Bifunctional co-solvent wide-temperature lithium ion battery electrolyte and application thereof

Abstract

This invention relates to a bifunctional co-solvent wide-temperature lithium-ion battery electrolyte and its application. The wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, tris(trimethylsilane)phosphate, and additives. The lithium-ion battery prepared with the bifunctional co-solvent wide-temperature electrolyte of this invention effectively broadens the operating temperature range, improves high-temperature cycle performance and low-temperature discharge performance, and features a wide operating temperature range, high specific energy, and long cycle life. Furthermore, it exhibits excellent thermal stability and good safety performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolyte technology, specifically relating to a dual-functional co-solvent wide-temperature lithium-ion battery electrolyte and its application. Background Technology

[0002] Since the invention of lithium-ion batteries (LIBs) in 1990, they have rapidly dominated the power supply market for electronic devices. With further improvements in energy density and decreases in production costs, lithium-ion batteries have almost monopolized the electric vehicle battery market and are gradually moving towards grid-scale energy storage. As the most advanced battery technology currently available, lithium-ion batteries offer advantages such as high energy density, high output voltage, long cycle life, low self-discharge, and no memory effect. However, LIBs still face safety risks and a narrow operating temperature range.

[0003] Temperature is a crucial factor affecting the health and safe operation of lithium-ion batteries. Commercial lithium-ion batteries typically operate within a temperature range of -20 to 60°C, meeting the needs of most portable electronic devices. However, for electric vehicle batteries, the operating temperature range is wider than that of portable devices to adapt to regional and seasonal variations. Furthermore, in extreme applications in the defense and military industries, lithium-ion batteries need to operate at temperatures below -40°C and be able to store stably at high temperatures (capacity retention >80% after 48 hours of storage at 70°C, pouch cell expansion rate <5%). In the aerospace field, the lower limit of the operating temperature range for lithium-ion batteries even needs to be extended to -50°C or lower. Therefore, developing wide-temperature-range lithium-ion batteries is essential for improving battery stability, safety, and applicability.

[0004] Patent publication number CN 105428719 A discloses a high-voltage wide-temperature lithium-ion battery electrolyte, its preparation method and application. This patent uses 3-fluoro-1,3-propenesulfonate lactone as a fixed additive to prepare the electrolyte to improve the battery's cycle stability and high-temperature cycle performance under high voltage. However, the examples only provide discharge data of the battery at voltages of 3.0 to 4.95V, without mentioning high-temperature cycle performance and wide-temperature performance.

[0005] Patent publication number CN 106450462 A discloses a high-voltage, wide-temperature lithium-ion battery electrolyte. It employs a cyclic carbonate solvent and di(trifluoromethanol) carbonate, along with functional additives such as film-forming additives, overcharge protection additives, and positive electrode protection additives. This effectively improves the charge-discharge performance of the lithium battery, reduces side reactions, thereby reducing battery gas buildup and extending battery cycle life. The film-forming additive, 1,3,5,2,4,6-trioxotrithionhexane-2,2,4,4,6,6-hexaoxide, inhibits the oxidation or reduction decomposition of the electrolyte on the electrode material surface, reducing electrode damage and improving the compatibility between the electrolyte and the electrode. This method improves the battery's cycle performance and storage performance at high temperatures to some extent, but its low-temperature discharge capability is limited to -30℃ or -40℃.

[0006] Patent publication number CN 111384446A discloses a wide-temperature electrolyte, a secondary battery, and their applications. This patent uses water and alcohol as solvents, and the solutes are composed of alkali metal salts, alkaline earth metal salts, main group metal salts, transition metal salts, and ammonium salts. The secondary battery assembled with this wide-temperature electrolyte exhibits normal charge and discharge characteristics within a temperature range of -80°C to 100°C, meeting the requirements for use in ambient temperature, extremely low temperature, and extremely high temperature environments. However, judging from the discharge performance of its embodiments, the wide-temperature electrolyte of this patent is only suitable for non-high-voltage systems, with voltage windows all below 3.0V; and the discharge capacity of the batteries is all less than 100mAh / g, with a discharge energy density not exceeding 100Wh / Kg.

[0007] Patent publication number CN 116565313 A discloses a wide-temperature electrolyte, a wide-temperature battery, and a preparation method. The wide-temperature electrolyte comprises a lithium salt, an organic solvent, and additives; the additives consist of bis(trimethylsilane)sulfite (BTMSS) and other additives. The trimethylsilyl group in BTMSS can react with water and HF in the electrolyte to improve the stability of the electrolyte under high temperature and high voltage conditions; it can also react with LiPF6 in the electrolyte to generate LiPF2O2, which has the ability to reduce impedance, thereby improving the low-temperature performance of the electrolyte. The sulfite group in BTMSS can form a highly ductile, low-impedance SEI layer rich in ROSO2Li at the negative electrode to accommodate the volume expansion of the silicon negative electrode during low-temperature cycling; moreover, the formed SEI layer is more dense and uniform, which can suppress the growth of lithium dendrites and the co-intercalation of PC and solvated lithium ions in the electrolyte. However, the working temperature range of the wide-temperature electrolyte in this patent is limited, specifically -40℃ to 55℃. The narrow operating temperature range and unclear performance at lower temperatures further complicate matters, with the highest capacity retention rate at -40℃ being only 85%. Furthermore, the electrolyte containing BTMSS additives in this patent has a complex manufacturing process: it requires complete dissolution of the raw materials, followed by ice bath and rotary evaporation steps, and finally recrystallization with n-heptane. This process is not easily simplified and is not conducive to continuous production. Moreover, the preparation of the BTMSS additives contains carcinogenic compounds such as tetrahydrofuran, posing a significant threat to the environment and human health, and thus lacks both environmental friendliness and safety.

[0008] Conventional commercial electrolytes used in lithium-ion batteries typically contain electrolytic electrolytes (EC). However, EC has a high freezing point (36.4℃), which increases the electrolyte's viscosity and may even cause partial solidification at low temperatures, thus reducing its ionic conductivity. This leads to increased charge transfer resistance at low temperatures, amplifying electrode polarization during charge and discharge. The Li-containing electrode within the bulk electrode... + The diffusion coefficient decreases sharply, leading to a significant increase in diffusion resistance; at low temperatures, the polarization is large, which easily causes Li to... + Lithium metal is formed by ion deposition on the anode. Current research reports that low-temperature lithium batteries generally exhibit poor high-temperature performance, while high-temperature lithium batteries show unsatisfactory low-temperature performance. Therefore, finding an electrolyte that balances specific energy and cycle performance, while also considering the battery's discharge performance at both high and low temperatures, to improve the battery's environmental adaptability and safety, is a pressing issue that needs to be addressed. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by proposing a dual-functional co-solvent wide-temperature lithium-ion battery electrolyte and its applications.

[0010] Specifically, this is achieved through the following technical solutions:

[0011] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, tris(trimethylsilane) phosphate (TMSP), and additives.

[0012] The lithium salt includes inorganic lithium salts and organic lithium salts; the inorganic lithium salt is one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), and lithium hexafluoroarsenate (LiAsF6); the organic lithium salt is one or more of lithium dioxalatoborate (LiBOB), lithium difluorooxalatoborate (LiDFOB), Li2DFB, lithium difluorosulfonate borate (LiBF2SO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0013] The organic solvent is one or more of carbonates, carboxylic esters, and fluorinated solvents.

[0014] The carbonate is one or both of cyclic carbonates and linear carbonates; the cyclic carbonate is one or more of ethylene carbonate (EC) and propylene carbonate (PC); the linear carbonate is one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and methyl propyl carbonate (MPC).

[0015] The carboxylic ester is one or both of cyclic carboxylic esters and linear carboxylic esters; the cyclic carboxylic ester is one or more of γ-butyrolactone (γ-BL) and γ-valerolactone (γ-VL); the linear carboxylic ester is one or more of methyl formate (MF), methyl acetate (MA), methyl propionate (MP), methyl butyrate (MB), ethyl formate (EF), ethyl acetate (EA), ethyl propionate (EP), ethyl butyrate (EB), isooctyl isooctanoate (EH), propyl acetate (PA), propyl butyrate (PB), propyl propionate (BB), and isobutyl formate (IF).

[0016] The fluorinated solvent is one or more of the following: trifluoroethyl acetate (TEFA), 2,2,2-trifluoroethyl n-butyl ester (TFENB), 2,2,2-trifluoroethyl n-hexyl ester (TFENH), 2,2,2-trifluoroethyl ether (BTFE), fluorinated alkyl phosphates, fluorinated phosphate amides, fluorinated esters, and fluorinated ethers.

[0017] The additive is one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), and propylene-1,3-sulfonate lactone (PES).

[0018] The concentration of lithium salt in the bifunctional cosolvent wide-temperature lithium-ion battery electrolyte is 0.5–2.0 mol / L, the total amount of thionyl chloride and tris(trimethylsilane) phosphate (TMSP) added is 0.5–20 wt%, and the amount of additive added is 0.1–10 wt%.

[0019] The mass ratio of thionyl chloride to tris(trimethylsilane) phosphate is (1-10):(1-10).

[0020] Application of the bifunctional co-solvent wide-temperature lithium-ion battery electrolyte in the preparation of lithium-ion batteries.

[0021] Application of the bifunctional co-solvent wide-temperature lithium-ion battery electrolyte in the preparation of lithium-ion full batteries.

[0022] The positive electrode material of the lithium-ion full battery is LiCoO2 or LiMn. x Fe 1-x PO4, Li[Ni x Co y (Al / Mn) 1-x-y One or more of O2.

[0023] The positive electrode of the lithium-ion full battery is an in-situ polymer composite thin film electrode deposited by radio frequency plasma polymerization of hexamethyldisiloxane.

[0024] The method for preparing the positive electrode of the lithium-ion full battery is as follows: the positive electrode material is mixed with binder and conductive agent, homogenized, and then coated onto the current collector. Then, hexamethyldisiloxane is polymerized and deposited onto the coated current collector by plasma radio frequency method to form an in-situ polymer composite thin film electrode.

[0025] The negative electrode material of the lithium-ion full battery is one or more of graphite and silicon-carbon / oxygen composite negative electrode materials.

[0026] Technical principle of the invention:

[0027] This invention provides a complete functional co-solvent continuous reaction chain, specifically: An in-situ polymer composite film positive electrode is obtained by polymer deposition of hexamethyldisiloxane under the action of radio frequency high-energy plasma. The hexamethyldisiloxane in the in-situ polymer composite film positive electrode reacts with phosphoric acid or phosphate, a product of electrolyte decomposition, at temperatures above 30°C to generate tris(trimethylsilyl)phosphate (TMSP). TMSP can generate a tris(trimethylsilane)ol intermediate at high temperatures, which can react with thionyl chloride to form a cyclic sulfite. Hexamethyldisiloxane, TMSP, and the cyclic sulfite are all wide-temperature co-solubility functional compounds. During the charge-discharge reaction process, the battery forms a continuous reaction cycle by directly reacting raw materials or intermediate products. The products of each step not only serve as reactants for the next reaction but also have multiple functional effects on battery performance improvement, acting on the lithiation and delithiation processes of lithium-ion batteries. This is a complete, spontaneous, and functional wide-temperature co-solvent continuous reaction ecosystem.

[0028] The cyclic sulfite product generated by the reaction of TMSP and thionyl chloride in the reaction chain of this invention is used as a low-temperature Li + The ligand has a freezing point below -100℃ and exhibits low-temperature eutectic properties. It is a key compound for improving the low-temperature conductivity of electrolytes, significantly enhancing the low-temperature characteristics of batteries and broadening the operating temperature range of lithium-ion batteries.

[0029] Beneficial effects:

[0030] 1. Effectively improves the high-temperature stability and safety of batteries: This invention utilizes hexamethyldisiloxane to obtain an in-situ polymer composite thin-film positive electrode through radio frequency high-energy plasma polymerization deposition. This composite thin-film positive electrode has uniform dispersion and high consistency. The Si-O bonds generated by pyrolysis are tightly bonded to the substrate surface, forming a natural organosilicon compound protective barrier. During charge and discharge, due to the high energy of the highest electron occupied orbital (HOMO) of the organosilicon compound, a low-impedance CEI interface layer is preferentially generated on the surface of the plasma-polymerized composite positive electrode sheet, thereby improving the cycle performance of the battery. At the same time, the positive electrode contains siloxane, which can react with trace amounts of HF in the electrolyte, improving the high-temperature stability of the electrolyte.

[0031] This invention uses TMSP as an electrolyte additive and also as an intermediate product in the reaction chain (acting again as an additive in the lithiation and delithiation processes of lithium-ion batteries). It has good flame retardant properties at high temperatures. When heated, it vaporizes and decomposes to release flame-retardant free radicals that capture hydrogen free radicals in the electrolyte system, preventing the chain reaction of hydrocarbon combustion or explosion, reducing the battery's heat release value and self-heating rate, and enhancing the thermal stability of the electrolyte itself. This avoids the battery from burning or exploding under overheating conditions, effectively improving the battery's safety performance.

[0032] 2. High specific gravity and volume expansion suppression: Tris(trimethylsilyl)phosphate (TMSP), as an electrolyte additive, can be oxidized and decomposed on the surface of the battery cathode at high potentials, generating a layer rich in silicates with good ion conductivity and electrochemically stable inorganic lithium carbonate. The silicates possess high Young's modulus and high mechanical strength, effectively suppressing the electrochemical expansion of lithium-ion batteries during cycling. TMSP exhibits Lewis basicity, forming a weak bond with lithium salts, thus stabilizing them. Furthermore, the positive electrode solid electrolyte interphase (SEI) film, containing fewer major electrolyte decomposition products (organic lithium carbonate and lithium fluoride), reduces the polarization voltage during charge and discharge, allowing the material to maintain good cycle performance and power characteristics during charging and discharging. Meanwhile, the Si-O bonds generated by the pyrolysis of the in-situ polymer composite film positive electrode sheet of the present invention are tightly bonded to the substrate surface, forming a natural organosilicon compound protective barrier. During the charging and discharging process, due to the high energy of the highest electron occupied orbital (HOMO) of the organosilicon compound, a CEI interface layer with lower impedance is preferentially generated on the surface of the plasma polymer composite positive electrode sheet, thereby improving the cycle performance of the battery.

[0033] 3. Wide temperature range with excellent high and low temperature compatibility: TMSP phosphate ester exhibits good flame retardant properties at high temperatures. Upon heating, it vaporizes and decomposes, releasing flame-retardant free radicals that capture hydrogen free radicals in the electrolyte system. This prevents the chain reaction of hydrocarbon combustion or explosion, reduces the battery's heat release and self-heating rate, and enhances the electrolyte's thermal stability, thereby preventing the battery from burning or exploding under overheating conditions and effectively improving battery safety. TMSP can generate a tris(trimethylsilane)ol intermediate at high temperatures, which can react with thionyl chloride to form cyclic sulfites. Cyclic sulfites act as a low-temperature Li + The ligand has a low freezing point and a high boiling point, and its viscosity is low at low temperatures. It is a preferred solvent for wide-temperature co-solvents, which can improve the conductivity of the electrolyte at low temperatures and enhance the low-temperature characteristics of the battery.

[0034] Therefore, by improving the positive electrode and electrolyte, the synergistic effect of the two not only reduces the polarization voltage of the battery during charge and discharge, improving high-temperature cycle performance and enhancing battery safety, but also lowers the freezing point of the electrolyte by reacting the intermediates of TMSP decomposition at high temperatures with thionyl chloride. This further broadens the wide temperature range of the electrolyte, improves the high and low temperature performance of the battery, and achieves the discharge characteristics of a dual-functional co-solvent electrolyte with high specific energy, low expansion, and wide temperature compatibility. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the fabrication process of a wide-temperature-range lithium-ion battery.

[0036] Figure 2 The image shows a comparison of the room temperature discharge curves of a bifunctional co-solvent wide-temperature lithium-ion battery electrolyte prepared in Example 1 and a basic electrolyte.

[0037] Figure 3 This is a comparison of the low-temperature discharge of a bifunctional co-solvent wide-temperature lithium-ion battery electrolyte prepared in Example 1 and the basic electrolyte at -60°C.

[0038] Figure 4 This is a comparison of high-temperature discharge at 80°C between a bifunctional co-solvent wide-temperature lithium-ion battery electrolyte prepared in Example 1 and a basic electrolyte. Detailed Implementation

[0039] The specific embodiments of the present invention will be described in further detail below, but the present invention is not limited to these embodiments. Any improvements or substitutions based on the basic spirit of these embodiments shall still fall within the scope of protection claimed by the claims of the present invention.

[0040] Example 1

[0041] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0042] The lithium salt is composed of inorganic lithium salt LiPF6 and organic lithium salt LiBOB in a mass ratio of 8:2.

[0043] The organic solvent is composed of EC, MF, and TFENH in a volume ratio of 30:40:30.

[0044] The additive is composed of VC and FEC in a mass ratio of 1:1.

[0045] The lithium salt concentration is 1.2 mol / L, the total addition amount of thionyl chloride and TMSP is 2.3 wt%, and the addition amount of the additive is 5 wt%; the mass ratio of thionyl chloride to TMSP is 3.5:6.5.

[0046] Example 2

[0047] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0048] The lithium salt is composed of inorganic lithium salt LiBF4 and organic lithium salt LiTFSI in a mass ratio of 6:4.

[0049] The organic solvent is composed of cyclic carbonate ethylene carbonate, linear carbonate, cyclic carboxylic acid ester γ-butyrolactone, linear carboxylic acid ester propyl acetate, and 2,2,2-trifluoroethyl n-butyl ester, wherein the volume ratio of carbonate, carboxylic acid ester, and fluorinated solvent is 70:20:10.

[0050] The additive is composed of fluoroethylene carbonate, 1,3-propanesulfonate lactone, and propenyl-1,3-sulfonate lactone in a mass ratio of 8:1:1.

[0051] The lithium salt concentration is 1.09 mol / L, the total amount of thionyl chloride and TMSP added is 0.85 wt%, and the amount of additive added is 8 wt%; the mass ratio of thionyl chloride and TMSP is 2:8.

[0052] Example 3

[0053] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0054] The lithium salt is composed of inorganic lithium salt LiPF6 and organic lithium salt LiFSI in a mass ratio of 9.5:0.5.

[0055] The organic solvent is a cyclic carbonate propylene carbonate, a cyclic carboxylic acid ester γ-butyrolactone, a linear carboxylic acid ester isobutyl formate, and trifluoroethyl acetate, wherein the volume ratio of the carbonate, carboxylic acid ester, and fluorinated solvent is 20:40:40.

[0056] The additive is composed of 1,3-propanesulfonate lactone and propenyl-1,3-sulfonate lactone in a mass ratio of 9:1.

[0057] The lithium salt concentration is 1.75 mol / L; the total amount of thionyl chloride and TMSP added is 6.5 wt%; the amount of additive added is 7 wt%; and the mass ratio of thionyl chloride to TMSP is 6:4.

[0058] Example 4

[0059] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0060] The lithium salt is composed of inorganic lithium salt LiPF6 and organic lithium salt lithium difluorosulfate borate LiBF2SO4 in a mass ratio of 5:5.

[0061] The organic solvent is a cyclic carbonate propylene carbonate, a cyclic carboxylic acid ester γ-valerolactone, a linear carboxylic acid ester isobutyl formate, methyl propionate, or trifluoroethyl acetate, wherein the volume ratio of the carbonate, carboxylic acid ester, and fluorinated solvent is 35:52:13.

[0062] The additive is composed of vinylene carbonate and 1,3-propanesulfonate lactone in a mass ratio of 6:4.

[0063] The lithium salt concentration is 0.92 mol / L, the total addition amount of thionyl chloride and TMSP is 8.7 wt%, the addition amount of the additive is 2.7 wt%, and the mass ratio of thionyl chloride to TMSP is 1.5:8.5.

[0064] Example 5

[0065] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0066] The lithium salt is composed of inorganic lithium salt LiPF6 and organic lithium salt lithium difluorosulfate borate LiBF2SO4 in a mass ratio of 7:3.

[0067] The organic solvent is a cyclic carbonate propylene carbonate, a linear carbonate diethyl carbonate, a linear carboxylic acid ethyl propionate, an ethyl butyrate, or a trifluoroethyl acetate, wherein the volume ratio of the carbonate, carboxylic acid ester, and fluorinated solvent is 42:55:3.

[0068] The additive is composed of fluoroethylene carbonate and propylene-1,3-sulfonyl lactone in a mass ratio of 5:5.

[0069] The lithium salt concentration is 1.86 mol / L; the total amount of thionyl chloride and TMSP added is 16 wt%; the amount of additive added is 4.6 wt%; and the mass ratio of thionyl chloride to TMSP is 4:6.

[0070] Example 6

[0071] A dual-functional co-solvent wide-temperature lithium-ion battery electrolyte is composed of lithium salt, organic solvent, thionyl chloride, TMSP, and additives.

[0072] The lithium salt is composed of LiBF4, lithium difluorosulfate borate LiBF2SO4, and lithium difluorooxalate borate LiDFOB in a mass ratio of 7:2:1.

[0073] The organic solvent is a cyclic carbonate propylene carbonate, a linear carbonate diethyl carbonate, methyl ethyl carbonate, a linear carboxylic acid ester, EH, and a fluorinated solvent fluorinated phosphate amide, wherein the volume ratio of the carbonate, carboxylic acid ester, and fluorinated solvent is 25:65:10.

[0074] The additive is propylene-1,3-sulfonyl lactone.

[0075] The lithium salt concentration is 0.6 mol / L, the total amount of thionyl chloride and TMSP added is 20 wt%, and the amount of additive added is 3.8 wt%; the mass ratio of thionyl chloride and TMSP is 7:3.

[0076] Application Example 1

[0077] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 1 was used in the preparation and application of lithium-ion batteries. LiCoO2 / Li[Ni 0.85 Co 0.10 Al 0.05 The O2 composite positive electrode and the silicon-carbon / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the lithium-ion full battery was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 1. The positive electrode was deposited via radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin-film electrode. The prepared electrode was wound to form a battery cell, which was then vacuum-dried and encapsulated in an aluminum-plastic film. Subsequent electrolyte injection was performed in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the battery cell, it was sealed. After aging and formation processes, vacuum degassing and secondary sealing were performed to assemble a single battery cell. The fabrication flow chart of the wide-temperature-range lithium-ion battery is shown below. Figure 1 As shown.

[0078] Using a basic electrolyte as a comparative example, another set of control batteries was assembled using the same positive and negative electrode formulations and assembly methods. The basic electrolyte was 1 mol / L LiPF6 / EC+PC+DMC (where the volume ratio of EC, PC, and DMC was 1:1:1).

[0079] Depend on Figure 2 It can be seen that, at room temperature, the discharge capacity of the wide-temperature electrolyte and the basic electrolyte in Example 1 is not significantly different. The battery using Example 1 has an initial discharge capacity of 2.437 Ah at 0.1C and 3.0–4.45V, an initial coulombic efficiency of 75.36%, an internal resistance of 27.90 mΩ, and an energy density of 295.1 Wh / Kg. Under the same test conditions, the basic electrolyte has an initial discharge capacity of 2.416 Ah, an internal resistance of 35.03 mΩ, and an energy density of 280.4 Wh / Kg. Therefore, the battery prepared with the wide-temperature electrolyte effectively reduces the internal resistance, increases the specific energy by 5%, and effectively improves the energy density.

[0080] from Figure 3It can be seen that the battery prepared with the wide-temperature electrolyte in Example 1 has a discharge capacity of 2.310 Ah at -60℃, with a capacity retention rate as high as 94.79%; while the battery prepared with the basic electrolyte has a discharge capacity of only 1.379 Ah, with a discharge capacity retention rate of only 57.08%, representing a 37% improvement in low-temperature discharge capacity retention. After being left at -60℃ for 4 hours, both batteries showed varying degrees of voltage decrease. In the initial stage of discharge, it was evident that due to the mismatch between the electron migration speed of the battery and the external circuit, severe polarization occurred, leading to a sharp voltage drop. The polarization voltage of the basic electrolyte plummeted to around 2.5V, resulting in poor discharge curve stability. This was due to the increased electrolyte viscosity and slower ion conduction at -60℃. The wide-temperature electrolyte in Example 1 showed significant improvement, increasing the polarization voltage from 2.5V to 2.8V, and resulting in a relatively smooth discharge curve with the discharge plateau maintained at around 2.3V. The discharge capacity retention rate was improved by nearly 40%. The results indicate that the prepared bifunctional cosolvent wide-temperature lithium-ion electrolyte has high ionic conductivity at -60℃. The sulfite produced by the chain reaction lowers the freezing point of the electrolyte, thus the wide-temperature electrolyte has excellent low-temperature discharge characteristics.

[0081] from Figure 4 It can be seen that the battery prepared with the electrolyte in Example 1 has a discharge capacity of 2.353 Ah at 80°C, with a capacity retention rate as high as 96.55%; while the battery prepared with the basic electrolyte has a discharge capacity of only 1.807 Ah, with a discharge capacity retention rate of only 74.79%. The temperature rise during discharge at 80°C decreased from 123°C to 95°C, indicating that the in-situ polymer composite film cathode deposited by hexamethyldisiloxane polymerization enhances the thermal stability of the electrolyte itself through the reaction product TMSP at high temperature. Compared with the 36% gas expansion rate of the basic electrolyte, the gas expansion rate of the battery prepared with the wide-temperature electrolyte is only 8%, effectively improving the safety performance of the battery.

[0082] Application Example 2

[0083] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 2 was used for the preparation and application in lithium-ion full batteries. Li[Ni] 0.75 Co 0.25 O2 / Li[Mn 0.8 Fe 0.2The PO4 composite positive electrode and the silicon-oxygen / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the full cell was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 2. The positive electrode was deposited by radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin film electrode. The prepared electrode was wound to form a cell, which was then vacuum-dried and encapsulated with an aluminum-plastic film. Subsequently, electrolyte was injected into the cell in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the cell, the cell was sealed. After aging and formation processes, vacuum degassing and secondary sealing were performed to assemble the cell into a single unit.

[0084] Application Example 3

[0085] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 3 was used for the preparation and application of lithium-ion full batteries. LiCoO2 / Li[Mn] 0.8 Fe 0.2 The PO4 composite positive electrode and the silicon-carbon / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the full cell was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 3. The positive electrode was deposited by radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin film electrode. The prepared electrode was wound to form a cell, which was then vacuum-dried and encapsulated in an aluminum-plastic film. Subsequently, electrolyte was injected into the cell in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the cell, the cell was sealed. After aging and formation processes, vacuum degassing and secondary sealing were performed to assemble a single cell.

[0086] Application Example 4

[0087] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 4 was used for the preparation and application in lithium-ion full batteries. Li[Ni] 0.9 Mn 0.1 O2 / Li[Ni 0.95 Co 0.02 Mn 0.03 The O2 composite positive electrode and the silicon-oxygen / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the full cell was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 4. The positive electrode was deposited by radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin film electrode. The prepared electrode was wound to form a cell, which was then vacuum-dried and encapsulated with an aluminum-plastic film. Subsequently, electrolyte was injected into the cell in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the cell, the cell was sealed. After aging and formation processes, vacuum degassing and secondary sealing were performed to assemble a single cell.

[0088] Application Example 5

[0089] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 5 was used for the preparation and application of lithium-ion full batteries. LiCoO2 / Li[Ni 0.88 Co 0.02 Mn 0.10 The O2 composite positive electrode and the silicon-oxygen / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the full cell was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 5. The positive electrode was deposited by radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin film electrode. The prepared electrode was wound to form a cell, which was vacuum dried and then encapsulated in an aluminum-plastic film. Subsequently, electrolyte was injected into the cell in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the cell, the cell was sealed. After the aging and formation processes were completed, vacuum degassing and secondary sealing were performed to assemble a single cell.

[0090] Application Example 6

[0091] The bifunctional co-solvent wide-temperature electrolyte prepared in Example 6 was used in the preparation and application of lithium-ion full batteries. Li[Ni] 0.90 Co 0.05 Mn 0.05 The O2 composite positive electrode and the silicon-carbon / graphite composite negative electrode were mixed, homogenized, coated, and dried for later use. The separator used in the full cell was Celgard 2325, and the electrolyte was the bifunctional co-solvent wide-temperature electrolyte prepared in Example 6. The positive electrode was deposited by radio frequency plasma polymerization with hexamethyldisiloxane to form an in-situ plasma-polymerized composite thin film electrode. The prepared electrode was wound to form a cell, which was then vacuum-dried and encapsulated in an aluminum-plastic film. Subsequently, electrolyte was injected into the cell in a drying room with a humidity of less than 3% RH. After the electrolyte completely wetted the cell, the cell was sealed. After aging and formation processes, vacuum degassing and secondary sealing were performed to assemble the cell into a single unit.

[0092] Table 1 below shows the discharge performance data for each application example:

[0093]

[0094] As can be seen from the data in Table 1 above, the dual-function co-solvent wide-temperature lithium-ion battery provided by the present invention not only has good high-temperature characteristics, but also has obvious discharge advantages under low-temperature conditions, strong wide-temperature compatibility, excellent safety performance, and excellent long-cycle performance.

Claims

1. A lithium-ion full battery, characterized in that, The electrolyte of the lithium-ion full battery is composed of lithium salt, organic solvent, thionyl chloride, tris(trimethylsilane) phosphate, and additives. The positive electrode material of the lithium-ion full battery is LiCoO2 or LiMn. x Fe 1-x PO4, Li[Ni x Co y (Al / Mn) 1-x-y One or more of O2; The positive electrode of the lithium-ion full battery is an in-situ polymer composite thin film electrode deposited by radio frequency plasma polymerization of hexamethyldisiloxane.

2. The lithium-ion full battery as described in claim 1, characterized in that, The lithium salt includes inorganic lithium salts and organic lithium salts; the inorganic lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate; the organic lithium salt is one or more of lithium dioxalate borate, lithium difluorooxalate borate, Li2DFB, lithium difluorosulfonate borate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

3. A lithium-ion full battery as described in claim 1, characterized in that, The organic solvent is one or more of carbonates, carboxylic esters, and fluorinated solvents.

4. A lithium-ion full battery as described in claim 3, characterized in that, The carbonate is one or both of cyclic carbonates and linear carbonates; the cyclic carbonate is one or more of ethylene carbonate and propylene carbonate; the linear carbonate is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

5. A lithium-ion full battery as described in claim 3, characterized in that, The carboxylic acid ester is one or both of cyclic carboxylic acid esters and linear carboxylic acid esters; the cyclic carboxylic acid ester is one or more of γ-butyrolactone and γ-valerolactone; the linear carboxylic acid ester is one or more of methyl formate, methyl acetate, methyl propionate, methyl butyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, EH, propyl acetate, propyl butyrate, propyl propionate, and isobutyl formate.

6. A lithium-ion full battery as described in claim 3, characterized in that, The fluorinated solvent is one or more of the following: trifluoroethyl acetate, 2,2,2-trifluoroethyl n-butyl ester, 2,2,2-trifluoroethyl n-hexyl ester, 2,2,2-trifluoroethyl ether, fluorinated alkyl phosphate, fluorinated phosphate amide, fluorinated ester, fluorinated ether, etc.

7. A lithium-ion full battery as described in claim 1, characterized in that, The additive is one or more of vinylene carbonate, fluorovinyl carbonate, 1,3-propanesulfonate lactone, and propenyl-1,3-sulfonate lactone.

8. A lithium-ion full battery as described in claim 1, characterized in that, The concentration of lithium salt in the electrolyte is 0.5–2.0 mol / L, the total amount of thionyl chloride and tris(trimethylsilane) phosphate (TMSP) added is 0.5–20 wt%, and the amount of the additive added is 0.1–10 wt%.

9. A lithium-ion full battery as described in claim 1, characterized in that, The negative electrode material in the lithium-ion full battery is one or more of graphite and silicon-carbon / oxygen composite materials.

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