Phosphorus-oxygen-based additive, preparation method thereof, electrolyte and lithium battery

Abstract

The invention provides a phosphorus-oxygen-based additive, a preparation method of the phosphorus-oxygen-based additive, an electrolyte and a lithium battery. The structural formula of the phosphorus-oxygen-based additive is shown in the following general formula (I): (I), X1 is cyano, halogen atoms and C1-C8 alkyl and alkoxy substituted by halogen atoms, alkenyl and alkynyl; x2 has a structure as shown in a general formula (II) in the specification; wherein Y is C, N or O, and R1, R2 and R3 can be independently selected from halogen atoms, C1-C8 alkoxy substituted or unsubstituted by halogen atoms, alkyl, alkenyl, alkynyl or aryl respectively; and X3 is a cyano group, a halogen atom or X2. The phosphorus-oxygen-based additive can solve the problems that high-working-voltage (such as over 4.3 V) interface side reaction is violent and high-load positive electrode lithium ion conduction is limited, and the structural stability and the electrochemical performance of the battery under the high-voltage condition are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to phosphorus-oxygenated additives and their preparation methods, electrolytes, and lithium batteries. Background Technology

[0002] Achieving high energy density has always been a key goal for the development of next-generation energy storage systems and electric vehicles. This demand has driven the development of a series of high-voltage cathode materials such as LiCoO2 and LiNi. x Co y Mn1 x-y O2, LiNi 0.5 Mn 1.5 The development of O4, lithium-rich manganese layered oxides, and other similar battery systems has been undertaken. However, under high-voltage operating conditions, these battery systems face significant application limitations. On the one hand, due to insufficient interfacial passivation stability, severe side reactions occur between the electrolyte and the catalytic surface of the delithiated cathode, thereby exacerbating electrolyte consumption and cathode transition metal dissolution. On the other hand, the traditional cathode-electrolyte interface layer (CEI) formed by the continuous decomposition of the electrolyte is rich in organic components, resulting in high lithium-ion diffusion resistance and hindering the diffusion of Li-ion. + Effective transport within the electrode. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one object of this invention is to provide a phosphorooxylated additive that, when applied to the electrolyte of a lithium battery, can effectively improve the structural stability and electrochemical performance of the battery under high-voltage conditions.

[0004] In one aspect of the invention, a phosphorooxylated additive is provided. According to an embodiment of the invention, the phosphorooxylated additive has the following general formula (I): (I), Wherein, X1 is a cyano group, a halogen atom, or a C1-C8 alkyl or alkoxy group substituted with a halogen atom, an alkenyl group, or an alkynyl group; X2 has the structure of the following general formula (II): (II); Wherein, Y is C, N or O, R1, R2 and R3 can be independently selected from halogen atoms, C1-C8 alkoxy, alkyl, alkenyl, alkynyl or aryl groups substituted or unsubstituted by halogen atoms; X3 is cyano, halogen atom or X2.

[0005] The phosphorooxyl additive of this invention possesses a high HOMO (highest occupied molecular orbital) energy level, readily losing electrons during cycling. It preferentially decomposes on the positive electrode surface to form a high-voltage resistant interface film containing P, O, and Si, thereby improving the stability of electrode interface passivation, reducing side reactions, and significantly decreasing electrolyte consumption and the dissolution of positive electrode transition metals. Furthermore, the phosphorooxyl additive can decompose on the positive electrode surface to generate Li3PO4, which has high lithium-ion conductivity, effectively reducing interfacial impedance and charge transfer resistance, thus improving the battery's electrochemical performance. Further, the silicon-based groups in the phosphorooxyl additive can act as acid-binding agents to remove trace amounts of water and HF from the electrolyte, forming a flexible interface rich in Si-O groups. This effectively buffers the volume expansion caused by accumulated lattice stress in the positive electrode, contributing to the formation of a high-voltage resistant lithium battery. Therefore, this phosphorooxyl additive can solve the problems of severe interfacial side reactions and limited lithium-ion conductivity in high-load positive electrodes at high operating voltages (e.g., above 4.3V), effectively improving the structural stability and electrochemical performance of the battery under high-voltage conditions.

[0006] According to embodiments of the present invention, the phosphorooxylated additive may be at least one of the following structural formulas: .

[0007] In another aspect of the present invention, a method for preparing the aforementioned phosphorooxylated additive is provided. According to an embodiment of the present invention, the method for preparing the phosphorooxylated additive includes: reacting a phosphate and a silane in a first non-aqueous solvent at a predetermined temperature to obtain a mixed product; adding a second non-aqueous solvent to the mixed product and extracting to obtain the phosphorooxylated additive. Therefore, the above preparation method is simple, has a good yield, is easy to implement, and is suitable for industrial mass production.

[0008] According to embodiments of the present invention, in the method for preparing a phosphorooxylated additive, at least one of the following conditions is met: when the phosphorooxylated additive contains a single silane group, the molar ratio of the phosphate to the silane is 1:1 to 1:1.1; when the phosphorooxylated additive contains two silane groups, the molar ratio of the phosphate to the silane is 1:2 to 1:2.7; the predetermined temperature is -20 ℃ to 60 ℃, and the reaction time is 2 to 12 h.

[0009] In another aspect, the present invention provides an electrolyte for a lithium battery. According to an embodiment of the present invention, the electrolyte comprises a lithium salt, an organic solvent, and the aforementioned phosphorooxygenated additive. Thus, the phosphorooxygenated additive preferentially decomposes on the positive electrode surface of the battery to form a high-voltage resistant interface film containing P, O, and Si, thereby helping to improve the stability of electrode interface passivation, reduce the occurrence of side reactions, significantly reduce electrolyte consumption, and reduce the dissolution of positive electrode transition metals. Moreover, during the decomposition of the phosphorooxygenated additive on the positive electrode surface, Li3PO4 can be derived. Li3PO4 has high lithium-ion conductivity, which can effectively reduce interfacial impedance and charge transfer resistance, thereby improving the electrochemical performance of the battery. Furthermore, the silicon-based groups in the phosphorooxygenated additive can act as acid-binding agents to remove trace water and HF from the electrolyte and form a flexible interface rich in Si-O groups, which can effectively buffer the volume expansion caused by the accumulation of positive electrode lattice stress, thereby contributing to the obtaining of a high-voltage resistant lithium battery. Therefore, electrolytes with this composition can solve the problems of severe interfacial side reactions and limited lithium-ion conduction in high-load cathodes at high operating voltages (such as above 4.3V), effectively improving the structural stability and electrochemical performance of batteries under high voltage conditions.

[0010] According to an embodiment of the present invention, the mass fraction of the phosphorooxygenated additive is 0.5% to 5.0% based on the total weight of the lithium battery electrolyte.

[0011] According to embodiments of the present invention, the concentration of the lithium salt is 0.5~2 mol / L, and / or the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalateborate, and lithium difluorooxalateborate.

[0012] According to an embodiment of the present invention, the electrolyte further includes a film-forming agent, which includes at least one selected from lithium nitrate, lithium perchlorate, lithium sulfate, lithium difluorophosphate and lithium carbonate, and / or the concentration of the film-forming agent is 0.1~0.5 mol / L.

[0013] According to embodiments of the present invention, the organic solvent includes at least one of chain carbonate solvents, cyclic carbonate solvents, and carboxylic acid ester solvents; the chain carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl trifluoroethyl carbonate; the cyclic carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; and the carboxylic acid ester solvent includes at least one of propyl acetate, ethyl acetate, and propyl propionate.

[0014] In another aspect, the present invention provides a lithium battery. According to an embodiment of the invention, the lithium battery includes the electrolyte described above. Therefore, the lithium battery exhibits good structural stability and electrochemical performance under high voltage conditions. Those skilled in the art will understand that the lithium battery possesses all the features and advantages of the phosphorus-oxygenated additives or electrolytes described above, which will not be elaborated further here.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 These are contact angle test diagrams of the electrolyte to the positive electrode in Example 5 and Comparative Example 1.

[0017] Figure 2 These are the electrochemical impedance spectra of the test batteries corresponding to Example 5 and Comparative Example 1 after 100 cycles.

[0018] Figure 3 The graph shows the cycle performance of the test batteries corresponding to Example 5 and Comparative Example 1 at a 2C charge / discharge rate. Detailed Implementation

[0019] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. 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 the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0020] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0022] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] In one aspect of the invention, a phosphorooxylated additive is provided. According to an embodiment of the invention, the phosphorooxylated additive has the following general formula (I): (I), Wherein, X1 is a cyano group, a halogen atom, or a C1-C8 alkyl or alkoxy group substituted with a halogen atom, an alkenyl group, or an alkynyl group; X2 has the structure of the following general formula (II): (II); Wherein, Y is C, N or O, R1, R2 and R3 can be independently selected from halogen atoms, C1-C8 alkoxy, alkyl, alkenyl, alkynyl or aryl groups substituted or unsubstituted by halogen atoms; X3 is cyano, halogen atom or X2.

[0024] The phosphorooxyl additive of this invention possesses a high HOMO (highest occupied molecular orbital) energy level, readily losing electrons during cycling. It preferentially decomposes on the positive electrode surface to form a high-voltage resistant interface film containing P, O, and Si, thereby improving the stability of electrode interface passivation, reducing side reactions, and significantly decreasing electrolyte consumption and the dissolution of positive electrode transition metals. Furthermore, the phosphorooxyl additive can decompose on the positive electrode surface to generate Li3PO4, which has high lithium-ion conductivity, effectively reducing interfacial impedance and charge transfer resistance, thus improving the battery's electrochemical performance. Further, the silicon-based groups in the phosphorooxyl additive can act as acid-binding agents to remove trace amounts of water and HF from the electrolyte, forming a flexible interface rich in Si-O groups. This effectively buffers the volume expansion caused by accumulated lattice stress in the positive electrode, contributing to the formation of a high-voltage resistant lithium battery. Therefore, this phosphorooxyl additive can solve the problems of severe interfacial side reactions and limited lithium-ion conductivity in high-load positive electrodes at high operating voltages (e.g., above 4.3V), effectively improving the structural stability and electrochemical performance of the battery under high-voltage conditions.

[0025] According to embodiments of the present invention, the phosphorooxylated additive may be at least one of the following structural formulas: The aforementioned phosphorus oxy-based additives can effectively solve the problems of severe interfacial side reactions and limited lithium-ion conduction in high-load cathodes at high operating voltages (e.g., above 4.3V), thereby effectively improving the structural stability and electrochemical performance of batteries under high voltage conditions. Moreover, the preparation methods of the aforementioned phosphorus oxy-based additives are easy to implement and mass-produce, with high yields.

[0026] In another aspect of the present invention, the present invention provides a method for preparing the aforementioned phosphorus-oxygenated additive. According to an embodiment of the present invention, the method for preparing the phosphorus-oxygenated additive includes: S100: In a first non-aqueous solvent, phosphate and silane react at a predetermined temperature to obtain a mixed product.

[0027] According to some embodiments of the present invention, when the phosphorooxygenated additive contains a single silane group, that is, the structure of X2 in the general formula of the phosphorooxygenated additive is general formula (II), and X3 is a cyano or halogen atom, the molar ratio of phosphate to silane is 1:1 to 1:1.1. Therefore, the prepared phosphorooxygenated additive has a high yield and good purity.

[0028] According to other embodiments of the present invention, when the phosphorooxygenated additive contains two silane groups, that is, the X2 structure in the general formula of the phosphorooxygenated additive is general formula (II) and the X3 structure in the general formula is also general formula (II), the molar ratio of phosphate to silane is 1:2 to 1:2.7, for example, the molar ratio of phosphate to silane is 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, etc., thereby improving the yield of preparing the product containing two silane groups.

[0029] According to some embodiments of the present invention, the predetermined temperature is -20℃ to 60℃ (e.g., -20℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.), and the reaction time is 2 to 12 hours (e.g., 2 hours, 4 hours, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, etc.). Under the above conditions, the reaction efficiency can be improved, the yield of the target product can be increased, and the occurrence of side reactions can be reduced.

[0030] According to some embodiments of the present invention, the first non-aqueous solvent includes at least one of pyridine, acetonitrile, formamide, N,N-diethylformamide, and N-methylpyrrolidone.

[0031] S200: A second non-aqueous solvent is added to the mixed product, and the phosphorus-oxygenated additive is obtained by extraction. Therefore, the above preparation method is simple, yields good results, is easy to implement, and is suitable for industrial mass production.

[0032] According to some embodiments of the present invention, the second non-aqueous solvent includes at least one of n-hexane, pentane, and petroleum ether.

[0033] According to some embodiments of the present invention, after the extraction step, further fractionation can be carried out to obtain phosphorooxygenated additives, thereby further improving the purity of the product.

[0034] According to some embodiments of the present invention, in the general formula of the phosphorooxyl additive, X1 and X2 are -F, and X3 is -O-Si(CH3)3. The preparation method of this phosphorooxyl electrolyte additive includes: reacting trimethylchlorosilane with difluorophosphoric acid in a first non-aqueous solvent under a nitrogen stream and at a certain temperature to obtain a mixed product; adding a second non-aqueous solvent to the mixed product to obtain a crude compound; and further fractionating to obtain the target product, i.e., the phosphorooxyl additive.

[0035] Furthermore, in some embodiments, the molar ratio of difluorophosphoric acid to trimethylchlorosilane is 1:1 to 1:1.1, the reaction temperature is 30 ℃ to 60 ℃, and the reaction time is 3 to 12 h.

[0036] According to other embodiments of the present invention, in the general formula of the phosphorooxyl additive, X1 is -F, and X2 and X3 are -O-Si-(CH3)3. The preparation method of this phosphorooxyl electrolyte additive includes: reacting sodium monofluorophosphate with trimethylchlorosilane in a first non-aqueous solvent at a certain temperature to obtain a mixed product; adding a second non-aqueous solvent to the mixed product to obtain a crude compound; and further fractionating to obtain the target product, i.e., the phosphorooxyl additive.

[0037] Furthermore, in some embodiments, the molar ratio of sodium monofluorophosphate to trimethylchlorosilane is 1:2 to 1:2.7, the reaction temperature is -20 ℃ to 30 ℃, and the reaction time is 3 to 12 h.

[0038] According to other embodiments of the present invention, in the general formula of the phosphorooxyl additive, X1 is -CN, and X2 and X3 are -O-Si-(CH3)3. The preparation method of this phosphorooxyl electrolyte additive includes: reacting trimethyliodosilane with diethyl cyanophosphate in a first non-aqueous solvent at a certain temperature to obtain a mixed product; adding a second non-aqueous solvent to the mixed product to obtain a crude compound; and further fractionating to obtain the target product, i.e., the phosphorooxyl additive.

[0039] Furthermore, in some embodiments, the molar ratio of sodium monofluorophosphate to trimethylchlorosilane is 1:2.3 to 1:2.8, the reaction temperature is -20 ℃ to 30 ℃, and the reaction time is 2 to 10 h.

[0040] In another aspect, the present invention provides an electrolyte for a lithium battery. According to an embodiment of the present invention, the electrolyte comprises a lithium salt, an organic solvent, and the aforementioned phosphorooxygenated additive. Thus, the phosphorooxygenated additive preferentially decomposes on the positive electrode surface of the battery to form a high-voltage resistant interface film containing P, O, and Si, thereby helping to improve the stability of electrode interface passivation, reduce the occurrence of side reactions, significantly reduce electrolyte consumption, and reduce the dissolution of positive electrode transition metals. Moreover, during the decomposition of the phosphorooxygenated additive on the positive electrode surface, Li3PO4 can be derived. Li3PO4 has high lithium-ion conductivity, which can effectively reduce interfacial impedance and charge transfer resistance, thereby improving the electrochemical performance of the battery. Furthermore, the silicon-based groups in the phosphorooxygenated additive can act as acid-binding agents to remove trace water and HF from the electrolyte and form a flexible interface rich in Si-O groups, which can effectively buffer the volume expansion caused by the accumulation of positive electrode lattice stress, thereby contributing to the obtaining of a high-voltage resistant lithium battery. Therefore, electrolytes with this composition can solve the problems of severe interfacial side reactions and limited lithium-ion conduction in high-load cathodes at high operating voltages (such as above 4.3V), effectively improving the structural stability and electrochemical performance of batteries under high voltage conditions.

[0041] According to some embodiments of the present invention, based on the total weight of the lithium battery electrolyte, the mass fraction of the phosphorus oxygenation additive is 0.5% to 5.0%, for example, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, etc. The phosphorus oxygenation additive at the above-mentioned content can help form a high-voltage resistant interface film, help improve the stability of electrode interface passivation, and effectively reduce interface impedance and charge transfer resistance, thereby improving the electrochemical performance of the battery. If the amount of phosphorus oxygenation additive is too low, the improvement effect is not good; if the amount of phosphorus oxygenation additive is too high, trace amounts of corrosive HF will be generated, which will damage the stability of the positive electrode structure.

[0042] According to some embodiments of the present invention, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxalate borate, and lithium difluorooxalate borate. According to some embodiments of the present invention, the concentration of the lithium salt is 0.5~2 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, etc. Electrolytes under the above conditions have better conductivity, which helps to form a stable interface film and ensures good battery performance requirements such as rate capability, cycle life, capacity retention, and safety.

[0043] According to some embodiments of the present invention, the electrolyte further includes a film-forming agent, said film-forming agent including at least one selected from lithium nitrate, lithium perchlorate, lithium sulfate, lithium difluorophosphate, and lithium carbonate. The phosphoroyl group additive of the present invention exhibits good compatibility in the electrolyte, and when synergistically compounded with the above-mentioned film-forming additive, it enables the electrolyte to possess excellent bulk properties such as oxidation resistance, low viscosity, good electrode / diaphragm wettability, and high ionic conductivity.

[0044] According to some embodiments of the present invention, the concentration of the film-forming agent is 0.1~0.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc. Film-forming agents at these concentrations help to form a structurally stable interfacial film with good ion transport performance on the electrode surface, while reducing the occurrence of side reactions and interfacial defects.

[0045] According to some embodiments of the present invention, the organic solvent includes at least one selected from chain carbonate solvents, cyclic carbonate solvents, and carboxylic acid ester solvents. Specifically, the chain carbonate solvents include at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl trifluoroethyl carbonate; the cyclic carbonate solvents include at least one selected from ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; and the carboxylic acid ester solvents include at least one selected from propyl acetate, ethyl acetate, and propyl propionate.

[0046] According to some embodiments of the present invention, when preparing a lithium battery electrolyte, an organic solvent, lithium salt, film-forming agent, and phosphorus oxygen additive can be mixed in a glove box under an inert gas atmosphere with H2O < 0.01 ppm and O2 < 0.01 ppm to prepare a high-voltage resistant lithium battery electrolyte.

[0047] In another aspect, the present invention provides a lithium battery. According to an embodiment of the invention, the lithium battery includes the electrolyte described above. Therefore, the lithium battery exhibits good structural stability and electrochemical performance under high voltage conditions. Those skilled in the art will understand that the lithium battery possesses all the features and advantages of the phosphorus-oxygenated additives or electrolytes described above, which will not be elaborated further here.

[0048] Those skilled in the art will understand that, in addition to the electrolyte mentioned above, the lithium battery also includes essential battery components such as a positive electrode, a negative electrode, and a separator. There are no special requirements for the specific materials, structures, and preparation methods of the positive electrode, negative electrode, and separator; those skilled in the art can flexibly design and select them based on existing technical means.

[0049] Example Example 1 Phosphorus-oxygenated additives have the structure shown in Formula A1: (A1) The preparation method includes: adding 30g of acetonitrile to a three-necked flask, then adding 4.57g of difluorophosphoric acid, placing a stir bar, purging with nitrogen for protection, and stirring thoroughly. Then, using a constant-pressure separatory funnel, 4.87g of trimethylchlorosilane is added dropwise to the mixture at room temperature. After the addition is complete, the mixture is reacted at 50℃ for 6 hours. After the reaction, the resulting mixture (3×200mL) is extracted with n-hexane, stirred thoroughly, allowed to stand for separation, and the supernatant is collected. The n-hexane is removed by rotary evaporation, and further fractionation yields the phosphorus-oxygenated additive A1.

[0050] The NMR analysis of the phosphoroyl group additive A1 yielded the following results: 1H NMR (400 MHz, CDCl3) δ=0.33 (s, 9H); 19F NMR (376.17 MHz, CDCl3) δ=-80.4 (d, 2F, J=985.9 Hz).

[0051] Electrolyte preparation method: Under argon protection, 1.5M LiPF6 (lithium hexafluorophosphate) was measured in a glove box and then added to a mixed solvent of carbonates. The mixed solvent consisted of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a volume ratio of FEC:EMC = 1:3. The mixture was stirred until homogeneous to obtain a lithium salt solution. Then, the phosphorooxygenated additive and 0.2M film-forming additive LiDFOB (lithium difluorooxalate borate) prepared above were added to the lithium salt solution and mixed thoroughly to obtain the electrolyte for the lithium battery. The phosphorooxygenated additive A1 had a mass content of 2.5wt%.

[0052] Example 2 The steps and composition of the electrolyte preparation are basically the same as in Example 1, except that the mass content of phosphorus oxygen additive A1 is 5 wt%.

[0053] Example 3 The steps and composition of the electrolyte preparation are basically the same as in Example 1, except that the film-forming additive LiDFOB is not added to the electrolyte.

[0054] Example 4 The steps and composition of the electrolyte preparation are basically the same as in Example 2, except that the film-forming additive LiDFOB is not added to the electrolyte.

[0055] Example 5 Phosphorus-oxygenated additives have the structure shown in Formula A2: (A2) The preparation method includes: adding 30g of formamide to a three-necked flask, then adding 8g of sodium monofluorophosphate, placing a stir bar, immersing the flask in an ice bath at 0℃, purging with nitrogen, stirring thoroughly, and then adding 15.4g of dimethylvinylchlorosilane dropwise to the mixture using a constant-pressure separatory funnel. After the addition is complete, the mixture is reacted at room temperature for 5 hours. After the reaction is complete, the resulting mixture (3×200mL) is extracted with n-hexane, stirred thoroughly, allowed to stand for separation, and the supernatant is collected. The n-hexane is removed by rotary evaporation, and the phosphorooxylated additive A2 is obtained by further fractional distillation.

[0056] The NMR analysis of the phosphoroyl group additive A2 yielded the following results: 1 H NMR (400 MHz, CDCl3) δ=0.37 (s, 12H), 5.85-5.91 (dd, 2H), 6.06-6.19 (m, 4H); 19 F NMR (376.17 MHz, CDCl3) δ=-70.88~ -73.36 (d, 1 JFP=935 Hz).

[0057] Electrolyte preparation method: Under argon protection, 1.5M LiPF6 (lithium hexafluorophosphate) was measured in a glove box and then added to a mixed solvent of carbonates. The mixed solvent consisted of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a volume ratio of FEC:EMC = 1:3. The mixture was stirred until homogeneous to obtain a lithium salt solution. The prepared phosphorooxygenated additive and 0.2M film-forming additive LiDFOB (lithium difluorooxalate borate) were then added to the lithium salt solution and mixed thoroughly to obtain the lithium battery electrolyte. The phosphorooxygenated additive A2 had a mass content of 2.5 wt%.

[0058] For the contact angle test of the electrolyte to the positive electrode, please refer to [link / reference needed]. Figure 1 .

[0059] Example 6 The steps and composition of the electrolyte preparation are basically the same as in Example 5, except that the mass content of phosphorus oxygen additive A2 is 5wt%.

[0060] Example 7 Phosphorus-oxygenated additives have the structure shown in Formula A3: (A3) The preparation method includes: adding 30g of formamide to a three-necked flask, then adding 8g of sodium monofluorophosphate, placing a stir bar, immersing the flask in an ice bath at 0℃, purging with nitrogen, stirring thoroughly, and then adding 18.4g of trivinylchlorosilane dropwise to the mixture using a constant pressure separatory funnel. After the addition is complete, the mixture is reacted at room temperature for 5 hours. After the reaction is complete, the resulting mixture (3×200mL) is extracted with n-hexane, stirred thoroughly, allowed to stand for separation, and the supernatant is collected. The n-hexane is removed by rotary evaporation, and the phosphorooxygenated additive A3 is obtained by further fractional distillation.

[0061] Electrolyte preparation method: Under argon protection, 1.5M LiPF6 (lithium hexafluorophosphate) was measured in a glove box and then added to a mixed solvent of carbonates. The mixed solvent consisted of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a volume ratio of FEC:EMC = 1:3. The mixture was stirred until homogeneous to obtain a lithium salt solution. Then, the phosphorooxygenated additive A3 and 0.2M film-forming additive LiDFOB (lithium difluorooxalate borate) prepared above were added to the lithium salt solution and mixed thoroughly to obtain the electrolyte for the lithium battery. The mass content of phosphorooxygenated additive A3 was 2.5 wt%.

[0062] Example 8 The steps and composition of the electrolyte preparation are basically the same as in Example 7, except that the mass content of phosphorus oxygen additive A3 is 5 wt%.

[0063] Example 9 Phosphorus-oxygenated additives have the structure shown in Formula A4: (A4) The preparation method includes: adding 30g of formamide to a three-necked flask, then adding 9g of diethyl cyanophosphate, placing a stir bar, immersing the flask in an ice bath at 0℃, purging with nitrogen, stirring thoroughly, and then adding 22g of trimethyliodosilane dropwise to the mixture using a constant pressure separatory funnel. After the addition is complete, the mixture is reacted at room temperature for 3 hours. After the reaction is complete, the resulting mixture (3×200mL) is extracted with n-hexane, stirred thoroughly, allowed to stand for separation, and the supernatant is collected. The n-hexane is removed by rotary evaporation, and the phosphorooxygenated additive A4 is obtained by further fractional distillation.

[0064] Electrolyte preparation method: Under argon protection, 1.5M LiPF6 (lithium hexafluorophosphate) was measured in a glove box and then added to a mixed solvent of carbonates. The mixed solvent consisted of fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) in a volume ratio of FEC:EMC = 1:3. The mixture was stirred until homogeneous to obtain a lithium salt solution. Then, the phosphorooxygenated additive A4 and 0.2M film-forming additive LiDFOB (lithium difluorooxalate borate) prepared above were added to the lithium salt solution and mixed thoroughly to obtain the electrolyte for the lithium battery. The mass content of phosphorooxygenated additive A4 was 2.5wt%.

[0065] Example 10 The steps and composition of the electrolyte preparation are basically the same as in Example 9, except that the mass content of phosphorus oxygenated additive A4 is 5 wt%.

[0066] Comparative Example 1 The steps and composition for preparing the electrolyte are basically the same as in Example 2, except that no phosphorus-oxygenated additives are added. The contact angle test of this electrolyte with the positive electrode can be found in [reference needed]. Figure 1 .

[0067] Batteries were assembled and tested using the electrolytes obtained in the examples and comparative examples, respectively. After standing overnight, cycle performance tests were conducted. In the test batteries, a 500 μm thick lithium sheet was used as the negative electrode, and lithium-rich manganese oxide (LRMO) powder was used as the positive electrode active material. The positive electrode was coated onto an aluminum current collector using polyvinylidene fluoride (PVDF) as a binder and conductive carbon powder, with a loading of 4 mg / cm³. 2The separator was Celgard 2325. The assembled Li|LRMO battery was activated at room temperature by charge-discharge at 0.2 C and 2-4.8 V for 5 cycles, followed by charge-discharge testing at a constant rate of 2C. The cycle stability test and characterization results are shown in Table 1. The electrochemical impedance spectroscopy spectra of the test batteries corresponding to Example 5 and Comparative Example 1 after 100 cycles can be found in [reference needed]. Figure 2 The cycle performance graphs of the test batteries corresponding to Example 5 and Comparative Example 1 at a 2C charge / discharge rate can be found in [reference needed]. Figure 3 .

[0068] Table 1

[0069] The results above show that, compared to Comparative Example 1, in all embodiments, the electrolyte containing the phosphorooxylated additive of the present invention exhibits better wettability of the electrode due to the strong polarity of the silicon-based electrolyte; in all embodiments, the content of Ni, Mn, and other transition metal ions dissolved in the electrolyte is significantly reduced after 100 battery cycles; and the impedance R of the battery in the embodiments is... ct All of them are lower than Comparative Example 1, indicating that the positive electrode interface film (CEI) constructed by the decomposition of phosphorus-oxygenated additives imparts good passivation stability and structural stability to the electrode. Moreover, due to the interface being rich in lithium-conducting Li3PO4, it exhibits faster lithium-ion transport kinetics. The batteries corresponding to Examples 5-9 can stably cycle for more than 800 cycles.

[0070] Moreover, as can be seen from the comparison of Examples 1 to 4, the combination of the phosphoroxyl additive and the film-forming agent of the present invention can better improve the wettability of the electrolyte and the stability of the interface, better reduce the dissolution of transition metals, and better improve the electrochemical performance of the battery.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A phosphoroyl group additive, characterized in that, The structural formula of the phosphorooxylated additive is the following general formula (Ⅰ): （Ⅰ）， Wherein, X1 is a cyano group, a halogen atom, or a C1-C8 alkyl or alkoxy group substituted with a halogen atom, an alkenyl group, or an alkynyl group; X2 has the following general formula (Ⅱ) structure: （Ⅱ）； Wherein, Y is C, N or O, and R1, R2 and R3 can be independently selected from halogen atoms, C1-C8 alkoxy, alkyl, alkenyl, alkynyl or aryl groups substituted or unsubstituted by halogen atoms; X3 can be a cyano group, a halogen atom, or X2.

2. The phosphorooxylated additive according to claim 1, characterized in that, The phosphorooxyl additive is at least one of the following structural formulas: 。 3. A method for preparing the phosphoro-oxygenated additive of claim 1 or 2, characterized in that, include: In a first non-aqueous solvent, phosphate and silane react at a predetermined temperature to obtain a mixed product; A second non-aqueous solvent is added to the mixture, and the phosphorooxylated additive is obtained by extraction.

4. The method according to claim 3, characterized in that, At least one of the following conditions must be met: When the phosphorooxyl additive contains a single silane group, the molar ratio of the phosphate to the silane is 1:1 to 1:1.1; when the phosphorooxyl additive contains two silane groups, the molar ratio of the phosphate to the silane is 1:2 to 1:2.

7. The predetermined temperature is -20 ℃ to 60 ℃, and the reaction time is 2 to 12 h.

5. An electrolyte for a lithium battery, characterized in that, Includes lithium salts, organic solvents, and phosphorus-oxygenated additives as described in claim 1 or 2.

6. The electrolyte according to claim 5, characterized in that, Based on the total weight of the lithium battery electrolyte, the mass fraction of the phosphorus oxygenation additive is 0.5% to 5.0%.

7. The electrolyte according to claim 5 or 6, characterized in that, The concentration of the lithium salt is 0.5~2 mol / L. And / or, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium di(oxalate)borate, and lithium di(fluorooxalate)borate.

8. The electrolyte according to claim 5 or 6, characterized in that, It also includes film-forming agents, said film-forming agents comprising at least one of lithium nitrate, lithium perchlorate, lithium sulfate, lithium difluorophosphate, and lithium carbonate. And / or, the concentration of the film-forming agent is 0.1~0.5 mol / L.

9. The electrolyte according to claim 5 or 6, characterized in that, The organic solvent includes at least one of chain carbonate solvents, cyclic carbonate solvents, and carboxylic acid ester solvents; The chain carbonate solvents include at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl trifluoroethyl carbonate; The cyclic carbonate solvents include at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate. The carboxylic acid ester solvent includes at least one of propyl acetate, ethyl acetate, and propyl propionate.

10. A lithium battery, characterized in that, The electrolyte includes any one of claims 5 to 9.

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