Lithium ion battery electrolyte for lithium metal negative electrode as well as preparation method and application of lithium ion battery electrolyte
By adding the rare earth-based additive bis(trifluoromethanesulfonyl)imine cerium (Ce(TFSI)3) to the electrolyte of the lithium metal negative electrode, the SEI interface layer is optimized, and the electrolyte adaptability problem of the lithium metal negative electrode is solved, achieving more stable electrochemical performance and longer battery cycle life.
Patent Information
- Application Number
- CN202510597054.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-09
- Publication Date
- 2025-08-15
AI Technical Summary
The electrolyte system of traditional lithium metal negative electrodes has sharply decreased adaptability when the lithium metal negative electrodes, resulting in problems such as electrolyte decomposition cycle, lithium dendrites growth and poor thermal stability.
The low-dose rare earth-based additive bis(trifluoromethanesulfonyl)imide cerium (Ce(TFSI)3) is used to participate in the formation of the solid electrolyte interface (SEI) of the lithium negative electrode, optimize the components of the SEI interface layer and improve its stability.
It improves the electrochemical performance of lithium metal negative electrode, inhibits dendrites' growth, reduces the risk of thermal runaway, and improves the Coulomb efficiency and cycling performance of the battery.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a lithium ion battery electrolyte for a lithium metal negative electrode, and a preparation method and application thereof. Background Art
[0002] Currently, conventional commercial electrolyte systems use carbonate solvents with moderate concentrations of lithium hexafluorophosphate (LiPF6), which offer suitable electrochemical performance and significant cost advantages. However, the compatibility of conventional electrolyte systems decreases dramatically when lithium metal is used as the anode, leading to a series of problems such as a vicious electrolyte decomposition cycle, lithium dendrite growth, and poor thermal stability. Summary of the Invention
[0003] To address the issues raised in the background art, the present invention provides a lithium-ion battery electrolyte for a lithium metal anode, a preparation method, and applications thereof. The present invention improves the electrochemical performance of the lithium metal anode by in-situ construction of a corrosion-resistant CeF3 solid electrolyte interface.
[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a lithium-ion battery electrolyte additive for lithium metal negative electrode, and the additive includes cerium bis(trifluoromethanesulfonyl)imide.
[0005] On the other hand, the present invention provides a lithium ion battery electrolyte for lithium metal negative electrode, comprising an organic solvent, a lithium salt, and the above-mentioned lithium ion battery electrolyte additive for lithium metal negative electrode.
[0006] Furthermore, the organic solvent is selected from a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), and a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).
[0007] Furthermore, the organic solvent is selected from a mixture of ethylene carbonate and diethyl carbonate, and the volume percentage of ethylene carbonate in the mixture of ethylene carbonate and diethyl carbonate is 40%-60%, preferably 50%.
[0008] Furthermore, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), lithium bis(fluorosulfonyl imide) (LiFSI), and lithium bis(oxalatoborate) (LiBOB).
[0009] Furthermore, the lithium salt is selected from lithium hexafluorophosphate, and the molar concentration of the lithium hexafluorophosphate is 0.8-1.5 mol L -1 , preferably 1 mol L-1 .
[0010] Furthermore, the weight percentage of the lithium-ion battery electrolyte additive for the lithium metal negative electrode is 0.25-2%, preferably 0.5%.
[0011] On the other hand, the present invention provides a method for preparing a lithium-ion battery electrolyte for a lithium metal negative electrode as described above, comprising the following steps: mixing an organic solvent and a lithium salt evenly, then adding a lithium-ion battery electrolyte additive for a lithium metal negative electrode and stirring until the electrolyte is clear and free of precipitation to obtain the lithium-ion battery electrolyte for a lithium metal negative electrode.
[0012] In another aspect, the present invention provides a use of any of the above-mentioned lithium-ion battery electrolytes for lithium metal negative electrodes in lithium-ion batteries.
[0013] On the other hand, the present invention provides a lithium-ion battery, which uses any of the above-mentioned lithium-ion battery electrolytes for lithium metal negative electrodes or the lithium-ion battery electrolytes for lithium metal negative electrodes prepared by the above-mentioned methods as electrolytes.
[0014] Compared with the prior art, the present invention has the following beneficial effects:
[0015] The present invention uses a low dose of high-efficiency and low-cost rare earth-based additive cerium bis(trifluoromethanesulfonyl)imide (Ce(TFSI)3) to participate in the formation of SEI at the lithium negative electrode during the charge and discharge process, optimize the components of the SEI interface layer, improve the stability of the SEI, prevent the vicious decomposition cycle of the electrolyte, and improve the overall coulombic efficiency and cycle performance of the battery. In addition, the stable SEI can regulate the charge distribution on the surface of the lithium negative electrode, inhibit dendrite growth, and reduce the risk of thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 Graph showing the cycling performance of the electrolytes prepared in Example 3 of the present invention and Comparative Examples 1-5 in a Li||Li symmetrical battery;
[0017] Figure 2 Graph showing the cycling performance of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 in a Li||Li symmetrical battery;
[0018] Figure 3 Graph showing the cycling performance of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 at high current density in a Li||Li symmetrical battery;
[0019] Figure 4 CCD diagram of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 in a Li||Li symmetric battery;
[0020] Figure 5 Coulombic efficiency diagram of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 in a Li||Cu half-cell;
[0021] Figure 6 Graph showing the cycling performance of the electrolytes prepared in Example 1 and Comparative Example 5 of the present invention in Li||LFP lithium-ion batteries;
[0022] Figure 7 This is a rate performance diagram of the electrolyte prepared in Example 1 of the present invention and Comparative Example 5 in a Li||LFP lithium-ion battery;
[0023] Figure 8 This is a Ce 3d XPS spectrum recorded on the surface of the lithium negative electrode of the electrolyte prepared in Example 1 of the present invention and Comparative Example 5 after the first cycle in the Li||LFP lithium ion battery. DETAILED DESCRIPTION
[0024] In order to better understand the content of the present invention, the content of the present invention is further described below in conjunction with specific implementation methods, but the protection content of the present invention is not limited to the following embodiments.
[0025] Example 1
[0026] Lithium-ion battery electrolyte (LD) for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cerium bis(trifluoromethanesulfonyl)imide (Ce(TFSI)3); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 The weight percentage of cerium bis(trifluoromethanesulfonyl)imide is 0.5%.
[0027] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0028] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then cerium bis(trifluoromethanesulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0029] Example 2
[0030] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cerium bis(trifluoromethanesulfonyl)imide; the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1The weight percentage of cerium bis(trifluoromethanesulfonyl)imide is 0.25%.
[0031] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0032] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then cerium bis(trifluoromethanesulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0033] Example 3
[0034] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cerium bis(trifluoromethanesulfonyl)imide; the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of cerium bis(trifluoromethanesulfonyl)imide is 1%.
[0035] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0036] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then cerium bis(trifluoromethanesulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0037] Example 4
[0038] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cerium bis(trifluoromethanesulfonyl)imide; the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of cerium bis(trifluoromethanesulfonyl)imide is 2%.
[0039] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0040] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then cerium bis(trifluoromethanesulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0041] Comparative Example 1
[0042] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and lanthanum bis(trifluoromethylsulfonyl)imide (La(TFSI)3); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of lanthanum bis(trifluoromethylsulfonyl)imide is 1%.
[0043] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0044] Ethylene carbonate and diethyl carbonate were mixed, and lithium hexafluorophosphate was added and mixed evenly, and then lanthanum bis(trifluoromethylsulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0045] Comparative Example 2
[0046] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and silver bis(trifluoromethylsulfonyl)imide (AgTFSI); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of silver bis(trifluoromethylsulfonyl)imide is 1%.
[0047] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0048] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then silver bis(trifluoromethylsulfonyl)imide was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0049] Comparative Example 3
[0050] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cobalt bis(trifluoromethylsulfonyl)imide (Co(TFSI)2); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of cobalt bis(trifluoromethylsulfonyl)imide is 1%.
[0051] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0052] Ethylene carbonate and diethyl carbonate were mixed, and lithium hexafluorophosphate was added and mixed evenly, and then bis(trifluoromethylsulfonyl)imide cobalt was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0053] Comparative Example 4
[0054] Lithium-ion battery electrolyte for lithium metal anode: including a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), lithium hexafluorophosphate (LiPF6) and cerium trifluoromethanesulfonate (Ce(OTf)3); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 , the weight percentage of cerium trifluoromethanesulfonate is 1%.
[0055] The preparation method of lithium ion battery electrolyte for lithium metal negative electrode is as follows:
[0056] Ethylene carbonate and diethyl carbonate were mixed, lithium hexafluorophosphate was added and mixed evenly, and then cerium trifluoromethanesulfonate was added and heated at 400 r min. -1 The mixture was stirred for 6 h until it became clear without precipitation, thereby obtaining a lithium-ion battery electrolyte for lithium metal negative electrode.
[0057] Comparative Example 5
[0058] Conventional electrolyte (BE): includes a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), and lithium hexafluorophosphate (LiPF6); the volume ratio of ethylene carbonate and diethyl carbonate is 1:1, and the molar concentration of lithium hexafluorophosphate is 1 mol L -1 .
[0059] The preparation method of traditional electrolyte is as follows:
[0060] Ethylene carbonate and diethyl carbonate were mixed, and lithium hexafluorophosphate was added and mixed evenly. -1 The solution was stirred for 6 h until it became clear without precipitation to obtain a conventional electrolyte.
[0061] The electrolytes prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to electrochemical performance tests of Li||Li symmetrical cells and Li||Cu half-cells, respectively. The button cell assembly method for the symmetrical cell and half-cell is to assemble the negative electrode shell, gasket, stainless steel sheet, negative electrode sheet, diaphragm, positive electrode sheet and positive electrode shell into a button cell in sequence. The amount of electrolyte added was 40 μL, and the electrolyte was pressed under a nominal pressure of 50 kPa and allowed to stand for 12 hours before electrochemical testing. The cycling performance results of the electrolytes prepared in Example 3 of the present invention and Comparative Examples 1-5 in the Li||Li symmetrical cell are shown in FIG. Figure 1 As shown, from Figure 1 It can be seen that at 3 mA cm -2 、1mAh cm -2 Under these conditions, the use of Ce(TFSI)3 enables the Li||Li symmetric battery to have a lower overpotential and long cycle performance. Lower overpotential means faster electrochemical reaction kinetics, smaller ion transport resistance, and better interface stability, which shows that the use of the additive Ce(TFSI)3 enhances the stability of the interface, reduces the occurrence of irreversible side reactions at the interface, inhibits the growth of dendrites, and improves the reversibility of lithium ion insertion and extraction and the cycle performance of the battery. The electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 have a high overpotential and long cycle performance in the Li||Li symmetric battery at 1 mA cm -2 The cycling performance at current density is as follows Figure 2 As shown, the electrolytes prepared in Examples 1-4 and Comparative Example 5 of the present invention have a 3 mA cm -2 Cycling performance at current density Figure 3 As shown, from Figure 2 and Figure 3 It can be seen that at 1 mA cm -2 , 3mA cm -2 The Li||Li symmetric battery using electrolyte containing 0.25-2wt% Ce(TFSI)3 has longer cycle performance at the current density. Figure 2 At low and medium currents, cerium in the SEI will hinder the transmission of lithium ions to a certain extent, so there will be a slightly higher overpotential than traditional electrolytes. However, traditional electrolytes will fail prematurely due to short circuits during the cycle. The cerium SEI in the electrolyte containing 0.25-2wt% Ce(TFSI)3 will hinder the vicious decomposition of the electrolyte and dendrite growth, thereby extending the battery cycle life. Figure 3 Medium current Figure 2The overpotential of conventional electrolytes increases rapidly due to poor SEI interface stability, while the electrolyte containing 0.25-2 wt% Ce(TFSI)3 has a very low overpotential increase due to its excellent SEI interface stability, once again demonstrating better interface stability and cycle stability. The critical current density (CCD) results of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 in Li||Li symmetric cells are shown in Figure 2. Figure 4 As shown, from Figure 4 It can be seen that the addition of different concentrations of Ce(TFSI)3 improves the CCD. The CCD values of 0.25wt% and 0.5wt% Ce(TFSI)3 are as high as 17mA cm -2 , 16mA cm -2 Critical current density (CCD) is a core parameter for measuring the anti-dendrite ability and high current stability of a battery system. A high CCD means safer fast charging potential and longer cycle life. The coulombic efficiency results of the electrolytes prepared in Examples 1-4 of the present invention and Comparative Example 5 in Li||Cu half-cells are shown in Figure 2. Figure 5 As shown, from Figure 5 As can be seen in the Li||Cu half-cell coulombic efficiency test, compared with the traditional electrolyte, the addition of different concentrations of Ce(TFSI)3 can improve the battery's coulombic efficiency. When 0.5wt% Ce(TFSI)3 is added, the battery's coulombic efficiency remains at 95.31% over a long cycle of 97 cycles. The Li||Cu half-cell coulombic efficiency reflects the reversible insertion and deinsertion of lithium ions in the additive system.
[0062] The electrolytes prepared in Example 1 and Comparative Example 5 were subjected to electrochemical performance tests of Li||LFP full batteries (Li||LFP LD and Li||LFP BE), respectively. The preparation of the full battery includes the preparation of the positive electrode sheet and the assembly of the button battery. The positive electrode sheet is prepared by ball milling 3.2g of commercial lithium iron phosphate (LFP), 0.4g of PVDF, and 0.4g of carbon black, followed by adding 6mL of N-methylpyrrolidone solution (NMP) and stirring in a glove box for 6h. Subsequently, a 100μm scraper is used to coat the copper foil. After coating, the copper foil is vacuum dried in an oven at 80°C for 2h and cut into electrode sheets with a diameter of 10mm using a slicer; the cut electrode sheets are placed in a 120°C oven for vacuum drying for 12h, and then immediately placed in a glove box after the drying is completed. The button battery assembly method is to assemble the negative electrode shell, gasket, stainless steel sheet, negative electrode sheet, diaphragm, positive electrode sheet and positive electrode shell in sequence into a button battery. The electrolyte drop amount was 40 μL, and the electrolyte was compacted under a nominal pressure of 50 kPa. After standing for 12 hours, the electrochemical test was performed. The cycle performance of the electrolyte prepared in Example 1 of the present invention and Comparative Example 5 in Li||LFP lithium ion batteries is shown in FIG. Figure 6 As shown, from Figure 6 It can be seen that the maximum discharge capacity of the battery containing the traditional electrolyte is 163.3 mAh g -1 After 220 cycles, the capacity retention rate was 76%, and then short-circuited and failed. The coulombic efficiency remained at 99%. The battery containing 0.5wt% Ce(TFSI)3 electrolyte was -1 ) and achieved a long cycle stability of 500 cycles at a current density of 1.5 GHz, with a maximum discharge capacity of 163.3 mAh g -1 , after 450 cycles, it still has 80% capacity retention rate and Coulomb efficiency remains at 99%. The rate performance of the electrolyte prepared in Example 1 of the present invention and Comparative Example 5 in Li||LFP lithium ion battery is as follows Figure 7 As shown, from Figure 7 It can be seen that the SEI layer with the cerium compound passivation layer does not affect the rate performance of the full battery and even slightly improves it. The Ce 3d XPS spectra recorded on the lithium negative electrode surface of the electrolyte prepared in Example 1 of the present invention and Comparative Example 5 after the first cycle are as follows: Figure 8 As shown in the figure, the XPS analysis of Ce 3d shows that the electrolyte with the addition of Ce(TFSI)3 forms corrosion-resistant phases such as CeF3 and CeO2 on the surface of the lithium negative electrode to improve the cycle stability of the battery.
[0063] The above description is only a specific embodiment of the present invention, not all embodiments. Any equivalent transformation of the technical solution of the present invention made by ordinary technicians in this field after reading the specification of the present invention is covered by the claims of the present invention.
Claims
1. A lithium ion battery electrolyte additive for lithium metal negative electrode, characterized in that The additive includes cerium bis(trifluoromethanesulfonyl)imide.
2. A lithium ion battery electrolyte for a lithium metal negative electrode, characterized in that: The invention comprises an organic solvent, a lithium salt, and the lithium ion battery electrolyte additive for a lithium metal negative electrode according to claim 1.
3. The lithium ion battery electrolyte for lithium metal negative electrode according to claim 2, characterized in that The organic solvent is selected from the group consisting of a mixture of ethylene carbonate and dimethyl carbonate, a mixture of ethylene carbonate and diethyl carbonate, and a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate.
4. The lithium ion battery electrolyte for lithium metal negative electrode according to claim 3, characterized in that The organic solvent is selected from a mixture of ethylene carbonate and diethyl carbonate, and the volume percentage of ethylene carbonate in the mixture of ethylene carbonate and diethyl carbonate is 40%-60%, preferably 50%.
5. The lithium ion battery electrolyte for lithium metal negative electrode according to claim 2, characterized in that The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalatoborate).
6. The lithium ion battery electrolyte for lithium metal negative electrode according to claim 5, characterized in that The lithium salt is selected from lithium hexafluorophosphate, and the molar concentration of the lithium hexafluorophosphate is 0.8-1.5 mol L -1 , preferably 1 mol L -1 .
7. The lithium ion battery electrolyte for lithium metal negative electrode according to claim 2, characterized in that The weight percentage of the lithium ion battery electrolyte additive for the lithium metal negative electrode is 0.25-2%, preferably 0.5%.
8. The method for preparing a lithium-ion battery electrolyte for a lithium metal negative electrode according to any one of claims 2 to 7, characterized in that: The method comprises the following steps: uniformly mixing an organic solvent and a lithium salt, then adding a lithium ion battery electrolyte additive for a lithium metal negative electrode and stirring until the electrolyte is clear and free of precipitation to obtain the lithium ion battery electrolyte for a lithium metal negative electrode.
9. Use of the lithium ion battery electrolyte for lithium metal negative electrode according to any one of claims 2 to 7 in a lithium ion battery.
10. A lithium ion battery, characterized in that: The lithium ion battery electrolyte for lithium metal negative electrode according to any one of claims 2 to 7 or the lithium ion battery electrolyte for lithium metal negative electrode prepared by the method according to claim 8 is used as the electrolyte.