Non-aqueous electrolyte and sodium ion battery

Abstract

The invention relates to a non-aqueous electrolyte and a sodium ion battery. The non-aqueous electrolyte comprises an electrolyte, a non-aqueous organic solvent and an additive, wherein the additive comprises an additive A with a structure as shown in a formula I and an additive B with a structure as shown in a formula II. By adding the additive A and the additive B into the non-aqueous electrolyte, the additive A and the additive B play a synergistic role, so that the cycle impedance of the sodium ion battery at high temperature can be reduced, the cycle life of the sodium ion battery can be prolonged, the side reaction of sodium and an electrolyte interface can be reduced, the high-temperature cycle stability of the sodium ion battery can be improved, and the application requirements of the sodium ion battery at high temperature can be met. The sodium ion battery prepared from the non-aqueous electrolyte provided by the invention has good stability and safety, the capacity retention ratio of the sodium ion battery under the test conditions of 25 DEG C and 1C is 87-91.1%, the capacity retention ratio of the sodium ion battery under the test conditions of 45 DEG C and 1C is 84.1-89.7%, and the DCR of 50% SOC is 95.2-107.2 m omega.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a non-aqueous electrolyte and a sodium ion battery. Background Art

[0002] The intensification of environmental pollution has greatly increased the demand for green energy, leading to an increased interest in high-energy-density lithium-ion batteries, which in turn has driven the development of electric vehicles and energy storage systems. However, due to the low abundance of lithium resources in the earth's crust, concerns about lithium supply have been raised. Secondly, lithium-ion batteries encounter high cost, sustainability, and safety issues. Sodium has been widely studied as an effective candidate material for lithium due to its high abundance, low cost, and high energy density.

[0003] However, with the increasing number of battery safety accidents, the safety of sodium-ion batteries has become a primary concern. The hard carbon negative electrode used in sodium-ion batteries has a lower reaction potential than the graphite negative electrode. During the charging process, especially at high rates, sodium precipitation is very likely to occur. Since the reaction activity of metallic sodium is stronger than that of metallic lithium, when sodium precipitation occurs, metallic sodium will react violently with the electrolyte, resulting in a rapid increase in the negative electrode interface impedance. Furthermore, the increase in the negative electrode interface impedance will intensify the occurrence of sodium precipitation reaction. When the sodium precipitation reaction continues to occur, the growing sodium dendrites can easily pierce the diaphragm, causing a short circuit inside the battery and thermal runaway.

[0004] To solve the above problems, CN118198513A provides a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet, a diaphragm and an electrolyte; the porosity of the diaphragm is 20% to 55%; the electrolyte includes a sodium salt, a solvent and an additive. The electrolyte of the sodium ion battery can optimize the SEI structure, inhibit solvent catalytic dehydrogenation and is intrinsically non-flammable. When paired with a diaphragm with a specific porosity, it can limit the substances and energy transported through the electrolyte. During the use of the battery, hydrogen evolution at the negative electrode and heat generation from crosstalk between the positive and negative electrodes are effectively suppressed, and the severity of energy runaway when the battery fails is also reduced, which can greatly improve the safety of the battery and has good application prospects. CN118800911A provides a battery positive electrode material with added silver powder or silver oxide, which is used to solve the problem that traditional sodium ion battery positive electrode materials still have deficiencies in electrochemical performance and cycle stability, and poor safety. CN117976982A provides a sodium ion battery electrolyte, comprising: sodium salt, organic solvent and functional additives, wherein the functional additives include phosphorus-containing flame retardant additives and fluoroether flame retardant additives. By adding the functional additives into the electrolyte, thermal runaway, combustion, explosion and other accidents of the battery are effectively prevented, so that the sodium ion battery has excellent flame retardant performance, thermal stability and safety performance.

[0005] However, the existing technology has limited effects on optimizing the capacity retention rate and internal resistance of sodium-ion batteries at high temperatures. In order to inhibit the decomposition side reaction of the electrolyte at high temperatures and reduce thermal runaway of the battery, thereby further improving the capacity retention rate of the sodium-ion battery and reducing the internal resistance of the battery, it is of great significance to develop a new type of sodium-ion battery electrolyte. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a non-aqueous electrolyte and a sodium ion battery. The present invention uses additive A and additive B in combination, and the synergistic effect greatly improves the cycle stability of the sodium ion battery at room temperature and high temperature.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising an electrolyte, a non-aqueous organic solvent and an additive, wherein the additive comprises an additive A having a structure shown in Formula 1 and an additive B having a structure shown in Formula 2:

[0009]

[0010] In the present invention, the high temperature and high pressure capability and cycle performance of the sodium ion battery system are effectively improved by using additives A and additive B, so as to achieve the goal of high energy density of the battery cell. The cyano group (-CN) contained in the additive A of the present invention has antioxidant ability, which can inhibit the oxidative decomposition of the electrolyte to a certain extent; the additive B is highly fluorinated, has a high bond energy and thermal stability, is not easy to decompose under high temperature and high pressure environment, and can maintain the integrity of the electrolyte. The two additives work synergistically to form a dense and multi-atomic composite protective layer at the interface between the positive electrode material and the electrolyte of the sodium ion battery, which can "calm" the electrolyte at high temperature, reduce the occurrence of side reactions between metallic sodium and the electrolyte, and thus reduce thermal runaway of the battery, and improve the high temperature capability and cycle performance of the sodium ion battery. In other words, the electrolyte provided by the present invention can improve the antioxidant ability of the electrolyte, reduce the side reactions between metal ions and the electrolyte at high temperature, and improve the high temperature capability and cycle performance of the battery.

[0011] Preferably, based on the mass of the non-aqueous electrolyte being 100%, the mass of the electrolyte is 2-22%, for example, 4%, 6%, 8%, 10%, 13%, 15%, 18% or 20%.

[0012] Preferably, the electrolyte comprises a sodium salt.

[0013] Preferably, the sodium salt includes any one of sodium hexafluorophosphate, sodium perchlorate or sodium bis(trifluoromethylsulfonyl)imide, or a combination of at least two thereof.

[0014] Preferably, based on the mass of the non-aqueous electrolyte being 100%, the mass of the non-aqueous organic solvent is 75-94%, for example, 78%, 80%, 82%, 85%, 88%, 90% or 92%.

[0015] Preferably, the non-aqueous organic solvent comprises a carbonate organic solvent and / or a carboxylate organic solvent.

[0016] Preferably, the carbonate organic solvent includes cyclic carbonate and / or chain carbonate.

[0017] Preferably, the carbonate organic solvent includes cyclic carbonate and chain carbonate.

[0018] Preferably, the volume ratio of the cyclic carbonate to the linear carbonate is 2:8-4:6, such as 2.5:7.5, 3:7 or 3.5:6.5.

[0019] In the present invention, by compounding cyclic carbonate and chain carbonate in a certain ratio as a non-aqueous organic solvent, it is beneficial to improve the overall dielectric constant of the electrolyte, and can ensure that the obtained non-aqueous electrolyte has a low viscosity and good wettability on the surface of the sodium ion battery pole piece, thereby ensuring the good operation of the sodium ion battery.

[0020] Preferably, the cyclic carbonate includes any one of ethylene carbonate, propylene carbonate or butylene carbonate, or a combination of at least two of them.

[0021] Preferably, the linear carbonate includes any one of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or methyl propyl carbonate, or a combination of at least two thereof.

[0022] Preferably, the carboxylate organic solvent includes any one of ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate, methyl acetate, propyl acetate, methyl propionate or γ-butyrolactone, or a combination of at least two thereof.

[0023] Preferably, based on the mass of the non-aqueous electrolyte as 100%, the mass of the additive A is 0.2-4%, for example, 0.3%, 0.5%, 1%, 1.3%, 1.8%, 2.2%, 2.5%, 2.7%, 3%, 3.2%, 3.5% or 3.7%, etc., preferably 0.2-2%, and more preferably 0.4-1.5%.

[0024] Preferably, based on the mass of the non-aqueous electrolyte being 100%, the mass of the additive B is 0.2-2%, for example 0.3%, 0.4%, 0.5%, 0.7%, 0.9%, 1.3%, 1.5% or 1.8%, etc., preferably 0.2-1%, and further preferably 0.4-1%.

[0025] In the present invention, the addition of a specific content of additive B can be well combined with additive A, and the two play a synergistic role, which can significantly reduce the cycle impedance of the sodium ion battery and improve its cycle stability. When the content of additive B is less than 0.2%, it is difficult to form an effective safety interface composite layer; when its content is higher than 2%, the battery impedance is large, affecting the battery performance; based on the mass of the non-aqueous electrolyte as 100%, when the content of additive B is 0.4-1%, the comprehensive performance of the sodium ion battery prepared is better, so that the sodium ion battery not only has a good room temperature capacity retention rate and a high high temperature capacity retention rate, but also reduces the cycle impedance of the sodium ion battery, thereby enhancing the battery cycle performance; but also improves the cycle stability during the battery cycle, and inhibits the battery thermal runaway caused by the violent side reaction between the sodium precipitated at high temperature and the electrolyte.

[0026] Preferably, the mass ratio of the additives A and B is (0.5-3):1, for example, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, 2:1, 2.5:1, etc., and more preferably 1.9:1-2.1:1.

[0027] When the mass ratio of the two is 2:1, the synergistic effect of the two reaches the best, and the sodium ion battery prepared has excellent room temperature capacity retention rate, higher high temperature capacity retention rate and lower high temperature storage gas production volume expansion rate.

[0028] Preferably, the additives also include sodium salt additives.

[0029] In the present invention, the use of the sodium salt additive can effectively improve the capacity retention rate and cycle life of the battery, and can effectively broaden the operating temperature range of the sodium ion battery; at the same time, the sodium salt additive can also form inorganic NaF faster, thereby further reducing the interface impedance.

[0030] Preferably, based on 100% of the mass of the non-aqueous electrolyte, the mass of the sodium salt additive is 0.2-3.0%, such as 0.5%, 1%, 1.5%, 2% or 2.5%.

[0031] Preferably, the sodium salt additive includes any one of sodium difluorosulfonyl imide (NaFSI), sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium difluorophosphate, sodium difluorobisoxalatophosphate or sodium tetraphenylborate, or a combination of at least two thereof.

[0032] Preferably, the additives also include other additives.

[0033] Preferably, based on 100% of the mass of the non-aqueous electrolyte, the mass of the other additives is 0.5-11.6%, for example, 1%, 2%, 3%, 5%, 9% or 11%.

[0034] Preferably, the other additives include any one or a combination of at least two of vinylene carbonate, 1,3-propane sultone (PS), fluoroethylene carbonate (FEC), vinyl sulfite, diethylene sulfate (DTD), methylene methanedisulfonate, vinyl ethylene carbonate, tris(trimethylsilyl) phosphate, and tris(trimethylsilyl) borate (TMSB).

[0035] In a second aspect, the present invention provides a sodium ion battery, comprising a battery cell and an electrolyte, wherein the battery cell comprises a positive electrode, a negative electrode and a separator, wherein the separator is arranged between the positive electrode and the negative electrode, and the electrolyte is the non-aqueous electrolyte as described in the first aspect.

[0036] Preferably, the positive electrode includes a positive electrode active material, a conductive agent and a binder.

[0037] Preferably, the negative electrode includes a negative electrode active material, a conductive agent and a binder.

[0038] Preferably, the material of the diaphragm includes any one of polyethylene, polypropylene or a composite ceramic membrane, or a combination of at least two of them.

[0039] Preferably, the positive electrode active material includes any one of transition metal oxides, polyanion compounds or Prussian blue analogs, or a combination of at least two thereof.

[0040] Preferably, the negative electrode active material includes any one of hard carbon, soft carbon, or a soft carbon-hard carbon composite, or a combination of at least two of them.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] The non-aqueous electrolyte provided by the present invention includes additives A and additives B of specific structures. Through the mutual cooperation of the two, a synergistic effect is exerted, which can not only reduce the cycle impedance of the sodium ion battery at high temperature and improve its cycle life, but also reduce the side reaction of the sodium and electrolyte interface, improve its high temperature cycle stability, and meet the application requirements of sodium ion batteries at high temperatures. The sodium ion battery prepared by the non-aqueous electrolyte provided by the present invention has good stability and safety, and the capacity retention rate under the test conditions of 25°C and 1C is 87-91.1%, the capacity retention rate under the test conditions of 45°C and 1C is 84.1-89.7%, and the DCR of 50% SOC is 95.2-107.2mΩ. DETAILED DESCRIPTION

[0043] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0044] Some of the raw materials used in the following examples:

[0045] Additive A: tris(2-cyanoethyl)phosphate, CAS No. 875826-91-8;

[0046] Additive B: 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, CAS number is 16627-68-2.

[0047] Example 1

[0048] This embodiment provides a non-aqueous electrolyte and a sodium ion battery containing the same. The components and amounts of the non-aqueous electrolyte are shown in Table 1. The preparation method of the sodium ion battery comprises the following steps:

[0049] (1) Preparation of positive electrode sheet: The positive electrode active material NaNi 0.33 Fe 0.33 Mn 0.34 O2, conductive agent acetylene black, and binder polyvinylidene fluoride are fully stirred and mixed in an N-methylpyrrolidone solvent system in a mass ratio of 95:3:2, and then coated on aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0050] (2) Preparation of negative electrode sheet: The negative electrode active material hard carbon, the conductive agent acetylene black, the binder styrene butadiene rubber, and the thickener carbon methyl cellulose sodium are mixed in a deionized water solvent system at a mass ratio of 96:2:1:1, and then coated on aluminum foil, dried, and cold pressed to obtain a negative electrode sheet.

[0051] (3) Preparation of non-aqueous electrolyte: The electrolyte (the filling gas is argon, and the gaseous water content is less than 10 ppm) is prepared in a mikroker glove box. First, the organic solvents ethylene carbonate (EC) and diethyl carbonate (EMC) are uniformly mixed in proportion. Additive A, additive B, sodium salt additive and other additives are added to the uniformly mixed solvent according to the formula in Table 1. Finally, sodium salt NaPF6 is added and mixed until there is no sodium salt residue at the bottom and the electrolyte is clear and not turbid. Thus, an electrolyte with normal chromaticity is obtained. The electrolyte is stored in a -10°C refrigerator. The proportions of each group are shown in Table 1.

[0052] (4) Diaphragm: A polyethylene with a thickness of 9 μm was used as a base film, and a nano-aluminum oxide coating with a thickness of 3 μm was coated on the base film to obtain a diaphragm.

[0053] (5) Cell production: stack the positive electrode sheet, separator, and negative electrode sheet in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and stack the sheets to obtain a bare cell.

[0054] (6) Liquid injection, formation and aging: The bare battery cell is placed in an aluminum-plastic film, baked at 80°C to remove water, and then a non-aqueous electrolyte is injected. The sodium battery is then packaged for the first time, and the surface is cleaned and other processes are completed for the preliminary work, and then placed at room temperature for one day. The formation is carried out by a step-by-step formation method. The first step is a formation current of 0.05C, and a constant current is charged for 2h. The second step is a formation current of 0.1C, and a constant current is charged until the voltage reaches 3.9V. After formation, it is aged at 50°C for one day, cooled to room temperature, and finally sealed to obtain the sodium ion battery.

[0055] Examples 2-20 and Comparative Examples 1-4

[0056] A non-aqueous electrolyte and a sodium ion battery containing the same, wherein the components and dosage of the non-aqueous electrolyte are shown in Table 1, and the difference between the sodium ion battery and Example 1 is that the specific composition of the non-aqueous electrolyte is different, see Table 1 for details. In Table 1, the contents of sodium salt and various additives are all their mass percentages in the electrolyte.

[0057] Table 1

[0058]

[0059]

[0060]

[0061] Battery performance test

[0062] After the battery is assembled, it is placed in a room temperature chamber for 10 hours to allow the electrolyte and the battery electrodes to fully penetrate each other, and then taken for the following tests.

[0063] (1) 50% state of charge (SOC) direct current resistance (DCR) test: adjust the temperature of the incubator to a constant 45°C, let it stand for 10 minutes, charge the battery to 3.9V at a constant current of 0.33C, then keep the voltage constant to 0.05C, let it stand for 10 minutes, and discharge it to 2V at 0.33C to obtain the theoretical capacity of the battery; then charge it to 3.9V at a constant current of 0.33C, then keep the voltage constant to 0.05C, let it stand for 10 minutes, and discharge it at 0.33C to adjust the capacity to 50% SOC. After standing for 1 hour, record the initial voltage V1 of the battery. Then discharge the battery at a current I0 of 4C for 30s, and record the battery voltage V2 after discharge. Calculate the DCR of the battery at 50% SOC according to the following formula: DCR (mΩ) = (V1-V2) / I0

[0064] (2) 25℃ normal temperature cycle test: The battery is charged and discharged at a constant current density of 1C at the rated capacity in a 25℃ constant temperature chamber for 500 cycles. The test voltage range is 2-3.9V and the charge cut-off current is 0.05C. After the test, the capacity retention rate at the 500th week is calculated based on the discharge capacity in the first week.

[0065] The calculation formula for the capacity retention rate of 500 cycles at room temperature is as follows:

[0066] 500th cycle capacity retention rate (%) = (500th room temperature cycle discharge capacity / first discharge capacity) × 100%.

[0067] (3) 45°C high temperature cycle test: In a constant temperature 45°C forced air oven, constant current charge and discharge were performed at a current density of 1C at the rated capacity. The cycle number was 500. The test voltage range was 2V-3.9V and the charge cut-off current was 0.05C. After the test, the capacity retention rate at the 500th week was calculated based on the discharge capacity in the first week.

[0068] The calculation formula for 500-week high-temperature cycle capacity retention rate is as follows:

[0069] 500th cycle capacity retention rate (%) = (500th high-temperature cycle discharge capacity / first discharge capacity) × 100%.

[0070] The test results of Examples 1-20 and Comparative Examples 1-4 are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] The test results show that:

[0075] (1) The electrolyte of the present invention has good room temperature capacity retention rate and high high temperature capacity retention rate by adding additives A and additive B, and can greatly inhibit the increase of DCR of the sodium battery during the cycle. It can be seen from Examples 1-20 that the capacity retention rate of the sodium ion battery assembled by the non-aqueous electrolyte is 87-91.1% under the test conditions of 25°C and 1C, and the capacity retention rate under the test conditions of 45°C and 1C is 84.1-89.7%, and the DCR of 50% SOC is 95.2-107.2mΩ. 。

[0076] (2) By comparing Example 1 with Examples 14-20, it can be seen that when the content of additive A is fixed, the present invention can enable the sodium ion battery to obtain better cycle performance by further limiting the content of additive B. The amount of additive B added should be within an appropriate range. Too much or too little addition will affect the performance of the battery cell. Too much addition will reduce the capacity and cost controllability and reduce practicality. Too little addition will not form a stable electrolyte interface, and will not have a "calming" effect on the high-temperature electrode surface, and will not achieve the expected performance.

[0077] (3) It can be seen from Examples 2-4 that when the mass ratio of additives A to B in the non-aqueous electrolyte provided by the present invention is 2:1, the sodium ion battery can have better high temperature and room temperature cycle performance.

[0078] (4) By comparing Example 1 with Comparative Examples 1-4, it can be seen that the present invention can reduce the cycle impedance of the sodium ion battery and improve its cycle life by adding specific additives A and B to the non-aqueous electrolyte, and can also reduce the storage gas production of the sodium ion battery and improve its cycle performance. That is, the synergistic effect of the two greatly improves the comprehensive performance of the obtained sodium ion battery; while only adding a single additive A or additive B, although it can improve the high temperature cycle performance of the battery and reduce its storage gas production to a certain extent, the single additive A or B cannot exert the synergistic effect of the two, and thus cannot significantly reduce the cycle impedance of the sodium ion battery and improve its cycle performance.

[0079] In summary, the present invention adds additives A and additives B of specific structures to the non-aqueous electrolyte, and through the cooperation of the two, a synergistic effect is exerted, which can not only reduce the cycle impedance of the sodium ion battery at high temperature and improve its cycle life, but also reduce the side reactions at the interface between sodium and the electrolyte, improve its high-temperature cycle stability, and meet the application requirements of sodium ion batteries at high temperatures.

[0080] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that: The non-aqueous electrolyte includes an electrolyte, a non-aqueous organic solvent and an additive, wherein the additive includes an additive A having a structure shown in Formula 1 and an additive B having a structure shown in Formula 2:

2. The non-aqueous electrolyte according to claim 1, characterized in that The mass of the electrolyte is 2-22% based on the mass of the non-aqueous electrolyte being 100%; Preferably, the electrolyte comprises a sodium salt; Preferably, the sodium salt includes any one of sodium hexafluorophosphate, sodium perchlorate or sodium bis(trifluoromethylsulfonyl)imide, or a combination of at least two thereof.

3. The non-aqueous electrolyte according to claim 1 or 2, characterized in that The mass of the non-aqueous organic solvent is 75-94% based on the mass of the non-aqueous electrolyte being 100%; Preferably, the non-aqueous organic solvent comprises a carbonate organic solvent and / or a carboxylate organic solvent; Preferably, the carbonate organic solvent includes cyclic carbonate and / or chain carbonate; Preferably, the cyclic carbonate includes any one of ethylene carbonate, propylene carbonate or butylene carbonate or a combination of at least two thereof; Preferably, the linear carbonate comprises any one of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or methyl propyl carbonate, or a combination of at least two thereof; Preferably, the carboxylate organic solvent includes any one of ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate, methyl acetate, propyl acetate, methyl propionate or γ-butyrolactone, or a combination of at least two thereof.

4. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that: Based on 100% of the mass of the non-aqueous electrolyte, the mass of the additive A is 0.2-4%, preferably 0.2-2%.

5. The non-aqueous electrolyte according to any one of claims 1 to 4, characterized in that: Based on 100% of the mass of the non-aqueous electrolyte, the mass of the additive B is 0.2-2%, preferably 0.2-1%.

6. The non-aqueous electrolyte according to any one of claims 1 to 5, characterized in that: The additives also include sodium salt additives; Preferably, based on the mass of the non-aqueous electrolyte being 100%, the mass of the sodium salt additive is 0.2-3.0%; Preferably, the sodium salt additive includes any one of sodium difluorosulfonyl imide, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium difluorophosphate, sodium difluorobisoxalatophosphate or sodium tetraphenylborate, or a combination of at least two thereof.

7. The non-aqueous electrolyte according to any one of claims 1 to 6, characterized in that: The additives also include other additives; Preferably, based on the mass of the non-aqueous electrolyte being 100%, the mass of the other additives is 0.5-11.6%; Preferably, the other additives include any one or a combination of at least two of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, vinyl sulfite, vinyl sulfate, methylene methanedisulfonate, vinyl ethylene carbonate, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate.

8. A sodium ion battery, characterized in that: The sodium ion battery comprises a battery cell and an electrolyte, wherein the battery cell comprises a positive electrode, a negative electrode and a separator, wherein the separator is arranged between the positive electrode and the negative electrode, and the electrolyte is a non-aqueous electrolyte as described in any one of claims 1 to 7.

9. The sodium ion battery according to claim 8, characterized in that: The positive electrode comprises a positive electrode active material, a conductive agent and a binder; Preferably, the negative electrode comprises a negative electrode active material, a conductive agent and a binder; Preferably, the material of the diaphragm includes any one of polyethylene, polypropylene or a composite ceramic membrane, or a combination of at least two of them.

10. The sodium ion battery according to claim 9, characterized in that: The positive electrode active material includes any one or a combination of at least two of a transition metal oxide, a polyanion compound or a Prussian blue analog; Preferably, the negative electrode active material includes any one of hard carbon, soft carbon, or a soft carbon-hard carbon composite, or a combination of at least two of them.

Images