An electrolyte based on gradient polarity component blending, its design method and application

Abstract

This invention provides an electrolyte based on a gradient polarity component blend, its design method, and its application. This design method achieves precise control over the microscopic solvation structure of the electrolyte by constructing a blend system composed of low-polarity, medium-polarity, and high-polarity solvents. First, the system components are screened based on the functional differences in solvation ability, low-temperature stability, and flame retardant properties of different polarity components. Second, the proportions of each component are systematically optimized to construct an optimal polarity gradient distribution. Finally, the ion migration behavior, structural characteristics, and thermal stability of the system are verified at multiple scales, thereby achieving a synergistic improvement in high ion mobility, excellent flame retardant properties, and wide-temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of batteries, specifically relating to an electrolyte based on gradient polarity component compounding, its design method, and its application. Background Technology

[0002] Electrolyte systems are a core component of power batteries, consisting of complex ionic soft matter systems composed of ions, polar solvents, and functional additives. In fields such as new energy vehicles and electrochemical energy storage, electrolytes not only perform ion transport but also directly determine key battery performance indicators such as safety, rate capability, and operating temperature range. Therefore, developing electrolyte systems that combine high ion mobility, excellent flame retardancy, and good low-temperature performance has become an important research direction in the current power battery field.

[0003] From a microscopic perspective, the structure and performance of electrolyte systems are primarily determined by various intermolecular interactions, especially the electrostatic interactions between components, including complex electrostatic interactions between anions, cations, and polar molecules. These interactions couple at different scales, collectively influencing the dispersion state, migration behavior, and macroscopic rheological properties of ions within the system. For example, the polarity of the solvent (usually characterized by dielectric constant or dipole moment) directly affects the solvation ability of ions, thereby altering their aggregation state and migration rate. Simultaneously, interactions between polar molecules also influence the system's viscosity and low-temperature phase behavior (such as crystallization or glass transition).

[0004] In electrolyte design, ion mobility, flame retardancy, and low-temperature stability are generally interdependent; that is, improving one property often comes at the expense of others. Furthermore, with a deeper understanding of electrolyte systems, research shows that the influence of solvent polarity on ion migration behavior is not a simple monotonic relationship, but rather is affected by ion-dipole and dipole-dipole interaction competition mechanisms, exhibiting a complex, non-monotonic variation. This further increases the difficulty of electrolyte design, making traditional design methods based on single-parameter control insufficient to meet the requirements of multi-performance synergistic optimization.

[0005] Currently, existing electrolyte design schemes have the following problems:

[0006] (1) It is difficult to synergistically improve the electrolyte's ion mobility, wide temperature range stability, and flame retardancy. In traditional electrolyte development, high ion mobility, high flame retardancy, and wide temperature range performance (low-temperature crystallization resistance) are mutually restrictive. Specifically, high polarity solvents can ensure sufficient solvation of ions, but they will lead to increased system viscosity. At the same time, high polarity components generally pose safety hazards such as flammability and easy crystallization at low temperatures. While introducing low polarity or flame retardant components can improve safety and low-temperature performance, it will weaken ion transport capacity, making it difficult to achieve unified optimization of multiple properties. The introduction of low polarity diluents or flame retardant additives usually relies on experience for ratio optimization, lacking a systematic understanding of the complex interactions between components, making it difficult to accurately control the ion distribution and dynamic behavior in the system. The above-mentioned technical routes are still generally at the stage of "single performance optimization or empirical compromise", and have not yet formed a systematic design method based on microscopic interaction mechanisms, making it difficult to fundamentally solve the problem of synergistic optimization of multiple properties.

[0007] (2) Traditional electrolyte theory is usually based on the mean field. This theoretical framework usually changes monotonically as the solvent dielectric constant increases, ion aggregation weakens, or kinetics accelerate. Therefore, in order to ensure that the ions are fully solvated, existing technologies often add highly polar solvents (such as ethylene carbonate, abbreviated as EC). However, this will lead to an increase in the viscosity of the system and cause low-temperature crystallization, inhibiting ion migration. During fast charging, lithium plating is easily triggered, increasing the risk of thermal runaway. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide an electrolyte based on a gradient polarity component blend, its design method, and its application. This design method achieves precise control of the electrolyte's microscopic solvation structure by constructing a blend system composed of low-polarity, medium-polarity, and high-polarity solvents. First, the system components are screened based on the functional differences in solvation ability, low-temperature stability, and flame retardant properties of different polarity components. Second, the proportions of each component are systematically optimized to construct an optimal polarity gradient distribution. Finally, the ion migration behavior, structural characteristics, and thermal stability of the system are verified at multiple scales, thereby achieving a synergistic improvement in high ion mobility, excellent flame retardant properties, and wide-temperature stability.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for designing an electrolyte based on a gradient polarity component complex, comprising the following steps:

[0011] S1: Component screening: Screening solvent components of different polarities to obtain low-polarity solvents, medium-polarity solvents and high-polarity solvents;

[0012] S2: Define the mixing ratio ranges of low-polarity, medium-polarity, and high-polarity solvents, construct combination systems with different ratios, and use a low-scaling algorithm to establish a simplified physical model between the solvent molecule polarity parameters and ion mobility in the combination systems with different ratios. Obtain the kinetic performance of the combination systems with different ratios, thereby initially screening the combination systems with different ratios. Then, use high-throughput simulation to calculate the ion solvation structure, migration behavior, and viscosity change law of the combination systems with different ratios obtained after the initial screening, and obtain the optimal polarity gradient window where the ion mobility reaches the peak while simultaneously meeting the requirements of flame retardant performance and wide temperature range stability. Determine the optimal ratio of low-polarity, medium-polarity, and high-polarity solvents based on the optimal polarity gradient window.

[0013] Preferably, the screening refers to: screening solvents based on the functional differences in solvation ability, low-temperature stability and flame retardant properties of solvents with different polarities to obtain low-polarity solvents, medium-polarity solvents and high-polarity solvents.

[0014] Preferably, the low-polarity solvent is selected from one or more of hydrofluoroether-7100, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, or fluoroethylene carbonate; the medium-polarity solvent is selected from methyl ethyl carbonate and / or diethyl carbonate; and the high-polarity solvent is selected from one or more of ethylene carbonate, acetonitrile, or dimethylformamide.

[0015] Preferably, the volume ratio of the low-polarity solvent, the medium-polarity solvent, and the high-polarity solvent is 1:(1.5~2.5):1.

[0016] Preferably, the high-throughput simulation refers to theoretical calculations performed using molecular dynamics simulations.

[0017] Preferably, the design method further includes step S3: testing and verification.

[0018] Preferably, the test verification is as follows: constructing an electrolyte and battery system according to the optimal ratio; characterizing the electrolyte system; if the characterization results are consistent with the performance change pattern simulated in step S2, then determining the electrolyte formulation according to the optimal ratio determined in step S2.

[0019] Preferably, the characterization includes testing the electrochemical performance of the battery and testing the safety performance of the electrolyte.

[0020] Preferably, the electrolyte safety performance test includes thermal stability testing and / or flame retardant performance testing.

[0021] Preferably, the electrolyte further includes an electrolyte salt and optional additives.

[0022] Preferably, the electrolyte salt is selected from any one of lithium salt, sodium salt, potassium salt or magnesium salt.

[0023] The lithium salt can be LiPF6 (lithium hexafluorophosphate, conventional application) or LiFSI (lithium bis(fluorosulfonyl)imide, preferred for high safety / wide temperature range) as the main salt, supplemented by LiDFOB (lithium difluoro(oxalato)borate) or LiTFSI (lithium bis(trifluoromethanesulfonyl)imide).

[0024] The sodium salt can use NaPF6 (sodium hexafluorophosphate, commonly used) or NaFSI (sodium bis(fluorosulfonyl)imide, preferred for high safety / wide temperature range) as the main salt, supplemented with NaDFOB (sodium difluoro(oxalato)borate) or NaTFSI (sodium bis(trifluoromethanesulfonyl)imide); the potassium salt can use KPF6 (potassium hexafluorophosphate, commonly used) or KFSI (potassium bis(fluorosulfonyl)imide, preferred for high safety / wide temperature range) as the main salt, supplemented with KDFOB (potassium difluoro(oxalato)borate) or KTFSI (potassium bis(trifluoromethanesulfonyl)imide). Magnesium salts can be Mg(TFSI)2 (magnesium bis(trifluoromethanesulfonyl)imide, commonly used) or MgCl2 (magnesium chloride, preferred for low cost) as the main salt, supplemented with Mg(BH4)2 (magnesium borohydride) or Mg(FSI)2 (magnesium bis(fluorosulfonyl)imide).

[0025] Preferably, the additive is selected from any one or more of film-forming additives, flame retardants, flame retardant diluents, or high-pressure stabilizers.

[0026] Preferably, the film-forming additive is selected from any one or more of VC (vinylene carbonate), FEC (fluoroethylene carbonate), ES (ethylene sulfate), or PS (1,3-propane sulfonate).

[0027] Preferably, the flame retardant is selected from any one or more phosphorus compounds such as MP (Trimethyl Phosphate), TEP (Triethyl Phosphate), or TFEP (Tris(2,2,2-trifluoroethyl) Phosphate).

[0028] Preferably, the flame retardant diluent is selected from low polarity fluorinated ethers, such as HFE-7100 (Hydrofluoroether-7100) and TTE (1,1,2,2-Tetrafluoroethyl 2,2,2-trifluoroethyl ether).

[0029] Preferably, the high-pressure stabilizer is selected from any one or more of ADN (Adiponitrile), SN (Succinonitrile), or TMSP (Tris(trimethylsilyl) Phosphate).

[0030] Secondly, the present invention provides an electrolyte obtained by the above-described design method.

[0031] Thirdly, the present invention provides an electrochemical energy storage device comprising an electrolyte obtained by the above-described design method.

[0032] Preferably, the electrochemical energy storage device includes a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, or a magnesium-ion battery.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) It avoids the misconception that "the higher the polarity of the solvent, the better" and fundamentally improves the upper limit of ion mobility;

[0035] (2) By using gradient polarity compounded solvents, flame retardancy and low temperature performance are improved at the same time, breaking the performance bottleneck of mutual restriction among the three, while existing technologies are difficult to maintain high ionic conductivity while improving safety.

[0036] (3) The present invention introduces a digital high-throughput simulation platform, which greatly shortens the research and development cycle, reduces experimental costs, and can be extended to the optimization design of other complex ionic soft matter systems.

[0037] In summary, this invention achieves synergistic optimization of high mobility, intrinsic flame retardancy, and wide temperature range operation performance, providing a new technical path for the development of next-generation high-safety, high-performance power battery electrolytes. Attached Figure Description

[0038] Figure 1 A flowchart illustrating the design method for the electrolyte;

[0039] Figure 2 This is a graph showing the relationship between mobility and dipole moment.

[0040] Figure 3 The graph shows the migration test results of complex systems with different gradient polarity components;

[0041] Figure 4 The electron microscope image shows lithium plating on the negative electrode of a battery assembled using a gradient polarity component compound electrolyte.

[0042] Figure 5 A comparison chart showing the rate performance of batteries assembled with electrolytes corresponding to traditional systems and gradient polarity component composite systems. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] Terminology Explanation:

[0045] 1. Lithium-ion batteries: Lithium-ion batteries are secondary battery systems that convert electrical energy into chemical energy through the repeated insertion and extraction of lithium ions between the positive and negative electrodes. These batteries typically include basic components such as a positive electrode, a negative electrode, an electrolyte, and a separator. They are characterized by high energy density and long cycle life, and are widely used in new energy vehicles, energy storage systems, and consumer electronics.

[0046] 2. Electrodes: Electrodes are the functional structural units in a battery where electrochemical reactions occur, including the positive and negative electrodes. Electrodes are typically composed of active materials, conductive agents, binders, and current collectors. Their structural uniformity, component distribution, and interface states have a significant impact on the battery's capacity, rate performance, and cycle stability.

[0047] 3. Electrolyte: The electrolyte is the ion-conducting medium used in a battery to conduct ions, and it is usually composed of salts, organic solvents, and additives. Its main function is to provide an ion transport channel between the positive and negative electrodes.

[0048] 4. Organic solvents: These are the main components in the electrolyte used to dissolve salts and provide an ion transport medium. They are usually carbonates, ethers, or fluorinated solvents. They determine the dielectric constant, viscosity, and solvation structure of the electrolyte, thereby affecting the ion dissociation ability and migration performance.

[0049] 5. Additives: These are functional components added in small amounts to the electrolyte to regulate interfacial properties and overall performance. They typically include film-forming additives, flame-retardant additives, and high-voltage stabilizing additives. They can preferentially react to form a stable interfacial film or suppress side reactions, thereby improving the cycle stability and safety performance of the battery.

[0050] 6. Intermolecular interactions: These are non-covalent forces between molecules or ions generated through electrostatic interactions, solvation effects, etc. They are key factors that determine the microstructure and macroscopic properties of electrolytes, and usually affect the solvation structure, aggregation state, and migration behavior of ions.

[0051] 7. Ion-ion interaction: refers to the Coulomb interaction between charged particles, including the attraction between cations and anions and the repulsion between ions of the same kind. It is an important factor affecting the formation of ion pairs or ion clusters and is usually closely related to the concentration of free ions and conductivity.

[0052] 8. Ion-dipole interaction: refers to the electrostatic interaction between ions and polar molecules. It is the dominant force in the solvation process and usually increases with the increase of solvent polarity, thereby promoting the dissociation of salt. However, if it is too strong, it will increase the resistance to ion migration.

[0053] 9. Dipole-dipole interaction: refers to the mutual attraction between polar molecules due to the permanent dipole moment. It usually enhances the degree of intermolecular correlation and increases the viscosity of the system, thereby affecting the ion migration rate and low-temperature phase behavior.

[0054] 10. Charge / Discharge Efficiency: Charge / discharge efficiency refers to the ratio of a battery's discharge capacity to its charge capacity in one charge / discharge cycle, usually expressed as a percentage. This parameter measures the battery's energy utilization efficiency, and its value is affected by factors such as side reactions, polarization, and ion transport efficiency.

[0055] 11. Thermal runaway: Thermal runaway refers to an uncontrollable exothermic reaction occurring inside the battery, causing the temperature to rise continuously and triggering a chain reaction. This process may be accompanied by electrolyte decomposition, electrode material reactions, etc., and in severe cases, it can lead to fire or explosion. It is an important indicator for evaluating battery safety.

[0056] 12. Ion mobility: refers to the ability of ions to move under the influence of an electric field or concentration gradient. It is an important indicator for measuring the conductivity of electrolytes and is usually positively correlated with the diffusion coefficient. According to the driving force, it can be divided into two categories: electric field migration and concentration diffusion. Its magnitude is affected by solvent viscosity, solvation intensity and ion aggregation degree. It is mainly used to characterize the ion transport efficiency and rate performance of electrolytes.

[0057] 13. Mean square displacement: A physical quantity used to characterize the mobility of particles. It is calculated by the relationship between particle displacement and time. Its slope can be used to solve for the diffusion coefficient, thus reflecting the ion migration ability. According to the time scale, it can be divided into two categories: short-term local motion and long-term diffusion behavior. It is often used in molecular dynamics simulations to quantitatively analyze the ion diffusion characteristics and dynamic mechanisms.

[0058] 14. Polarity: A physical quantity that describes the degree of non-uniformity of molecular charge distribution. It is usually characterized by dipole moment or dielectric constant. The greater the polarity, the stronger the solvation ability of the molecule to ions. According to the strength, it can be divided into three categories: low polarity, medium polarity and high polarity, which correspond to functions such as flame retardant dilution, kinetic regulation and solvation enhancement, respectively. It is a core control parameter in electrolyte design.

[0059] 15. Solvation: refers to the process by which ions and solvent molecules form a stable coordination structure through ion-dipole interactions. The degree of solvation directly affects the dispersion state and migration ability of ions. According to the structure, it can be divided into compact solvation and loose solvation, which correspond to high stability and high migration, respectively. In electrolytes, it is used to regulate ion dissociation, transport and interfacial reaction behavior.

[0060] 16. Ion clusters: These are aggregates of multiple ions formed by electrostatic interactions, which reduce the number of free ions and thus decrease conductivity. They can be classified into ion pairs, contact ion clusters, and solvent-separated ion clusters according to their structure. Their formation is closely related to the polarity and concentration of the solvent and are mainly used to describe the ion distribution and conductivity mechanism in electrolytes.

[0061] 17. Flame retardant performance: refers to the ability of a material to inhibit combustion or delay the spread of combustion under high temperature or open flame conditions. It is a key indicator of electrolyte safety. According to the mechanism of achievement, it can be divided into physical dilution type and chemical inhibition type. The former is achieved by reducing the concentration of combustible components, while the latter is achieved by capturing free radicals to inhibit the combustion reaction. It is mainly used to improve the thermal safety and resistance to thermal runaway of batteries.

[0062] 18. Lithium plating: refers to the phenomenon in which lithium ions are deposited on the electrode surface in the form of metal instead of being embedded in the electrode during the charging process, which can lead to safety risks. It can be divided into low-temperature lithium plating and high-rate lithium plating according to the conditions under which it occurs. Its occurrence is related to the limitation of ion transport and the imbalance of interfacial kinetics. It is usually used to evaluate the fast charging performance and safety of batteries.

[0063] 19. Wide temperature range stability: refers to the ability of an electrolyte system to maintain stable physicochemical properties and electrochemical performance over a wide temperature range (such as -40℃ to 80℃ or even higher), including no crystallization or glass transition at low temperatures, no thermal decomposition or violent side reactions at high temperatures, while maintaining good ion transport capacity and interfacial stability; it can be divided into low temperature stability and high temperature stability according to the temperature range, and is an important indicator for measuring the applicable environment range of an electrolyte.

[0064] 20. Gradient polarity complex: This refers to a design method that introduces solvent components with different polarities (low, medium, and high) and constructs a continuous or hierarchical polarity distribution environment in a certain proportion, so that multi-scale solvation structures exist in the system at the same time, thereby achieving synergistic regulation of ion solvation capability, low-temperature stability, and safety performance. According to the structural form, it can be divided into two categories: continuous gradient and hierarchical gradient. Functionally, it achieves the synergistic effect of high polarity promoting dissociation, medium polarity optimizing kinetics, and low polarity improving safety.

[0065] 21. Molecular Dynamics Simulation: Molecular dynamics simulation is a method that uses classical Newtonian mechanics equations to numerically calculate the trajectories of particles in a molecular system. This method can be used to study the microstructural evolution of a system, intermolecular interactions, and dynamic behavior, playing an important role in materials design and performance prediction.

[0066] To address the limitations of the existing technologies, the present invention aims to provide a digital design approach and method for electrolyte systems that balances high mobility, flame retardancy, and wide temperature range performance. The specific objectives are as follows:

[0067] (1) Clarify the influence of the dipole property of polar solvent on ion migration, that is, the migration rate shows a non-monotonic trend with solvent polarity, correct the misconception that "the higher the polarity, the better", and achieve kinetic optimization design.

[0068] (2) Provide a gradient polarity component compounding design strategy to achieve multi-performance synergy: Based on the physical mechanism discovered by simulation, a gradient compounding strategy of high polarity (for ion solubilization), medium polarity (for viscosity reduction and anti-crystallization) and low polarity (for solubilization and flame retardancy) components is proposed. The optimal component ratio that takes into account high mobility, flame retardancy and wide temperature range can be quickly locked through a high-throughput intelligent platform.

[0069] Specifically, this invention provides a design method for an electrolyte based on a gradient polarity component complex, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0070] S1: Component screening: Screening solvent components of different polarities to obtain low-polarity solvents, medium-polarity solvents and high-polarity solvents;

[0071] S2: Ratio Optimization: Set the mixing ratio ranges for low-polarity, medium-polarity, and high-polarity solvents, construct combination systems with different ratios, and use a low-scaling algorithm to establish a simplified physical model between solvent molecule polarity parameters and ion mobility in the combination systems with different ratios. This yields the kinetic performance of the combination systems with different ratios, thus performing preliminary screening. Then, high-throughput simulation is used to calculate the ion solvation structure, migration behavior, and viscosity changes of the combination systems with different ratios obtained after preliminary screening. The optimal polarity gradient window is obtained when the ion mobility reaches its peak while simultaneously meeting the requirements for flame retardant performance and wide-temperature stability. Based on the optimal polarity gradient window, the optimal ratio of low-polarity, medium-polarity, and high-polarity solvents is determined.

[0072] S3: Testing and verification: Construct the electrolyte and battery system according to the optimal ratio; characterize the electrolyte system. If the characterization results are consistent with the performance change pattern simulated in step S2, then determine the electrolyte formulation according to the optimal ratio determined in step S2.

[0073] More specifically, the design method for the electrolyte based on gradient polarity component blending includes the following steps:

[0074] I. Component Screening and Functional Classification

[0075] To achieve synergistic optimization of multiple electrolyte properties, this invention first conducts system component design and functional analysis, specifically including:

[0076] 1.1 Construction of Three Types of Polar Components

[0077] First, the electrolyte solvent system was subjected to function-oriented screening, classifying the solvent into three categories: high polarity, medium polarity, and low polarity. This function-oriented screening refers to selecting system components based on the functional differences in solvation ability, low-temperature stability, and flame-retardant properties among components of different polarities.

[0078] 1.2 Analysis of Functional Synergy Mechanism

[0079] High-polarity components enhance solubility but increase viscosity, medium-polarity components help improve kinetic performance, while low-polarity components improve safety but may weaken ion dissociation ability. Therefore, there are competitive and synergistic relationships among the components, requiring system design to optimize overall performance.

[0080] II. Polarity Gradient Proportion Design

[0081] Based on a clear understanding of the functions and interaction mechanisms of the components, the proportion space was constructed and optimized.

[0082] 2.1 Constructing the scale space and scanning

[0083] By setting different ratio ranges for polar components, a multidimensional ratio space is constructed, and a digital computing strategy that deeply integrates low-scaling algorithms and high-throughput simulation is employed to systematically scan different combinations. The low-scaling algorithm involves establishing a simplified physical model between solvent molecule polarity parameters (dipole moment, dielectric constant) and ion mobility to quickly predict the kinetic performance of systems with different ratios, thus performing preliminary screening and dimensionality reduction of candidate combinations in the high-dimensional ratio space. Subsequently, molecular dynamics simulations (such as mean square displacement calculation and radial distribution function analysis) are performed on the key ratio ranges screened by the low-scaling algorithm to accurately calculate the ion solvation structure, migration behavior, and viscosity changes. This two-level computing architecture of "low-scaling pre-screening + high-throughput precision calculation" can lock in the optimal ratio from hundreds or thousands of component combinations in a very short period, significantly reducing computational costs and solving the technical challenge of balancing multiple performance trade-offs in traditional development.

[0084] 2.2 Locking the optimal gradient window

[0085] Excessively low polarity leads to enhanced ion aggregation and decreased mobility; moderate polarity results in solvent-solvent equilibrium and maximum mobility; excessively high polarity increases viscosity due to enhanced dipole interaction, inhibiting ion migration. Therefore, an "optimal polarity gradient window" exists, within which multiple properties can be synergistically optimized. Further analysis of simulation results allows for the screening of different formulations to determine the component proportions that stably maintain the system within the optimal window, thus obtaining candidate systems.

[0086] III. Experimental and Application Testing and Verification

[0087] Based on obtaining the candidate systems and their structure-property relationships, the constructed electrolyte system was validated and optimized:

[0088] 3.1 Electrolyte and Battery System Construction

[0089] Based on the aforementioned screening and simulation analysis results, representative component combinations were selected to construct multi-component electrolyte and battery systems (such as lithium-ion battery systems). The system configuration was completed under controllable environmental conditions to ensure that each component is uniformly dispersed and forms a stable system structure.

[0090] 3.2 Multi-dimensional comprehensive characterization and analysis

[0091] Based on the simulation results, the multi-component electrolyte and battery system were characterized in multiple dimensions. The system was analyzed from the perspectives of structure, kinetics and stability to verify the rationality of the simulation results and to further understand the synergistic mechanism of different components.

[0092] 3.3 Comparative Analysis and Solution Optimization

[0093] By comparing and analyzing different systems, the reliability of the structure-performance relationship of the battery was verified, and the component design scheme was iteratively optimized accordingly, finally determining the electrolyte system scheme with excellent comprehensive characteristics.

[0094] In one embodiment of the present invention, the electrolyte system is composed of solvent components with different polarities, and a gradient polarity structure is formed by adjusting the proportion of each component to achieve synergistic optimization of multiple performance characteristics.

[0095] (1) Component functional classification based on polarity gradient

[0096] Optionally, the solvent system comprises the following three types of components:

[0097] Low-polarity solvent components include fluoroethers (HFE-7100, Hydrofluoroether-7100; TTE, 1,1,2,2-Tetrafluoroethyl 2,2,2-trifluoroethyl ether), and fluorocarbonates (FEC, Fluoroethylene Carbonate). These low-polarity solvent components provide flame retardant properties and act as a diluent in the system, reducing the overall polarity of the environment.

[0098] Medium-polarity solvent components: such as linear carbonates (EMC, Ethyl Methyl Carbonate; DEC, Diethyl Carbonate). Medium-polarity solvent components are used to reduce system viscosity, improve low-temperature stability, inhibit crystallization, dilute highly polar environments, and also have a certain solubilizing effect on ions, inhibiting lithium deposition.

[0099] Highly polar solvent components: such as strongly polar amides / nitriles (EC, ethylene carbonate; ACN, acetonitrile; DMF, dimethylformamide). Highly polar solvent components are used to enhance ion solvation capabilities, promote the dissociation of electrolyte salts, and improve ion transport capabilities.

[0100] Through the synergistic effect of the three types of components with different polarities, a balanced regulation is achieved between ion solvation, low-temperature stability and safety performance of the system.

[0101] (2) Proportion optimization law

[0102] There exists an "optimal ratio window" in the electrolyte system, determined by various intermolecular interactions. Within this window, ion solvation capability, molecular low-temperature stability, and safety performance reach a dynamic equilibrium, maximizing ion mobility. This optimal window is not a fixed value and is flexibly adjusted according to different requirements and purposes in practical applications. It shifts with changes in solvent type, molecular structure (such as dipole moment and dielectric constant), and salt concentration.

[0103] (3) Performance testing and experimental verification

[0104] In one embodiment of the present invention, a lithium-ion battery half-cell or full-cell system can be assembled based on an optimized gradient polarity compounded electrolyte system, and its electrochemical performance and safety performance can be systematically tested. The electrolyte is composed of high polarity, medium polarity and low polarity components in an optimal ratio, and is used to verify its comprehensive performance in practical applications.

[0105] The performance tests include, but are not limited to: charge-discharge tests, rate performance tests, and cycle life tests, to evaluate the battery's capacity retention capability and kinetic response under high-rate conditions; and to characterize ion migration behavior from both microscopic and macroscopic levels by analyzing interfacial impedance and ion transport characteristics through electrochemical impedance spectroscopy (EIS) and combining the mean square displacement (MSD) or diffusion coefficient calculation results.

[0106] Simultaneously, electrolyte safety performance tests were conducted, including thermal stability tests (such as differential scanning calorimetry, DSC) and flame retardant performance tests (such as ignition experiments or limiting oxygen index tests) to evaluate the stability and flame retardancy of the gradient polarity compound system under high temperature and extreme conditions; and the role of the medium polarity component in improving low temperature performance was verified through low temperature conductivity tests and phase behavior analysis (such as crystallization / glass transition tests).

[0107] Furthermore, overcharge and heating tests can be combined to comprehensively evaluate the safety performance of the electrolyte system in actual batteries. By comparing and analyzing experimental test results with molecular dynamics simulation results, the effectiveness of the proposed gradient polarity compounding strategy in regulating solvation structure, improving ion transport efficiency, inhibiting ion aggregation, and enhancing electrolyte safety and wide-temperature stability is verified, thus providing experimental basis for determining the optimal electrolyte formulation.

[0108] In some specific embodiments of the present invention, the electrolyte design method can be carried out according to the following steps:

[0109] (1) First, the solvent dipole moment is used as the core screening parameter. By constructing different dipole moment systems, the variation law of ion mobility with dipole moment is analyzed to determine the optimal polarity window. Low polarity solvents are used to reduce viscosity and enhance flame retardancy, medium polarity solvents are used to improve low temperature stability and reduce crystallization tendency, and high polarity solvents are used to enhance salt dissociation and ion solvation ability, ultimately forming a gradient polarity synergistic compounding strategy.

[0110] In this implementation scheme, the graph showing the relationship between mobility and dipole moment is as follows: Figure 2 As shown, migration initially increases and then decreases with increasing dipole moment, peaking in the region of approximately 1.5–2.0 dipole moments. These results indicate that excessively low polarity leads to insufficient salt dissociation, while excessively high polarity enhances ion binding; the moderate polarity region is most favorable for ion migration.

[0111] (2) Based on the above principles, a three-component gradient compound system of low polarity / medium polarity / high polarity was further constructed, and the migration rate of different ratios was tested. Among them, the high polarity component EC (Ethylene Carbonate) provides ionic solvation capability, the medium polarity component EMC (Ethyl Methyl Carbonate) reduces viscosity and inhibits crystallization, and the low polarity component HFE-7100 (Hydrofluoroether-7100) plays a role in flame retardancy and dilution.

[0112] In this implementation plan, the migration rate test results of different gradient composite systems are as follows: Figure 3 As shown, the low-polarity / medium-polarity / high-polarity tri-component ratio of 1:2:1 (volume ratio) exhibits the highest mobility, significantly outperforming the 1:1:1 and 1:3:1 systems. This indicates that a moderately polar component can simultaneously balance salt dissociation capability and low-temperature stability, achieving optimal synergistic transport performance.

[0113] (3) Microscopic verification: The battery system was prepared. The electrolyte composition was as follows: LiPF6 (Lithium Hexafluorophosphate) was used as the main salt, and the solvent system was a gradient polarity compound scheme of EC (Ethylene Carbonate): EMC (Ethyl Methyl Carbonate): HFE-7100 (Hydrofluoroether-7100) = 1:2:1 (volume ratio). The high polarity component EC (Ethylene Carbonate) provided ion solubilization ability, the medium polarity component EMC (Ethyl Methyl Carbonate) reduced viscosity and inhibited crystallization, and the low polarity component HFE-7100 (Hydrofluoroether-7100) played a flame retardant and diluent role. The additives included 2 wt% FEC (Fluoroethylene Carbonate, which has both film-forming and flame retardant functions) and 1 wt% VC (Vinylene Carbonate, used to assist in SEI film formation).

[0114] Battery Structure: A Li||graphite half-cell (or NCM811||graphite full cell) is constructed. The positive electrode uses NCM811 active material, conductive carbon black, and PVDF (polyvinylidene fluoride) binder coated on an aluminum foil current collector; the negative electrode uses graphite active material, conductive carbon black, and SBR (styrene-butadiene rubber) + CMC (sodium carboxymethyl cellulose) aqueous binder coated on a copper foil current collector; the separator is a Celgard 2325 polypropylene porous membrane.

[0115] The changes in lithium plating on the negative electrode after recombination were observed by electron microscopy to verify the effect of the gradient polarity system on improving interface stability. The results are as follows: Figure 4 As shown, lithium plating is significantly reduced in the gradient polarity complex system. This indicates that gradient polarity complexes can optimize the interfacial solvation structure and suppress local ion aggregation and interfacial instability.

[0116] (4) Rate performance verification: Rate charge-discharge tests were conducted on the traditional system (electrolyte of old commercial batteries, such as a carbonate-based mixed solvent system) and the gradient compound system to evaluate their ion transport capabilities under high-rate conditions. The results are as follows: Figure 5 As shown, the gradient polarity complex system maintains a high capacity retention rate even at high magnification. This indicates that the gradient polarity complex system can effectively improve the rapid migration capability of ions and the stability at high magnification.

[0117] (5) Flame retardant performance verification: The combustion flame of the gradient compound system was significantly weakened, the self-extinguishing time was shortened, and the combustion range was significantly reduced. This indicates that the low polarity flame retardant component can effectively reduce the flammability of the system and improve the thermal safety stability of the electrolyte.

[0118] In summary, the gradient compound system can simultaneously take into account ion mobility, interfacial stability, and rate performance, thereby achieving comprehensive performance optimization of the electrolyte.

[0119] It should be noted that the innovation of this invention lies in:

[0120] (1) A gradient compound system that balances high mobility, flame retardancy and wide temperature range

[0121] Based on the polarity and function of different components, the combination achieves compatibility and comprehensive performance improvement. The specific application effect of this combination scheme in engineering is as follows: Through the optimized gradient polarity formula, the ion insertion and insertion kinetics are significantly improved in a wide temperature range (especially in low temperature environment), the lithium plating of the battery is suppressed, and the system is ensured not to burn or explode under extreme collision or heating conditions.

[0122] (2) Gradient design strategy based on dynamic laws

[0123] At the thermodynamic level, by introducing components with different polarity gradients for compounding, the energy barriers for the disintegration and recombination of ion clusters are controlled, avoiding ion re-aggregation due to excessive polarity, thereby optimizing the energy distribution and system stability of the solvation configuration. At the kinetic level, the "peak window" of ion mobility is precisely locked, synergistically enhancing the ion transport rate, while suppressing the kinetic lag caused by the dominance of polarity under high-rate charge and discharge, achieving rapid and stable ion transport.

[0124] (3) High-throughput digital design path

[0125] This invention deeply integrates "low-scaling algorithms" and "high-throughput simulations," forming a digital R&D model that differs from traditional experimental verification. By automatically analyzing the structural and kinetic properties of hundreds or thousands of component combinations through algorithms, it can lock in the optimal ratio within a very short period of time, solving the technical problem of not being able to take into account multiple performance trade-offs in traditional development.

[0126] (4) Proportional optimization method based on multi-interaction competition mechanism

[0127] This invention proposes a dynamic ratio optimization strategy for multi-component systems. A rapid prediction model of polarity parameter-mobility is established through a low-scaling algorithm, and precise calculations are performed by combining molecular dynamics simulations. The system regulates the ratio of high, medium and low polarity components to achieve competitive equilibrium between ion-ion, ion-dipole and dipole-dipole interactions in the system.

[0128] In summary, this invention proposes a design method for electrolytes based on gradient polarity components, which can be widely applied to the construction of high-safety, high-performance lithium-ion battery electrolytes and related electrochemical systems. It is particularly suitable for power batteries, energy storage batteries, and high-rate batteries. Through the effective compounding of high, medium, and low polarity solvent components, the synergistic optimization of ion mobility, flame retardancy, and wide temperature range performance is achieved, thereby significantly improving the safety and stability of the battery under high temperature, low temperature, fast charging, and extreme operating conditions.

[0129] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A design method for an electrolyte based on a gradient polarity component blend, characterized in that, Includes the following steps: S1: Component screening: Screening solvent components of different polarities to obtain low-polarity solvents, medium-polarity solvents and high-polarity solvents; S2: Ratio Optimization: Set the mixing ratio range of low-polarity solvent, medium-polarity solvent, and high-polarity solvent, construct combination systems with different ratios, and use a low-scaling algorithm to establish a simplified physical model between the solvent molecule polarity parameters and ion mobility in the combination systems with different ratios. Obtain the kinetic performance of the combination systems with different ratios, thereby initially screening the combination systems with different ratios. Then, use high-throughput simulation to calculate the ion solvation structure, migration behavior, and viscosity change law of the combination systems with different ratios obtained after the initial screening, and obtain the optimal polarity gradient window where the ion mobility reaches the peak while simultaneously meeting the requirements of flame retardant performance and wide temperature range stability. Determine the optimal ratio of low-polarity solvent, medium-polarity solvent, and high-polarity solvent based on the optimal polarity gradient window.

2. The design method according to claim 1, characterized in that, The screening refers to the process of selecting solvents based on their functional differences in solvation ability, low-temperature stability, and flame retardant properties, thereby obtaining low-polarity solvents, medium-polarity solvents, and high-polarity solvents.

3. The design method according to claim 1 or 2, characterized in that, The low-polarity solvent is selected from any one or more of hydrofluoroether-7100, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, or fluoroethylene carbonate; the medium-polarity solvent is selected from methyl ethyl carbonate and / or diethyl carbonate; the high-polarity solvent is selected from any one or more of ethylene carbonate, acetonitrile, or dimethylformamide.

4. The design method according to any one of claims 1 to 3, characterized in that, The volume ratio of the low-polarity solvent, the medium-polarity solvent, and the high-polarity solvent is 1:(1.5~2.5):

1.

5. The design method according to any one of claims 1 to 4, characterized in that, The high-throughput simulation refers to theoretical calculations performed using molecular dynamics simulations.

6. The design method according to any one of claims 1 to 5, characterized in that, The design method further includes step S3: testing and verification; The test verification is as follows: construct the electrolyte and battery system according to the optimal ratio; characterize the electrolyte system; if the characterization results are consistent with the performance change law simulated in step S2, then determine the electrolyte formula according to the optimal ratio determined in step S2.

7. The design method according to claim 6, characterized in that, The characterization includes testing the electrochemical performance of the battery and the safety performance of the electrolyte. The electrolyte safety performance test includes thermal stability test and / or flame retardant performance test.

8. The design method according to claim 6 or 7, characterized in that, The electrolyte also includes electrolyte salts and optional additives; The electrolyte salt is selected from any one of lithium salt, sodium salt, potassium salt or magnesium salt; The additive is selected from any one or more of film-forming additives, flame retardants, flame retardant diluents, or high-pressure stabilizers; The film-forming additive is selected from any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, or 1,3-propanesulfonate lactone. The flame retardant is selected from any one or more of trimethyl phosphate, triethyl phosphate, and tris(2,2,2-trifluoroethyl) phosphate; The flame retardant diluent is selected from hydrofluoroether-7100 and / or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether; The high-pressure stabilizer is selected from any one or more of diisocyanate, succinate, or tris(trimethylsilyl)phosphate.

9. The electrolyte obtained by the design method according to any one of claims 1 to 8.

10. An electrochemical energy storage device, characterized in that, The electrolyte comprising the design method of any one of claims 1 to 8; The electrochemical energy storage device includes a lithium-ion battery, a sodium-ion battery, a potassium-ion battery, or a magnesium-ion battery.

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