Electrolyte, battery monomer and electric device

Abstract

The invention discloses an electrolyte, a battery monomer and a power utilization device, the electrolyte contains an additive, a lithium salt and a solvent, the additive comprises at least one of a cyclic siloxane additive and a cyclic silazane additive, based on the total mass of the electrolyte, the mass fraction of the additive is 0.1-15.0%, and the mass fraction of the lithium salt is 0.1-15.0%. The additive can be reduced and decomposed on the surface of the negative electrode prior to the solvent to form a solid electrolyte interface film (SEI) rich in polysiloxane, and the SEI has high mechanical stability, can significantly prolong the cycle life of the battery, and has wide application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte, a battery cell and a power utilization device. BACKGROUND

[0002] With the rapid development of portable electronic devices, electric vehicles and grid energy storage, people's demand for high energy density batteries is becoming more and more intense. Metal lithium has extremely high theoretical specific capacity and the lowest reduction potential, and becomes the most promising negative electrode material of high energy density batteries. A solid electrolyte interface film (SEI) is formed on the surface of the electrolyte and the lithium metal negative electrode. However, in the process of repeated lithium deposition / detachment, the lithium metal negative electrode undergoes a huge volume change, and the fragile SEI is easily destroyed, leading to continuous side reactions of the electrolyte and the metal lithium, affecting the cycle life. Therefore, it is crucial to enhance the mechanical stability of the SEI and improve the stability of the lithium metal negative electrode / electrolyte interface.

[0003] At present, there is no related report on enhancing the mechanical stability of the SEI by adding cyclic siloxane additives and cyclic silazane additives. SUMMARY

[0004] The present application provides an electrolyte, a battery cell and a power utilization device, which can enhance the mechanical stability of the SEI.

[0005] In a first aspect, the present application provides an electrolyte, comprising an additive, a lithium salt and a solvent; the mass fraction of the additive is 0.1% to 15.0% based on the total mass of the electrolyte; the additive comprises at least one of a cyclic siloxane additive and a cyclic silazane additive, wherein the cyclic siloxane additive has a structure as shown in formula (I), formula (II) or formula (III): (I), (II), (III), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 and R 24 are each independently selected from -H, C1-C6 alkyl, C1-C6 haloalkyl, C2-C 10 alkenyl, C6-C10 at least one of aryl, C3-C6cycloalkyl, heterocyclyl, cycloalkylalkyl, aralkyl, and heterocyclylalkyl.

[0006] In any embodiment of the present application, R1, R2, R3, R4, R5, R6are each independently selected from at least one of -H, C1-C5alkyl, C1-C5haloalkyl, C2-C8alkenyl, and C6-C8aryl; preferably, R1, R2, R3, R4, R5, R6are each independently selected from at least one of -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, -CH2-CH2-CH2-CH2-CH3, -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH=CH-CH2-CH3, -CX3, -CH2-CX3, -CH2-CH2-CX3, and phenyl, X is selected from at least one of F, Cl, Br, and I; more preferably, R1, R2, R3, R4, R5, R6are each independently selected from at least one of -H, -CH3, -CH2-CH2-CF3, -CH=CH2, and phenyl.

[0007] In any embodiment of the present application, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , and R 24 are each independently selected from at least one of -H, C1-C5alkyl, and C1-C5haloalkyl; preferably, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , and R 24Each of the following is independently selected from at least one of: -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, -CH2-CH2-CH2-CH2-CH3, -CX3, -CH2-CX3, and -CH2-CH2-CX3, and X is selected from at least one of F, Cl, Br, and I; more preferably, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24 Each is independently selected from at least one of -H and -CH3.

[0008] In any embodiment of this application, the cyclic siloxane additive includes at least one of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane, and hexaphenylcyclotrisiloxane.

[0009] In any embodiment of this application, the lithium salt includes at least one selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium nitrate; the molar concentration of the lithium salt is 0.5 mol / L based on the total mass of the electrolyte. −1 ~6.0 mol L −1 .

[0010] In any embodiment of this application, the solvent includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and ethylene glycol methyl ethyl ether.

[0011] In any embodiment of this application, the electrolyte further includes a diluent; the mass fraction of the diluent is 20% to 80% based on the total mass of the electrolyte.

[0012] In any embodiment of this application, the diluent has a structure as shown in formula (Ⅳ): (Ⅳ), Wherein, Rf1 and Rf2 are independently selected from C1 to C6 fluoroalkyl groups; preferably, the diluent includes at least one of bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether.

[0013] In a second aspect, this application provides a battery cell, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is the electrolyte described in the first aspect; optionally, the negative electrode includes at least one of lithium and lithium alloy; optionally, the battery cell includes at least one of lithium metal battery cell, sodium metal battery cell, lithium-ion battery cell, and sodium-ion battery cell.

[0014] Thirdly, this application provides an electrical device including the battery cell described in the second aspect.

[0015] Compared to existing technologies, this application introduces cyclic siloxanes or cyclic silazanes with specific structures and amounts into the electrolyte, enabling them to undergo ring-opening polymerization on the surface of the negative electrode, especially the lithium metal negative electrode, to construct a high-modulus, dense polymer layer in situ. This polymer layer significantly enhances the mechanical stability of the SEI, effectively alleviates SEI cracking and reconstruction, and reduces side reactions between the electrolyte and the negative electrode. Furthermore, the electrolyte formulation of this application achieves the above effects while also exhibiting excellent wettability and low additive dosage, demonstrating promising prospects for industrial application. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the cycle performance of the lithium metal battery electrolytes in Example 1, Comparative Example 1, and Comparative Example 2.

[0018] Figure 2 This is a schematic diagram of the cycle performance of the lithium metal battery electrolyte in Examples 1, 16, and 3 (Comparative Example 3).

[0019] Figure 3 This is a schematic diagram showing the mechanical stability test results of the lithium metal anode solid interface film in Example 1 and Comparative Example 1. Detailed Implementation

[0020] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the implementation details described in this specification are merely for illustrative purposes and are not intended to limit the scope of this application.

[0021] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0022] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0023] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0024] The anode, especially the lithium metal anode, is key to breaking through the energy density bottleneck of batteries, but its practical application is limited by the stability of the solid electrolyte interphase (SEI) film during cycling. During lithium deposition / deposition, the lithium metal anode undergoes huge volume deformation, and the fragile SEI is easily broken, leading to continuous side reactions between the electrolyte and the lithium metal anode, resulting in low battery coulombic efficiency and a sharp reduction in cycle life. Currently, stabilizing the interface through electrolyte additives is a common strategy. However, most existing additive technologies have significant shortcomings. Many traditional additives form an SEI with insufficient modulus, resulting in limited "toughening" effects and failing to effectively suppress the damage caused by lithium dendrite growth and volume changes. Other methods (such as artificial interface films) often suffer from problems such as complex processes, high costs, or excessive interfacial impedance, making it difficult to balance performance and industrialization prospects.

[0025] In view of this, the inventors have developed a novel electrolyte formulation by introducing a specific cyclic siloxane additive. This additive can undergo ring-opening polymerization on the surface of the lithium metal anode to form a high-modulus polymer layer in situ. This not only greatly enhances the mechanical stability of the SEI and effectively suppresses interfacial damage during cycling, but also requires a low amount of additive, is particularly suitable for lithium metal batteries with lithium metal as the anode, and has good compatibility with existing electrolyte systems. This provides a promising new path for the practical application of high-performance, long-life lithium metal batteries.

[0026] A first aspect of this application provides an electrolyte comprising an additive, a lithium salt, and a solvent; the additive has a mass fraction of 0.1% to 15.0% based on the total mass of the electrolyte; the additive comprises at least one of a cyclic siloxane additive and a cyclic silazane additive, wherein the cyclic siloxane additive has a structure as shown in formula (I), formula (II), or formula (III): (I) (II) (Ⅲ), where R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24 Each is independently selected from: -H, C1-C6 alkyl, C1-C6 haloalkyl, C2-C 10 alkenyl, C6-C 10 At least one of aryl, C3-C6 cycloalkyl, heterocyclic, cycloalkylalkyl, aralkyl, and heterocyclic alkyl.

[0027] By introducing cyclic siloxane additives with specific structures and dosages into the electrolyte, lithium salt is preferentially reduced to form inorganic components. Subsequently, the cyclic siloxane additives preferentially reduce the lithium metal anode surface, polymerizing to form high-modulus polysiloxanes, thus achieving the construction of a high-mechanical-strength SEI. Simultaneously, this additive requires low dosage and exhibits good wettability, achieving enhanced mechanical strength and stability of the SEI film while retaining excellent process and cost advantages, demonstrating significant industrialization potential.

[0028] In some embodiments, R1, R2, R3, R4, R5, and R6 are each independently selected from at least one of: -H, C1-C5 alkyl, C1-C5 haloalkyl, C2-C8 alkenyl, and C6-C8 aryl; preferably, R1, R2, R3, R4, R5, and R6 are each independently selected from: -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, and -CH2-CH2-CH2-CH2-CH 3. At least one of -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH=CH-CH2-CH3, -CX3, -CH2-CX3, -CH2-CH2-CX3 and phenyl, wherein X is selected from at least one of F, Cl, Br and I; more preferably, R1, R2, R3, R4, R5 and R6 are each independently selected from at least one of -H, -CH3, -CH2-CH2-CF3, -CH=CH2 and phenyl.

[0029] In some implementations, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24 Each is independently selected from at least one of: -H, C1-C5 alkyl, and C1-C5 haloalkyl; preferably, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24Each of the following is independently selected from at least one of: -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, -CH2-CH2-CH2-CH2-CH3, -CX3, -CH2-CX3, and -CH2-CH2-CX3, and X is selected from at least one of F, Cl, Br, and I; more preferably, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24 Each is independently selected from at least one of -H and -CH3.

[0030] In some embodiments, the cyclic siloxane additive includes at least one selected from octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane, and hexaphenylcyclotrisiloxane.

[0031] The aforementioned cyclic siloxane additives with specific structures, on the one hand, contribute to high modulus and enhance the mechanical stability of the SEI through ring-opening polymerization on the negative electrode surface to form a polymer layer containing silicon-oxygen chains (–Si–O–), thereby effectively resisting the volumetric deformation stress during lithium deposition / desorption. On the other hand, the diverse side groups introduced on the ring (such as methyl, phenyl, vinyl, and trifluoropropyl) play a key regulatory role. The large phenyl group can enhance the rigidity of the molecular chain and promote dense packing; the reactive vinyl group can participate in polymerization, significantly increasing the crosslinking density and strengthening the toughness of the polymer network; while the highly polar trifluoropropyl group can optimize the interfacial energy and promote the formation of a more uniform and stable protective layer. This synergistic effect of "silicon-oxygen backbone and multifunctional tunable side groups" enables these additives to precisely construct SEIs with both high mechanical strength and good adaptability through in-situ polymerization, fundamentally solving the problem of traditional SEIs being fragile and prone to breakage.

[0032] In some embodiments, the lithium salt includes at least one selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium tetrafluoroborate, and lithium nitrate; the molar concentration of the lithium salt is 0.5 mol / L based on the total mass of the electrolyte. −1 ~6.0 mol L −1 .

[0033] The selected lithium salt type and concentration range are crucial for the synergistic construction of a high-mechanical-stability SEI with cyclic siloxane additives. On one hand, the aforementioned lithium salt concentration reduces free solvent molecules, effectively minimizing solvent reduction and decomposition on the lithium metal anode surface, thus preventing the formation of a loose, thick, high-resistivity organic layer. Simultaneously, it increases the proportion of anions in the lithium-ion solvation structure, creating prerequisites for forming a robust SEI rich in inorganic matter, with low impedance and a dense structure. On the other hand, specific lithium salt anions (such as PF6)... − FSI − NO3⁻ can be preferentially reduced to generate SEI components rich in high-modulus inorganic substances such as LiF, Li3N, and Li2O. This results in a composite SEI with an upper layer of high-modulus polymer formed by the ring-opening polymerization of cyclic siloxanes and a lower layer of inorganic-rich layer generated by anion reduction. Through the composite reinforcement effect, the overall mechanical strength and toughness of the SEI are significantly improved, enabling it to better withstand the negative electrode volume changes during cycling.

[0034] In some embodiments, the solvent includes at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and ethylene glycol methyl ethyl ether.

[0035] The selected solvent system, through the synergistic effect of its physicochemical properties, lays the foundation for constructing a high-mechanical-stability SEI. Specifically, cyclic carbonates with high dielectric constants (such as ethylene carbonate and fluoroethylene carbonate) can ensure the effective dissociation of lithium salts, thus maintaining sufficient lithium-ion mobility and suppressing side reactions of free solvents in conjunction with a high-concentration lithium salt strategy. The introduction of linear carbonates (such as dimethyl carbonate and ethyl methyl carbonate) and linear ether solvents (such as ethylene glycol dimethyl ether) not only significantly improves the overall wettability of the electrolyte and lithium-ion transport kinetics, but also regulates the rate and extent of reduction polymerization of cyclic siloxanes at the electrode interface, promoting the formation of a more dense, uniform, and moderately tough high-modulus polymer / inorganic composite SEI.

[0036] In some embodiments, the electrolyte also includes a diluent; the mass fraction of the diluent is 20% to 80% based on the total mass of the electrolyte.

[0037] In some embodiments, the diluent has a structure as shown in formula (Ⅳ): (Ⅳ), Wherein, Rf1 and Rf2 are independently selected from C1 to C6 fluoroalkyl groups; preferably, the diluent includes at least one of bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether.

[0038] The aforementioned fluorinated ether diluents consist of two highly fluorinated alkyl groups (Rf1, Rf2) linked by low-polarity ether oxygen bonds. By controlling their mass fraction to 20%~80%, they can effectively reduce the overall viscosity of the electrolyte. At the same time, the introduction of the diluent can further increase the proportion of anions in the lithium-ion solvation structure and promote the formation of an inorganic-based SEI.

[0039] A second aspect of the embodiments of this application provides a battery cell, the battery cell including a positive electrode, a negative electrode and an electrolyte, the electrolyte being the electrolyte described in the first aspect; optionally, the negative electrode includes at least one of lithium and lithium alloy; optionally, the battery cell includes at least one of lithium metal battery cell, sodium metal battery cell, lithium-ion battery cell and sodium-ion battery cell.

[0040] Preferably, the negative electrode comprises lithium.

[0041] Preferably, the battery cell includes a lithium metal battery cell.

[0042] In lithium metal battery systems using lithium metal as the negative electrode, the lithium metal negative electrode undergoes significant volume deformation during charging and discharging, which continuously damages the solid electrolyte interphase (SEI) film on the electrode surface. The integrity and mechanical stability of the SEI directly affect the battery's cycle life, coulombic efficiency, and safety performance. This application introduces cyclic siloxane additives with specific structures and dosages into the electrolyte. Through synergistic effects with the lithium metal negative electrode, an SEI with high flexibility and high mechanical stability is constructed on the electrode surface. This effectively enhances the tolerance to volume changes of the lithium metal negative electrode, inhibits dendrite growth, and significantly improves the mechanical stability of the SEI. This electrolyte formulation is highly compatible with lithium metal battery systems and is the key to achieving high performance and long lifespan in this type of battery system.

[0043] A third aspect of the embodiments of this application provides an electrical device including the battery cell described in the second aspect.

[0044] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0045] The abbreviations for lithium salt, solvent, and diluent used in the following examples and comparative examples are as follows: Lithium salts: Lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium nitrate (LiNO3). All lithium salts were purchased from Suzhou Duoduo Chemical Technology Co., Ltd.

[0046] Solvents: Ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), fluoroethylene carbonate (FEC), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (2-DME), triethylene glycol dimethyl ether (3-DME), tetraethylene glycol dimethyl ether (4-DME), and ethylene glycol methyl ethyl ether (EGEME). EC, PC, DMC, DEC, EMC, FEC, DME, 2-DME, 3-DME, and 4-DME were all purchased from Suzhou Duoduo Chemical Technology Co., Ltd., and EGEME was purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0047] Diluents: bis(2,2,2-trifluoroethyl) ether was BTFE, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether was HFE-347, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether was HFE-458, and 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether was HFE-449. BTFE, HFE-347, and HFE-458 were purchased from Suzhou Duoduo Chemical Technology Co., Ltd., and HFE-449 was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0048] The button cell parameters in the examples and comparative examples are as follows: the battery configuration is type 2032, the positive electrode material is lithium nickel cobalt manganese oxide, and the areal capacity is 3.0 mAh cm⁻¹. −2 The negative electrode material is a lithium metal sheet with a thickness of 50 μm, the separator is polyethylene, and the electrolyte volume is 50 μL. The battery cycle life is calculated when the battery capacity drops to 80% of its initial capacity.

[0049] Example 1 A novel electrolyte, comprising lithium salts of LiPF6 and LiBOB (molar ratio 6:1), solvent of 2-DME and FEC mixed in a volume ratio of 2:1, diluent of HFE-458, and additive of octamethylcyclotetrasiloxane.

[0050] The preparation method of this electrolyte is as follows: LiPF6 and LiBOB were added to a mixed solvent of 2-DME and FEC to form an initial electrolyte. The molar concentration of lithium salts (LiPF6 and LiBOB) in the initial electrolyte was 8 mol / L. −1 HFE-458 diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 4 mol / L. −1 Finally, octamethylcyclotetrasiloxane is added to form the target electrolyte, with the mass fraction of octamethylcyclotetrasiloxane in the target electrolyte being 10%.

[0051] Example 2 A novel electrolyte, wherein the lithium salt is LiFSI, the solvent is a mixture of DMC and FEC in a volume ratio of 3:1, the diluent is BTFE, and the additive is decamethylcyclopentasiloxane.

[0052] The preparation method of this electrolyte is as follows: LiFSI was added to a mixed solvent of DMC and FEC to form the initial electrolyte, with a molar concentration of lithium salt (LiFSI) of 6 mol / L in the initial electrolyte. −1 BTFE diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 2 mol L. −1 Finally, decamethylcyclopentasiloxane is added to form the target electrolyte, with the mass fraction of decamethylcyclopentasiloxane in the target electrolyte being 5%.

[0053] Example 3 A novel electrolyte, wherein the lithium salt is LiTFSI, the solvent is a mixture of EC and DMC in a volume ratio of 3:7, the diluent is HFE-458, and the additive is octamethylcyclotetrasiloxane.

[0054] The preparation method of this electrolyte is as follows: LiTFSI was added to a mixed solvent of EC and DMC to form the initial electrolyte, with a molar concentration of lithium salt (LiTFSI) of 5 mol / L in the initial electrolyte. −1 HFE-458 diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 1 mol L. −1Finally, octamethylcyclotetrasiloxane is added to form the target electrolyte, with the mass fraction of octamethylcyclotetrasiloxane in the target electrolyte being 3%.

[0055] Example 4 A novel electrolyte, with LiPF6 as the lithium salt, EMC as the solvent, HFE-347 as the diluent, and hexamethylcyclotrisiloxane as the additive.

[0056] The preparation method of this electrolyte is as follows: LiPF6 was added to the EMC solvent to form the initial electrolyte, with a molar concentration of lithium salt (LiPF6) of 4 mol / L in the initial electrolyte. −1 HFE-347 diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 0.5 mol L. −1 Finally, hexamethylcyclotrisiloxane is added to form the target electrolyte, with a mass fraction of 2% for hexamethylcyclotrisiloxane in the target electrolyte.

[0057] Example 5 A novel electrolyte, wherein the lithium salts are LiTFSI and LiNO3 (molar ratio 4:1), the solvent is a mixed solvent of EC, DEC and DMC in a volume ratio of 1:1:1, the diluent is HFE-449, and the additive is hexaphenylcyclotrisiloxane.

[0058] The preparation method of this electrolyte is as follows: LiTFSI and LiNO3 were added to a mixed solvent of EC, DEC, and DMC to form the initial electrolyte. The molar concentration of lithium salts (LiTFSI and LiNO3) in the initial electrolyte was 5 mol / L. −1 HFE-449 diluent was added to the initial electrolyte to form a diluted electrolyte, in which the molar concentration of lithium salt was 0.2 mol L. −1 Finally, hexaphenylcyclotrisiloxane is added to form the target electrolyte, with a mass fraction of 1% for hexaphenylcyclotrisiloxane in the target electrolyte.

[0059] Example 6 A novel electrolyte, comprising lithium salts of LiTFSI and LiDFOB (molar ratio 5:1), solvent of 4-DME and FEC mixed in a volume ratio of 1:1, diluent of BTFE, and additive of 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane.

[0060] The preparation method of this electrolyte is as follows: LiTFSI and LiDFOB were added to a mixed solvent of 4-DME and FEC to form an initial electrolyte. The molar concentration of the lithium salts (LiTFSI and LiDFOB) in the initial electrolyte was 6 mol / L. −1 BTFE diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 1 mol L. −1 Finally, 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane is added to form the target electrolyte, with the mass fraction of 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane in the target electrolyte being 8%.

[0061] Example 7 A novel electrolyte, wherein the lithium salt is LiBF4, the solvent is a mixture of PC and 3-DME in a volume ratio of 1:1, the diluent is BTFE, and the additive is decamethylcyclopentasiloxane.

[0062] The preparation method of this electrolyte is as follows: LiBF4 was added to a mixed solvent of PC and 3-DME to form an initial electrolyte. The molar concentration of lithium salt (LiBF4) in the initial electrolyte was 4 mol / L. −1 BTFE diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 0.5 mol L. −1 Finally, decamethylcyclopentasiloxane is added to form the target electrolyte, with the mass fraction of decamethylcyclopentasiloxane in the target electrolyte being 5%.

[0063] Example 8 A novel electrolyte, wherein the lithium salt is LiTFSI, the solvent is a mixture of PC and DMC in a volume ratio of 2:8, the diluent is HFE-458, and the additive is 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane.

[0064] The preparation method of this electrolyte is as follows: LiTFSI was added to a mixed solvent of PC and DMC to form an initial electrolyte, with a molar concentration of lithium salt (LiTFSI) of 3 mol / L in the initial electrolyte. −1 HFE-458 diluent was added to the initial electrolyte to form a diluted electrolyte, in which the molar concentration of lithium salt was 0.8 mol L. −1 Finally, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is added to form the target electrolyte, with a mass fraction of 4% for 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the target electrolyte.

[0065] Example 9 A novel electrolyte, wherein the lithium salt is LiPF6, the solvent is a mixture of DMC and DEC in a volume ratio of 1:1, the diluent is HFE-449, and the additive is 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0066] The preparation method of this electrolyte is as follows: LiPF6 was added to a mixed solvent of DMC and DEC to form an initial electrolyte, with a molar concentration of lithium salt (LiPF6) of 6 mol / L in the initial electrolyte. −1 HFE-449 diluent was added to the initial electrolyte to form a diluted electrolyte, with a lithium salt molar concentration of 2 mol / L in the diluted electrolyte. −1 Finally, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane is added to form the target electrolyte, with the mass fraction of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane in the target electrolyte being 7%.

[0067] Example 10 A novel electrolyte, wherein the lithium salt is LiTFSI and LiBF4 (molar ratio of 2:1), the solvent is a mixed solvent of DME and FEC in a volume ratio of 4:1, the diluent is HFE-347, and the additive is octamethylcyclotetrasiloxane.

[0068] The preparation method of this electrolyte is as follows: LiTFSI and LiBF4 were added to a mixed solvent of DME and FEC to form the initial electrolyte. The molar concentration of the lithium salts (LiTFSI and LiBF4) in the initial electrolyte was 8 mol / L. −1 HFE-347 diluent was added to the initial electrolyte to form a diluted electrolyte, with a lithium salt molar concentration of 2 mol / L in the diluted electrolyte. −1 Finally, octamethylcyclotetrasiloxane is added to form the target electrolyte, with the mass fraction of octamethylcyclotetrasiloxane in the target electrolyte being 5%.

[0069] Example 11 A novel electrolyte, wherein the lithium salts are LiFSI and LiPF6 (molar ratio 1:1), the solvent is EGEME, the diluent is HFE-458, and the additive is 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane.

[0070] The preparation method of this electrolyte is as follows: LiFSI and LiPF6 were added to EGEME solvent to form the initial electrolyte, with a molar concentration of 5 mol / L for the lithium salts (LiFSI and LiPF6) in the initial electrolyte. −1 HFE-458 diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 0.5 mol L. −1 Finally, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is added to form the target electrolyte, with the mass fraction of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane in the target electrolyte being 2%.

[0071] Example 12 A novel electrolyte, wherein the lithium salt is LiFSI, LiTFSI and LiBOB (molar ratio of 5:4:1), the solvent is a mixed solvent of 4-DME, DMC and FEC in a volume ratio of 2:2:1, the diluent is HFE-449, and the additive is 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0072] The preparation method of this electrolyte is as follows: LiFSI, LiTFSI, and LiBOB were added to a mixed solvent of 4-DME, DMC, and FEC to form the initial electrolyte. The molar concentration of the lithium salts (LiFSI, LiTFSI, and LiBOB) in the initial electrolyte was 6 mol / L. −1 HFE-449 diluent was added to the initial electrolyte to form a diluted electrolyte, with a lithium salt molar concentration of 2 mol / L in the diluted electrolyte. −1 Finally, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane is added to form the target electrolyte, with the mass fraction of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane in the target electrolyte being 5%.

[0073] Example 13 A novel electrolyte, wherein the lithium salts are LiFSI, LiBOB and LiDFOB (molar ratio of 8:1:1), the solvent is a mixed solvent of 3-DME, EMC and DEC in a volume ratio of 7:2:1, the diluent is HFE-347, and the additive is 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane.

[0074] The preparation method of this electrolyte is as follows: LiFSI, LiBOB, and LiDFOB were added to a mixed solvent of 3-DME, EMC, and DEC to form an initial electrolyte. The molar concentration of the lithium salts (LiFSI, LiBOB, and LiDFOB) in the initial electrolyte was 6 mol / L. −1 HFE-347 diluent was added to the initial electrolyte to form a diluted electrolyte, with a lithium salt molar concentration of 2 mol / L in the diluted electrolyte. −1 Finally, 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane is added to form the target electrolyte, with the mass fraction of 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane in the target electrolyte being 10%.

[0075] Example 14 A novel electrolyte, wherein the lithium salt is LiTFSI, LiPF6 and LiNO3 (molar ratio of 8:1:1), the solvent is a mixed solvent of DMC, PC and EMC in a volume ratio of 6:2:2, the diluent is BTFE, and the additive is 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane.

[0076] The preparation method of this electrolyte is as follows: LiTFSI, LiPF6, and LiNO3 were added to a mixed solvent of DMC, PC, and EMC to form the initial electrolyte. The molar concentration of the lithium salts (LiTFSI, LiPF6, and LiNO3) in the initial electrolyte was 5 mol / L. −1 BTFE diluent was added to the initial electrolyte to form a diluted electrolyte, wherein the molar concentration of lithium salt in the diluted electrolyte was 1 mol L. −1 Finally, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane is added to form the target electrolyte, with a mass fraction of 4% in the target electrolyte.

[0077] Example 15 A novel electrolyte, wherein the lithium salts are LiTFSI, LiDFOB and LiBF4 (molar ratio of 6:2:2), the solvent is a mixed solvent of DMC, EC and FEC in a volume ratio of 1:1:1, the diluent is HFE-449, and the additive is decamethylcyclopentasiloxane.

[0078] The preparation method of this electrolyte is as follows: LiTFSI, LiDFOB, and LiBF4 were added to a mixed solvent of DMC, EC, and FEC to form an initial electrolyte. The molar concentration of the lithium salts (LiTFSI, LiDFOB, and LiBF4) in the initial electrolyte was 6 mol / L. −1 HFE-449 diluent was added to the initial electrolyte to form a diluted electrolyte, with a lithium salt molar concentration of 2 mol / L in the diluted electrolyte. −1 Finally, decamethylcyclopentasiloxane is added to form the target electrolyte, with a mass fraction of 6% for decamethylcyclopentasiloxane in the target electrolyte.

[0079] Example 16 A novel electrolyte differs from Example 1 only in the mass fraction of the additive in the target electrolyte. Specifically, the mass fraction of octamethylcyclotetrasiloxane in the target electrolyte is 5%.

[0080] Comparative Example 1 A novel electrolyte differs from Example 1 only in that it does not contain the additive octamethylcyclotetrasiloxane.

[0081] Comparative Example 2 A novel electrolyte differs from Example 1 only in the type of additive, specifically by replacing the additive in equal amounts with tetramethyltetraphenylcyclotetrasiloxane.

[0082] Comparative Example 3 A novel electrolyte differs from Example 1 only in the mass fraction of the additive in the target electrolyte. Specifically, the mass fraction of octamethylcyclotetrasiloxane in the target electrolyte is 20%.

[0083] Performance testing 1. The test method for battery cycle life is as follows: Battery assembly: Using LiNi0.5Co0.2Mn0.3O2 (NCM523) as the positive electrode active material, aluminum foil as the positive electrode current collector, lithium metal as the negative electrode, copper foil as the negative electrode current collector, and polyethylene as the separator, CR2032 type button batteries were assembled in a glove box filled with argon atmosphere (oxygen content <0.01ppm, water content <0.01ppm) in the following order: positive electrode-electrolyte-separator-electrolyte-negative electrode. The electrolyte system in the battery adopted the target electrolyte systems prepared in Examples 1–16 and Comparative Examples 1–3 above.

[0084] Charge / Discharge Procedure: The assembled battery is subjected to charge / discharge cycle testing using a battery testing system such as Blue Electric or Newway at a constant temperature of 25°C. Before the cycle test, three activation cycles are performed: charging at 0.1C to 4.3V and discharging at 0.1C to 2.8V. The cycle test uses a constant current-constant voltage (CC-CV) charging mode and a constant current (CC) discharging mode. Specific parameters can be set as follows: Charging: Charge at a constant current rate of 0.4 C to 4.3 V, then charge at a constant voltage of 4.3 V until the current decays to 0.05 C.

[0085] Discharge: Discharge at a constant current rate of 0.4 C to 2.8 V.

[0086] Cycle life determination: The above charge-discharge procedure is considered as one cycle, and tests are conducted continuously. The cycle life of a battery is defined as the number of cycles completed before the battery's discharge capacity first decays to 80% of its initial discharge capacity.

[0087] Data recording and analysis: Record the discharge capacity for each cycle and calculate its capacity retention rate relative to the discharge capacity of the first cycle of the cycle test. When the capacity retention rate drops to 80%, record the corresponding number of cycles, which is the cycle life of the battery.

[0088] 2. The test method for the mechanical stability of the solid electrolyte interface film of lithium metal anode is as follows (in-situ method): The mechanical stability of the solid electrolyte interphase (SEI) membrane was tested using electrochemical atomic force microscopy (EC-AFM).

[0089] Testing Procedure: An electrochemical workstation was used in conjunction with an atomic force microscope (AFM) in a glove box filled with argon atmosphere (oxygen content <0.01 ppm, water content <0.01 ppm). A three-electrode system was employed, with highly oriented pyrolytic graphite as the working electrode and lithium metal as the counter and reference electrodes. The three-electrode system was sealed with an 8 mm diameter O-ring. Testing was conducted at 1 mV s. −1 At the scan rate, the electrode potential was negatively scanned from the open-circuit voltage to 0.4 V (vs. Li / Li). + Then test the elastic modulus.

[0090] The test results are shown in Table 1. Figure 1 This is a schematic diagram showing the cycle performance of the lithium metal battery electrolytes in Example 1, Comparative Example 1, and Comparative Example 2. Figure 2 This is a schematic diagram of the cycle performance of the lithium metal battery electrolyte in Examples 1, 16, and 3 (Comparative Example 3). Figure 3 This is a schematic diagram showing the mechanical stability test results of the lithium metal anode solid interface film in Example 1 and Comparative Example 1.

[0091] Table 1 The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. An electrolyte, characterized in that, additives, lithium salts and solvents; a mass fraction of the additives is 0.1% to 15.0% based on the total mass of the electrolyte; the additives comprise at least one of a cyclic siloxane additive and a cyclic silazane additive, wherein the cyclic siloxane additive has a structure as shown in formula (I), formula (II) or formula (III): (I) (II) (Ⅲ), where R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 21 R 22 R 23 and R 24 Each is independently selected from: -H, C1-C6 alkyl, C1-C6 haloalkyl, C2-C 10 alkenyl, C6-C 10 At least one of aryl, C3-C6 cycloalkyl, heterocyclic, cycloalkylalkyl, aralkyl, and heterocyclic alkyl.

2. The electrolyte according to claim 1, characterized in that, each of R1, R2, R3, R4, R5 and R6 is independently selected from at least one of -H, C1-C5 alkyl, C1-C5 haloalkyl, C2-C8 alkenyl and C6-C8 aryl; each of R1, R2, R3, R4, R5 and R6 is independently selected from at least one of -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, -CH2-CH2-CH2-CH2-CH3, -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH=CH-CH2-CH3, -CX3, -CH2-CX3, -CH2-CH2-CX3 and phenyl, wherein X is selected from at least one of F, Cl, Br and I; each of R1, R2, R3, R4, R5 and R6 is independently selected from at least one of -H, -CH3, -CH2-CH2-CF3, -CH=CH2 and phenyl.

3. The electrolyte of claim 1, wherein R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 and R 24 are each independently selected from at least one of: -H, C1-C5 alkyl, and C1-C5 haloalkyl; Preferably, said R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 and R 24 are each independently selected from at least one of: -H, -CH3, -CH2CH3, -CH2-CH2-CH3, -CH2-CH2-CH2-CH3, -CH2-CH2-CH2-CH2-CH3, -CX3, -CH2-CX3and -CH2-CH2-CX3, said X being selected from at least one of F, Cl, Br and I; More preferably, each of R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , and R 24 is independently selected from at least one of -H and -CH3.

4. The electrolyte of claim 1, wherein the cyclic siloxane additive comprises at least one of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, 2,4,6-trimethyl-2,4,6-triphenylcyclotrisiloxane and hexaphenylcyclotrisiloxane.

5. The electrolyte of claim 1, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate and lithium tetrafluoroborate, lithium nitrate; a molar concentration of the lithium salt of 0.5 to 6.0 mol L based on the total mass of the electrolyte −1 ~6.0mol L −1 .

6. The electrolyte of claim 1, wherein the solvent comprises at least one of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and ethylene glycol methyl ethyl ether.

7. The electrolyte of claim 1, wherein the electrolyte further comprises a diluent; a mass fraction of the diluent is 20% to 80% based on the total mass of the electrolyte.

8. The electrolyte of claim 7, wherein, the diluent has a structure as shown in formula (IV): （Ⅳ）， wherein Rf1 and Rf2 are independently selected from C1-C6 fluoroalkyl; preferably, the diluent comprises at least one of bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether.

9. A battery cell characterized by, the battery cell comprises a positive electrode, a negative electrode and an electrolyte, and the electrolyte is the electrolyte according to any one of claims 1 to 8. Optionally, the negative electrode comprises at least one of lithium and lithium alloy. Optionally, the battery cell comprises at least one of a lithium metal battery cell, a sodium metal battery cell, a lithium ion battery cell, and a sodium ion battery cell.

10. An electrical device, characterized by A battery cell comprising the battery cell of claim 9.

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