Non-aqueous electrolyte for lithium-ion battery and lithium-ion battery having the same

Abstract

The present invention discloses a non-aqueous electrolyte for lithium-ion batteries and a lithium-ion battery having the electrolyte. The raw materials thereof include: an electrolyte, a non-aqueous organic solvent, and an additive. The additive includes one or a mixture of two or more of compound A, compound B, vinylene carbonate, 1,3-propane sultone, and ethylene sulfate. In the present invention, compound B is used as an additive to improve the low-temperature performance of compound A. The sulfur oxide contained therein can first react with the double bond of vinylene carbonate to passivate the activity, inhibit the reaction of isocyanate groups, and reduce the influence on the low-temperature performance. The present invention also discloses a lithium-ion battery having the above electrolyte. Through the combined action of compound A and compound B, the lithium-ion battery of the present invention effectively improves the decomposition of DTD at high temperatures without affecting the high-temperature and low-temperature performance of the battery, and reduces the costs during storage, transportation, and production of the electrolyte.

Description

Technical Field

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

[0002] The electrolytes currently used in industrial lithium-ion batteries are mainly LiPF6, LiBF4, LiCLO4, LiI, etc. The electrolyte concentration is 0.1-2.0 mol / L, and organic substances such as EC-PC-DMC-DEC-EMC (EC is ethylene carbonate, PC is propylene carbonate, DMC is dimethyl carbonate, DEC is diethyl carbonate, and EMC is ethyl methyl carbonate) are used as solvents.

[0003] The electrolyte has a great influence on the performance of lithium batteries, mainly because the composition, concentration, viscosity, and conductivity of the electrolyte are related to the electrode surface reaction. The conductivity of the electrolyte and the reversibility of the electrode reaction directly affect the discharge capacity of the lithium battery. The stability of the electrolyte will affect the safety performance of the lithium battery. The electrolyte also has a great influence on the specific capacity, operating temperature range, charge and discharge cycle efficiency, and high and low temperature performance of the lithium battery.

[0004] DTD (vinyl sulfate) is widely used in lithium-ion secondary battery electrolytes. It can form low-impedance and stable SEI films of Li2SO3 and ROSO2Li at the positive and negative electrodes, which effectively inhibits the oxidation, decomposition and reduction reactions of the positive and negative electrode materials with the electrolyte surface. The resulting polarization of the electrode surface increases, the impedance increases, and the reaction byproducts with low conductivity cover the surface, causing rapid cycle drops and severe gas production at high temperatures. Because DTD can ensure the low-temperature performance of the battery while taking into account good high-temperature performance, it is widely added to the electrolyte of lithium-ion batteries as an additive.

[0005] A Chinese patent (patent number: CN201610458121.X) mentions an electrolyte for lithium-ion batteries and a lithium-ion battery containing the electrolyte. The use of a high-temperature additive HMDI (hexamethylene diisocyanate) can improve the storage performance of lithium-ion batteries at high temperatures, and additives such as FEC and VEC can effectively improve the poor low-temperature performance caused by the addition of HMDI.

[0006] However, DTD at high temperature (over 10°C) will hydrolyze LiPF6 and produce colored substances under the catalysis of the strong Lewis acid of the reaction product PF5, resulting in a significant increase in color. Therefore, low-temperature storage is required, which causes a certain increase in costs for material storage, transportation, and production process. Summary of the invention

[0007] The object of the present invention is to provide a non-aqueous electrolyte for lithium-ion batteries and a lithium-ion battery having the same.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A non-aqueous electrolyte for lithium-ion batteries, the raw materials of the non-aqueous electrolyte for lithium-ion batteries including: an electrolyte, a non-aqueous organic solvent, and an additive, the additive including one or a mixture of two or more of compound A, compound B, vinylene carbonate, 1,3-propane sultone, or ethylene sulfate;

[0010] The general formula of the compound A is:

[0011]

[0012] Among them, R1 and R2 are one or more of alkyl C n H 2n+1 、alkenyl C n H 2n 、polyene group, aromatic hydrocarbon group, alkoxy group, or isocyanate, and the number of carbon atoms in R1 and R2 is 1≤n≤7;

[0013] The general formula of the compound B is:

[0014]

[0015] Among them, R1' is one or a mixture of two or more of alkyl C m H 2m+1 、alkenyl C m H 2m 、polyene group, aromatic hydrocarbon group, alkoxy group, fluoroalkoxy group, or sulfoxide; the number of carbon atoms in R1' is 0≤m≤7;

[0016] Based on the electrolyte quality being 100%, the content of the additive accounts for 1.5% - 5% of the electrolyte.

[0017] As a preferred embodiment of the present invention, based on the electrolyte quality being 100%, the compound A accounts for 0.1% - 1% of the electrolyte, the compound B accounts for 0.1% - 3% of the electrolyte, vinylene carbonate accounts for 1.5% of the electrolyte, 1,3-propane sultone accounts for 1% of the electrolyte, and ethylene sulfate accounts for 2% of the electrolyte.

[0018] As a preferred embodiment of the present invention, based on the electrolyte quality being 100%, the compound A accounts for 0.1% - 0.5% of the electrolyte, the compound B accounts for 0.1% - 1% of the electrolyte, vinylene carbonate accounts for 1.5% of the electrolyte, 1,3-propane sultone accounts for 1% of the electrolyte, and ethylene sulfate accounts for 2% of the electrolyte.

[0019] As a preferred embodiment of the present invention, the electrolyte includes one or a combination of several of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(fluorosulfonyl)imide. Based on the electrolyte mass being 100%, the electrolyte accounts for 10% - 14.5% of the electrolyte solution.

[0020] As a preferred embodiment of the present invention, the non-aqueous organic solvent includes a mixture of two or more of EC, EMC, DEC, DMC, and PC, and the non-aqueous organic solvent accounts for 81.5% - 83% of the electrolyte solution.

[0021] As a preferred embodiment of the present invention, the additive is a composition of compound A, compound B, vinylene carbonate, 1,3-propane sultone, and ethylene sulfate.

[0022] As a preferred embodiment of the present invention, compound A is hexamethylene diisocyanate.

[0023] As a preferred embodiment of the present invention, compound B is triethylamine trioxide sulfur.

[0024] As a preferred embodiment of the present invention, the electrolyte is LiPF6 or LiFSI.

[0025] The present invention also discloses a lithium-ion battery having the above non-hydrolyzable electrolyte for a lithium-ion battery.

[0026] The present invention has the following beneficial effects: In the present invention, compound A introduces an isocyanate group on the basis of hexamethylene, which can form a good passivation film on the surfaces of the positive and negative electrodes of the lithium battery, so as to well protect the surfaces of the positive and negative electrodes. Isocyanate can consume trace moisture, react with HF, and inhibit PF5 generated by the hydrolysis of LiPF6, and can reduce the catalytic effect of PF5 on DTD. When the content of compound A is less than 0.1%, the film-forming effect of the SEI film at the electrode interface is poor, and it cannot well protect the electrode surface, and the inhibitory effect on PF5 is not obvious. When the content of compound A is greater than 1%, the isocyanate group (-N = C = O) will chemically react with the double bond (-C = C-) in vinylene carbonate at low temperature, resulting in serious lithium precipitation at low temperature of the battery and deteriorating the low-temperature discharge capacity.

[0027] In the present invention, compound B is an additive to improve the low-temperature performance of compound A. The sulfur oxide contained therein can first react with the double bond of vinylene carbonate to passivate the activity and inhibit the reaction of the isocyanate group, reducing the impact on the low-temperature performance. When the content of compound B is less than 0.1%, the effect of inhibiting the isocyanate group is not obvious. When the content of compound B is greater than 3%, the viscosity of the electrolyte solution will increase, and the migration of lithium ions will become difficult.

[0028] Compared with the prior art, through the combined action of Compound A and Compound B, the present invention effectively improves the decomposition of DTD at high temperatures without affecting the high-temperature and low-temperature performance of the battery, and reduces the costs of the electrolyte during storage, transportation, and production. Description of the Drawings

[0029] Figure 1 It is an SEM test diagram of the graphite negative electrode in Comparative Example 1 of the present invention after three cycles of disassembling the button battery.

[0030] Figure 2 It is an SEM test diagram of the graphite negative electrode in Comparative Example 3 of the present invention after three cycles of disassembling the button battery.

[0031] Figure 3 It is an SEM test diagram of the graphite negative electrode in Example 4 of the present invention after three cycles of disassembling the button battery.

[0032] Figure 4 It is the impedance comparison curve trend of the batteries in Example 4, Comparative Example 1, and Comparative Example 3 of the present invention in the initial state.

[0033] Figure 5 It is the impedance comparison curve trend of the batteries in Example 4, Comparative Example 1, and Comparative Example 3 of the present invention after three cycles. Detailed Embodiments

[0034] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0035] The raw materials used in the present invention can all be purchased from the market.

[0036] Example 1

[0037] A non-aqueous electrolyte for a lithium-ion battery, based on 100 g of the electrolyte mass, contains the following components and contents: 11.03 g of LiPF6, 30.25 g of EC, 36.82 g of EMC, 13.40 g of DEC, 1 g of Compound A (hexamethylene diisocyanate), 3 g of Compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0038] Example 2

[0039] A non-aqueous electrolyte for a lithium-ion battery, based on a 100 g electrolyte mass, contains the following components and contents: 11.54 g of LiPF6, 30.74 g of EC, 37.82 g of EMC, 13.40 g of DEC, 1 g of compound A (hexamethylene diisocyanate), 1 g of compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0040] Example 3

[0041] A non-aqueous electrolyte for a lithium-ion battery, based on a 100 g electrolyte mass, contains the following components and contents: 11.67 g of LiPF6, 31.04 g of EC, 38.26 g of EMC, 13.40 g of DEC, 1 g of compound A (hexamethylene diisocyanate), 0.1 g of compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0042] Example 4

[0043] A non-aqueous electrolyte for a lithium-ion battery, based on a 100 g electrolyte mass, contains the following components and contents: 11.92 g of LiPF6, 30.64 g of EC, 38.04 g of EMC, 13.40 g of DEC, 0.5 g of compound A (hexamethylene diisocyanate), 1 g of compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0044] Example 5

[0045] A non-aqueous electrolyte for a lithium-ion battery, based on a 100 g electrolyte mass, contains the following components and contents: 12.04 g of LiPF6, 30.92 g of EC, 38.04 g of EMC, 13.40 g of DEC, 0.1 g of compound A (hexamethylene diisocyanate), 1 g of compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0046] Example 6

[0047] A non-aqueous electrolyte for a lithium-ion battery, based on a 100 g electrolyte mass, contains the following components and contents: 12.12 g of LiPF6, 30.92 g of EC, 38.06 g of EMC, 13.40 g of DEC, 0.5 g of compound A (hexamethylene diisocyanate), 0.5 g of compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0048] Comparative Example 1

[0049] A non-aqueous electrolyte for lithium-ion batteries. Based on 100 g of the electrolyte mass, it contains the following components and contents: 11.98 g of LiPF6, 30.87 g of EC, 38.10 g of EMC, 14.55 g of DEC, 1.5% of vinylene carbonate, 1% of 1,3-propane sultone, and 2% of ethylene sulfate.

[0050] Comparative Example 2

[0051] A non-aqueous electrolyte for lithium-ion batteries. Based on 100 g of the electrolyte mass, it contains the following components and contents: 12.02 g of LiPF6, 30.13 g of EC, 37.80 g of EMC, 14.55 g of DEC, 1 g of Compound A (hexamethylene diisocyanate), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0052] Comparative Example 3

[0053] A non-aqueous electrolyte for lithium-ion batteries. Based on 100 g of the electrolyte mass, it contains the following components and contents: 11.27 g of LiPF6, 31.01 g of EC, 37.32 g of EMC, 14.90 g of DEC, 1 g of Compound B (triethylamine trioxide), 1.5 g of vinylene carbonate, 1 g of 1,3-propane sultone, and 2 g of ethylene sulfate.

[0054] The electrolytes of Examples 1 to 6 and Comparative Examples 1 to 3 were stored at 50 °C for 5 days and 30 days respectively. The electrolyte colority comparison is listed in Table 1 below:

[0055] Table 1. Electrolyte Colority Comparison

[0056]

[0057] As can be seen from Table 1, as the content of Compound A decreases from high to low, the colority gradually increases. It is obvious that Compound A has a good inhibitory effect on the discoloration caused by the decomposition of DTD at high temperature to improve the electrolyte stability.

[0058] The electrolytes of Examples 1 to 6 and Comparative Examples 1 to 3 were respectively used to manufacture 4.35V LiNi 0.5 Co 0.2 Mn 0.3 / artificial graphite lithium batteries. The lithium battery performance comparison is listed in Table 2 below:

[0059] Table 2. Lithium Battery Performance Comparison

[0060]

[0061]

[0062] As can be seen from Table 2, the battery performances of Examples 1-6 are significantly better than those of Comparative Examples 1-3. Considering the comprehensive electrolyte stability and battery performance, Example 4 is the optimal solution.

[0063] In addition, in combination with Figures 1-5 As shown, in the present invention, Compound A introduces isocyanate groups on the basis of hexamethylene, which can form a good passivation film on the surfaces of the positive and negative electrodes of lithium batteries, so as to well protect the surfaces of the positive and negative electrodes. Isocyanate can consume trace moisture, react with HF, inhibit PF5 generated by the hydrolysis of LiPF6, and can reduce the catalytic effect of PF5 on DTD. When the content of Compound A is less than 0.1%, the film-forming effect of the SEI film at the electrode interface is poor, and it cannot well protect the electrode surface, and the inhibitory effect on PF5 is not obvious. When the content of Compound A is greater than 1%, the isocyanate group (-N=C=O) will chemically react with the double bond (-C=C-) in vinylene carbonate at low temperature, resulting in serious lithium precipitation at low temperature of the battery and deteriorating the low-temperature discharge capacity.

[0064] In the present invention, Compound B is used as an additive to improve the low-temperature performance of Compound A. Its sulfoxide can first react with the double bond of vinylene carbonate to passivate the activity, inhibit the reaction of the isocyanate group, and reduce the influence on the low-temperature performance. When the content of Compound B is less than 0.1%, the effect of inhibiting the isocyanate group is not obvious. When the content of Compound B is greater than 3%, the viscosity of the electrolyte will increase, and the migration of lithium ions will become difficult.

[0065] Compared with the prior art, through the combined action of Compound A and Compound B, the present invention effectively improves the decomposition of DTD at high temperature without affecting the high-temperature and low-temperature performances of the battery, and reduces the costs of the electrolyte during storage, transportation and production.

[0066] The above is only the preferred embodiment of the present invention, and it is not a limitation to any form and essence of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention. For those skilled in the art, without departing from the spirit and scope of the present invention, any equivalent changes made by using the technical content disclosed above, such as slight modifications, decorations and evolutions, are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments according to the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A non-aqueous electrolyte for a lithium-ion battery, characterized in that, The raw materials of the non-aqueous electrolyte of the lithium-ion battery include: an electrolyte, a non-aqueous organic solvent, and an additive. The additive includes Compound A, Compound B, vinylene carbonate, 1,3-propane sultone, and ethylene sulfate; The general formula of Compound A is: wherein, R1 and R2 are isocyanates; The general formula of Compound B is: wherein, R1' is a sulfur oxide; Based on the electrolyte mass being 100%, the content of the additive accounts for 1.5% - 5% of the electrolyte.

2. The non-aqueous electrolyte for a lithium ion battery according to claim 1, characterized in that Based on the electrolyte mass being 100%, Compound A accounts for 0.1% - 1% of the electrolyte, Compound B accounts for 0.1% - 3% of the electrolyte, vinylene carbonate accounts for 1.5% of the electrolyte, 1,3-propane sultone accounts for 1% of the electrolyte, and ethylene sulfate accounts for 2% of the electrolyte.

3. The non-aqueous electrolyte for a lithium-ion battery according to claim 1, wherein Based on the electrolyte mass being 100%, Compound A accounts for 0.1% - 0.5% of the electrolyte, Compound B accounts for 0.1% - 1% of the electrolyte, vinylene carbonate accounts for 1.5% of the electrolyte, 1,3-propane sultone accounts for 1% of the electrolyte, and ethylene sulfate accounts for 2% of the electrolyte.

4. The non-aqueous electrolyte for a lithium ion battery according to claim 1, wherein The electrolyte includes one or a combination of several of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(fluorosulfonyl)imide. Based on the electrolyte mass being 100%, the electrolyte accounts for 10% - 14.5% of the electrolyte.

5. The non-aqueous electrolyte for a lithium-ion battery according to claim 1, characterized in that, The non-aqueous organic solvent includes a mixture of two or more of EC, EMC, DEC, DMC, and PC. The non-aqueous organic solvent accounts for 81.5% - 83% of the electrolyte.

6. The non-aqueous electrolyte for a lithium ion battery according to any one of claims 1 to 5, characterized in that, The additive is a composition of Compound A, Compound B, vinylene carbonate, 1,3-propane sultone, and ethylene sulfate.

7. The non-aqueous electrolyte for a lithium ion battery according to claim 6, characterized in that, Compound A is hexamethylene diisocyanate.

8. The non-aqueous electrolyte for a lithium ion battery according to claim 6, wherein Compound B is triethylamine trioxide sulfur.

9. The non-aqueous electrolyte for a lithium ion battery according to claim 4, characterized in that, The electrolyte is LiPF6 or LiFSI.

10. A lithium-ion battery, characterized in that, It includes the non-aqueous electrolyte of the lithium-ion battery according to any one of claims 1 - 9.

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