Non-aqueous electrolyte and lithium ion battery containing the same
By using a non-aqueous electrolyte containing cyano functional groups as an additive in lithium-ion batteries, the problem of electrode reaction at high temperatures was solved, the high-temperature storage and cycle performance of the battery was improved, the low-temperature discharge performance was enhanced, and the battery life was extended.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHUHAI SMOOTHWAY ELECTRONICS MATERIALS
- Filing Date
- 2023-05-12
- Publication Date
- 2026-06-16
AI Technical Summary
Existing lithium-ion batteries suffer from material loss and deterioration in battery performance due to the reaction between the electrodes and non-aqueous electrolytes under high temperature and high pressure conditions, which affects their service life. Furthermore, the high viscosity of additives reduces the ion transfer rate.
The non-aqueous electrolyte contains lithium salt, non-aqueous organic solvent and additives with a specific structure. The additives contain cyano functional groups, which have electronic conductivity, promote electron transfer, and adsorb cobalt ions and transfer lithium ions when forming a solid electrolyte interface film, thereby improving high-temperature storage and cycling performance.
It improves the high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries under high-voltage systems, while also improving low-temperature discharge performance and extending battery life.
Smart Images
Figure CN116470140B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a non-aqueous electrolyte and a lithium-ion battery containing the non-aqueous electrolyte. Background Technology
[0002] Rechargeable batteries include various types such as nickel-metal hydride (NiMH), nickel-cadmium (NiCd), lead-acid, and lithium-ion batteries. Among them, lithium-ion batteries are widely used due to their advantages of large capacity, fast charging speed, and high cycle life. Recent studies have shown that the main reason for the shortened lifespan of lithium-ion batteries is that the electrodes easily react with the non-aqueous electrolyte under the high temperature and pressure environment inside the battery. This reaction causes electrode material loss, electrolyte deterioration, and the gases produced by many reactions can also cause battery volume expansion. All these changes easily lead to deterioration of battery performance and shortened lifespan. Currently, stabilizing additives, such as fluorobenzene, cyclohexylbenzene, and cyclohexylfluorobenzene, are added to the non-aqueous electrolyte to inhibit the reaction between the electrodes and the non-aqueous electrolyte. However, these stabilizing additives have high viscosity, significantly reducing the fluidity of the electrolyte, thereby affecting the ion transport rate in the electrolyte and reducing battery performance. Summary of the Invention
[0003] The purpose of this invention is to provide a non-aqueous electrolyte that can improve the high-temperature storage performance and high-temperature cycling performance of lithium-ion batteries under high-voltage systems.
[0004] To achieve the above objectives, the present invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive is a compound represented by structural formula 1.
[0005]
[0006] R1, R2, and R3 are each independently selected from one of alkyl, alkynyl, alkenyl, amino, nitrile, and alkylamine.
[0007] Compared with the prior art, the non-aqueous electrolyte of the present invention includes a lithium salt, a non-aqueous organic solvent, and an additive. The additive is a compound shown in structural formula 1, which enables the non-aqueous electrolyte to remain stable under continuous high voltage. At the same time, the substance of this structure contains a cyano functional group, and the cyano group carries electrons and has electronic conductivity. Under low temperature conditions, it promotes electron transfer, thereby improving the low-temperature discharge performance of the lithium battery. At the same time, under high-temperature storage conditions, the structure containing positive and negative valences can not only adsorb cobalt ions when forming a solid electrolyte interphase (SEI) film, but also has the function of adsorbing and transferring lithium ions, which slows down lithium loss under high-temperature cycling and high-temperature storage conditions. This improves the high-temperature storage performance and high-temperature cycling performance of lithium-ion batteries under high voltage (especially at 4.53V) systems, and also improves the low-temperature discharge performance of lithium-ion batteries.
[0008] In some embodiments, R1, R2, and R3 are each independently selected from alkyl, alkynyl, and alkenyl groups having 1-4 carbon atoms, respectively; the amine group is selected from primary amine, secondary amine, tertiary amine, and quaternary amine; the nitrile group is selected from nitrile alkyl groups having 1-4 carbon atoms; and the alkylamine is selected from alkylamines having 1-6 carbon atoms.
[0009] It is understood that the alkyl groups of R1, R2, and R3, which have 1-4 carbon atoms, can be straight-chain, branched, or cyclic alkyl groups. This invention does not limit them. For example, specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, neopentyl, sec-pentyl, tert-pentyl, n-hexyl, 2-hexyl, etc., but are not limited to these.
[0010] It is understandable that R1, R2, and R3 can be the same or different, and no restrictions are imposed here.
[0011] It is understandable that R1, R2, and R3 are alkynyl groups with 1 to 4 carbon atoms, such as, but not limited to, ethynyl, propynyl, and propynyl.
[0012] It is understandable that R1, R2, and R3 are alkenyl groups with 1 to 4 carbon atoms, such as, but not limited to, vinyl, propenyl, allyl, butenyl, etc.
[0013] It is understood that the nitrile group is selected from nitrile alkyl groups having 1-4 carbon atoms. The nitrile alkyl group can be a chain nitrile alkyl group or a cyclic nitrile alkyl group. The chain nitrile alkyl group can be branched or straight-chain. Preferably, a nitrile alkyl group having 1-4 carbon atoms is selected. As an example, the nitrile alkyl group can be, but is not limited to, nitrile methyl or nitrile ethyl.
[0014] It is understood that the alkylamine is selected from alkylamines having 1 to 6 carbon atoms. By way of example, the alkylamine is selected from methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine and n-butylamine, but is not limited thereto.
[0015] In some embodiments, the compound represented by structural formula 1 is selected from at least one of compound 1, compound 3, and compound 4.
[0016]
[0017]
[0018] In some embodiments, the mass percentage of the additive of the present invention in the non-aqueous electrolyte is 0.05-5%, preferably 0.1-4%, and more preferably 0.1-3%. As an example, the mass percentage of the additive in the non-aqueous electrolyte may be, but is not limited to, 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%.
[0019] In some embodiments, the mass percentage of the lithium salt in the non-aqueous electrolyte is 5-20%, preferably 8-15%, and more preferably 10-15%. As an example, the mass percentage of the lithium salt in the non-aqueous electrolyte may be, but is not limited to, 10%, 11%, 12%, 13%, 14%, or 15%.
[0020] In some embodiments, the lithium salt of the present invention is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate, lithium difluorooxalatoborate, lithium difluorodi(oxalato)phosphate, and lithium bis(fluorosulfonyl)imide. As an example, the lithium salt is lithium hexafluorophosphate (LiPF6) or lithium bis(oxalato)borate (LiBOB). In a preferred embodiment, the lithium salt is a mixture of two or more compounds, such as a mixture of lithium hexafluorophosphate (LiPF6) and lithium bis(oxalato)borate (LiBOB), or a mixture of lithium hexafluorophosphate and lithium trifluoromethanesulfonate, which can achieve better high-temperature cycling performance.
[0021] In some embodiments, the non-aqueous organic solvent of the present invention is at least one of chain carbonates, cyclic carbonates and carboxylic acid esters. Further, the non-aqueous organic solvent is selected from at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), butyl acetate (n-Ba), γ-butyrolactone (γ-Bt), n-propyl propionate (n-PP), ethyl propionate (EP) and ethyl butyrate (Eb).
[0022] In some embodiments, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte of the present invention is 65-90%, preferably, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte is 70-88%, more preferably, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte is 80-88%. As an example, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte can be but is not limited to 80%, 82%, 85%, 86%, 87%, 88%.
[0023] Correspondingly, the present invention also provides a lithium-ion battery, including a positive electrode material, a negative electrode material and the above non-aqueous electrolyte. Because the lithium-ion battery contains the non-aqueous electrolyte, it has good high-temperature storage performance, high-temperature cycle performance and low-temperature discharge performance.
[0024] In some embodiments, the positive electrode material is at least one of lithium cobalt oxide, nickel cobalt manganese oxide or nickel cobalt aluminum oxide.
[0025] Among them, the chemical formula of nickel cobalt manganese oxide is LiNi
[0026] Co y Mn z M (1-x-y-z) O2; the chemical formula of nickel cobalt aluminum oxide is LiNi x Co y Al z N (1-x-y-z) O2, where M and N are each independently selected from at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z ≤ 1; the chemical formula of lithium cobalt oxide is LiCoO2.
[0026] In some embodiments, the negative electrode material of the present invention is selected from at least one of artificial graphite, natural graphite, lithium titanate, silicon-carbon composite material and silicon monoxide. Detailed implementation manners
[0027] To better illustrate the purpose, technical solution, and beneficial effects of the present invention, specific embodiments are provided below to further illustrate the purpose, technical solution, and beneficial effects of the present invention. However, these embodiments do not constitute any limitation on the present invention. Unless otherwise specified, specific conditions may be followed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products that can be obtained commercially.
[0028] Example 1
[0029] (1) Preparation of non-aqueous electrolyte
[0030] In an argon-filled glove box (O2 < 1 ppm, H2O < 1 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a weight ratio of EC:EMC:DEC = 1:1:1 to obtain 87 g of non-aqueous organic solvent. Then, 0.5 g of compound 1 was added as an additive, dissolved, and stirred thoroughly. After that, 12.5 g of lithium hexafluorophosphate was added and mixed evenly to obtain a non-aqueous electrolyte.
[0031] (2) Preparation of positive electrode
[0032] LiCoO2, binder PVDF and conductive agent SuperP are mixed evenly at a mass ratio of 95:1:4 to prepare a lithium-ion battery positive electrode slurry with a certain viscosity. The mixed slurry is coated on both sides of aluminum foil, dried and rolled to obtain the positive electrode sheet.
[0033] (3) Preparation of negative electrode
[0034] Artificial graphite, conductive agent SuperP, thickener CMC, and binder SBR (styrene-butadiene rubber latex) are mixed in a mass ratio of 95:1.5:1.0:2.5 to form a slurry. The mixture is then coated on both sides of a copper foil, dried, and rolled to obtain the negative electrode sheet.
[0035] (4) Preparation of lithium-ion batteries
[0036] The positive electrode, separator, and negative electrode are wound together to form a soft-pack battery cell, which is then packaged in a polymer aluminum-plastic film and filled with the prepared non-aqueous electrolyte for lithium-ion batteries. After formation, capacity testing, and other processes, a lithium-ion battery with a capacity of 4000mAh is produced.
[0037] The non-aqueous electrolyte formulations for Examples 2-9 are shown in Table 1. The steps for preparing the electrolyte and manufacturing the battery are the same as in Example 1.
[0038] Table 1 Formulation of non-aqueous electrolyte
[0039]
[0040]
[0041] The lithium-ion batteries prepared in Examples 1 to 9 were subjected to low-temperature discharge performance tests, high-temperature storage tests, and high-temperature cycle tests, respectively. The specific test conditions are as follows, and the performance test results are shown in Table 2.
[0042] Low-temperature discharge performance test of lithium-ion batteries
[0043] Under normal temperature (25℃) conditions, a lithium-ion battery is subjected to a 0.5C / 0.5C charge and discharge cycle (discharge capacity denoted as C0), with an upper limit voltage of 4.535V. Then, the battery is charged to 4.535V under constant current and constant voltage conditions at 0.5C. The lithium-ion battery is then placed in a -20℃ low-temperature chamber for 4 hours and discharged at -20℃ at 0.5C (discharge capacity denoted as C1). The low-temperature discharge rate of the lithium-ion battery is calculated using the following formula:
[0044] Low-temperature discharge rate = (C1 / C0) * 100%
[0045] High-Temperature Storage Performance Test of Lithium-ion Batteries
[0046] Under normal temperature (25℃) conditions, a lithium-ion battery was subjected to one 0.3C / 0.3C charge and discharge cycle (battery discharge capacity recorded as C0), with an upper limit voltage of 4.535V. The battery was then placed in a 60℃ oven for 7 days, removed, and placed in a 25℃ environment for a 0.3C discharge, with the discharge capacity recorded as C1. Finally, the lithium-ion battery was subjected to another 0.3C / 0.3C charge and discharge cycle (battery discharge capacity recorded as C2). The capacity retention rate and capacity recovery rate of the lithium-ion battery were calculated using the following formulas:
[0047] Capacity retention rate = (C1 / C0) * 100%
[0048] Capacity recovery rate = (C2 / C0) * 100%
[0049] High-temperature cycle performance test of lithium-ion batteries
[0050] The lithium-ion battery was placed in a 45°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1C until the voltage reached 4.535V, followed by constant voltage charging at 4.535V until the current reached 0.05C. Next, it was discharged at a constant current of 1C until the voltage reached 3.0V. The first discharge capacity was recorded as C0. This constitutes one charge-discharge cycle. Then, 300 cycles of 1C / 1C charging and discharging were performed at 45°C, and the discharge capacity was recorded as C1. The capacity retention rate of the lithium-ion battery was calculated using the following formula.
[0051] Capacity retention rate = (C1 / C0) * 100%
[0052] Table 2. Performance test results of lithium-ion batteries
[0053]
[0054] As shown in Table 2, the lithium-ion batteries of Examples 1-9 exhibit better high-temperature storage performance, high-temperature cycling performance, and low-temperature discharge performance than Comparative Example 1. This is because the additive is a compound represented by structural formula 1, which enables the non-aqueous electrolyte to remain stable under continuous high voltage. Furthermore, this structure contains a cyano functional group, and the cyano group carries electrons, possessing electronic conductivity. Under low-temperature conditions, it promotes electron transfer, thereby improving the low-temperature discharge performance of the lithium battery. Simultaneously, under high-temperature storage conditions, the structure containing both positive and negative valences allows it to not only adsorb cobalt ions but also adsorb and transfer lithium ions when forming a solid electrolyte interphase (SEI) film, mitigating lithium loss under high-temperature cycling and storage conditions. This further enhances the high-temperature storage and cycling performance of the lithium-ion battery under high voltage (especially at 4.53V) systems, while also improving its low-temperature discharge performance.
[0055] The data results of Examples 2 and 7-8 demonstrate that the combination of cyano and amino groups can enhance the performance of the main structure and further improve high-temperature performance.
[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A non-aqueous electrolyte, characterized in that, It includes lithium salts, non-aqueous organic solvents, and additives, wherein the additives are compounds as shown in structural formula 1. R1, R2, and R3 are each independently selected from one of alkyl, alkynyl, alkenyl, amino, nitrile, and alkylamine.
2. The non-aqueous electrolyte as described in claim 1, characterized in that, R1, R2, and R3 are each independently selected from alkyl, alkynyl, and alkenyl groups with 1-4 carbon atoms; the amine group is selected from primary, secondary, tertiary, and quaternary amines; the nitrile group is selected from nitrile alkyl groups with 1-4 carbon atoms; and the alkylamine is selected from alkylamines with 1-6 carbon atoms.
3. The non-aqueous electrolyte as described in claim 1, characterized in that, The compound represented by structural formula 1 is selected from at least one of compound 1, compound 2, compound 3, and compound 4.
4. The non-aqueous electrolyte as described in claim 1, characterized in that, The additive constitutes 0.05% to 5% of the mass of the non-aqueous electrolyte.
5. The non-aqueous electrolyte as described in claim 1, characterized in that, The lithium salt constitutes 5-20% of the mass of the non-aqueous electrolyte.
6. The non-aqueous electrolyte as described in claim 1, characterized in that, The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate-borate), lithium difluorophosphate, lithium difluorooxalate-borate, lithium difluorodioxalate-phosphate, and lithium bis(oxalate-imide).
7. The non-aqueous electrolyte as described in claim 1, characterized in that, The non-aqueous organic solvent is at least one of chain carbonates, cyclic carbonates, and carboxylic acid esters.
8. The non-aqueous electrolyte as described in claim 7, characterized in that, The non-aqueous organic solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, butyl acetate, γ-butyrolactone, propyl propionate, ethyl propionate, and ethyl butyrate.
9. A lithium-ion battery, comprising a positive electrode material and a negative electrode material, characterized in that, It also includes the non-aqueous electrolyte as described in any one of claims 1 to 8.
10. The lithium-ion battery as described in claim 9, characterized in that, The cathode material is at least one of lithium cobalt oxide, nickel cobalt manganese oxide, or nickel cobalt aluminum oxide.