Low-temperature fast-charging electrolyte as well as preparation method and application thereof
By using a low-temperature fast charging solution containing soluble lithium salts, ester solvents and low-temperature additives in lithium-ion batteries, the problem of degradation of lithium batteries under low temperature conditions is solved, and the rate performance and circulation performance are significantly improved. in extremely low temperature environment.
Patent Information
- Application Number
- CN202411614418.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-02-18
AI Technical Summary
Lithium-ion batteries have lower ion conductivity under low temperature conditions, difficult desolution of solvents and Li+ binding force, and insufficient SEI generation on the interface, resulting in low capacity retention and short cycle life, limiting the application of lithium batteries in low temperature environments.
A low-temperature fast charging electrolyte is used, and its composition includes soluble lithium salts, ester solvents and low-temperature additives. Through appropriate proportions and combinations, the desolution barrier of Li+ and the stability of the SEI film are improved.
It effectively improves the rate performance and cycle performance of lithium batteries under low temperature conditions, ensuring that good capacity retention and battery cycle life can be maintained under low temperature conditions below -40℃.
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Figure CN119481281A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrolytes, and in particular to a low-temperature fast-charging electrolyte and a preparation method and application thereof. Background Art
[0002] With the rapid development of portable electronic devices, electric vehicles, energy storage systems and other fields, the performance requirements for lithium-ion batteries are constantly increasing. In practical applications, lithium-ion batteries often face various complex environmental conditions, among which the impact of low temperature environment on battery performance is particularly prominent. Whether in cold areas at high latitudes or in some special low-temperature working scenarios, such as polar scientific research, aerospace and other fields, strict requirements are placed on the performance of lithium-ion batteries at low temperatures. The development of electric vehicles also faces the challenge of low temperatures. In the cold winter, the cruising range of lithium-ion batteries drops significantly, the charging speed slows down, and they may even fail to start. This brings great inconvenience to users and restricts the promotion of electric vehicles in cold areas.
[0003] The electrolyte is called the "blood" of lithium-ion batteries. It plays a vital role in the performance of lithium-ion batteries, especially the structure and properties of the interface between the electrode and the electrolyte. At present, the conventional lithium-ion battery electrolyte has the problems of decreased ion conductivity, solvent and Li + The strong binding force makes it difficult to dissolve, and the SEI formation at low temperatures is not stable enough, which leads to low capacity retention and short cycle life of lithium batteries at low temperatures, greatly limiting the application of lithium-ion batteries in low-temperature environments. In particular, at temperatures below -20°C, the interfacial impedance of the battery increases significantly, the capacity decays severely, and causes huge energy loss in the battery.
[0004] Therefore, developing a lithium-ion low-temperature electrolyte that can effectively improve the capacity retention rate and cycle life of lithium batteries under low temperature conditions has become a technical problem that needs to be solved urgently. Summary of the invention
[0005] The purpose of the present invention is to provide a low-temperature fast-charge electrolyte and a preparation method and application thereof. By using the low-temperature fast-charge electrolyte prepared by the present invention, the rate performance and cycle performance of the battery under low temperature conditions can be effectively improved.
[0006] The purpose of the present invention can be achieved by the following technical solutions:
[0007] A low-temperature fast-charge electrolyte, in terms of weight percentage, the low-temperature fast-charge electrolyte comprises:
[0008] Soluble lithium salt 5% ~ 20%,
[0009] Ester solvents 70% to 90%,
[0010] Low temperature additive 0.5% ~ 10%.
[0011] Furthermore, the soluble lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate.
[0012] As a preferred technical solution, the soluble lithium salt is lithium bis(trifluoromethanesulfonyl imide), and the concentration of the soluble lithium salt is 0.1 to 3.0 mol / L.
[0013] Further, the ester solvent is selected from a mixed solvent of any two combinations of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl butyrate, ethyl difluoroacetate, ethyl trifluoroacetate, ethyl trifluoroformate, methyl trifluoroacetate, butyl trifluoroacetate, fluoroethylene carbonate, difluoroethylene carbonate or ethyl methyl trifluorocarbonate.
[0014] Furthermore, in the above, the volume ratio of the two ester solvents is 1:9 to 9:1.
[0015] As a preferred technical solution, the ester solvent is a mixed solvent of fluoroethylene carbonate and ethyl difluoroacetate.
[0016] Furthermore, the low-temperature additive is selected from any one or more of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluorooxalatophosphate, lithium bis(oxalatodifluorophosphate), lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide or lithium 2-fluoromalonate difluoroborate.
[0017] As a preferred technical solution, the low-temperature additive is lithium difluorophosphate.
[0018] The present invention also provides a method for preparing a low-temperature fast-charge electrolyte, the specific steps of which are as follows:
[0019] Take the two ester solvents and stir to mix; then add the soluble lithium salt and stir until it is completely dissolved; finally add the low-temperature additive and mix evenly to obtain the low-temperature fast-charge electrolyte.
[0020] Furthermore, the stirring time is 10 to 20 minutes.
[0021] Furthermore, the entire process of preparing the low-temperature fast-charge electrolyte is carried out in a glove box filled with argon (water content ≤ 0.1 ppm, oxygen content ≤ 0.1 ppm).
[0022] A lithium-ion battery comprises: a positive electrode material, a negative electrode material and the above-mentioned low-temperature fast-charging electrolyte.
[0023] Furthermore, the positive electrode material is NCM622 (LiNi 0.6 Mn 0.2 Co 0.2 O2) pole piece.
[0024] Furthermore, the negative electrode material is graphite.
[0025] Furthermore, the application temperature of the lithium-ion battery is -40°C to 25°C.
[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0027] The present invention improves the Li + The desolvation barrier effectively decouples Li + The combination with the solvent generates a SEI film rich in LiF and other inorganic substances. Compared with the traditional EC-based electrolyte, the lithium battery using the electrolyte of the present invention can have a good capacity retention rate and battery cycle life at low temperatures as low as -40°C.
[0028] The present invention improves the ionic conductivity of the electrolyte at low temperature by adding a lithium fluorophosphate additive, and promotes the production of a thin and strong SEI film. After the low-temperature fast-charging electrolyte is applied to a lithium ion battery, it has good rate performance under low temperature conditions as low as -40°C.
[0029] The present invention effectively improves the oxidation resistance of the SEI film of the low-temperature fast-charging electrolyte during the initial formation by jointly using solvent components such as fluorocarbonate, thereby significantly improving the cycle stability of the lithium-ion battery under high voltage, while also having excellent charge and discharge performance, being suitable for high-voltage positive electrode materials, and being conducive to the development and promotion of high-energy-density lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 This is a comparison chart of the rate performance of the low-temperature fast-charge electrolyte prepared in Example 1 and the electrolytes prepared in Comparative Examples 1 to 2;
[0031] Figure 2 This is a comparison chart of the low-temperature fast-charge electrolyte prepared in Example 1 and the electrolyte prepared in Comparative Examples 1-2 at low temperature rate performance;
[0032] Figure 3 This is a comparison chart of the cycle performance of the low-temperature fast-charge electrolyte prepared in Example 1 and the electrolyte prepared in Comparative Examples 1-2 at 0.2C;
[0033] Figure 4This is a comparison chart of the cycle performance of the low-temperature fast-charge electrolyte prepared in Example 1 and the electrolyte prepared in Comparative Examples 1 to 2 at 4C. DETAILED DESCRIPTION
[0034] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0035] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.
[0036] Example 1
[0037] This embodiment provides a method for preparing a low-temperature fast-charge electrolyte, and the specific steps are as follows:
[0038] In a closed environment with a water oxygen content of less than or equal to 0.1ppm, fluoroethylene carbonate (FEC) and ethyl difluoroacetate (DFEA) are mixed in a volume ratio of 3:7; 1mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added and stirred to completely dissolve it until the system becomes clear and transparent; then 0.5wt.% of lithium difluorophosphate is added and stirred to be fully mixed, and finally a low-temperature fast-charge electrolyte is prepared, which is recorded as 1M LiTFSI-FEC / DFEA (3:7in vol.)+0.5wt.%LiPO2F2.
[0039] In addition, this embodiment provides an application of a low-temperature fast-charge electrolyte, and a Li||NCM622 full battery assembled using the 1MLiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the specific steps are as follows:
[0040] Using NCM622(LiNi 0.6 Mn 0.2 Co 0.2 O2) electrode was used as the positive electrode and a button cell was assembled with a graphite negative electrode. The electrolyte was the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the electrochemical performance of the full battery was tested.
[0041] Example 2
[0042] This embodiment provides a method for preparing a low-temperature fast-charge electrolyte, and the specific steps are as follows:
[0043] In a closed environment with a water and oxygen content of less than or equal to 0.1 ppm, fluoroethylene carbonate (FEC) and ethyl difluoroacetate (DFEA) are mixed in a volume ratio of 3:7; 1M lithium bistrifluoromethanesulfonyl imide (LiTFSI) is added and stirred to completely dissolve it until the system becomes clear and transparent; then 2wt.% of lithium difluorophosphate is added and stirred to be fully mixed, and finally a low-temperature fast-charge electrolyte is prepared, which is recorded as 1MLiTFSI-FEC / DFEA (3:7 in vol.) + 2wt.%LiPO2F2.
[0044] In addition, this embodiment provides an application of a low-temperature fast-charge electrolyte, and a Li||NCM622 full battery assembled using the 1MLiTFSI-FEC / DFEA (3:7 in vol.) + 2wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the specific steps are as follows:
[0045] Using NCM622(LiNi 0.6 Mn 0.2 Co 0.2 O2) electrode was used as the positive electrode and a button cell was assembled with a graphite negative electrode. The electrolyte was the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 2wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the electrochemical performance of the full battery was tested.
[0046] Example 3
[0047] This embodiment provides a method for preparing a low-temperature fast-charge electrolyte, and the specific steps are as follows:
[0048] In a closed environment with a water and oxygen content of less than or equal to 0.1ppm, fluoroethylene carbonate (FEC) and ethyl difluoroacetate (DFEA) are mixed in a volume ratio of 3:7; 1mol / L lithium bistrifluoromethanesulfonyl imide (LiTFSI) is added and stirred to completely dissolve it until the system becomes clear and transparent; then 5wt.% of lithium difluorophosphate is added and stirred to be fully mixed, and finally a low-temperature fast-charge electrolyte is prepared, which is recorded as 1MLiTFSI-FEC / DFEA (3:7in vol.)+5wt.%LiPO2F2.
[0049] In addition, this embodiment provides an application of a low-temperature fast-charge electrolyte, and a Li||NCM622 full battery assembled using the 1MLiTFSI-FEC / DFEA (3:7 in vol.) + 5wt.%LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the specific steps are as follows:
[0050] Using NCM622(LiNi 0.6 Mn0.2 Co 0.2 O2) electrode was used as the positive electrode and a button cell was assembled with a graphite negative electrode. The electrolyte was the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1, and the electrochemical performance of the full battery was tested.
[0051] Comparative Example 1
[0052] This comparative example provides a method for preparing an electrolyte, and the specific steps are as follows:
[0053] In a closed environment with a water oxygen content of less than or equal to 0.1 ppm, ethylene carbonate (EC) and diethyl carbonate (DEC) are uniformly mixed in a volume ratio of 1:1; 1 mol / L lithium hexafluorophosphate (LiPF6) is added and stirred to completely dissolve it, and finally an electrolyte is prepared, which is recorded as 1M LiPF6-EC / DEC (1:1 in vol.).
[0054] In addition, this comparative example provides an application of an electrolyte, and a Li||NCM622 full battery is assembled using the 1MLiPF6-EC / DEC (1:1 in vol.)) electrolyte prepared in Comparative Example 1, and the specific steps are as follows:
[0055] NCM622 pole piece was used as the positive electrode, and button-type battery was assembled with graphite negative pole piece. The electrolyte was 1M LiPF6-EC / DEC (1:1 in vol.) electrolyte prepared in Comparative Example 1, and the electrochemical performance of the whole battery was tested.
[0056] Comparative Example 2
[0057] This comparative example provides a method for preparing an electrolyte, and the specific steps are as follows:
[0058] In a closed environment with a water oxygen content of less than or equal to 0.1 ppm, fluoroethylene carbonate (FEC) and ethyl difluoroacetate (DFEA) are uniformly mixed in a volume ratio of 3:7 and stirred; 1 mol / L lithium bistrifluoromethanesulfonyl imide (LiTFSI) is added and stirred to completely dissolve it, and finally an electrolyte is prepared, which is recorded as 1MLiTFSI-FEC / DFEA (3:7 invol.).
[0059] In addition, this comparative example provides an application of an electrolyte, and a Li||NCM622 full battery is assembled using the 1MLiTFSI-FEC / DFEA (3:7 in vol.) electrolyte prepared in Comparative Example 2, and the specific steps are as follows:
[0060] The NCM622 electrode was used as the positive electrode and a button cell was assembled with a graphite negative electrode. The 1M LiTFSI-FEC / DFEA (3:7 in vol.) electrolyte prepared in Comparative Example 2 was selected as the electrolyte to test the electrochemical performance of the full cell.
[0061] The performance test results of the low-temperature fast-charge electrolyte prepared in Example 1 and the electrolyte prepared in Comparative Examples 1-2 are as follows:
[0062] from Figure 1 It can be seen that the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 electrolyte prepared in Example 1 is at room temperature 6C (1C = 372mA g -1 ) and the discharge capacity at a current density of 10C are 240mAh / g and 150mAh / g, respectively, which are greatly improved compared with Comparative Examples 1 and 2.
[0063] from Figure 2 It can be seen that the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1 has a discharge capacity of 275mAh / g and 140mAh / g at -20℃ and -30℃ at a current density of 0.2C, which is greatly improved compared with Comparative Examples 1 and 2.
[0064] from Figure 3 It can be seen that the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1 retains a discharge capacity of 360mAh / g after 200 cycles at a current density of 0.2C, and the capacity retention rate reaches 96%, which is greatly improved compared with Comparative Examples 1 and 2.
[0065] from Figure 4 It can be seen that the 1M LiTFSI-FEC / DFEA (3:7 in vol.) + 0.5wt.% LiPO2F2 low-temperature fast-charge electrolyte prepared in Example 1 retains a discharge capacity of 250mAh / g after 3000 cycles at a current density of 4C, and the capacity retention rate reaches 68%, which is greatly improved compared with Comparative Examples 1 and 2.
[0066] In summary, the low-temperature rate performance and low-temperature cycle performance of Example 1 with the addition of the low-temperature additive are significantly improved compared with those of Comparative Examples 1 and 2, indicating that the low-temperature additive can effectively improve the low-temperature electrical performance of the lithium battery.
[0067] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A low-temperature fast-charge electrolyte, characterized in that: In terms of weight percentage, the low-temperature fast-charge electrolyte comprises: Soluble lithium salt 5% ~ 20%, Ester solvents 70% to 90%, Low temperature additive 0.5% ~ 10%.
2. A low-temperature fast-charge electrolyte according to claim 1, characterized in that: The soluble lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate.
3. A low-temperature fast-charge electrolyte according to claim 1, characterized in that: The ester solvent is selected from a mixed solvent of any two combinations of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl butyrate, ethyl difluoroacetate, ethyl trifluoroacetate, ethyl trifluoroformate, methyl trifluoroacetate, butyl trifluoroacetate, fluoroethylene carbonate, difluoroethylene carbonate or ethyl methyl trifluorocarbonate.
4. A low-temperature fast-charge electrolyte according to claim 3, characterized in that: The volume ratio of the two ester solvents is 1:9 to 9:
1.
5. A low-temperature fast-charge electrolyte according to claim 1, characterized in that: The low-temperature additive is selected from any one or more of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluorooxalatophosphate, lithium bis(oxalatodifluorophosphate), lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide or lithium 2-fluoromalonatedifluoroborate.
6. A method for preparing a low-temperature fast-charge electrolyte as claimed in any one of claims 1 to 5, characterized in that: The specific steps are as follows: Take the two ester solvents and stir to mix; then add the soluble lithium salt and stir until it is completely dissolved; finally add the low-temperature additive and mix evenly to obtain the low-temperature fast-charge electrolyte.
7. The method for preparing a low-temperature fast-charge electrolyte according to claim 6, characterized in that: The stirring time is 10 to 20 minutes.
8. A lithium ion battery, characterized in that: The lithium-ion battery comprises: a positive electrode material, a negative electrode material and a low-temperature fast-charging electrolyte as described in any one of claims 1-5.
9. A lithium ion battery according to claim 8, characterized in that: The positive electrode material is NCM622 pole piece, and the negative electrode material is graphite.
10. A lithium ion battery according to claim 8, characterized in that: The application temperature of the lithium ion battery is -40°C to 25°C.