CN113140790A - High-nickel/graphite system lithium ion battery electrolyte - Google Patents
High-nickel/graphite system lithium ion battery electrolyte Download PDFInfo
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- CN113140790A CN113140790A CN202010053657.XA CN202010053657A CN113140790A CN 113140790 A CN113140790 A CN 113140790A CN 202010053657 A CN202010053657 A CN 202010053657A CN 113140790 A CN113140790 A CN 113140790A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0037—Mixture of solvents
- H01M2300/0042—Four or more solvents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a high nickel/graphite system lithium ion battery electrolyte, and belongs to the technical field of lithium ion batteries. The electrolyte comprises electrolyte lithium salt, a non-aqueous organic solvent and an additive; wherein the additive comprises a borate compound additive A and a conventional film forming additive. The electrolyte adopts the borate compound as an additive and the lithium bis (fluorosulfonyl) imide as a main salt, so that the high-temperature cycle performance of the high-nickel/graphite system lithium ion battery under the extreme condition of 60 ℃ is improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-nickel/graphite system lithium ion battery electrolyte.
Background
With the rapid development of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), the energy density, cycle life, and safety requirements of Lithium Ion Batteries (LIBs) are continuously increasing. However, in a traditional electrolyte system, the ternary cathode material can generate severe structural change and interface side reaction at ultrahigh temperature, which brings great challenges to practical application, especially the cycle life and safety of the high-nickel ternary material.
The current solutions are mainly of two kinds: one method is to modify the ternary positive electrode material, such as ion doping, surface coating of the material, and the like. Another approach is to develop new electrolytes. Compared with the high-temperature electrolyte and the lithium ion battery of the Chinese patent application CN107240717A, the electrolyte adopts borate compound as the electrolyte additive and lithium hexafluorophosphate (LiPF)6) The high temperature performance of the electrolyte is improved for lithium salt, but the electrolyte is not suitable for ultra high temperature (60 ℃) conditions due to poor thermal stability of lithium hexafluorophosphate.
Disclosure of Invention
The invention aims to provide a high-nickel/graphite system lithium ion battery electrolyte, which adopts borate compounds as additives and lithium bis (fluorosulfonyl) imide (LiFSI) as a main salt, and improves the high-temperature cycle performance of the high-nickel/graphite system lithium ion battery under the extreme condition of 60 ℃.
In order to achieve the above object, the present invention provides a high nickel/graphite system lithium ion battery electrolyte comprising an electrolyte lithium salt, a non-aqueous organic solvent and an additive; wherein the additive comprises a borate compound additive A and a conventional film forming additive; the structural formula of the borate compound additive A is shown as the formula I:
wherein R is1、R2、R3、R4Are each independently selected from a hydrogen atom, a halogen atom, C1-C12Straight or branched alkyl, C1-C12Straight-chain or branched alkoxy, amino, C2-C12Straight-chain or branched alkenyl radical, C2-C12Straight or branched alkynyl, and C substituted by halogen atom1-C12Straight or branched alkyl, C substituted by halogen atoms1-C12Straight or branched alkoxy, amino, C substituted by halogen atoms2-C12Straight or branched alkenyl, C substituted by halogen atoms2-C12Any one of linear or branched alkynyl; r5Is selected from C2-C12Straight-chain or branched alkenyl, C2-C12Straight or branched alkynyl, and C substituted by halogen atom2-C12Straight-chain or branched alkenyl, C2-C12Any one of linear or branched alkynyl groups.
Preferably, R1、R2、R3、R4Are each independently selected from C1-C3A linear or branched alkyl group; r5Is selected from C2-C4Straight-chain or branched alkenyl, C2-C4Any one of linear or branched alkynyl groups.
Preferably, the borate compound additive A is selected from at least one of A1 and A2, wherein the structural formulas of A1 and A2 are as follows:
preferably, the borate compound additive A accounts for 0.1-3% of the total mass of the electrolyte.
Preferably, the conventional film-forming additive is selected from difluorophosphate (LiPO)2F2) At least one of ethylene sulfate (DTD), fluoroethylene carbonate (FEC), Vinylene Carbonate (VC) and Propylene Sulfite (PS).
Preferably, the conventional film forming additive accounts for 3-5% of the total mass of the electrolyte.
Preferably, the electrolyte lithium salt is lithium bis-fluorosulfonylimide (LiFSI) and lithium hexafluorophosphate (LiPF)6) A mixture of (a); among them, lithium bis (fluorosulfonyl) imide (LiFSI) is used as a main salt.
More preferably, the lithium bis (fluorosulfonyl) imide salt (LiFSI) accounts for 8-12% of the total mass of the electrolyte, and the lithium hexafluorophosphate (LiPF)6) Accounting for 0.5-3% of the total mass of the electrolyte.
Preferably, the non-aqueous organic solvent is selected from at least one of carbonate compounds.
The carbonate compound comprises cyclic carbonate and chain carbonate, wherein the cyclic carbonate comprises Ethylene Carbonate (EC) and Propylene Carbonate (PC), and the chain carbonate comprises diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC).
Further preferably, the non-aqueous organic solvent is a mixture of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC); wherein the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate is 2-3: 0.2-0.7: 5.5-6.5: 0.8 to 1.2.
The preparation method of the high nickel/graphite system lithium ion battery electrolyte comprises the following steps:
preparing a solvent, adding electrolyte lithium salt into the solvent, uniformly mixing, adding a conventional film-forming additive, and finally adding a borate compound additive A, and uniformly mixing to obtain the electrolyte.
The invention has the beneficial effects that:
compared with the prior art, the borate compound additive A adopted by the electrolyte has more stable chemical structure and physical properties, carbon-carbon double bonds in the additive A can be reduced and oxidized on the surfaces of a positive electrode and a negative electrode to generate a stable interfacial film (SEI/CEI), and the side reaction of the electrolyte and an electrode interface under the high-temperature condition is inhibited. Meanwhile, as the borate group in the additive A is an anion receptor, and the empty p orbit of the B is in an electron-deficient state, the additive is acidic and can complex with PF6 -Or F-Increase Li+The transference number reduces the content of LiF on the surface of the electrode, thereby effectively relieving the problem of overlarge battery impedance caused by carbon-carbon double bonds in the additive A. In addition, the electrolyte of the invention uses lithium bis (fluorosulfonylimide) (LiFSI) as the electrolyteIs the main salt, and improves the thermal stability of the lithium salt. Therefore, the electrolyte of the invention improves the high-temperature cycle and high-temperature shelf performance of the high-nickel/graphite system lithium ion battery under the extreme condition of 60 ℃.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings.
FIG. 1 shows the cycle capacity retention rates of the batteries in examples 1 to 10 and comparative example 1.
FIG. 2 shows impedance maps of the batteries of examples 1 to 10 and comparative example 1.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
Example 1
This example illustrates the electrolyte for a high nickel/graphite system lithium ion battery according to the present invention. Preparing electrolyte: in a drying room with a dew point of-50 ℃, the mass ratio of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) is 2.5: 0.5: 6: 1, and then slowly adding 12 wt% of lithium bis (fluorosulfonyl) imide (LiFSI) and 0.5 wt% of lithium hexafluorophosphate (LiPF) to the solution based on the total mass of the electrolyte6) 1 wt% of difluorophosphate (LiPO) based on the total mass of the electrolyte2F2) 0.5 wt% of ethylene sulfate (DTD), 0.2 wt% of fluoroethylene carbonate (FEC), 0.3 wt% of Vinylene Carbonate (VC) and 1 wt% of Propylene Sulfite (PS), and finally 0.1 wt% of borate compound additive A with the structure shown in formula I (the specific selection of additive A is shown in Table 1) based on the total mass of the electrolyte is added, and the lithium ion battery electrolyte of example 1 is obtained after uniform stirring.
Preparing a soft package battery: stacking the prepared positive plate, the diaphragm and the negative plate in sequence, enabling the diaphragm to be positioned between the positive plate and the negative plate, and winding to obtain a bare cell; and placing the bare cell in an outer package, injecting the prepared electrolyte into the dried battery, standing, forming and grading to finish the preparation of the lithium ion soft package battery.
Examples 2 to 10 and comparative example 1
Examples 2 to 10 and comparative example 1 are the same as in example 1 except that the electrolyte composition is different from that of example 1, and are specifically shown in table 1.
TABLE 1 substances and amounts used in examples 1 to 10 and comparative example 1
The following performance tests were performed on the soft-package full cells prepared in examples 1 to 10 and comparative example 1:
(1) and (3) testing high-temperature cycle performance: at 60 ℃, the divided-capacity battery is charged to 4.2V at constant current and constant voltage according to 1C, the current is cut off at 0.05C, then the battery is discharged to 3V at constant current according to 1C, the test is stopped according to the cycle, the discharge capacity retention rate is less than or equal to 80% of the initial discharge capacity, and the calculation formula of the capacity retention rate is as follows:
capacity retention (%) — (cycle discharge capacity/first cycle discharge capacity) × 100%.
(2) And (3) high-temperature impedance testing: and at the temperature of 60 ℃, charging the battery after capacity grading to 4.2V at a constant current and a constant voltage of 1C, stopping current at 0.05C, and then discharging for 30 minutes at a constant current of 1C, wherein the battery is considered to be in a half-electric state, the frequency range is 0.01-100 KHz, and the amplitude is 5 mV.
As can be seen from the comparison of the capacity retention of fig. 1 and the impedance test of fig. 2: compared with the example 2, the impedance of the battery in the example 2 is slightly larger than that of the battery in the example 1, but the cycle capacity retention rate is higher than that of the battery in the example 1, which shows that although the impedance of the battery is slightly increased due to the increase of the additive A2 and the use amount of the conventional additive, the formation of positive and negative CEI/SEI films is more facilitated, and thus the cycle stability of the battery in the example 2 is better.
Comparing examples 3, 4 and 5, it can be seen that when LiPF is increased6When the amount of LiFSI was decreased, the battery capacity retention rate was reduced, presumably due to LiPF under high temperature conditions6Unstable decomposition.
Comparing examples 6, 7, 8 and 9, it can be seen that 9 has the highest impedance and the lowest capacity retention rate, and secondly, the performance of 7 is poor, and the reason for this is presumed to be that the battery impedance is increased and the capacity retention rate is reduced due to the excessive amount of the additive.
Comparing examples 6 and 10, it can be seen that additives a1 and a2, which act the same, do not affect the difference in cell performance.
Comparing examples 1-10 with comparative example 1, it can be seen from fig. 1 that when the basic electrolyte (comparative example 1) is used in a high-temperature high-nickel battery system, the battery capacity attenuation is severe; and the battery of comparative example 1 became soft during the cycle, it is presumed that the decomposition of the electrolyte solution under high temperature conditions causes the deterioration of the electrochemical properties. It can also be seen from fig. 2 that the resistance of the battery of comparative example 1 is the greatest, resulting in a greater polarization of the battery during use, resulting in energy loss. The difference between the batteries of examples 1-10 and comparative example 1 is that the electrolyte is different, and the cycle performance of the batteries prepared in examples 1-10 is obviously better than that of comparative example 1 under the high temperature condition of 60 ℃.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A high nickel/graphite system lithium ion battery electrolyte, characterized in that the electrolyte comprises an electrolyte lithium salt, a non-aqueous organic solvent and an additive; wherein the additive comprises a borate compound additive A and a conventional film forming additive; the structural formula of the borate compound additive A is shown as the formula I:
wherein R is1、R2、R3、R4Are each independently selected from a hydrogen atom, a halogen atom, C1-C12Straight or branched alkyl, C1-C12Straight-chain or branched alkoxy, amino, C2-C12Straight-chain or branched alkenyl radical, C2-C12Straight or branched alkynyl, and C substituted by halogen atom1-C12Straight or branched alkyl, C substituted by halogen atoms1-C12Straight or branched alkoxy, amino, C substituted by halogen atoms2-C12Straight or branched alkenyl, C substituted by halogen atoms2-C12Any one of linear or branched alkynyl; r5Is selected from C2-C12Straight-chain or branched alkenyl, C2-C12Straight or branched alkynyl, and C substituted by halogen atom2-C12Straight-chain or branched alkenyl, C2-C12Any one of linear or branched alkynyl groups.
2. The high nickel/graphite system lithium ion battery electrolyte of claim 1, wherein R is1、R2、R3、R4Are each independently selected from C1-C3A linear or branched alkyl group; r5Is selected from C2-C4Straight-chain or branched alkenyl, C2-C4Any one of linear or branched alkynyl groups.
3. The high nickel/graphite system lithium ion battery electrolyte of claim 2, wherein the borate compound additive a is selected from at least one of a1 and a2, wherein a1 and a2 have the following structural formulas:
4. the high nickel/graphite system lithium ion battery electrolyte according to claim 1, wherein the borate compound additive a accounts for 0.1 to 3% of the total mass of the electrolyte.
5. The high nickel/graphite-based lithium ion battery electrolyte of claim 1, wherein the conventional film-forming additive is selected from at least one of difluorophosphate, vinyl sulfate, fluoroethylene carbonate, vinylene carbonate, and propylene sulfite.
6. The high nickel/graphite system lithium ion battery electrolyte of claim 1, wherein the conventional film forming additive accounts for 3-5% of the total mass of the electrolyte.
7. The high nickel/graphite system lithium ion battery electrolyte of claim 1, wherein the electrolyte lithium salt is a mixture of lithium bis-fluorosulfonylimide and lithium hexafluorophosphate; wherein, lithium bis-fluorosulfonylimide is used as a main salt.
8. The high nickel/graphite-based lithium ion battery electrolyte according to claim 7, wherein the lithium bis-fluorosulfonylimide accounts for 8 to 12% of the total mass of the electrolyte, and the lithium hexafluorophosphate accounts for 0.5 to 3% of the total mass of the electrolyte.
9. The high nickel/graphite system lithium ion battery electrolyte of claim 1, wherein the non-aqueous organic solvent is selected from at least one of carbonate based compounds.
10. The high nickel/graphite system lithium ion battery electrolyte of claim 1, wherein the non-aqueous organic solvent is a mixture of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate; wherein the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate is 2-3: 0.2-0.7: 5.5-6.5: 0.8 to 1.2.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080020286A1 (en) * | 2006-07-24 | 2008-01-24 | Hiroshi Haruna | Lithium secondary battery |
| CN103518284A (en) * | 2011-05-09 | 2014-01-15 | 新神户电机株式会社 | Nonaqueous electrolyte solution and lithium ion battery |
| CN110556580A (en) * | 2019-10-15 | 2019-12-10 | 骆驼集团武汉光谷研发中心有限公司 | Start-stop battery electrolyte and lithium ion battery |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080020286A1 (en) * | 2006-07-24 | 2008-01-24 | Hiroshi Haruna | Lithium secondary battery |
| CN103518284A (en) * | 2011-05-09 | 2014-01-15 | 新神户电机株式会社 | Nonaqueous electrolyte solution and lithium ion battery |
| CN110556580A (en) * | 2019-10-15 | 2019-12-10 | 骆驼集团武汉光谷研发中心有限公司 | Start-stop battery electrolyte and lithium ion battery |
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Application publication date: 20210720 |