Preparation method of phosphoric acid cyclic anhydride compound

Abstract

The invention discloses a preparation method of a phosphoric acid cyclic anhydride compound, and belongs to the technical field of battery electrolyte additives, and the preparation method comprises the following steps: reacting a compound as shown in a formula 1 with a chlorination reagent, and controlling the reaction temperature and the reaction time to generate a phosphoric acid cyclic anhydride compound as shown in a formula 2; carrying out post-treatment on the reaction liquid to obtain a phosphoric acid cyclic anhydride compound; according to the invention, aromatic ring phosphonic acid with an adjustable structure is used as a starting raw material, and a series of products with a core skeleton constructed by a rigid benzene ring and phosphoric acid cyclic anhydride are efficiently constructed through an optimized reaction path, so that the method has the advantages of mild conditions and high substrate universality; the limitation that an existing synthesis technology is poor in selectivity on phosphoric acid cyclic anhydride of a complex structure and difficult to purify is fundamentally overcome, and a more reliable technical approach is provided for molecular design and controllable synthesis of a high-performance electrolyte additive.

Description

Technical Field

[0001] This invention belongs to the field of battery electrolyte additive technology, and particularly relates to a method for preparing a phosphate cyclic anhydride compound. Background Technology

[0002] With the rapid development of new energy vehicles and the energy storage industry, the market has placed unprecedented demands on the energy density, cycle life, and long-term stability at high temperatures of lithium-ion batteries. Electrolyte additives are key materials for regulating the electrode-electrolyte interface and help improve the overall performance of batteries. Among the many types of electrolyte additives, organophosphorus compounds, especially cyclic phosphate anhydrides, show outstanding application potential due to their unique molecular structure and functional characteristics.

[0003] Recent studies have shown that certain cyclic phosphate anhydrides, such as propyl cyclic phosphate anhydride, can serve as effective electrolyte additives for lithium-ion batteries, participating in the construction of stable solid-state electrolyte interfacial films, extending battery cycle life, and improving electrochemical performance. These effects are attributed to the high reactivity of their cyclic anhydride structure, allowing them to preferentially decompose the electrolyte at the electrode surface. Other studies have found that mixed anhydride additives containing both phosphorus and sulfur can form heteroatom-rich interfacial films, thereby more effectively improving battery cycle stability. Therefore, cyclic phosphate anhydrides and their derivatives hold an important position as high-performance electrolyte additives.

[0004] However, existing preparation methods exhibit significant limitations when dealing with complex cyclic phosphate anhydrides, particularly polycyclic phosphate anhydrides with multiple electrochemical functions. For example, patent CN120136924A provides a simple synthetic route for preparing alkylcyclic phosphate anhydrides, using the reaction of trifluoroacetic anhydride with non-chlorinated alkyl phosphates. However, this reaction has only been validated for application to simple straight-chain alkyl phosphates. When the substrate becomes a structurally complex aromatic phosphonic acid with various functional groups attached to the aromatic ring, this method is not directly applicable in terms of the suitability of the reaction reagents, the effectiveness of the reaction conditions, or the distillation purification techniques that depend on boiling point differences.

[0005] Therefore, developing a universally applicable and efficient method for constructing polycyclic aromatic phosphate anhydrides is crucial for promoting the industrialization and application of such high-performance additives. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical shortcomings of existing technologies for synthesizing cyclic phosphate anhydrides, especially derivatives containing aromatic ring structures, which suffer from poor universality and difficulty in efficiently constructing complex functional molecular structures. This invention provides a method for preparing cyclic phosphate anhydrides, using structurally tunable aromatic phosphonic acids as starting materials to efficiently construct compounds with a triphenylcyclic cyclic phosphate anhydride core skeleton through a mild and controllable reaction.

[0007] The technical solution adopted in this invention is a method for preparing a cyclic phosphate anhydride compound. The key lies in reacting the compound shown in Formula 1 with a chlorinating reagent, controlling the reaction temperature and time to generate the cyclic phosphate anhydride compound shown in Formula 2; and then post-treating the reaction solution to obtain the aforementioned cyclic phosphate anhydride compound. Formula 1, Equation 2, The synthesis route is as follows:

[0008] In Formula 1 or Formula 2, R is selected from at least one of hydrogen, halogen, cyano, nitro, amino, alkyl with 1 to 10 substituted or unsubstituted carbon atoms, substituted or unsubstituted phenyl, substituted or unsubstituted amide; the substituents are selected from at least one of halogen, cyano, nitro, amino and amide.

[0009] Furthermore, R is selected from hydrogen, fluorine, chlorine, alkyl, phenyl, biphenyl and formamido groups with 1 to 5 substituted or unsubstituted carbon atoms, and the substituents are selected from at least one of fluorine, cyano, nitro and amino.

[0010] Furthermore, the reaction temperature is 40℃~120℃.

[0011] Furthermore, the reaction time is 18h to 30h.

[0012] Preferably, the molar ratio of the compound shown in Formula 1 to the chlorination reagent is 1:(0.5 to 2.0).

[0013] Preferably, the molar ratio of the compound shown in Formula 1 to the chlorination reagent is 1:(1.1 to 1.6).

[0014] Specifically, the chlorinating agent mentioned above is selected from at least one of thionyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, and phenylphosphonic dichloride.

[0015] Furthermore, the above reaction can be carried out in a reaction solvent; when the chlorinating reagent is a liquid substance, no reaction solvent needs to be added.

[0016] Furthermore, the reaction solvent is selected from at least one of chlorobenzene, 1,2-dichlorobenzene, tetrahydrofuran, dichloromethane, and toluene.

[0017] Furthermore, the above post-processing specifically involves extracting, drying, and concentrating the reaction solution to obtain a crude product, and then purifying the crude product to obtain the phosphate cyclic anhydride compound product shown in Formula 2.

[0018] Compared with the prior art, the present invention has the following advantages: First, this invention provides a universal, efficient, and precisely controllable method for preparing cyclic phosphate anhydrides. Using structurally tunable aromatic phosphonic acids as starting materials, this invention optimizes the selection of specific chlorination reagents and reaction media, efficiently and selectively constructing the core framework of the cyclic phosphate anhydride compound consisting of a rigid benzene ring and the cyclic phosphate anhydride under mild reaction conditions. This invention exhibits excellent substrate universality, applicable to starting materials containing various functional groups such as electron-withdrawing, electron-donating, and sterically hindered groups. Most importantly, the solvent-free design of this invention not only simplifies the process and reduces waste but has also proven to be an important and feasible technical route for obtaining high yields and high purity.

[0019] Secondly, the series of phosphate cyclic anhydride compounds prepared in this invention possess excellent and customizable electrochemical functions inherent in their molecular structure. The core framework, composed of a rigid benzene ring and phosphate cyclic anhydride, combines structural stability with specific reactivity, enabling it to participate in the construction of a robust and ion-conducting protective film at the electrode interface. Through flexible design of substituents on the benzene ring, the electronic properties of the additive molecules can be precisely controlled, thereby directionally enhancing their specific performance in areas such as improving interfacial ion conduction, enhancing high-temperature interfacial stability, or optimizing high-voltage cycle life.

[0020] Third, the preparation process and product quality indicators of this invention fully meet the stringent requirements for high-end electrolyte additives, demonstrating outstanding potential for industrial transformation. The process route of this invention is stable and reliable, and the key quality indicators of the resulting series of products, such as purity, trace moisture control, and yield, all meet or exceed the standards for high-performance electrolyte additives. Therefore, this invention not only overcomes the technical challenges of efficient and high-quality synthesis of complex aromatic cyclic phosphate anhydrides, but also provides an important material foundation for the development of next-generation battery technology.

[0021] In summary, this invention not only successfully developed an efficient preparation process for high-performance cyclic anhydride phosphate additives, but also achieved precise and long-term control of battery interface chemistry through a strategy combining core framework design and customized functional groups, providing an important material and technological foundation for the development of advanced lithium-ion battery systems with high energy density and high safety. Attached Figure Description

[0022] Figure 1This is the ¹H NMR spectrum of sample 1 of the product of this invention. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] Unless otherwise specified in the examples, the procedures can be followed according to conventional conditions; unless the manufacturers of the reagents or instruments used are specified, they are all conventional products that can be purchased commercially.

[0029] The vacuum distillation method in various embodiments of the present invention involves redissolving the crude product, washing it with water, drying it, concentrating it to remove the solvent, performing vacuum distillation, collecting the fraction with the corresponding boiling range, and obtaining the product.

[0030] In various embodiments of the present invention, compounds with different structures based on triphenylcyclic phosphate anhydrides were prepared using different starting materials. The names and structures of the starting materials used in each embodiment are shown in Table 1.

[0031] Table 1: Summary Table of Starting Material Names and Structures Used in Examples

[0032] Example 1 The preparation of triphenylcyclic phosphate anhydride using compound 1 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.1 mol of phenylphosphonic acid and 0.13 mol of thionyl chloride to 100 mL of dichloromethane, mix at 350 r / min, control the reaction temperature at 40 °C, react for 24 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 1, with the structural formula shown in Formula 3.

[0033] Formula 3 Example 2 The preparation of triphenylcyclic phosphate anhydride using compound 1 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.2 mol of phenylphosphonic acid and 0.2 mol of thionyl chloride to 180 mL of dichloromethane, mix at 500 r / min, control the reaction temperature at 40 °C, react for 24 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract twice with diethyl ether solvent, allow to stand and separate, combine the organic phases, wash the organic phase with water, dry with anhydrous sodium sulfate, and concentrate to obtain crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 2, with the structural formula shown in Formula 3.

[0034] Example 3 The preparation of triphenylcyclic phosphate anhydride using compound 1 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.15 mol of phenylphosphonic acid and 0.24 mol of thionyl chloride to 150 mL of dichloromethane, mix at 200 r / min, control the reaction temperature at 40 °C, react for 24 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 3, with the structural formula shown in Formula 3.

[0035] Example 4 The preparation of triphenylcyclic phosphate anhydride using compound 1 in Table 1 as the starting material is as follows: S1. Under inert gas protection, without using any reaction solvent, 0.1 mol of phenylphosphonic acid and 0.13 mol of thionyl chloride are mixed at a speed of 350 r / min, the reaction temperature is controlled at 40℃, and the reaction is carried out for 24 h. The reaction solution is cooled to room temperature and the reaction is quenched with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 4, with the structural formula shown in Formula 3.

[0036] Example 5 The preparation of triphenylcyclic phosphate anhydride using compound 1 in Table 1 as the starting material is as follows: S1. Under inert gas protection, without using any reaction solvent, 0.1 mol of phenylphosphonic acid and 0.13 mol of phosphorus oxychloride were mixed at a speed of 350 r / min, the reaction temperature was controlled at 40℃, and the reaction was carried out for 24 h. The reaction solution was cooled to room temperature and the reaction was quenched with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 5, with the structural formula shown in Formula 3.

[0037] Example 6 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 2 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.2 mol of (4-fluorophenyl)phosphonic acid and 0.1 mol of phenylphosphonic dichloride to 200 mL of toluene, mix at 350 r / min, control the reaction temperature at 60 °C, react for 30 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with diethyl ether solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 6, with the structural formula shown in Formula 4.

[0038] Formula 4 Example 7 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 3 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.1 mol of (2-cyanophenyl)phosphonic acid and 0.13 mol of phosphorus trichloride to 100 mL of tetrahydrofuran, mix at 350 r / min, control the reaction temperature at 60 °C, react for 22 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 7, with the structural formula shown in Formula 5.

[0039] Formula 5 Example 8 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 4 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.1 mol of (4-nitrophenyl)phosphonic acid and 0.13 mol of phosphorus oxychloride to 100 mL of 1,2-dichlorobenzene, mix at 350 r / min, control the reaction temperature at 80℃, react for 20 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 8, with the structural formula shown in Formula 6.

[0040] Formula 6 Example 9 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 5 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.1 mol of (4-aminophenyl)phosphonic acid and 0.13 mol of phosphorus pentachloride to 100 mL of chlorobenzene, mix at 350 r / min, control the reaction temperature at 120℃, react for 28 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 9, with the structural formula shown in Formula 7.

[0041] Formula 7 Example 10 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 6 in Table 1 as the starting material is as follows: S1. Under inert gas protection, without using any reaction solvent, 0.1 mol of (4-tert-butylphenyl)phosphonic acid and 0.2 mol of a compound chlorination reagent consisting of phenylphosphonic dichloride and phosphorus trichloride were mixed at a rotation speed of 350 r / min, the reaction temperature was controlled at 90℃, and the reaction was carried out for 22 h. The reaction solution was then cooled to room temperature and the reaction was quenched in ice water to obtain the reaction solution. The molar ratio of phenylphosphonic dichloride to phosphorus trichloride in the compound chlorination reagent was 1:0.5. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 10, with the structural formula shown in Formula 8.

[0042] Formula 8 Example 11 The preparation of compounds with a triphenylcyclic phosphate anhydride as the basic skeleton using compound 7 in Table 1 as the starting material is as follows: S1. Under inert gas protection, add 0.1 mol of (4-methylphenyl)phosphonic acid and 0.13 mol of thionyl chloride to 100 mL of toluene, mix at 350 r / min, control the reaction temperature at 105 °C, react for 18 h, cool the reaction solution to room temperature, and quench the reaction with ice water to obtain the reaction solution. S2. After quenching the reaction solution with ice water, extract it three times with ethyl acetate solvent, let it stand and separate the liquids, combine the organic phases, wash the organic phases with water, dry them with anhydrous sodium sulfate, and concentrate them to obtain the crude product. S3. The crude product was purified by vacuum distillation to obtain the above-mentioned phosphate cyclic anhydride compound, denoted as product 11, with the structural formula shown in Formula 9.

[0043] Formula 9 Example 12 Using compound 8 from Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that compound 1 was replaced by an equal amount of compound 8. The above-mentioned phosphate anhydride compound was obtained and denoted as product 12. Its structural formula is shown in Formula 10.

[0044] Formula 10 Example 13 Using compound 9 from Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that compound 1 was replaced with an equal amount of compound 9 to obtain the above-mentioned phosphate anhydride compound, denoted as product 13, with the structural formula shown in Formula 11.

[0045] Formula 11 Example 14 Using compound 10 from Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that compound 1 was replaced by an equal amount of compound 10 to obtain the above-mentioned phosphate anhydride compound, denoted as product 14, with the structural formula shown in Formula 12.

[0046] Formula 12 Example 15 Using compound 11 in Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that compound 1 was replaced by an equal amount of compound 11 to obtain the above-mentioned phosphate anhydride compound, which was denoted as product 15, and its structural formula is shown in Formula 13.

[0047] Formula 13 Comparative Example 1 Using compound 1 in Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that oxalyl chloride was used in place of thionyl chloride in an equal amount to prepare the above-mentioned phosphate anhydride compound, which was designated as reference standard 1.

[0048] Comparative Example 2 Using compound 1 in Table 1 as the starting material, a compound with a triphenylcyclic cyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 4, except that an equal amount of sulfonyl chloride was used instead of thionyl chloride to prepare the above-mentioned cyclic phosphate anhydride compound, which was designated as reference standard 2.

[0049] Comparative Example 3 Using compound 1 in Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 1, except that an equal volume of dimethyl sulfoxide was used instead of dichloromethane as the reaction solvent. The above-mentioned phosphate anhydride compound was prepared and was designated as reference standard 3.

[0050] Comparative Example 4 Using compound 1 in Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 1, except that an equal volume of N,N-dimethylformamide was used instead of dichloromethane as the reaction solvent. The above-mentioned phosphate anhydride compound was prepared and was designated as reference standard 4.

[0051] Comparative Example 5 Using compound 1 in Table 1 as the starting material, a compound with a triphenylcyclic phosphate anhydride as the basic skeleton was prepared. The specific process was the same as in Example 1, except that an equal volume of n-hexane was used instead of dichloromethane as the reaction solvent. The above-mentioned phosphate anhydride compound was prepared and was designated as reference standard 5.

[0052] Analysis and Testing The purity of the products prepared in each embodiment was analyzed using high performance gas chromatography. After removing volatile components by rotary evaporation at room temperature, the moisture content of the products was determined, and the yield was calculated. The results are shown in Table 2.

[0053] Product yield = Actual weight of the product obtained (g) / Theoretical yield (g) calculated using the starting material amount shown in Formula 1 × 100%.

[0054] The structure of the product samples was confirmed using nuclear magnetic resonance (NMR) analysis, demonstrating that the structure of the final product obtained from each test conformed to the target structural characteristics. The test spectrum for product 1 is shown below. Figure 1 .

[0055] Table 2: Summary Table of Test Results for Product and Reference Samples

[0056] As shown in Table 2, the cyclic phosphate anhydride series compounds prepared by this invention all have a final product purity of 99.1% or higher, with some products reaching a high purity level of over 99.7%. The moisture content of all products is strictly controlled within an extremely low range of less than 25 ppm. This indicates that the preparation process of this invention has high universality and controllability for different starting materials, and the resulting series of cyclic phosphate anhydride products fully meet the stringent quality requirements for ultra-high purity and trace moisture in high-performance electrolyte additives.

[0057] Using starting materials with different structures as raw materials, the yields of the products prepared by this invention can all reach over 92%. The process route using thionyl chloride as the chlorinating agent and without the use of solvents is particularly outstanding: Example 4 achieved a 100% yield; under the same optimized conditions, Examples 12 to 15, using starting materials with different substituents, also maintained extremely high yields of 99.1% to 99.8%. This proves that the solvent-free process of this invention is not only applicable to basic substrates but also has excellent applicability to various substituted aromatic phosphonic acids, generally achieving high yields. In contrast, although Example 5 also uses a solvent-free method, due to the use of a different chlorinating agent, its yield of 96.2%, while still excellent, is lower than that of the thionyl chloride system, further confirming the unique advantages of thionyl chloride in this solvent-free synthetic route.

[0058] Of particular note is that reference standard 1, which uses oxalyl chloride instead of thionyl chloride, resulted in an excessively vigorous reaction and poor selectivity, leading to increased side reactions, a product purity of only 92.5%, a significantly reduced yield of 65.2%, and an increased moisture content. Reference standard 2, which uses sulfonyl chloride, had relatively insufficient chlorination capacity, making the reaction difficult to complete and easily introducing sulfur impurities. Although the product purity reached 95.8%, the yield was only 78.6%.

[0059] Reference standard 3 used dimethyl sulfoxide as a solvent, which not only underwent side reactions with the chlorinating reagent, but also, due to the extremely high boiling point of the solvent, was difficult to completely remove from the product, resulting in a product purity of only 90.1%, a water content as high as 78 ppm, and a yield as low as 41.3%. Reference standard 4 used N,N-dimethylformamide as the reaction solvent, further reducing the product purity to 88.7%, with severely excessive water content and a yield of only 38.5%. Reference standard 5 used chemically inert n-hexane as the reaction solvent, but its poor solubility and insufficient contact with reactants led to low reaction efficiency, with a yield of only 71.4%.

[0060] It is evident that the specific reaction system constructed in this invention, namely the selection of chlorination reagent, solvent, and solvent-free conditions, exhibits a synergistic effect with the structural characteristics of the target product. This system not only efficiently and selectively completes the crucial synthesis from aromatic phosphonic acids to tricyclic anhydrides, but its reaction process is also highly compatible with subsequent purification processes. This simultaneously achieves multiple stringent requirements, including ultra-high product purity, trace moisture control, and near-quantitative yield, solving the long-standing technical challenge of efficiently and effectively preparing complex aromatic phosphonic anhydrides.

[0061] Application Examples To verify the practical application effect of the series of phosphate cyclic anhydride compounds of this invention as electrolyte additives, nine structurally representative products were selected for systematic evaluation according to Table 3.

[0062] Different product samples with different mass concentrations were added to the same reference electrolyte at a concentration of 1% each, and were designated as application samples P-1 to P-9. The electrolyte with 1% tripropyl cyclic anhydride added was application comparison 1; the electrolyte with 1% triphenyl phosphate added was application comparison 2; the electrolyte with a total mass concentration of 1% tripropyl cyclic anhydride and triphenyl phosphate (in a 1:1 molar ratio) was application comparison 3; and the electrolyte without any additives was used as a blank comparison.

[0063] These electrolytes were used to fabricate a lithium battery with a rated capacity of 1000mAh for testing. The battery system consisted of a ternary cathode and a graphite anode.

[0064] Table 3: Sample Numbers and Dosages for Application Examples

[0065] (I) Interface dynamics and rate performance testing This section of the test aims to quantitatively evaluate the impact of different additives on the battery's internal interface impedance and fast charge / discharge capability.

[0066] 1. DC internal resistance (DCR) test: The battery was charged at a constant current rate of 1C to 4.5V in an environment of 25℃±2℃, then switched to constant voltage charging until the current dropped to 0.05C. After standing for 5 minutes, the DC internal resistance (DCR) was tested using the HPPC method at 50% state of charge (SOC). The results are shown in Table 4.

[0067] 2. Discharge performance test at different rates: The battery was charged at 25℃±2℃ with a constant current of 1C to 4.5V, and then switched to constant voltage charging until the current dropped to 0.05C. Subsequently, it was discharged at constant current of 0.2C and 3C to 3.0V respectively. The retention rate of the 3C rate discharge capacity relative to the 0.2C rate discharge capacity was calculated to evaluate the effect of additives on the improvement of the battery's high-rate discharge capability. The higher the retention rate, the better the ion transport kinetics at high rates.

[0068] (II) High Temperature and High Voltage Stability Test This section of the test aims to evaluate the additive's ability to maintain long-term stability of the battery interface and capacity under extreme operating conditions.

[0069] 1. High-temperature storage test: Charge the battery to 4.5V at a 1C rate and store it in a 60℃ environment for 7 days. Cool the battery to 25℃, discharge it to 3.0V at a 1C rate, and record the recovered capacity; then charge it to 4.5V at a 1C rate and record the charging capacity. The results are shown in Table 4.

[0070] 2. High-temperature cycle performance test: The battery was placed in an environment of 60℃±2℃ and subjected to a cycle test of 1C constant current charging to 4.5V / 1C constant current discharging to 3.0V. The capacity retention rate after 100 cycles was recorded. The results are shown in Table 4.

[0071] Table 4: Summary Table of Application Test Results

[0072] As shown in Table 4, the triphenylcyclic phosphate anhydride series additives of this invention exhibit excellent technical effects in improving the interfacial conductivity, high-temperature storage stability, and long cycle life of the battery. Overall, all samples of this invention demonstrate excellent high-temperature capacity retention and high power output capabilities, with a capacity recovery rate exceeding 90% after high-temperature storage and a 3C high-rate discharge capacity retention rate exceeding 82%. It is evident that all products used in this invention can effectively construct a stable and low-impedance electrode interface protective layer under extreme electrochemical environments of high voltage and high temperature.

[0073] Among them, application samples P-2 and P-8 exhibited excellent interfacial ion conduction kinetics, with the lowest DC internal resistance and a capacity retention rate of over 92% at 3C high-rate discharge. Application sample P-3 achieved the highest capacity recovery rate and the smallest DCR increase after high-temperature storage, demonstrating exceptional thermal interface stability. Application sample P-4 achieved high oxidation stability, exhibiting a capacity retention rate of 88.5% after 100 cycles under extreme conditions of 60℃ / 4.5V, demonstrating outstanding performance in high-voltage cathode protection. Application sample P-5 showed high overall advantages, with balanced and excellent performance across various indicators. In contrast, application sample P-6, containing a sterically hindered tert-butyl group, had the highest interfacial impedance, reflecting the adverse effect of steric hindrance on the density of the interfacial film. Application samples P-7 and P-9, containing electron-donating alkyl and alkoxy groups, showed more significant interfacial degradation after high-temperature storage and relatively lower cycle retention rates, indicating that electron-donating substituents may be unstable under high-pressure and high-temperature systems. However, even so, their performance still surpassed that of the other application samples.

[0074] In contrast, traditional additive systems fully expose their structural limitations. While Comparison 1 offers some basic protection, its capacity recovery rate after high-temperature storage is low, and its interface deteriorates severely, resulting in insufficient overall stability. More significantly, Comparison 2 exhibits high internal resistance, low cycle retention, and a substantial increase in DCR and significant capacity loss after high-temperature storage in a series of stringent tests, including high-temperature storage and cycling. This demonstrates that without the key bridging structure of phosphate cyclic anhydride, it is difficult to construct a robust and ion-conducting effective protective layer at the electrode interface. Of particular concern is Comparison 3, as a physically compounded system, whose long-term cycling stability is even worse than that of a single component. This indicates that different additive components may have unpredictable adverse interactions or competitive reactions in the electrolyte, leading to deterioration of the interfacial film performance. Clearly, simple physical mixing not only fails to achieve functional synergy but may also introduce new failure risks.

[0075] In summary, the series of triphenylcyclic phosphate anhydride compounds prepared by this invention, through the synergistic design of the core framework constructed by the rigid benzene ring and phosphate anhydride and the customizable functional groups, not only achieve comprehensive performance superiority over traditional structural additives, but also endow the products with specific performance peaks through substituent regulation. This provides an innovative, reliable and customizable material solution for solving the interface failure problem of lithium-ion batteries under high voltage and high temperature conditions.

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a cyclic phosphate anhydride compound, characterized in that, The compound shown in Formula 1 is reacted with a chlorinating reagent, and the reaction temperature and time are controlled to generate the phosphate cyclic anhydride compound shown in Formula 2. The reaction solution is then post-treated to obtain the phosphate cyclic anhydride compound. Formula 1, Equation 2, In Formula 1 or Formula 2, R is selected from at least one of hydrogen, halogen, cyano, nitro, amino, alkyl with 1 to 10 substituted or unsubstituted carbon atoms, alkoxy with 1 to 10 substituted or unsubstituted carbon atoms, phenyl with substituted or unsubstituted carbon atoms, and amide with substituted or unsubstituted carbon atoms; the substituted substituent is selected from at least one of halogen, cyano, nitro, and amide.

2. The preparation method according to claim 1, characterized in that, R is selected from one of hydrogen, fluorine, chlorine, alkyl with 1 to 5 substituted or unsubstituted carbon atoms, alkoxy with 1 to 5 substituted or unsubstituted carbon atoms, phenyl, biphenyl and formamido, wherein the substituted substituent is selected from at least one of fluorine, cyano, nitro and amide.

3. The preparation method according to claim 1, characterized in that, The reaction temperature is 40℃~120℃.

4. The preparation method according to claim 1, characterized in that, The reaction time is 18h to 30h.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the compound shown in Formula 1 to the chlorination reagent is 1:(0.5 to 2.0).

6. The preparation method according to claim 5, characterized in that, The molar ratio of the compound shown in Formula 1 to the chlorination reagent is 1:(1.1 to 1.6).

7. The preparation method according to claim 1, characterized in that, The chlorinating agent is selected from at least one of thionyl chloride, phosphorus oxychloride, phosphorus trichloride, phosphorus pentachloride, and phenylphosphonic dichloride.

8. The preparation method according to claim 1, characterized in that, The reaction can be carried out in a reaction solvent.

9. The preparation method according to claim 8, characterized in that, The reaction solvent is selected from at least one of chlorobenzene, 1,2-dichlorobenzene, tetrahydrofuran, dichloromethane, and toluene.

10. The preparation method according to claim 1, characterized in that, The post-processing specifically involves extracting, drying, and concentrating the reaction solution to obtain a crude product, and then purifying the crude product to obtain the phosphate cyclic anhydride compound product shown in Formula 2.

Images