Sodium-ion battery and electrical device

Abstract

The present disclose relates to the technical field of sodium ion batteries, and in particular to a sodium-ion battery and an electrical device. The sodium-ion battery comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises an active material layer, and the active material layer mainly consists of a positive electrode active material, a conductive agent, and a binder; the mass of the conductive agent accounts for A% of the total mass of the active material layer, and the mass of the binder accounts for B% of the total mass of the active material layer; the electrolyte comprises solvents and a sodium salt; the relative dielectric constant of the solvents is ε, n types of solvents are comprised, n≥2, and the ratio of the mass of each type of solvent to the total mass of the solvents is M; the molar concentration of the sodium salt in the electrolyte is N; A, B, ε, M, and N satisfy: 4.3≤A / B+C≤12.9, and formula (I). The sodium-ion battery provided in the present disclosure has high safety and good cycle stability.

Description

Sodium ion battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to application number 202311813714X, filed with the Patent Office of China on December 27, 2023, entitled “A Sodium Ion Battery and Electrical Equipment,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery and an electrical device. Background Art

[0004] Compared to lithium-ion batteries, sodium-ion batteries, with their higher resource abundance, are expected to enter commercialization as a complementary technology to lithium-ion batteries, filling the market niche in A00-class power and energy storage. These target applications require sodium-ion batteries to possess certain safety characteristics, ensuring normal operation throughout their lifecycle without the risk of fire.

[0005] However, current high-energy-density sodium-ion battery electrolyte formulations are not flame-retardant and perform poorly in stringent testing standards, such as needle puncture and thermal runaway, posing potential safety risks in actual use.

[0006] Therefore, it is of great significance to provide a highly safe sodium-ion battery.

[0007] In view of this, the present disclosure is proposed. Summary of the Invention

[0008] The first purpose of the present disclosure is to provide a sodium ion battery. By regulating parameters such as the amount of sodium salt in the electrolyte, the relative dielectric constant and amount of the solvent, the amount of conductive agent and the amount of binder in the positive electrode sheet, the battery safety problems caused by factors such as the Faraday reaction and oxygen release at high temperatures of the positive electrode can be suppressed, the energy release intensity caused by internal micro-short circuits when the battery fails can be reduced, and jet fires can be better suppressed, thereby preventing the occurrence of fires and having high safety.

[0009] A second objective of the present disclosure is to provide an electrical device.

[0010] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions are adopted:

[0011] The present disclosure first provides a sodium ion battery, comprising a positive electrode sheet and an electrolyte;

[0012] The positive electrode sheet includes an active material layer, which is mainly composed of a positive electrode active material, a conductive agent, and a binder; the mass of the conductive agent accounts for a percentage of the total mass of the active material layer is A, and the mass of the binder accounts for a percentage of the total mass of the active material layer is B;

[0013] The electrolyte comprises a solvent and a sodium salt; the relative dielectric constant of the solvent is ε, the solvent comprises n types, wherein n ≥ 2, the ratio of the mass of each solvent to the total mass of the solvent is M; the molar concentration of the sodium salt in the electrolyte is N;

[0014] A, B, ε, M, and N satisfy the following relationship:

[0015] 4.3≤A / B+C≤12.9, and

[0016] Furthermore, the A is 0.6% to 3%.

[0017] Furthermore, the B is 1.0% to 3.1%.

[0018] Furthermore, the C is 4.1 to 10.9.

[0019] Furthermore, the ε is 2-100.

[0020] Furthermore, the M is 0-1.

[0021] Furthermore, the N is 0.1 to 1.5 mol / L.

[0022] Furthermore, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes and graphene;

[0023] Furthermore, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, polyethylene oxide, sodium carboxymethyl cellulose and alginate.

[0024] Furthermore, the solvent includes at least one of a cyclic ester solvent and a chain ester solvent.

[0025] Furthermore, the solvent comprises a cyclic ester solvent and a chain ester solvent in a mass ratio of x:(100-x), wherein x=10-90.

[0026] Furthermore, the cyclic ester solvent includes at least one of ethylene carbonate, propylene carbonate and γ-butyrolactone.

[0027] Furthermore, the chain ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate.

[0028] Furthermore, the sodium salt includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide and sodium bis(trifluoromethanesulfonyl)imide.

[0029] Furthermore, the gas production of the sodium ion battery after 500 cycles at 45° C. is ≤20 mL / Ah.

[0030] Furthermore, the capacity retention rate of the sodium ion battery after 500 cycles at 45° C. is ≥75%.

[0031] Furthermore, the impedance growth rate of the sodium ion battery after 500 cycles at 45° C. is ≤70%.

[0032] The present disclosure further provides an electrical device comprising the sodium ion battery.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The sodium ion battery provided by the present disclosure can suppress battery safety issues caused by factors such as the Faradaic reaction and oxygen release at high temperatures of the positive electrode, reduce the intensity of energy release caused by internal micro-short circuits when the battery fails, effectively suppress jet fires, and prevent the occurrence of fires. It has high safety and good cycle stability and reversible capacity.

[0035] (2) The sodium ion battery provided by the present disclosure has a high capacity retention rate and a low impedance growth rate.

[0036] (3) The sodium ion battery provided by the present disclosure is not prone to sodium precipitation and large-scale gas production. DETAILED DESCRIPTION

[0037] The technical solutions of the present disclosure will be clearly and completely described below in conjunction with specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the present disclosure, rather than all of the embodiments, and are only used to illustrate the present disclosure, and should not be considered as limiting the scope of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present disclosure. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0038] Unless otherwise specified, in this disclosure, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," "third," and "fourth" serve only as non-exhaustive enumerations and descriptions and should not constitute closed-ended limitations on quantity.

[0039] Unless otherwise specified, the terms "include" and "comprising" mentioned in this disclosure may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0040] Unless otherwise specified, in this disclosure, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more of the listed items.

[0041] In a first aspect, the present disclosure provides a sodium ion battery with high safety and stability, which includes a positive electrode sheet and an electrolyte.

[0042] The positive electrode sheet includes an active material layer, which is primarily composed of a positive electrode active material, a conductive agent, and a binder. The mass of the conductive agent as a percentage of the total mass of the active material layer is A, i.e., A = mass of the conductive agent / total mass of the active material layer × 100%. The mass of the binder as a percentage of the total mass of the active material layer is B, i.e., B = mass of the binder / total mass of the active material layer × 100%.

[0043] The electrolyte includes a solvent and a sodium salt. The relative dielectric constant of the solvent is ε, the solvents include n types, where n ≥ 2, and the ratio of the mass of each solvent to the total mass of the solvents is M, i.e., M = the mass of the solvent / the total mass of the solvents. The molar concentration of the sodium salt in the electrolyte is N.

[0044] A, B, ε, M, and N satisfy the following relationship:

[0045] 4.3≤A / B+C≤12.9, and

[0046] The constraint values ​​in the above relationship are all parameters inside the battery that affect the ionic conductivity and electronic conductivity. By regulating the above parameters, the performance of the battery can be improved.

[0047] Here, ε is unitless. The unit of N is mol / L. The unit of A is %. The unit of B is %.

[0048] Among them, the value of A / B+C is 4.3 to 12.9, including but not limited to any one of 4.3, 4.5, 4.8, 5.0, 5.3, 5.5, 5.8, 6.0, 6.2, 6.5, 6.7, 7.0, 7.3, 7.5, 7.8, 8.0, 8.2, 8.4, 8.6, 7, 7.5, 8, 8.5, 9, 10, 11, 12, 12.9 or the range between any two of them.

[0049] It is understood that n in the above relationship is the number of solvent types. For example, if the electrolyte includes two solvents, then n=2; if the electrolyte includes three solvents, then n=3.

[0050] It can be understood that when the electrolyte includes three solvents, the relative dielectric constant of the first solvent is ε1, the relative dielectric constant of the second solvent is ε2, and the relative dielectric constant of the third solvent is ε3. The ratio of the mass of the first solvent to the total mass of the solvent is M1, the ratio of the mass of the second solvent to the total mass of the solvent is M2, and the ratio of the mass of the third solvent to the total mass of the solvent is M3. In this case, C = ε1M1 / 4 + ε2M2 / 4 + ε3M3 / 4 + N.

[0051] The sodium ion battery provided by the present disclosure controls the amount of sodium salt in the electrolyte, the relative dielectric constant and amount of the solvent, and regulates the amount of conductive agent and binder in the positive electrode sheet. These multiple factors work together to suppress battery safety issues caused by factors such as Faraday reaction and oxygen release at high temperatures at the positive electrode, reduce the intensity of energy release from internal micro-short circuits when the battery fails, effectively suppress the generation of jet fires, and thus prevent the occurrence of fires, ensuring that the secondary battery has good safety performance during actual use.

[0052] At the same time, the electrical properties of the sodium ion battery provided by the present invention, such as cycle stability and storage stability in a steady state, are not affected. During use, it has a good capacity retention rate and a low impedance growth rate, and does not experience sodium precipitation and large-scale gas production.

[0053] Furthermore, the sodium ion battery provided by the present disclosure is compatible with existing sodium ion battery production processes and has a low production cost.

[0054] In order to further comprehensively consider the cycle performance and impedance growth rate of sodium-ion batteries and avoid phenomena such as sodium precipitation and gas production, the present disclosure optimizes parameters such as A, B, C, ε, M, and N.

[0055] In some specific embodiments, A is 0.6% to 3%, including but not limited to 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.6%, 2%, 2.3%, 2.5%, 2.8%, 3%, any one of the point values ​​or any range value between two of them.

[0056] In some specific embodiments, the A is 0.8% to 1.2%.

[0057] In some specific embodiments, B is 1.0% to 3.1%, including but not limited to any one of 1.0%, 1.2%, 1.4%, 1.5%, 1.8%, 2.0%, 2.2%, 2.3%, 2.5%, 2.8%, 3%, 3.1% or a range between any two of them.

[0058] In some specific embodiments, the B is 1.3% to 1.8%.

[0059] In some specific embodiments, C is 4.1-10.9, including but not limited to any one of 4.1, 4.3, 4.5, 4.8, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 7.9, 8, 8.3, 8.5, 9, 9.5, 10, 10.9 or a range between any two of them.

[0060] In some specific embodiments, the C is 4.5 to 7.9.

[0061] In some specific embodiments, the ε is 2 to 100, including but not limited to any one of 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or a range between any two of them.

[0062] In some specific embodiments, M is 0-1, including but not limited to any one of 0, 0.0001, 0.001, 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range of values ​​between any two of them.

[0063] In some specific embodiments, N is 0.1 to 1.5 mol / L, including but not limited to any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, and 1.5 mol / L, or a range between any two of them.

[0064] In some specific embodiments, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, and graphene.

[0065] In some specific embodiments, the conductive carbon black includes at least one of conductive carbon black SP (super p), acetylene black (AB) and Ketjen black (KB).

[0066] In some specific embodiments, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), polyethylene oxide (PEO), sodium carboxymethyl cellulose (CMC) and alginate.

[0067] In some specific embodiments, the solvent includes at least one of a cyclic ester solvent and a chain ester solvent.

[0068] Generally speaking, cyclic ester solvents have high relative dielectric constants and high viscosities.

[0069] Chain ester solvents have low relative dielectric constant and low viscosity.

[0070] In some specific embodiments, in order to adjust the relative dielectric constant ε of the solvent and thus control the C value, the solvent includes a cyclic ester solvent and a chain ester solvent in a mass ratio of x:(100-x), wherein x=10-90.

[0071] As an example, the mass ratio of the cyclic ester solvent to the chain ester solvent is 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20 or 90:10.

[0072] Controlling the mass ratio of the cyclic ester solvent to the linear ester solvent within the above range helps ensure the kinetic performance of sodium-ion batteries during normal use, prevents sodium precipitation, and optimizes their impedance performance. It also avoids battery gassing problems caused by excessive concentration of ethylene carbonate in the cyclic ester solvent due to the singlet oxygen release mechanism.

[0073] In some specific embodiments, the cyclic ester solvent includes at least one of ethylene carbonate, propylene carbonate and γ-butyrolactone.

[0074] In some specific embodiments, the chain ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate.

[0075] In some specific embodiments, the sodium salt includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0076] In some specific embodiments, the gas production of the sodium ion battery after 500 cycles at 0.5C / 1C and 45°C is ≤20mL / Ah, including but not limited to 20mL / Ah, 15mL / Ah, 10mL / Ah, 5mL / Ah, 4mL / Ah, 3mL / Ah, 2mL / Ah, 1mL / Ah, 0.5mL / Ah, and any one of 0mL / Ah or a range between any two of them.

[0077] In some specific embodiments, the capacity retention rate of the sodium ion battery after 500 cycles at 0.5C / 1C and 45°C is ≥75%, including but not limited to any one of 75%, 77%, 80%, 83%, 85%, 88%, 90%, 91%, 92%, 93%, and 95%, or a range between any two of the values.

[0078] In some specific embodiments, the sodium ion battery has an impedance growth rate of ≤70% after 500 cycles at 0.5C / 1C and 45°C, including but not limited to 70%, 60%, 50%, 40%, 39%, 38%, 37%, 36%, 35%, 33%, 30%, 28%, 26%, 25%, 23%, 20%, 15%, 10%, or any one of the point values ​​or the range between any two of them.

[0079] In some specific embodiments, the capacity retention rate is tested as follows: at 45°C, the battery is charged at a constant current and constant voltage of 0.5C to 3.95V, with a cutoff current of 0.05C, and then discharged at a constant current of 1C to 2.0V. After 500 charge / discharge cycles, the capacity retention rate at the 500th cycle is calculated.

[0080] In some specific embodiments, the sodium ion battery further includes a negative electrode plate.

[0081] In some specific embodiments, the sodium ion battery further comprises a separator.

[0082] In some specific embodiments, the electrolyte further includes organic additives and / or salt additives.

[0083] The organic additives include any organic materials commonly used in the art.

[0084] As an example, the organic additive includes at least one of a carbonate additive, a silicon-containing additive, and a sulfur-containing additive; the carbonate additive includes at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC); the silicon-containing additive includes at least one of tris(trimethylsilyl)phosphite (TMSPi), tris(trimethylsilyl)phosphate (TMSP), and tris(trimethylsilyl)borate (TMSB); the sulfur-containing additive includes at least one of 1,3-propane sultone (PS), 1,3-propylene sultone (PST), ethylene sulfate (D At least one of, but not limited to, TD), propylene sulfate (PCS), methylene methanedisulfonate (MMDS), 4-methylethylene sulfate (MeDTD), 4-fluoroethylene sulfate (FDTD), 4,4'-bisulfate (BiDTD), spirobisDTD (1,3,6,8-tetraoxy-2,7-disulfide-spiro[4.4]nonane-2,2,7,7-tetraoxide), pyrrolidine DTD (GS), 4,5-dimethylethylene sulfate (DMeDTD), and 1,2-cyclopentadiene sulfate (CPS). The use of the above-mentioned organic additives can regulate the main composition of the SEI film and rationally distribute the organic and inorganic components of the SEI, thereby ensuring low impedance and high cycle stability of the SEI main body.

[0085] As an example, the mass fraction of the organic additive in the electrolyte can be 0.1% to 5%, such as 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, but is not limited thereto.

[0086] The salt-type additives include any salt materials commonly used in the art.

[0087] As an example, the salt type additive includes at least one of sodium difluorooxalatoborate (NaDFOB), sodium difluorophosphate (NaDFP), and sodium difluorobis(oxalatophosphate) (NaDFOP), but is not limited thereto.

[0088] As an example, the mass fraction of the salt additive in the electrolyte can be 0.1% to 2%, such as 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8% or 2%, but is not limited thereto.

[0089] In some specific embodiments, the positive electrode sheet includes a current collector, and the active material layer is disposed on the current collector, wherein the active material layer mainly consists of a positive electrode active material, a conductive agent, and a binder.

[0090] The positive electrode active material includes any positive electrode material commonly used in the art.

[0091] As an example, the positive electrode material includes at least one of a layered metal oxide, a polyanion compound, a Prussian compound, a phosphate compound, and a sulfate compound, but is not limited thereto.

[0092] In a second aspect, the present disclosure provides an electrical device comprising the above-mentioned sodium ion battery.

[0093] Among them, electrical equipment includes any equipment, device or system containing the above-mentioned sodium ion battery, such as transportation vehicles, energy storage systems, electronic products, medical equipment and office equipment, but is not limited thereto.

[0094] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0095] Example 1

[0096] The sodium ion battery provided in this embodiment includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The preparation method of the sodium ion battery includes the following steps:

[0097] (1) Preparation of positive electrode sheet: The positive electrode active material 1-AB, the conductive agent Super PA and the binder PVDF B are mixed and uniformly dispersed in the solvent N-methylpyrrolidone according to the mass percentage, wherein the values ​​of A and B are shown in Table 1 (A = 0.6%, B = 1.4%) to obtain a positive electrode slurry, and then the positive electrode slurry is coated on the positive electrode current collector aluminum foil, dried, and pressed to obtain a positive electrode sheet. The positive electrode sheet includes a current collector and an active material layer provided on the current collector, and the active material layer is composed of the positive electrode active material Na 0.833 Cu 0.167 Fe 0.333 Mn 0.5 The active material layer is composed of O2, Super P and PVDF, wherein the mass of Super P accounts for 0.6% of the total mass of the active material layer, and the mass of PVDF accounts for 1.4% of the total mass of the active material layer.

[0098] (2) Preparation of negative electrode sheet: Hard carbon, Super P, CMC and SBR are uniformly dispersed in solvent N-methylpyrrolidone in a mass ratio of 94.3:1.4:1.6:2.7 to obtain negative electrode slurry, and then the negative electrode slurry is coated on the negative electrode current collector aluminum foil, dried, and pressed to obtain the negative electrode sheet.

[0099] (3) Preparation of electrolyte: The solvent, sodium salt and organic additive are mixed evenly to obtain an electrolyte. The solvent is propylene carbonate (PC) and diethyl carbonate (DEC) in a mass ratio of 40:60 (i.e., n=2, M1=0.4, M2=0.6), wherein the relative dielectric constant of PC is ε1=69, and the relative dielectric constant of DEC is ε2=2.8. The sodium salt is sodium hexafluorophosphate (NaPF6), and the molar concentration of the sodium salt in the electrolyte is 0.5 mol / L. The organic additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC), and the mass fraction of VC in the electrolyte is 1%, and the mass fraction of FEC in the electrolyte is 3%.

[0100] (4) Assembling a sodium ion battery: stacking the positive electrode sheet, the separator, and the negative electrode sheet in order, with the separator positioned between the positive electrode sheet and the negative electrode sheet to serve as an isolation layer, and then winding to obtain a bare cell. The bare cell is placed in an aluminum-plastic film outer package, and the electrolyte is injected, packaged, and formed to obtain a sodium ion battery.

[0101] The key parameters in this embodiment are shown in Table 1.

[0102] Example 2 to Example 7

[0103] The preparation methods of the sodium ion batteries provided in Examples 2 to 7 are substantially the same as those in Example 1, wherein the key parameters of Examples 2 to 7 are shown in Table 1 (the remaining parameters are the same as those in Example 1).

[0104] Example 8

[0105] The preparation method of the sodium ion battery provided in this embodiment is basically the same as that in Example 1, except that in step (1), the conductive agent Super P is replaced by an equal mass of carbon nanotubes, and the binder PVDF is replaced by an equal mass of SBR.

[0106] Example 9

[0107] The preparation method of the sodium ion battery provided in this embodiment is basically the same as that in Example 1, except that in step (3), sodium hexafluorophosphate (NaPF6) is replaced by sodium bis(fluorosulfonyl)imide, and the molar concentration of the sodium salt in the electrolyte is 0.5 mol / L.

[0108] Example 10

[0109] The preparation method of the sodium ion battery provided in this embodiment is basically the same as that in Example 1, except that in step (3), the solvent is replaced with EC and EMC in a mass ratio of 40:60.

[0110] Example 11 to Example 14

[0111] The preparation methods of the sodium ion batteries provided in Examples 11 to 14 are substantially the same as those in Example 1, wherein the key parameters of Examples 11 to 14 are shown in Table 1 (the remaining parameters are the same as those in Example 1).

[0112] Comparative Examples 1 to 3

[0113] The preparation methods of the sodium ion batteries provided in Comparative Examples 1 to 3 are substantially the same as those in Example 1, wherein the key parameters of Comparative Examples 1 to 3 are shown in Table 1 (the remaining parameters are the same as in Example 1).

[0114] Table 1 Key parameters in each embodiment and each comparative example

[0115] Experimental example

[0116] Electrochemical tests were performed on the sodium ion batteries prepared in the above embodiments and comparative examples, and the results are shown in Table 2.

[0117] The capacity retention rate is tested as follows: at 45°C, the battery is charged at 0.5C constant current and constant voltage to 3.95V, with a cutoff current of 0.05C, and then discharged at 1C constant current to 2.0V. After 500 charge / discharge cycles, the capacity retention rate at the 500th cycle is calculated. The calculation formula is: 500th cycle capacity retention rate = 500th cycle discharge capacity / first cycle discharge capacity × 100%.

[0118] The test method for gas production is: drainage method.

[0119] The test method for sodium precipitation is: disassemble the battery in a dry room with a dew point of about -40℃ and observe the negative electrode with the naked eye.

[0120] The initial impedance and impedance growth rate are measured as follows: fully charge the battery at room temperature, connect the positive and negative electrodes to an AC impedance meter, and read the impedance growth rate. Impedance growth rate (%) = (500-cycle ACR - initial ACR) / initial ACR × 100%.

[0121] The needle penetration test method is as follows: After the cylindrical battery is fixed in a horizontal position, a tungsten steel needle is inserted vertically into the center of the cylindrical battery and penetrates. The test is considered passed if there is no fire or explosion. The steel needle parameters are as follows: diameter 5mm; needle insertion speed 25mm / s.

[0122] Table 2 Electrochemical performance of various sodium ion batteries

[0123] From Table 2, we can see that when the relationship is satisfied When 4.3≤A / B+C≤12.9, the sodium-ion battery has a higher capacity retention rate and a lower impedance growth rate, and there will be no sodium precipitation and large-scale gas production, and the safety performance is good.

[0124] Comparative Examples 1 to 3 do not satisfy the relationship 4.3≤A / B+C≤12.9, resulting in a decrease in capacity retention or an increase in impedance growth rate. In addition, in Comparative Example 2, sodium precipitation occurs due to the lack of a cyclic ester solvent.

[0125] In addition, by comparing Examples 11 to 14 with Example 1, it can be seen that, under the premise of satisfying the relationship 4.3≤A / B+C≤12.9, parameters such as N, A, and B can further improve the capacity retention rate of the sodium ion battery or further reduce the impedance growth rate within the preferred range.

[0126] Although the present disclosure has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features therein may be replaced by equivalents, without departing from the spirit and scope of the present disclosure. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure. Therefore, this means that all such replacements and modifications within the scope of the present disclosure are included in the appended claims. Industrial Applicability

[0127] The sodium-ion battery provided by the present disclosure can suppress battery safety issues caused by factors such as the Faradaic reaction and oxygen release at high temperatures at the positive electrode, reduce the intensity of energy release caused by internal micro-short circuits when the battery fails, effectively suppress jet fires, and prevent the occurrence of fires. It has high safety, and the sodium-ion battery has good cycle stability and reversible capacity, and has very good industrial application prospects.

Claims

1. A sodium-ion battery, characterized in that, It includes a positive electrode plate and an electrolyte; The positive electrode plate includes an active material layer, and the active material layer is mainly composed of a positive electrode active material, a conductive agent, and a binder; the percentage of the mass of the conductive agent in the total mass of the active material layer is A, and the percentage of the mass of the binder in the total mass of the active material layer is B; The electrolyte includes a solvent and a sodium salt; the relative dielectric constant of the solvent is ε, the solvent includes n types, where n≥2, and the mass ratio of each solvent in the total mass of the solvent is M; the molar concentration of the sodium salt in the electrolyte is N; The A, the B, the ε, the M, and the N satisfy the following relational expression: 4.3 ≤ A / B + C ≤ 12.9, and 2. The sodium ion battery according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) A is 0.6% to 3%; (2) B is 1.0% to 3.1%; (3) C is 4.1 to 10.

9.

3. The sodium-ion battery according to claim 1 or 2, wherein, It includes at least one of the following features (1) to (3): (1) ε is 2 to 100; (2) M is 0 to 1; (3) N is 0.1 to 1.5 mol / L.

4. The sodium ion battery according to any one of claims 1-3, characterized in that, It includes at least one of the following features (1) to (2): (1) The conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, and graphene; (2) The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, polyethylene oxide, sodium carboxymethyl cellulose, and alginate.

5. The sodium-ion battery according to any one of claims 1-4, characterized in that, The solvent includes at least one of a cyclic ester solvent and a chain ester solvent.

6. The sodium ion battery according to claim 5, wherein The solvent includes a cyclic ester solvent and a chain ester solvent with a mass ratio of x:(100 - x), where x = 10 to 90.

7. The sodium ion battery according to claim 5 or 6, characterized in that, The cyclic ester solvent includes at least one of ethylene carbonate, propylene carbonate, and γ-butyrolactone.

8. The sodium ion battery according to any one of claims 5-7, characterized in that, The chain ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

9. The sodium-ion battery according to any one of claims 1-8, characterized in that, The sodium salt includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

10. The sodium ion battery according to any one of claims 1-9, characterized in that, It includes at least one of the following features (1) to (3): (1) The gas generation amount of the sodium-ion battery after 500 cycles at 45°C ≤ 20 mL / Ah; (2) The capacity retention rate of the sodium-ion battery after 500 cycles at 45°C ≥ 75%; (3) The impedance growth rate of the sodium-ion battery after 500 cycles at 45°C ≤ 70%.

11. An electrical device, characterized in that, It includes the sodium-ion battery according to any one of claims 1 to 10.

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