Electrolyte and method for its preparation, half-cell, battery

Abstract

This invention discloses an electrolyte, its preparation method, a half-cell, and a battery. The electrolyte comprises a lithium salt, an organic solvent, and a diluent. The organic solvent is an orthoformate compound used to dissolve the lithium salt and regulate the solid-state electrolyte interface of the battery. The diluent is a fluorobenzene compound used to regulate the viscosity and flowability of the electrolyte. The special lithium-ion-anion coordination structure formed by the orthoformate compound in the electrolyte induces the formation of an inorganic-rich interface layer, improving the compatibility of the electrolyte with the lithium metal anode. This solves the problems of high viscosity, low conductivity, and poor wettability with the separator in high-concentration electrolytes. The electrolyte has high lithium metal stability, enabling the lithium-copper half-cell to have high coulombic efficiency. The electrolyte also has thermal stability and chemical compatibility, solving the lithium dendrite problem of the lithium metal anode. It is suitable for the development and application of high coulombic efficiency lithium metal batteries. The preparation method of the electrolyte is simple, has broad application prospects, is low in cost, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to electrolytes and their preparation methods, half-cells, and batteries. Background Technology

[0002] Lithium metal batteries are considered a strong candidate for next-generation battery technology due to their extremely low electrochemical reduction potential (-3.04 V, relative to a standard hydrogen electrode) and ultra-high theoretical specific capacity (3860 mAh / g). However, lithium metal batteries still face many challenges in commercial applications, especially in the compatibility of the electrolyte and the lithium metal anode, leading to problems such as lithium dendrite growth and increased risks. Current commercial electrolyte systems cannot form a stable solid-state electrolyte interface on the surface of the lithium metal anode, a problem that causes lithium dendrite growth and increases the risk of battery explosion.

[0003] The compatibility between the electrolyte and the lithium metal anode is one of the key bottlenecks in the development of lithium metal batteries. An ideal electrolyte should form a stable SEI (Solid Electrolyte Interphase) layer on the surface of the lithium metal anode to suppress lithium dendrite growth and electrolyte decomposition, thereby improving the battery's coulombic efficiency and cycle stability. However, traditional electrolyte systems often fail to meet this requirement, leading to side reactions at the lithium metal anode during charge and discharge, forming an unstable SEI layer, and consequently affecting battery performance. Localized-High Concentration Electrolyte (LHCE) is a novel electrolyte system developed based on High Concentration Electrolyte (HCE). LHCE introduces an inert solvent as a diluent to localize the high-concentration region, diluting the electrolyte solution while maintaining the original close ion pairs, ion aggregates, and other solution structures. This design not only reduces the viscosity of the electrolyte and increases ionic conductivity, but also improves its wettability with the separator and electrode materials, thus achieving a combination of physicochemical properties and electrochemical performance that integrate high-concentration and dilute solutions. Furthermore, the locally concentrated electrolyte also performs exceptionally well in suppressing lithium dendrite growth and increasing battery energy density, providing a new solution for the practical application of lithium metal batteries.

[0004] In locally concentrated electrolytes (LHCE), although ether solvents have high solubility and good ionic conductivity, they also have problems such as narrow voltage window and easy strong complexation with lithium ions.

[0005] Therefore, how to provide a novel solvent with high stability of lithium metal anodes is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides an electrolyte and its preparation method, a half-cell, and a battery, to provide a novel solvent with high stability of lithium metal anode.

[0007] In a first aspect, this application provides an electrolyte comprising a lithium salt, an organic solvent, and a diluent; wherein the organic solvent is an orthoformate compound used to dissolve the lithium salt and regulate the solid electrolyte interface of the battery, and the diluent is a fluorobenzene compound used to regulate the viscosity and flowability of the electrolyte.

[0008] Optionally, the lithium salt is used to provide lithium ions, including at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0009] Optionally, the orthoformate compounds include at least one of trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, and tributyl orthoformate.

[0010] Optionally, the fluorobenzene compounds include at least one of fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, and 1,3,5-trifluorobenzene.

[0011] Optionally, the molar ratio of lithium salt to organic solvent ranges from (1:1) to (1:5), and the molar ratio of lithium salt to diluent ranges from (1:1) to (1:10).

[0012] Secondly, this application provides a method for preparing an electrolyte, comprising the following steps: S1: Add lithium salt to an organic solvent to obtain a lithium salt organic dispersion; S2: Add diluent to the lithium salt organic dispersion, stir, and let stand to obtain the electrolyte.

[0013] Optionally, step S1 includes mixing the organic solvent and lithium salt in a glove box protected by an inert atmosphere.

[0014] Optionally, in step S2, the stirring time shall be no less than 1 hour and the standing time shall be no less than 2 hours.

[0015] Thirdly, this application provides a half-cell comprising the above-mentioned electrolyte; the coulombic efficiency of the half-cell is not less than 99%.

[0016] Fourthly, this application provides a battery, including an electrolyte, a negative electrode current collector, a metal negative electrode, a separator, a positive electrode and a positive electrode current collector, wherein the electrolyte is the aforementioned electrolyte; Electrolyte wets the negative electrode current collector, the metal negative electrode, the positive electrode, the positive electrode current collector, and the diaphragm.

[0017] Compared with the prior art, the electrolyte, its preparation method, half-cell, and battery provided by the present invention achieve at least the following beneficial effects: This invention provides an electrolyte and its preparation method, a half-cell, and a battery. The electrolyte includes a lithium salt, an organic solvent, and a diluent. The organic solvent is an orthoformate compound, used to dissolve the lithium salt and regulate the solid-state electrolyte interface of the battery. The diluent is a fluorobenzene compound, used to regulate the viscosity and flowability of the electrolyte. The orthoformate compound can form a special lithium-ion-anion coordination structure in the electrolyte, inducing the formation of an inorganic-rich interface layer, improving the compatibility of the electrolyte with the lithium metal anode, and solving the problems of high viscosity, low conductivity, and membrane wetting associated with high-concentration electrolytes. Overcoming issues such as poor stability, this electrolyte exhibits high lithium metal stability, enabling lithium-copper half-cells to achieve high coulombic efficiency. It also possesses excellent thermal stability and chemical compatibility, resolving the lithium dendrite problem faced by lithium metal anodes. This makes it suitable for the development and application of high-coulombic-efficiency lithium metal batteries. The preparation method is simple, and its application prospects are broad. Using fluorobenzene compounds as diluents, compared to commonly used polyfluoroether diluents, fluorobenzene compounds offer advantages such as readily available raw materials, lower cost, and more mature synthesis processes. This low-cost electrolyte is suitable for industrial production.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0019] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0021] Figure 1 These are Aurbach performance curves of lithium copper half-cells at 25°C in Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1 provided by the present invention. Figure 2 These are the long-cycle test curves of the lithium copper half-cells in Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1 provided by the present invention at 25°C. Figure 3 These are the Aurbach performance curves of the lithium copper half-cells in Embodiments 4, 5, 6 and Comparative Example 1 provided by this invention at 25°C. Figure 4 These are the long-cycle test curves of the lithium copper half-cells in Embodiments 4, 5, 6 and Comparative Example 1 provided by the present invention at 25°C. Figure 5 This is a flowchart of an electrolyte preparation method provided by the present invention; Figure 6 This is a partial structural diagram of a battery provided by the present invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0023] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0025] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0027] 1. Electrolyte The present invention provides an electrolyte comprising a lithium salt, an organic solvent, and a diluent; wherein the organic solvent is an orthoformate compound, which is used to dissolve the lithium salt and regulate the solid electrolyte interface of the battery, and the diluent is a fluorobenzene compound, which is used to regulate the viscosity and flowability of the electrolyte.

[0028] Specifically, an electrolyte is an ionic conductor capable of conducting electricity. It serves as an ion transport bridge connecting the positive and negative electrodes of a battery and is also the core medium for realizing electrochemical reactions. The functions of the electrolyte include: (1) transporting ions to complete charge cycling, enabling the battery's charging and discharging reactions to proceed smoothly; (2) constructing a stable electrode-electrolyte interface layer; (3) stabilizing the electrode structure and participating in electrochemical reactions; and (4) maintaining the electroneutrality of the entire battery system to ensure the continuous and stable progress of electrochemical reactions. The electrolyte provided in this embodiment includes lithium salt, organic solvent, and diluent. The organic solvent is a formate ester compound, and the diluent is a fluorobenzene compound. The descriptions of the components of the electrolyte are as follows: 1. Lithium salts: provide lithium ions (Li... +Lithium ions are not only the conductive ion current carriers during charging and discharging, and the electrochemical reactions connecting the positive and negative electrodes, but also energy storage units. They convert chemical energy into electrical energy through intercalation / deintercalation. The battery's capacity, charging speed, cycle life, and safety performance parameters all depend on the migration efficiency, intercalation / deintercalation ability, and stability of lithium ions. In addition, the lithium salt provided in this embodiment is insoluble in diluents but soluble in organic solvents. Therefore, when preparing the electrolyte, the lithium salt is first dissolved in an organic solvent to form a lithium salt organic dispersion, and then a diluent is added to the lithium salt organic dispersion to finally obtain the electrolyte. 2. Organic solvents: These possess high dielectric constants. Higher dielectric constants result in a stronger ability to dissolve lithium salts. Organic solvents dissolve lithium salts through their polarity, ionizing them into freely moving lithium ions and corresponding anions, providing the basis for ionic conductivity in the battery. Organic solvents also exhibit fluidity, enabling the construction of lithium ion migration channels and ensuring high ionic conductivity. Furthermore, organic solvents participate in the formation of the SEI layer, protecting the stability of the battery's negative electrode. With high boiling points and low freezing points, organic solvents, as a major component of the electrolyte, can regulate the battery's high and low temperature performance, broadening its application scenarios. In addition to protecting the negative electrode, organic solvents can also reduce structural collapse and transition metal ion dissolution in the positive electrode through interaction with the positive electrode material, stabilizing the electrode material and suppressing the formation of side reactions. The organic solvent provided in this embodiment is an orthoformate compound. The orthoformate molecule is composed of one carbon atom connected to three oxygen atoms. Compared with the conventional carbon atom which is usually connected to one or two atoms, the unique structure of the orthoformate molecule can protect the active site in the middle, reducing the reactivity of the organic solvent molecule.

[0029] 3. Diluent (1) Definition: It is a type of functional solvent component specifically used to optimize the physical and electrochemical properties of electrolyte. It can be understood as: a solvent that is used in combination with high dielectric constant solvents to reduce the overall viscosity of the electrolyte and improve its fluidity as the primary goal, while also helping to improve electrode wettability and low-temperature performance, and does not undertake the main task of lithium salt dissociation itself.

[0030] (2) The role of diluent in electrolyte: 1) Reduce electrolyte viscosity and improve lithium-ion conductivity: While high dielectric constant solvents can efficiently dissociate lithium salts, their strong molecular polarity and large intermolecular forces result in extremely high viscosity. In contrast, diluents have simpler molecular structures, weaker intermolecular forces, and extremely low viscosity. When diluents are combined with solvents, the overall viscosity of the electrolyte can be significantly reduced, directly reducing the migration resistance of lithium ions in the electrolyte. This allows lithium ions to be transported between the positive and negative electrodes more quickly, thereby improving the battery rate performance and reducing the concentration polarization of lithium ions in the electrolyte. 2) Improve the electrode wettability of the electrolyte and enhance the utilization rate of active materials: Both the positive and negative electrodes of lithium-ion batteries have porous structures. The electrolyte needs to fully penetrate into the pores of the electrodes to allow lithium ions to fully contact the active materials and complete the insertion / extraction reaction. The low viscosity of the diluent can improve the fluidity and wettability of the electrolyte. Low viscosity electrolyte can penetrate into the tiny pores of the electrodes more quickly, reducing the unwetted areas of the electrolyte. Some diluents have low surface tension, which can better adhere to the surface of the electrode particles and form a uniform electrolyte film, avoiding the waste of active materials due to local lack of liquid. The improvement of electrode wettability can significantly improve the battery's initial coulombic efficiency and capacity utilization. 3) Optimize low-temperature performance and reduce capacity decay at low temperatures: Low temperatures can cause a sharp increase in electrolyte viscosity and a significant decrease in lithium-ion migration rate, which may even prevent them from properly intercalating into the negative electrode, resulting in a sharp drop in battery capacity at low temperatures. The addition of diluent can lower the freezing point of the electrolyte and prevent it from freezing or becoming excessively viscous at low temperatures. Even at low temperatures, the diluent can maintain a low viscosity to ensure the basic migration ability of lithium ions. 4) Regulate SEI layer formation to help improve interface stability: Diluents have low reducing activity, which can regulate the reducing activity of solvent molecules in the electrolyte, slow down excessive solvent decomposition, and prevent the SEI layer from becoming too thick or developing pores. Some diluents can also introduce components such as lithium fluoride into the SEI layer, improve the mechanical flexibility and ionic conductivity of the SEI layer, and reduce capacity decay caused by SEI layer rupture during cycling.

[0031] The diluent provided in this embodiment is a fluorobenzene compound. A fluorobenzene compound molecule consists of at least one benzene ring and one fluorine atom. Using a fluorobenzene compound as a diluent has the following advantages: 1) Regulate the SEI layer to suppress lithium dendrite growth: Fluorobenzene compounds have high fluorine-donating capacity and low energy levels of the lowest unoccupied molecular orbitals, making them easy to undergo electrochemical reduction reactions on the surface of lithium anodes to generate lithium fluoride (LiF). The SEI layer rich in lithium fluoride has high strength, large surface energy and good electrochemical stability, which can effectively block the continuous reaction between the electrolyte and the lithium anode, while inhibiting the disordered growth of lithium dendrites. 2) Achieve localized high-concentration effects while reducing costs: Fluorobenzene compounds have extremely low binding energy with lithium ions. When added as a diluent, they can reduce the overall lithium salt concentration and cost of the electrolyte, while maintaining the local solvation structure of lithium ions and achieving a local high concentration effect. 3) Optimize the physicochemical properties of the electrolyte: Fluorobenzene compounds have low density and low viscosity. When added to high-concentration electrolytes, they can significantly reduce the overall viscosity of the electrolyte and improve the lithium-ion migration rate. Fluorobenzene compounds have good compatibility with mainstream electrolyte solvents such as carbonates, which can ensure the uniformity and stability of the electrolyte system. At the same time, they can also enhance the wettability of the electrolyte to the electrodes and help the smooth transport of ions during battery charging and discharging. 4) Adaptable to various operating conditions, improving overall battery performance: Fluorobenzene compounds can be adapted to various harsh battery operating scenarios such as high voltage, low temperature, and high areal capacity. They can also reduce the dissolution of transition metals in the positive electrode, enhance the stability of the positive electrode structure, and further improve the cycle life and reliability of the battery. 5) Greater economic efficiency and practicality: Compared to commonly used polyfluoroether diluents, fluorobenzene compounds are cheaper and have a relatively mature synthesis process. Taking fluorobenzene as an example, it has the advantages of low density and low cost as a co-solvent for electrolytes. In large-scale applications, it can reduce the production cost of lithium batteries and promote the actual application of high-performance lithium batteries.

[0032] In one alternative embodiment, the lithium salt is used to provide lithium ions, comprising at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0033] Specifically, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI or LiNTf2), with the chemical formula C2F6LiNO4S2 and CAS number 90076-65-6, exhibits good thermal stability, reducing the risk of electrolyte decomposition at high temperatures and improving battery safety and reliability under high-temperature conditions. It also demonstrates good hydrolysis resistance and electrochemical stability, enhancing the overall performance of the electrolyte and improving the battery's high-temperature tolerance and cycle stability. Lithium Bis(fluorosulfonyl)imide (LiFSI), a novel fluorosulfonylimide lithium salt with the chemical formula LiN(SO2F)2 and CAS number 171611-11-3, combines high ionic conductivity, excellent low-temperature performance, a wide voltage window, good chemical stability, and high rate adaptability, supporting the development of ultra-fast charging batteries. Lithium hexafluorophosphate (Lithium... Hexafluorophosphate (LiPF6) has the chemical formula LiPF6 and CAS number 21324-40-3. It possesses excellent ionic conductivity, wide voltage adaptability, and interfacial compatibility. Upon dissolution, it completely dissociates into free Li₂. + With PF6 -It can provide sufficient charge carriers for the electrolyte, form a stable electrolyte system with chlorinated ether solvents, adapt to the voltage requirements of mainstream cathode materials, and has the best overall conductivity; Lithium tetrafluoroborate (LiBF4) is a classic fluorine-containing inorganic lithium salt with the chemical formula LiBF4 and CAS number 7787-75-5. It can provide stable charge carriers for the electrolyte, has more balanced conductivity over a wide temperature range, and has excellent hydrolysis resistance and thermal stability. It can be used in medium and low voltage high-safety batteries, and has no side reactions of hydrofluoric acid corrosion. Even if the battery is short-circuited, there is no risk of fire or explosion; Lithium difluoro(oxalato) borate (LiDFOB) is a new type of fluorine-containing chelate lithium salt with the chemical formula C2LiBF2O4 and CAS number 409071-16-5. It has balanced conductivity over a wide temperature range and can balance stability and process adaptability. In summary, the lithium salt provided in this embodiment includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate. When there are two or more types of lithium salts, the proportions of the components in the various lithium salts can be adjusted adaptively according to the actual situation, and are not limited here.

[0034] In one alternative embodiment, the orthoformate compound includes at least one of trimethyl orthoformate, triethyl orthoformate, and tripropyl orthoformate.

[0035] Specifically, the chemical formula of trimethyl orthoformate (TMOF) is C4H. 10 O3, CAS number 149-73-5, has the molecular structure (CH3O)3CH. It is a trimethyl ether derivative of orthoformic acid. In the molecular structure of trimethyl orthoformate, the three methoxy groups (-OCH3) attached to the methylene carbon (-CH-) have a certain reducing property. During the first charge of the battery, it is reduced and decomposed on the surface of the negative electrode, and the generated lithium carbonate (Li2CO3) is the core inorganic component of the SEI layer. The generated lithium methoxide (LiOCH3) can help improve ionic conductivity. The SEI layer generated by trimethyl orthoformate is more dense and uniform, and the resistance to lithium ion migration is lower. The viscosity of trimethyl orthoformate (≈0.5 cP) is lower than that of commonly used low-viscosity main solvents, which can directly reduce the resistance to lithium ion migration, so that the electrolyte maintains a high ionic conductivity at low temperatures. This allows the battery to charge and discharge normally at low temperatures, and the capacity retention rate is higher. Triethyl orthoformate (TEOF), also known as triethoxymethane, has the molecular formula C7H. 16O3, with the structural formula HC(OC2H5)3 and CAS number 122-51-0, contains triethyl orthoformate. The steric hindrance of this molecule weakens the coordination between the solvent and lithium ions, thereby promoting the combination of lithium ions and electrolyte anions in the locally concentrated electrolyte system to form a stable structure. This allows for the formation of a lithium fluoride-rich SEI layer on the surface of the lithium metal anode. This SEI layer exhibits strong stability, hindering continuous side reactions between the electrolyte and the lithium anode and suppressing lithium dendrite growth. Tripropyl orthoformate (TPOF) has the molecular formula C0. 10 H 22 O3, CAS number 621-76-1, chemical structural formula HC(OC3H7)3, its core structure consists of a central carbon atom bonded to three alkoxy groups (—OC3H7, propoxy) and one hydrogen atom. It exhibits high chemical stability, is not easily hydrolyzed, and contains no unsaturated bonds or easily oxidized groups. Its redox resistance is superior to some traditional solvents. The polyether oxygen bonds (C—O—C) in its molecular structure can form weak coordination with metal ions (such as lithium ions), assisting ion transport. Tributyl orthoformate, also known as tributyloxymethane, has the molecular formula C0. 13 H 28 O3, CAS number 588-43-2, contains three butoxy groups in its tributyl orthoformate molecule, resulting in significant steric hindrance. This structural characteristic weakens the excessive coordination between the solvent and lithium ions, facilitating the formation of a suitable solvation structure in the electrolyte and promoting the formation of a stable SEI layer on the lithium metal anode surface. In summary, the orthoformate compounds provided in this embodiment include at least one of trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, and tributyl orthoformate. When there are two or more types of orthoformate compounds, the proportions of the components in the multiple orthoformate compounds can be adaptively adjusted according to actual conditions, and are not limited here.

[0036] In one alternative embodiment, the fluorobenzene compound includes at least one selected from fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, and 1,3,5-trifluorobenzene.

[0037] Specifically, fluorobenzene, abbreviated as FB, with CAS number 462-06-6, is the simplest aromatic fluoride with a molecular structure of C6H5F. It exhibits low viscosity, good chemical stability, and solvent compatibility. Using fluorobenzene as a diluent can reduce electrolyte viscosity, improve electrolyte ionic conductivity and rate performance, optimize low-temperature performance, broaden the battery's operating temperature range, stabilize the electrode interface, and suppress side reactions and lithium dendrite growth. Fluorobenzene has a mature synthesis process, readily available raw materials, and low industrial production costs, making it a preferred solution for balancing battery performance and cost. 1,2-Difluorobenzene, with the molecular formula C6H4F2 and CAS number 367-11-3, possesses low LUMO (Lowest Unoccupied Molecular Weight) properties. Orbital (lowest unoccupied molecular orbital) energy level, weak lithium-ion coordination, and high fluorine donation capacity allow for the formation of a lithium fluoride-rich SEI layer at a salt concentration of approximately 2M. This enables the maintenance of a localized lithium-ion solvation structure while reducing the overall salt concentration, achieving a localized high-concentration effect and reducing electrolyte costs. 1,2-Difluorobenzene can construct a robust SEI layer that effectively prevents the reaction between the solvent and the lithium metal anode, enhancing the interfacial stability between the electrolyte and the lithium metal anode and improving battery cycle performance. 1,2-Difluorobenzene has a low melting point, allowing it to... Introduced as a diluent into the electrolyte, 1,2-difluorobenzene can lower the electrolyte's freezing point, promote lithium-ion desolvation, and enable the battery to exhibit excellent low-temperature performance and fast-charging capability. The good diluting effect of 1,2-difluorobenzene can significantly reduce the viscosity of the electrolyte, which is beneficial for improving ionic conductivity and electrolyte wettability. 1,2-Difluorobenzene can also improve the flame retardant properties of the electrolyte and enhance its safety. 1,3-Difluorobenzene, also known as m-difluorobenzene, has the molecular formula C6H4F2 and CAS number 372-18-9. 1,3-Difluorobenzene has low viscosity (approximately 0.5 at 25°C).With a viscosity of 6 mPa·s, the addition of 1,3-difluorobenzene to the electrolyte significantly reduces the overall viscosity of the electrolyte system, decreases lithium-ion transport resistance, thereby improving the ionic conductivity of the electrolyte and enhancing the rate performance of the battery. The 1,3-difluorobenzene molecule has a stable structure and is not prone to decomposition or polymerization reactions within a wide temperature range of -40℃ to 60℃, thus broadening the battery's operating temperature range and meeting the needs of scenarios such as low-temperature start-up and high-temperature energy storage. 1,4-Difluorobenzene, also known as p-difluorobenzene, has the molecular formula C6H4F2 and CAS number 540-36-3. The fluorine atoms in this substance are highly electronegative. During battery cycling, they can undergo a reduction reaction on the surface of the lithium anode to form lithium fluoride. Lithium fluoride forms a thin, dense, and structurally stable SEI layer. This SEI layer not only prevents further side reactions between the electrolyte and the lithium anode but also effectively inhibits the disordered growth of lithium dendrites, preventing them from piercing the separator and causing a short circuit, thus ensuring battery safety during cycling. 1,2,3-Trifluorobenzene, also known as trifluorobenzene thiazolinone, has the molecular formula C6H3F3 and CAS number 1489-53- 8. The dehydrofluorination barrier of fluorinated aromatic hydrocarbons is higher than that of traditional fluorinated ethers. 1,2,3-Trifluorobenzene, as a substance of this class, can significantly alleviate the defluorination reaction and reduce the formation of acidic substances compared to polyfluoroether diluents when used in synergy with fluorobenzene. It can effectively inhibit the generation of hydrofluoric acid at high temperatures, preventing acidic substances from corroding the electrode interface and damaging the electrolyte system. Electrolytes containing this substance have better thermodynamic stability and will not deteriorate significantly even under high-temperature storage conditions, having no negative impact on the high-temperature storage performance of the battery; 1,2,4-trifluorobenzene... The molecular formula of fluorobenzene is C6H3F3, and its CAS number is 367-23-7. 1,2,4-Trifluorobenzene can be combined with relatively inert fluorobenzene to form a mixed diluent system. Fluorobenzene can reduce the viscosity and melting point of the electrolyte and widen the liquid range, while 1,2,4-trifluorobenzene optimizes interfacial stability. The synergistic effect of the two can improve the ionic conductivity and working performance of the battery in low-temperature environments such as -20℃. Relying on the high bond energy of the CF bond and the electron-withdrawing effect of fluorine atoms in the 1,2,4-trifluorobenzene molecule, it has good oxidation resistance and can be used with 4.A high-voltage lithium metal battery system with a high cutoff voltage of 5V avoids the oxidation and decomposition of the electrolyte under high-voltage conditions. 1,3,5-Trifluorobenzene, also known as symmetrical trifluorobenzene, has the molecular formula C6H3F3 and the CAS number 372-38-3. 1,3,5-Trifluorobenzene does not complex with lithium ions, has excellent compatibility, and can be well compatible with components such as lithium salts in the electrolyte without problems such as stratification or precipitation. At the same time, its related synthesis process is mature. As a diluent, it can not only reduce the overall cost of the electrolyte, but also ensure that the battery retains a relatively high capacity after hundreds of cycles, and has broad prospects for practical application. In summary, the fluorobenzene compounds provided in this embodiment include at least one of fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, and 1,3,5-trifluorobenzene. When there are two or more types of fluorobenzene compounds, the proportions of the components in the various fluorobenzene compounds can be adaptively adjusted according to actual conditions, and are not limited here.

[0038] In one alternative embodiment, the molar ratio of lithium salt to organic solvent ranges from (1:1) to (1:5), and the molar ratio of lithium salt to diluent ranges from (1:1) to (1:10).

[0039] Specifically, in the electrolyte provided in this embodiment, the molar ratio of lithium salt to organic solvent ranges from (1:1) to (1:5). Specifically, the molar ratio of lithium salt to organic solvent can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.4, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.7, 1:3.9, 1:4, 1:4.2, 1:4.5, 1:4.8, or 1:5. It can also be any range of values ​​conforming to the ratio of (1:1) to (1:5), such as (1:1) to (1:1.2), (1:1.2) to (1:3), (1:3) to (1:4), (1:2.5) to (1:5), (1:4) to (1:5), (1:3.7) to (1:4.5), or (1:4) to (1:4.5), etc. It should be noted that both excessively high and insufficient molar ratios of lithium salt and organic solvent are detrimental to the application of electrolyte in batteries and will affect battery performance. Specifically: If the molar ratio of lithium salt to organic solvent is too wide, the electrolyte viscosity will increase sharply, the lithium ion migration resistance will increase dramatically, and excessive lithium salt will easily cause side reactions on the electrode surface, leading to decreased electrolyte stability, easy precipitation of solids or corrosion. Excessive lithium salt will increase the cost of the electrolyte and increase the risk of internal short circuits in the battery. If the molar ratio of lithium salt to organic solvent is too narrow, the electrolyte ionic conductivity will decrease sharply, the battery will not be able to charge and discharge normally, and insufficient electrolyte filling in the electrode pores will lead to a significant decrease in the battery's initial coulombic efficiency and continuous capacity decay during cycling. The SEI layer will not form completely, the negative electrode interface will be unstable, and the risk of positive electrode dissolution will increase under high voltage. In this embodiment, the molar ratio of lithium salt to organic solvent is (1:1) to (1:5), which will not cause side reactions on the electrode surface, decreased electrolyte stability, or problems such as incomplete SEI layer formation and poor interface stability. The molar ratio range of lithium salt to organic solvent provided in this embodiment can be adjusted adaptively according to actual conditions and is not limited here.

[0040] Specifically, in the electrolyte provided in this embodiment, the molar ratio of lithium salt to diluent ranges from (1:1) to (1:10). Specifically, the molar ratio of lithium salt to diluent can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:10. It can also be any range of values ​​conforming to the ratio of (1:1) to (1:10), such as (1:1) to (1:3), (1:3) to (1:8), (1:3) to (1:4), (1:5) to (1:7), (1:6) to (1:10), (1:4) to (1:9), or (1:4) to (1:8.5), etc. It should be noted that both excessively high and insufficient molar ratios of lithium salt and diluent are detrimental to the application of electrolyte in batteries and will affect battery performance. Specifically: If the molar ratio of lithium salt to diluent is too wide, the electrolyte viscosity will be too high, lithium ion migration will be hindered, rate / low temperature performance will decrease, the generated SEI layer will be too thick, the interfacial impedance will increase, the electrolyte cost will increase, and the industrial economics will decrease. If the molar ratio of lithium salt to diluent is too narrow, lithium salt dissociation will be insufficient, the dielectric constant and ionic conductivity of the electrolyte will decrease, resulting in extremely slow battery charge and discharge speeds, or even failure to complete normal charge and discharge cycles, insufficient oxidation stability, failure of high-voltage positive electrode compatibility, incomplete SEI layer formation, poor negative electrode interface stability, imbalance between electrolyte and electrode wettability, reduced initial coulombic efficiency, and continuous capacity decay. In this embodiment, the molar ratio of lithium salt to diluent is (1:1) to (1:10), which will not cause problems such as an excessively thick SEI layer, increased interfacial impedance, increased electrolyte cost, and decreased industrial economics, nor will it cause problems such as incomplete SEI layer formation and poor interfacial stability. The molar ratio range of lithium salt to diluent provided in this embodiment can be adjusted adaptively according to actual conditions, and is not limited here.

[0041] The present invention will be further described below with reference to specific embodiments: Example 1 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 342 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:3.

[0042] Example 2 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 570 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:5.

[0043] Example 3 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 912 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is 1:8.

[0044] Example 4 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, tripropyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 228.3 mg of tripropyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 342 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:3.

[0045] Example 5 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, tripropyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 228.3 mg of tripropyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 570 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:5.

[0046] Example 6 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, tripropyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 228.3 mg of tripropyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 912 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:8.

[0047] Comparative Example 1 This comparative example provides an electrolyte, which belongs to the category of carbonated ester electrolytes and is existing technology. Specifically, it uses lithium bis(fluorosulfonyl)imide as the lithium salt and ethylene carbonate and methyl ethyl carbonate as organic solvents. The preparation method is as follows: 151.9 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 665 μL of methyl ethyl carbonate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, the ethylene carbonate is heated at 60°C until completely melted. 285 μL of ethylene carbonate is added to the mixed solution of lithium bis(fluorosulfonyl)imide and methyl ethyl carbonate. The mixture is stirred thoroughly until the solution is clear and transparent to obtain the electrolyte. The concentration of the lithium salt in the electrolyte is 1 mol / L, and the volume ratio of ethylene carbonate to methyl ethyl carbonate is 3:7.

[0048] The electrolytes in Examples 1 to 6 and Comparative Example 1 were respectively configured as lithium-copper half-cells. The lithium-copper half-cells include a lithium metal anode, an electrolyte, a copper current collector, and a polyethylene separator. The lithium metal anode, copper current collector, and polyethylene separator are all existing technologies in the field. The electrolytes are the electrolytes in Examples 1 to 6 and Comparative Example 1, respectively. The Aurbach performance of the above seven lithium-copper half-cells at room temperature was tested.

[0049] Reference Figure 1 As shown, Figure 1 These are Aurbach performance curves of the lithium copper half-cells in Embodiments 1, 2, 3, and Comparative Example 1 provided by this invention at 25°C. The horizontal axis represents cycle time, and the vertical axis represents voltage. The Aurbach method is an important technique in the field of lithium battery electrode material modification, proposed by Professor Doron Aurbach's team at Bar-Ilan University in Israel, and is common knowledge in this field. Figure 1 Four lithium copper half-cells were shown at 0.5 mA / cm². 2 Deposited at a current density of 5 mAh / cm 2 The deposition capacity is 0.5 mA / cm³. 2 Stripped to 1V at a current density of 0.5mA / cm 2 Deposited at a current density of 1 mAh / cm 2The deposition capacity is 0.5 mA / cm³. 2 Stripped down to 1V at a current density, and this process was repeated 10 times until finally stripped down to 1V.

[0050] Depend on Figure 1 It can be seen that the coulombic efficiency of the lithium copper half-cell in Example 1 is 99.64%, the coulombic efficiency of the lithium copper half-cell in Example 2 is 99.57%, the coulombic efficiency of the lithium copper half-cell in Example 3 is 99.74%, and the coulombic efficiency of the lithium copper half-cell in Comparative Example 1 is 67.73%. The coulombic efficiency of the lithium copper half-cells in Examples 1 to 3 all exceed 99.6%, which is significantly higher than that of Comparative Example 1, indicating that the electrolyte provided by the present invention has better compatibility with lithium metal anode.

[0051] Reference Figure 2 As shown, Figure 2 These are the long-cycle test curves of the lithium copper half-cells in Embodiment 1, Embodiment 2, Embodiment 3, and Comparative Example 1 provided by this invention at 25°C, where the horizontal axis represents the number of cycles and the vertical axis represents the coulombic efficiency. Figure 2 Four lithium copper half-cells were shown to operate at 0.5 mA / cm² at 25°C. 2 Deposited at a current density of 1 mAh / cm 2 The deposition capacity is 0.5 mA / cm². 2 Long cycle curves of stripping down to 1V at current density.

[0052] Depend on Figure 2 It can be seen that: in Comparative Example 1, the coulombic efficiency of the lithium copper half-cell in the first cycle was 95.61%, and then the coulombic efficiency began to decline significantly, reaching only 63.71% at the 50th cycle. In Example 1, the coulombic efficiency of the lithium copper half-cell in the first cycle was 97.20%, which then rapidly increased and tended to stabilize, with an average coulombic efficiency of 99.07% for the first 100 cycles. In Example 2, the coulombic efficiency of the lithium copper half-cell in the first cycle was 97.20%, and it was able to maintain a high coulombic efficiency for more than 100 cycles, with an average coulombic efficiency of 99.20%. Similarly, in Example 3, the coulombic efficiency of the lithium copper half-cell in the first cycle was 97.00%, and the average coulombic efficiency for the first 100 stable cycles was 99.10%, with no significant coulombic efficiency decline. This indicates that the electrolyte provided by the present invention can achieve extremely stable long-cycle performance in lithium copper half-cells, demonstrating excellent compatibility with lithium metal anodes.

[0053] Reference Figure 3 As shown, Figure 3 These are Aurbach performance curves of the lithium copper half-cells in Examples 4, 5, 6, and Comparative Example 1 provided by this invention at 25°C. Figure 3 Four lithium copper half-cells were shown at 0.5 mA / cm². 2Deposited at a current density of 5 mAh / cm 2 The deposition capacity is 0.5 mA / cm³. 2 Stripped to 1V at a current density of 0.5mA / cm 2 Deposited at a current density of 1 mAh / cm 2 The deposition capacity is 0.5 mA / cm³. 2 Stripped down to 1V at a current density, and this process was repeated 10 times until finally stripped down to 1V.

[0054] Depend on Figure 3 It can be seen that the coulombic efficiency of the lithium copper half-cell in Example 4 is 99.68%, the coulombic efficiency of the lithium copper half-cell in Example 5 is 99.57%, the coulombic efficiency of the lithium copper half-cell in Example 6 is 99.46%, and the coulombic efficiency of the lithium copper half-cell in Comparative Example 1 is 67.73%. The coulombic efficiency of the lithium copper half-cells in Examples 4 to 6 all exceed 99.6%, which is significantly higher than that of Comparative Example 1, indicating that the electrolyte provided by the present invention has better compatibility with lithium metal anode.

[0055] Reference Figure 4 As shown, Figure 4 These are the long-cycle test curves of the lithium copper half-cells in Embodiments 4, 5, 6, and Comparative Example 1 provided by this invention at 25°C, where the horizontal axis represents the number of cycles and the vertical axis represents the coulombic efficiency. Figure 4 Four lithium copper half-cells were shown to operate at 0.5 mA / cm² at 25°C. 2 Deposited at a current density of 1 mAh / cm 2 The deposition capacity is 0.5 mA / cm². 2 Long cycle curves of stripping down to 1V at current density.

[0056] Depend on Figure 4 It can be seen that: in Comparative Example 1, the coulombic efficiency of the lithium copper half-cell in the first cycle was 95.61%, and then the coulombic efficiency began to decline significantly, until it was only 63.71% at the 50th cycle. In Example 4, the coulombic efficiency of the lithium copper half-cell in the first cycle was 90.28%, and then it rose rapidly and tended to stabilize, with an average coulombic efficiency of 99.01% in the first 100 cycles. In Example 5, the coulombic efficiency of the lithium copper half-cell in the first cycle was 95.05%, and after 60 stable cycles, the lithium copper half-cell in Example 5 experienced significant failure. In Example 6, the coulombic efficiency of the lithium copper half-cell in the first cycle was 92.64%, but it also experienced a decline in coulombic efficiency after 60 cycles. This shows that the electrolyte provided by the present invention has excellent compatibility with lithium metal anodes.

[0057] Example 7 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 166.3 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 342 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1, and the molar ratio of lithium salt to diluent is approximately 1:3.

[0058] Example 8 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 498.9 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 342 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:3, and the molar ratio of lithium salt to diluent is approximately 1:3.

[0059] Example 9 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 831.5 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 342 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:5, and the molar ratio of lithium salt to diluent is approximately 1:3.

[0060] Example 10 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 114 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:1.

[0061] Example 11 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 627 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:5.5.

[0062] Example 12 This embodiment provides an electrolyte, which belongs to the orthoformate-based electrolyte, specifically as follows: lithium bis(fluorosulfonyl)imide is used as the lithium salt, triethyl orthoformate is used as the organic solvent, and 1,2-difluorobenzene is used as the diluent. The preparation method is as follows: 187 mg of lithium bis(fluorosulfonyl)imide is weighed and added to 199.56 mg of triethyl orthoformate. The mixture is stirred thoroughly to completely dissolve the lithium salt. Then, 1140 mg of 1,2-difluorobenzene is added and the mixture is stirred thoroughly to make the solution clear and transparent, thus obtaining the electrolyte. The molar ratio of lithium salt to organic solvent is approximately 1:1.2, and the molar ratio of lithium salt to diluent is approximately 1:10.

[0063] As can be seen from Examples 1, 7 to 12 and Comparative Example 1, the electrolyte provided by the present invention has superior compatibility with lithium metal anodes.

[0064] Compared with the prior art, the electrolyte provided in this embodiment achieves at least the following beneficial effects: The electrolyte provided in this embodiment includes lithium salt, organic solvent, and diluent. The organic solvent is an orthoformate compound, used to dissolve the lithium salt and regulate the solid-state electrolyte interface of the battery. The diluent is a fluorobenzene compound, used to regulate the viscosity and flowability of the electrolyte. The orthoformate compound can form a special lithium-ion-anion coordination structure in the electrolyte, inducing the formation of an inorganic-rich interface layer, improving the compatibility of the electrolyte with the lithium metal anode, and solving the problems of high viscosity, low conductivity, and poor wettability with the separator caused by high-concentration electrolytes. The electrolyte exhibits high lithium metal stability, enabling lithium-copper half-cells to achieve high coulombic efficiency. It also possesses excellent thermal stability and chemical compatibility, addressing the lithium dendrite problem faced by lithium metal anodes. This makes it suitable for the development and application of high-coulombic-efficiency lithium metal batteries. The electrolyte's preparation method is simple, and its application prospects are broad. Using fluorobenzene compounds as diluents, compared to commonly used polyfluoroether diluents, fluorobenzene compounds offer advantages such as readily available raw materials, lower cost, and more mature synthesis processes. This low-cost electrolyte is suitable for industrial production.

[0065] 2. Electrolyte preparation method Reference Figure 5 As shown, Figure 5 This is a flowchart of an electrolyte preparation method provided by the present invention. Another aspect of the present invention provides an electrolyte preparation method, comprising the following steps: S1: Add lithium salt to an organic solvent to obtain a lithium salt organic dispersion.

[0066] Specifically, refer to Figure 5 As shown, lithium salt is added to an organic solvent and stirred until the lithium salt is completely dissolved in the organic solvent. The two are then mixed uniformly to obtain a lithium salt organic dispersion. The organic solvent and lithium salt need to be mixed in a glove box under an inert atmosphere, such as argon or nitrogen. Since both lithium salt and organic solvent are highly sensitive to water, even trace amounts of water (e.g., greater than 20 ppm) can trigger multiple chain reactions, completely destroying the ionic conductivity of the electrolyte and producing harmful substances. Therefore, it is necessary to isolate water and oxygen using an inert atmosphere. The inert atmosphere will not react with the lithium salt and organic solvent, thus completely preventing external water and oxygen from entering. The reaction equipment, reaction time, reaction conditions, and other parameters used in step S1 are all existing technologies in the field and can be adjusted adaptively according to actual conditions. No specific limitations are made here.

[0067] S2: Add diluent to the lithium salt organic dispersion, stir, and let stand to obtain the electrolyte.

[0068] Specifically, continue to refer to Figure 5 As shown, after adding a diluent to the lithium salt organic dispersion, the mixture is stirred to ensure that the diluent is completely dissolved in the lithium salt organic dispersion. The two are then mixed uniformly and allowed to stand for a period of time to obtain the final electrolyte. In an optional embodiment, the stirring time is not less than 1 hour and the standing time is not less than 2 hours. If the stirring time is too short, the lithium salt organic dispersion and the diluent will not be sufficiently miscible. If the standing time is too short, the components of the final electrolyte will not be mixed evenly enough and will not be able to regulate the SEI layer. There is no upper limit set for the stirring time and the standing time, which can be adjusted according to the actual situation. In addition, the reaction equipment, reaction temperature and other parameters used in step S2 are all existing technologies in the field and can be adjusted according to the actual situation. No specific limitations are made here.

[0069] The electrolyte prepared by the above method includes lithium salt, organic solvent, and diluent. The organic solvent is an orthoformate compound, which is used to dissolve the lithium salt and regulate the solid-state electrolyte interface of the battery. The diluent is a fluorobenzene compound, which is used to regulate the viscosity and flowability of the electrolyte. Specific information about this electrolyte can be found above. This electrolyte preparation method is simple and has broad application prospects. Using fluorobenzene compounds as diluents has advantages over commonly used polyfluoroether diluents, such as readily available raw materials, lower cost, and more mature synthesis processes. This electrolyte is inexpensive and suitable for industrial production.

[0070] 3. Half-cell Another aspect of the present invention provides a half-cell comprising an electrolyte, the electrolyte being the electrolyte described above, the coulombic efficiency of the half-cell being not less than 99%, the electrolyte comprising a lithium salt, an organic solvent, and a diluent, wherein the organic solvent is an orthoformate compound, which is used to dissolve the lithium salt and regulate the solid electrolyte interface of the battery, and the diluent is a fluorobenzene compound, which is used to regulate the viscosity and flowability of the electrolyte. Formate compounds can form a unique lithium-ion-anion coordination structure in the electrolyte, inducing the formation of an inorganic-rich interface layer, improving the electrolyte's compatibility with the lithium metal anode, and solving problems such as high viscosity, low conductivity, and poor wettability with the separator caused by high-concentration electrolytes. This electrolyte exhibits high lithium metal stability, enabling high coulombic efficiency in lithium-copper half-cells. It also possesses excellent thermal stability and chemical compatibility, addressing the lithium dendrite problem faced by lithium metal anodes, making it suitable for the development and application of high-coulombic-efficiency lithium metal batteries. The preparation method of this electrolyte is simple, with broad application prospects. Using fluorobenzene compounds as diluents, compared to commonly used polyfluoroether diluents, fluorobenzene compounds have advantages such as readily available raw materials, lower cost, and more mature synthesis processes. This electrolyte is inexpensive and suitable for industrial production. Other information regarding this half-cell can be found in the descriptions of Examples 1 to 6 above, and will not be repeated here.

[0071] 4. Battery Reference Figure 6 As shown, Figure 6This is a partial structural schematic diagram of a battery provided by the present invention. Another aspect of the present invention provides a battery comprising an electrolyte, the electrolyte described above, comprising a lithium salt, an organic solvent, and a diluent. The organic solvent is an orthoformate ester compound, used to dissolve the lithium salt and regulate the solid-state electrolyte interface of the battery. The diluent is a fluorobenzene compound, used to regulate the viscosity and flowability of the electrolyte. The orthoformate ester compound can form a special lithium-ion-anion coordination structure in the electrolyte, inducing the formation of an inorganic-rich interface layer, improving the compatibility of the electrolyte with the lithium metal anode, and solving the problems of high viscosity and low conductivity caused by high-concentration electrolytes. Overcoming issues such as poor wettability with the separator, this electrolyte exhibits high lithium metal stability, enabling high coulombic efficiency in lithium-copper half-cells. It also demonstrates excellent thermal stability and chemical compatibility, resolving the lithium dendrite problem faced by lithium metal anodes. This makes it suitable for the development and application of high-coulombic-efficiency lithium metal batteries. The electrolyte preparation method is simple, with broad application prospects. Using fluorobenzene compounds as diluents offers advantages over commonly used polyfluoroether diluents, including readily available raw materials, lower cost, and more mature synthesis processes. This low-cost electrolyte is suitable for industrial production.

[0072] Continue to refer to Figure 6 As shown, the battery provided in this embodiment also includes a negative electrode current collector 1, a metal negative electrode 2, a separator 3, a positive electrode 4, and a positive electrode current collector 5. Along the assembly direction X of the battery, the negative electrode current collector 1, the metal negative electrode 2, the separator 3, the positive electrode 4, and the positive electrode current collector 5 are arranged in sequence. The negative electrode current collector 1 and the metal negative electrode 2 are in contact, the positive electrode 4 and the positive electrode current collector 5 are in contact, and the separator 3 is not in contact with the metal negative electrode 2 and the positive electrode 4. The electrolyte (not shown in the figure) wets the negative electrode current collector 1, the metal negative electrode 2, the positive electrode 4, the positive electrode current collector 5, and the separator 3, and the electrolyte fills the gaps between the negative electrode current collector 1, the metal negative electrode 2, the separator 3, the positive electrode 4, and the positive electrode current collector 5. The metal negative electrode 2 can be a lithium metal negative electrode, and the separator 3 can be a polyethylene film. The negative electrode current collector 1, the metal negative electrode 2, the separator 3, the positive electrode 4, and the positive electrode current collector 5 in this embodiment are all existing technologies in the art and can be adapted according to actual conditions. No specific limitations are made here. The battery provided in this embodiment has a large number of cycle times and can cycle stably.

[0073] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. An electrolyte, characterized in that, It includes lithium salt, organic solvent and diluent; wherein the organic solvent is an orthoformate compound, which is used to dissolve the lithium salt and regulate the solid electrolyte interface of the battery, and the diluent is a fluorobenzene compound, which is used to regulate the viscosity and flowability of the electrolyte.

2. The electrolyte according to claim 1, characterized in that, The lithium salt is used to provide lithium ions and includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

3. The electrolyte according to claim 1, characterized in that, The orthoformate compounds include at least one of trimethyl orthoformate, triethyl orthoformate, tripropyl orthoformate, and tributyl orthoformate.

4. The electrolyte according to claim 1, characterized in that, The fluorobenzene compounds include at least one of fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, and 1,3,5-trifluorobenzene.

5. The electrolyte according to claim 1, characterized in that, The molar ratio of the lithium salt to the organic solvent is in the range of (1:1) to (1:5), and the molar ratio of the lithium salt to the diluent is in the range of (1:1) to (1:10).

6. A method for preparing the electrolyte according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Add lithium salt to an organic solvent to obtain a lithium salt organic dispersion; S2: Add a diluent to the lithium salt organic dispersion, stir, and let stand to obtain an electrolyte.

7. The electrolyte preparation method according to claim 6, characterized in that, Step S1 includes mixing the organic solvent and the lithium salt in a glove box protected by an inert atmosphere.

8. The electrolyte preparation method according to claim 6, characterized in that, In step S2, the stirring time shall be no less than 1 hour and the standing time shall be no less than 2 hours.

9. A half-cell, characterized in that, Includes the electrolyte as described in any one of claims 1-5; the coulombic efficiency of the half-cell is not less than 99%.

10. A battery, characterized in that, It includes an electrolyte, a negative electrode current collector, a metal negative electrode, a separator, a positive electrode, and a positive electrode current collector, wherein the electrolyte is the electrolyte according to any one of claims 1-5; The electrolyte wets the negative electrode current collector, the metal negative electrode, the positive electrode, the positive electrode current collector, and the separator.

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