A method for preparing a local high-concentration electrolyte, an electrolyte, a battery and a vehicle thereof

Abstract

The application discloses a preparation method of a local high-concentration electrolyte, the electrolyte, a battery and a vehicle thereof. The preparation method is used for step-by-step liquid injection of the local high-concentration electrolyte. In the first liquid injection, the electrolyte containing a carbonate-based solvent is added and is left to stand, and then the first formation treatment is carried out. In the second liquid injection, the electrolyte containing a phosphate-based solvent is added and is left to stand, and then the second formation treatment is carried out. By adopting the phosphate-based solvent with high safety performance and the carbonate-based solvent with high kinetic performance, the safety of the local high-concentration electrolyte solvent is improved, and meanwhile, the high solubility of the local high-concentration electrolyte solvent to lithium salt and the high infiltration effect of the local high-concentration electrolyte solvent to the pole piece are ensured. Compared with the phosphate-based solvent, the carbonate-based solvent mixed with the phosphate-based solvent can effectively improve the infiltration speed of the electrolyte to the pole piece, reduce the infiltration time of the battery after liquid injection, greatly improve the production efficiency, reduce the un-infiltrated dead zone such as black spots generated during the formation of the battery, and reduce the risk of lithium precipitation in the later cycle process of the battery cell.

Description

Technical Field

[0001] This invention relates to a method for preparing an electrolyte, an electrolyte, a battery, and a vehicle thereof, and more particularly to a method for preparing a locally high-concentration electrolyte, an electrolyte, a battery, and a vehicle thereof. Background Technology

[0002] Existing lithium battery electrolyte solvent systems mainly use chain carbonates combined with cyclic carbonates to balance the physical properties of the electrolyte, such as viscosity, conductivity, and saturated vapor pressure. However, carbonate solvents have the disadvantage of being flammable. When the battery experiences thermal runaway, the combustion of the carbonate solvent itself and the reaction between the carbonate solvent and the positive and negative electrode materials at high temperatures are the main sources of heat generated during battery thermal runaway.

[0003] Phosphate esters possess good flame retardancy and can be used as flame-retardant electrolyte solvents because they share similar physicochemical properties with carbonates, offer a wide variety of structures, and can scavenge free radicals generated during battery thermal runaway, thus preventing chain reactions. However, phosphate ester solvents also suffer from high viscosity, low solubility with lithium salts, poor compatibility with the negative electrode, and poor wettability, which can affect the electrolyte filling efficiency, the wetting effect of the electrolyte on the electrodes, and the physicochemical properties of the solid electrolyte interphase (SEI) film formed during formation. Therefore, phosphate ester solvents are currently not suitable as the primary solvent.

[0004] The problem of poor compatibility between phosphate ester solvent and negative electrode can be solved by increasing the lithium salt concentration. However, this method requires a large amount of lithium salt, which leads to a significant increase in electrolyte cost. Furthermore, high-concentration electrolytes have high viscosity and poor wettability at the separator and electrode interface, which has a significant impact on the rate performance and manufacturing process of lithium-ion batteries.

[0005] Therefore, existing technologies cannot use phosphate ester solvents as the main solvent while ensuring the rate performance and manufacturing efficiency of lithium-ion batteries, and can no longer meet people's requirements. Summary of the Invention

[0006] The purpose of this invention is to provide an electrolyte preparation method, an electrolyte, a battery, and a vehicle thereof. The first technical problem to be solved is to use phosphate ester solvent as the main solvent for lithium-ion batteries. The second technical problem to be solved is to improve the wetting speed of the electrolyte on the electrode sheets, reduce the wetting time after battery injection, improve production efficiency, and overcome the shortcomings of the existing technology.

[0007] This invention provides the following solution:

[0008] A method for preparing a locally high-concentration electrolyte specifically includes stepwise injection of the locally high-concentration electrolyte:

[0009] The first injection involves adding an electrolyte containing carbonate solvent and allowing it to stand.

[0010] The battery cell undergoes its first formation process;

[0011] The second injection involves adding an electrolyte containing phosphate ester solvent and allowing it to stand.

[0012] The battery cell undergoes a second formation process.

[0013] Furthermore, in the first electrolyte injection, the carbonate-containing solvent specifically includes: a certain mass fraction of lithium salt and a certain mass fraction of fluorinated ether diluent, forming a locally high-concentration electrolyte system, wherein the concentration of the lithium salt is 0.9 mol / L - 1.1 mol / L.

[0014] Furthermore, in the second injection, the phosphate ester-containing solvent includes: additives and a remaining mass fraction of lithium salt and a remaining mass fraction of fluoroether diluent.

[0015] Furthermore, the positive electrode material of the battery cell is a ternary material of lithium nickel cobalt manganese oxide, and the negative electrode is graphite.

[0016] Furthermore, in the second electrolyte injection, the lithium salt concentration is 0.1 mol / L - 0.2 mol / L, and the additives include 1,3-propanesulfonic acid lactone and vinyl sulfate, with the additive mass accounting for 2%-4% of the total electrolyte mass.

[0017] Furthermore, the first formation process of the battery cell specifically involves:

[0018] 1) Charge at a constant current of 0.02C-0.05C to the first voltage, where the first voltage ranges from 3.0 to 3.1V;

[0019] 2) Charge at a constant current of 0.05C-0.1C to the second voltage, where the second voltage ranges from 3.35V to 3.4V;

[0020] The second formation process for the battery cell specifically involves:

[0021] 1) Charge at a constant current of 0.1C-0.2C to the third voltage, which is 3.75V;

[0022] 2) Charge at a constant current of 0.33C-0.5C to 4.25V-4.4V;

[0023] 3) Charge at a constant voltage of 4.25V-4.4V until the cutoff current is 0.02C-0.05C;

[0024] 4) Discharge at a constant current of 0.33C-0.5C to 2.8V-2.5V.

[0025] A locally high-concentration electrolyte, wherein the locally high-concentration electrolyte is prepared using the aforementioned locally high-concentration electrolyte preparation method.

[0026] A battery comprising a locally high concentration of electrolyte.

[0027] A vehicle includes a battery, a battery pack, and a battery management system. The battery management system is used to monitor and manage the battery and includes a cell parameter identification module, a cloud monitoring module, and a control module.

[0028] Furthermore, the cell parameter identification module is used to monitor the data of cells using a local high-concentration electrolyte system and identify the cell voltage, temperature, self-discharge rate, and voltage parameters between cells.

[0029] The cloud monitoring module is used to monitor and analyze data from the battery pack and battery management system.

[0030] The control module is used to perform data analysis on the battery pack and battery management system, and adjust the usage strategy of the battery cells.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] This invention employs a high-safety phosphate ester solvent combined with a high-kinetic-performance carbonate solvent. This improves the safety of locally high-concentration electrolyte solvents while ensuring high solubility of lithium salts and effective wetting of the electrodes. Compared to phosphate ester solvents alone, the carbonate solvent mixed with phosphate ester solvent effectively increases the electrolyte wetting rate of the electrodes, reduces the wetting time after battery filling, significantly improves production efficiency, reduces unwetting dead zones such as black spots during battery formation, and lowers the risk of lithium plating during later cell cycles.

[0033] By employing a high-safety phosphate solvent combined with a high-kinetic-performance carbonate solvent, and using a stepwise electrolyte injection and formation method, the first injection introduces an electrolyte primarily composed of carbonate solvent, while the second injection introduces an electrolyte primarily composed of phosphate solvent. By injecting electrolytes with different solvent systems in stages, and combining this with a stepwise formation method, the wetting rate and effect of the electrolyte on the electrodes can be effectively improved, and the physicochemical properties of the solid electrolyte interphase (SEI) film can be enhanced, thereby improving battery performance.

[0034] By employing a phased formation method, combined with electrolyte solvents and additives added in stages during the electrolyte injection process, the physicochemical properties of the negative electrode SEI film and the positive electrode CEI film are optimized. This localized high-concentration electrolyte solution significantly improves safety performance while ensuring the battery's cycle performance and high-temperature performance. Attached Figure Description

[0035] 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.

[0036] Figure 1 This is a flowchart of a method for preparing locally high-concentration electrolyte.

[0037] Figure 2 This is a flowchart of a method in a specific application scenario according to an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of a battery structure that uses a locally high concentration of electrolyte.

[0039] Figure 4 It is an electric vehicle battery management system that uses a locally high-concentration electrolyte system. Detailed Implementation

[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0041] like Figure 1 The illustrated method for preparing locally high-concentration electrolyte specifically includes stepwise injection of the locally high-concentration electrolyte:

[0042] Step S1: Add electrolyte containing carbonate solvent for the first injection and let it stand;

[0043] Specifically, in the first electrolyte injection, the carbonate-containing solvent includes: a carbonate solvent, a certain mass fraction of lithium salt, and a certain mass fraction of fluorinated ether diluent, forming a locally high-concentration electrolyte system, with a lithium salt concentration of 0.9 mol / L - 1.1 mol / L. For example, 90% by mass of lithium salt is added in the first electrolyte injection.

[0044] Step S2: Perform the first formation treatment on the battery cell;

[0045] Specifically, the first formation process is as follows: 1) Charge the first voltage U1 at a constant current of 0.02C-0.05C, with the value of the first voltage U1 ranging from 3.0 to 3.1V; 2) Charge the second voltage U2 at a constant current of 0.05C-0.1C, with the value of the second voltage U2 ranging from 3.35 to 3.4V.

[0046] Step S3: For the second electrolyte injection, add an electrolyte containing phosphate ester solvent and allow it to stand. Specifically:

[0047] 1) Charge at a constant current of 0.15C to 3.75V;

[0048] 2) Charge at a constant current of 0.33C to 4.25V;

[0049] 3) Charge at a constant voltage of 4.25V until the cutoff current is 0.05C;

[0050] 4) Discharge at a constant current of 0.33C to 2.8V.

[0051] Specifically, the phosphate ester solvent in the second injection includes: phosphate ester solvent, additives, and the remaining mass fraction of lithium salt and the remaining mass fraction of fluoroether diluent. For example, the remaining 10% mass fraction of lithium salt is added to the second injection.

[0052] Specifically, in the second electrolyte injection, the lithium salt concentration is 0.1 mol / L - 0.2 mol / L, and the additives include 1,3-propanesulfonic acid lactone and vinyl sulfate. The mass of the additives accounts for 2%-4% of the total mass of the electrolyte.

[0053] Specifically, the positive electrode material of the battery cell is a ternary material of lithium nickel cobalt manganese oxide, and the negative electrode is graphite (graphite-doped silicon system). Finally, the capacity of the battery cell is tested.

[0054] Step S4 involves a second formation process for the battery cell. The steps for the second formation process are as follows:

[0055] 1) Charge at a constant current of 0.1C-0.2C to the third voltage U3, where the value of the third voltage U3 is 3.75V;

[0056] 2) Charge at a constant current of 0.33C-0.5C to 4.25V-4.4V;

[0057] 3) Charge at a constant voltage of 4.25V-4.4V until the cutoff current is 0.02C-0.05C;

[0058] 4) Discharge at a constant current of 0.33C-0.5C to 2.8V-2.5V.

[0059] In this specification, C represents the battery charge / discharge capacity rate. 1C indicates the current intensity when the battery is fully discharged in one hour. For example, if an 18650 battery with a nominal capacity of 2200mA·h is discharged completely at 1C for one hour, the discharge current will be 2200mA.

[0060] Charge / discharge rate = charge / discharge current / rated capacity; for example, a battery with a rated capacity of 100Ah discharged at 20A has a discharge rate of 0.2C. Battery discharge rate (C-rate), 1C, 2C, and 0.2C are measures of how fast a battery discharges. If the used capacity is completely discharged in 1 hour, it is called a 1C discharge; if it is completely discharged in 5 hours, it is called a 1 / 5 = 0.2C discharge. Battery capacity can generally be tested by different discharge currents. For a 24Ah battery, the 2C discharge current is 48A, and the 0.5C discharge current is 12A.

[0061] The specific values ​​of the first voltage U1, the second voltage U2, and the third voltage U3 can be determined by calculating the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels (HOMO-LUMO levels) of the solvent and additives in the locally high-concentration electrolyte system. By controlling the range of the first, second, and third voltages, the composition of the negative electrode SEI film and the positive electrode CEI film can be improved, ensuring that the FEC in the carbonate solvent mainly participates in the SEI film formation reaction before the voltage reaches the second voltage U2, significantly improving the cycle performance of the adapted silicon negative electrode. Furthermore, the 1,3-propanesulfonate lactone (PS) and vinyl sulfate (DTD) in the additives only form films within the voltage range of the second voltage U2 to the third voltage U3, reducing the cell impedance while improving the cell's high-temperature performance.

[0062] This invention also discloses a locally high-concentration electrolyte and a battery. The locally high-concentration electrolyte is prepared using a locally high-concentration electrolyte preparation method, and the battery includes the locally high-concentration electrolyte.

[0063] For the purpose of simplicity, the method steps disclosed in the above embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0064] Any flowchart or other description of a process or method can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process. Furthermore, the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed and implemented not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, or by executing computer instructions and implementing corresponding functions according to program structures such as loops, branches, etc., as will naturally be understood by those skilled in the art when practicing embodiments of the invention.

[0065] like Figure 2 and Figure 3 The implementation of the local high-concentration electrolyte preparation method in a specific application scenario, as shown in this embodiment of the invention, involves the following steps: preparing an electrolyte primarily composed of carbonate solvents → first electrolyte injection → high-temperature settling → first formation → preparing an electrolyte primarily composed of phosphate ester solvents → second electrolyte injection → high-temperature settling → second formation → battery aging and capacity testing. Furthermore, the local high-concentration electrolyte preparation method disclosed in this embodiment can be used in conjunction with... Figure 1 The embodiments shown are combined with each other. The following describes this embodiment and Figure 1 The embodiments shown, along with their associated electrolyte preparation methods, reaction principles, and working principles, are described in detail below:

[0066] Figure labeling: 1. Positive electrode; 2. Negative electrode; 3. Diaphragm; 4. Local high-concentration electrolyte.

[0067] Phosphate esters have good flame retardancy and can be used as flame-retardant electrolyte solvents because they have similar physicochemical properties and diverse structures to carbonates. Furthermore, phosphate ester solvents can eliminate free radicals generated during battery thermal runaway, thereby blocking the chain reaction of battery thermal runaway.

[0068] By incorporating carbonate solvents in conjunction with phosphate solvents, the problems of high viscosity, low solubility in lithium salts, and poor compatibility with the anode are addressed. A phased electrolyte injection and formation process is employed. The first injection adds a carbonate-based electrolyte to enhance the solvent's solubility in lithium salts and its wetting effect on the electrode. The FEC in the carbonate solvent can participate in the film formation process, improving the cycle performance of the compatible silicon anode, thereby increasing battery production efficiency and battery performance. The second injection adds a phosphate-based solvent containing additives such as 1,3-propanesulfonate lactone (PS) and vinyl sulfate (DTD), which significantly improve the battery's high-temperature performance. This phased formation process further enhances the physicochemical properties of the cathode CEI film.

[0069] In high-concentration electrolytes, anions participate in the solvation of lithium ions, drastically reducing the number of free solvent molecules. This unique solvation structure brings a series of outstanding performance characteristics, mainly due to the participation of anions in the formation of the solid-liquid interface film, which significantly alters the physicochemical properties of the film. However, high-concentration electrolytes have high viscosity, resulting in low ionic conductivity, which hinders the improvement of battery rate performance and makes large-scale application difficult.

[0070] Adding fluorinated ether diluents to locally high-concentration electrolytes can reduce the total salt concentration while preserving the local coordination environment of the high-concentration salt-solvent clusters. Lithium salts, due to their low solubility in fluorinated ether diluents, can be miscible with the soluble salt solvent in the high-concentration electrolyte to form a clear, homogeneous solution, preventing phase separation. Furthermore, fluorinated ether diluents have low viscosity, reducing the overall viscosity of the high-concentration electrolyte; and they possess sufficient stability. The locally high-concentration electrolyte obtained by adding diluents effectively compensates for the high cost, high viscosity, and poor wettability of lithium salts in high-concentration electrolytes, allowing the battery to maintain good rate performance.

[0071] In this embodiment, a phosphate-based locally high-concentration electrolyte is used, composed of lithium salt, phosphate solvent, carbonate solvent, and fluorinated ether diluent. The lithium salt is lithium bis(fluorosulfonyl)imide (LFSI), the phosphate solvent is triethyl phosphate (TEP), and the carbonate solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) in a mass ratio of 1:1:1. The mass ratio of phosphate solvent to carbonate solvent is 1:3. Additives are 1,3-propanesulfonic acid lactone (PS) and ethylene sulfate (DTD), accounting for 1% and 1.5% of the total electrolyte mass, respectively. The positive electrode material is Ni92 ternary material, and the negative electrode is a graphite-doped silicon system.

[0072] The electrolyte is injected in stages. The first injection is an electrolyte mainly composed of carbonate solvents, including carbonate solvents, 90% lithium salt by mass, and 90% fluorinated ether diluent, forming a locally high-concentration electrolyte system with a lithium salt concentration of 1.1 mol / L.

[0073] The positive electrode material of the battery cell is lithium nickel cobalt manganese oxide ternary material, and the negative electrode is graphite. The formation process of the battery cell is as follows: 1) 0.05C constant current charging to 3.0V, 2) 0.1C constant current charging to 3.4V.

[0074] The second electrolyte injection involves adding an electrolyte primarily composed of phosphate ester solvents, including phosphate ester solvents, additives, and the remaining 10% by mass of lithium salt and the remaining 10% by mass of fluorinated ether diluent. The specific steps are as follows: 1) 0.15C constant current charging to 3.75V, 2) 0.33C constant current charging to 4.25V, 3) 4.25V constant voltage charging to a cutoff current of 0.05C, and 4) 0.33C constant current discharging to 2.8V.

[0075] Comparative example:

[0076] A locally high-concentration electrolyte was used, composed of lithium salt, carbonate solvent, and fluorinated ether diluent. The lithium salt was selected from lithium bis(fluorosulfonyl)imide (LFSI), and the carbonate solvent included ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) in a mass ratio of 1:1:1. Additives were 1,3-propanesulfonate lactone (PS) and ethylene sulfate (DTD), accounting for 1% and 1.5% of the total electrolyte mass, respectively, with a lithium salt concentration of 1.1 mol / L. In this comparative example, a conventional injection formation method was used, without employing partial injection or distributed formation methods.

[0077] The above battery cells were tested, and the test results are as follows:

[0078] project Example Comparative Example DCR (2C discharge, test for 10 seconds) 0.735 0.813 ACR (1000Hz) 0.532 0.596 Monthly self-discharge rate (stored at 25℃) 1.24% 1.43%

[0079] A comparison between this embodiment and the comparative example shows that the battery cell produced by the step-by-step liquefaction process in this embodiment has higher production efficiency, lower production cost, and better rate performance and charge retention capability.

[0080] Based on the above embodiments, the embodiments of the present invention can be further improved as follows: a locally high-concentration electrolyte, which is composed of lithium salt, phosphate ester solvent, carbonate solvent, and fluorinated ether diluent. The lithium salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate. The phosphate ester solvent is selected from at least one of triargyl phosphate (TPP) and triethyl phosphate (TEP). The carbonate solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate, ethyl carbonate (DEC), methyl ethyl carbonate (EMC), and fluoroethylene carbonate (FEC). The mass ratio of phosphate ester solvent to carbonate solvent is 15%-30%:70%-85%. The additives include at least one of 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), vinylene carbonate (VC), and lithium difluorophosphate (LiPO2F2). This electrolyte system is suitable for both liquid lithium-ion batteries and semi-solid lithium-ion batteries.

[0081] In existing technologies, phosphate esters are used as solvent components, forming a solvated structure with lithium salts in a certain ratio and dispersed in fluorinated ether solvents. However, this cannot solve the problems of high viscosity, low solubility with lithium salts, and poor compatibility with the negative electrode of phosphate ester solvents. Furthermore, batteries using phosphate ester solvents alone have poor rate performance, and using phosphate ester solvents cannot improve the rate performance, cycle performance, and high-temperature performance of the battery.

[0082] In this embodiment of the invention, phosphate esters, due to their similar physicochemical properties and diverse structures to carbonates, and because phosphate ester solvents can effectively eliminate free radicals generated during battery thermal runaway, thereby blocking the chain reaction of battery thermal runaway, exhibit good flame retardancy and can be used as flame-retardant electrolyte solvents. Phosphate ester flame retardants decompose to generate PO· free radicals, while polymers decompose during combustion to form small amounts of hydrogen free radicals (H·) and hydroxyl free radicals (HO·). The PO· free radicals generated from the decomposition of phosphorus-based flame retardants can capture H· and HO· to ​​form HPO, thereby preventing or slowing down the combustion chain reaction and enhancing the flame retardant effect. Furthermore, phosphate ester flame retardants decompose at high temperatures to generate phosphorus-containing flame-retardant gases, reducing the concentration of combustible gases and thus delaying the spread of flames.

[0083] Based on the above embodiments, the present invention can be further improved: the present invention provides a carbonate solvent plus phosphate solvent flame-retardant electrolyte system: in existing high-voltage lithium-ion battery electrolytes, the electrolyte is usually a locally high-concentration electrolyte, the organic solvent is selected from carbonate solvents, and the diluent is selected from fluorinated ether compounds. However, this locally high-concentration electrolyte cannot significantly improve the safety of the electrolyte and cannot effectively suppress the thermal runaway reaction of the battery. Other technical problems existing in the prior art include: using phosphate ester as a solvent component, but failing to solve the problems of high viscosity of phosphate ester solvent, low solubility with lithium salt, and poor compatibility with the negative electrode.

[0084] In this embodiment of the invention, by adding a carbonate solvent in conjunction with a phosphate solvent, the problems of high viscosity, low solubility of phosphate solvents with lithium salts, and poor compatibility with the negative electrode are solved. Through fractional electrolyte injection, the first injection incorporates a carbonate-based electrolyte, enhancing the solvent's high solubility for lithium salts and its high wetting effect on the electrode, thereby improving battery production efficiency and battery performance. Furthermore, the FEC in the carbonate solvent can participate in the film formation process, improving the cycle performance of the compatible silicon negative electrode.

[0085] Based on the above embodiments, the embodiments of the present invention can be further improved: the embodiments of the present invention provide a local high-concentration electrolyte system: the defects of the existing high-voltage lithium-ion battery electrolyte are that its organic solvent is selected from carbonate solvent, which cannot significantly improve the safety of the electrolyte and cannot effectively suppress the thermal runaway reaction of the battery.

[0086] In this invention, fluorinated ethers are used. Fluorinated ethers have low viscosity and good interfacial wettability. When used in conjunction with carbonate solvents, they effectively solve the problems of high viscosity, low conductivity, and poor wettability of pure phosphate solvents on electrodes and separators. Adding fluorinated ether diluents to locally high-concentration electrolytes reduces the total salt concentration while preserving the local coordination environment of high-concentration salt-solvent clusters. This allows anions to participate in the formation of the solid-liquid interface film, significantly altering its physicochemical properties. This addresses the shortcomings of high-concentration lithium salt electrolytes, such as high cost, high viscosity, and poor wettability, enabling the battery to maintain good rate performance.

[0087] Based on the above embodiments, the embodiments of the present invention can be further improved as follows:

[0088] A method for preparing a locally high-concentration electrolyte includes the following steps:

[0089] 1. Prepare two separate electrolyte solutions for the step-by-step electrolyte filling process. The first electrolyte added is a carbonate-based solvent, including carbonate solvent, lithium salt, and fluorinated ether diluent, forming a locally high-concentration electrolyte system with a lithium salt concentration of 0.9 mol / L - 1.1 mol / L. The carbonate solvent can improve the solubility of lithium salt and enhance the electrolyte's wetting effect on the electrodes. After the first electrolyte filling, minimize the battery's settling time.

[0090] 2. The electrolyte added in the second electrolyte injection is a phosphate ester solvent-based electrolyte, including phosphate ester solvent, additives, and the remaining lithium salt and fluorinated ether diluent. The lithium salt concentration is 0.1 mol / L - 0.2 mol / L. The additives include 1,3-propanesulfonate lactone (PS) and vinyl sulfate (DTD), which have significant effects on improving the high-temperature performance of the battery. The additives account for 2%-4% of the total electrolyte mass.

[0091] The shortcomings of the existing technology are: the existing technology uses phosphate ester as a solvent component and does not adopt the electrolyte injection scheme of adding electrolyte with carbonate solvent as the main component and electrolyte with phosphate ester solvent as the main component. Therefore, it cannot solve the problems of high viscosity of phosphate ester solvent, low solubility with lithium salt, and poor compatibility with negative electrode. In addition, phosphate ester solvent has a significant impact on the rate performance of battery.

[0092] The carbonate solvent in this invention can improve the solubility of lithium salts and enhance the wettability of the electrolyte on the electrodes. This reduces the battery's settling time after the initial electrolyte filling.

[0093] Based on the above embodiments, the embodiments of the present invention can be further improved as follows:

[0094] The stepwise preparation method for locally high-concentration electrolytes specifically includes:

[0095] 1. The electrolyte is added in stages. The first stage involves adding an electrolyte primarily composed of carbonate solvents, including carbonate solvents, lithium salts, and fluorinated ether diluents.

[0096] 2. Allow to stand to allow the electrolyte to fully wet the electrode.

[0097] 3. In the formation of the battery, fluoroethylene carbonate (FEC) in the carbonate solvent can participate in the film formation process, which can significantly improve the cycle performance of the adapted silicon anode, thereby improving the battery production efficiency and battery performance.

[0098] The formation process is as follows:

[0099] 1) Charge at a constant current of 0.02C-0.05C until voltage U1′ is reached, where U1′ ranges from 3.0 to 3.1V.

[0100] 2) Charge at a constant current of 0.05C-0.1C until voltage U2′ is reached, where U2′ ranges from 3.35V to 3.4V.

[0101] 4. The specific values ​​of voltages U1′ and U2′ are determined by calculating the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels (HOMO-LUMO energy levels) of the solvent and additives in the local high-concentration electrolyte system.

[0102] 5. The second electrolyte injection involves adding a phosphate ester-based solvent, including phosphate ester solvents, additives, and the remaining lithium salt and fluorinated ether diluents. The additives include 1,3-propanesulfonate lactone (PS) and vinyl sulfate (DTD), which significantly improve the high-temperature performance of the battery. This fractional formation enhances the physicochemical properties of the positive electrode CEI film.

[0103] 6. Perform capacity testing on the battery cells, the procedure is as follows:

[0104] 1) Charge to 3.75V using a constant current of 0.1C-0.2C.

[0105] 2) Constant current charging at 0.33C-0.5C to 4.25V-4.4V.

[0106] 3) Charge at a constant voltage of 4.25V-4.4V until the cutoff current is 0.02C-0.05C.

[0107] 4) Constant current discharge at 0.33C-0.5C to 2.8V-2.5V

[0108] The existing technology has the following drawbacks: when using phosphate esters as solvent components, it always employs a step-by-step injection and formation method, which cannot solve the problems of high viscosity of phosphate ester solvents, low solubility with lithium salts, and poor compatibility with the negative electrode. However, the embodiments of this invention optimize the battery performance using a step-by-step injection and formation method, thereby achieving the goal of controlling the physicochemical properties of the negative and positive electrode films.

[0109] like Figure 4 As shown, this embodiment of the invention also provides a vehicle, including a battery with a locally high concentration of electrolyte, a battery pack, and a battery management system. The battery management system is used to monitor and manage the battery, and includes a cell parameter identification module, a cloud monitoring module, and a control module.

[0110] Preferably, the cell parameter identification module is used to monitor the data of cells using a local high-concentration electrolyte system, and to identify the cell voltage, temperature, self-discharge rate, and voltage parameters between cells;

[0111] The cloud monitoring module is used to monitor and analyze data from the battery pack and battery management system.

[0112] The control module is used to perform data analysis on the battery pack and battery management system, and adjust the usage strategy of the battery cells.

[0113] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, any of the claimed embodiments can be used in any combination.

[0115] 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.

[0116] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0117] In addition, the functional modules in the various embodiments of the present invention can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0118] All features disclosed in this specification, or steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps. Any feature disclosed in this specification, unless specifically stated otherwise, may be replaced by other equivalent or similar features. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features. Throughout this specification, the same reference numerals indicate the same elements.

[0119] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the corresponding claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the corresponding claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a locally high-concentration electrolyte, characterized in that, Specifically, this includes the stepwise injection of locally high-concentration electrolyte: The electrolyte containing carbonate solvent is added during the first injection and allowed to stand. In the first injection, the electrolyte containing carbonate solvent includes carbonate solvent, a certain mass fraction of lithium salt, and a certain mass fraction of fluorinated ether diluent to form a locally high-concentration electrolyte system. The concentration of the lithium salt is 0.9 mol / L - 1.1 mol / L. The battery cell undergoes its first formation process; The second injection involves adding an electrolyte containing a phosphate ester solvent and allowing it to stand. In the second injection, the electrolyte containing the phosphate ester solvent includes: a phosphate ester solvent, an additive, and a remaining mass fraction of lithium salt and a remaining mass fraction of fluorinated ether diluent. The mass ratio of the phosphate solvent to the carbonate solvent is 15%-30%: 70%-85%; The additive includes 1,3-propanesulfonate lactone and vinyl sulfate. The battery cell undergoes a second formation process.

2. The method for preparing a locally high-concentration electrolyte according to claim 1, characterized in that, The carbonate solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) in a mass ratio of 1:1:

1.

3. The method for preparing a locally high-concentration electrolyte according to claim 1, characterized in that, The positive electrode material of the battery cell is a ternary material of lithium nickel cobalt manganese oxide, and the negative electrode is graphite.

4. The method for preparing a locally high-concentration electrolyte according to claim 1, characterized in that, In the second electrolyte injection, the lithium salt concentration was 0.1 mol / L - 0.2 mol / L, and the additive mass accounted for 2%-4% of the total electrolyte mass.

5. The method for preparing a locally high-concentration electrolyte according to claim 1, characterized in that, The first formation process for the battery cell specifically involves: 1) Charge at a constant current of 0.02C-0.05C to the first voltage, where the first voltage ranges from 3.0 to 3.1V; 2) Charge at a constant current of 0.05C-0.1C to the second voltage, where the second voltage ranges from 3.35V to 3.4V; The second formation process for the battery cell specifically involves: 1) Charge at a constant current of 0.1C-0.2C to the third voltage, which is 3.75V; 2) Charge at a constant current of 0.33C-0.5C to 4.25V-4.4V; 3) Charge at a constant voltage of 4.25V-4.4V until the cutoff current is 0.02C-0.05C; 4) Discharge at a constant current of 0.33C-0.5C to 2.8V-2.5V.

6. A locally high-concentration electrolyte, characterized in that, The local high-concentration electrolyte is prepared using the local high-concentration electrolyte preparation method according to any one of claims 1 to 5.

7. A battery, characterized in that, The battery includes the locally high-concentration electrolyte as described in claim 6.

8. A vehicle, characterized in that, The battery as described in claim 7 is further comprising a battery pack and a battery management system, wherein the battery management system is used to monitor and manage the battery and includes a cell parameter identification module, a cloud monitoring module, and a control module.

9. The vehicle according to claim 8, characterized in that, The cell parameter identification module is used to monitor the data of cells using a local high-concentration electrolyte system and identify the cell's voltage, temperature, self-discharge rate, and voltage parameters between cells. The cloud monitoring module is used to monitor and analyze data from the battery pack and battery management system. The control module is used to perform data analysis on the battery pack and battery management system, and adjust the usage strategy of the battery cells.

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