High-entropy electrolyte of lithium metal battery, preparation method and application
By using a high-entropy electrolyte formulation, the problems of lithium dendrites and interface instability in lithium metal batteries were solved, achieving high ion conduction and a stable interface, thereby improving the cycle life and charge/discharge efficiency of lithium metal batteries.
Patent Information
- Application Number
- CN202511519187.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-23
- Publication Date
- 2026-01-27
AI Technical Summary
In existing lithium metal batteries, side reactions between the electrodes and electrolytes lead to instability at the solid electrolyte interface, causing problems such as lithium dendrite formation, thermal runaway, short cycle life, and low charge-discharge efficiency. Commercial electrolytes are incompatible with lithium metal anodes, and it is difficult to balance the interactions between lithium ions, anions, and solvents to construct high ionic conductivity and anion-rich structures.
A high-entropy electrolyte formulation is used, which includes lithium fluoride and a specific ratio of lithium salt mixed with an organic solvent to form a uniform solvation structure, suppressing the lithium ion desolvation barrier and inducing uniform lithium deposition. The electrolyte is prepared by adding an equal molar concentration of lithium salt to an equal volume of organic solvent.
It achieves high ion conductivity and a stable solid electrolyte interface in lithium metal batteries, suppresses lithium dendrite growth, improves battery cycle stability and charge/discharge efficiency, and possesses rapid lithium-ion transport and long cycle performance.
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Figure CN121416618A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery technology, and in particular to a method for preparing a high-entropy electrolyte for lithium metal batteries and its application. Background Technology
[0002] The sustainable development of artificial intelligence and the revolution in the new energy industry have increased the demand for high-energy-density energy storage technologies. Lithium-metal batteries, with their ultra-high energy density exceeding 450 Wh / kg, are particularly noteworthy. −1 This has become a key design strategy for breaking through the energy density ceiling and reshaping the competitive landscape of the industry. However, side reactions between the electrodes and electrolytes lead to instability of the solid electrolyte interface film in lithium metal batteries. This causes the active lithium and electrolyte to be continuously depleted, inducing uneven deposition of lithium ions and the formation of lithium dendrites. This results in a series of problems such as thermal runaway, short cycle life, and low charge-discharge efficiency.
[0003] Electrolytes, acting as the "blood" for ion transport between electrodes, determine the electrode / electrolyte interface chemistry and significantly influence battery performance. Modulating the electrolyte is a direct and effective way to address these challenges. However, commercial electrolytes are incompatible with lithium metal anodes. While high ionic conductivity is achieved in commercial electrolytes with strong solvation structures, excessively strong lithium-ion-solvent interactions lead to high desolvation barriers and easily broken, organic-rich solid electrolyte interface phases. Weakly solvated electrolytes, high-concentration electrolytes, locally high-concentration electrolytes, electrolyte additives, and other novel systems have been designed to lower the lithium-ion desolvation barrier and form robust, inorganic-rich solid electrolyte interface phases. A key aspect of these designs is introducing more anions into the lithium-ion solvation structure. However, this enhanced lithium-ion-anion interaction results in lower ionic conductivity, thus reducing lithium-ion transport kinetics. Balancing the interactions among the three components (lithium ions, anions, and solvent) in the solvation structure and constructing a solvation structure with high ionic conductivity and anion-rich structure remains a major challenge. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-entropy electrolyte for lithium metal batteries, its preparation method, and its application.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: A high-entropy electrolyte for a lithium metal battery includes lithium fluoride and an organic solvent, said organic solvent including highly polar ethylene carbonate.
[0006] Preferably, it also includes lithium dioxaborate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxaborate, and lithium nitrate.
[0007] Preferably, the molar concentration ratio of lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium nitrate is 1:1:1:1:1:1:1, wherein the total molar concentration of lithium ions is 1 mol / L.
[0008] Preferably, the organic solvent further includes ethyl methyl carbonate and dimethyl carbonate.
[0009] Preferably, the volume ratio of methyl ethyl carbonate, dimethyl carbonate, and ethylene carbonate is 1:1:1.
[0010] A method for preparing a high-entropy electrolyte for lithium metal batteries includes the following steps: Step 1: Lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium nitrate are added sequentially to a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate to obtain a premixed solution. Step 2: Place the premixed solution under a magnetic stirrer and stir until the lithium salt is fully dissolved and the solution becomes relatively clear, thus obtaining a high-entropy electrolyte.
[0011] Preferably, the stirring process in step two involves placing the high-entropy electrolyte in a glove box and stirring for 12 hours.
[0012] Preferably, the lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxaborate, and lithium nitrate are added to an equal volume mixed solution of ethyl methyl carbonate, dimethyl carbonate, and ethylene carbonate at a total molar concentration of 1 mol / L.
[0013] Preferably, the volume ratio of methyl ethyl carbonate, dimethyl carbonate, and ethylene carbonate is 1:1:1.
[0014] Preferably, in step one, 0.0419 g of lithium dioxalatoborate, 0.0056 g of lithium fluoride, 0.0326 g of lithium hexafluorophosphate, 0.6158 g of lithium bis(trifluoromethanesulfonyl)imide, 0.0401 g of lithium bis(fluoromethanesulfonyl)imide, 0.0308 g of lithium dioxalatoborate and 0.0148 g of lithium nitrate are sequentially added to a mixed solution of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate with a total volume of 1.5 mL to obtain a premixed solution.
[0015] The application of the electrolyte described above or the electrolyte prepared by the above method in the production of lithium metal batteries.
[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a novel high-entropy electrolyte formulation, which can be prepared simply by mixing seven lithium salts at equimolar concentrations with equal volumes of three common commercial ester solvents. The resulting high-entropy electrolyte for lithium metal batteries has a total lithium-ion molar concentration of 1 mol / L, lower cost than high-salt-concentration electrolytes, and a simple and controllable preparation method, making it suitable for industrial applications.
[0017] Compared to lower entropy electrolyte systems, the aforementioned high entropy electrolyte for lithium metal batteries facilitates the entry of various lithium salt anions into the solvation sheath of lithium ions, inhibiting the coordination of large solvent molecules with lithium ions. This can effectively reduce the desolvation barrier of lithium ions.
[0018] This high-entropy electrolyte for lithium metal batteries induces more small anions to enter the solvation sheath of lithium ions and inhibits ion aggregation, forming a uniform solvation structure with smaller clusters. This effectively balances the advantages of strong / weak solvation structures, making the high-entropy electrolyte compatible with rapid ion conduction and anion-rich solvation structures.
[0019] The high-entropy electrolyte of this lithium metal battery can form a stable solid electrolyte interface on the surface of the lithium metal anode, ensuring that lithium ions can be rapidly transported between the bulk electrolyte and the interface, inducing uniform lithium deposition behavior.
[0020] Lithium metal battery electrolyte for Li||LiNi 0.5 Co 0.2 Mn 0.3 O2 full cell, including LiNi 0.5 Co 0.2 Mn 0.3 O2 has a high loading capacity (19.7 mg cm⁻¹). −2 3.0 mAh cm −2 This battery achieves a long cycle life of 200 cycles with a current density of 0.2 C and a voltage range of 2.8-4.3 V, and retains a capacity of more than 87.1%, demonstrating its potential for market application. Attached Figure Description
[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0022] Figure 1 This is a cycle count-specific capacity graph.
[0023] Figure 2 This is a graph showing the rate performance.
[0024] Figure 3 This is a time-voltage plot of current density.
[0025] Figure 4 This is a graph showing the average coulombic efficiency of lithium coating / stripping.
[0026] Figure 5 This is a scanning electron microscope image.
[0027] Figure 6 This shows the impedance diagram and the corresponding calculated ionic conductivity.
[0028] Figure 7 The electrolytes prepared using Example 1 and Comparative Example 1 were obtained using nuclear magnetic resonance (NMR) technology. 19 F nuclear magnetic resonance spectrum. Detailed Implementation
[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.
[0031] Example 1 In a glove box filled with high-purity argon, 0.0616 g of lithium bis(trifluoromethanesulfonyl)imide, 0.0401 g of lithium bis(fluoromethanesulfonyl)imide, 0.0326 g of lithium hexafluorophosphate, 0.0308 g of lithium difluorooxalate borate, 0.0148 g of lithium nitrate, 0.0419 g of lithium dioxalate borate, and 0.0056 g of lithium fluoride were sequentially added at a concentration of 0.143 mol / L to a 1.5 mL mixture of equal volumes of three ester solvents: ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The ethylene carbonate was highly polar. The mixture was then placed in the glove box and stirred on a magnetic stirrer (1000-1500 rpm) for 12 hours. The high polarity of the ethylene carbonate facilitated the dissolution of the lithium fluoride. After the lithium salts were fully dissolved, the solution became relatively clear, yielding a high-entropy electrolyte.
[0032] Comparative Example 1 The difference between Example 1 and Comparative Example 1 is that the solutes in the Comparative Example were 0.0616 g lithium bis(trifluoromethanesulfonyl)imide, 0.0401 g lithium bis(fluoromethanesulfonyl)imide, 0.0326 g lithium hexafluorophosphate, 0.0308 g lithium difluorooxalateborate, 0.0148 g lithium nitrate, and 0.0419 g lithium dioxalateborate, wherein the total molar concentration of lithium ions was also 1 mol / L, and all other conditions were the same as in Example 1.
[0033] Battery assembly: The positive electrode uses a high loading capacity of 3 mAh cm⁻¹ −2 LiNi 0.5 Co 0.2 Mn 0.3 O2 (Kelode), the negative electrode uses 400 μm thick pure lithium.
[0034] Full-cell (button type) assembly: Using CR2032 battery cases, assembly is performed inside a glove box to ensure a clean environment free from impurities. During assembly, the H2O and O2 content in the glove box must be below 0.1 ppm. Required battery components include: CR2032 battery case, 0.5 mm gasket, spring clip, well-stirred electrolyte, the aforementioned positive and negative electrode materials, and a PE separator (Φ16 mm). The battery assembly steps are as follows: First, use tweezers to pick up the CR2032 positive electrode case and place it in a clean area, then place the LiNi... 0.5 Co 0.2 Mn 0.3 The O2 (Φ10 mm) positive electrode material is placed in the center of the positive electrode shell, and 35 μL of electrolyte is added. Next, a thin film is laid on top, and another 35 μL of electrolyte is added, ensuring the film is smooth and flat. The lithium sheet (Φ14 mm), gasket (smooth side down), and spring contact (round hole down) are then placed in the center of the positive electrode shell using tweezers. Finally, the 2032 negative electrode shell is placed on top. The battery is gently pressed down with insulated tweezers to ensure it can be closed. The battery is then placed in a packaging machine to seal it. After removal, the battery assembly is complete.
[0035] Figure 1 Li||LiNi constructed using the electrolytes of Example 1 and Comparative Example 1 0.5 Co 0.2 Mn 0.3The cycle count-specific capacity plot of the O2 full cell was obtained during long-term cycling at room temperature using a current density of 0.2 C and a voltage range of 2.8–4.3 V. Excellent cycling stability was achieved in Example 1, with the full cell exhibiting 87.1% capacity retention and an ideal average coulombic efficiency of 99.7% after 200 cycles. In contrast, Comparative Example 1 showed significant capacity decay after 128 cycles. This is attributed to the fact that, compared to the lower entropy electrolyte of Comparative Example 1, the solvation structure of Example 1 became more diverse with the increase in the number of anion species, forming a more chaotic high-entropy chemical environment. Lithium ions in the solvation structure were more coordinated with anions, forming an anion-rich solvation structure, which reduced to form an inorganic-rich solid electrolyte interface phase. Furthermore, the anions occupied less space in long-chain solvents such as dimethyl carbonate and ethyl methyl carbonate, inducing smaller lithium-ion clusters, which facilitated faster lithium-ion transport.
[0036] Figure 2 To construct Li||LiNi using the electrolytes of Example 1 and Comparative Example 1 of this invention 0.5 Co 0.2 Mn 0.3 The rate performance of the O2 full cell was obtained during cycling at room temperature using a current density of 0.1 C–3 C and a voltage range of 2.8–4.3 V. As the current density increased, the full cell of Example 1 maintained a higher specific discharge capacity compared to Comparative Example 1, retaining approximately 149.1 mAh g⁻¹ at 1.0 C. −1 The specific capacity was high. Even at high current densities of 2.0 C and 3.0 C, the high capacity was still maintained. This further demonstrates that the electrolyte of Example 1, with its high entropy characteristics, induced smaller anions to enter the lithium-ion solvation sheath and form small lithium-ion clusters, establishing rapid lithium-ion transfer kinetics and giving it stronger fast-charging capability. In contrast, the lower entropy Comparative Example 1, due to its low anion content solvation structure resulting in large lithium-ion clusters, could not significantly improve the battery's rate performance, and its specific capacity decreased significantly with increasing current.
[0037] Figure 3 The Li||Li symmetric cells constructed using the electrolytes prepared in Example 1 and Comparative Example 1 were used at 1 mA cm⁻¹ −2The time-voltage plot of current density shows that the symmetric cell using Comparative Example 1 exhibits significant polarization after 230 hours, indicating uncontrollable dendrite growth and severe side reactions, leading to a sharp increase in cell resistance. Conversely, the symmetric cell constructed using Example 1 demonstrates a longer cycle life (300 hours) and less polarization. At 255 hours, the polarization voltage of Example 1 is 63.5 mV, significantly lower than that of Comparative Example 1 (88.9 mV). This demonstrates that in the higher entropy electrolyte of Example 1, multiple anions participate in solvation behavior and form smaller clusters, exhibiting both rapid ion conduction and a low desolvation barrier, resulting in more reversible lithium deposition / stripping behavior. In contrast, the lower entropy electrolyte of Comparative Example 1 has a lower proportion of solvated structural anions, a high desolvation barrier for lithium ions, and cannot transport them rapidly, leading to large polarization at the interface and preventing uniform lithium deposition.
[0038] Figure 4 The Li||Cu batteries constructed using the electrolytes prepared in Example 1 and Comparative Example 1 were tested using the Auerbach method to measure the average coulombic efficiency of the lithium plating / stripping over 20 cycles. This was achieved at a current density of 0.5 mA cm⁻¹. −2 and equivalent capacity of 1mAh cm −2 After 20 cycles under the specified conditions, the average coulombic efficiency of Example 1 reached 99.1%, while that of Comparative Example 1 was lower. This indicates that the solvation structure with a high anion content in Example 1, which has a higher entropy, lowers the desolvation barrier of lithium ions and accelerates lithium ion kinetics. On the other hand, the reduction of anions constructs an inorganic-rich solid electrolyte interface, which has faster ion conduction and is more robust, making it difficult for lithium metal to contact the electrolyte and causing irreversible side reactions, thus facilitating more reversible lithium deposition / stripping behavior. In contrast, in the lower entropy Comparative Example 1, the anion-poor solvation structure forms a high desolvation barrier, and the interface phase is dominated by organic matter. This restricts lithium ion transport and leads to a fragile solid electrolyte interface, which cannot suppress lithium dendrite growth, and the side reactions between the lithium anode and the electrolyte continue to occur, resulting in low coulombic efficiency.
[0039] Figure 5The lithium metal anode images are obtained after three short-cycle tests at room temperature using the electrolytes prepared in Example 1 and Comparative Example 1, with a current density of 0.2 C and a voltage range of 2.8–4.3 V. Images a and b show the lithium metal anodes using the electrolytes of Example 1 and Comparative Example 1, respectively. After short-cycle testing with the half-cell of Comparative Example 1, a loose lithium deposition surface was observed, with obvious pores and dendrites. This indicates that Comparative Example 1 resulted in severe interfacial side reactions, with the lithium metal being severely corroded by the electrolyte and forming a thick, non-uniform solid electrolyte interface. In contrast, dense and uniform lithium deposition behavior was observed in Example 1. This suggests that a high-entropy electrolyte can promote faster desolvation and construct a robust solid electrolyte interface while reducing interfacial resistance, further limiting lithium dendrite growth.
[0040] Figure 6 To test the stainless steel symmetric cells constructed using the electrolytes prepared in Example 1 and Comparative Example 1, a 10-year standard was applied at room temperature. −1 Hz to 10 6 Impedance plots and corresponding calculated ionic conductivities were obtained from tests conducted over a frequency range of Hz and a voltage amplitude of 10 mV. In the figures, a and b represent the impedance and corresponding ionic conductivities of the electrolytes used in Example 1 and Comparative Example 1, respectively. It can be observed that the impedance of Example 1 is significantly lower than that of Comparative Example 1, indicating that the lithium-ion transport capacity is enhanced in Example 1, resulting in higher ionic conductivities. This is attributed to the fact that in the high-entropy Example 1, smaller anions participate more in the lithium-ion solvation structure, further reducing cluster size and establishing rapid ion transfer kinetics. In contrast, in the lower-entropy Comparative Example 1, larger solvent molecules dominate the lithium-ion solvation structure, forming larger lithium-ion clusters. The increased spatial position hinders the rapid conduction of lithium ions, leading to lower ionic conductivities.
[0041] Figure 7 The electrolytes prepared using Example 1 and Comparative Example 1 were obtained using nuclear magnetic resonance (NMR) technology. 19 F-NMR spectrum. It can be observed that, compared to the lower entropy Comparative Example 1, the higher entropy of Example 1... 19The low-field shift in the F-NMR spectrum indicates a reduced electron cloud density on the surface of the fluorine-containing anion, resulting in a stronger coordination ability with lithium ions. This allows more anions to enter the solvation structure of lithium ions, reducing cluster size and lowering the desolvation barrier. These anions also preferentially reduce at the interface, forming an inorganic-rich solid electrolyte interface to suppress lithium dendrite growth and interfacial side reactions. In contrast, the lower-entropy comparative example 1 exhibits a weaker coordination ability between anions and lithium ions. Larger solvent molecules participate more in the lithium-ion solvation sheath, forming larger lithium-ion clusters and a stronger solvation structure, leading to lower ionic conductivity and a higher desolvation barrier. Furthermore, the organic-rich interfacial phase resulting from solvent reduction is incompatible with the lithium anode, leading to irreversible lithium dendrite growth and increased polarization.
[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.
Claims
1. A high-entropy electrolyte for lithium metal batteries, characterized in that, It includes lithium fluoride and an organic solvent, said organic solvent including highly polar ethylene carbonate.
2. The high-entropy electrolyte for lithium metal batteries according to claim 1, characterized in that, It also includes lithium dioxaborate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxaborate, and lithium nitrate.
3. The high-entropy electrolyte for lithium metal batteries according to claim 2, characterized in that, The molar concentration ratio of lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium nitrate is 1:1:1:1:1:1:1, wherein the total molar concentration of lithium ions is 1 mol / L. The organic solvents also include ethyl methyl carbonate and dimethyl carbonate.
4. The lithium metal battery electrolyte according to claim 3, characterized in that, The volume ratio of methyl ethyl carbonate, dimethyl carbonate, and ethylene carbonate is 1:1:
1.
5. A method for preparing a high-entropy electrolyte for lithium metal batteries, characterized in that, Includes the following steps: Step 1: Lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium nitrate are added sequentially to a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate to obtain a premixed solution. Step 2: Mechanically stir the premixed solution in a glove box for 12 hours until the lithium salt is fully dissolved, forming a clear solvent, and obtain a high-entropy electrolyte.
6. The method for preparing the high-entropy electrolyte for lithium metal batteries according to claim 5, characterized in that, The stirring process in step two involves placing the high-entropy electrolyte in a glove box and stirring for 12 hours.
7. The method for preparing the lithium metal battery electrolyte according to claim 6, characterized in that, The lithium dioxaborate, lithium fluoride, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium nitrate were added to an equal volume mixed solution of ethyl methyl carbonate, dimethyl carbonate, and ethylene carbonate at a total molar concentration of 1 mol / L.
8. The method for preparing the lithium metal battery electrolyte according to claim 6, characterized in that, The volume ratio of methyl ethyl carbonate, dimethyl carbonate, and ethylene carbonate is 1:1:
1.
9. The method for preparing the lithium metal battery electrolyte according to claim 6, characterized in that, The first step involves sequentially adding 0.0419 g of lithium dioxalatoborate, 0.0056 g of lithium fluoride, 0.0326 g of lithium hexafluorophosphate, 0.6158 g of lithium bis(trifluoromethanesulfonyl)imide, 0.0401 g of lithium bis(fluoromethanesulfonyl)imide, 0.0308 g of lithium dioxalatoborate, and 0.0148 g of lithium nitrate to a mixed solution of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate with a total volume of 1.5 mL, to obtain a premixed solution.
10. The application of the electrolyte according to any one of claims 1 to 4 or the electrolyte prepared by any one of claims 5 to 9 in the production of lithium metal batteries.