Preparation and application of high-capacity and high-efficiency electrolyte suitable for lithium metal battery
By introducing functional diluents into the lithium metal battery electrolyte, the problems of inefficiency and insufficient stability of lithium metal batteries in high magnification and low temperature environments are solved, high Coulomb efficiency and cyclic stability are achieved, and the theoretical capacity is approached.
Patent Information
- Application Number
- CN202510358393.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2025-05-13
AI Technical Summary
The existing lithium metal battery electrolytes exhibit low efficiency and insufficient stability in high-rate charging and discharging and low-temperature environments, especially the capacity drop caused by the interface deterioration of ether electrolytes and the ion transport hysteresis of carbonate electrolytes.
Using functional diluents, it has the triple functions of viscosity adjustment, interface modification and film-forming components, and is used to prepare a new type of lithium metal battery electrolyte. The diluent includes components such as 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and forms an optimized electrolyte system by combining with an ester organic solvent and a lithium salt.
It significantly improves the energy conversion efficiency of lithium metal batteries in high-rate charging and discharging and extremely low-temperature environments, maintains high Coulomb efficiency and cycling stability, minimizes the irreversible loss of lithium, and is close to the theoretical capacity.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of secondary battery electrolytes and relates to the preparation and application of a high-capacity and high-efficiency electrolyte suitable for lithium metal batteries. Background Art
[0002] As an important development direction of high energy density energy storage system, the practical application of lithium metal battery has long been constrained by the efficiency bottleneck of electrolyte system. In the existing technology, although the traditional ether electrolyte can improve the uniformity of lithium metal deposition to a certain extent, its inherent low oxidation stability leads to a continuous increase in the positive electrode interface impedance, significantly reducing the charge and discharge efficiency; and the carbonate electrolyte, although it has a high oxidation stability, causes a sharp decay of coulomb efficiency due to the violent side reaction with lithium metal. More prominently, the polarization loss caused by the hysteresis of ion transfer kinetics during high-rate charge and discharge of conventional electrolytes, and the sharp drop in energy conversion efficiency caused by the surge in viscosity in low temperature environment, have become common problems restricting the practical application of lithium metal batteries.
[0003] In response to the above efficiency defects, existing technologies usually use solvent compounding or high-concentration electrolyte strategies for optimization, but these solutions often fall into the dilemma of performance imbalance: for example, although increasing the proportion of fluorinated solvents can improve interface stability, it leads to deterioration of electrolyte fluidity, which in turn aggravates the efficiency decay at high rates; and although high-concentration systems can improve the number of lithium ion migration, their excessively high viscosity seriously weakens the effective ion conduction under low-temperature conditions. In addition, existing diluent technologies mostly focus on improving a single performance parameter, such as simply reducing viscosity or adjusting the solvation structure, and fail to systematically solve the problem of synergistic improvement of coulombic efficiency, rate efficiency and low-temperature efficiency in lithium metal batteries.
[0004] The present invention breaks through the shackles of traditional technologies that are difficult to balance between efficiency improvement and performance maintenance by innovatively introducing specific functional diluents. The diluent plays a triple functional role in the system: it acts as a viscosity regulator to improve ion transfer kinetics, it acts as an interface modifier to optimize lithium metal deposition behavior, and it acts as a synergistic film-forming component to enhance the stability of the electrode / electrolyte interface. Compared with the prior art, the electrolyte system of the present invention significantly improves the energy conversion efficiency under all operating conditions while maintaining the stable circulation of the lithium metal negative electrode, especially in high-rate charge and discharge and extreme low temperature environments. It shows a breakthrough efficiency retention ability, providing key material support for the practical application of lithium metal batteries. Summary of the invention
[0005] 1. Technical problem to be solved by the invention
[0006] The purpose of the present invention is to solve the problems of limited stabilization of lithium metal negative electrodes by existing ether electrolytes, charge and discharge efficiency attenuation caused by interface degradation when matching high-voltage positive electrodes, and sudden capacity drop caused by ion transport hysteresis of carbonate electrolytes at low temperatures, and to develop a lithium metal battery electrolyte system containing a functionalized diluent and its application. Compared with the traditional system, the present invention adopts a functionalized diluent to synergistically improve the coulombic efficiency and cycle stability while ensuring the charge and discharge voltage window, providing a key material solution for the development of practical lithium metal batteries.
[0007] 2. Technical solution
[0008] In order to achieve the above object, the present invention provides the following technical solutions:
[0009] The present invention provides a method for preparing an electrolyte, comprising the following steps:
[0010] 1) mixing one or more ester organic solvents and stirring them uniformly to obtain an ester solvent mixed solution;
[0011] 2) adding the diluent and additive into the ester solvent mixture, stirring evenly to obtain a mixed solvent;
[0012] 3) Adding a single lithium salt into the mixed solvent and stirring until the lithium salt is completely dissolved to obtain an electrolyte.
[0013] Furthermore, the ester organic solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, difluoroethylene carbonate, fluoroethylene carbonate, trimethyl phosphate, methyl trifluoroethyl carbonate, and methyl propionate, preferably a mixed solvent of ethylene carbonate, ethyl methyl carbonate and difluoroethylene carbonate, a mixed solvent of difluoroethylene carbonate and ethyl methyl carbonate, and more preferably a mixed solvent of ethylene carbonate, ethyl methyl carbonate and difluoroethylene carbonate.
[0014] Furthermore, the diluent and additive is one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and 2H,3H-decafluoropentane, preferably 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2H,3H-decafluoropentane, and more preferably 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.
[0015] Furthermore, the volume ratio of the diluent and additive in the electrolyte to the mixed solvent is 20% to 80%, preferably 30% to 70%, and more preferably 50% to 70%.
[0016] Furthermore, the single lithium salt is one of lithium hexafluorophosphate, lithium bis(difluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium trifluoroacetate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(fluoroborate), preferably lithium bis(difluorosulfonyl imide, lithium bis(trifluoromethylsulfonyl imide), and lithium hexafluorophosphate, and more preferably lithium bis(difluorosulfonyl imide).
[0017] Furthermore, the concentration of the lithium salt in the electrolyte in the mixed solvent is 0.5 to 4 mol / L, preferably 1.0 to 3.0 mol / L, and more preferably 1.2 to 2 mol / L.
[0018] Furthermore, the electrolyte solution is prepared in an argon atmosphere, and the stirring temperature is room temperature (25-30° C.).
[0019] The invention also provides an electrolyte obtained by the preparation method.
[0020] The beneficial effects of the present invention include the following:
[0021] 1) The preparation process of the electrolyte is simple, the operation process is easy to implement, and it has good potential for industrial promotion.
[0022] 2) The electrolyte prepared by the present invention has an ultra-high coulombic efficiency of up to 99.84%, thereby minimizing the irreversible loss of lithium.
[0023] 3) The electrolyte prepared by the present invention has a maximum capacity of 195.06 mAh g in Li-NCM811. -1 The discharge specific capacity is close to the theoretical capacity. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 The diagram is a change diagram of the coulomb efficiency of the lithium negative electrode at room temperature using the electrolytes of the embodiment and the comparative example;
[0025] Figure 2 The discharge specific capacity variation diagram of the Li-NCM811 battery assembled using the electrolytes of the embodiment and the comparative example;
[0026] Figure 3 The graph shows the coulombic efficiency change of Li-NCM811 batteries assembled using the electrolytes of the embodiment and the comparative example. DETAILED DESCRIPTION
[0027] The present invention provides a method for preparing an electrolyte, comprising the following steps:
[0028] 1) mixing one or more ester organic solvents and stirring them uniformly to obtain an ester solvent mixed solution;
[0029] 2) adding the diluent and additive into the ester solvent mixture, stirring evenly to obtain a mixed solvent;
[0030] 3) Adding a single lithium salt into the mixed solvent and stirring until the lithium salt is completely dissolved to obtain an electrolyte.
[0031] In the present invention, the ester organic solvent is one or more of ethylene carbonate (EC), propylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), bisfluoroethylene carbonate (DFEC), fluoroethylene carbonate, trimethyl phosphate, methyl trifluoroethyl carbonate, and methyl propionate, preferably a mixed solvent of ethylene carbonate, ethyl methyl carbonate and bisfluoroethylene carbonate, a mixed solvent of bisfluoroethylene carbonate and ethyl methyl carbonate, and more preferably a mixed solvent of ethylene carbonate, ethyl methyl carbonate and bisfluoroethylene carbonate.
[0032] In the present invention, the diluent and additive is one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TTE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and 2H,3H-decafluoropentane (HFC), preferably 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether and 2H,3H-decafluoropentane, and more preferably 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.
[0033] In the present invention, the volume ratio of the diluent and additive in the electrolyte to the mixed solvent is 20% to 80%, preferably 30% to 70%, and more preferably 50% to 70%.
[0034] In the present invention, the single lithium salt is one of lithium hexafluorophosphate (LiPF6), lithium bis(difluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoroacetate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(fluoroborate), preferably lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium hexafluorophosphate, and more preferably lithium bis(difluorosulfonyl)imide.
[0035] In the present invention, the concentration of the lithium salt in the electrolyte in the mixed solvent is 0.5 to 4 mol / L, preferably 1.0 to 3.0 mol / L, and more preferably 1.2 to 2 mol / L.
[0036] In the present invention, the electrolyte is prepared in an argon atmosphere, and the stirring temperature is room temperature (25-30° C.).
[0037] The invention also provides an electrolyte obtained by the preparation method.
[0038] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0039] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.
[0040] Example 1
[0041] EC, EMC and DFEC were fully mixed in a volume ratio of 0.07:0.63:0.3 to obtain an ester-based mixed solvent A, and TTE was added to the ester-based mixed solution A so that the volume ratio of the ester-based mixed solvent A to TTE was 8:2 to obtain a mixed solvent A. LiFSI was added to the mixed solvent A and fully dissolved so that the concentration of the solution was 1 mol / L to obtain an electrolyte A.
[0042] Electrolyte A was used to assemble a lithium copper half-cell with a lithium sheet, a copper sheet, and a separator. -2 The coulombic efficiency test was carried out at a current density of 30°C. Figure 1 As shown in Figure 3, after the battery cycle stabilized, the average Coulombic efficiency was 98.04%, and it remained stable within 100 cycles.
[0043] The Li-NCM811 battery was assembled with electrolyte A, lithium sheet, NCM811 cathode sheet and separator. After activation at 0.2C current density for 3 cycles, the battery was charged and discharged at 1C current density. Figure 2 As shown in Figure 2, the maximum discharge capacity of the battery reached 171.84 mAh g -1 , and the battery capacity is very stable during the 100 cycles, with no signs of capacity decay, and the capacity retention rate is close to 100% after 100 cycles. The coulombic efficiency during the cycle is as follows Figure 3 As shown, the average Coulomb efficiency is as high as 99.59% and is very stable with almost no fluctuation.
[0044] Example 2
[0045] EC, EMC and DFEC were fully mixed in a volume ratio of 0.21:0.49:0.3 to obtain an ester-based mixed solvent B, and HFC was added to the ester-based mixed solution B so that the volume ratio of the ester-based mixed solvent B to HFC was 7:3 to obtain a mixed solvent B. LiPF6 was added to the mixed solvent B and fully dissolved so that the concentration of the solution was 1.5 mol / L to obtain an electrolyte B.
[0046] Electrolyte B was used to assemble a lithium copper half-cell with a lithium sheet, a copper sheet, and a separator. -2 The coulombic efficiency test was carried out at a current density of 30°C. Figure 1 As shown, after the battery cycle stabilizes, the average Coulombic efficiency is 98.79%, and it remains stable within 100 cycles.
[0047] The Li-NCM811 battery was assembled with electrolyte B, lithium sheet, NCM811 cathode sheet and separator. After activation at 0.2C current density for 3 cycles, the battery was charged and discharged at 1C current density. Figure 2 As shown, the battery has a maximum discharge capacity of up to 184.8 mAh g -1 , and the battery capacity did not fluctuate significantly during the 100 cycles, and the capacity retention rate after 100 cycles was 95.01%. The coulombic efficiency during the cycle is shown in Figure 3 As shown, the average Coulomb efficiency is as high as 99.84% and is very stable with almost no fluctuation.
[0048] Example 3
[0049] DEC and EMC were fully mixed in a volume ratio of 1:9 to obtain an ester-based mixed solvent C, and TTE was added to the ester-based mixed solution C so that the volume ratio of the ester-based mixed solvent C to TTE was 5:5 to obtain a mixed solvent C. LiFSI was added to the mixed solvent C and fully dissolved so that the concentration of the solution was 1.2 mol / L to obtain an electrolyte C.
[0050] Electrolyte C was used to assemble a lithium copper half-cell with a lithium sheet, a copper sheet, and a separator. -2 The coulombic efficiency test was carried out at a current density of 30°C. Figure 1 As shown in Figure 3, after the battery cycle stabilized, the average Coulombic efficiency was 98.51%, and it remained stable within 100 cycles.
[0051] The Li-NCM811 battery was assembled with electrolyte C, lithium sheet, NCM811 positive electrode sheet and separator. After activation at 0.2C current density for 3 cycles, the battery was charged and discharged at 1C current density. Figure 2 As shown, the highest discharge capacity of the battery is up to 195.06 mAh g -1 , the capacity retention rate after 100 cycles is 88%. The coulombic efficiency during the cycle is as follows Figure 3 As shown, the average Coulombic efficiency is as high as 98.14%.
[0052] Example 4
[0053] DFEC and DMC were fully mixed in a volume ratio of 1:9 to obtain an ester-based mixed solvent D, and HFC was added to the ester-based mixed solution D so that the volume ratio of the ester-based mixed solvent D to HFC was 3:7 to obtain a mixed solvent D. LiFSI was added to the mixed solvent D and fully dissolved so that the concentration of the solution was 2 mol / L to obtain an electrolyte D.
[0054] Electrolyte D was used to assemble a lithium copper half-cell with a lithium sheet, a copper sheet, and a separator. -2 The coulombic efficiency test was carried out at a current density of 30°C. Figure 1 As shown, after the battery cycle stabilizes, the average Coulombic efficiency is 98.57%, and it remains stable within 100 cycles.
[0055] The Li-NCM811 battery was assembled with electrolyte D, lithium sheet, NCM811 cathode sheet and separator. After activation at 0.2C current density for 3 cycles, the battery was charged and discharged at 1C current density. Figure 2 As shown, the battery has a maximum discharge capacity of up to 183.9 mAh g -1 , and the battery capacity remained stable during 100 cycles, with a capacity retention rate of up to 97.1% after 100 cycles. The coulombic efficiency during the cycle is as follows Figure 3 As shown, the average Coulombic efficiency is as high as 98.93%.
[0056] Comparative Example
[0057] EC, EMC and DFEC were fully mixed at a volume ratio of 0.07:0.63:0.3 to obtain an ester-based mixed solvent E. LiFSI was added to the ester-based mixed solvent E and fully dissolved so that the concentration of the solution was 1.2 mol / L, thereby obtaining an electrolyte E.
[0058] Electrolyte E was used to assemble a lithium copper half-cell with a lithium sheet, a copper sheet, and a separator. -2 The coulombic efficiency test was carried out at a current density of 30°C. Figure 1 As shown, the coulombic efficiency of the battery is low, with an average coulombic efficiency of only 95.64%.
[0059] The Li-NCM811 battery was assembled with electrolyte E, lithium sheet, NCM811 positive electrode sheet and separator. After activation at 0.2C current density for 3 cycles, the battery was charged and discharged at 1C current density. Figure 2 As shown, during the cycle, the initial capacity of the battery is only 133.4 mAh g -1And it decays sharply during the cycle, and the capacity decays to almost 0 after 50 cycles. The coulomb efficiency during the cycle is as follows Figure 3 As shown, the coulombic efficiency of the battery is low and produces extremely unstable and violent fluctuations, making the battery unable to cycle normally.
[0060] Compared with the comparative example, the samples of the embodiment have ultra-high coulombic efficiency and ultra-high discharge specific capacity, and excellent cycle stability.
Claims
1. A method for preparing a high-capacity and high-efficiency electrolyte suitable for lithium metal batteries, characterized in that: The following steps are involved: (1) mixing one or more ester organic solvents and stirring them uniformly to obtain an ester solvent mixed solution; (2) adding a diluent and additive into the ester solvent mixture and stirring uniformly to obtain a mixed solvent; (3) Adding a single lithium salt into a mixed solvent and stirring until the lithium salt is completely dissolved to obtain an electrolyte.
2. The preparation method according to claim 1, characterized in that: The ester organic solvent described in step (1) is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, difluoroethylene carbonate, fluoroethylene carbonate, trimethyl phosphate, methyl trifluoroethyl carbonate, and methyl propionate.
3. The preparation method according to claim 1, characterized in that: The diluent and additive described in step (2) is one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and 2H,3H-decafluoropentane.
4. The preparation method according to claim 1, characterized in that: The single lithium salt described in step (3) is one of lithium hexafluorophosphate, lithium bis(difluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium trifluoroacetate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium difluoroborate.
5. The preparation method according to claim 1, characterized in that: The volume ratio of the diluent and additive to the mixed solvent is 20% to 80%.
6. The preparation method according to claim 1, characterized in that: The concentration of the lithium salt in the electrolyte in the mixed solvent is 0.5-4 mol / L.
7. An electrolyte obtained by the preparation method.
8. The use of a high-capacity and high-efficiency electrolyte suitable for lithium metal batteries according to any one of claims 1 to 7, characterized in that: The electrolyte enables lithium metal batteries to have high capacity and high coulombic efficiency.
9. The use of a high-capacity and high-efficiency electrolyte suitable for lithium metal batteries according to claim 8, characterized in that: The negative electrode of the lithium metal battery used is metallic lithium, and the positive electrode material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium titanate, lithium manganese oxide, lithium nickel oxide, nickel cobalt manganese ternary, nickel cobalt aluminum ternary, sulfur, oxygen, carbon dioxide, and air; the diaphragm of the lithium metal battery is one or more of a polypropylene diaphragm, a polyethylene diaphragm, a composite diaphragm of polypropylene and polyethylene, a glass fiber diaphragm, a polytetrafluoroethylene diaphragm, and a cellulose diaphragm.