A sodium ion battery non-aqueous electrolyte and a sodium ion battery

Abstract

The present invention relates to the field of electrochemical technology, and in particular to a sodium ion battery non-aqueous electrolyte and a sodium ion battery. The non-aqueous electrolyte of the present invention comprises an electrolyte salt, an additive and a solvent; the additive comprises a phosphorus-containing compound additive and a gas generation inhibiting additive; 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 0.7≤a / c+b≤13, 0.2≤a≤2, 0.3≤b≤3, and 0.1≤c≤1. The present invention selects a molecular formula of C x H y O 3z P z R m Phosphorus-containing compound additives and gas production inhibition additives are added, and the mass ratio of cyclic ester solvents and chain ester solvents in the solvent, as well as the content relationship between the three are limited. Through their synergistic and complementary effects, the system impedance is effectively reduced, gas production is inhibited, and the rate performance and cycle performance of sodium-ion batteries are improved.

Description

Technical Field

[0001] The present invention 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, leading researchers to have 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, and the reversible shuttling of alkali ions between two electrodes is carried out 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, they have wide temperature ranges and high safety performance, which 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 view of the above technical problems, the present invention 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] The present invention 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 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 meets 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 compound additive in the non-aqueous electrolyte, in wt%;

[0012] b is the mass percentage of the gas generation inhibiting 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 sodium ion battery non-aqueous electrolyte of the present invention is selected from the molecular formula C x H y O 3z P z R m A phosphorus-containing compound additive and a gas production inhibiting additive are added, and the content of the additive 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 of the present invention can effectively participate in the negative electrode film formation, improve the stability of the SEI film, significantly inhibit the side reaction caused by the high solubility of the SEI film, effectively improve the circulation and inhibit the 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%, 2wt%; preferably, the mass percentage of the phosphorus-containing compound additive is 0.5-1.5wt%.

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

[0017]

[0018] C7H 19 O3PSi

[0019] Compound 4.

[0020] The use of gas production inhibitor additives can significantly reduce the gas production of the battery system, but has the characteristics of high system impedance; by combining the phosphorus compound additive and the gas production inhibitor additive, the system impedance and gas production can be effectively reduced; specifically, the mass percentage of the gas production inhibitor additive is 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%; preferably, the mass percentage of the gas production inhibitor additive is 0.5-2.5wt%. The gas production inhibitor additive includes one or more of tris(trimethylsilyl)borate (TMSB), sodium difluorooxalatoborate (NaODFB), vinyl ethylene carbonate (VEC), and 1,6-hexamethylene diisocyanate.

[0021] The present invention limits the mass ratio of cyclic ester solvents to chain ester solvents, which can inhibit the decomposition and gas generation of 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 γ-butyrolactone (GBL); the chain ester solvents include one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl propionate (EP), and polyacrylate (PP).

[0022] Specifically, as some embodiments of the present invention, the solvent further comprises one or more of C3-C5 carbonate solvents, C2-C6 carboxylate solvents, and C4-C10 ether solvents;

[0023] More specifically, the carbonate solvent includes C3-C5 cyclic carbonate or 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);

[0024] 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;

[0025] The ether solvent includes a C4-C10 cyclic ether or a chain ether, wherein 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.

[0026] Specifically, as some embodiments of the present invention, 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 trifluoromethylsulfonate (NaSO3CF3), sodium bis(fluorosulfonyl)imide (Na[(FSO2)2N]) or sodium bis(trifluoromethylsulfonyl)imide (Na[(CF3SO2)2N]).

[0027] Specifically, as some embodiments of the present invention, 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;

[0028] Preferably, the cyclic carbonate compound is selected from one or more of vinylene carbonate and methylene carbonate;

[0029] The fluorinated cyclic carbonate compound is selected from one or more of fluoroethylene carbonate and difluoroethylene carbonate;

[0030] The cyclic sulfonate compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, and propenyl-1,3-sultone;

[0031] The cyclic sulfate ester compound is selected from one or more of vinyl sulfate, 4-methyl vinyl sulfate, and propylene sulfate;

[0032] The phosphate compound is selected from one or more of tripropargyl phosphate, trimethyl phosphate, triethyl phosphate, and tris(trimethylsilyl) phosphate;

[0033] The nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebaconitrile.

[0034] The present invention also provides a sodium ion battery, comprising a positive electrode, a negative electrode and the above-mentioned non-aqueous electrolyte.

[0035] Specifically, as some embodiments of the present invention, 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.

[0036] Specifically, as some embodiments of the present invention, 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.

[0037] Specifically, in some embodiments of the present invention, the chemical formula of the layered transition metal oxide is Na x M y O z , where 0 < x ≤ 1, 0 < y ≤ 1, 1 < z ≤ 2, and 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 / 9Ni 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.

[0038] In some embodiments of the present invention, the molecular formula of the Prussian compound is Na x M[M′(CN)6] y ·zH2O, where 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), and the Prussian compound is Na x Fe[Fe(CN)6] y ·zH2O (0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 20).

[0039] In some embodiments of the present invention, 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.

[0040] In some embodiments of the present invention, the chemical formula of the phosphate compound is Na2MPO4F, M is selected from one or more of Fe and Mn; the chemical formula of the phosphate compound is Na2FePO4F, Na2MnPO4F.

[0041] In some embodiments of the present invention, the chemical formula of the sulfate compound is Na2M(SO4)2·2H2O, and M can be selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.

[0042] Specifically, as some embodiments of the present invention, 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.

[0043] Specifically, as some embodiments of the present invention, 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.

[0044] Specifically, as some embodiments of the present invention, 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 will not be described in detail herein.

[0045] In some embodiments of the present invention, 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.

[0046] In some embodiments of the present invention, the sodium ion battery further includes a diaphragm, and the diaphragm is located between the positive electrode and the negative electrode.

[0047] The diaphragm may be an existing conventional diaphragm, which may 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 triple-layer PP / PE / PP diaphragms.

[0048] In some embodiments of the present invention, the preparation method of the sodium ion battery is a general preparation method for secondary batteries, that is, a positive electrode, a separator, and a negative electrode are combined, and an electrolyte is injected to obtain a sodium ion battery.

[0049] Compared with the prior art, the present invention achieves the following beneficial effects:

[0050] The sodium ion battery non-aqueous electrolyte of the present invention can significantly inhibit the decomposition and gas generation of the electrolyte at the positive and negative electrodes and improve the stability of the SEI film by selecting a phosphorus-containing compound additive of a specific general formula and an additive for inhibiting gas generation, and combining them with a cyclic ester solvent and a chain ester solvent, and controlling the content relationship of each additive and the solvent; the non-aqueous electrolyte of the present invention can significantly improve the cycle performance and rate performance of the sodium ion battery, and inhibit the gas generation of the battery. DETAILED DESCRIPTION

[0051] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0052] Examples 1-24

[0053] The present embodiment provides a sodium ion battery, which includes a positive electrode, a negative electrode and a non-aqueous electrolyte.

[0054] (1) Preparation of non-aqueous electrolyte

[0055] The solvents propylene carbonate (PC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) are mixed in a mass ratio of 25:50:25 to obtain an organic solvent, 1 mol / L sodium hexafluorophosphate is 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 are added.

[0056] (2) Preparation of positive electrode

[0057] The positive electrode active material NaNi was taken at a mass ratio of 88:9:3 0.3 Mn 0.3 Fe 0.4O2, 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 the aluminum foil, and after drying, calendering and vacuum drying, and aluminum lead wires are welded with an ultrasonic welder, a positive electrode plate is obtained, and the thickness of the plate is between 120-150μm.

[0058] (3) Preparation of negative electrode plate

[0059] 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, calendered and vacuum dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative electrode plate, and the thickness of the plate is between 120-150 μm.

[0060] (4) Preparation of battery cells

[0061] A three-layer separator with a thickness of 20 μm was placed between the positive electrode plate and the negative electrode plate prepared above, and then the sandwich structure consisting of the positive electrode plate, the negative electrode plate and the separator was wound, and then the wound body was flattened and placed in an aluminum foil packaging bag, and vacuum baked at 75°C for 48 hours to obtain a battery cell to be injected with liquid.

[0062] (5) Battery filling and formation

[0063] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell, vacuum packaged, and left to stand for 24 hours.

[0064] 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 discharging to 1.5V to obtain a sodium ion battery.

[0065] Comparative Examples 1-15

[0066] Comparative Examples 1-15 include most of the operating steps in the above embodiments, and the differences are as follows: 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; as shown in Table 1.

[0067] Table 1

[0068]

[0069]

[0070]

[0071] Note: DTD-vinyl sulfate; SN-succinonitrile; PS-1,3-propane sultone; TMSP-tri(trimethylsilyl) phosphate.

[0072] Performance Testing

[0073] The sodium ion batteries prepared in the above Examples 1-24 and Comparative Examples 1-15 were respectively subjected to the following performance tests:

[0074] 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.

[0075] High temperature cycle test: the formed battery was placed at 45℃ for 2h, charged to 3.9V at a constant current of 0.5C, then charged to 0.03C at a constant voltage, and then discharged to 1.5V at a constant current of 1C, for 400 cycles;

[0076] Capacity retention rate (%) = (discharge capacity C2 - charge capacity C1) / charge capacity C1 × 100%;

[0077] Gas production test: Immerse the batteries before and after gas production in a container filled with solvent. The difference in the overflowed solvent volume is the volume of gas production.

[0078] (1) The test results of Examples 1-12 and Comparative Examples 8-15 are shown in Table 2.

[0079] Table 2

[0080]

[0081]

[0082] It can be seen from the test results in Table 2 that in the sodium ion battery of the present invention, the non-aqueous electrolyte selected has a molecular formula of C x H y O 3z P z R mThe 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, 0.1≤c≤1, it can effectively inhibit gas production and improve the rate performance and cycle performance of the sodium ion battery.

[0083] 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 inhibiting 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 effect of improving the rate performance and cycle performance of the sodium ion battery and inhibiting gas production is better.

[0084] It can be seen from the test results of Example 1 and Comparative Examples 8-15 that when any one of the parameters a, b, and c of the content of the phosphorus-containing compound additive in the non-aqueous electrolyte does not meet the specified range or a / c+b is too large or too small, the sodium ion battery cannot be guaranteed to have good rate performance and cycle performance. This shows that the content a, b, and c of the phosphorus-containing compound additive, b, and c of the mass ratio of the cyclic ester solvent to the chain ester solvent have a strong correlation in improving the performance of the sodium ion battery.

[0085] (2) The test results of Example 1, Examples 13-15, and Comparative Example 7 are shown in Table 3.

[0086] Table 3

[0087]

[0088] From the test results of Example 1 and Examples 13-15 in Table 3, it can be seen that the phosphorus-containing compound additive selected by the present invention only needs 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 and the chain ester solvent meet the corresponding requirements, which can improve the rate performance and cycle performance of the sodium ion battery and inhibit gas generation.

[0089] It can be seen from the test results of Example 1, Examples 13-15 and Comparative Example 7 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, R is selected from any one or several 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 indicates the specificity of the selection of the phosphorus-containing compound additive in this application.

[0090] (3) The test results of Example 1 and Examples 16-18 are shown in Table 4.

[0091] Table 4

[0092]

[0093] From the test results of Example 1 and Examples 16-18 in Table 4, it can be seen that the sodium ion battery of the present invention uses different gas generation inhibitory additives. When the content a of the phosphorus compound additive, the content b of the gas generation inhibitory additive, and the mass ratio c of the cyclic ester solvent and the chain ester solvent meet the corresponding requirements, the rate performance and cycle performance of the sodium ion battery can be improved, and gas generation can be inhibited. This shows that the sodium ion battery of the present invention is universal for different gas generation inhibitory additives.

[0094] (4) The test results of Example 1 and Examples 19-21 are shown in Table 5.

[0095] Table 5

[0096]

[0097] From the test results of Example 1 and Examples 19-21 in Table 5, it can be seen that the sodium ion battery of the present invention, using different positive electrode active materials, when the content a of the phosphorus compound additive in the non-aqueous electrolyte, the content b of the gas generation inhibitor additive, and the mass ratio c of the cyclic ester solvent and the chain ester solvent meet the corresponding requirements, the rate performance and cycle performance of the sodium ion battery can be improved, and gas generation can be inhibited. This shows that the sodium ion battery of the present invention is universal for different positive electrode active materials.

[0098] (5) The test results of Example 1, Examples 22-24 and Comparative Examples 1-6 are shown in Table 6.

[0099] Table 6

[0100]

[0101] From the test results of Example 1 and Examples 22-24 in Table 6, it can be seen that in the sodium ion battery of the present invention, 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.

[0102] 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 only contains 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 contains a phosphorus-containing compound additive and a conventional additive DTD, and when the additive does not contain a phosphorus-containing compound additive, only contains 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 invention 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.

[0103] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

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 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 phosphorus-containing compound additive includes one or more of the following compounds: The solvent includes a cyclic ester solvent and a chain ester solvent; The non-aqueous electrolyte meets 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 compound additive in the non-aqueous electrolyte, in wt%; b is the mass percentage of the gas generation inhibiting 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 sodium ion battery nonaqueous electrolyte according to claim 1, characterized in that: The non-aqueous electrolyte satisfies the following condition: 1.5≤a / c+b≤7.

3. The sodium ion battery nonaqueous electrolyte according to claim 1, characterized in that: The mass percentage of the phosphorus compound additive in the non-aqueous electrolyte is 0.5-1.5wt%.

4. The sodium ion battery nonaqueous electrolyte according to claim 1, characterized in that: The mass percentage of the gas generation inhibiting additive in the non-aqueous electrolyte is 0.5-2.5wt%.

5. The sodium ion battery nonaqueous electrolyte according to claim 1, characterized in that: 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, characterized in that: The gas generation inhibiting additive includes one or more of tris(trimethylsilyl)borate, sodium difluorooxalatoborate, vinyl ethylene carbonate, and hexamethylene diisocyanate.

7. The non-aqueous electrolyte for sodium ion batteries according to claim 1, characterized in that: 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.

8. 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 trifluoromethylsulfonate, sodium bis(fluorosulfonyl)imide or sodium bis(trifluoromethylsulfonyl)imide.

9. A sodium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the non-aqueous electrolyte according to any one of claims 1 to 8.

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