A stable lithium / sodium-ion battery electrolyte and battery thereof

Abstract

The application discloses a stable lithium / sodium ion battery electrolyte and a battery thereof, and the electrolyte comprises a main lithium salt, a nonaqueous solvent and an additive, wherein the additive comprises: a first additive, the first additive at least comprises a novel composite metal salt with a structure shown in the following formula (I-1), and the amount of the first additive accounts for 0.01-15.0 wt% of the total mass of the electrolyte; and a second additive, the second additive is a stabilizer, and the amount of the second additive accounts for 0.001-1.0 wt% of the total mass of the electrolyte. The second additive can improve the stability of the first additive, not only inhibits the generation of a fluorinated polymer in the first additive, but also inhibits the decomposition of a-S-O-B- group in the first additive, strengthens the performance of the additive, and further improves the cycle performance and high-low temperature performance of the battery under high voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrolyte, in particular to an electrolyte containing pyrosulfate-boron trifluoride complex metal salt and stabilizer and its application in lithium ion battery or sodium ion battery. BACKGROUND

[0002] As an indispensable component in lithium / sodium ion battery, electrolyte additives are mainly responsible for building a stable electrode / electrolyte interface film to achieve electron insulation and facilitate lithium / sodium ion transmission. Under the influence of different functional groups in the additives, the composition and structure of the battery interface film change, ultimately affecting the battery cycle life, high-temperature storage and low-temperature discharge performance.

[0003] With the increasing demand for battery volume energy density, improving battery operating voltage and developing high-voltage electrolyte are the current mainstream methods. However, high voltage will lead to the decline of various electrochemical performances of the battery, which puts higher requirements on the performance of electrolyte additives. Further, in order to meet the working performance of the battery in high-temperature and low-temperature environments at the same time, the electrolyte is required to have excellent high-temperature and low-temperature performance. At present, most electrolyte additives only have high-temperature performance or low-temperature performance, and the combination of high-temperature additives and low-temperature additives is needed to meet the high and low temperature performance of the battery.

[0004] Pyrosulfate-boron trifluoride complex lithium salt is a new type of electrolyte additive with high and low temperature performance developed by Zhejiang Research Institute of Chemical Industry Co., Ltd. Its patent CN202211583064.X discloses that the additive can simultaneously improve the cycle performance, high-temperature storage performance and low-temperature performance of the battery. At the same time, patent CN202211583043.8 also discloses that pyrosulfate-boron trifluoride complex lithium salt, vinyl sulfate and / or 1,3-propane sultone are used in combination, or further combined with vinylene carbonate, so that the lithium ion battery still has excellent cycle performance, high-temperature storage performance and gas inhibition effect in high energy density system and high voltage environment, and can inhibit the impedance growth during battery cycle, further improving the low temperature performance.

[0005] Therefore, it is also an important research topic to continue to conduct in-depth research and develop more compositions of pyrosulfate-boron trifluoride complex metal salt with good stability, safety and environmental protection, and electrolyte formulations to meet the performance requirements of the battery in high energy density system and high voltage scenario. SUMMARY

[0006] During further research, it is found that with the increase of the storage time of the electrolyte, the colority of the electrolyte containing the pyrosulfate boron trifluoride complex metal salt increases, and even presents reddish brown. It is speculated through research that the sulfuric acid group and the sulfonic acid group in the pyrosulfate boron trifluoride complex metal salt will exacerbate the electrolyte acidity under the action of the electron-deficient boron component, and then cause the polymerization reaction of the solvent molecules such as ethylene carbonate (EC) and methyl ethyl carbonate (EMC) to produce polymers containing conjugated double bonds, and the electrolyte discoloration is intensified; at the same time, the colority problem caused by the electrolyte side reaction is also accompanied by the deterioration of the battery electrochemical performance, and the obvious decline of the battery cycle performance and high-temperature storage performance.

[0007] In order to solve the above technical problems, the present application further proposes an electrolyte containing a pyrosulfate boron trifluoride complex metal salt and a stabilizer and its application in lithium ion / sodium ion batteries. The electrolyte not only makes the lithium ion / sodium ion battery have high-temperature cycle performance, high-temperature storage performance and low-temperature performance at high voltage, but also improves the stability of the electrolyte, inhibits the discoloration of the electrolyte, and solves the problem of the deterioration of the battery electrochemical performance caused by the colority problem of the electrolyte decomposition.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A stable lithium / sodium ion battery electrolyte comprises a main salt, a non-aqueous solvent and an additive, wherein the additive comprises:

[0010] The first additive comprises at least a novel complex metal salt represented by the following formula (I-1), and the amount is 0.01-15.0wt% of the total mass of the electrolyte:

[0011]

[0012] In formula (I-1), M is Li or Na; preferably, M is Li;

[0013] The second additive is a stabilizer, which is at least one compound represented by the following structure, and the amount is 0.001-1.0wt% of the total mass of the electrolyte:

[0014]

[0015] During the preparation of the first additive of the present application, in addition to the novel complex metal salt represented by the above-mentioned (I-1), at least one of the following compounds represented by the following formula (I-2), (I-3), (I-4), (I-5) and (I-6) is also included:

[0016]

[0017]

[0018] In formula (I-2), (I-3), (I-4), (I-5), (I-6), M is Li or Na;

[0019] Preferably, the first additive contains 80-95wt% of the novel composite lithium salt of the structure shown in formula (I-1), and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5), or (I-6).

[0020] Preferably, the amount of the first additive is 0.2-5.0wt% of the total mass of the electrolyte, more preferably 0.5-2wt%.

[0021] The amount of the second additive is 0.001-1.0wt% of the total mass of the electrolyte, more preferably 0.01-0.1wt%, and even more preferably 0.02-0.05wt%.

[0022] Further, the second additive is at least one selected from compounds (II-1), (II-2), (II-3), (II-8).

[0023] In the charging and discharging process of the battery, the -S-O-B- group in the first additive can form a cross-linked network interface film containing S and B at the electrode interface, regulate the content of inorganic salts such as M2SO4, M2SO3, M2SO4, M2SO3 (M is Li or Na) in the interface film, effectively reduce the internal resistance of the battery, and improve the low temperature performance of the battery. At the same time, the cross-linked network interface film contains more Li + or Na + pores, has high ionic conductivity, and significantly improves the low temperature performance of the battery. However, when the first additive exists alone, the -S-O-B- group is prone to decomposition, which weakens its superior performance effect in the battery electrolyte. In addition, the -B-F group in the first additive has strong fluorination effect, which is prone to react with organic solvents to generate fluorinated polymers, resulting in discoloration of the electrolyte.

[0024] The second additive structure of the present application contains reducing and weakly basic groups, which can not only inhibit the decomposition of LiPF6 or NaPF6, neutralize Lewis acids such as PF5 or POF3, but also combine with the -B-F group in the first additive to weaken the fluorination of the -B-F group, inhibit the formation of fluorinated polymers, and improve the stability of the electrolyte. At the same time, not only does the second additive itself have the ability to eliminate the oxidative components generated by the positive electrode, but it can also improve the electrochemical performance of the battery at high voltage and high temperature. The second additive can also inhibit the decomposition of the -S-O-B- group in the first additive, enhance the performance advantages of the first additive, and further improve the cycle performance and high and low temperature performance of the battery.

[0025] According to the above stable lithium / sodium ion battery electrolyte, the main salt is a main lithium salt or a main sodium salt.

[0026] The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoro(oxalato)phosphate, lithium tris(oxalato)phosphate, or lithium difluoro-bis(oxalato)phosphate;

[0027] The main sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium perchlorate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium tetrafluoro(oxalato)phosphate, sodium tris(oxalato)phosphate, or sodium difluoro-bis(oxalato)phosphate.

[0028] The non-aqueous solvent is selected from at least one of a C3-C6 carbonate or fluorinated carbonate compound, a C3-C8 carboxylate or fluorinated carboxylate compound, a sulfone compound, or an ether compound.

[0029] Preferably, the C3-C6 carbonate or fluorinated carbonate compound is selected from at least one of vinyl carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate; the C3-C8 carboxylate or fluorinated carboxylate compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; and the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether, dioxolane.

[0030] Generally, the non-aqueous solvent in the lithium ion battery electrolyte and the sodium ion battery electrolyte can be the same. Therefore, the above non-aqueous solvent can be applied to the lithium ion battery electrolyte or the sodium ion battery electrolyte.

[0031] The additive also includes a base additive selected from at least one of fluoroethylene carbonate, vinylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propene sultone, lithium difluorophosphate, lithium bisfluorosulfonylimide, succinic anhydride, adipodinitrile, cyclohexylbenzene, lithium difluorophosphate bisoxalate, lithium difluoroboric acid oxalate, sodium difluoroboric acid oxalate, sodium difluorophosphate, sodium bisfluorosulfonylimide, or sodium difluorophosphate bisoxalate, and any one of the base additives accounts for 0.1-5 wt% of the total mass of the electrolyte, and the base additive is different from the main salt, for meeting the application scenarios and the battery electrochemical performance requirements of different electrolytes.

[0032] In a specific embodiment, a high-stable lithium ion battery electrolyte is provided, including a main salt, a non-aqueous solvent, a first additive, a second additive, and a base additive, the main salt is preferably LiPF6, and the molar concentration in the non-aqueous solvent is 0.5-2.0 mol / L; the non-aqueous solvent is preferably at least one of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), and more preferably a mixed solvent of EC, EMC, and DEC, and the mass ratio of the three is EC: EMC: DEC = 4:4:2, 3:4:3, 3:5:2, or 3:3:4, etc. The first additive and the second additive are as described above, and the first additive is a composite lithium salt; the base additive includes vinylene carbonate, fluoroethylene carbonate, 1,3-propene sultone, lithium difluorophosphate, and lithium difluoroboric acid oxalate, and the amount accounts for 0.5-2 wt% of the total mass of the electrolyte.

[0033] In another specific embodiment, a high-stable sodium ion battery electrolyte is provided, including a main salt, a non-aqueous solvent, a first additive, a second additive, and a base additive, the main salt is preferably NaPF6, and the molar concentration in the non-aqueous solvent is 0.5-2.0 mol / L; the non-aqueous solvent is preferably at least one of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and propylene carbonate (PC), and more preferably a mixed solvent of EC, EMC, and PC, and the mass ratio of the three is EC: EMC: PC = 7:10:1, 3:4:3, 3:5:2, or 4:4:2, etc. The first additive and the second additive are as described above, and the first additive is a composite sodium salt; the base additive includes vinylene carbonate, 1,3-propene sultone, sodium difluoroboric acid oxalate, sodium bisfluorosulfonylimide, and sodium difluorophosphate bisoxalate, and the amount accounts for 0.5-2 wt% of the total mass of the electrolyte.

[0034] The present application provides a lithium ion secondary battery, including a positive electrode, a negative electrode, and a separator, and the above-mentioned electrolyte is filled in the lithium ion secondary battery.

[0035] Specifically, the active material of the positive electrode is selected from a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, a lithium cobaltate material, or a lithium iron phosphate material, and the active material of the negative electrode is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or a composite material thereof.

[0036] The application also provides a sodium-ion secondary battery comprising a positive electrode, a negative electrode, and a separator, and the sodium-ion secondary battery is filled with the electrolyte described in any of the above.

[0037] The active material of the positive electrode tab is selected from at least one of NaMn (1-x-y) Ni y M x O2(0≤x, y≤1, M is Cu, Fe, Co), sodium manganate, sodium ammonium phosphate, sodium fluorophosphate ammonium, sodium iron phosphate, sodium manganese phosphate, Na x MnFe(CN)6(0<x≤2), and the active material of the negative electrode tab is selected from at least one of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, a silicon-based material, a metal oxide, a metal sulfide, or metallic sodium.

[0038] Compared with the prior art, the application has the beneficial effects that:

[0039] Through the mutual synergy of the first additive and the second additive, the second additive can significantly improve the stability of the first additive, and improve the electrochemical performance of the battery at high voltage and high temperature, which is specifically manifested in the following aspects: first, the second additive can inhibit the generation of fluorinated polymers of the first additive and inhibit the discoloration of the electrolyte; second, the second additive can inhibit the decomposition of the-S-O-B-group in the first additive, strengthen the superior performance of the first additive, and further improve the cycle performance and high-low temperature performance of the battery; third, the second additive itself has the function of annihilating the oxidizing components generated by the positive electrode, which helps to improve the electrochemical performance of the battery at high voltage and high temperature. DETAILED DESCRIPTION

[0040] The application will be further described below in conjunction with specific embodiments, but the application is not limited to these specific embodiments. Those skilled in the art should recognize that the application encompasses all alternatives, improvements, and equivalents within the scope of the claims.

[0041] In the examples and comparative examples of the application, the types of the first additive include the following:

[0042] The first additive A contains 95wt% of compound I-1 and 5wt% of compound I-2, and both are composite lithium salts;

[0043] First additive B: contains 90 wt% of compound I-1, 6 wt% of compound I-2 and 4 wt% of compound I-3, and all are complex lithium salts;

[0044] First additive C: contains 85 wt% of compound I-1, 7 wt% of compound I-2, 5 wt% of compound I-3 and 3 wt% of compound I-4, and all are complex lithium salts.

[0045] First additive D: contains 95 wt% of compound I-1 and 5 wt% of compound I-2, and all are complex sodium salts.

[0046] I. Preparation of electrolyte

[0047] Preparation of base electrolyte 1: In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC: EMC: DEC = 4:4:2, and then lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 was 1.0 mol / L, to obtain the base electrolyte 1.

[0048] Preparation of base electrolyte 2: In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), propylene carbonate (PC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC: EMC: PC = 7:10:1, and then sodium hexafluorophosphate (NaPF6) was slowly added to the mixed solution until the molar concentration of NaPF6 was 1.0 mol / L, to obtain the base electrolyte 2.

[0049] Example 1

[0050] In the base electrolyte 1, 0.5 wt% of the first additive A and 0.01 wt% of compound II-1 were added to obtain the electrolyte of the present example.

[0051] Example 2

[0052] In the base electrolyte 1, 0.5 wt% of the first additive A and 0.05 wt% of compound II-1 were added to obtain the electrolyte of the present example.

[0053] Example 3

[0054] In the base electrolyte 1, 1.0 wt% of the first additive A and 0.1 wt% of compound II-1 were added to obtain the electrolyte of the present example.

[0055] Example 4

[0056] In the base electrolyte 1, 2 wt% of the first additive A and 0.1 wt% of the compound II-1 were added to obtain the electrolyte of the present example.

[0057] Example 5

[0058] In the base electrolyte 1, 5 wt% of the first additive A and 0.1 wt% of the compound II-1 were added to obtain the electrolyte of the present example.

[0059] Example 6

[0060] In the base electrolyte 1, 15 wt% of the first additive A and 1.0 wt% of the compound II-1 were added to obtain the electrolyte of the present example.

[0061] Example 7

[0062] In the base electrolyte 1, 0.01 wt% of the first additive A and 0.02 wt% of the compound II-6 were added to obtain the electrolyte of the present example.

[0063] Example 8

[0064] In the base electrolyte 1, 0.5 wt% of the first additive A and 0.2 wt% of the compound II-1 were added to obtain the electrolyte of the present example.

[0065] Example 9

[0066] In the base electrolyte 1, 0.5 wt% of the first additive A and 0.001 wt% of the compound II-6 were added to obtain the electrolyte of the present example.

[0067] Example 10

[0068] In the base electrolyte 1, 0.5 wt% of the first additive A and 0.02 wt% of the compound II-2 were added to obtain the electrolyte of the present example.

[0069] Example 11

[0070] In the base electrolyte 1, 0.5 wt% of the first additive B and 0.02 wt% of the compound II-3 were added to obtain the electrolyte of the present example.

[0071] Example 12

[0072] In the base electrolyte 1, 1 wt% of the first additive B and 0.03 wt% of the compound II-4 were added to obtain the electrolyte of the present example.

[0073] Example 13

[0074] In the base electrolyte 1, 0.5 wt% of the first additive C and 0.05 wt% of compound II-5 were added to obtain the electrolyte of this embodiment.

[0075] Example 14

[0076] In the base electrolyte 1, 1.0 wt% of the first additive C and 0.05 wt% of compound II-7 were added to obtain the electrolyte of this embodiment.

[0077] Example 15

[0078] In the base electrolyte 1, 0.5 wt% of first additive A, 0.05 wt% of compound II-1 and 1.0 wt% of VC were added to obtain the electrolyte of this embodiment.

[0079] Example 16

[0080] In the base electrolyte 1, 0.5 wt% of first additive A, 0.05 wt% of compound II-1 and 1.0 wt% of FEC were added to obtain the electrolyte of this embodiment.

[0081] Example 17

[0082] In the basic electrolyte 1, 0.5 wt% of the first additive A, 0.02 wt% of compound II-2, 1.0 wt% of VC and 1.0 wt% of LiPO2F2 were added to obtain the electrolyte of this embodiment.

[0083] Example 18

[0084] In the base electrolyte 2, 0.5 wt% of the first additive D and 0.05 wt% of compound II-3 were added to obtain the electrolyte of this embodiment.

[0085] Example 19

[0086] The electrolyte of this embodiment is obtained by adding 1 wt% of the first additive D and 0.05 wt% of compound II-8 to the base electrolyte 2.

[0087] Example 20

[0088] In the base electrolyte 2, 1 wt% of the first additive D, 0.05 wt% of compound II-8 and 1 wt% of PS were added to obtain the electrolyte of this embodiment.

[0089] Comparative Example 1

[0090] In the basic electrolyte 1, 0.5 wt% of the first additive A was added to obtain the electrolyte of this comparative example.

[0091] Comparative Example 2

[0092] In the base electrolyte 1, 0.5wt% of the first additive B was added to obtain the electrolyte of the present comparative example.

[0093] Comparative Example 3

[0094] In the base electrolyte 1, 0.05wt% of the compound II-1 was added to obtain the electrolyte of the present comparative example.

[0095] Comparative Example 4

[0096] In the base electrolyte 1, 1wt% of the first additive A and 1.5wt% of the compound II-1 were added to obtain the electrolyte of the present comparative example.

[0097] Comparative Example 5

[0098] In the base electrolyte 1, 1wt% of the first additive A and 0.0001wt% of the compound II-1 were added to obtain the electrolyte of the present comparative example.

[0099] Comparative Example 6

[0100] In the base electrolyte 1, 1wt% of the first additive A and 0.1wt% of pyridine were added to obtain the electrolyte of the present comparative example.

[0101] Comparative Example 7

[0102] The base electrolyte 1 was used as the electrolyte of the present comparative example.

[0103] Comparative Example 8

[0104] In the base electrolyte 2, 1wt% of the first additive D was added to obtain the electrolyte of the present comparative example.

[0105] Comparative Example 9

[0106] In the base electrolyte 2, 0.05wt% of the compound II-8 was added to obtain the electrolyte of the present comparative example.

[0107] Comparative Example 10

[0108] The base electrolyte 2 was used as the electrolyte of the present comparative example.

[0109] II. Colorimetric test of electrolyte storage

[0110] Part of the electrolytes of the above prepared examples and comparative examples were transferred to sealed aluminum bottles and placed in a constant temperature oven at 50°C for storage. The colorimetric values of the electrolytes were detected before storage, 7 days after storage and 28 days after storage respectively in a glove box. The colorimetric test method used platinum-cobalt colorimetry and the colorimetric unit was Hazen. The test results are shown in Table 1 below:

[0111] Table 1 Electrolyte colorimetric test results table

[0112]

[0113]

[0114] From the above table 1, the use of the first additive can cause the electrolyte colorimetric stability to decrease, and the second additive has obvious reducing effect on the colorimetric of the electrolyte.

[0115] Comparing example 3, example 4 and example 5, it can be known that with the increase of the addition amount of the first additive A, the colorimetric of the electrolyte also increases. Comparing example 1, example 2 and example 8, it can be known that the increase of the content of compound II-1 can further reduce the colorimetric of the electrolyte.

[0116] III. Electrochemical performance test

[0117] The electrolyte of the above examples 1-17 and comparative examples 1-7 is respectively made into a soft package capacity 1260 mAh lithium ion battery, the lithium ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and a battery auxiliary material, the positive electrode active material is ternary positive electrode LiNi 0.6 Co 0.2 Mn 0.2 O2, and the negative electrode active material is high-capacity graphite. The preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a roll core, sealed with an aluminum plastic film, and then baked to make the electrode moisture meet the requirements. After baking, the battery core is subjected to electrolyte injection, standing, formation, capacity distribution and aging processes to obtain a finished lithium ion battery soft package battery core.

[0118] The electrolyte of the above examples 18-20 and comparative examples 8-10 is respectively made into a soft package capacity 1000 mAh sodium ion battery, the sodium ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and a battery auxiliary material, the positive electrode active material is ternary positive electrode NaNi 0.33 Fe 0.33 Mn 0.33 O2, and the negative electrode active material is hard carbon. The preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a roll core, sealed with an aluminum plastic film, and then baked to make the electrode moisture meet the requirements. After baking, the battery core is subjected to electrolyte injection, standing, formation, capacity distribution and aging processes to obtain a finished sodium ion soft package battery core.

[0119] The lithium ion battery and the sodium ion battery prepared above are subjected to performance test (test voltage 2.8-4.2V), mainly including:

[0120] (1) 60℃ high temperature storage test: charge the battery to 100% SOC, store in a 60±2℃ oven for 28 days, test the volume before and after storage, and obtain the volume expansion rate of single battery before and after 60℃ storage.

[0121] (2) 45℃ high temperature cycle test: the battery is cycled in a 45±1℃ oven at 1C / 1C charge-discharge current, the discharge capacity per week is calculated, and the cycle is stopped after 500 cycles, and the capacity retention rate after cycle is calculated.

[0122] (3) -20℃ low temperature discharge: the battery is discharged to 80% of the lower limit voltage at a discharge current of 1C in a -20±1℃ oven, as low temperature discharge capacity, and calculate its percentage of 1C discharge capacity at 25℃, recorded as low temperature discharge capacity retention rate.

[0123] The test results are shown in Table 2 below:

[0124] Table 2 Battery electrochemical performance test results

[0125]

[0126]

[0127] From Table 2 above, the addition of the first additive A, the first additive B or the first additive C in the lithium ion battery electrolyte can reduce the initial impedance of the battery, improve the low temperature discharge performance, and at the same time can inhibit the gas production and impedance growth of the battery during high temperature storage, and improve the cycle performance, which can achieve the effect of considering high and low temperature performance. At the same time, the use of the first additive D in the sodium ion battery can also achieve the same effect.

[0128] From Table 2 above, the addition of the second additive can significantly improve the electrochemical performance of the battery, because: the addition of the second additive can inhibit the decomposition of the -S-O-B- group in the first additive, strengthen the superior performance of the first additive, and further improve the cycle performance and high and low temperature performance of the battery.

[0129] From the comparison of Examples 2-6, it can be seen that with the increase of the addition amount of the first additive A, the comprehensive performance of the battery is improved first, and with the further increase of the addition amount, the battery performance cannot continue to improve, and the best addition amount is about 0.5-2.0wt%.

[0130] By comparing Example 15 with Example 2, it can be found that the simultaneous addition of the first additive A, the second additive and VC in the electrolyte can not only avoid the defect that the VC increases the initial impedance of the battery, but also further improve the high-temperature storage performance and the cycle performance. By comparing Example 17 with Example 2 and Example 15, it can be found that on the basis of adding the first additive and the second additive, further adding conventional additives such as VC and LiPO2F2 can further improve the high and low temperature performance of the battery.

Claims

1. A stable lithium / sodium-ion battery electrolyte comprising a host salt, a nonaqueous solvent, and an additive, characterized in that: The additive comprises: The first additive comprises at least a novel complex metal salt of the structure shown in the following formula (I-1), and the amount is 0.01-15.0wt% of the total mass of the electrolyte: In the formula (I-1), M is Li or Na; The second additive is a stabilizer, and is at least one compound selected from the following structures, and the amount is 0.001-1.0wt% of the total mass of the electrolyte:

2. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The M is Li.

3. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The first additive further comprises at least one of the following compounds of the formula (I-2), (I-3), (I-4), (I-5), (I-6): In the formula (I-2), (I-3), (I-4), (I-5), (I-6), M is Li or Na; And the first additive contains at least 80wt% of the novel complex metal salt of the structure shown in the formula (I-1).

4. The stable lithium / sodium-ion battery electrolyte of claim 3, wherein: The first additive contains 80-95wt% of the novel complex metal salt of the structure shown in the formula (I-1), and the rest is at least one of the compounds (I-2), (I-3), (I-4), (I-5) or (I-6).

5. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The amount of the first additive is 0.2-5.0wt% of the total mass of the electrolyte.

6. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The amount of the second additive is 0.01-0.1wt% of the total mass of the electrolyte.

7. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The second additive is at least one of the compounds (II-1), (II-2), (II-3), (II-8).

8. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The main salt is a main lithium salt or a main sodium salt, the main lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium bisfluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium tetrafluoro oxalate phosphate, lithium trioxalate phosphate or lithium difluoro bisoxalate phosphate; and the main sodium salt is at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bisfluorosulfonimide, sodium bis-trifluoromethylsulfonimide or sodium difluorophosphate.

9. The stable lithium / sodium-ion battery electrolyte of claim 1, wherein: The non-aqueous solvent is at least one of C3-C6 carbonate or fluorinated carbonate compound, C3-C8 carboxylate or fluorinated carboxylate compound, sulfone compound or ether compound; The C3-C6 carbonate or fluorinated carbonate compound is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate or ethyl propyl carbonate; the C3-C8 carboxylate or fluorinated carboxylate compound is at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate or propyl propionate; the sulfone compound is at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone or diethyl sulfone; and the ether compound is at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether or dioxolane.

10. The stable lithium / sodium-ion battery electrolyte according to any one of claims 1-9, characterized in that: The additive further comprises a base additive selected from at least one of fluoroethylene carbonate, vinylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propene sultone, lithium difluorophosphate, lithium bisfluorosulfonylimide, succinic anhydride, adipodinitrile, cyclohexylbenzene, lithium bis(oxalato)difluorophosphate, lithium difluoro(oxalato)borate, sodium difluoro(oxalato)borate, sodium difluorophosphate, sodium bisfluorosulfonylimide, sodium bis(oxalato)difluorophosphate, and such that any one base additive is present in a range of 0.1 to 5.0 wt% of the total mass of the electrolyte, and the base additive is different from the host salt.

11. A lithium / sodium-ion secondary battery comprising a positive electrode, a negative electrode, and a separator, characterized by: The lithium / sodium ion secondary battery is filled with the electrolyte according to any one of claims 1-10. 12.The lithium / sodium ion secondary battery according to claim 11, wherein: In the lithium ion secondary battery, the active material of the positive electrode is selected from a nickel-cobalt-manganese ternary material, a nickel-cobalt-aluminum ternary material, a lithium cobaltate material, or a lithium iron phosphate material, and the active material of the negative electrode is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium, or a composite material thereof. In the sodium-ion secondary battery, the active material of the positive electrode is selected from NaMn (1-x-y) Ni y M x O2(0≤x, y≤1, M is Cu, Fe, Co), sodium manganate, sodium aluminophosphate, sodium fluorophosphate aluminophosphate, sodium iron phosphate, sodium manganese phosphate, Na x at least one of MnFe(CN)6(0 < x≤2), the active material of the negative electrode is selected from at least one of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, silicon-based material, metal oxide, metal sulfide or metal sodium.

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