Lithium salt containing cyanide, preparation method thereof, lithium battery electrolyte, and lithium battery

Abstract

The present invention provides a cyano group-containing lithium salt, a preparation method thereof, a lithium battery electrolyte, and a lithium battery. The cyano group-containing lithium salt has a structure represented by Formula I. The present invention utilizes the coordinating nitrogen atom in the cyano group to coordinate with the transition metal in the positive electrode material during the lithium battery's static and charging processes, thereby stabilizing the positive electrode material, inhibiting the dissolution of the transition metal and side reactions catalyzed by its active sites, and indirectly optimizing the formation of the CEI film, thereby effectively passivating the positive electrode interface and improving the battery's high-voltage resistance, cycle stability, and rate performance. This can further expand the market for equipment with high requirements for lithium battery fast charging and long cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a cyanide-containing lithium salt, a preparation method thereof, a lithium battery electrolyte, and a lithium battery. Background Art

[0002] As demand for electronic devices and electric vehicles continues to increase, lithium batteries have become an increasingly important energy storage device. Lithium batteries are highly efficient, lightweight, environmentally friendly, and rechargeable, finding widespread use in electronic devices, electric vehicles, energy storage systems, solar panels, and more.

[0003] With the increasing application of lithium batteries, research and development has become a hot field. Batteries are required to have increasingly higher energy densities, wider operating temperature ranges, and, in particular, higher charging speeds and longer lifespans. However, conventional carbonate electrolytes, due to their high viscosity and low conductivity, often face challenges with charging speeds and cycle life. These issues arise primarily because when charging speeds are too fast, the mobility of lithium ions cannot keep up with the current changes, resulting in reduced charging efficiency and potentially damaging the battery's structure and performance. Changes in the structure of the battery's internal cathode material inevitably lead to reduced charge and discharge capacity, rapid capacity decay, poor rate performance, and a significant reduction in cycle life.

[0004] Currently, most of the publicly reported electrolyte research is to help improve low-temperature performance by optimizing the electrolyte lithium salt or solvent and adding functional additives. The method is simple and the effect is significant. CN113991181A discloses a method for mixing ethylene carbonate-based solvents and propylene carbonate-based solvents, which optimizes the electrolyte solvent composition, increases the solvation effect of lithium ions, and greatly reduces the impedance of the solid electrolyte interface formed by the electrolyte on the surface of the electrode material by using additives, thereby solving the problem of high-rate charge and discharge of the battery. However, the use of its graphite negative electrode still has the problems of low energy density and cycle life. CN114122542A uses new charge and discharge technology to improve the cycle of cylindrical lithium iron phosphate material batteries, and can also appropriately shorten the actual charging time of the battery. However, this technical solution does not fundamentally solve the problems of cycle life and high-rate charge and discharge, and therefore, it has no practical expansibility. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a cyanide-containing lithium salt and a preparation method thereof, a lithium battery electrolyte, and a lithium battery, which achieve excellent battery fast charging and long cycle life and have high practical application value.

[0006] In a first aspect, the present invention provides a cyanide-containing lithium salt having a structure shown in Formula I:

[0007]

[0008] Wherein, Z1 and Z2 are the same or different and are independently selected from a single bond, -(CH2) x -、-(CH2CH2O) x -、-(CXH) x -、-(CX2) x -、-(BH) x -、-(SiH2) x -, sulfinyl, sulfonyl or one or more; x, y are integers within the range of 0 to 10, X = F, Cl, Br or I;

[0009] R is selected from one of a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a C1-C10 haloalkyl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, a cyano group, a phenyl group, a fluorophenyl group, a trimethylsilyl group, a trifluoromethylsilyl group, a cyclotriphosphino group, a fluorocyclotriphosphino group, an isocyanate group, a lithium group, and a C1-C10 alkyl group.

[0010] In some embodiments of the present invention, the cyanide-containing lithium salt structure contains -SO2CF2- with strong electron-withdrawing ability or -S(=O)2-(CH2CH2O)3-CH3 with strong coordination ability and a -CN group with coordination ability.

[0011] In a preferred embodiment of the present invention, Z1 is a single bond or -CH2-, and -Z2-R is -S(=O)2CF3 or -S(=O)2-(CH2CH2O)3-CH3.

[0012] In a second aspect, the present invention also provides a method for preparing the above-mentioned cyanide-containing lithium salt.

[0013] The preparation method provided by the present invention comprises the following steps:

[0014] R-Z2-Cl is reacted with H2N-Z1-CN in the presence of potassium carbonate to obtain a potassium salt intermediate product, which is then dissolved in acetonitrile and lithium tetrafluoroborate is added to carry out a displacement reaction to obtain the target product.

[0015] In a preferred embodiment of the present invention, Z1 is a single bond, and -Z2-R is -S(=O)2CF3.

[0016] The preparation method may include the following steps: first, dissolving trifluoromethanesulfonyl chloride in acetonitrile / tetrahydrofuran-water, adding potassium carbonate after the sample is completely dissolved, and then stirring at room temperature. Nitrile amide is separately dissolved in acetonitrile / tetrahydrofuran and slowly added dropwise to the above solution after a homogeneous phase is formed. The reaction temperature is 10-25°C and the reaction time is 12-24 hours. After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain a potassium salt intermediate. Second, the intermediate product is dissolved in acetonitrile, and lithium tetrafluoroborate is added to carry out a displacement reaction to obtain the target product. The reaction temperature is 10-25°C and the reaction time is 3-8 hours.

[0017] In another preferred embodiment of the present invention, Z1 is -CH2- and -Z2-R is -S(=O)2CF3.

[0018] The preparation method may include the following steps: first, dissolving trifluoromethanesulfonyl chloride in acetonitrile / tetrahydrofuran-water, adding potassium carbonate after the sample is completely dissolved, and then stirring at room temperature. Separately, dissolving aminoacetonitrile in acetonitrile / tetrahydrofuran and slowly adding it dropwise to the above solution after a homogeneous phase is formed, with a reaction temperature of 10-25°C and a reaction time of 12-24 hours. After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain a potassium salt intermediate. Second, dissolving the intermediate product in acetonitrile, adding lithium tetrafluoroborate, and conducting a displacement reaction to obtain the target product, with a reaction temperature of 10-25°C and a reaction time of 3-8 hours.

[0019] In another preferred embodiment of the present invention, Z1 is a single bond, and -Z2-R is -S(=O)2-(CH2CH2O)3-CH3.

[0020] The preparation method may include the following steps: first, dissolving a sulfonyl chloride structuring reagent in acetonitrile / tetrahydrofuran-water, adding potassium carbonate after the sample is completely dissolved, and then stirring at room temperature. Nitrile ammonia is separately dissolved in acetonitrile / tetrahydrofuran and slowly added dropwise to the above solution after a homogeneous phase is formed. The reaction temperature is 10-25°C and the reaction time is 12-24 hours. After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain a potassium salt intermediate. Second, the intermediate product is dissolved in acetonitrile, and lithium tetrafluoroborate is added to carry out a displacement reaction to obtain the target product. The reaction temperature is 10-25°C and the reaction time is 3-24 hours.

[0021] In a third aspect, the present invention provides a lithium battery electrolyte comprising the above-mentioned cyanide-containing lithium salt as a lithium salt electrolyte and / or additive.

[0022] That is, the above-mentioned cyanide-containing lithium salt is applied to lithium batteries and can be used as a lithium salt electrolyte of a lithium battery electrolyte, or as an additive of a lithium battery electrolyte, or as both a lithium salt electrolyte and an additive of a lithium battery electrolyte.

[0023] In some embodiments of the present invention, the cyanide-containing lithium salt is used only as an additive, and its usage is within 20% of the mass of the lithium battery electrolyte.

[0024] In some embodiments of the present invention, the lithium battery electrolyte further comprises a lithium salt electrolyte, an organic solvent, and an optional second additive. In other words, the inclusion of the cyanide-containing lithium salt as an additive does not exclude the inclusion of other components that can serve as additives in the electrolyte.

[0025] The lithium salt electrolyte is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0026] The organic solvent is one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, and methyltetrahydrofuran.

[0027] The second additive is one or more of lithium nitrate, lithium perchlorate, lithium sulfate, lithium carbonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0028] In some embodiments of the present invention, the cyanide-containing lithium salt is used at least as a lithium salt electrolyte, and its usage is 0.01-80% by mass of the lithium battery electrolyte.

[0029] In some embodiments of the present invention, the lithium battery electrolyte further comprises an organic solvent, an additive, and an optional second lithium salt electrolyte. In other words, the use of the cyanide-containing lithium salt as the lithium salt electrolyte does not exclude the inclusion of other components that can serve as lithium salt electrolytes in the electrolyte.

[0030] The organic solvent is one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, and methyltetrahydrofuran.

[0031] The additive is one or more of lithium nitrate, lithium perchlorate, lithium sulfate, lithium carbonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0032] The second lithium salt electrolyte is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0033] Furthermore, the present invention has found that, whether as a lithium salt electrolyte or an additive, when the cyanide-containing lithium salt is used in combination with lithium nitrate, the resulting electrolyte can further improve the performance of the battery.

[0034] In some embodiments of the present invention, the concentration of the lithium salt electrolyte in the electrolyte is 0.01 to 5 mol / L.

[0035] In some embodiments of the present invention, the additives in the electrolyte other than the cyanide-containing lithium salt account for less than 20% of the total mass of the electrolyte.

[0036] In a preferred embodiment of the present invention, the cyanide-containing lithium salt is used as an additive, the lithium salt electrolyte is lithium bis(fluorosulfonyl)imide, the organic solvent is ethylene glycol dimethyl ether, and the second additive is lithium nitrate.

[0037] In another preferred embodiment of the present invention, the cyanide-containing lithium salt is used as the lithium salt electrolyte, the organic solvent is ethylene glycol dimethyl ether and fluorinated ethylene carbonate, and the additive is lithium nitrate.

[0038] In a fourth aspect, the present invention provides a lithium battery comprising the lithium battery electrolyte containing a lithium cyanide salt. The lithium battery of the present invention is not limited in form and may be cylindrical, aluminum shell, plastic shell or soft package shell.

[0039] Furthermore, the lithium battery includes a positive electrode, a negative electrode and a separator placed between the positive electrode and the negative electrode. The positive electrode can be lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide or a ternary positive electrode material, preferably a ternary positive electrode material, such as LiNi x Co y Mn 1-x-y O2, wherein 0<x<1, 0<y<1, and x+y<1. The negative electrode is a lithium metal negative electrode or a graphite negative electrode. The separator is a polypropylene or polyethylene film.

[0040] The present invention provides a cyanide-containing lithium salt, a preparation method thereof, a lithium battery electrolyte, and a lithium battery. By utilizing the nitrogen atoms with coordination ability in the cyanide group to coordinate with the transition metal in the positive electrode material during the static and charging processes of the lithium battery, the positive electrode material is stabilized, the dissolution of the transition metal and the side reactions catalyzed by its active sites are inhibited, and the formation of the CEI film is indirectly optimized, thereby effectively passivating the positive electrode interface and improving the battery's high voltage resistance, cycle stability, and rate performance. This can further broaden the market for equipment with high requirements for fast charging and long cycle life of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The room temperature cycle rate diagram of the NCM811 / Li half-cell prepared in Example 1 and Comparative Example 1;

[0042] Figure 2 Graph showing the cycling performance of NCM811 / Li half-cells prepared in Example 1, Example 6, and Comparative Example 1;

[0043] Figure 3 The cycling performance diagram of the NCM811 / Li full battery prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] Unless otherwise specified, the technical means used in the embodiments of the present invention are conventional means well known to those skilled in the art.

[0046] The organic solvents, lithium salt electrolytes and additives used in the examples and comparative examples of the present invention are all of battery grade. The cyanide-containing lithium salt prepared in the present invention is subjected to multi-step purification and strict drying.

[0047] The electrolytes in the following examples were prepared in a glove box filled with 99.999% pure argon, with the water content of the glove box being less than 0.1 ppm and the temperature being room temperature.

[0048] Synthesis Example 1

[0049] This embodiment provides a cyanide-containing lithium salt, the structural formula of which is as follows:

[0050]

[0051] The preparation method is as follows:

[0052] In the first step, trifluoromethanesulfonyl chloride was dissolved in acetonitrile-water (10:1 volume ratio). Potassium carbonate was added after the sample was completely dissolved, and the mixture was stirred at room temperature. Nitrile amide was separately dissolved in acetonitrile and slowly added dropwise to the above solution after a homogeneous phase was formed. The reaction temperature was 25°C and the reaction time was 18 hours. After the reaction, the resulting mixture was filtered and the filtrate was rotary evaporated to obtain the potassium salt intermediate.

[0053] In the second step, the intermediate product was dissolved in acetonitrile and lithium tetrafluoroborate was added to carry out a displacement reaction to obtain the target product. The reaction temperature was 25°C and the reaction time was 5 hours. The specific reaction formula is as follows:

[0054]

[0055] The characterization data are as follows: 19 F-NMR (376MHz, DMSO) δ-78.00; C2F3N2O2S - HRMS (ESI, m / z) M - Theoretical value: 173.0898; tested value: 173.0868.

[0056] Synthesis Example 2

[0057] This embodiment provides a cyanide-containing lithium salt, the structural formula of which is as follows:

[0058]

[0059] The preparation method is as follows:

[0060] In the first step, trifluoromethanesulfonyl chloride was dissolved in acetonitrile-water (10:1 volume ratio). Potassium carbonate was added after the sample was completely dissolved, and the mixture was stirred at room temperature. Aminoacetonitrile was separately dissolved in acetonitrile and slowly added dropwise to the above solution after a homogeneous phase was formed. The reaction temperature was 25°C and the reaction time was 24 hours. After the reaction, the resulting mixture was filtered and the filtrate was rotary evaporated to obtain the potassium salt intermediate.

[0061] In the second step, the intermediate product was dissolved in acetonitrile and lithium tetrafluoroborate was added to carry out a displacement reaction to obtain the target product. The reaction temperature was 10°C and the reaction time was 6 hours. The specific reaction formula is as follows:

[0062]

[0063] The characterization data are as follows: 19 F-NMR (376 MHz, DMSO) δ -77.76; 1 H-NMR (400MHz, DMSO) δ2.07; C3H2F3N2O2S - HRMS (ESI, m / z) M - Theoretical value: 186.9795; tested value: 186.9765.

[0064] Synthesis Example 3

[0065] This embodiment provides a cyanide-containing lithium salt, the structural formula of which is as follows:

[0066]

[0067] The preparation method is as follows:

[0068] In the first step, the sulfonyl chloride reagent was dissolved in acetonitrile-water (10:1 volume ratio). Potassium carbonate was added after the sample was completely dissolved, and the mixture was stirred at room temperature. Aminoacetonitrile was separately dissolved in acetonitrile and slowly added dropwise to the above solution after a homogeneous phase was formed. The reaction temperature was 25°C and the reaction time was 24 hours. After the reaction, the resulting mixture was filtered and the filtrate was rotary evaporated to obtain the potassium salt intermediate.

[0069] In the second step, the intermediate product was dissolved in acetonitrile and lithium tetrafluoroborate was added to carry out a displacement reaction to obtain the target product. The reaction temperature was 25°C and the reaction time was 24 hours. The specific reaction formula is as follows:

[0070]

[0071] The characterization data are as follows: 1 H-NMR (400MHz, DMSO) δ3.84(t,2H),3.62-3.58(m,8H),3.37-3.35(m,5H); C3H2F3N2O2S - HRMS (ESI, m / z) M - Theoretical value: 251.0707; tested value: 251.0735.

[0072] Electrolyte Example 1

[0073] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (II), which is prepared as follows:

[0074] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, 36 g of the above-mentioned lithium salt compound (II), and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0075] Electrolyte Example 2

[0076] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (II), which is prepared as follows:

[0077] In an argon-filled glove box, 287 g of lithium bis(trifluoromethanesulfonyl)imide, 21 g of lithium perchlorate, 36 g of the above-mentioned lithium salt compound (II), and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0078] Electrolyte Example 3

[0079] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (II), which is prepared as follows:

[0080] In a glove box filled with argon, 180 g of the above-mentioned lithium salt compound (II), 14 g of lithium nitrate, and 1000 mL of tetraethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0081] Electrolyte Example 4

[0082] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (III), which is prepared as follows:

[0083] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, 39 g of the above-mentioned lithium salt compound (III), and 1000 mL of tetraethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0084] Electrolyte Example 5

[0085] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (IV), which is formulated as follows:

[0086] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, 52 g of the above-mentioned lithium salt compound (IV), and 1000 mL of tetraethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0087] Electrolyte Example 6

[0088] This embodiment provides a lithium battery electrolyte containing the above-mentioned cyanide-containing lithium salt compound (II), which is prepared as follows:

[0089] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 29 g of lithium difluorooxalatoborate, 36 g of the above-mentioned lithium salt compound (II), and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0090] Electrolyte Comparative Example 1

[0091] This comparative example provides a lithium battery electrolyte, which is formulated as follows:

[0092] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0093] Electrolyte Comparative Example 2

[0094] This comparative example provides a lithium battery electrolyte, which is formulated as follows:

[0095] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear and transparent solution was obtained.

[0096] Electrolyte Comparative Example 3

[0097] This comparative example provides a lithium battery electrolyte, which is formulated as follows:

[0098] In an argon-filled glove box, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, 36 g of 1-cyano-N,N-(dimethyl)ethylamine (DMAPN), and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0099] Electrolyte Comparative Example 4

[0100] This comparative example provides a lithium battery electrolyte, which is formulated as follows:

[0101] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 14 g of lithium nitrate, 36 g of lithium hexafluorophosphate, and 1000 mL of ethylene glycol dimethyl ether were added and stirred until a homogeneous, clear, and transparent solution was obtained.

[0102] Performance Testing

[0103] The electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then subjected to cycle performance tests as follows:

[0104] LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was used as the positive electrode, lithium sheet as the negative electrode, aluminum foil as the positive electrode current collector, and Celgard 2325 separator. Coin cell half-cells or full-cells were assembled in a glove box and tested after standing for 24 hours. At a constant temperature of 25°C, the battery was activated by charging and discharging three times between 3.0V and 4.3V at a rate of 1 / 5C. Subsequently, the battery was charged and discharged at different rates of 1 / 2C, 1C, 2C, 5C, and 10C. The capacity at different rates was tested and the capacity retention rate was calculated. The results are shown in Table 1 (half-cell); the charge and discharge cycle was carried out at a rate of 0.5C at room temperature and 25°C. The test results are shown in Table 2 (full cell).

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109]

[0110] Note: The capacity of Comparative Example 2 is 0, which means that the electrolyte cannot be circulated under high pressure due to poor oxidation resistance.

[0111] Figure 1 Figure 1 is a diagram of the room temperature rate performance of the NCM811 / Li half-cell prepared in Example 1 and Comparative Example 1; Figure 2 Graph showing the cycling performance of NCM811 / Li half-cells prepared in Example 1, Example 6, and Comparative Example 1; Figure 3 The graph shows the cycling performance of the NCM811 / Li full battery prepared in Example 1 and Comparative Example 1 at room temperature.

[0112] From Tables 1 to 2 and Figures 1 to 3 It can be seen that the capacity retention rate of the electrolyte prepared in the embodiment of the present invention is significantly better than that of the comparative example when the charge and discharge cycles are carried out at different rates at room temperature, indicating that the cyanide-containing lithium salt provided by the present invention can significantly improve the cycle stability of the battery and obtain excellent high rate and long cycle life. Figure 2 It can be seen from the results that the cyanide-containing lithium salt of the present invention is better when used in combination with lithium nitrate.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A lithium battery electrolyte, characterized in that: Contains lithium cyanide salts; The structural formula of the cyanide-containing lithium salt is as follows: 、 or ； The cyanide-containing lithium salt is used only as an additive, and its amount is within 20% of the mass of the lithium battery electrolyte; The lithium battery electrolyte further includes a lithium salt electrolyte, an organic solvent and an optional second additive; The lithium salt electrolyte is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate); The organic solvent is one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, and methyltetrahydrofuran; The second additive is lithium nitrate.

2. A lithium battery, characterized in that: Including the lithium battery electrolyte according to claim 1.

3. The lithium battery according to claim 2, characterized in that The lithium battery includes a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode.

4. The lithium battery according to claim 3, characterized in that The positive electrode is made of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide or a ternary positive electrode material; The negative electrode is a lithium metal negative electrode or a graphite negative electrode; The diaphragm is a polypropylene or polyethylene film.

5. The lithium battery according to claim 4, characterized in that The positive electrode is a ternary positive electrode material.

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