Aza-silane electrolyte additive, electrolyte and lithium ion battery

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a nitrogen heterosilane electrolyte additive, an electrolyte and a lithium ion battery. The nitrogen heterosilane electrolyte additive has a structure shown in formula I. The application first proposes a nitrogen heterosilane electrolyte additive, the unique structure of the additive can effectively eliminate HF in the electrolyte and protect the active material; meanwhile, the additive can effectively complex transition metal manganese ions in the electrolyte and effectively inhibit manganese deposition to protect the negative electrode SEI film; the structure contains various characteristic groups, which can solve the industry problem of manganese ion dissolution from the positive electrode interface-transition metal dissolution-negative electrode interface in multiple aspects, effectively protect the film structure in the battery system, thereby improving the electrochemical performance of the battery, solving the pain points of manganese iron lithium phosphate, lithium nickel manganese oxide and lithium-rich manganese and other materials, and developing a matching electrolyte.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a nitrogen-based silane electrolyte additive, an electrolyte, and a lithium-ion battery. Background Technology

[0002] With the increasing popularity of electric vehicles, portable devices, and other electronic products, the demand for high-energy-density lithium-ion batteries is becoming more and more urgent. This type of battery has broad application prospects in energy storage, aerospace, and other fields, and how to improve the energy density of lithium batteries has become a key research focus for scholars.

[0003] Currently, lithium manganese iron phosphate cathode materials, which offer the same cost and safety as lithium iron phosphate and the same energy density as high-voltage ternary cathode materials, lithium nickel manganese oxide cathode materials with high energy density and low production cost, and lithium-rich manganese-based cathode materials have received widespread attention and research. However, all of these materials suffer from poor high-temperature cycling and storage performance, limiting their application. On the other hand, at high temperatures, the corrosion of the cathode material by the electrolyte leads to capacity decay and the dissolution of transition metal manganese. The dissolved manganese ions can also deposit on the anode, damaging the SEI film at the anode interface and further degrading the material.

[0004] The process by which transition metals in the electrolyte damage the electrochemical performance of the battery includes the following steps: manganese dissolution from the positive electrode - manganese dissolution in the electrolyte - manganese deposition at the negative electrode. Because manganese ions dissolve, they will undergo a disproportionation reaction on the surface of the positive electrode material to generate divalent manganese, which will migrate to the surface of the negative electrode and be reduced and deposited, thereby damaging the SEI film. This leads to the continuous growth and thickening of the SEI film, resulting in problems such as consumption of active lithium, increased electrode impedance, and gas generation at the negative electrode, ultimately leading to a continuous decline in battery capacity.

[0005] To address the severe manganese ion leaching problem mentioned above, there are generally three strategies from the perspective of the electrolyte: First, form an effective positive electrode CEI film structure to avoid corrosion of the positive electrode material by the electrolyte and prevent manganese ion leaching from the source; second, form a dense and tough SEI film structure at the negative electrode to reduce the damage to the SEI film caused by manganese deposition at the negative electrode; and third, capture manganese ions in the solvent to prevent damage to the SEI film caused by manganese deposition at the negative electrode.

[0006] Most current commercial additives focus on improving one aspect, making it difficult to completely avoid the dissolution and damage of transition metals. Only when the three levels of manganese dissolution, dissolution, and deposition work together can the industry's pain points be solved from the perspective of electrolytes. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a nitrogen-based silane electrolyte additive, an electrolyte, and a lithium-ion battery, which solves the problem of manganese ion dissolution from three aspects.

[0008] To achieve the above objectives, the present invention provides a azirsilane electrolyte additive having the structure shown in Formula I:

[0009]

[0010] Where 0 ≤ n1 ≤ 3; 1 ≤ n2 ≤ 2;

[0011] R1 and R2 are independently selected from alkyl groups from C1 to C6.

[0012] The above n1 is any integer from 0 to 3, specifically 0, 1, 2 or 3.

[0013] The above n2 is any integer from 1 to 2, specifically it can be 1 or 2.

[0014] R1 and R2 are independently selected from alkyl groups of C1 to C6, more preferably independently selected from alkyl groups of C1 to C4, and even more preferably independently selected from alkyl groups of C1 to C3. Specifically, they can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl.

[0015] The azasilane electrolyte additive structure provided by this invention contains Si-O bonds, which can react with HF in the electrolyte to reduce the destructive effect of HF on the surface of the manganese-based cathode, thus protecting the cathode material. The azasilane electrolyte additive structure also contains Si-N bonds, which can also react with HF and H2O in the electrolyte to protect the cathode. Simultaneously, after the Si-N bonds react with HF, the azasilane ring opens, and the resulting chain-like product adheres to the surface of the active material, forming a flexible and robust organic film to prevent corrosion of the active material by the electrolyte. The azasilane electrolyte additive structure also contains ethyleneamine chains, where the arc pair electrons of the N atom can complex with transition metal ions but do not participate in film formation. The long chain has multiple active sites for binding with metal ions, forming a more stable structure with the transition metal Mn. This complexation effect can capture transition metal ions in the electrolyte, significantly slowing down the damage of dissolved manganese to the negative electrode surface. These effects are superior to using additives containing the above-mentioned structures alone, thus solving the problem of manganese ion dissolution from three aspects.

[0016] This invention provides a method for preparing the above-mentioned azirsilane electrolyte additive, comprising the following steps:

[0017] S1) The ethyleneamine shown in formula I-a undergoes a substitution reaction with the bromotrichlorosilane shown in formula I-b to obtain an intermediate;

[0018] S2) The obtained intermediate is subjected to a substitution reaction with a C1-C6 alcohol to obtain the intermediate shown in Formula I-d;

[0019] The intermediate shown in Formula I-d undergoes a condensation reaction with pyridine and hexamethyldisilazane to obtain the azasilane electrolyte additive shown in Formula I.

[0020]

[0021] Where 0 ≤ n1 ≤ 3; 1 ≤ n2 ≤ 2;

[0022] R, R1, and R2 are independently selected from alkyl groups from C1 to C6.

[0023] The ranges of n1, n2, R1, and R2 mentioned above are the same as those described above.

[0024] The range of R is the same as the range of R1 and R2 mentioned above.

[0025] The preferred molar ratio of the ethyleneamine shown in Formula I-a to the bromotrichlorosilane shown in Formula I-b is (1 to 1.05):1.

[0026] In some specific embodiments of the present invention, the ethyleneamine represented by Formula I-a is selected from diethylenetriamine, ethylenediamine, triethylenetetramine, or tetraethylenepentamine.

[0027] In some specific embodiments of the present invention, the bromotrichlorosilane represented by Formula I-b is selected from 3-bromopropyltrichlorosilane or 3-bromobutyltrichlorosilane.

[0028] The preferred reaction temperature for the substitution reaction in step S1) is -20 to 0°C, and the preferred reaction time is 1 to 3 hours.

[0029] Preferably, an acid-binding agent is added to the substitution reaction system.

[0030] The acid-binding agent is preferably triethylamine.

[0031] The preferred molar ratio of triethylamine to ethyleneamine is (5-8):1.

[0032] The preferred molar ratio of the intermediate shown in Formula I-c to the C1-C6 alcohol is 1:(3-3.1).

[0033] In some specific embodiments of the present invention, the C1 to C6 alcohol compounds are selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, n-pentanol, or n-hexanol.

[0034] The preferred reaction temperature for the substitution reaction in step S2) is 0–20°C, and the preferred reaction time is 3–5 h.

[0035] Preferably, pyridine is added to the substitution reaction system.

[0036] The preferred reaction temperature for the condensation reaction in step S3) is 50–70°C, more preferably 50–60°C; the preferred reaction time is 3–5 h.

[0037] The reaction equations for the above preparation method are as follows:

[0038]

[0039] In the above reaction equations, the ranges of n1, n2, and R are the same as those described above.

[0040] The above reaction is preferably carried out under the protection of an inert gas.

[0041] Another aspect of the present invention provides a lithium-ion electrolyte comprising: a non-aqueous solvent, a lithium salt, and the aforementioned azirsilane electrolyte additive.

[0042] The present invention does not specifically limit the types of non-aqueous solvents mentioned above, and can be any organic solvents suitable for lithium-ion electrolytes that are well known to those skilled in the art, preferably including any one or more of carbonate solvents, carboxylic acid ester solvents, amine solvents, sulfone solvents, and nitrile solvents.

[0043] The carbonate solvents include, but are not limited to, one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl propyl carbonate, butene carbonate, methyl butyl carbonate, and dibutyl carbonate.

[0044] The carboxylic acid ester solvents include, but are not limited to, one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and methyl propionate.

[0045] The amine solvents include, but are not limited to, one or more of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide.

[0046] The sulfone solvents include, but are not limited to, one or more of dimethyl sulfoxide, sulfolane, diphenyl sulfoxide, thionyl chloride, dipropyl sulfone, dimethyl sulfite, diethyl sulfite, and tetramethyl sulfoxide.

[0047] The nitrile solvents include, but are not limited to, one or more of acetonitrile, butadione, adiponitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile, and 1,3,6-hexanetrionitrile.

[0048] The content of the non-aqueous solvent in the electrolyte is preferably 70% to 90 wt%.

[0049] The present invention does not specifically limit the lithium salt, and can be any lithium salt suitable for lithium-ion electrolytes that is well known to those skilled in the art, including but not limited to one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalateborate, and lithium bis(oxalateborate).

[0050] The concentration of the lithium salt in the electrolyte is preferably 0.5–2 M.

[0051] The amount of the azirsilane electrolyte additive added is preferably 0.05wt% to 3wt%, more preferably 0.1wt% to 1wt%.

[0052] Another aspect of the present invention provides a lithium-ion battery comprising the above-described lithium-ion electrolyte.

[0053] The present invention does not impose any special limitation on the structure of the above-mentioned lithium-ion battery, and can be any lithium-ion battery structure known to those skilled in the art. Preferably, the structure further includes a positive electrode, a negative electrode and a separator.

[0054] This invention does not specifically limit the structure of the aforementioned positive electrode; it can be any positive electrode suitable for lithium-ion batteries well-known to those skilled in the art. Preferably, the positive electrode includes a positive electrode current collector and a positive electrode material layer disposed on the surface of the positive electrode current collector. The material of the positive electrode current collector can be selected from aluminum, titanium, or stainless steel. The positive electrode material layer preferably includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), medium-high nickel ternary materials, and their composite positive electrode materials. The conductive agent includes, but is not limited to, carbon materials, such as carbon black, conductive polymers, acetylene black, carbon fibers, carbon nanotubes, and graphite, or one or more of these. The binder includes, but is not limited to, polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene monomer (EPDM), and styrene-butadiene rubber (SBR), or one or more of these.

[0055] This invention does not specifically limit the structure of the aforementioned negative electrode; it can be any negative electrode suitable for lithium-ion batteries known to those skilled in the art. Preferably, the negative electrode may include a negative electrode current collector and a negative electrode material layer on the surface of the current collector. The material of the negative electrode current collector includes, but is not limited to, copper, nickel, or stainless steel. The negative electrode material layer includes, but is not limited to, a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes, but is not limited to, metallic lithium, lithium-intercalated carbon materials, or lithium alloys. The conductive agent and binder used for the negative electrode are the same as those used for the positive electrode.

[0056] The present invention does not specifically limit the material of the above-mentioned separator membrane, and it can be any separator membrane suitable for lithium-ion batteries that is well known to those skilled in the art, including but not limited to polypropylene (PP), polyethylene (PE), polypropylene (PP) and polyethylene (PE) composite materials, glass fiber mat, and composite membranes formed by welding or bonding with wettable polyolefin microporous membranes.

[0057] Experimental results show that the electrolyte prepared using the azirsilane electrolyte additive provided by this invention can eliminate HF and H2O in the electrolyte, and can form a film on the surface of the active material, which significantly improves the first efficiency, capacity retention and cycle stability of the battery cell, and greatly reduces the deposition of transition metal Mn on the negative electrode.

[0058] Compared with the prior art, the present invention provides a azirsilane electrolyte additive having the structure shown in Formula I.

[0059] This invention is the first to propose a azirsilane electrolyte additive. The unique structure of this additive can effectively eliminate HF in the electrolyte, protecting the active materials. At the same time, it can effectively complex manganese ions in the electrolyte, effectively inhibiting manganese deposition and protecting the SEI film of the negative electrode. The various characteristic groups contained in its structure can solve the industry problem of manganese ion dissolution from multiple angles from the positive electrode interface to the transition metal dissolution to the negative electrode interface, effectively protecting the film structure in the cell system, thereby improving the electrochemical performance of the battery, solving the pain points of materials such as lithium manganese iron phosphate, lithium nickel manganese oxide, and lithium-rich manganese, and developing matching electrolytes. Detailed Implementation

[0060] To further illustrate the present invention, a detailed description is provided below with reference to embodiments. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0061] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0062] Example 1

[0063] At -20℃, 0.105 mol of diethylenetriamine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromopropyltrichlorosilane was slowly added under stirring. The reaction was continued for 2 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.31 mol of propanol was added at 10℃ under stirring and reacted for 3 hours. The temperature was raised to 60℃, and 0.05 mol of hexamethyldisilazane was added and reacted for 4 hours. The mixed solution was then separated and extracted by rapid chromatography to obtain compound A. GC-MS (m / z): calcd.for C13 H 31 O2N3Si[M +1 ] + ,289.22,found289.71.

[0064]

[0065] Take 30wt% EC, 30.5wt% DMC and 26wt% EMC in a glove box and stir them evenly to form a mixed solution; add 13wt% LiPF6 to the mixed solution and stir until fully dissolved to obtain a mixed salt solution; further add 0.5wt% compound A to the mixed salt solution and use the resulting mixed solution as an electrolyte.

[0066] Battery fabrication:

[0067] Take 95wt% LiMn 0.4 Fe 0.6 PO4, 2.5 wt% PVDF and 2.5 wt% conductive carbon black are mixed and dispersed evenly in N,N-dimethylpyrrolidone to form a slurry, which is then uniformly coated onto aluminum foil.

[0068] Cutting sheet: 94.8 wt% artificial graphite, 1.7 wt% CMC, 1 wt% SBR and 2.5 wt% conductive carbon black are mixed and dispersed evenly in pure water to make a slurry, which is then evenly coated on copper foil and rolled into a cutting sheet.

[0069] The 2032 button cell is assembled in the following order: negative electrode shell—negative electrode sheet—polypropylene separator—positive electrode sheet—gasket—spring sheet—positive electrode shell.

[0070] To investigate the complexation effect of additives on the transition metal manganese, the battery was disassembled after 200 cycles, and the graphite negative electrode of the coin cell was subjected to inductively coupled plasma (ICP) testing to analyze the deposition of transition metal manganese on the negative electrode. The coin cell cycle test was performed with a constant current and constant voltage of 0.2C to 4.4V, and a constant current discharge of 0.2C to 3V.

[0071] Example 2

[0072] At 0℃, 0.10 mol of ethylenediamine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromopropyltrichlorosilane was slowly added under stirring. The reaction was continued for 2 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.3 mol of methanol was added at 20℃ under stirring and the reaction was carried out for 4 hours. The temperature was raised to 50℃, and 0.05 mol of hexamethyldisilazane was added and the reaction was carried out for 3 hours. The mixed solution was then separated and extracted by rapid chromatography to obtain compound B. GC-MS (m / z): calcd. for C7H18 O2N2Si[M +1 ] + , 190.11, found 190.64.

[0073]

[0074] In a glove box, 30 wt% EC, 30 wt% DMC, and 26 wt% EMC were mixed evenly to form a mixed solution. 13 wt% LiPF6 was added to the mixed solution and stirred until fully dissolved to obtain a mixed salt solution. 1 wt% compound B was further added to the mixed salt solution, and the resulting mixed solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0075] Example 3

[0076] At -10℃, 0.103 mol of diethylenetriamine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromobutyltrichlorosilane was slowly added under stirring. The reaction was continued for 3 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.31 mol of ethanol was added under stirring at 10℃ and the reaction was carried out for 5 hours. The temperature was raised to 60℃ and 0.05 mol of hexamethyldisilazane was added and the reaction was carried out for 4 hours. The mixed solution was then separated and extracted by rapid chromatography to obtain compound C. GC-MS (m / z): calcd.for C 12 H 29 O2N3Si[M +1 ] + ,275.20,found276.13.

[0077]

[0078] In a glove box, 30 wt% EC, 30.95 wt% DMC, and 26 wt% EMC were mixed to form a homogeneous solution. 13 wt% LiPF6 was added to the homogeneous solution and stirred until fully dissolved to obtain a homogeneous salt solution. 0.05 wt% compound C was further added to the homogeneous salt solution, and the resulting homogeneous solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0079] Example 4

[0080] At 0℃, 0.104 mol of tetraethylenepentamine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromopropyltrichlorosilane was slowly added under stirring. The reaction was continued for 3 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.305 mol of methanol was added under stirring at 20℃ for 5 h. The temperature was raised to 70℃, and 0.05 mol of hexamethyldisilazane was added and reacted for 4 h. The mixed solution was then separated and extracted by rapid chromatography to obtain compound D. GC-MS (m / z): calcd.for C 13 H 33 O2N5Si[M +1 ] + , 319.24, found 319.63.

[0081]

[0082] In a glove box, 30 wt% EC, 30.9 wt% DMC, and 26 wt% EMC were mixed to form a homogeneous solution. 13 wt% LiPF6 was added to the homogeneous solution and stirred until fully dissolved to obtain a homogeneous salt solution. 0.1 wt% compound D was further added to the homogeneous salt solution, and the resulting homogeneous solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0083] Example 5

[0084] At 0℃, 0.102 mol of triethylenetetramine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromobutyltrichlorosilane was slowly added under stirring. The reaction was continued for 2 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.303 mol of methanol was added under stirring at 0℃ and reacted for 5 h. The temperature was raised to 60℃, and 0.05 mol of hexamethyldisilazane was added and reacted for 4 h. The mixed solution was then separated and extracted by rapid chromatography to obtain compound E. GC-MS (m / z): calcd.for C 12 H 30 O2N4Si[M +1 ] + , 290.20, found 290.58.

[0085]

[0086] In a glove box, 30 wt% EC, 28 wt% DMC, and 26 wt% EMC were mixed evenly to form a mixed solution. 13 wt% LiPF6 was added to the mixed solution and stirred until fully dissolved to obtain a mixed salt solution. 3 wt% compound E was further added to the mixed salt solution, and the resulting mixed solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0087] Comparative Example 1

[0088] In a glove box, 30 wt% EC, 31 wt% DMC, and 26 wt% EMC were mixed evenly to form a mixed solution. 13 wt% LiPF6 was added to the mixed solution and stirred until fully dissolved to obtain a mixed salt solution for use as an electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0089] Comparative Example 2

[0090] In a glove box, 30 wt% EC, 30 wt% DMC, and 26 wt% EMC were mixed evenly to form a mixed solution. 13 wt% LiPF6 was added to the mixed solution and stirred until fully dissolved to obtain a mixed salt solution. 0.5 wt% diethylenetriamine, 0.25 wt% hexamethyldisilazane, and 0.25 wt% tetrapropoxysilane were further added to the mixed salt solution, and the resulting mixed solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the Mn deposition content of the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0091] Comparative Example 3

[0092] At 0℃, 0.10 mol of pentaethylenehexamine was added to 50 mL of triethylamine, and 0.1 mol of 3-bromopropyltrichlorosilane was slowly added under stirring. The reaction was continued for 2 hours. After the reaction was completed, 50 mL of 1 mol / L sodium bicarbonate aqueous solution was added to wash and extract the organic phase. The intermediate obtained by distillation of the organic phase was added to 50 mL of pyridine, and 0.3 mol of methanol was added at 20℃ with stirring and the reaction was carried out for 4 hours. The temperature was raised to 50℃, and 0.05 mol of hexamethyldisilazane was added and the reaction was carried out for 3 hours. The mixed solution was then separated and extracted by rapid chromatography to obtain compound F. GC-MS (m / z): calcd.for C 15 H 38 O2N6Si[M +1 ] + , 362.28, found 362.59.

[0093]

[0094] In a glove box, 30 wt% EC, 30 wt% DMC, and 26 wt% EMC were mixed evenly to form a mixed solution. 13 wt% LiPF6 was added to the mixed solution and stirred until fully dissolved to obtain a mixed salt solution. 1 wt% compound F was further added to the mixed salt solution, and the resulting mixed solution was used as the electrolyte. After 200 cycles, the battery was disassembled and the deposition content of Mn on the graphite anode was analyzed. The battery preparation and testing were the same as in Example 1.

[0095] Table 1. Mn deposition content of batteries prepared in Examples 1-5 and Comparative Examples 1-3

[0096]

[0097] A comparison of Examples 1-5 with Comparative Example 1 reveals that adding the electrolyte additive described in this invention can eliminate HF and H2O in the electrolyte, and can also form a film on the surface of the active material, significantly improving the first-time efficiency and capacity retention of the battery cell. From the Mn deposition content of the negative electrode, it is found that the additive described in this invention can effectively inhibit the dissolution of Mn ions and improve the cycle stability of the battery cell.

[0098] By comparing Example 1 with Comparative Example 2, it can be found that the additive described in this article solves the drawbacks of ethyleneamine chains not being able to form films and the decomposition of silazane additives into small molecules affecting high-temperature performance through the synergistic effect between various functional groups. This makes the cell performance better than when each functional group is used alone, improves the cell's first efficiency and cycle stability, and further reduces the deposition of transition metal Mn on the negative electrode.

[0099] By comparing Example 2 and Comparative Example 3, it can be found that when n1>3, the performance of the battery cell shows a deterioration trend, which is related to the fact that the longer ethyleneamine chain increases the film-forming impedance of the battery cell.

[0100] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A azirsilane electrolyte additive having the structure shown in Formula I: Formula I; in, 0≤n1≤3;1≤n2≤2; R1 and R2 are independently selected from C1 to C6 alkyl groups; The azasilane electrolyte additive is not selected from the following structures: 。 2. The azasilane electrolyte additive according to claim 1, characterized in that, R1 and R2 are independently selected from C1 to C4 alkyl groups.

3. The method for preparing the azasilane electrolyte additive according to any one of claims 1 to 2, comprising the following steps: S1) The ethyleneamine shown in formula I-a undergoes a substitution reaction with the bromotrichlorosilane shown in formula I-b to obtain an intermediate; S2) The obtained intermediate is subjected to a substitution reaction with a C1~C6 alcohol to obtain the intermediate shown in Formula I-d; S3) The intermediate shown in Formula I-d undergoes a condensation reaction in the presence of pyridine and hexamethyldisilazane to obtain the azasilane electrolyte additive shown in Formula I. Formula I-a; Formula I-b; Formula I-d; Formula I; Where 0 ≤ n1 ≤ 3; 1 ≤ n2 ≤ 2; R, R1, and R2 are independently selected from C1 to C6 alkyl groups.

4. The preparation method according to claim 3, characterized in that, The molar ratio of the ethyleneamine shown in Formula I-a to the bromotrichlorosilane shown in Formula I-b is (1~1.05):1; The substitution reaction in step S1) is carried out at a temperature of -20 to 0°C and for a time of 1 to 3 hours. An acid-binding agent is added to the substitution reaction system; The acid-binding agent is triethylamine; the molar ratio of triethylamine to ethyleneamine is (5~8):

1.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the intermediate to the C1-C6 alcohol is 1:(3-3.1). The substitution reaction in step S2) is carried out at a temperature of 0-20°C for 3-5 hours. The substitution reaction system contains pyridine.

6. The preparation method according to claim 3, characterized in that, The condensation reaction in step S3) is carried out at a temperature of 50-70°C for 3-5 hours.

7. A lithium-ion electrolyte, comprising: Non-aqueous solvents, lithium salts, and azirsilane electrolyte additives; The azasilane electrolyte additive has the structure shown in Formula I: Formula I; Where 0 ≤ n1 ≤ 3; 1 ≤ n2 ≤ 2; R1 and R2 are independently selected from C1 to C6 alkyl groups.

8. The lithium-ion electrolyte according to claim 7, characterized in that, The non-aqueous solvent includes any one or more of carbonate solvents, carboxylic acid ester solvents, amine solvents, sulfone solvents, and nitrile solvents; The lithium salt includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalateborate, and lithium bis(oxalateborate). The concentration of the lithium salt is 0.5~2M; The amount of the azirsilane electrolyte additive added is 0.05wt%~3wt%.

9. The lithium-ion electrolyte according to claim 8, characterized in that, The carbonate solvents include one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl propyl carbonate, butene carbonate, methyl butyl carbonate, and dibutyl carbonate. The carboxylic acid ester solvents include one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and methyl propionate. The amine solvent includes one or more of N-methylacetamide, N-methylformamide, dimethylformamide, and diethylformamide; The sulfone solvents include one or more of dimethyl sulfoxide, sulfolane, diphenyl sulfoxide, thionyl chloride, dipropyl sulfone, dimethyl sulfite, diethyl sulfite, and tetramethyl sulfoxide; The nitrile solvents include one or more of acetonitrile, butadionitrile, adiponitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile, and 1,3,6-hexanetrionitrile.

10. A lithium-ion battery comprising the lithium-ion electrolyte according to any one of claims 7 to 9.

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