Electrolyte, battery, and electrical device

Abstract

An electrolyte, a battery, and an electrical device. The electrolyte comprises a first additive, the first additive comprising a compound represented by general chemical structural formula I: In formula I, R1 and R2 are independently selected from a hydrogen atom, a halogen atom, a C1-C10 alkyl group, a C1-C10 alkoxy group, a C2-C10 carboxylate group, a C2-C10 carbonate group, a C1-C10 fluoro- or bromo-substituted alkyl group, a C1-C10 fluoro- or bromo-substituted alkoxy group, a C2-C10 fluoro- or bromo-substituted carboxylate group, a C2-C10 fluoro- or bromo-substituted carbonate group, a group represented by general chemical structural formula II, or a group represented by general chemical structural formula III: In formula II and formula III, m and n are each natural numbers greater than or equal to 0.

Description

Electrolytes, batteries and electrical equipment

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese patent application filed on January 2, 2025, with application number 202510010349.1 and entitled "Electrolyte, Battery and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and in particular to an electrolyte, a battery, and an electrical device. Background Technology

[0004] In related technologies, the key to improving the cycle performance of sodium-ion batteries lies in the construction of a low-impedance, high-toughness solid electrolyte interphase (SEI) membrane. An effective SEI membrane can significantly reduce system impedance, exhibit high sodium-ion migration kinetics, promote the full utilization of the positive and negative electrode capacities, and simultaneously suppress side reactions between the electrolyte and the electrode plates, thereby achieving a comprehensive improvement in the cycle performance and even the overall performance of sodium-ion batteries. However, the SEI membrane in sodium-ion batteries using conventional electrolytes has poor stability, which is detrimental to the long-term stable use of sodium-ion batteries.

[0005] Public content

[0006] This disclosure aims to at least address one of the technical problems existing in the prior art. To this end, one object of this disclosure is to provide an electrolyte employing a first additive that can promote the formation of a low-resistance, dense, and stable SEI film, thereby promoting the stable performance of the negative electrode capacity of the battery.

[0007] Another object of this disclosure is to provide a battery using the above-described electrolyte.

[0008] Another object of this disclosure is to provide an electrical device using the aforementioned battery.

[0009] The electrolyte according to a first aspect embodiment of the present disclosure includes a first additive, the first additive comprising a compound having a general chemical formula I:

[0010] In Formula I, R1 and R2 are independently selected from hydrogen atoms, halogen atoms, C1-C10 alkyl groups, C1-C10 alkoxy groups, C2-C10 carboxylic acid ester groups, C2-C10 carbonate groups, C1-C10 fluoro or brominated alkyl groups, C1-C10 fluoro or brominated alkoxy groups, C2-C10 fluoro or brominated carboxylic acid ester groups, C2-C10 fluoro or brominated carbonate groups, groups having general chemical formula II, or groups having general chemical formula III.

[0011] In Equations II and III, m and n are natural numbers greater than or equal to 0.

[0012] According to the electrolyte of the first aspect of this disclosure, by using an electrolyte containing a first additive, it is possible to promote the formation of a low-resistance and dense SEI film at the positive and negative electrodes. The SEI film has a high sodium ion migration kinetics, which promotes the capacity utilization of the positive and negative electrodes. At the same time, it can effectively isolate the contact between the electrolyte and the electrode, suppress the occurrence of side reactions, thereby significantly improving the room temperature cycle performance of the sodium-ion battery and enhancing other performance characteristics of the sodium-ion battery.

[0013] According to some embodiments of this disclosure, R1 and R2 are independently selected from groups having the general chemical formula II:

[0014] In Formula II, m is a natural number greater than or equal to 0; or, R1 and R2 are independently selected from groups having the general chemical formula III:

[0015] In Equation III, n is a natural number greater than or equal to 0.

[0016] According to some embodiments of this disclosure, the content of the first additive is 0.1% to 10% by mass percentage.

[0017] According to some embodiments of this disclosure, the content of the first additive is 1% to 5% by mass percentage.

[0018] According to some embodiments of this disclosure, when R1 and R2 are independently one of hydrogen atom, halogen atom, C1-C10 alkyl, C1-C10 alkoxy, C2-C10 carboxylic acid ester, C2-C10 carbonate, C1-C10 fluoro or brominated alkyl, C1-C10 fluoro or brominated alkoxy, C2-C10 fluoro or brominated carboxylic acid ester and C2-C10 fluoro or brominated carbonate, the electrolyte further includes a second additive, the second additive including at least one of tris(trimethylsilane) phosphate, tris(trimethylsilyl) phosphite and tris(trimethylsilane) borate.

[0019] According to some embodiments of this disclosure, the content of the second additive is 0.1% to 10% by mass percentage.

[0020] According to some embodiments of this disclosure, the electrolyte further comprises, by mass percentage, 5 wt% to 45 wt% of sodium salt and 45 wt% to 94.7 wt% of solvent.

[0021] According to some embodiments of this disclosure, the sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalateborate, sodium bis(oxalateborate), sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate, and sodium chloride.

[0022] According to some embodiments of this disclosure, the solvent includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and bis(2,2,2-trifluoroethyl) ether.

[0023] According to some embodiments of this disclosure, the electrolyte further includes, by weight percentage, a third additive, which includes at least one selected from fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, propylene sulfate, propylene-1,3-sulfonyl lactone, ethylene sulfate, methanedisulfonate, succinate, adiponitrile, trimethyl phosphate, triphenyl phosphate, trifluoromethylsilane, ethoxy(pentafluoro)cyclotriphosphazene, and biphenyl.

[0024] According to some embodiments of this disclosure, the content of the third additive is 0.1% to 10% by mass percentage.

[0025] The battery according to a second aspect embodiment of the present disclosure includes the electrolyte according to any of the embodiments of the first aspect described above.

[0026] According to some embodiments of this disclosure, the battery includes a sodium-ion battery.

[0027] The electrical device according to a third aspect of this disclosure includes the battery described in any of the second aspects above.

[0028] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0029] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 is a performance test comparison chart of batteries prepared according to the electrolyte of this disclosure, wherein Experiment 1, Experiment 4, and Experiments 6-9 correspond to the batteries prepared in Examples 1, 4, and 6-9, respectively;

[0031] Figure 2 is a performance test comparison chart of batteries prepared according to the electrolyte of this disclosure, wherein Experiment 1, Experiment 2, Experiment 4 and Experiment 5 correspond to the batteries prepared in Example 1, Example 2, Example 4 and Example 5, respectively.

[0032] Figure 3 is a performance comparison chart of batteries prepared according to the electrolyte of this disclosure, wherein Experiment 1-Experiment 3 correspond to the batteries prepared in Examples 1-3, respectively. Detailed Implementation

[0033] The embodiments of this disclosure are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The electrolyte according to the first aspect of this disclosure is described below with reference to FIG1. ​​In the following description of this disclosure, the electrolyte used in a sodium-ion battery is used as an example.

[0034] The electrolyte according to the first aspect of this disclosure includes, by mass percentage, a first additive, the first additive comprising a compound having a general chemical formula I:

[0035] In Formula I, R1 and R2 are independently selected from hydrogen atoms, halogen atoms, C1-C10 alkyl groups, C1-C10 alkoxy groups, C2-C10 carboxylic acid ester groups, C2-C10 carbonate groups, C1-C10 fluoro or brominated alkyl groups, C1-C10 fluoro or brominated alkoxy groups, C2-C10 fluoro or brominated carboxylic acid ester groups, C2-C10 fluoro or brominated carbonate groups, groups having general chemical formula II, or groups having general chemical formula III.

[0036] In Equations II and III, m and n are natural numbers greater than or equal to 0.

[0037] In other words, R1 and R2 in Formula I can be the same group or different groups. m and n can be natural numbers such as 0, 1, 2, ... For example, R 1、When R2 is independently selected from a halogenated group, it can generate more sodium halide inorganic substances during SEI film formation, thus improving the stability of the SEI film. Using an electrolyte with a first additive promotes the formation of a low-resistance and dense SEI film at both the positive and negative electrodes. The SEI film has high sodium ion migration kinetics, promoting the full utilization of the positive and negative electrode capacities. Simultaneously, it effectively isolates the electrolyte from the electrode, suppressing side reactions and significantly improving the room-temperature cycle performance of sodium-ion batteries, as well as other performance characteristics.

[0038] For example, when the substituent is a trimethylsiloxane group, using the first additive can improve the electrode interface performance and form a stable interface film. The trimethylsiloxane group can participate in the reaction on the electrode surface, forming a stable and uniform solid electrolyte interphase (SEI) film. This film effectively prevents direct contact between the electrolyte and the electrode material, reducing side reactions and thus improving the battery's cycle stability and lifespan. Furthermore, it can reduce interfacial impedance. The interface film formed by the first additive has good ionic conductivity, reducing the interfacial impedance between the electrode and the electrolyte, making it easier for sodium ions to transport between the electrode and the electrolyte during charge and discharge, improving the battery's rate performance—that is, maintaining high capacity and good performance even under high current charge and discharge. The trimethylsiloxane group has a certain antioxidant capacity, which can inhibit the oxidative decomposition of the electrolyte under high voltage. When sodium-ion batteries are operating, especially under high-voltage charge and discharge conditions, the electrolyte is prone to oxidation, leading to a decline in battery performance. Adding an additive containing a trimethylsiloxane group can improve the electrolyte's antioxidant stability, ensuring normal battery operation at higher voltages.

[0039] When the substituent is a trimethylsilyl group, the first additive can form a stable solid electrolyte interphase (SEI) film, improving film stability. The trimethylsilyl group can participate in the formation of the SEI film, making its structure more stable, reducing film breakage and reconstruction, helping to maintain the integrity of the electrode structure, and extending the battery's cycle life. Furthermore, it can effectively suppress side reactions. Siloxane bonds are easily broken by hydrolysis or react with impurities such as hydrofluoric acid in the electrolyte, thus suppressing side reactions between the electrolyte and electrode materials and reducing battery performance degradation. Moreover, it can improve the battery's low-temperature performance. The SEI film formed with the participation of the trimethylsilyl group has good kinetic characteristics at low temperatures, thereby improving the battery's low-temperature performance and enabling it to maintain good charge-discharge performance even in low-temperature environments.

[0040] In conclusion, trimethylsilyl groups, as additives for sodium-ion battery electrolytes, can improve the performance of sodium-ion batteries in multiple ways, which is of great significance for promoting the development of sodium-ion batteries.

[0041] According to the electrolyte of this disclosure, by using an electrolyte containing a first additive, it is possible to promote the formation of a low-resistance and dense SEI film at the positive and negative electrodes. The SEI film has a high sodium ion migration kinetics, which promotes the capacity utilization of the positive and negative electrodes. At the same time, it can effectively isolate the contact between the electrolyte and the electrode, suppress the occurrence of side reactions, thereby significantly improving the room temperature cycle performance of the sodium-ion battery and other performance characteristics of the sodium-ion battery.

[0042] According to some preferred embodiments of this disclosure, R1 and R2 are independently selected from groups having the general chemical formula II:

[0043] In Equation II, m is a natural number greater than or equal to 0.

[0044] For example, m can be a natural number such as 0, 1, 2, ... Using a first additive with a group of formula II can improve the electrode interface performance and form a stable interface film. The trimethylsiloxane group can participate in the reaction on the electrode surface, forming a stable and uniform solid electrolyte interfacial film (SEI film). This film effectively prevents direct contact between the electrolyte and the electrode material, reducing the occurrence of side reactions, thereby improving the cycle stability and lifespan of the battery. Furthermore, it can reduce interfacial impedance. The interface film formed by the first additive has good ionic conductivity, which can reduce the interfacial impedance between the electrode and the electrolyte, making it easier for sodium ions to transport between the electrode and the electrolyte during charging and discharging, improving the battery's rate performance, i.e., maintaining high capacity and good performance even under high current charging and discharging. The trimethylsiloxane group has a certain antioxidant capacity, which can inhibit the oxidative decomposition of the electrolyte under high voltage. When sodium-ion batteries are working, especially under high voltage charging and discharging conditions, the electrolyte is prone to oxidation, leading to a decline in battery performance. Adding a first additive containing a trimethylsiloxane group can improve the antioxidant stability of the electrolyte, ensuring normal operation of the battery at higher voltages.

[0045] According to some preferred embodiments of this disclosure, R1 and R2 are independently selected from groups having the general chemical formula III:

[0046] In Equation III, n is a natural number greater than or equal to 0.

[0047] For example, n can be a natural number such as 0, 1, 2, ... When the substituent is a trimethylsilyl group, using a first additive with a group of formula III can form a stable solid electrolyte interphase (SEI) film, improving film stability. The trimethylsilyl group can participate in the formation of the SEI film, and the organic sodium salt it forms can reduce the inorganic sodium salt components such as NaF and NaCO that are easily formed in traditional electrolyte systems, thereby making the SEI film structure more stable, reducing film rupture and reconstruction, helping to maintain the integrity of the electrode structure, and extending the cycle life of the battery. In addition, it can effectively suppress side reactions. Siloxane bonds are easily broken and hydrolyzed or react with impurities such as hydrofluoric acid in the electrolyte, thereby suppressing side reactions between the electrolyte and electrode materials and reducing battery performance degradation. In addition, it can enhance the battery's overcharge and over-discharge tolerance. The trimethylsilyl group can form a protective film on the electrode surface. This film can buffer the volume changes of the electrode material during overcharge and over-discharge to a certain extent, reducing structural damage to the electrode material, thereby improving the battery's overcharge and over-discharge tolerance and enhancing battery safety performance. Moreover, it can improve the low-temperature performance of the battery. The trimethylsilyl group can reduce the viscosity of the electrolyte and increase the ionic conductivity of the electrolyte at low temperatures, thereby improving the low-temperature performance of the battery and enabling the battery to maintain good charge and discharge performance in low-temperature environments.

[0048] According to some embodiments of this disclosure, the content of the first additive is 0.1% to 10% by mass percentage. This setting is reasonable. As shown in the test results of the embodiments described below (Table 1), when the content of the first additive is between 0.1% and 10%, the electrolyte exhibits better performance, which is beneficial for the electrolyte's performance and thus its use. Furthermore, it can reduce the amount of electrolyte added, thereby lowering costs.

[0049] Preferably, the content of the first additive is 1% to 5% by mass percentage. That is, when the content of the first additive is within the above-mentioned range, the performance of the electrolyte is optimal, and at the same time, the content of the first additive is reduced, further reducing the production cost of the electrolyte.

[0050] According to some embodiments of this disclosure, when R1 and R2 are independently selected from one of hydrogen atom, halogen atom, C1-C10 alkyl, C1-C10 alkoxy, C2-C10 carboxylic acid ester, C2-C10 carbonate, C1-C10 fluoro or brominated alkyl, C1-C10 fluoro or brominated alkoxy, C2-C10 fluoro or brominated carboxylic acid ester and C2-C10 fluoro or brominated carbonate, the electrolyte further comprises 0.1% to 10% of a second additive by mass percentage, the second additive comprising at least one of tris(trimethylsilane) phosphate, tris(trimethylsilyl) phosphite and tris(trimethylsilane) borate.

[0051] For example, the second additive is a dehydrating or HF-removing additive. When R1 and R2 are independently selected from silicon-free groups, the combined use of the first and second additives can exert a significant advantage. Specifically, they can jointly promote the formation of Na2SO4 / ROSO3Na (mainly), Na2SO3 / ROSO2Na, and Na2S / Na on the electrode surface. x A low-impedance, dense, and stable solid electrolyte interphase (SEI) film composed of components such as sulfur (S) is formed. This SEI film plays several important roles. On the one hand, it promotes the stable utilization of the negative electrode capacity, ensuring that the negative electrode maintains good performance throughout the charge and discharge process, allowing for full and stable utilization of the battery capacity. On the other hand, it effectively suppresses the occurrence of side reactions between the electrode and the electrolyte, greatly reducing the adverse effects of side reactions on battery performance. In this way, ultra-long stable cycling is achieved, providing a solid guarantee for the reliable operation of the battery in various application scenarios.

[0052] For example, when the electrolyte includes a first additive, a second additive, and a solvent, the content of the first additive is 0.1% to 10%, the content of the second additive is 0.1% to 10%, and the remaining amount is made up to 100% by the solvent. This configuration ensures that the contents of the first and second additives are appropriately set. When the contents of the first and second additives are respectively between 0.1% and 10%, the performance of the electrolyte is further improved, thus making the electrolyte more suitable for use.

[0053] According to some embodiments of this disclosure, the product also includes 5 wt% to 45 wt% sodium salt and 45 wt% to 94.7 wt% solvent by mass percentage.

[0054] In other words, besides the first and / or second additives, the electrolyte also includes sodium salt and solvent. The sodium salt accounts for 4-45% of the total mass. Sodium salt plays a crucial role in the electrolyte, providing sodium ions to participate in the battery's charging and discharging process, ensuring normal battery operation. Different types of sodium salt have different properties. For example, some sodium salts may have high ionic conductivity, accelerating ion transport between electrodes and improving battery charging and discharging efficiency. Other sodium salts may have better stability, maintaining good performance over a wider temperature range. The solvent is an important component of the electrolyte, dissolving sodium salt and other additives to form a homogeneous solution. A suitable solvent should have good solubility, a high dielectric constant, and low viscosity. A high dielectric constant helps dissolve sodium salt, allowing it to exist in ionic form in solution. Low viscosity facilitates rapid ion migration, improving battery performance. Simultaneously, the solvent should also have good chemical and thermal stability, remaining stable under battery operating conditions without decomposition or deterioration. In summary, sodium salt and solvent work together in the electrolyte to provide crucial support for battery performance.

[0055] According to some embodiments of this disclosure, the sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalateborate, sodium bis(oxalateborate), sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate, and sodium chloride.

[0056] For example, the concentration of sodium salt is 0.5 mol / L to 5 mol / L. This setting, using the aforementioned sodium salt to prepare the electrolyte, is beneficial for the use of the electrolyte and for maximizing its performance. Furthermore, sodium-ion batteries prepared using the electrolyte of this disclosure have advantages such as lower cost, excellent cycle performance, good high and low temperature performance, and safety, which are conducive to the long-term use of sodium-ion batteries. In addition, the aforementioned sodium salt is widely available and readily purchased, thus facilitating electrolyte preparation.

[0057] According to some embodiments of this disclosure, the solvent includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and bis(2,2,2-trifluoroethyl) ether. Therefore, using the above-mentioned solvents facilitates the dissolution of sodium salts, the first additive, and the second additive, thereby facilitating the preparation of the electrolyte and simplifying the operation. Furthermore, the dissolution rate is fast and the dissolution effect is good. In addition, the use of the above-mentioned solvents has no effect on the performance of the electrolyte, which is beneficial to the performance of the electrolyte.

[0058] According to some embodiments of this disclosure, the product further includes 0.1% to 10% by weight of a third additive, which includes at least one selected from fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulpholol, propylene sulfate, propylene-1,3-sulfonyl lactone, vinyl sulfate, methanedisulfonate, succinate, adiponitrile, trimethyl phosphate, triphenyl phosphate, trifluoromethylsilane, ethoxy(pentafluoro)cyclotriphosphazene, and biphenyl.

[0059] For example, fluoroethylene carbonate can generally improve the stability and electrochemical performance of electrolytes, contributing to the formation of a more stable solid electrolyte interphase (SEI) film, thereby improving battery cycle life and safety. Ethylene carbonate can also participate in SEI film formation, enhancing battery cycle performance and high-temperature stability. 1,3-Propane sulpholol can improve the ionic conductivity of electrolytes, enhancing battery charge-discharge performance. Propylene sulfate, propylene-1,3-sulfonyl lactone, and ethylene sulfate may play a role in improving the conductivity, stability, and compatibility with electrode materials of electrolytes. Butadionitrile and adiponitrile are often used as electrolyte additives to improve battery performance, such as enhancing ion transport and improving high-temperature performance. Trimethyl phosphate and triphenyl phosphate have flame-retardant properties and can improve electrolyte safety. Trifluoromethylsilane may help improve the interfacial properties between the electrolyte and the electrode. Ethoxy(pentafluoro)cyclotriphosphazene has some effect on improving the stability and flame retardancy of electrolytes. Biphenyl can improve the antioxidant properties of electrolytes. In summary, the combined use of these third additives can optimize the electrolyte in terms of stability, conductivity, and safety according to different battery requirements, thereby improving the overall performance of the battery.

[0060] Depending on the application requirements of the electrolyte, other film-forming additives, flame-retardant additives, and overcharge protection additives may also be included. In other words, different types of additives can be added according to the different application scenarios of sodium-ion batteries. Furthermore, the materials for the aforementioned third additive are readily available, which is beneficial for electrolyte preparation.

[0061] The battery according to a second aspect embodiment of the present disclosure includes the electrolyte according to the first aspect embodiment described above.

[0062] According to the battery of the second aspect of this disclosure, by using the above-described electrolyte, the room temperature cycle performance of the sodium-ion battery can be significantly improved, as well as other performance characteristics of the sodium-ion battery, which is beneficial for its long-term use. For example, including a sodium-ion battery in the battery is beneficial for maximizing the performance of the sodium-ion battery.

[0063] The electrical device according to a third aspect of the present disclosure includes a battery according to the second aspect of the present disclosure.

[0064] According to the third aspect of this disclosure, the electrical equipment using the aforementioned battery improves its performance. For example, the electrical equipment includes vehicles, aircraft, ships, computers, energy storage cabinets, etc.

[0065] The embodiments of this disclosure are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known to others. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0066] The electrolyte and battery of this disclosure are illustrated through exemplary embodiments and comparative examples. The performance of the batteries of Examples 1-9 and Comparative Examples 1-4 is tested below.

[0067] The calculation method for capacity division and first-efficiency is as follows: At room temperature, the fresh battery is charged to 3.6V at a constant current and constant voltage of 1C, and the cutoff current is 0.05C. The formation charging capacity is recorded. After standing for 10 minutes, the battery is discharged to 1.5V at a constant current of 1C. The capacity division discharge capacity is recorded.

[0068] The initial efficiency is calculated using the following formula: Initial efficiency = Discharge capacity / Formation charge capacity.

[0069] Battery cycle performance test: The battery is charged and discharged at a current density of 1C, the test voltage range is 1.5 to 3.6V, and the test temperature is 25℃.

[0070] The capacity retention rate is calculated using the following formula: Current cycle capacity retention rate = Current cycle discharge capacity / First cycle discharge capacity.

[0071] Example 1

[0072] (1) Preparation of electrolyte

[0073] First, propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) were mixed in a mass ratio of 20:10:70 to prepare a mixed solvent. The water in the mixed solvent was removed by molecular sieve. 1 mol / L sodium hexafluorophosphate was added in batches to the dry and anhydrous mixed solvent while stirring. After cooling, 2 wt% of 2λ6,7λ6-1,3,6,8-tetraoxa-2,7-dithiaspiro[4.4]nonane-2,2,7,7-tetraone (TTDT) was added as the first additive to finally obtain a clear, colorless, and transparent electrolyte for sodium-ion batteries.

[0074] Among them, the above TTDT is the compound in formula (1) where R1 and R2 are both selected from hydrogen atoms, and its structural formula is as follows (4):

[0075] (2) Preparation of positive electrode

[0076] A positive electrode material, such as sodium iron pyrophosphate (NFPP), a binder, such as polyvinylidene fluoride (PVDF), and a conductive agent, such as acetylene black (SuperP), are mixed in a mass ratio of 8:1:1, and a certain amount of N-methylpyrrolidone (NMP) is added to make a positive electrode slurry. The solid content of the slurry is adjusted to about 50%. After degassing and sieving, the slurry is uniformly coated on the surface of aluminum foil. After drying, rolling, and cutting, a positive electrode sheet is obtained.

[0077] (3) Preparation of negative electrode

[0078] The negative electrode material hard carbon (HC), the composite binder styrene-butadiene rubber (SBR) / carboxymethyl cellulose (CMC) and the conductive agent acetylene black (SuperP) are mixed in a mass ratio of 8:1:1, and deionized water is added to prepare the negative electrode slurry. The solid content is adjusted to about 45%, and after degassing and sieving, it is uniformly coated on the surface of aluminum foil. After drying, rolling and cutting, the negative electrode sheet is obtained.

[0079] (4) Battery manufacturing

[0080] The negative electrode, separator, and positive electrode are stacked in sequence to form a cell, which is then packaged in an aluminum-plastic shell. After the cell is baked to remove moisture, the electrolyte prepared in (1) is injected into the soft-pack battery. After aging, formation, and capacity testing, a soft-pack sodium-ion battery is obtained.

[0081] (5) Performance Testing

[0082] Examples 2-5

[0083] The main difference from Example 1 is the different additives (i.e., whether to add a second and third additive, and the selection of the type and amount of additives), as shown in Table 1.

[0084] Among them, the first additive in Example 4, 4,9-bis(trimethylsiloxy)-2λ6,7λ6-1,3,6,8-tetraoxa-2,7-dithiaspiro[4.4]nonane-2,2,7,7-tetraone (BTMSTTDT), is the compound in formula (1) where R1 and R2 are both selected from trimethylsiloxane groups, and its structural formula is as follows (5):

[0085] The first additive in Example 5, 4,9-difluoro-2λ6,7λ6-1,3,6,8-tetraoxa-2,7-dithiaspiro[4.4]nonane-2,2,7,7-tetraone (DFTDTT), is a compound in formula (1) where R1 and R2 are both selected from fluorine atoms, and its structural formula is as follows (6):

[0086] Example 6

[0087] The main difference from Example 1 is the amount of the first additive added.

[0088] Example 7

[0089] The main difference from Example 1 is the amount of the first additive added.

[0090] Example 8

[0091] The main difference from Example 1 is the amount of the first additive added.

[0092] Example 9

[0093] The main difference from Example 1 is the amount of the first additive added.

[0094] Comparative Examples 1-4

[0095] The main difference from Example 4 is the different additives, that is, the electrolyte does not include the first additive. Information on the specific additives is shown in Table 1.

[0096] The charging performance of the batteries prepared in Examples 1-9 and Comparative Examples 1-4 was measured, and the results are shown in Table 1.

[0097] Table 1. Parameter selection and measurement results for Examples 1-9 and Comparative Examples 1-4.

[0098] Referring to Figure 1 and the data from Examples 1-9 in Table 1, it can be seen that the battery prepared using the electrolyte containing the first additive has a capacity retention rate after 600 cycles at 1C room temperature. According to Examples 1 and 3, when the first additive is 2λ6,7λ6-1,3,6,8-tetraoxa-2,7-dithiaspiro[4.4]nonane-2,2,7,7-tetraone (TTDT), the capacity retention rate after 600 cycles at 1C room temperature is relatively high, reaching 95.63%. Adding the second additive to the first additive further increases the capacity retention rate after 600 cycles at room temperature, further improving the battery's performance. As shown in Example 4, the battery with the best performance is prepared when the first additive is 4,9-bis(trimethylsiloxy)-2λ6,7λ6-1,3,6,8-tetraoxa-2,7-dithiaspiro[4.4]nonane-2,2,7,7-tetraone (BTMSTTDT). As can be seen from the comparison of Examples 1 and 4 with Comparative Examples 1-4, the capacity retention of the electrolyte without the first additive is significantly reduced after 600 cycles at room temperature, resulting in decreased battery performance. It should be noted that TMSP in Table 1 refers to tris(trimethylsilane) phosphate, FEC refers to fluoroethylene carbonate, and DTD refers to ethylene sulfate.

[0099] As shown in Table 1, Examples 1 and 6-9, the preferred addition amount of the first additive is 1% to 5% to improve electrolyte performance. Examples 2 and 3 show that adding the third additive, FEC, reduces the capacity retention rate after 600 cycles at 1C room temperature. This is because FEC increases battery impedance, which generally reduces room temperature cycle capacity retention. To improve overall battery performance, a third additive can be added as needed. For example, while adding FEC reduces capacity retention after 600 cycles at 1C room temperature, it improves the high-temperature performance of the electrolyte, thus enhancing overall battery performance.

[0100] The sodium-ion battery, other components of the electrical equipment, and operation according to the embodiments of this disclosure are known to those skilled in the art and will not be described in detail here.

[0101] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0102] In the description of this disclosure, "multiple" means two or more.

[0103] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0104] Although embodiments of this disclosure have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. An electrolyte, characterized in that, The first additive includes a compound having a general chemical formula I: In Formula I, R1 and R2 are independently selected from hydrogen atoms, halogen atoms, C1-C10 alkyl groups, C1-C10 alkoxy groups, C2-C10 carboxylic acid ester groups, C2-C10 carbonate groups, C1-C10 fluoro or brominated alkyl groups, C1-C10 fluoro or brominated alkoxy groups, C2-C10 fluoro or brominated carboxylic acid ester groups, C2-C10 fluoro or brominated carbonate groups, groups having general chemical formula II, or groups having general chemical formula III. In Equations II and III, m and n are natural numbers greater than or equal to 0.

2. The electrolyte according to claim 1, characterized in that, R1 and R2 are independently selected from groups having the general chemical formula II: In Equation II, m is a natural number greater than or equal to 0; or R1 and R2 are independently selected from groups having the general chemical formula III: In Equation III, n is a natural number greater than or equal to 0.

3. The electrolyte according to claim 1 or 2, characterized in that, The content of the first additive is 0.1% to 10% by mass percentage.

4. The electrolyte according to claim 3, characterized in that, The content of the first additive is 1% to 5% by mass percentage.

5. The electrolyte according to any one of claims 1-4, characterized in that, When R1 and R2 are independently one of hydrogen atom, halogen atom, C1-C10 alkyl, C1-C10 alkoxy, C2-C10 carboxylic acid ester, C2-C10 carbonate, C1-C10 fluoro or brominated alkyl, C1-C10 fluoro or brominated alkoxy, C2-C10 fluoro or brominated carboxylic acid ester and C2-C10 fluoro or brominated carbonate, the electrolyte further includes a second additive, the second additive including at least one of tris(trimethylsilane) phosphate, tris(trimethylsilyl) phosphite and tris(trimethylsilane) borate.

6. The electrolyte according to claim 5, characterized in that, The content of the second additive is 0.1% to 10% by mass percentage.

7. The electrolyte according to any one of claims 1-6, characterized in that, It also includes 5 wt% to 45 wt% sodium salt and 45 wt% to 94.7 wt% solvent by mass percentage.

8. The electrolyte according to claim 7, characterized in that, The sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalateborate, sodium bis(oxalateborate), sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate, and sodium chloride.

9. The electrolyte according to claim 7 or 8, characterized in that, The solvent includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and bis(2,2,2-trifluoroethyl) ether.

10. The electrolyte according to any one of claims 1-9, characterized in that, It also includes a third additive, which comprises at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, propylene sulfate, propylene-1,3-sulfonyl lactone, ethylene sulfate, methanedisulfonate, succinate, adiponitrile, trimethyl phosphate, triphenyl phosphate, trifluoromethylsilane, ethoxy(pentafluoro)cyclotriphosphazene, and biphenyl.

11. The electrolyte according to claim 10, characterized in that, The content of the third additive is 0.1% to 10% by mass percentage.

12. A battery, characterized in that, Includes the electrolyte according to any one of claims 1-11.

13. The battery according to claim 12, characterized in that, The battery includes a sodium-ion battery.

14. An electrical appliance, characterized in that, Includes the battery according to claim 12 or 13.

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