Fluorine-free electrolyte and preparation method and application thereof

Abstract

The invention discloses a fluoride-free electrolyte and a preparation method and application thereof, and belongs to the technical field of battery electrolytes.The fluoride-free electrolyte is composed of a fluoride-free organic solvent, a fluoride-free diluent and fluoride-free lithium salt. The fluoride-free electrolyte provided by the invention has a solvation structure rich in fluoride-free anions, a stable, uniform and compact inorganic interface layer rich in multiple components such as sulfur, boron, nitrogen, chlorine and the like can be formed under the induction of an electrode, and the interface stability is favorably improved, so that the cycle life of a lithium battery can be comparable with that of a fluorine-containing electrolyte. The fluoride-free electrolyte provided by the invention is low in cost and environment-friendly, and is beneficial to later environment-friendly recovery of the lithium battery.

Description

Technical Field

[0001] The invention belongs to the technical field of battery electrolytes, and in particular relates to a fluorine-free electrolyte and a preparation method and application thereof. Background Art

[0002] In various battery systems, lithium metal anodes with low reduction potentials (-3.040 V vs SHE) and transition metal oxide cathodes with higher oxidation potentials (>4.3 V vs Li + The high-voltage lithium battery system that matches Li / Li has a high theoretical energy density. However, in commercial carbonate electrolytes, lithium metal anodes are prone to lithium dendrites during repeated electroplating / stripping, which shortens the cycle life of the battery and poses a safety hazard to the battery. Commercial carbonate electrolytes will also undergo severe oxidation reactions at the cathode interface at higher oxidation potentials, and the reaction byproducts will increase the battery impedance and cause serious electrolyte loss. Therefore, the development of an electrolyte that is compatible with both lithium metal anodes and high-voltage cathodes is crucial for the stable cycle of high-voltage lithium battery systems.

[0003] Based on this situation, researchers have found that the electrolyte system using a local high concentration strategy has unique adaptability for high-voltage lithium battery systems. Local high concentration electrolytes usually refer to electrolytes that use diluents that do not participate in the lithium ion solvation structure to dilute high concentration electrolytes. In local high concentration electrolytes, a large amount of lithium salts are dissolved in the solvent to form a solvation structure of a high concentration lithium salt system, and then a diluent that does not participate in the lithium ion solvation structure is added to form a homogeneous system, which reduces the viscosity of the electrolyte while also improving its ionic conductivity. At present, researchers usually adopt a fluorination strategy for molecules such as lithium salts in local high concentration electrolytes, using the strong electron-withdrawing properties of fluorine atoms to reduce the highest occupied molecular orbital energy level (HOMO) of the system to improve the stability of the electrolyte to the high-voltage positive electrode; at the same time, the electrolyte components after fluorination also help to form a solid electrolyte interface phase (SEI) rich in lithium fluoride on the electrode surface, which can reduce the formation of lithium dendrites, reduce interfacial side reactions, and improve the cycle life of the lithium negative electrode. Patent CN117199535A discloses a high-voltage lithium metal battery electrolyte, which is a local high-concentration electrolyte, with one of lithium hexafluorophosphate, lithium bis(trifluoromethyl)sulfonyl imide, and lithium bis(fluorosulfonyl)imide as lithium salt, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, and perfluorobenzene as diluents, and 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, and 2,2-dimethyltetrahydrofuran as solvents, which can significantly reduce the viscosity of high-concentration electrolytes, improve the ionic conductivity of electrolytes, and solve the problem of poor wettability with diaphragms, and can be applied to high-voltage lithium metal batteries. However, the strategy of using fluorinated local high-concentration electrolytes usually involves fluorination of various components, such as lithium salts and diluents, to a high degree, which greatly increases the cost of the electrolyte, which can even reach 4 to 6 times that of commercial ester electrolytes; moreover, the fluorination strategy has serious defluorination and acidification phenomena under high temperatures and with active hydrogen impurities, which is easy to cause environmental damage. Therefore, there is an urgent need to develop a fluorine-free local high-concentration electrolyte to avoid the drawbacks of the existing fluorine-containing strategy, while ensuring that the lithium metal battery containing it can achieve high voltage, high power, high energy density and high stability applications. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a fluorine-free electrolyte and a preparation method and application thereof. The fluorine-free electrolyte described in the present invention is a local high-concentration electrolyte. The fluorine-free electrolyte described in the present invention adopts fluorine-free lithium salt, fluorine-free solvent and fluorine-free diluent, which greatly reduces the cost and avoids the defluorination acidification problem caused by fluorine element, improves stability and reduces harm to the environment; at the same time, the fluorine-free lithium salt effectively improves the ionic conductivity and the interface reaction rate, which is beneficial to improving the battery rate performance, and the electrolyte is conducive to establishing a stable lithium metal negative electrode interface and a high-voltage positive electrode interface, and is suitable for constructing a high-energy density, high-power battery system.

[0005] In a first aspect, the present invention provides a fluorine-free electrolyte comprising a fluorine-free lithium salt, a fluorine-free diluent and a fluorine-free organic solvent.

[0006] The fluorine-free electrolyte is used in lithium metal batteries, which improves its comprehensive performance and practical application capabilities while maintaining the advantages of traditional local high-concentration electrolyte systems. Compared with the fluorine content of commercial ester battery electrolytes, the overall fluorine content of the electrolyte is zero. The use of fluorine-free lithium salts in the present invention greatly reduces the amount of fluorine-containing lithium salts, while regulating and optimizing the lithium negative electrode solid electrolyte interface (SEI) and the high-voltage positive electrode electrolyte interface (CEI), producing inorganic phases doped with multiple elements such as sulfur, boron, nitrogen, and chlorine, improving the lithium ion conductivity of SEI and CEI, reducing interface impedance, increasing the interface reaction rate, inhibiting lithium dendrite growth and positive electrode interface side reactions, and establishing a stable lithium metal negative electrode interface and high-voltage positive electrode interface during the cycle. Since the electrolyte in the present invention greatly reduces the amount of expensive fluorination reagents, and uses mature industrial product-grade solvents and diluents, the cost of the electrolyte system is greatly reduced; the use of fluorine-free electrolytes reduces the risk of defluorination and acidification of electrolytes; from the perspective of the entire life cycle of the battery, the environmental hazards caused by fluorine-containing reagents are reduced.

[0007] As a preferred technical solution of the present invention, the fluorine-free lithium salt is any one of lithium perchlorate, lithium chloride, lithium sulfate, lithium nitrate, lithium bis(oxalatoborate), lithium tetranitrile borate, and lithium tricyanomethane, or a combination of at least two thereof; the fluorine-free lithium salt combination includes a combination of lithium nitrate and lithium bis(oxalatoborate), a combination of lithium nitrate and lithium perchlorate, or a combination of lithium bis(oxalatoborate) and lithium perchlorate.

[0008] As a preferred technical solution of the present invention, the fluorine-free organic solvent is any one of 1,3-dioxolane, tetraethylene glycol dimethyl ether, tetrahydropyran, 2-methyltetrahydropyran, and 2-n-propyltetrahydropyran, or a combination of at least two thereof; the fluorine-free organic solvent combination includes a combination of tetraethylene glycol dimethyl ether and tetrahydropyran, a combination of 2-methyltetrahydropyran and 2-n-propyltetrahydropyran, and a combination of tetrahydrofuran and 2-methyltetrahydrofuran.

[0009] As a preferred technical solution of the present invention, the fluorine-free diluent is any one of γ-valerolactone, 2-(ethylsulfonyl)propane, 1,3-dichloropropane, dichloroethane, 1,1,2-trichloroethane, clinodichlorobenzene, meta-dichlorobenzene, and 1,1-dichlorobutane, or a combination of at least two thereof; the fluorine-free diluent combination includes a combination of γ-valerolactone and 2-(ethylsulfonyl)propane, a combination of 2-(ethylsulfonyl)propane and 1,3-dichloropropane, a combination of dichloroethane and 1,1,2-trichloroethane, a combination of 1,1,2-trichloroethane and clinodichlorobenzene, a combination of clinodichlorobenzene and meta-dichlorobenzene, and a combination of meta-dichlorobenzene and 1,1-dichlorobutane.

[0010] As a preferred technical solution of the present invention, in the fluorine-free electrolyte, the total concentration of lithium salt is 0.5-3 mol / L, for example, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0011] As a preferred technical solution of the present invention, in the fluorine-free electrolyte, the ratio of the total molar amount of the lithium salt to the molar amount of the fluorine-free organic solvent is 1:(0.5-4), for example 1:0.5, 1:0.7, 1:0.9, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.1, 1:2.3, 1:2.5, 1:2.7, 1:2.9, 1:3.1, 1:3.3, 1:3.5, 1:3.7, 1:3.9 or 1:4, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0012] As a preferred technical solution of the present invention, in the fluorine-free electrolyte, the ratio of the total molar amount of the lithium salt to the molar amount of the fluorine-free diluent is 1:(0.3-10), for example 1:0.3, 1:0.7, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5 or 1:10, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0013] The invention provides a method for preparing a fluorine-free electrolyte. The method comprises: firstly dissolving a fluorine-free lithium salt in a fluorine-free solvent, and then adding a fluorine-free diluent to obtain the fluorine-free electrolyte.

[0014] The present invention provides a lithium metal battery, comprising a positive electrode, a negative electrode and an electrolyte between the positive electrode and the negative electrode, wherein the electrolyte of the lithium metal battery is the above-mentioned fluorine-free electrolyte; the positive electrode is made of a positive electrode active material, a binder and conductive carbon black, wherein the positive electrode active material is one of lithium iron phosphate, lithium cobaltate, lithium manganate, and lithium cobalt nickel manganate; the negative electrode is a lithium metal negative electrode or is made of a negative electrode active material, a binder and conductive carbon black, wherein the negative electrode active material is one of graphite, lithium titanate, and vanadium pentoxide; the binder is polyvinylidene fluoride (PVDF), cellulose or polyethylene oxide.

[0015] Beneficial effects:

[0016] 1) The fluorine-free electrolyte disclosed in the present invention is prepared by using fluorine-free lithium salt, fluorine-free solvent and fluorine-free diluent, and there is no fluorine in the system, and the cost is much lower than the traditional fluorine-containing electrolyte;

[0017] 2) The fluorine content of the fluorine-free electrolyte of the present invention is zero, and no defluorination occurs, which can effectively improve the stability of the battery and reduce the harm to the environment and human health;

[0018] 3) The fluorine-free lithium salt introduced in the present invention regulates and optimizes the lithium negative electrode SEI and the high-voltage positive electrode CEI, improves the conductivity and interface reaction rate, reduces the interface impedance, effectively inhibits the growth of lithium dendrites and the side reaction at the positive electrode interface, and establishes a stable lithium metal negative electrode interface and a high-voltage positive electrode interface during the cycle process; at the same time, the use of a diluent reduces the anion solvation strength of lithium ions, reduces the excessive consumption of anions, and reaches or exceeds the corresponding indicators of commercial ester electrolytes in a wide temperature range;

[0019] 4) The fluorine-free solvent and fluorine-free diluent used in the present invention have a high electrochemical stability window, which can improve the positive electrode interface stability of the electrolyte in a high-voltage lithium metal battery without adopting a fluorination strategy.

[0020] 5) The present invention also discloses a method for preparing a fluorine-free electrolyte. The preparation process of the present invention is simple, the raw materials used are low-cost, and it is suitable for large-scale production. It provides a new idea for the development of fluorine-free electrolytes, can achieve fluorine-free lithium metal batteries, and can provide technical support for the environmentally friendly recycling of waste batteries in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a physical picture of the fluorine-free electrolyte prepared in Example 1;

[0022] Figure 2 A schematic diagram of a typical solvation structure of the fluorine-free electrolyte prepared in Example 1;

[0023] Figure 3The impedance spectrum of the Li||Li symmetric battery with fluorine-free electrolyte prepared in Example 2;

[0024] Figure 4 The rate performance test results of the Li||Li symmetric battery with the fluorine-free electrolyte prepared in Example 3;

[0025] Figure 5 Li||LFP (loading 10 mg cm) prepared by the fluorine-free electrolyte of Example 4 -2 )’s cycle performance test results;

[0026] Figure 6 Li||NCM622 (loading 10 mg cm) prepared by using the fluorine-free electrolyte of Example 5 -2 )’s cycle performance test results. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further illustrated by specific implementation methods below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0028] Example 1

[0029] The actual picture of the local fluorine-free electrolyte prepared in this embodiment is as follows Figure 1 As shown, after dissolving the fluorine-free lithium salt in the fluorine-free solvent, a transparent and uniform high-concentration electrolyte is formed, and then a fluorine-free diluent is added and stirred evenly to obtain the fluorine-free electrolyte.

[0030] The local high concentration electrolyte is obtained according to the following preparation method:

[0031] (1) dissolving battery-grade lithium borate oxalate (LiBOB) in anhydrous tetraethylene glycol dimethyl ether solvent by vigorous stirring to form a transparent and uniform high-concentration electrolyte, wherein the molar ratio of lithium salt to solvent is 2:1.5;

[0032] (2) Anhydrous γ-valerolactone (γ-VL) diluent is added to the above-mentioned high-concentration electrolyte, wherein the molar ratio of lithium salt to diluent is 8:3.6, and the mixture is stirred evenly to obtain a fluorine-free electrolyte, wherein the total concentration of lithium salt is 2 mol / L (25° C.), such as Figure 2 This is a typical solvation structure of the electrolyte. The room temperature ionic conductivity of the electrolyte is 2.4 mS cm -1 , the electrochemical window can reach 4.9V.

[0033] The fluorine-free lithium-ion battery was prepared using the fluorine-free electrolyte prepared in Example 1:

[0034] ① Preparation of lithium iron phosphate electrode:

[0035] Weigh 0.1 g of polyvinylidene fluoride and dissolve it in 2.6 g of N-methylpyrrolidone, slowly add 0.1 g of conductive carbon black, stir at room temperature for 2 h, then add 1.5 g of lithium iron phosphate, continue stirring for 3 h and let stand for 0.5 h, apply the slurry on aluminum foil, and air dry it at 80 ° C for 3 h, then vacuum dry it at 120 ° C for 12 h, and cut it to obtain a small disc with a diameter of 12 mm, which is the lithium iron phosphate electrode, which is used as the positive electrode;

[0036] ② Stack the positive electrode, fluorine-free electrolyte, and lithium metal negative electrode in a sandwich structure and package them to prepare a fluorine-free lithium battery.

[0037] The Li||LFP battery (the mass of the lithium iron phosphate positive electrode active material is 10 mg cm) assembled with the electrolyte in Example 1 -2 ) The battery cycle performance test shows that the specific capacity reaches 165mAh g at 0.2C -1 .

[0038] Example 2

[0039] This embodiment provides a fluorine-free electrolyte, and the local high-concentration electrolyte is obtained according to the following preparation method:

[0040] (1) dissolving battery-grade lithium perchlorate and lithium nitrate (molar ratio of 10:1) in a 1,3-dioxolane solvent by vigorous stirring to form a transparent and uniform high-concentration electrolyte, wherein the molar ratio of lithium salt to solvent is 1:3;

[0041] (2) Anhydrous dichloroethane diluent was added to the above high concentration electrolyte, wherein the molar ratio of lithium salt to diluent was 1:6, and the fluorine-free electrolyte was obtained after stirring evenly, wherein the total concentration of lithium salt was 2.5 mol / L (25°C). The room temperature ionic conductivity of the electrolyte was 3.2 mS cm -1 , the electrochemical window can reach 4.8V.

[0042] Figure 3 This is the impedance spectrum of the fluorine-free electrolyte prepared in Example 2. It can be seen that the impedance of the Li||Li symmetric battery (lithium symmetric battery) based on the fluorine-free electrolyte is 150Ω.

[0043] Li||LFP (loading 10 mg cm) assembled with the electrolyte in Example 2 -2 ) The battery cycle performance test at 0.5C specific capacity reached 150mAh g -1 , and can stably cycle 500 times.

[0044] Example 3

[0045] This embodiment provides a fluorine-free electrolyte, which is prepared according to the following preparation method:

[0046] (1) Battery grade lithium borate oxalate (LiBOB) and lithium sulfate (Li 2 SO 4 ) (the molar ratio of the two lithium salts is 8:1) is dissolved in anhydrous 2-methyltetrahydropyran solvent by vigorous stirring to form a transparent and uniform fluorine-free high-concentration electrolyte, wherein the molar ratio of the lithium salt to the solvent is 1:1.4;

[0047] (2) Anhydrous 1,1,2-trichloroethane diluent was added to the above high-concentration electrolyte, wherein the molar ratio of lithium salt to diluent was 1:6, and stirred evenly to obtain a fluorine-free high-entropy electrolyte, wherein the total concentration of lithium salt was 3 mol / L (25°C). The room temperature ionic conductivity of the electrolyte was 2.5 mS cm -1 , the electrochemical window can reach 5.1V.

[0048] Figure 4 The time-voltage curve of the Li||Li symmetric battery with fluorine-free electrolyte prepared in Example 3 shows lower polarization and no battery short circuit occurs.

[0049] Example 4

[0050] This embodiment provides a fluorine-free electrolyte, which is prepared according to the following preparation method:

[0051] (1) dissolving battery-grade lithium tetranitrile borate in an anhydrous 2-n-propyltetrahydropyran solvent by vigorous stirring to form a transparent and uniform fluorine-free high-concentration electrolyte, wherein the molar ratio of lithium salt to solvent is 2:1;

[0052] (2) Anhydrous 1,3-dichloropropane diluent was added to the above-mentioned fluorine-free high-concentration electrolyte, wherein the molar ratio of lithium salt to diluent was 1:8, and the fluorine-free electrolyte was obtained after being stirred evenly, wherein the total concentration of lithium salt was 3.5 mol / L (25°C). The room temperature ionic conductivity of the electrolyte was 1.5 mS cm -1 , the electrochemical window can reach 4.7V.

[0053] Figure 5 Li||LFP (loading 10 mg cm) prepared by the fluorine-free electrolyte of Example 4 -2 )'s cycle performance test results, such as Figure 5 The battery can be stably cycled for 200 cycles at room temperature with an average capacity of 170 mAh g -1 .

[0054] Example 5

[0055] This embodiment provides a fluorine-free electrolyte, which is prepared according to the following preparation method:

[0056] (1) dissolving battery-grade lithium tricyanomethane in anhydrous 1,3-dioxolane and tetraethylene glycol dimethyl ether solvents by vigorous stirring to form a transparent and uniform fluorine-free high-concentration electrolyte, wherein the molar ratio of lithium salt to solvent is 2:1.24;

[0057] (2) Anhydrous grade 2-(ethylsulfonylpropane) diluent was added to the above fluorine-free high concentration electrolyte, wherein the molar ratio of lithium salt to diluent was 1:8, and the fluorine-free electrolyte was obtained after stirring evenly, wherein the total concentration of lithium salt was 4 mol / L (25°C). The room temperature ionic conductivity of the electrolyte was 4.3 mS cm -1 , the electrochemical window can reach 5.0V.

[0058] The fluorine-free lithium-ion battery was prepared using the fluorine-free electrolyte prepared in Example 5:

[0059] ① Preparation of lithium cobalt oxide electrode:

[0060] Weigh 0.1g of polyethylene oxide and dissolve it in 2.6g of N-methylpyrrolidone, slowly add 0.1g of conductive carbon black, stir at room temperature for 2h, then add 1.8g of lithium cobalt oxide, continue stirring for 3h and let stand for 0.5h, scrape the slurry on aluminum foil, and air dry it at 80℃ for 3h, then vacuum dry it at 120℃ for 12h, and prepare small discs with a diameter of 12mm by cutting, which are lithium cobalt oxide electrodes, and use them as positive electrodes.

[0061] ② Weigh 0.1g of polyethylene oxide and disperse it in 2.6g of N-methylpyrrolidone, slowly add 0.1g of conductive carbon black, stir at room temperature for 2h, then add 1.8g of lithium titanate, continue stirring for 3h and let stand for 0.5h, apply the slurry on copper foil, and air dry it at 80℃ for 3h, then vacuum dry it at 120℃ for 12h, and prepare small discs with a diameter of 12mm by cutting, which are lithium titanate electrodes, and use them as negative electrodes.

[0062] ③ Stack the positive electrode, fluorine-free electrolyte, and negative electrode in a sandwich structure and package them to prepare a fluorine-free lithium battery.

[0063] Figure 6 The Li||NCM622 battery (the mass of the positive electrode active material of lithium nickel cobalt oxide 622 is 10 mg cm) prepared by the fluorine-free electrolyte of Example 5 -2 )'s cycle performance test results, such as Figure 6 The battery can be stably cycled for 200 cycles at room temperature with an average capacity of 175 mAh g -1 .

[0064] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A fluorine-free electrolyte, characterized in that: The fluorine-free electrolyte consists of a fluorine-free lithium salt, a fluorine-free organic solvent and a fluorine-free diluent.

2. The fluorine-free electrolyte according to claim 1, characterized in that The fluorine-free lithium salt is any one of lithium perchlorate, lithium chloride, lithium sulfate, lithium nitrate, lithium bis(oxalato)borate, lithium tetranitrile borate and lithium tricyanomethane, or a combination of several of them.

3. The fluorine-free electrolyte according to claim 2, characterized in that: The fluorine-free organic solvent is any one of 1,3-dioxolane, tetraethylene glycol dimethyl ether, tetrahydropyran, 2-methyltetrahydropyran, and 2-n-propyltetrahydropyran, or a combination of several thereof.

4. The fluorine-free electrolyte according to claim 3, characterized in that The fluorine-free diluent is any one of γ-valerolactone, 2-(ethylsulfonyl) propane, 1,3-dichloropropane, dichloroethane, 1,1,2-trichloroethane, ortho-dichlorobenzene, meta-dichlorobenzene, and 1,1-dichlorobutane, or a combination of several of them.

5. The fluorine-free electrolyte according to any one of claim 4, characterized in that: In the fluorine-free electrolyte, the concentration of the fluorine-free lithium salt is 0.5 to 3 mol / L.

6. The fluorine-free electrolyte according to claim 5, characterized in that In the fluorine-free electrolyte, the molar ratio of the fluorine-free lithium salt, the fluorine-free solvent, and the fluorine-free diluent is 1:(0.5-4):(0.3-10).

7. A method for preparing a fluorine-free electrolyte according to any one of claims 1 to 6, characterized in that: The preparation method comprises: Firstly, a fluorine-free lithium salt is dissolved in a fluorine-free solvent, and then a fluorine-free diluent is added to obtain the fluorine-free electrolyte.

8. A lithium metal battery, comprising a positive electrode, a negative electrode and an electrolyte between the positive electrode and the negative electrode, characterized in that: The electrolyte is the fluorine-free electrolyte according to any one of claims 1 to 6; The positive electrode is made of a positive electrode active material, a binder and conductive carbon black, wherein the positive electrode active material is one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and cobalt nickel lithium manganese oxide; The negative electrode is a lithium metal negative electrode or is made of a negative electrode active material, a binder and conductive carbon black, wherein the negative electrode active material is one of graphite, lithium titanate and vanadium pentoxide; The binder is polyvinylidene fluoride, cellulose or polyethylene oxide.

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