Silicon difluorophosphate product and application thereof, electrolyte and battery

Abstract

The invention discloses a silicon difluorophosphate product and application thereof, an electrolyte and a battery. The silicon difluorophosphate has a chemical formula shown in a formula I, r1, R2 and R3 are respectively and independently selected from any one of a hydrogen atom, a fluorine atom, alkyl of C1-C4, fluoroalkyl of C1-C4, alkenyl of C2-C4, fluoroalkenyl of C2-C4, alkynyl of C2-C4, cycloalkane of C5-C7, substituted or unsubstituted phenyl and substituted or unsubstituted benzyl; the content of the difluorophosphoric acid in the silicon difluorophosphate product is 0.05 ppm to 2000 ppm, and the difluorophosphoric acid is obtained by hydrolyzing the silicon difluorophosphate. By controlling the content of the difluorophosphoric acid, dissociation of lithium ions in the electrolyte from a lithium salt ion pair structure can be promoted, and the ionic conductivity of the electrolyte is improved; dissociation of lithium ions in a solvation sheath structure in an electrode interface and transmission of lithium ions in an interface film can be promoted, and comprehensive improvement of high-temperature circulation and high-temperature storage performance of the battery is realized by integrating other effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrolyte, in particular, to a silicon difluorophosphate product and application thereof, an electrolyte and a battery. BACKGROUND

[0002] At present, lithium ion batteries are widely used in digital products, electric vehicles and other fields due to the advantages of low cost, high safety and high energy density, and the demand for lithium ion batteries is increasing. However, there are residual alkaline substances in the positive active material of lithium ion batteries, which will have a great negative impact on the performance of the battery, causing capacity attenuation, poor high-temperature performance and many other problems. Therefore, the current lithium ion battery still needs to be further improved. It should be noted that the above statements are only used to provide background technical information related to the present application, and do not necessarily constitute the prior art. SUMMARY

[0003] In the first aspect of the present application, a silicon difluorophosphate product is provided, and the silicon difluorophosphate has a chemical formula as shown in formula 1: Formula I, wherein R1, R2, R3 are each independently selected from any one of a hydrogen atom, a fluorine atom, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C2-C4 alkenyl group, a C2-C4 fluoroalkenyl group, a C2-C4 alkynyl group, a C5-C7 cycloalkane, a substituted or unsubstituted phenyl group, and a substituted or unsubstituted benzyl group; the content of difluorophosphoric acid in the silicon difluorophosphate product is 0.05 ppm-2000 ppm, and the difluorophosphoric acid is obtained by hydrolysis of the silicon difluorophosphate.

[0004] By controlling the content of difluorophosphoric acid to be 0.05 ppm-2000 ppm, the difluorophosphoric acid can participate more in the solvation structure of lithium ions, promote the dissociation of lithium salt ions in the electrolyte, and thus improve the solubility of lithium salt and the ionic conductivity of the electrolyte. Further, based on the effect that the silicon difluorophosphate preferentially undergoes electrochemical reaction to participate in the construction of the interface film, and the interface film constructed is rich in P-F, P=O and Si-O components, the dissociation of lithium ions in the solvation sheath structure in the electrode interface can be promoted, the interface film has high acid corrosion resistance due to its dense stability and the coordination of organic / inorganic components, and has strong interaction with lithium ions, which promotes the dissociation of solvated lithium ions, improves the transfer rate of lithium ions in the interface, reduces the interface impedance, and comprehensively improves the high-temperature cycle and high-temperature storage performance of the battery.

[0005] In some embodiments, the mass percentage of difluorophosphoric acid in the silicon difluorophosphate is 1 ppm to 1500 ppm. In this way, the alkaline substance in the battery can be effectively eliminated, and the influence on other substances in the battery liquid is small.

[0006] In some embodiments, the silicon difluorophosphate includes at least one of the following structural formulas: Compound 1, Compound 2, Compound 3, Compound 4, Compound 5, Compound 6, Compound 7, Compound 8, Compound 9, Compound 10, Compound 11, Compound 12, Compound 13, Compound 14, Compound 15, Compound 16, Compound 17, Compound 18, Compound 19, Compound 20, Compound 21, Compound 22. In this way, the side reaction between the electrolyte and the residual alkali on the surface of the positive active material can be reduced.

[0007] In a second aspect of the present application, the present application provides a silicon difluorophosphate product, the content of difluorophosphoric acid in the silicon difluorophosphate product is 2000 ppm based on the mass of the silicon difluorophosphate, under the condition that the moisture in the storage environment or the operating environment is less than or equal to 0.15 mg / cm 3 for not more than 150 days.

[0008] In some embodiments, the content of difluorophosphoric acid in the silicon difluorophosphate product is 0.05 ppm to 1500 ppm based on the mass of the silicon difluorophosphate, under the condition that the moisture in the storage environment or the operating environment is less than or equal to 0.12 mg / cm 3 for not more than 100 days.

[0009] In some embodiments, the content of difluorophosphoric acid in the silicon difluorophosphate product is 1200 ppm based on the mass of the silicon difluorophosphate, under the condition that the temperature is not higher than 25 ℃, and the operation or storage is not more than 150 days.

[0010] In some embodiments, the content of difluorophosphoric acid in the product of silicon difluorophosphate is 1000 ppm, based on the mass of silicon difluorophosphate, when the product is operated or stored for no more than 100 days at a temperature of no higher than 0 ℃.

[0011] In a third aspect of the present application, the present application provides an application of the product of silicon difluorophosphate in the field of electrolyte and battery.

[0012] In a fourth aspect of the present application, the present application provides an electrolyte comprising the product of silicon difluorophosphate. Thus, the electrolyte has all the features and advantages of the product of silicon difluorophosphate, which will not be repeated here.

[0013] In some embodiments, the mass fraction of silicon difluorophosphate in the electrolyte is 0.05%-5.0%. Thus, by matching an appropriate amount of silicon difluorophosphate and corresponding difluorophosphoric acid, a synergistic effect can be better played to jointly improve the high-temperature storage and high-temperature cycle performance of the battery of the electrolyte.

[0014] In some embodiments, the mass fraction of silicon difluorophosphate in the electrolyte is 0.5%-2.5%.

[0015] In a fifth aspect of the present application, the present application provides a battery comprising the product of silicon difluorophosphate or the electrolyte. Thus, the battery has all the features and advantages of the product of silicon difluorophosphate and the electrolyte, which will not be repeated here.

[0016] In some embodiments, the battery further comprises a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, and the positive electrode active material comprising a nickel-cobalt-manganese ternary material. Thus, the energy density of the battery can be further improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the description of the embodiments, taken in conjunction with the following drawings in which: Figure 1 NMR F spectrum of compound 2 according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] Embodiments of the present application are described in detail below with reference to the accompanying drawings. Examples of the embodiments are shown in the drawings, but there will be cases where unnecessary detailed descriptions are omitted. For example, there will be cases where detailed descriptions of matters known well, repeated descriptions of substantially the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0019] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0020] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0021] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0022] Highly reactive difluorophosphate silicon ester preferentially reacts with the solvent in the electrolyte during battery charging and discharging. The silicon-based groups undergo electrochemical polymerization to form polysiloxanes that coat the surface of the positive electrode active material, inhibiting the direct reaction between residual alkali on the surface of the positive electrode active material and the electrolyte. Meanwhile, lithium fluoride, lithium phosphate, and Li2O3 are produced by the fluorophosphate groups. x PO y F z Inorganic lithium salt components help improve the lithium-ion conductivity, residual alkali resistance, and free F resistance of the aforementioned polysiloxane film. - Corrosive.

[0023] Lithium hexafluorophosphate and silicon difluorophosphate react with water to hydrolyze and form difluorophosphoric acid. Hydrolysis can be effectively suppressed by controlling the water content in the electrolyte. However, during battery charging and discharging, the chemical or electrochemical decomposition of the solvent generates water, leading to continued hydrolysis. Introducing trace amounts of difluorophosphoric acid into the system can inhibit the forward hydrolysis reaction, thus suppressing the hydrolysis process. Simultaneously, difluorophosphoric acid can form hydrogen bonds with the solvent, participating in the solvation structure of lithium ions and regulating their dissociation.

[0024] Further, by controlling the content of difluorophosphoric acid to be 0.05 ppm-2000 ppm, the difluorophosphoric acid has a smaller volume, more hydrogen bonding sites, and stronger lithium ion affinity, can participate more in the solvation structure of lithium ions and produce a better stabilizing effect on the solvation sheath structure and the solvent molecules therein, reduce the ion pair ratio in the solution, promote the dissociation of lithium ions in the electrolyte, and thus improve the ionic conductivity of the electrolyte. On the other hand, on the basis of the interface film component preventing the decomposition reaction of the solvent molecules, the stable solvation sheath and solvent molecules of the difluorophosphoric acid have better pressure stability, further inhibit the electrochemical decomposition of the solvent molecules. After the silicon-based difluorophosphate ester preferentially undergoes an electrochemical reaction to participate in the construction of the interface film, the interface film constructed is rich in P-F, P=O and Si-O components, promotes the dissociation of lithium ions in the solvation sheath structure at the electrode interface, and under the coordination of its dense stability and organic / inorganic components, endows the interface film with a higher acid corrosion resistance, and has a stronger interaction with lithium ions, promotes the dissociation of solvated lithium ions, improves the transfer rate of lithium ions at the interface, reduces the interface impedance, and comprehensively improves the high-temperature cycle and high-temperature storage performance of the battery through the comprehensive effect of other effects.

[0025] In the first aspect of the present application, the present application proposes a silicon difluorophosphate product, the silicon difluorophosphate has a chemical formula as shown in formula 1: Formula I, wherein R1, R2, R3 are each independently selected from any one of a hydrogen atom, a fluorine atom, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C2-C4 alkenyl group, a C2-C4 fluoroalkenyl group, a C2-C4 alkynyl group, a C5-C7 cycloalkane, a substituted or unsubstituted phenyl group, and a substituted or unsubstituted benzyl group; the content of difluorophosphoric acid in the silicon difluorophosphate product is 0.05 ppm-2000 ppm, and the difluorophosphoric acid is obtained by hydrolysis of the silicon difluorophosphate.

[0026] Therefore, by controlling the content of difluorophosphoric acid to be 0.05 ppm-2000 ppm, the difluorophosphoric acid can participate more in the solvation structure of lithium ions, promote the dissociation of lithium salt ions in the electrolyte, and thus improve the solubility of the lithium salt and the ionic conductivity of the electrolyte. Further, based on the effect that the silicon difluorophosphate preferentially undergoes an electrochemical reaction to participate in the construction of the interface film, and the interface film constructed is rich in P-F, P=O and Si-O components, which can promote the dissociation of lithium ions in the solvation sheath structure at the electrode interface, and under the coordination of its dense stability and organic / inorganic components, endows the interface film with a higher acid corrosion resistance, and has a stronger interaction with lithium ions, promotes the dissociation of solvated lithium ions, improves the transfer rate of lithium ions at the interface, reduces the interface impedance, and comprehensively improves the high-temperature cycle and high-temperature storage performance of the battery through the comprehensive effect of other effects.

[0027] In some embodiments, the mass percentage of difluorophosphoric acid in the difluorophosphate silicon ester is 1 ppm to 1500 ppm. Therefore, an appropriate amount of difluorophosphoric acid can effectively eliminate alkaline substances in the battery while having minimal impact on other substances in the battery fluid, thus improving the stability of the electrolyte.

[0028] As an example, the mass percentage of difluorophosphoric acid in difluorophosphoric acid silicate is 0.05ppm, 0.1ppm, 0.5ppm, 1ppm, 5ppm, 10ppm, 15ppm, 20ppm, 25ppm, 30ppm, 35ppm, 40ppm, 45ppm, 50ppm, 55ppm, 60ppm, 65ppm, 70ppm, 75ppm, 80ppm, 85ppm, 90ppm, 95ppm, 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, or 2000ppm.

[0029] In some embodiments, when at least one of R1, R2, and R3 is a substituted or unsubstituted phenyl group, the substituent may be a fluorine atom, methyl, ethyl, vinyl, ethynyl, etc.

[0030] In some embodiments, when at least one of R1, R2, and R3 is a substituted or unsubstituted benzyl group, the substituent may be a fluorine atom, methyl, ethyl, vinyl, ethynyl, etc.

[0031] In some embodiments, the difluorophosphate silicon ester product itself contains a small amount of difluorophosphoric acid. Specifically, the raw materials used in the preparation process of the difluorophosphate silicon ester product may hydrolyze or undergo side reactions, thereby producing difluorophosphoric acid. Simultaneously, the difluorophosphate silicon ester itself is relatively sensitive to moisture and may also produce difluorophosphoric acid due to hydrolysis. Based on this, the content of difluorophosphoric acid in the difluorophosphate silicon ester product can be controlled according to actual conditions, so that the composition of the difluorophosphate silicon ester product meets the usage requirements.

[0032] As an example, the amount of difluorophosphate in the silicon difluorophosphate can be determined by the ambient water content during the preparation / storage process. This eliminates the need for the additional addition of difluorophosphate, allowing the silicon difluorophosphate containing the appropriate amount of difluorophosphate to be used directly as a silicon difluorophosphate product.

[0033] As an example, when the content of difluorophosphate in the difluorophosphate silicon ester product is too high, the excess difluorophosphate can be removed during the synthesis process by means of vacuum distillation, etc.; when the content of difluorophosphate in the difluorophosphate silicon ester product is too low, the required amount of difluorophosphate can be added directly to the difluorophosphate silicon ester product.

[0034] When difluorophosphate silicon ester contains a certain amount of difluorophosphate, its overall performance is even better, especially for batteries under high voltage and high temperature conditions, the problems of battery swelling and abnormal increase in impedance are well solved.

[0035] In some embodiments, the mass percentage of difluorophosphate is 1 ppm to 1500 ppm, based on the mass of silicon difluorophosphate. This effectively eliminates alkaline substances in the battery with minimal impact on other substances in the battery fluid.

[0036] By utilizing the characteristic that difluorophosphoric acid can quickly react with residual alkali to remove it, the amount of difluorophosphoric acid used can be controlled to effectively eliminate residual alkali while reducing losses caused by side reactions between acidic substances and positive electrode active materials, thus reducing the consumption and decomposition of electrolyte.

[0037] In some embodiments, difluorophosphate silicate comprises at least one of the following structural formulas: Compound 1 (CAS No.: 2708941-25-5), Compound 2 (CAS No.: 4419-25-9), Compound 3 (CAS No.: 13683-39-1) Compound 4 (CAS No.: 4414-27-1), Compound 5 (CAS No.: 4414-26-0), Compound 6 (CAS No.: 4480-02-8), Compound 7 (CAS No.: 2577172-95-1), Compound 8 (CAS No.: 13683-40-4), Compound 9 (CAS No.: 2577172-93-9), Compound 10 (CAS No.: 2708941-27-7), Compound 11 (CAS No.: 2287283-36-5), Compound 12 (CAS No.: 6231-57-8), Compound 13 (CAS No.: 1386-54-9), Compound 14 (CAS No.: 2708941-26-6), Compound 15 (CAS No.: 6231-58-9), Compound 16 (CAS No.: 6231-59-0), Compound 17 (CAS No.: 2577172-94-0), Compound 18 Compound 19 Compound 20 Compound 21 Compound 22. This reduces side reactions between the electrolyte and residual alkali on the surface of the positive electrode active material.

[0038] As an example, difluorophosphate silicon ester can be prepared by the following method: Under anhydrous conditions, sodium difluorophosphate (50 mmol, moisture ≤ 20 ppm) is added to a reaction vessel, followed by ultra-dry acetonitrile solvent (550 mmol). The solid is stirred and dissolved at a controlled temperature of 20℃-60℃. Then, a chlorosilane (50 mmol, moisture ≤ 20 ppm) is slowly added, maintaining a nitrogen atmosphere and stirring continuously at 20℃-60℃ for about 8 hours during the addition of the chlorosilane. After the reaction is complete, the mixture is allowed to stand at room temperature for about 2 hours, then filtered to remove the solid precipitate. Finally, nitrogen is bubbled to remove the solvent and volatile byproducts, thus obtaining the desired difluorophosphate silicon ester.

[0039] As examples, the chlorosilane used in preparing compound 18 can be vinylchlorosilane (CAS No.: 1871-21-2); the chlorosilane used in preparing compound 19 can be dimethylynyl butylchlorosilane (CAS No.: 2069196-19-4); the chlorosilane used in preparing compound 20 can be dimethyl (trifluoropropenyl)chlorosilane (CAS No.: 89705-02-2); the chlorosilane used in preparing compound 21 can be tris(pentafluoroethyl)chlorosilane (CAS No.: 1620665-21-5); and the chlorosilane used in preparing compound 22 can be dimethyl (p-methylbenzyl)chlorosilane (CAS No.: 1833-28-9).

[0040] As an example, the difluorophosphate content in difluorophosphate silicate can be tested using the following method, specifically: Standard curve NMR characterization: A series of quantitative difluorophosphoric acid solutions were transferred to sample vials, and a fixed amount of fluorobenzene was added as an internal standard. The solution was then diluted to 100 mL with dehydrated EMC solvent. After complete dissolution, 500 μL of the solution was added to an NMR tube, followed by the addition of NMR reagent d6-DMSO. After mixing, NMR F-spectrum analysis was performed (Bruker NMR). 19 F-NMR 376MHz standard test).

[0041] Data Analysis: The chemical shift of F in the internal standard fluorobenzene in the F spectrum was qualitatively determined. After determining the chemical shift, peak area integration and normalization were performed. Then, the peak chemical shift of difluorophosphoric acid was assigned, and its peak area was integrated. A standard curve was plotted using the (difluorophosphoric acid / fluorobenzene) peak area ratio against the molar ratio of F content. R 2 ≥0.99.

[0042] Sample testing and analysis: A solid mass of silicon difluorophosphate sample was transferred to an NMR tube, a certain amount of fluorobenzene standard was added, followed by NMR reagent d6-DMSO. After shaking well, NMR F-spectrum analysis was performed (Bruker NMR). 19 (F-NMR 376MHz standard test). Determine the peak position of difluorophosphate in the sample, calculate its peak area and compare it with the fluorobenzene standard to determine the position of the peak area ratio in the working curve. The content of difluorophosphate in the difluorophosphate silicon ester sample can then be calculated based on the standard curve.

[0043] As an example, Figure 1 The NMR F-spectrum is for compound 2 of one embodiment of this application.

[0044] In some embodiments, the difluorophosphate silicon ester includes at least one of compound 1, compound 2, compound 5, compound 12, compound 14, compound 16, and compound 18. Thus, the constructed interfacial film is relatively stable and can further suppress side reactions between the electrolyte and residual alkali on the surface of the positive electrode active material.

[0045] In a second aspect, this application discloses a difluorophosphate silicon ester product, wherein the moisture content of the difluorophosphate silicon ester product in the storage or operating environment is ≤0.15 mg / cm³. 3 Under these conditions, for no more than 150 days, based on the mass of difluorophosphate silicon ester, the content of difluorophosphate is 2000 ppm.

[0046] In some embodiments, the moisture content of the difluorophosphate silicon ester product in the storage or operating environment is ≤0.12 mg / cm³. 3 Under these conditions, for no more than 100 days, based on the mass of difluorophosphate silicon ester, the content of difluorophosphate is 0.05ppm-1500ppm.

[0047] In some embodiments, the difluorophosphate silicon ester product is operated or stored for no more than 150 days at a temperature not exceeding 25 °C, and the content of difluorophosphate is 1200 ppm based on the mass of the difluorophosphate silicon ester.

[0048] In some embodiments, the difluorophosphate silicon ester product is operated or stored for no more than 100 days at a temperature not exceeding 0 °C, with a difluorophosphate content of 1000 ppm based on the mass of the difluorophosphate silicon ester.

[0049] In a third aspect of this application, the application of the aforementioned difluorophosphate silicon ester product in the fields of electrolytes and batteries is proposed.

[0050] In a fourth aspect, this application provides an electrolyte comprising the aforementioned difluorophosphate silicon ester product. Therefore, this electrolyte possesses all the features and advantages of the aforementioned difluorophosphate silicon ester product, which will not be repeated here.

[0051] In some embodiments, the mass fraction of difluorophosphate silicon ester in the electrolyte is 0.05%-5.0%. Therefore, by combining an appropriate amount of difluorophosphate silicon ester with the corresponding difluorophosphate, a synergistic effect can be effectively achieved, jointly improving the high-temperature storage and high-temperature cycling performance of the battery with this electrolyte.

[0052] As an example, the mass fraction of difluorophosphate silicate in the electrolyte can be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0053] In some embodiments, the mass fraction of difluorophosphate silicon ester in the electrolyte is 0.5%-2.5%.

[0054] As an example, the mass fraction of difluorophosphate silicate in the electrolyte can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0055] In a fifth aspect, this application proposes a battery comprising the aforementioned silicon difluorophosphate product or the aforementioned electrolyte. Thus, the battery possesses all the features and advantages of the aforementioned silicon difluorophosphate product and electrolyte, which will not be elaborated further here.

[0056] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between them while allowing ions to pass through.

[0057] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive active material layer includes a positive active material, which is a nickel-cobalt-manganese ternary material. This can further improve the energy density of the battery.

[0058] In some embodiments, the positive electrode active material may include LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.1 Mn 0.1 At least one of O2 can be used to further improve the specific capacity of the positive electrode active material and increase the energy density of the battery.

[0059] The batteries in this application may be in the form of individual battery cells, battery modules, or battery packs.

[0060] In some embodiments, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0061] In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0062] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] Obtaining difluorophosphate silicon ester products Product Example 1 100 g of the compound shown in Formula 1-1 was stored in a 250 mL container with a water content of 0.10 mg / cm³. 3 The silicon-based fluorophosphate compound sample 1 was obtained by storing the compound at a temperature of -10℃ for 90 days.

[0064] Product Examples 2-34 It is basically the same as the product example 1, with the differences shown in Table 1.

[0065] Product Comparison Example 1 Same as Product Example 1, with differences shown in Table 1.

[0066] Table 1

[0067] The test method for the content of difluorophosphate in the above-mentioned difluorophosphate silicon ester products is as follows: Standard curve NMR characterization: A series of quantitative difluorophosphoric acid solutions were transferred to sample vials, and a fixed amount of fluorobenzene was added as an internal standard. The solution was then diluted to 100 mL with dehydrated EMC solvent. After complete dissolution, 500 μL of the solution was added to an NMR tube, followed by the addition of NMR reagent d6-DMSO. After mixing, NMR F-spectrum analysis was performed (Bruker NMR). 19 F-NMR 376MHz standard test).

[0068] Data Analysis: The chemical shift of F in the internal standard fluorobenzene in the F spectrum was qualitatively determined. After determining the chemical shift, peak area integration and normalization were performed. Then, the peak chemical shift of difluorophosphoric acid was assigned, and its peak area was integrated. A standard curve was plotted using the (difluorophosphoric acid / fluorobenzene) peak area ratio against the molar ratio of F content. R 2 ≥0.99.

[0069] Sample testing and analysis: A solid mass of silicon difluorophosphate sample was transferred to an NMR tube, a certain amount of fluorobenzene standard was added, followed by NMR reagent d6-DMSO. After shaking well, NMR F-spectrum analysis was performed (Bruker NMR). 19 (F-NMR 376MHz standard test). Determine the peak position of difluorophosphate in the sample, calculate its peak area and compare it with the fluorobenzene standard to determine the position of the peak area ratio in the working curve. The content of difluorophosphate in the difluorophosphate silicon ester product can then be calculated based on the standard curve.

[0070] Battery manufacturing Example 1 1. Electrolyte preparation: The electrolyte solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 3:6:1. LiPF6 and difluorophosphate silicon ester products (including difluorophosphate silicon ester (using compound 2) and difluorophosphate) are added to the electrolyte solvent. Based on the total mass of the electrolyte, the mass fraction of LiPF6 is 12.5%, and the mass fraction of difluorophosphate silicon ester product is 1%. The mass percentage of difluorophosphate silicon ester product is 500 ppm.

[0071] 2. Preparation of the positive electrode: The positive electrode active material LiNi is prepared... 0.6 Co 0.1 Mn 0.3O2, conductive carbon black (conductive agent), carbon nanotubes (conductive agent), and polyvinylidene fluoride (PVDF) (binder) are mixed evenly in a mass ratio of 95:3:0.5:1.5 and vacuum stirred until the mixture has uniform flowability to obtain a positive electrode slurry. The positive electrode slurry is then evenly coated onto both sides of an aluminum foil, and subsequently dried at 85°C, cold-pressed, trimmed, cut into sheets, slit, and vacuum-dried at 85°C for 12 hours. After welding the tabs, the areal density of the positive electrode active material layer is 25 mg / cm³. 2 The positive electrode sheet.

[0072] 3. Negative Electrode Preparation: Graphite (negative electrode active material), conductive carbon black (conductive agent), sodium carboxymethyl cellulose (thickener), and styrene-butadiene rubber latex (binder) are thoroughly mixed in a mass ratio of 95:1.5:1.5:2 to form a uniform negative electrode slurry. The slurry is coated onto both sides of a copper foil and dried at 85°C. Then, it undergoes cold pressing, edge trimming, cutting, and slitting. Finally, it is dried under vacuum at 85°C for 12 hours. The resulting electrode tabs are then welded to obtain a negative electrode active material with a layer density of 15.0 mg / cm³. 2 The negative electrode sheet.

[0073] 4. Separator: A 9μm thick porous polyethylene polymer film is used as the substrate, and a 2μm thick polyvinylidene fluoride adhesive coating is applied to both sides of the substrate.

[0074] 5. Lithium-ion battery manufacturing: The above-mentioned positive electrode sheet (cut size: 70mm×54mm), separator (cut size: 1900mm×61.5mm), and negative electrode sheet (cut size: 74mm×58mm) are sequentially stacked to form a bare cell with a theoretical capacity of 1400mAh. The bare cell is placed in an outer packaging aluminum foil and vacuum baked at 75°C for 10 hours before being injected with the aforementioned electrolyte. After vacuum sealing, settling, formation, aging, and capacity testing, a stacked lithium-ion battery is obtained.

[0075] For the differences between other embodiments, comparative examples and Embodiment 1, please refer to Table 2.

[0076] Table 2

[0077] Impedance, cycle, and high / low temperature performance tests were performed on the batteries in the aforementioned embodiments and comparative examples. The test methods are as follows, and the test results are shown in Table 3: (1) 25℃ room temperature cycle test: The battery is charged at 25℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. Then the battery is discharged at a constant current of 1.0C to 3.0V. The charge and discharge cycle is repeated for 1000 cycles. The discharge capacity of the 1000th cycle and the 1st cycle are recorded. The capacity retention rate is obtained by dividing the discharge capacity of the 1000th cycle by the discharge capacity of the 1st cycle.

[0078] (2) 45℃ high temperature cycle test: The battery is charged at 45℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. Then the battery is discharged at a constant current of 1.0C to 3.0V. The charge and discharge cycle is repeated for 800 cycles. The discharge capacity of the 800th cycle and the 1st cycle are recorded. The capacity retention rate is obtained by dividing the discharge capacity of the 800th cycle by the discharge capacity of the 1st cycle.

[0079] (3) 30-day storage test at 60℃: The battery was charged at 25℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. Then, the battery was discharged at a constant current of 1.0C to 3.0V. The discharge capacity was recorded as C1. At 25℃, the battery was charged at a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. The battery was then transferred to 60℃ and stored for 30 days. Then, the battery was discharged at a constant current of 1.0C to 3.0V. The discharge capacity was recorded as C2. The capacity retention rate after 30 days of storage at 60℃ = C2 / C1 × 100%.

[0080] (4) High-temperature DCIR test: The battery was charged at 25℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C for 30 minutes, rested for 1 hour, and then discharged at a constant current of 2.0C for 10 seconds. The DCIR of the battery at 50% SOC was calculated and recorded as D1. The battery that had completed the 30-day storage test at 60℃ was charged at 25℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C for 30 minutes, rested for 1 hour, and then discharged at a constant current of 2.0C for 10 seconds. The DCIR of the battery at 50% SOC was calculated and recorded as D2. Battery impedance change rate = D2 / D1 × 100%.

[0081] (5) High-temperature expansion test: The battery was charged at 25℃ with a constant current of 1.0C to 4.45V, and then charged at a constant voltage of 4.45V to the cutoff current of 0.05C. The initial thickness of the battery at this time was measured and recorded as T1. The battery was then stored at 60℃ for 30 days, and the thickness of the battery after 30 days of storage was measured and recorded as T2. Battery expansion rate (%) = (T2-T1) / T1×100%.

[0082] Table 3

[0083] Test results show that when the difluorophosphate content is less than 0.05 ppm, there is not enough difluorophosphate to participate in the solvation structure of lithium ions, which cannot have a good stabilizing effect on the solvation sheath structure and the solvent molecules therein. The promoting effect on the dissociation of lithium ions in the electrolyte is small, which is not conducive to improving the ionic conductivity of the electrolyte. It also cannot promote the dissociation of lithium ions in the solvation sheath structure at the electrode interface and the transport of lithium ions in the interface film. The high-temperature cycle performance and high-temperature storage performance of the battery are both poor.

[0084] When the content of difluorophosphate is 0.05ppm-2000ppm, it can promote the dissociation of lithium ions from the lithium salt ion pair structure in the electrolyte, thereby improving the ionic conductivity of the electrolyte. In addition, difluorophosphate silicon ester preferentially participates in the electrochemical reaction to form the interfacial film, which can promote the dissociation of lithium ions in the solvated sheath structure at the electrode interface and the transport of lithium ions in the interfacial film, thus improving the overall cycle performance and storage performance of the battery. However, when the content of difluorophosphate is too high, the excess difluorophosphate will consume too much lithium salt in the electrolyte to produce lithium difluorophosphate. This is not only detrimental to maintaining the discharge capacity of the battery, but also leads to an excessive amount of inorganic lithium salt components in the interfacial film, resulting in low flexibility and increased thickness. This leads to poor lithium ion conduction performance of the interfacial film and makes the interfacial film easily damaged under high temperature / high voltage conditions. At the same time, it will also have a corrosive effect on the electrode material, exacerbating the dissolution of transition metal ions in the positive electrode active material, resulting in an increase in the interfacial impedance of the positive / negative electrodes.

[0085] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A difluorophosphate silicon ester product, characterized in that, The difluorophosphate silicate has the chemical formula shown in Formula 1: Formula 1 R1, R2, and R3 are each independently selected from any one of hydrogen atoms, fluorine atoms, C1-C4 alkyl groups, C1-C4 fluoroalkyl groups, C2-C4 alkenyl groups, C2-C4 fluoroalkenyl groups, C2-C4 alkynyl groups, C5-C7 cycloalkanes, substituted or unsubstituted phenyl groups, and substituted or unsubstituted benzyl groups. The difluorophosphate silicon ester product contains 0.05ppm-2000ppm of difluorophosphate, which is obtained by hydrolyzing the difluorophosphate silicon ester.

2. The difluorophosphate silicon ester product according to claim 1, characterized in that, The mass percentage of difluorophosphate in the difluorophosphate silicon ester is 1ppm-1500ppm.

3. The difluorophosphate silicon ester product according to claim 1, characterized in that, The difluorophosphate silicate comprises at least one of the following structural formulas: Compound 1 Compound 2 Compound 3 Compound 4 Compound 5 Compound 6 Compound 7 Compound 8 Compound 9 Compound 10 Compound 11 Compound 12 Compound 13 Compound 14 Compound 15 Compound 16 Compound 17 Compound 18 Compound 19 Compound 20 Compound 21 Compound 22.

4. A difluorophosphate silicon ester product, characterized in that, The difluorophosphate silicon ester product has a moisture content of ≤0.15 mg / cm³ in the storage or operating environment. 3 Under the conditions of not exceeding 150 days, the content of difluorophosphate is 2000 ppm based on the mass of the difluorophosphate silicon ester.

5. The difluorophosphate silicon ester product according to claim 4, characterized in that, The difluorophosphate silicon ester product has a moisture content of ≤0.12 mg / cm³ in the storage or operating environment. 3 Under the conditions of not exceeding 100 days, based on the mass of the difluorophosphate silicon ester, the content of the difluorophosphate is 0.05ppm-1500ppm.

6. The difluorophosphate silicon ester product according to claim 4, characterized in that, The difluorophosphate silicon ester product is operated or stored for no more than 150 days at a temperature not exceeding 25 ℃, and the content of difluorophosphate is 1200 ppm based on the mass of the difluorophosphate silicon ester.

7. The difluorophosphate silicon ester product according to claim 4, characterized in that, The difluorophosphate silicon ester product is operated or stored for no more than 100 days at a temperature not exceeding 0 ℃, and the content of difluorophosphate is 1000 ppm based on the mass of the difluorophosphate silicon ester.

8. The application of the difluorophosphate silicon ester product according to any one of claims 1-7 in the field of electrolytes and batteries.

9. An electrolyte, characterized in that, Includes the difluorophosphate silicon ester product as described in any one of claims 1-7.

10. The electrolyte according to claim 9, characterized in that, The mass fraction of the difluorophosphate silicon ester in the electrolyte is 0.05%-5.0%.

11. The electrolyte according to claim 10, characterized in that, The mass fraction of the difluorophosphate silicon ester in the electrolyte is 0.5%-2.5%.

12. A battery, characterized in that, Includes the difluorophosphate silicon ester product according to any one of claims 1-7, or the electrolyte according to any one of claims 9-11.

13. The battery according to claim 12, characterized in that, It also includes a positive electrode sheet, which includes a positive current collector and a positive active material layer located on at least one side of the positive current collector. The positive active material layer includes a positive active material, which includes a nickel-cobalt-manganese ternary material.

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