Non-aqueous electrolyte solution for sodium-ion battery and sodium-ion battery

Abstract

A non-aqueous electrolyte solution for a sodium-ion battery and a sodium-ion battery. The non-aqueous electrolyte solution comprises an electrolyte salt, additives, and solvents. The additives include a phosphorus-containing compound additive and a gas production-inhibiting additive; the molecular formula of the phosphorus-containing compound additive is CxHyO3zPzRm, wherein 1≤z≤4, 4<x+y<40, 3<(x+y) / z<32, m≥0, and R is selected from any one or more of elements Si, F, and N; and the solvents include a cyclic ester solvent and a chain ester solvent. The phosphorus-containing compound additive of a specific general formula and the gas production-inhibiting additive are selected and combined with the cyclic ester solvent and the chain ester solvent, and the content relationship of the additives and the solvents is controlled, so that the system impedance is effectively reduced, and gas production is inhibited, thereby improving the rate performance and cycle performance of sodium-ion batteries.

Description

Sodium ion battery non-aqueous electrolyte and sodium ion battery Technical Field

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

[0002] Rechargeable alkali metal ion batteries are considered to be the most promising and efficient electrochemical energy storage systems. In particular, lithium-ion batteries are considered to be one of the most successful scientific research in the past three decades. However, the cost of raw materials used in lithium batteries (i.e., cobalt, copper, and lithium) has increased rapidly in recent years, resulting in researchers having a stronger interest in sodium-ion batteries, which are cheaper and have more abundant and uniform raw material distribution. These two battery systems have similar working principles, with reversible shuttling of alkali ions between two electrodes through an electrolyte medium that conducts alkali metal ions. Compared with lithium batteries, sodium-ion batteries have wide resources, low costs, and small fluctuations. At the same time, their wide temperature range and high safety performance give them alternative potential. With the continuous advancement of sodium-ion battery technology, sodium-ion batteries have broad growth space in the field of energy storage. However, current sodium-ion batteries generally have problems such as poor battery cycle performance and severe battery gas production, which affect the further development of sodium-ion batteries. Summary of the Invention

[0003] In response to the above technical problems, the present application provides a sodium ion battery non-aqueous electrolyte and a sodium ion battery to overcome the problems of poor cycle performance and severe gas production of sodium ion batteries in the prior art.

[0004] This application adopts the following technical solutions:

[0005] A non-aqueous electrolyte for a sodium ion battery, comprising an electrolyte salt, an additive, and a solvent;

[0006] The additives include phosphorus-containing compound additives and gas generation inhibition additives;

[0007] The molecular formula of the phosphorus-containing compound additive is C x H y O 3z P z R m , wherein: 1≤z≤4, 4<x+y<40, 3<(x+y) / z<32, m≥0, R is selected from any one or more elements of Si, F, and N;

[0008] The solvent includes a cyclic ester solvent and a chain ester solvent;

[0009] The non-aqueous electrolyte satisfies the following conditions:

[0010] 0.7≤a / c+b≤13, 0.2≤a≤2, 0.3≤b≤3, 0.1≤c≤1;

[0011] Wherein: a is the mass percentage of the phosphorus-containing compound additive in the non-aqueous electrolyte, in wt%;

[0012] b is the mass percentage of the gas generation inhibitor additive in the non-aqueous electrolyte, in wt%;

[0013] c is the mass ratio of cyclic ester solvent to chain ester solvent in the non-aqueous electrolyte.

[0014] The non-aqueous electrolyte for sodium ion batteries of the present application is selected from the molecular formula C x H y O 3z P z R m The phosphorus-containing compound additive and the gas production inhibitory additive are added, and the content of the additives is limited. At the same time, the mass ratio of the cyclic ester solvent and the chain ester solvent in the solvent, as well as the content relationship between the three are limited. Through the synergistic and complementary effects between each other, the system impedance is effectively reduced, gas production is inhibited, and the rate performance and cycle performance of the sodium ion battery are improved; preferably, the content relationship of a, b, and c is 1.5≤a / c+b≤7.

[0015] The phosphorus-containing compound additive described in the present application can effectively participate in the negative electrode film formation, improve the stability of the SEI film, significantly inhibit the side reactions caused by the high solubility of the SEI film, effectively improve the circulation and inhibit gas production, and the formed SEI film has the characteristics of low impedance; specifically, the mass percentage of the phosphorus-containing compound additive is 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, and 2wt%; preferably, the mass percentage of the phosphorus-containing compound additive is 0.5-1.5wt%.

[0016] Specifically, as some embodiments of the present application, the phosphorus-containing compound additive includes one or more of the following compounds:

[0017] The use of a gassing inhibitor additive can significantly reduce gassing in the battery system, but it also has the characteristic of high system impedance. By combining a phosphorus-containing compound additive with the gassing inhibitor additive, the system impedance and gassing can be effectively reduced. Specifically, the mass percentage of the gassing inhibitor additive is 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, and 3wt%. Preferably, the mass percentage of the gassing inhibitor additive is 0.5-2.5wt%. The gassing inhibitor additive includes one or more of tris(trimethylsilyl)borate (TMSB), sodium difluorooxalatoborate (NaODFB), vinyl ethylene carbonate (VEC), and 1,6-hexamethylene diisocyanate.

[0018] The present application specifies a mass ratio of cyclic ester solvents to chain ester solvents to suppress decomposition and gassing of the electrolyte at the positive and negative electrodes; preferably, the mass ratio of cyclic ester solvents to chain ester solvents is 0.11 to 0.67. The cyclic ester solvents include one or more of propylene carbonate (PC) and gamma-butyrolactone (GBL); the chain ester solvents include one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl propionate (EP), and polyacrylate (PP).

[0019] Specifically, as some embodiments of the present application, the solvent further comprises one or more of a C3-C5 carbonate solvent, a C2-C6 carboxylate solvent, and a C4-C10 ether solvent;

[0020] More specifically, the carbonate solvent includes a C3-C5 cyclic carbonate or a chain carbonate, the cyclic carbonate is selected from one or more of ethylene carbonate (EC) and butylene carbonate (BC); the chain carbonate is selected from one or more of dimethyl carbonate (DMC) and dipropyl carbonate (DPC);

[0021] The C2-C6 carboxylic acid ester solvent is selected from one or more of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and propyl propionate;

[0022] The ether solvent includes a C4-C10 cyclic ether or chain ether, the cyclic ether is selected from one or more of 1,3-dioxolane, 1,4-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran; the chain ether is selected from one or more of dimethoxymethane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0023] Specifically, as some embodiments of the present application, the electrolyte salt includes one or more of sodium perchlorate (NaClO4), sodium tetrafluoroborate (NaBF4), sodium hexafluorophosphate (NaPF6), sodium trifluoroacetate (CF3COONa), sodium tetraphenylborate (NaB(C6H5)4), sodium trifluoromethanesulfonate (NaSO3CF3), sodium bis(fluorosulfonyl)imide (Na[(FSO2)2N]) or sodium bis(trifluoromethylsulfonyl)imide (Na[(CF3SO2)2N]).

[0024] Specifically, as some embodiments of the present application, the electrolyte additive further includes one or more of cyclic carbonate compounds, fluorinated cyclic carbonate compounds, cyclic sulfonate compounds, cyclic sulfate compounds, phosphate compounds and nitrile compounds;

[0025] Preferably, the cyclic carbonate compound is selected from one or more of vinylene carbonate and methylene carbonate;

[0026] The fluorinated cyclic carbonate compound is selected from one or more of fluoroethylene carbonate and difluoroethylene carbonate;

[0027] The cyclic sulfonate compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, and propenyl-1,3-sultone;

[0028] The cyclic sulfate compound is selected from one or more of vinyl sulfate, 4-methylvinyl sulfate, and propylene sulfate;

[0029] The phosphate compound is selected from one or more of tripropargyl phosphate, trimethyl phosphate, triethyl phosphate, and tris(trimethylsilyl) phosphate;

[0030] The nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0031] The present application also provides a sodium ion battery comprising a positive electrode, a negative electrode and the above-mentioned non-aqueous electrolyte.

[0032] Specifically, as some embodiments of the present application, the negative electrode includes a negative electrode active material, and the negative electrode active material is a carbon material; the carbon material is selected from at least one of hard carbon and soft carbon.

[0033] Specifically, as some embodiments of the present application, the positive electrode includes a positive electrode active material, and the positive electrode active material is selected from one or more of layered transition metal oxides, Prussian compounds, phosphate compounds, and sulfate compounds.

[0034] Specifically, in some embodiments of the present application, the chemical formula of the layered transition metal oxide is Na x M y O z , 0 < x ≤ 1, 0 < y ≤ 1, 1 < z ≤ 2, M can be selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V; the transition metal oxide is NaNi m Fe n Mn p O2 (m + n + p = 1, 0 ≤ m ≤ 1, 0 ≤ n ≤ 1, 0 ≤ p ≤ 1), NaNi m Co n Mn p O2 (m + n + p = 1, 0 ≤ m ≤ 1, 0 ≤ n ≤ 1, 0 ≤ p ≤ 1); more specifically, the layered transition metal oxide is selected from Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, Na 0.44 MnO2, NaNi 0.3 Mn 0.3 Fe 0.4 O2, Na 2 / 3 [Fe 1 / 2 Mn 1 / 2 O2, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na 7 / 9 [Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, NaNi 0.7 Co 0.15 Mn 0.15 O2, or one or more of them.

[0035] In some embodiments of the present application, the molecular formula of the Prussian compound is Na x M[M′(CN)6] y ·zH2O, M is a transition metal, M′ is a transition metal, 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 20; the Prussian compound is Na x Mn[Fe(CN)6] y ·zH2O (0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 20), the Prussian compound is Na x Fe[Fe(CN)6] y ·zH2O (0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 20).

[0036] In some embodiments of the present application, the chemical formula of the phosphate compound is Na3(MO 1- x PO4)2F 1+2x , 0≤x≤1, M is selected from one or more of Al, V, Ge, Fe, and Ga; the chemical formula of the phosphate compound is Na3(VPO4)2F3, Na3(VOPO4)2F.

[0037] In some embodiments of the present application, the chemical formula of the phosphate compound is Na2MPO4F, where M is selected from one or more of Fe and Mn; the chemical formula of the phosphate compound is Na2FePO4F or Na2MnPO4F.

[0038] In some embodiments of the present application, the chemical formula of the sulfate compound is Na2M(SO4)2·2H2O, where M can be selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.

[0039] Specifically, as some embodiments of the present application, the negative electrode further includes a negative electrode conductive agent, and the negative electrode conductive agent is selected from one or more of acetylene black, Super P, graphene, Ketjen black, SFG-6, carbon nanotubes, and graphyne.

[0040] Specifically, as some embodiments of the present application, the negative electrode also includes a negative electrode binder, and the negative electrode binder is selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, thermoplastic resins such as polyethylene and polypropylene; acrylic resin; and one or more of styrene butadiene rubber.

[0041] Specifically, as some embodiments of the present application, the positive electrode further includes a positive electrode conductor and a positive electrode binder. The positive electrode binder and the positive electrode conductor may be the same as the negative electrode binder and the negative electrode conductor, respectively, and are not described in detail here.

[0042] In some embodiments of the present application, the positive electrode or negative electrode is prepared by uniformly mixing an active material, a binder, a conductive agent, and a solvent, coating the mixture on a substrate, and removing the solvent to obtain the positive electrode or negative electrode.

[0043] In some embodiments of the present application, the sodium ion battery further includes a diaphragm, which is located between the positive electrode and the negative electrode.

[0044] The diaphragm can be an existing conventional diaphragm, which can be a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and three-layer PP / PE / PP diaphragms.

[0045] In some embodiments of the present application, the preparation method of the sodium ion battery is a general preparation method for secondary batteries, that is, the positive electrode, the separator, and the negative electrode are combined, and the electrolyte is injected to obtain the sodium ion battery.

[0046] Compared with the prior art, this application achieves the following beneficial effects:

[0047] The sodium ion battery non-aqueous electrolyte of the present application, by selecting a phosphorus-containing compound additive of a specific general formula and a gas production inhibitory additive, and combining it with a cyclic ester solvent and a chain ester solvent, and by controlling the content relationship of each additive and solvent, can significantly inhibit the decomposition and gas production of the electrolyte at the positive and negative electrodes, and improve the stability of the SEI film; the use of the non-aqueous electrolyte of the present application can significantly improve the cycle performance and rate performance of the sodium ion battery, and inhibit battery gas production. DETAILED DESCRIPTION

[0048] The following will be combined with the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] Examples 1-24

[0050] This embodiment provides a sodium ion battery, which includes a positive electrode, a negative electrode and a non-aqueous electrolyte.

[0051] (1) Preparation of non-aqueous electrolyte

[0052] The solvents propylene carbonate (PC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were mixed in a mass ratio of 25:50:25 to obtain an organic solvent, 1 mol / L sodium hexafluorophosphate was added, and based on the total weight of the electrolyte being 100%, phosphorus-containing compound additives and gas generation inhibitor additives of the types and mass percentages shown in Table 1 were added.

[0053] (2) Preparation of positive electrode plate

[0054] The positive electrode active material NaNi was prepared in a mass ratio of 88:9:3. 0.3 Mn 0.3 Fe 0.4 O2, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) are mixed and then dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry; the obtained slurry is evenly coated on both sides of aluminum foil, dried, rolled and vacuum dried, and aluminum lead wires are welded with an ultrasonic welder to obtain a positive electrode plate with a thickness of 120-150μm.

[0055] (3) Preparation of negative electrode plate

[0056] Hard carbon, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in an appropriate amount of deionized water to obtain a negative electrode slurry; the slurry is coated on both sides of a copper foil, dried, rolled and vacuum-dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative electrode plate with a thickness of between 120 and 150 μm.

[0057] (4) Preparation of battery cells

[0058] A three-layer separator with a thickness of 20 μm was placed between the positive plate and the negative plate prepared above. The sandwich structure consisting of the positive plate, the negative plate and the separator was then wound. The wound body was flattened and placed in an aluminum foil packaging bag. The battery was vacuum-baked at 75°C for 48 hours to obtain a battery cell ready for liquid injection.

[0059] (5) Battery injection and formation

[0060] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell, vacuum-sealed, and left to stand for 24 hours.

[0061] Then, conventional charging is carried out according to the following steps: 0.1C constant current charging for 180 minutes, 0.2C constant current charging to 3.8V, secondary vacuum sealing, and then further 0.2C constant current charging to 3.95V, after being placed at room temperature for 24 hours, and then 0.2C constant current discharge to 1.5V to obtain a sodium ion battery.

[0062] Comparative Examples 1-15

[0063] Comparative Examples 1-15 include most of the operating steps of the above examples, except that: based on 100% of the total mass of the electrolyte, the type and content of the phosphorus-containing compound additive and the gas generation inhibitor additive, the mass ratio of the cyclic ester solvent to the chain ester solvent, and the positive electrode active material are as shown in Table 1.

[0064] Table 1 Note: DTD-vinyl sulfate; SN-succinonitrile; PS-1,3-propane sultone; TMSP-trimethylsilyl phosphate.

[0065] Performance Testing

[0066] The sodium ion batteries prepared in Examples 1-24 and Comparative Examples 1-15 were subjected to the following performance tests:

[0067] 4C rate discharge capacity ratio: the ratio of the capacity released by the battery from 3.95-1.5V at a 4C rate to the capacity released by the battery at a 0.2C rate during the activation stage.

[0068] High temperature cycle test: The formed battery was placed at 45°C for 2 hours, charged at a constant current rate of 0.5C to 3.9V, then charged at a constant voltage to a current of 0.03C, and then discharged at a constant current of 1C to 1.5V, for 400 cycles;

[0069] Capacity retention rate (%) = (discharge capacity C2 - charge capacity C1) / charge capacity C1 × 100%;

[0070] Gas production test: Immerse the batteries before and after gas production in a container filled with solvent. The difference in the volume of the overflowed solvent is the volume of gas produced.

[0071] (1) The test results of Examples 1-12 and Comparative Examples 8-15 are shown in Table 2.

[0072] Table 2

[0073] From the test results in Table 2, it can be seen that the sodium ion battery of the present application uses a non-aqueous electrolyte with a molecular formula of C x H y O 3z P z R m The phosphorus-containing compound additive, the gas production inhibition additive, the cyclic ester solvent and the chain ester solvent are used in combination, and by further limiting the content a of the phosphorus-containing compound additive in the non-aqueous electrolyte, the content b of the gas production inhibition additive in the non-aqueous electrolyte, and the mass ratio c of the cyclic ester solvent and the chain ester solvent in the non-aqueous electrolyte to meet 0.7≤a / c+b≤13, 0.2≤a≤2, 0.3≤b≤3, and 0.1≤c≤1, gas production can be effectively inhibited and the rate performance and cycle performance of the sodium ion battery can be improved.

[0074] It can be seen from the test results of Examples 1-12 that when the content a of the phosphorus-containing compound additive in the non-aqueous electrolyte of the sodium ion battery, the content b of the gas production inhibitory additive, and the mass ratio c of the cyclic ester solvent and the chain ester solvent further satisfy 1.5≤a / c+b≤7, 0.5≤a≤1.5, 0.5≤b≤2.5, and 0.11≤c≤0.67, the rate performance and cycle performance of the sodium ion battery are improved, and the gas production inhibition effect is better.

[0075] The test results of Example 1 and Comparative Examples 8-15 demonstrate that when any of the following parameters (a)—the phosphorus-containing compound additive content, b)—in the non-aqueous electrolyte, or the mass ratio (c) of the cyclic ester solvent to the chain ester solvent—do not meet the specified ranges, or when the ratio (a / c+b) is too large or too small—the sodium-ion battery cannot achieve good rate and cycle performance. This demonstrates the strong correlation between the phosphorus-containing compound additive content, b) and the mass ratio (c) of the cyclic ester solvent to the chain ester solvent in improving sodium-ion battery performance.

[0076] (2) The test results of Example 1, Examples 13-15, and Comparative Example 7 are shown in Table 3.

[0077] Table 3

[0078] From the test results of Example 1 and Examples 13-15 in Table 3, it can be seen that the phosphorus-containing compound additives selected in this application only need to meet the "molecular formula is C x H y O 3z P z R m , wherein: 1≤z≤4, 4<x+y<40, 3<(x+y) / z<32, m≥0, R is selected from any one or more elements of Si, F, and N". At the same time, the content a of the phosphorus-containing compound additive, the content b of the gas generation inhibiting additive, and the mass ratio c of the cyclic ester solvent to the chain ester solvent meet the corresponding requirements, all of which can achieve the improvement of the rate performance and cycle performance of the sodium ion battery and inhibit gas generation.

[0079] From the test results of Example 1, Examples 13-15 and Comparative Example 7, it can be seen that the conventional phosphorus-containing compound additive cannot meet the requirement of "molecular formula C x H y O 3z P z R m, wherein: 1≤z≤4, 4<x+y<40, 3<(x+y) / z<32, m≥0, and R is selected from any one or more elements of Si, F, and N". When the conditions are met, the effect of improving the performance of the sodium ion battery is not good, which illustrates the specificity of the selection of the phosphorus-containing compound additive in this application.

[0080] (3) The test results of Example 1 and Examples 16-18 are shown in Table 4.

[0081] Table 4

[0082] The test results of Example 1 and Examples 16-18 in Table 4 show that the sodium-ion batteries of the present application, when using different gassing inhibitor additives, can improve the rate performance and cycle performance of the sodium-ion batteries and suppress gassing when the phosphorus-containing compound additive content a, the gassing inhibitor additive content b, and the mass ratio c of the cyclic ester solvent to the chain ester solvent meet the corresponding requirements. This shows that the sodium-ion batteries of the present application are universally compatible with different gassing inhibitor additives.

[0083] (4) The test results of Example 1 and Examples 19-21 are shown in Table 5.

[0084] Table 5

[0085] The test results of Example 1 and Examples 19-21 in Table 5 show that the sodium-ion batteries of the present application, using different positive electrode active materials, can achieve improved rate performance and cycle performance, while suppressing gas production, when the content a of the phosphorus-containing compound additive in the non-aqueous electrolyte, the content b of the gas production suppressing additive, and the mass ratio c of the cyclic ester solvent to the chain ester solvent meet the corresponding requirements. This demonstrates that the sodium-ion batteries of the present application are universally applicable to different positive electrode active materials.

[0086] (5) The test results of Example 1, Examples 22-24 and Comparative Examples 1-6 are shown in Table 6.

[0087] Table 6

[0088] From the test results of Example 1 and Examples 22-24 in Table 6, it can be seen that the sodium ion battery of the present application, the addition of additives such as vinyl sulfate (DTD), 1,3-propane sultone (PS), and succinonitrile (SN) to the non-aqueous electrolyte can further optimize the rate performance and cycle performance of the sodium ion battery, indicating that the molecular formula is C x H y O 3z P z R m There is a complementary effect between the phosphorus-containing compound additive and other additives.

[0089] It can be seen from the test results of Example 1 and Comparative Examples 1-4 that when the non-aqueous electrolyte does not contain additives or contains only conventional additives, the rate performance, cycle performance and gas production inhibition effect of the sodium ion battery are not good; it can be seen from the test results of Example 1 and Comparative Examples 5-6 that when the additive does not contain a gas production inhibition additive, only a phosphorus-containing compound additive and a conventional additive DTD, and when the additive does not contain a phosphorus-containing compound additive, only a gas production inhibition additive and a conventional additive DTD, the rate performance, cycle performance and gas production inhibition performance of the sodium ion battery are not good; it shows that the sodium ion battery under the system of the present application can significantly improve the cycle performance and rate performance of the sodium ion battery and inhibit battery gas production through the interaction between specific additives in the non-aqueous electrolyte.

[0090] The present application is further described above with the help of specific embodiments, but it should be understood that the specific description here should not be construed as limiting the essence and scope of the present application. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of this application.

Claims

1. A non-aqueous electrolyte for sodium ion batteries, comprising an electrolyte salt, an additive and a solvent, characterized in that: The additives include phosphorus-containing compound additives and gas generation inhibition additives; The molecular formula of the phosphorus-containing compound additive is C x H y O 3z P z R m , wherein: 1≤z≤4, 4<x+y<40, 3<(x+y) / z<32, m≥0, R is selected from any one or more elements of Si, F, and N; The solvent includes a cyclic ester solvent and a chain ester solvent; The non-aqueous electrolyte satisfies the following conditions: 0.7≤a / c+b≤13, 0.2≤a≤2, 0.3≤b≤3, 0.1≤c≤1; Wherein: a is the mass percentage of the phosphorus-containing compound additive in the non-aqueous electrolyte, in wt%; b is the mass percentage of the gas generation inhibitor additive in the non-aqueous electrolyte, in wt%; c is the mass ratio of cyclic ester solvent to chain ester solvent in the non-aqueous electrolyte.

2. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The non-aqueous electrolyte satisfies the following condition: 1.5≤a / c+b≤7.

3. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The mass percentage of the phosphorus compound additive in the non-aqueous electrolyte is 0.5-1.5 wt%.

4. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The mass percentage of the gas generation inhibiting additive in the non-aqueous electrolyte is 0.5-2.5 wt %.

5. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The mass ratio of the cyclic ester solvent to the chain ester solvent in the non-aqueous electrolyte is 0.11 to 0.

67.

6. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The phosphorus-containing compound additive includes one or more of the following compounds:

7. The non-aqueous electrolyte for sodium ion batteries according to claim 1, characterized in that: The gas generation inhibiting additive includes one or more of tris(trimethylsilyl)borate, sodium difluorooxalatoborate, vinyl ethylene carbonate, and hexamethylene diisocyanate.

8. The non-aqueous electrolyte for sodium ion batteries according to claim 1, wherein The cyclic ester solvent includes one or more of propylene carbonate and γ-butyrolactone; the chain ester solvent includes one or more of ethyl methyl carbonate, diethyl carbonate, ethyl propionate, and polyacrylate.

9. The non-aqueous electrolyte for sodium ion batteries according to claim 1, characterized in that: The electrolyte salt includes one or more of sodium perchlorate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium trifluoroacetate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, or sodium bis(trifluoromethylsulfonyl)imide.

10. A sodium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the non-aqueous electrolyte according to claim 1.

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