Anion-regulated weakly solvating sulfone-based electrolyte and method of preparation thereof

Abstract

The application discloses anion-regulated weak-solvation sulfone-based electrolyte and a preparation method thereof, and belongs to the technical field of battery electrolytes.The electrolyte comprises common lithium salts, high-donor-number lithium salts and sulfone solvents.The anion of the high-donor-number lithium salt effectively weakens the coordination between lithium ions and the sulfone solvents, and enhances the interaction between lithium ions and the anions of the common lithium salts.The weak-solvation structure is constructed by the above method, the lithium ion desolvation process and the decomposition of the common lithium salts are promoted, the redox of the anion of the weak-solvation structure is formed, and a solid-state electrolyte interface (SEI) layer rich in inorganic substances is formed, so that the problem of poor compatibility of the sulfone solvents with lithium metal and graphite negative electrodes is solved, the electrolyte has good electrochemical performance and wide temperature range adaptability, and has wide application prospects in lithium ion batteries and energy storage lithium battery systems.

Description

Technical Field

[0001] This invention belongs to the field of battery electrolyte technology, specifically relating to an anion-controlled weakly solvated sulfone-based electrolyte and its preparation method. Background Technology

[0002] Compared to traditional carbonate-based electrolyte systems, sulfone solvents are considered potential high-voltage electrolyte solvents due to their low cost and high oxidation stability. However, sulfone solvents have poor compatibility with lithium metal and graphite anodes, and their high melting point, high viscosity, and low wettability significantly reduce their practicality.

[0003] Currently, researchers typically employ high-concentration electrolytes (HCEs) or locally high-concentration electrolytes (LHCEs) to modulate the solvation structure of sulfone-based electrolytes, thereby improving the electrochemical performance of lithium-ion batteries. For example, increasing the concentration of lithium hexafluorophosphate (LiPF6) salt in the electrolyte forms an inorganic-rich solid electrolyte interface (SEI) film, thus improving battery cycle performance. However, higher salt concentrations lead to higher viscosity and poorer wettability of sulfone-based electrolytes, hindering ion transport and affecting battery cycle performance. While introducing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a diluent has solved the problem of high viscosity in HCEs, most reported diluents are fluorinated ethers, which have low boiling points and volatility issues, limiting the use of sulfone-based electrolytes at high temperatures. Furthermore, adding diluents increases the cost and complexity of the electrolyte. Therefore, developing a novel sulfone-based electrolyte with high efficiency, simplicity, and economy is a pressing technical challenge. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a sulfone-based electrolyte for lithium-ion batteries that features high voltage resistance, wide temperature range, long cycle life, and high safety performance.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] An anion-controlled weakly solvated sulfone-based electrolyte, characterized in that it comprises: a high-donor lithium salt, a sulfone solvent, and a common lithium salt.

[0007] Furthermore, the high-donor lithium salt includes one or more of lithium nitrate, lithium trifluoromethanesulfonate, and lithium bromide.

[0008] Furthermore, the sulfone solvent includes one or more of sulfolane, dimethyl sulfoxide, dimethyl sulfone, dibutyl sulfone, dipropyl sulfone, diethyl sulfone, benzyl sulfone, diphenyl sulfone, ethyl methyl sulfone, ethyl phenyl sulfone, benzosulfone, methoxyethyl methyl sulfone, ethyl methoxyethyl sulfone, and ethyl methoxyethoxyethyl sulfone.

[0009] Furthermore, the common lithium salts include one or more of lithium difluorooxalate borate (LiDFOB), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(oxalate borate) (LiBOB), lithium bis(difluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium hexafluorophosphate (LiPF6).

[0010] The high-donor lithium salts, sulfone solvents, and common lithium salts used in this invention are all commercially available.

[0011] Furthermore, the concentrations of the high-donor lithium salt and the common lithium salt are less than 1 mol / L, and the molar ratio of the high-donor lithium salt to the common lithium salt is (1-5):(5-1).

[0012] Furthermore, the electrolyte is suitable for a wide temperature range and operates stably in environments from -40°C to 80°C; the electrolyte maintains excellent performance under high voltage (4.4V).

[0013] A method for preparing an anion-controlled weakly solvated sulfone-based electrolyte includes the following steps: dissolving a common lithium salt in a sulfone solvent, then adding a high-donor lithium salt, and mixing and stirring until homogeneous.

[0014] A lithium-ion battery comprising the anion-controlled weakly solvated sulfone-based electrolyte described in this invention.

[0015] Furthermore, the lithium-ion battery also includes a positive electrode material and a negative electrode material.

[0016] Furthermore, the positive electrode material includes any one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich materials, nickel-cobalt-manganese ternary materials, and nickel-cobalt-aluminum ternary materials; the negative electrode material includes any one of lithium metal, graphite, lithium titanate, silicon, silicon-carbon, and hard carbon.

[0017] The high-donor-number anions added in this invention can strongly bind with lithium ions, exhibiting a binding affinity greater than that between lithium ions and sulfone solvents, while also demonstrating good solubility in sulfone-based solutions. For example, by using the nitrate ions of the high-donor-number lithium salt LiNO3, the coordination structure between lithium ions and sulfone solvents (such as sulfolane (SL)) is effectively weakened, while the interaction between lithium ions and difluorooxo-oxalate-borate ions is enhanced. This construct of a weakly solvated structure not only promotes the lithium ion desolvation process but also facilitates the decomposition of common lithium salts. Simultaneously, the oxidation-reduction of the high-donor-number lithium salt on the electrode surface forms a solid electrolyte interphase (SEI) layer rich in inorganic matter, further improving the interfacial stability between SL and lithium metal. This also facilitates ion transport, promotes lithium deposition and stripping, solves the problem of poor compatibility between sulfone solvents, lithium metal, and graphite anodes, and improves the cycle performance, high and low temperature resistance, and high voltage resistance of batteries based on weakly solvated sulfone-based electrolytes.

[0018] Beneficial effects

[0019] This invention provides a sulfone-based lithium-ion battery electrolyte with low salt concentration, high voltage resistance, and stable operation over a wide temperature range. By constructing a weakly solvated structure, the compatibility of the sulfone-based electrolyte with lithium metal is improved, effectively inhibiting lithium dendrite growth and electrolyte decomposition, thus enhancing the cycle performance of the lithium-ion battery. Simultaneously, the electrolyte exhibits excellent oxidation resistance. Furthermore, the electrolyte remains stable over a wide temperature range (-40℃ to 80℃), making it suitable for a wider range of applications. This invention reduces the preparation cost of the electrolyte and improves its commercial feasibility through a simple preparation process and low-cost raw materials. Attached Figure Description

[0020] Figure 1 For Li + With SL, DFOB - and NO 3- Binding energy test diagram;

[0021] Figure 2 These are Raman test images of Example 1 and Comparative Example 1;

[0022] Figure 3 This is a diagram verifying the weak solvation structure of Example 1;

[0023] Figure 4 This is an X-ray photoelectron spectroscopy (XPS) test image of the lithium metal side in Example 1;

[0024] Figure 5 X-ray photoelectron spectroscopy (XPS) image of one side of the lithium cobalt oxide cathode;

[0025] Figure 6 Comparative Examples 1-3 ( Figure 6 a, 6b, 6c), Example 1 ( Figure 6 d) A button cell composed of lithium and copper sheets, operating at 4 mA cm -2 After depositing lithium at a current density for 4 hours, the lithium deposition morphology was observed using scanning electron microscopy.

[0026] Figure 7 The graph shows the long-cycle performance of lithium / cobalt oxide batteries using Examples 1, 2, 3, 4 and 5 at 25°C.

[0027] Figure 8 The graph shows the long-cycle performance of the lithium / cobalt oxide batteries using Examples 6-18 at 25°C.

[0028] Figure 9 The graph shows the long-cycle performance of lithium / cobalt oxide batteries using Comparative Examples 1, 2, and 3 at 25°C.

[0029] Figure 10 The cycling performance diagram and charge / discharge curve diagram of the lithium / cobalt oxide battery using Example 1 at 80°C;

[0030] Figure 11 The cycling performance diagram and charge / discharge curve of the lithium / cobalt oxide battery using Example 1 at -40°C are shown.

[0031] Figure 12 The image shows the cycle performance and charge / discharge curves of the lithium / graphite battery used in Example 1 at 25°C. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0033] Example 1

[0034] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiDFOB and 0.2 M LiNO3 were added to sulfolane to prepare an SL-0.2 M LiNO3-0.5 M LiDFOB electrolyte.

[0035] Example 2

[0036] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.3 M LiDFOB and 0.5 M LiNO3 were added to sulfolane to prepare SL-0.3 M LiNO3-0.5 M LiDFOB electrolyte.

[0037] Example 3

[0038] In an argon glove box with both water and oxygen content less than 0.1 ppm, 1 M LiDFOB and 0.2 M LiNO3 were added to sulfolane to prepare an SL-0.2 M LiNO3-1 M LiDFOB electrolyte.

[0039] Example 4

[0040] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.2 M LiDFOB and 0.2 M LiNO3 were added to sulfolane to prepare SL-0.2 M LiNO3-0.2 M LiDFOB electrolyte.

[0041] Example 5

[0042] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.1 M LiDFOB and 0.5 M LiNO3 were added to sulfolane to prepare SL-0.1 M LiNO3-0.5 M LiDFOB electrolyte.

[0043] Example 6

[0044] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiTFSI and 0.2 M LiNO3 were added to dimethyl sulfone (DS) to prepare a DS-0.2 M LiNO3-0.5 M LiTFSI electrolyte.

[0045] Example 7

[0046] In an argon glove box with both water and oxygen contents less than 0.1 ppm, 0.5 M LiBOB and 0.2 M LiNO3 were added to dibutyl sulfone (DBS) to prepare a DBS-0.2 M LiNO3-0.5 M LiBOB electrolyte.

[0047] Example 8

[0048] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiClO4 and 0.2 M LiTf were added to dipropyl sulfone (DPS) to prepare a DPS-0.2 M LiTf-0.5 LiClO4 electrolyte.

[0049] Example 9

[0050] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiTFSI and 0.2 M LiBr were added to diethyl sulfone (DES) to prepare a DES-0.5 M LiBF4-0.2 M LiBr electrolyte.

[0051] Example 10

[0052] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiBF4 and 0.2 M LiBr were added to benzyl sulfone (BMS) to prepare a BMS-0.5 M LiBF4-0.2 M LiBr electrolyte.

[0053] Example 11

[0054] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiBOB and 0.2 M LiNO3 were added to dimethyl sulfoxide (DMSO) to prepare a DMSO-0.2 M LiNO3-0.5 M LiPF6 electrolyte.

[0055] Example 12

[0056] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiFSI and 0.2 M LiTf were added to diphenyl sulfone (DPSO) to prepare a DPSO-0.2 M LiTf-0.5 M LiFSI electrolyte.

[0057] Example 13

[0058] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to ethyl methyl sulfone (EMSO) to prepare an EMSO-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0059] Example 14

[0060] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to ethyl phenyl sulfone (EPSO) to prepare an EPSO-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0061] Example 15

[0062] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to benzyl sulfone (BAS) to prepare a BAS-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0063] Example 16

[0064] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to methoxyethyl methyl sulfone (MEMS) to prepare a MEMS-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0065] Example 17

[0066] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to ethyl methoxyethyl sulfone (EEMS) to prepare EEMS-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0067] Example 18

[0068] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiAsF6 and 0.2 M LiBr were added to ethyl methoxyethoxyethyl sulfone (EBOES) to prepare an EBOES-0.2 M LiBr-0.5 M LiAsF6 electrolyte.

[0069] Comparative Example 1

[0070] In an argon glove box with both water and oxygen content less than 0.1 ppm, 0.5 M LiDFOB was added to SL to prepare SL-LiDFOB electrolyte.

[0071] Comparative Example 2

[0072] SL-LiNO3 electrolyte was prepared by adding 0.2M LiNO3 to SL in an argon glove box where both water and oxygen contents were less than 0.1ppm.

[0073] Comparative Example 3

[0074] In an argon glove box with both water and oxygen content less than 0.1 ppm, an electrolyte was prepared by dissolving 1 M LiPF6 in a solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 (EC / DMC (v:v = 1:1)) to prepare an EC / DMC-LiPF6 electrolyte.

[0075] Performance testing

[0076] Various data tests were conducted on the electrolyte.

[0077] (1) For Li + With SL, DFOB - and NO 3- The binding energy was measured.

[0078] DFT calculations were performed using Gaussian16 software. All DFT calculations were performed at the B3LYP / 6-3111+G(d, p) level. First, the clustering model required for the calculations was constructed using GassView. Then, the structure of all clusters was optimized at the corresponding computational levels. Finally, the anions and cations in the clusters were extracted, and the Li... + With DFOB- /

[0079] NO 3- Binding energy between sulfonated alkane.

[0080] like Figure 1 As shown, DFT theory calculates Li + With SL, DFOB - and NO3 - Binding energy of NO3 - With Li + The interaction energy is higher than that of Li-SL. When NO 3- When introduced, NO 3- It competes with SL for coordination, thereby weakening Li. + Coordination with SL. Conversely, Li + With DFOB - The binding energy is relatively large. Therefore, after adding the high donor number lithium salt LiNO3, Li + As the concentration of DFOB increases, - Able to work with more Li + Coordination provides a basis for constructing anion-enhanced weak solvation structures.

[0081] (2) Raman testing of TF and TFN electrolytes

[0082] TFN was 0.5M LiDFOB-0.2M LiNO3-SL (Example 1), and TF was 0.5M LiDFOB-SL (Comparative Example 1). The laser was turned on and preheated for half an hour. The sample was placed in a glass bottle and tested in a dark environment. The Raman instrument was a HORIBA JY LabRAM HR Evolution.

[0083] like Figure 2 As shown in a, 1025cm -1 peak and NO 3- The symmetric stretching vibration is related. In TFN electrolyte, the peak position shifts to higher frequencies, indicating that free NO3-... - The reduction indicates that NO3 - It participated in the solvation of the sheath layer.

[0084] like Figure 2 As shown in b, the stretching vibration peak of CSC in sulfolane increases from 745 cm⁻¹. -1 Redshifted to 735cm -1 This indicates that SL and Li + The interaction is weakened in TFN electrolyte.

[0085] like Figure 2 As shown in c, the range is 1735-1885cm.-1 Corresponding DFOB - Characteristic peaks. The significant increase in contact ions (CIPs) in TFN electrolyte indicates that Li... + With DFOB - The coordination is enhanced.

[0086] (3) Verification of the weakly solvated structure in Example 1

[0087] Nuclear magnetic resonance (NMR) was performed using TFN (Example 1) and TF (Comparative Example 1) electrolytes. 7Li NMR spectra were recorded using a 600M NMR JNM-ECZ600R / S1 system with D2O (1.0 mol L⁻¹). -1 In the figure, LiCl is an external parameter, set to 0 ppm. Throughout the experiment, ensure the operating environment is dry and free of moisture to minimize its impact on the sample.

[0088] like Figure 3 As shown, add NO 3- TFNs all shift towards lower fields, verifying the weak solvation structure of the TFN electrolyte. (4) Universal force field (UFF) and RESP partial charge description of the molecular structure of TFN (Example 1) and TF (Comparative Example 1) electrolytes.

[0089] A simulation model was constructed using the Packmol software package. First, the model was designed for energy minimization. Then, molecular dynamics calculations were performed on the model under NPT ensemble conditions of 298 K and 1 atmosphere. The total simulation time was 500 ps, ​​with the first 300 ps used for structural relaxation and the last 200 ps used for subsequent data analysis. For the calculated trajectory files, the radial distribution function of the corresponding Li-O / Li-F atom pairs in the system was calculated using the VMD software package, and the corresponding average coordination number is shown in Table 1.

[0090] Table 1 Mean coordination number

[0091] Coordination number Li-O(SL) Li-O(DFOB) <![CDATA[Li-O(NO3)]]> TF 3.960 0.039 - TFN 3.754 0.046 0.198

[0092] As shown in the table above, the coordination number of Li-O(SL) in the TF electrolyte is 3.960. (Introduction of NO...) 3- Subsequently, the coordination number decreased to 3.754, while the coordination number of Li-O(DFOB) increased from 0.039 to 0.046. This indicates that NO 3- The introduction of this material creates a unique anion-enhanced weak solvation structure.

[0093] (5) X-ray photoelectron spectroscopy (XPS) test on the lithium metal side

[0094] The electrolyte used was TFN (Example 1). Lithium sheets were removed from the Li / LCO battery after 100 cycles. The surface of the lithium sheets was rinsed with DMC solvent. Using a clean tool, the lithium metal side was cut into appropriately sized sample pieces, ensuring a smooth surface. To avoid contaminating the lithium metal surface, the entire process was performed under argon atmosphere. The cut lithium metal samples were placed in an XPS vacuum chamber, and the sample was scanned to record the characteristic peaks of Li.

[0095] After 100 cycles of a Li / LCO battery, the X-ray photoelectron spectroscopy (XPS) of the lithium metal side is as follows: Figure 4 As shown, after cycling in TFN electrolyte, a protective layer of LiF and LiNxOy is formed on the lithium metal surface.

[0096] (6) X-ray photoelectron spectroscopy (XPS) test on the positive electrode side of lithium cobalt oxide

[0097] The electrolyte used was TFN (Example 1). After 100 cycles, the lithium cobalt oxide cathode was removed from the Li / LCO battery. The cathode surface was rinsed with DMC solvent, and the lithium metal side was cut into appropriately sized sample pieces using a clean tool. To avoid contaminating the lithium metal surface, the entire process was performed under argon atmosphere. The cut cathode samples were placed in an XPS vacuum chamber, and the sample was scanned to record the characteristic peaks of the F element.

[0098] After 100 cycles of a Li / LCO battery, the X-ray photoelectron spectroscopy (XPS) of the lithium cobalt oxide cathode side is as follows: Figure 5 As shown, after cycling in TFN electrolyte, a LiF protective layer is formed on the surface of the lithium cobalt oxide cathode.

[0099] The electrochemical performance of lithium-ion batteries prepared using the electrolyte of this invention was tested.

[0100] 1. Preparation of electrolyte

[0101] The electrolyte was prepared using the preparation method of Example 1.

[0102] 2. Preparation of positive electrode sheet

[0103] Lithium cobalt oxide cathode material was uniformly dispersed with a super conductive agent (Super P) and a polyvinylidene fluoride (PVDF) binder in a mass ratio of 8:1:1 in a certain amount of N-methylpyrrolidone (NMP) solvent. The mixture was then coated onto aluminum foil, dried, and rolled to prepare the cathode. The cathode loading was 10 mg / cm³. 2 .

[0104] 3. Preparation of graphite anode

[0105] The graphite anode material was mixed with conductive carbon black (Super P), thickener (CMC) and polyvinylidene fluoride (SBR) binder in a mass ratio of 93:2:2.5:2.5 to form a slurry, which was then coated onto copper foil, dried, and rolled to prepare the graphite anode.

[0106] 4. Battery manufacturing

[0107] In an argon glove box with both water and oxygen content less than 0.1 ppm, the following sequence is used to assemble the negative electrode shell / lithium sheet / electrolyte / separator / electrolyte / steel sheet / spring sheet / positive electrode shell. After sealing and pressing, the assembly is completed to prepare the coin cell.

[0108] 5. Material Battery Performance Testing

[0109] Battery cycle test: At 25℃, it was charged and discharged twice at a constant current density of 0.1C (1C=160mAh / g). The charging cutoff potential was 4.4V and the discharging cutoff potential was 3V. After activation, the cycle performance was tested.

[0110] Battery cycle test: The battery is charged to 4.4V at 0.5C constant current at 25℃, and discharged to 3V at 0.5C; the battery is then cycled by constant current charge and discharge twice at 80℃ and -40℃.

[0111] Lithium deposition morphology characterization: using 4mA cm -2 Lithium was deposited on copper foil at a current density of 4 hours, and the deposition morphology of lithium was then observed using a scanning electron microscope.

[0112] Figure 6 It is a button cell battery composed of lithium and copper sheets, with a current of 4mA cm -2 Lithium was deposited at a current density of [value missing] for 4 hours, and the morphology of the lithium deposition was observed by scanning electron microscopy. The results show that in comparative examples 1, 2, and 3, metallic lithium exhibits high porosity and dendritic structure. Figure 6 In contrast, in Example 1, metallic lithium is tightly packed (ac). Figure 6 d) This demonstrates that Example 1 has good compatibility with lithium metal, which is of great significance for the long cycle life of the battery.

[0113] Figure 7 Examples 1 and 2 are respectively. Figure 7 a) Example 2 Figure 7 b) Example 3 Figure 7 c) Example 4 Figure 7 d) Example 5 Figure 7e) Long-term cycling performance of lithium / cobalt oxide batteries with electrolyte at 25°C. The results show that the battery using Example 1 has the highest discharge specific capacity and the slowest capacity decay. After 1000 cycles, the capacity retention rate is as high as 93.3%, indicating that the addition of 0.2M LiNO3 and 0.5M LiDFOB is the optimal ratio.

[0114] Figure 8 The lithium / cobalt oxide batteries used in Examples 6-18 are shown in long-term cycling diagrams at 25°C. The results show that different sulfone-based electrolytes regulated with high donor number lithium salts can significantly improve the cycle life of the batteries and greatly reduce the capacity decay rate, demonstrating the generalizability of this work.

[0115] Figure 9 Comparative Example 1 ( Figure 9 a) Comparative Example 2 Figure 9 b) and Comparative Example 3 Figure 9 c) Long-cycle performance of lithium / cobalt oxide batteries with electrolyte at 25°C. The results show that the capacity decay rate of batteries using Comparative Examples 1, 2, and 3 is greater than that of the battery using Example 1, indicating that the anion-controlled weakly solvated sulfone-based electrolyte has practical application feasibility.

[0116] Figure 10 The long-cycle performance of the lithium / cobalt oxide battery using the electrolyte of Example 1 at 80°C is shown. It can be seen that the battery capacity decay is small, indicating that the battery using Example 1 is suitable for use at 80°C.

[0117] Figure 11 The long-cycle performance of the lithium / cobalt oxide battery using the electrolyte of Example 1 was tested at -40°C. The stable charge-discharge curves show that the battery of Example 1 is suitable for use at -40°C.

[0118] Figure 12 The image shows the long-cycle performance of the lithium / graphite battery in Example 1. It can be seen that the battery charge-discharge curves are stable, indicating that this work has solved the incompatibility problem between sulfolane and the graphite anode.

[0119] In summary, this invention provides an anion-controlled weakly solvated sulfone-based electrolyte and its preparation method. Specifically, the electrolyte is composed of high-donor lithium salts and common lithium salts added to sulfone compounds in different molar ratios. This electrolyte is a sulfone-based lithium-ion battery electrolyte that is resistant to high voltage and operates stably over a wide temperature range. By constructing a weakly solvated structure, the compatibility of the sulfone-based electrolyte with lithium metal is improved, effectively inhibiting lithium dendrite growth and electrolyte decomposition, and enhancing the cycle performance of lithium-ion batteries.

[0120] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. An anion-controlled weakly solvated sulfone-based electrolyte, characterized in that, It includes high-donor lithium salts, sulfone solvents, and common lithium salts; the high-donor lithium salt is lithium nitrate; the sulfone solvent is sulfolane; and the common lithium salt is lithium difluorooxalate borate.

2. The anion-controlled weakly solvated sulfone-based electrolyte according to claim 1, characterized in that, The concentrations of the high-donor lithium salt and the common lithium salt are less than or equal to 1 mol / L, and the molar ratio of the high-donor lithium salt to the common lithium salt is (1-5):(5-1).

3. The anion-controlled weakly solvated sulfone-based electrolyte according to claim 1, characterized in that, The electrolyte is suitable for temperatures ranging from -40°C to 80°C.

4. A method for preparing an anion-controlled weakly solvated sulfone-based electrolyte as described in any one of claims 1-3, characterized in that, Includes the following steps: In an argon glove box with both water and oxygen content less than 0.1 ppm, a commonly used lithium salt is dissolved in a sulfone solvent, and then a high-donor lithium salt is added. The mixture is stirred until homogeneous to obtain a weakly solvated sulfone-based electrolyte.

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