An electrolyte and a lithium metal battery comprising the same
Patent Information
- Application Number
- CN202611006051.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-07
- Publication Date
- 2026-09-15
Smart Images
Figure CN122762829A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium metal secondary battery technology, specifically to an electrolyte and a lithium metal battery including the electrolyte. Background Technology
[0002] In recent years, lithium-ion batteries have become the mainstream energy storage device in portable electronic devices, large-scale energy storage systems, and new energy vehicles due to their advantages such as high operating voltage, long cycle life, and environmental friendliness. With the rapid iteration of the global new energy industry, the market demand for battery energy density continues to rise. Traditional lithium-ion batteries (with energy densities mostly between 200-300Wh / kg) can no longer meet the performance requirements of next-generation energy storage devices, making high-energy-density lithium metal batteries (LMBs) a key direction for industry breakthroughs.
[0003] Lithium metal anodes possess ultra-low redox potentials and ultra-high theoretical specific capacity, making them a key breakthrough for improving battery energy density. When lithium metal anodes are matched with high-voltage cathode materials (such as high-nickel ternary materials like NCM811), battery energy density can achieve a leapfrog improvement, with the cathode specific capacity stably exceeding 200mAh / g and the charging cut-off voltage increasing to over 4.3V. This demonstrates enormous industrialization potential in fields such as long-range new energy vehicles and large-capacity energy storage power stations.
[0004] However, the practical application of high-voltage lithium metal batteries is limited by multiple common technical bottlenecks. Especially under extreme conditions such as voltages above 4.5V and high temperatures, the cycle stability and safety of the batteries deteriorate sharply, severely hindering their industrialization. The core problems are concentrated in the following aspects: First, the high-nickel cathode structure is prone to failure. During high-voltage charging, the cathode material is prone to transition metal dissolution, lattice oxygen loss, and particle cracking, leading to a continuous reduction in active sites and rapid capacity decay. Second, traditional commercial carbonate electrolytes have insufficient oxidative stability, especially at 4.3V... Under the above voltages, oxidation and decomposition will occur, producing gases and organic byproducts, which will damage the integrity of the cathode electrolyte interface (CEI) and exacerbate the interfacial reaction between the electrode and the electrolyte. Third, the lithium metal anode deposition behavior will be out of control. Under high voltage conditions, the electrolyte decomposition products will interfere with the lithium deposition kinetics, causing lithium to grow unevenly in the form of dendrites. This not only consumes active lithium and electrolyte, but may also puncture the separator and cause internal short circuits, bringing serious safety hazards. Fourth, the control of the double layer structure at the electrode interface is lacking. The inner Helmholtz layer (IHP) is the core region of the double layer, and its composition and structure directly determine the formation quality of the CEI layer. However, under the current technology, the IHP composition is disordered, which further aggravates electrolyte decomposition and interfacial impedance growth, forming a vicious cycle.
[0005] To address these issues, the industry has conducted extensive research on electrolyte optimization. Existing technical solutions mainly fall into three categories: First, increasing the lithium salt concentration to improve electrolyte oxidation stability by constructing contact ion pairs. However, this significantly increases electrolyte viscosity, reduces ion conduction efficiency, and the increased lithium salt usage leads to soaring costs, making it difficult to meet the demands of industrial-scale production. Second, using a weakly solvated solvent system to reduce the probability of solvent molecule oxidation and decomposition. However, this type of system has poor compatibility with high-nickel cathodes and easily exacerbates transition metal dissolution, thus worsening cycle stability. Third, adding single-function additives. This approach can only address a specific problem and cannot simultaneously meet multiple requirements such as dual-interface stability, transition metal dissolution inhibition, and tolerance to extreme operating conditions, resulting in limited practical application effectiveness.
[0006] Therefore, how to precisely control the double-layer structure of the high-voltage cathode surface through a simple, feasible, and cost-controllable electrolyte modulation strategy, especially optimizing the composition and distribution of IHP, to fundamentally solve a series of problems such as electrolyte decomposition, transition metal dissolution, and lithium dendrite growth, while ensuring the stable operation of the battery under extreme conditions such as high temperature, has become a common industry problem that urgently needs to be solved in the practical application of high-energy-density lithium metal batteries.
[0007] This application addresses this core need by providing an efficient and reliable solution. Summary of the Invention
[0008] The purpose of this application is to provide an electrolyte and a lithium metal battery including the electrolyte to solve the above-mentioned problems.
[0009] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: This application provides an electrolyte comprising a lithium salt, an organic solvent, a first additive, and a second additive. The first additive is a compound with electric field responsiveness, which preferentially accumulates at the positive electrode interface during charging. The second additive is an electronically defective compound with Lewis acid characteristics, which preferentially interacts with anions in the electrolyte. Through the synergistic effect of the first and second additives, the proportion of solvent molecules in the Helmholtz layer at the positive electrode interface is reduced, thereby improving the oxidative stability of the electrolyte under high voltage conditions.
[0010] Preferably, the first additive is an anionic compound that can form a strong coordination interaction with lithium ions and has a small ion size.
[0011] More preferably, the first additive is selected from any one or more of lithium chloride, lithium bromide, lithium nitrate, lithium tetrafluoroborate, lithium perchlorate, lithium borate, and lithium phosphate.
[0012] Preferably, the second additive is any one or more of Lewis acid compounds, boron-based compounds, carbonyl-containing strong electron-withdrawing compounds, cyano-containing compounds, and fluorine-containing organic compounds.
[0013] More preferably, the second additive is an electronically defective compound containing aryl substituents.
[0014] Optionally, the electrolyte also satisfies one or more of the following conditions: a. The first additive accounts for 0.01–10% of the total mass of the lithium salt and the organic solvent; b. The second additive comprises 0.01–5% of the total mass of the lithium salt and the organic solvent; c. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorophosphate; d. The organic solvent is selected from at least one of chain carbonate solvents and cyclic carbonate solvents.
[0015] This application also provides a lithium metal battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.
[0016] Preferably, the cathode is a high-nickel layered oxide cathode material.
[0017] More preferably, the cathode material is LiNi. x Co y Mn z O2, where x+y+z=1, 0.5≤x≤0.9.
[0018] Compared with the prior art, this application has the following beneficial effects: The electrolyte provided in this application contains dual additives. By regulating the Helmholtz layer structure within the positive electrode interface, it enhances high-voltage stability. Specifically, the synergistic additive electrolyte system of this application introduces anionic additives with electric field response characteristics and electronically defective compounds with Lewis acid characteristics. During charging, a solvent-depleted and ion-enriched Helmholtz layer structure is constructed within the positive electrode interface, thereby inhibiting the oxidative decomposition of the solvent at the positive electrode interface and improving the stability of the electrolyte under high-voltage conditions. The electrolyte provided in this application remains stable under a charging cutoff voltage of 4.5–5.0 V, and lithium metal batteries containing it exhibit stable cycling performance at 25–70°C. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 The graph shows the results of charge-discharge cycle tests of lithium metal batteries at room temperature provided in Example 4 and Comparative Example 1. Figure 2 The graph shows the results of the high-temperature charge-discharge cycle test of the lithium metal battery provided in Example 4 and Comparative Example 1; Detailed Implementation To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0021] The following description is based on specific embodiments. It should be noted that the electrolyte provided in this application is prepared by: firstly, dissolving lithium salt in an organic solvent under an inert atmosphere in an argon glove box, so that the lithium salt concentration is 0.5-3 mol·L⁻¹. - ¹, to obtain the basic electrolyte. Subsequently, a first additive is added to the basic electrolyte at an amount of 0.01-10 wt% of the total mass of the basic electrolyte; then a second additive is added at an amount of 0.01-5 wt% of the total mass of the basic electrolyte. The resulting system is stirred continuously at 25-50°C for 8-16 hours until a homogeneous, transparent electrolyte without precipitation is formed.
[0022] Example 1 This embodiment provides an electrolyte system suitable for high-voltage lithium metal batteries. The electrolyte includes lithium hexafluorophosphate, a mixed solvent of chain carbonates and cyclic carbonates, as well as perchlorate and triarylboroxyalkane.
[0023] The preparation steps of this electrolyte are as follows: First, lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate and diethyl cyclic carbonate under an inert atmosphere in an argon glove box, so that the concentration of lithium hexafluorophosphate salt was 1 mol·L⁻¹. - ¹, thus obtaining the basic electrolyte.
[0024] Subsequently, lithium perchlorate was added to the above-mentioned basic electrolyte at a rate of 1 wt% of the total mass of the basic electrolyte; then, a second additive, triarylboroxane, was added at a rate of 0.75 wt% of the total mass of the basic electrolyte.
[0025] Finally, the resulting system was stirred continuously at 25°C for 16 hours until a homogeneous, transparent electrolyte without precipitation was formed.
[0026] Example 2 This embodiment provides an electrolyte system suitable for high-voltage lithium metal batteries. The electrolyte includes lithium bis(fluorosulfonyl)imide, chain carbonate solvents, perchlorate, and triarylboroxyalkane.
[0027] The preparation steps of this electrolyte are as follows: First, lithium bis(fluorosulfonyl)imide was dissolved in a mixed solvent of ethylene carbonate and diethyl cyclic carbonate under an inert atmosphere in an argon glove box, so that the concentration of lithium bis(fluorosulfonyl)imide salt was 1.5 mol·L⁻¹. - ¹, thus obtaining the basic electrolyte.
[0028] Subsequently, lithium perchlorate was added to the above-mentioned basic electrolyte at a rate of 5 wt% of the total mass of the basic electrolyte; then, a second additive, triarylboroxane, was added at a rate of 3 wt% of the total mass of the basic electrolyte.
[0029] Finally, the resulting system was stirred continuously at 40°C for 12 hours until a homogeneous, transparent electrolyte without precipitation was formed.
[0030] Example 3 This embodiment provides an electrolyte system suitable for high-voltage lithium metal batteries. The electrolyte includes lithium difluorophosphate, cyclic carbonate solvents, phosphates, and triarylboroxyalkane.
[0031] The preparation steps of this electrolyte are as follows: First, lithium difluorophosphate was dissolved in a mixed solvent of ethylene carbonate and cyclic diethyl carbonate under an inert atmosphere in an argon glove box, so that the concentration of lithium difluorophosphate salt was 3 mol·L⁻¹. - ¹, thus obtaining the basic electrolyte.
[0032] Subsequently, lithium phosphate was added to the above-mentioned basic electrolyte at a rate of 10 wt% of the total mass of the basic electrolyte; then, a second additive, triarylboroxane, was added at a rate of 5 wt% of the total mass of the basic electrolyte.
[0033] Finally, the resulting system was stirred continuously at 50°C for 8 hours until a homogeneous, transparent electrolyte without precipitation was formed.
[0034] Example 4 This embodiment provides a method using LiNi x Co y Mn zO2 is used as the positive electrode active material, where x is 0.8, y is 0.1, and z is 0.1. It is coated with conductive agent Super P and binder PVDF onto an aluminum foil current collector and dried to obtain a positive electrode sheet. Lithium metal is used as the negative electrode, and the electrolyte prepared in Example 1 is injected to construct a lithium metal button cell.
[0035] Comparative Example 1 The difference from Example 4 is that the electrolyte in this comparative example is the basic electrolyte prepared in Example 1, which is used to construct a lithium metal button cell.
[0036] The batteries provided in Example 4 and Comparative Example 1 were subjected to charge-discharge cycle tests at room temperature. The test results are as follows: Figure 1 As shown. Figure 1 The graph shows the charge-discharge cycle test results of the lithium metal batteries provided in Example 4 and Comparative Example 1 at room temperature. Figure 1 In this context, "Dual" represents the battery provided in Example 4, and "Blank" represents the battery provided in Comparative Example 1. Figure 1 It can be seen that the lower limit of the cutoff voltage is 2.8V and the upper limit is 4.5-4.9V. The battery provided in Example 4 showed good cycle stability at room temperature.
[0037] The batteries provided in Example 4 and Comparative Example 1 were subjected to cycle testing in an environment of 25-70°C. The results are as follows: Figure 2 As shown, Figure 2 The graph shows the high-temperature charge-discharge cycle test results of the lithium metal batteries provided in Example 4 and Comparative Example 1. Figure 2 In this context, Dual represents the battery provided in Example 4, and Blank represents the battery provided in Comparative Example 1. Figure 2 This indicates that the battery provided in Example 4 still maintains a high capacity retention rate under high temperature and high voltage conditions.
[0038] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. An electrolyte, characterized by, The electrolyte comprises lithium salt, organic solvent, first additive, and second additive; wherein the first additive is a compound with electric field responsive characteristics; and the second additive is an electronically defective compound with Lewis acid characteristics.
2. The electrolyte according to claim 1, characterized in that, The first additive is an anionic compound that can form a strong coordination interaction with lithium ions and has a small ion size.
3. The electrolyte according to claim 2, characterized in that, The first additive is selected from any one or more of lithium chloride, lithium bromide, lithium nitrate, lithium tetrafluoroborate, lithium perchlorate, lithium borate, and lithium phosphate.
4. The electrolyte of claim 1, wherein The second additive is any one or more of Lewis acid compounds, boron-based compounds, carbonyl-containing strong electron-withdrawing compounds, cyano-containing compounds, and fluorine-containing organic compounds.
5. The electrolyte according to claim 4, characterized in that, The second additive is an electronically defective compound containing aryl substituents.
6. The electrolyte according to any one of claims 1-5, characterized in that, The electrolyte also satisfies one or more of the following conditions: a. The first additive accounts for 0.01–10% of the total mass of the lithium salt and the organic solvent; b. The second additive comprises 0.01–5% of the total mass of the lithium salt and the organic solvent; c. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorophosphate; d. The organic solvent is selected from at least one of chain carbonate solvents and cyclic carbonate solvents.
7. A lithium metal battery, characterized in that, The lithium metal battery includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1-6.
8. The lithium metal battery according to claim 7, characterized in that, The cathode is a high-nickel layered oxide cathode material.
9. The lithium metal battery according to claim 8, characterized in that, The positive electrode material is LiNi x Co y Mn z O2, wherein x+y+z = 1, 0.5≤x≤0.9.