancing initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance. The reason is that sulfate ester additives promote the formation of a stable and uniform solid electrolyte interphase (SEI) film in the electrolyte. This film effectively reduces side reactions between the electrolyte and the negative electrode active material, minimizing irreversible capacity loss during the first charge-discharge cycle, thereby improving the initial coulombic efficiency. Furthermore, the stable SEI film is not only effective during the first charge-discharge cycle but also maintains its integrity in subsequent cycles. This stability protects the negative electrode active material from structural degradation and capacity decay, significantly improving the battery's cycle life. Additionally, by optimizing the amount of sulfate ester additives and the surface properties of the hard carbon material, a highly conductive SEI film can be formed. This film reduces interfacial impedance and improves ion transport efficiency. Simultaneously, the lower interfacial impedance and stable SEI film contribute to improved battery performance at high rates. Rapid ion transport and a stable electrode interface enable the battery to maintain high capacity output at high discharge rates, thus improving its rate performance. Furthermore, sulfate-based additives and optimized hard carbon material properties work together to reduce electrolyte decomposition and electrode material degradation. This stability is particularly important during long-term storage, helping to maintain the battery's capacity and performance.

[0030] Therefore, the battery provided in this application, by rationally designing the amount of sulfate ester additives and the surface characteristics of hard carbon materials, can optimize the battery performance in many aspects, thereby improving the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0031] The specific surface area of ​​the hard carbon material in this application can be obtained by testing using the BET method.

[0032] In this application, the percentage of oxygen atoms in the total number of atoms in the hard carbon material can be obtained through XPS testing. Specifically, XPS testing is performed on the hard carbon material, and then the peaks of the XPS total spectrum are obtained using CasaXPS software.

[0033] XPS typically measures the atoms on the surface of hard carbon materials, meaning no etching is required. X% represents the percentage of oxygen atoms on the surface of the hard carbon material relative to the total number of atoms on the surface.

[0034] Similarly, the percentage of nitrogen atoms in the total number of atoms in hard carbon materials can also be obtained through XPS testing. Specifically, this is achieved by performing XPS testing on the hard carbon material and then using CasaXPS software to perform peak fitting on the XPS total spectrum.

[0035] XPS typically measures the atoms on the surface of hard carbon materials, which does not require etching. Y% represents the percentage of nitrogen atoms on the surface of the hard carbon material relative to the total number of atoms on the surface.

[0036] The hard carbon material in this application can be obtained using conventional methods in the art, such as commercial purchase or self-production using conventional methods. Parameters such as specific surface area, oxygen atom content, and nitrogen atom content of the hard carbon material can be controlled using conventional methods. For example, the specific surface area can be controlled by the following methods: 1) Carbonization process optimization: mainly by controlling the carbonization temperature. Increasing the carbonization temperature can reduce defects and porosity, thereby reducing the specific surface area. A slow heating rate helps to form a more ordered carbon layer structure, reducing defects and micropores, and effectively controlling the specific surface area. 2) Precursor treatment and selection: By cross-linking reactions or pre-oxidation treatment of precursors (such as epoxy resin and asphalt), the graphitization tendency during the carbonization process can be suppressed, and the pore distribution and specific surface area can be controlled. Pre-carbonizing biomass such as wood (e.g., 24-hour pre-carbonization) can reduce disordered structures, thus lowering the specific surface area of ​​the product. 3) Surface coating: Covering the active sites on the hard carbon surface suppresses side reactions between the electrolyte and high specific surface area materials, physically reducing the exposed specific surface area. 4) Micropore control: Activation methods such as alkali treatment can selectively remove some micropores, thereby reducing the specific surface area.

[0037] The oxygen atom content can be controlled by the following methods: 1) Chemical reduction to reduce oxygen atoms on the hard carbon surface: hydrogen plasma treatment, using H2 plasma to reduce oxygen-containing groups (such as carboxyl groups) on the surface. 2) Chemical oxidation to increase oxygen atoms on the hard carbon surface: selectively introducing oxygen atoms through oxidation with ozone, potassium permanganate, or nitric acid.

[0038] Nitrogen atom content can be controlled through the following methods: 1) Introduction via precursors: using nitrogen-rich organic matter (such as thiourea, biomass shrimp shells, polyacrylonitrile, etc.) as a carbon source, which decomposes during high-temperature carbonization, allowing nitrogen atoms to embed into the carbon framework. 2) Introduction of nitrogen atoms via chemical vapor deposition: introducing a nitrogen-containing atmosphere during carbonization.

[0039] In some embodiments of this application, the specific surface area of ​​the hard carbon material is 3m². 2 / g~100m 2 / g, for example, can be 3m 2 / g, 10m 2 / g、20m 2 / g、30m 2 / g、40m 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g、90m2 / g, 100m 2 / g or a range consisting of any two of them.

[0040] The hard carbon material in this application has a specific surface area within the aforementioned range, providing more active sites, which is beneficial for ion insertion and extraction, thereby increasing battery capacity. Furthermore, this specific surface area facilitates the formation of a stable solid electrolyte interphase (SEI) film, effectively reducing side reactions between the electrolyte and the negative electrode active material, and improving the battery's initial coulombic efficiency and cycle stability. In addition, this specific surface area provides more channels and pathways, promoting rapid ion transport and efficient electron conduction, which can improve the battery's rate performance. Simultaneously, the hard carbon material with this specific surface area can maintain structural stability, avoiding material pulverization or structural collapse due to volume changes during charge and discharge, thus helping to extend the battery's cycle life.

[0041] In some embodiments of this application, the percentage of oxygen atoms in the hard carbon material to the total number of atoms in the hard carbon material is 1.0% to 15.0%, for example, it can be a range of 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, 15.0%, or any combination thereof.

[0042] In this application, the percentage of oxygen atoms in the hard carbon material is within a suitable range, meaning the content of oxygen-containing functional groups in the hard carbon material is appropriate. These oxygen-containing functional groups, such as hydroxyl, carboxyl, and carbonyl groups, can promote the formation of a stable solid electrolyte interphase (SEI) membrane. The SEI membrane effectively reduces side reactions between the electrolyte and the negative electrode active material, improving the initial coulombic efficiency. Furthermore, these oxygen-containing functional groups can react with certain components in the electrolyte to form a chemically stable interface. This interface stability helps improve the battery's cycle life and reduce capacity decay. Additionally, oxygen-containing functional groups can increase the polarity of the hard carbon material, thereby improving its wettability with the electrolyte. This improved wettability helps the electrolyte penetrate more uniformly into the electrode material, improving ion transport efficiency. Simultaneously, oxygen-containing functional groups can provide additional active sites for ion insertion and extraction, thereby improving the battery's rate performance and capacity. Moreover, an appropriate amount of oxygen-containing functional groups can regulate the electrochemical reactivity of the hard carbon material and optimize its interaction with the electrolyte. This adjustment helps reduce interface impedance and improve the overall performance of the battery.

[0043] In some embodiments of this application, the percentage of nitrogen atoms in the hard carbon material to the total number of atoms in the hard carbon material is 0.1% to 0.5%, for example, it can be a range of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any two of these.

[0044] In this application, the percentage of nitrogen atoms in the hard carbon material is within a suitable range. Nitrogen doping can introduce additional electron donors, enhance the conductivity of the hard carbon material, and help improve the rate performance of the battery, enabling it to maintain a high capacity output during high-rate discharge. Furthermore, nitrogen atoms can alter the electronic structure of the hard carbon material, increasing the number of active sites and helping to improve ion insertion and extraction efficiency, thereby improving battery capacity and cycle stability. In addition, nitrogen-containing functional groups can react with components in the electrolyte, promoting the formation of a stable and uniform solid electrolyte interphase (SEI) film, effectively reducing side reactions and improving initial coulombic efficiency and cycle life. Simultaneously, the introduction of nitrogen atoms can modulate the surface chemistry of the hard carbon material, increasing its compatibility with the electrolyte. This compatibility helps reduce interfacial impedance and improve ion transport efficiency. Moreover, appropriate nitrogen doping can enhance the structural stability of the hard carbon material, reducing volume changes during charge-discharge cycles, thereby improving battery cycle life. The presence of nitrogen-containing functional groups can also optimize the interfacial characteristics between the electrode and the electrolyte, reducing interfacial impedance and improving overall electrochemical performance.

[0045] In some embodiments of this application, the sulfate ester additive accounts for 0.01% to 6.8% of the electrolyte by mass, for example, it can be a range of 0.01%, 1%, 2%, 3%, 4%, 5%, 6%, 6.8% or any two of these.

[0046] In this application, the sulfate ester additives account for a percentage of the electrolyte by mass within the above-mentioned range, which can further promote the formation of a uniform and stable solid electrolyte interphase (SEI) film on the negative electrode surface. This can effectively reduce the side reactions between the electrolyte and the negative electrode active material, and improve the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0047] In some embodiments of this application, E satisfies 80 < E ≤ 100, for example, it can be a range consisting of 81, 83, 85, 87, 90, 92, 95, 97, 100 or any two of them.

[0048] In this application, E satisfies 80 < E ≤ 100, meaning the specific surface area of ​​the hard carbon material is greater than 80 m². 2 / g, less than or equal to 100m 2A higher specific surface area ( / g) provides more active sites, which is beneficial for ion storage capacity and can increase battery capacity, enabling it to store and release more energy during charge and discharge. Furthermore, a larger specific surface area helps shorten the diffusion path of ions within the material, promoting rapid ion transport and improving the battery's rate performance, allowing for rapid charge and discharge at high rates. Additionally, a larger surface area provides more interfacial regions, facilitating the formation of a uniform and stable solid electrolyte interphase (SEI) film, thereby reducing side reactions between the electrolyte and the negative electrode active material, improving initial coulombic efficiency and cycle stability. Simultaneously, a higher specific surface area increases the reactivity of the negative electrode active material, enabling it to interact more effectively with the electrolyte and contributing to the optimization of the battery's electrochemical performance.

[0049] In some embodiments of this application, the electrolyte further includes a stabilizer; the stabilizer includes at least one selected from monofluorophosphate, difluorophosphate, pentafluoroethyl trifluoroborate, tetraphenylborate, difluorooxalate borate, dioxalate borate, and tetrafluoroborate.

[0050] The electrolyte of this application also includes stabilizers, the types of which include those mentioned above. In particular, when the negative electrode uses hard carbon material with a high specific surface area, sulfate ester additives can form a synergistic stable system with the stabilizers, significantly improving the stability of the SEI film, preventing the occurrence of side reactions, thereby improving the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0051] In some embodiments, the stabilizer accounts for 0.2% to 0.8% of the electrolyte by mass, for example, it can be a range of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any combination thereof.

[0052] In this application, the stabilizer accounts for 0.2% to 0.8% of the electrolyte by mass, which can further play a synergistic stabilizing role, improve the stability of the SEI film, prevent the occurrence of side reactions, and thus improve the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0053] In some embodiments of this application, the sulfate ester additives include at least one of vinyl sulfate (DTD), propylene sulfate (PES), dimethyl sulfate (DMS), diethyl sulfate (DES), dipropyl sulfate (DPS), dibutyl sulfate (DBS), pentaerythritol bicyclic sulfate (TDT), bicyclic [2.2.1]heptane-5-sulfate, dicyclopentadienyl sulfate, and tricyclic decyl sulfate.

[0054] The sulfate ester additives used in this application fall within the aforementioned range, which can further promote the formation of a stable and uniform solid electrolyte interphase (SEI) film on the negative electrode surface, thereby further improving the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0055] In some embodiments of this application, the battery includes a sodium-ion battery, which has advantages corresponding to the batteries described above, and will not be elaborated further.

[0056] The battery in this application includes a sodium-ion battery, which includes a positive electrode, a separator, a negative electrode, and an electrolyte. In addition to sulfate ester additives, the electrolyte also includes sodium electrolyte salts, solvents, and other additives.

[0057] The electrolyte sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium methanesulfonate, and sodium perchlorate, and the concentration of the sodium salt can be from 0.1 mol / L to 3 mol / L.

[0058] Solvents include ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethyl butyrate, butyl acetate, methyl propionate, propyl butyrate, trimethyl phosphate, triethyl phosphate, tetrahydrofuran, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and ethyl methanesulfonate. At least one of the following: γ-butyrolactone, sulfolane, dimethyl sulfone, dimethyl sulfoxide, ethyl methyl sulfone, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl (2,2,2-trifluoroethyl) carbonate, methyl trifluoroacetate, acetonitrile, and 1,3-dioxolane, may be used in an amount ranging from 85 wt% to 99.5 wt%.

[0059] Other additives include at least one of the following: vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, tris(trimethylsilane) phosphate, 1,3-propane sulpholactone, methylene disulfonate, 1,3,6-hexanetrionitrile, tris(pentafluorophenyl)borane, 3-hexylthiophene, hexafluorocyclotriphosphazene, and tris(hexafluoroisopropyl) phosphate, in a content of 0 wt% to 8 wt%.

[0060] In the battery manufacturing process provided in this application, the amount of each substance added in the electrolyte, the specific surface area of ​​the hard carbon material, the proportion of oxygen atoms, and the proportion of nitrogen atoms may deviate from the content of each substance in the electrolyte, the specific surface area of ​​the hard carbon material, the proportion of oxygen atoms, and the proportion of nitrogen atoms obtained from the electrolyte and hard carbon material obtained after disassembling the battery. However, these deviations are within the error range. Therefore, the amount of each substance added in the electrolyte, the specific surface area of ​​the hard carbon material, the proportion of oxygen atoms, and the proportion of nitrogen atoms in the battery manufacturing process are basically consistent with the content of each substance in the electrolyte, the specific surface area of ​​the hard carbon material, the proportion of oxygen atoms, and the proportion of nitrogen atoms in the battery.

[0061] The battery in this application can be a single cell, a battery pack, a battery stack, or a cylindrical cell formed by connecting single cells. These cells can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a hybrid connection that includes both of these connection methods. No particular limitation is made in this regard.

[0062] Secondly, this application provides an electrical device including the battery described above, which has advantages corresponding to the battery described above, and will not be elaborated further.

[0063] The electrical equipment used in this application can be conventional electrical equipment in the field, such as power equipment (e.g., electric vehicles), electronic equipment (e.g., computers, mobile phones, digital cameras, printers, fax machines, etc.), wearable devices (e.g., watches, wristbands, VR glasses, etc.), and household appliances (e.g., air conditioners, refrigerators, washing machines, microwave ovens, etc.), etc., without any particular limitation.

[0064] The technical solution of this application will be further described below with reference to specific embodiments.

[0065] The following examples and comparative examples can all change the specific surface area of ​​hard carbon materials by lowering or raising the carbonization temperature; change the oxygen atom content of hard carbon materials by introducing oxygen elements through nitric acid oxidation or by using H2 plasma to reduce oxygen-containing groups on the surface; and change the nitrogen atom content of hard carbon materials by lowering the nitrogen-containing atmosphere or using nitrogen-rich organic matter as a carbon source during the carbonization process.

[0066] Example 1

[0067] The battery preparation method of this embodiment includes the following steps:

[0068] 1) Preparation of electrolyte

[0069] In a nitrogen-filled clean glove box with water and oxygen content ≤0.1ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 3:7. Sodium hexafluorophosphate (NaPF6) was added to the prepared solvent and thoroughly mixed and dissolved to prepare a basic electrolyte containing 1 mol / L sodium hexafluorophosphate (NaPF6). Ethyl acetate sulfate (DTD) was added to the basic electrolyte to obtain the final electrolyte. The DTD constituted 2% of the electrolyte by mass, i.e., Z = 2.

[0070] 2) Fabrication of sodium-ion batteries

[0071] The positive electrode active material sodium iron phosphate pyrophosphate (Na4Fe3(PO4)2P2O7), conductive carbon black, and binder polyvinylidene fluoride (PVDF) were added and dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2 and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of carbon-coated aluminum foil, and after drying, rolling, and cutting, a positive electrode sheet was obtained.

[0072] Hard carbon (anode active material), conductive carbon black, sodium carboxymethyl cellulose (CMC) binder, and styrene-butadiene rubber (SBR) were added to and dispersed in distilled water at a mass ratio of 96:1:1.5:1.5, and thoroughly mixed to obtain the anode slurry; wherein, the specific surface area of ​​the hard carbon material is 50 m². 2 / g, i.e., E=50, the percentage of oxygen atoms in the hard carbon material is 8% of the total number of atoms in the hard carbon material, i.e., X=8, and the percentage of nitrogen atoms in the hard carbon material is 3% of the total number of atoms in the hard carbon material, i.e., Y=3. The negative electrode slurry is coated on both sides of double-sided bright aluminum foil, and after drying, rolling and cutting, the negative electrode sheet is obtained.

[0073] The positive electrode, polypropylene porous separator, and negative electrode are stacked to prepare the electrode assembly. The tabs are then welded onto the positive and negative electrodes using an ultrasonic spot welder. The electrode assembly is then placed in an aluminum foil bag and vacuum dried at 80°C for 48 hours to obtain a dried battery cell.

[0074] In a nitrogen-filled glove box with water and oxygen content ≤0.1ppm, the prepared electrolyte is injected into the thoroughly dried battery cell. After the electrolyte injection is completed, the cell is sealed and left to stand, undergoes formation, aging, resealing, and capacity testing to obtain a sodium-ion battery.

[0075] Example 2

[0076] The preparation method of the battery in Example 2 is basically the same as that in Example 1, except that the mass percentage of DTD in the electrolyte is 1.6%, i.e., Z = 1.6.

[0077] Example 3

[0078] The preparation method of the battery in Example 3 is basically the same as that in Example 1, except that the mass percentage of DTD in the electrolyte is 2.6%, i.e., Z = 2.6.

[0079] Example 4

[0080] The preparation method of the battery in Example 4 is basically the same as that in Example 1, except that the solvent for the electrolyte is ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a volume ratio of 3:5:2. Dipropyl sulfate (DPS) and dibutyl sulfate (DBS) are added to the basic electrolyte to obtain the electrolyte. DPS accounts for 3.1% of the electrolyte by mass, and DBS accounts for 3.2% of the electrolyte by mass, i.e., Z = 6.3. The specific surface area of ​​the hard carbon material is 100 m². 2 / g, that is, E=100, the percentage of oxygen atoms in the hard carbon material is 15% of the total number of atoms in the hard carbon material, that is, X=15, and the percentage of nitrogen atoms in the hard carbon material is 0.1% of the total number of atoms in the hard carbon material, that is, Y=0.1.

[0081] Example 5

[0082] The preparation methods of the batteries in Example 5 and Example 4 are basically the same, except that the mass percentage of DPS in the electrolyte is 3.1%, and the mass percentage of DBS in the electrolyte is 3.2%, i.e., Z = 6.3. Sodium difluorophosphate (NaPO2F2) is also added as a synergistic stabilizer, wherein NaPO2F2 accounts for 0.5% of the mass percentage of the electrolyte.

[0083] Example 6

[0084] The preparation method of the battery in Example 6 is basically the same as that in Example 1, except that ethylene carbonate (EC) and propylene carbonate (PC) are mixed in a nitrogen-filled clean glove box with water and oxygen content ≤0.1ppm at a volume ratio of 5:5. Sodium perchlorate (NaClO4) is added to the prepared solvent and thoroughly mixed and dissolved to prepare a basic electrolyte containing 0.8mol / L sodium perchlorate (NaClO4). Fluorinated ethylene carbonate (FEC), ethylene sulfate (DTD), and propylene sulfate (PES) are added to the basic electrolyte to obtain the electrolyte. The mass percentages of FEC, DTD, and PES in the electrolyte are 5%, 0.4%, and 0.3%, respectively, i.e., Z = 0.7. The specific surface area of ​​the hard carbon material is 10m². 2 / g, that is, E=10, the percentage of oxygen atoms in hard carbon materials is 3%, that is, X=3, the percentage of nitrogen atoms in hard carbon materials is 0.2%, that is, Y=0.2.

[0085] Example 7

[0086] The preparation method of the battery in Example 7 is basically the same as that in Example 1, except that the specific surface area of ​​the hard carbon material is 3m². 2 / g, i.e., E=3, the percentage of oxygen atoms in the hard carbon material is 2% of the total number of atoms, i.e., X=2, and the percentage of nitrogen atoms in the hard carbon material is 0.2% of the total number of atoms, i.e., Y=0.2. Ethylene sulfate (DMS) is added to the basic electrolyte to obtain the electrolyte. The DMS accounts for 0.3% of the electrolyte by mass, i.e., Z=0.3.

[0087] Example 8

[0088] The preparation method of the battery in Example 8 is basically the same as that in Example 1, except that the specific surface area of ​​the hard carbon material is 22 m². 2 / g, i.e., E=22, the percentage of oxygen atoms in the hard carbon material is 1%, i.e., X=1, and the percentage of surface nitrogen atoms in the hard carbon material is 0.2%, i.e., Y=0.2. Ethyl acetate (DES) is added to the basic electrolyte to obtain the electrolyte. The mass percentage of DES in the electrolyte is 0.6%, i.e., Z=0.6.

[0089] Example 9

[0090] The preparation method of the battery in Example 9 is basically the same as that in Example 1, except that the specific surface area of ​​the hard carbon material is 55 m². 2 / g, i.e., E=55, the percentage of oxygen atoms in the hard carbon material is 10%, i.e., X=10, and the percentage of nitrogen atoms in the hard carbon material is 0.5%, i.e., Y=0.5. Ethylene sulfate (DPS) is added to the basic electrolyte to obtain the electrolyte. DPS accounts for 2% of the mass of the electrolyte, i.e., Z=2.

[0091] Example 10

[0092] The preparation method of the battery in Example 10 is basically the same as that in Example 1, except that the specific surface area of ​​the hard carbon material is 3m². 2 / g, i.e., E=3, the percentage of oxygen atoms in the hard carbon material is 2% of the total number of atoms, i.e., X=2, and the percentage of nitrogen atoms in the hard carbon material is 0.2% of the total number of atoms, i.e., Y=0.2. Vinyl sulfate (DBS) is added to the basic electrolyte to obtain the electrolyte. DBS accounts for 0.01% of the electrolyte by mass, i.e., Z=0.01.

[0093] Comparative Example 1

[0094] The preparation methods of the batteries in Comparative Example 1 and Example 1 are basically the same, except that the mass percentage of DTD in the electrolyte is 1%, i.e., Z = 1.

[0095] Comparative Example 2

[0096] The preparation method of the battery in Comparative Example 2 is basically the same as that in Example 1, except that the mass percentage of DTD in the electrolyte is 4%, i.e., Z = 4.

[0097] Comparative Example 3

[0098] The preparation method of the battery in Comparative Example 3 is basically the same as that in Example 1, except that no electrolyte additive is added, i.e., Z=0.

[0099] Comparative Example 4

[0100] The preparation methods of the batteries in Comparative Example 4 and Example 5 are basically the same, except that the mass percentage of DPS in the electrolyte is 2% and the mass percentage of DBS in the electrolyte is 2%, that is, Z=4.

[0101] Comparative Example 5

[0102] The preparation methods of the batteries in Comparative Example 5 and Example 6 are basically the same, except that the mass percentage of DTD in the electrolyte is 1% and the mass percentage of PES in the electrolyte is 1%, i.e., Z = 2.

[0103] Comparative Example 6

[0104] The preparation methods of the batteries in Comparative Example 6 and Example 7 are basically the same, except that the mass percentage of DMS in the electrolyte is 1%, i.e., Z = 1.

[0105] Comparative Example 7

[0106] The preparation methods of the batteries in Comparative Example 7 and Example 8 are basically the same, except that the mass percentage of DES in the electrolyte is 2%, i.e., Z = 2.

[0107] Comparative Example 8

[0108] The preparation methods of the batteries in Comparative Example 8 and Example 9 are basically the same, except that the mass percentage of DPS in the electrolyte is 1%, i.e., Z = 1.

[0109] Comparative Example 9

[0110] The preparation methods of the batteries in Comparative Example 9 and Example 10 are basically the same, except that the mass percentage of DBS in the electrolyte is 0.005%, i.e., Z = 0.005.

[0111] Experimental example:

[0112] 1. Specific Surface Area: A portion of the hard carbon material was ultrasonically cleaned with anhydrous ethanol or isopropanol for 5-10 minutes to remove surface contaminants. It was then dried in a vacuum drying oven at 60℃ for 12 hours. The specific surface area of ​​the hard carbon material was tested using the BET static method. First, the hard carbon material was placed in a sample tube of a specialized adsorbent and pretreated at high temperature (200℃ with nitrogen blowing for 2 hours) to remove surface impurities and moisture. Subsequently, an inert gas (usually nitrogen or other adsorbent) was brought into contact with the hard carbon material under a series of known relative pressures until adsorption equilibrium was reached. The instrument measured the adsorption amount at different relative pressures, and the specific surface area was calculated based on these data using BET theory. The results are shown in Table 1.

[0113] 2. XPS characterization method for quantitative analysis of the atomic content of hard carbon surface: Grind some hard carbon to a particle size ≤ 5 μm, take 100 mg of sample and dry it in an argon atmosphere for 12 h, then disperse the dried sample evenly on conductive tape to avoid surface contamination.

[0114] XPS Test Conditions

[0115] Instrument: Al Kα ray source (hv=1486.6eV), power 150W.

[0116] Vacuum degree: ≤5×10 -9 mbar.

[0117] Scan range: wide scan (0-1200eV), narrow scan (C1s, O1s, N1s).

[0118] Energy resolution: ≤0.48eV.

[0119] Data analysis methods

[0120] Peak fitting was performed on the XPS overall spectrum to obtain the atomic percentage of each element on the surface of the hard carbon material. For example, CasaXPS software was used for peak fitting. The results are shown in Table 1.

[0121] 3. Percentage of sulfate ester additives in electrolyte by mass: mass of sulfate ester additives / total mass of electrolyte × 100%.

[0122] 4. Initial Coulombic Efficiency: At 25℃, the battery is discharged at a constant current of 0.05C to 0.01V, then discharged at a constant voltage with a cutoff current of 0.02C. The discharge capacity at this point is recorded as the initial discharge specific capacity. Subsequently, it is charged at a constant current of 0.05C to 2.0V, and the charging capacity at this point is recorded as the initial charging specific capacity. The initial coulombic efficiency is calculated by dividing the initial discharge specific capacity by the initial charging specific capacity. The results are shown in Table 1.

[0123] 5. Storage Performance Test: The batteries of the examples and comparative examples were discharged to 2V using a 0.2C constant current discharge mode, and then charged to 3.4V using a 0.2C constant current charging mode, which was recorded as the initial capacity C1. The batteries were stored in a constant temperature chamber at 60℃ for 84 days. They were then discharged to 2V using a 0.2C constant current discharge mode, and the remaining capacity C2 was recorded. Three charge-discharge cycles were then performed using the standard charge-discharge mode, and the maximum discharge capacity was taken as the recovered capacity C3. Remaining capacity = C2 / C1 × 100%; Capacity recovery rate = C3 / C1 × 100%. The results are shown in Table 1.

[0124] 6. Impedance: After capacity gradation, the sodium-ion battery was charged to 50% SOC. EIS impedance testing was performed using an electrochemical workstation with an amplitude of 5mV and a frequency range of 100,000Hz-0.05Hz. The obtained data were fitted using Zview software to obtain the interface impedance. The results are shown in Table 1.

[0125] 7. Cyclic Performance Test: Under 25℃ conditions, charge at a constant current rate of 1C to 3.4V, then charge at a constant voltage rate of 1C to 3.4V, and then discharge at a discharge rate of 1C to 0.8V. Repeat this charge-discharge cycle 1000 times. Measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 1000th cycle. 1000 The capacity retention rate after 1000 cycles is Q = Q 1000 / Q1×100%. The results are shown in Table 1.

[0126] Under conditions of 60℃, the capacitor is charged at a constant current rate of 1C to 3.4V, then charged at a constant voltage rate of 1C to 3.4V, and then discharged at a discharge rate of 1C to 0.8V. This charge-discharge cycle is repeated 500 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q at the 500th cycle are measured. 500 The capacity retention rate Q after 500 cycles is Q = Q 500 / Q1×100%. The results are shown in Table 1.

[0127] At -5℃, the capacitor was charged at a constant current rate of 1C to 3.4V, then charged at a constant voltage rate of 1C to 3.4V, and then discharged at a discharge rate of 1C to 0.8V. This charge-discharge cycle was repeated 200 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q at the 200th cycle were measured. 200 The capacity retention rate Q after 200 cycles is Q = Q 200 / Q1×100%. The results are shown in Table 1.

[0128] 8. Rate Performance Test: At 25℃, the battery is charged at a constant current rate of 1C to a voltage of 4.5V, then charged at a constant voltage of 4.5V until the current equals 0.05C. After resting for 5 minutes, it is discharged at a constant current rate of 1C to a voltage of 2.5V. The capacity at this point is recorded as the discharge capacity at the 1C rate. After resting for 10 minutes, it is charged at a constant current rate of 2C to a voltage of 4.5V, then charged at a constant voltage of 4.5V until the current equals 0.05C. After resting for 5 minutes, it is discharged at a constant current rate of 2C to a voltage of 2.5V. The capacity at this point is recorded as the discharge capacity at the 2C rate. The ratio of the discharge capacity at the 2C rate to the discharge capacity at the 1C rate is the 2C rate performance. The results are shown in Table 1.

[0129] Table 1

[0130] As shown in Table 1, compared with the comparative example, the battery provided in this application satisfies Formula 1, that is, by introducing sulfate ester additives into the electrolyte of the battery and combining the characteristics of hard carbon materials, this application provides an optimized battery design that can significantly improve the overall performance of the battery, namely, improve the battery's initial coulombic efficiency, cycle stability, impedance, rate performance and storage performance.

[0131] Compared to Comparative Example 4, the battery in Example 4 has a hard carbon specific surface area greater than 80 m². 2 In a high-activity system, the amount of sulfate ester additives added satisfies Equation 1, which improves the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance. Example 5, based on Example 4, adds an additional 0.5% NaPO2F2 as a stabilizer, further improving the battery's initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0132] Compared to Comparative Example 5, the battery in Example 6, with its low specific surface area hard carbon and fewer active sites, still showed significant improvements in initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance despite the addition amount of sulfate ester additives satisfying Equation 1. In contrast, Comparative Example 5, due to excessive addition of sulfate ester additives, resulted in a thicker SEI film, blocking sodium ion transport pathways and leading to poorer initial coulombic efficiency, cycle stability, impedance, rate performance, and storage performance.

[0133] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to what has been described above, and various modifications and changes may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A battery, characterized in that, The battery includes a negative electrode sheet and an electrolyte. The negative electrode sheet includes a negative electrode active material, which includes a hard carbon material. The electrolyte includes sulfate ester additives. The battery satisfies the following formula 1: k ranges from -0.5 to 0.5; The sulfate ester additive accounts for Z% of the mass percentage of the electrolyte; the specific surface area of ​​the hard carbon material is Em. 2 / g; the percentage of oxygen atoms in the hard carbon material relative to the total number of atoms in the hard carbon material is X%; the percentage of nitrogen atoms in the hard carbon material relative to the total number of atoms in the hard carbon material is Y%.

2. The battery according to claim 1, characterized in that, The specific surface area of ​​the hard carbon material is 3m². 2 / g~100m 2 / g.

3. The battery according to claim 1 or 2, characterized in that, The percentage of oxygen atoms in the hard carbon material is 1.0% to 15.0% of the total number of atoms in the hard carbon material.

4. The battery according to any one of claims 1-3, characterized in that, The percentage of nitrogen atoms in the hard carbon material is 0.1% to 0.5% of the total number of atoms in the hard carbon material.

5. The battery according to any one of claims 1-4, characterized in that, The sulfate ester additive accounts for 0.01% to 6.8% of the mass of the electrolyte.

6. The battery according to any one of claims 1-5, characterized in that, The condition E satisfies 80 < E ≤ 100.

7. The battery according to any one of claims 1-6, characterized in that, The electrolyte also includes a stabilizer; The stabilizer includes at least one of monofluorophosphate, difluorophosphate, pentafluoroethyl trifluoroborate, tetraphenylborate, difluorooxalate borate, dioxalate borate, and tetrafluoroborate.

8. The battery according to claim 7, characterized in that, The stabilizer accounts for 0.2% to 0.8% of the mass of the electrolyte.

9. The battery according to any one of claims 1-8, characterized in that, The sulfate ester additives include at least one of vinyl sulfate (DTD), propylene sulfate (PES), dimethyl sulfate (DMS), diethyl sulfate (DES), dipropyl sulfate (DPS), dibutyl sulfate (DBS), pentaerythritol bicyclic sulfate (TDT), bicyclic [2.2.1]heptane-5-sulfate, dicyclopentadienyl sulfate, and tricyclic decyl sulfate.

10. The battery according to any one of claims 1-9, characterized in that, The battery includes a sodium-ion battery.

11. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1-10.

Images