A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material and lithium-ion battery

Abstract

The present invention discloses a low-temperature chargeable and dischargeable lithium-ion battery negative electrode material and a lithium-ion battery, which belong to the field of electrochemical energy storage technology. The present invention uses bismuth metal as the negative electrode, uses an ether electrolyte that can withstand high pressure, and develops a new type of lithium-ion battery negative electrode material that can be charged and discharged under low temperature conditions. And use this material as the negative electrode, and use one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material as the positive electrode material to form a lithium-ion full battery. The lithium-ion battery negative electrode material and lithium-ion battery described in the present invention can be charged and discharged in the temperature range of ‑50°C to 60°C, and at the same time show a high charge and discharge specific capacity, and can be used as an energy storage device in high and low temperature fields. The bismuth metal described in the present invention is abundant in reserves and is green and environmentally friendly; the raw materials of the lithium-ion battery described in the present invention are low in price and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and more specifically to a low-temperature chargeable and dischargeable lithium-ion battery negative electrode material and a lithium-ion battery. Background Art

[0002] Currently, lithium-ion batteries are widely used in various fields, such as electric vehicles, portable electronic products, and power storage, due to their high energy density, high power density, and high cycle stability. The application of lithium batteries will inevitably encounter low temperature environments, especially in areas such as plateaus, deep seas, the poles, and near space that are in low temperature environments all year round. When in a low temperature environment, the ion transport kinetics in the battery will be significantly attenuated, causing a sharp drop in the battery's energy density, power density, and cycle life.

[0003] Commercial lithium-ion batteries generally use graphite as the negative electrode. However, in low temperature environments, metallic lithium is easily precipitated on the surface of the graphite negative electrode during discharge, which not only reduces the capacity of the battery, but also brings the risk of short circuit to the battery. At the same time, low temperature will increase the impedance of the solid electrolyte membrane formed on the graphite surface, and also make Li + The diffusion rate in graphite is reduced, so the graphite negative electrode cannot meet the current lithium-ion battery's stable operation requirements in low-temperature environments. Therefore, the development of a negative electrode material with excellent performance at low temperatures will hopefully promote the development of low-temperature rechargeable lithium-ion batteries.

[0004] Therefore, developing a lithium-ion battery negative electrode material that can be charged and discharged in a low-temperature environment, and thereby realizing a practical lithium-ion full battery that can be used in a low-temperature environment is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a low-temperature chargeable and dischargeable lithium-ion battery negative electrode material and a lithium-ion battery. The negative electrode material and the lithium-ion battery containing the negative electrode material can be reversibly charged and discharged in a temperature environment of -50°C to 60°C, and have excellent energy density and cycle stability.

[0006] The low-temperature chargeable and dischargeable lithium-ion battery provided by the present invention exhibits high ion conductivity within -50°C-60°C. Its working principle is mainly that during the charge and discharge process, Li + Repeated insertion and extraction between the positive and negative electrodes: During discharge, Li + It is extracted from the positive electrode, transferred in the electrolyte and then embedded in the negative electrode; the opposite is true during charging.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The invention discloses a negative electrode material for a lithium-ion battery capable of rapid charge and discharge at low temperature, comprising an active substance, a conductive agent and a binder, wherein the active substance is a single substance of bismuth metal.

[0009] Preferably, the mass ratio of the active material to the conductive agent and the binder is (6-9.6):(0.2-2):(0.2-2).

[0010] More preferably, the mass ratio of the active material to the conductive agent and the binder is 8:1:1. The beneficial effect is that this mass ratio fully ensures the conductivity and uniformity of the electrode material, while also ensuring a high unit loading of the active material.

[0011] Preferably, the conductive agent is one or more of SuperP, acetylene black, Ketjen black, conductive graphite, carbon nanotubes, graphene and carbon fiber.

[0012] More preferably, the conductive agent is SuperP.

[0013] The above preferred advantageous effects are that SuperP is inexpensive, using SuperP can significantly reduce costs, and it is one of the most widely used conductive agents in lithium-ion batteries and is easily available.

[0014] Preferably, the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose / sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, LA132 or gelatin.

[0015] More preferably, the binder is polyvinylidene fluoride.

[0016] The above preferred advantageous effects are that polyvinylidene fluoride is inexpensive and the use of polyvinylidene fluoride can significantly reduce the cost. In addition, polyvinylidene fluoride is one of the most widely used binders in lithium-ion batteries and is easily available.

[0017] Another object of the present invention is to provide a method for preparing the above-mentioned low-temperature and fast-chargeable lithium-ion battery negative electrode material, comprising the following steps:

[0018] S1. Weigh each raw material of the above negative electrode material and set aside;

[0019] S2. Grinding the bismuth metal element sufficiently to obtain an active substance;

[0020] S3. Add a conductive agent to the active material and continue to grind it thoroughly to mix it evenly to obtain a solid mixture;

[0021] S4. Add a binder to the solid mixture, and continue to grind it thoroughly to obtain a solid mixture of two;

[0022] S5. Adding a solvent to the solid mixture II, stirring thoroughly to mix well, to obtain a composite slurry;

[0023] S6: coating the composite slurry on the copper current collector, and vacuum drying to obtain the negative electrode material.

[0024] Preferably, the grinding time in steps S2-S5 is 30-120 min, the solvent in step S5 is N-methylpyrrolidone or deionized water, and the stirring time in step S5 is 4-12 h.

[0025] More preferably, the grinding time in steps S2-S5 is 30 minutes, and the stirring time in step S5 is 12 hours.

[0026] Compared with the prior art, the beneficial effect is that the grinding time of each step reaches 30 minutes or more, which can effectively improve the uniformity of the composite slurry, thereby improving the uniformity of the negative electrode material. The stirring time reaches 12 hours, which can also significantly improve the uniformity of the composite slurry, thereby improving the uniformity of the negative electrode material.

[0027] The present invention also provides a low-temperature chargeable and dischargeable lithium-ion battery

[0028] Preferably, the lithium-ion battery pack comprises the above-mentioned negative electrode material based on bismuth metal element

[0029] Preferably, the lithium-ion battery further comprises a positive electrode material, an electrolyte and a separator, and the electrolyte further comprises a lithium salt and an organic solvent.

[0030] Preferably, the positive electrode material is selected from lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), nickel cobalt manganese ternary material (NCM), nickel cobalt aluminum ternary material (NCA) and lithium titanate (Li4Ti5O 12 ) one or more.

[0031] More preferably, the positive electrode material is nickel-cobalt-manganese ternary material (NCM811).

[0032] The beneficial effect of using the above raw materials is that the NCM811 positive electrode material has better performance in a low temperature environment, and the full battery assembled using the positive electrode material also has better performance in a low temperature environment.

[0033] Preferably, the lithium salt is selected from at least one of LiTFSI, LiFSI, LiCF3SO3, LiPF6, LiClO4, LiNO3, LiBF4, LiDFOB and LiBOB;

[0034] The above preferred beneficial effect is that the above lithium salts are all lithium salts commonly used in lithium-ion battery electrolytes. The use of these lithium salts can significantly reduce costs and are easy to obtain.

[0035] The organic solvent is selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, 1,3-dioxolane, dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran;

[0036] The preferred beneficial effect is that the organic solvents are all ethers, which generally have a lower freezing point. The electrolyte prepared using these organic solvents has an even lower freezing point, which is beneficial to the charging and discharging of the battery in a low temperature environment.

[0037] Preferably, the diaphragm is one of polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyimide (PI), and glass fiber.

[0038] The above preferred beneficial effect is that the above diaphragm is a commonly used lithium-ion battery diaphragm, which is low in cost and easy to obtain.

[0039] Preferably, the lithium-ion battery is a button-type lithium-ion battery.

[0040] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The bismuth metal material described in the present invention is abundant in reserves, low in cost, and environmentally friendly, and is a promising active material for lithium-ion batteries.

[0042] 2. The bismuth metal electrode material and the lithium-ion battery based on the negative electrode material described in the present invention can be reversibly charged and discharged within a temperature range of -50°C to 60°C.

[0043] 3. The lithium-ion battery based on the bismuth metal active substance negative electrode material described in the present invention has the ability to work in extreme environments of high and low temperatures, and can be used in high-altitude areas, deep sea, space, and polar regions with harsh environments, showing important practical application significance.

[0044] 4. The preparation method of the present invention is simple to operate, has low production cost, mature technology, can be put into production without a large amount of capital and technical investment, and is relatively easy to industrialize. The negative electrode material based on bismuth metal and the lithium ion battery based on the negative electrode material have great application prospects in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0046] Figure 1 The charge and discharge voltage-specific capacity curve of the bismuth metal negative electrode of the present invention in a Bi||Li battery at a current density of 0.2C at room temperature 25°C;

[0047] Figure 2 The charge and discharge voltage-specific capacity curve of the bismuth metal negative electrode of the present invention in a Bi||Li battery at a current density of 0.2C at 60°C, 25°C, and -20°C;

[0048] Figure 3 The charge and discharge voltage-specific capacity curve of the Bi||NCM811 lithium ion battery of the present invention at a current density of 0.1C at room temperature of 25°C;

[0049] Figure 4 The charge and discharge voltage-specific capacity curves of the Bi||NCM811 lithium ion battery of the present invention at a current density of 0.1C at 60°C, 25°C, -20°C, -40°C, and -50°C, respectively. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Example 1

[0052] A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material comprises the following steps:

[0053] a. Weigh 100 mg of bismuth metal powder and grind it thoroughly for 30 min, then dry it at 60 ° C for 2 h to obtain a solid 1

[0054] b. Take 80 mg of solid 1, add 10 mg of superP, grind for 30 min, then add 10 mg of PVDF, and continue grinding for 30 min.

[0055] c. Add an appropriate amount of N-methylpyrrolidone as a solvent to the solid obtained in step b, and stir thoroughly for 12 hours to obtain a uniform negative electrode slurry.

[0056] d. The negative electrode slurry was coated on a copper current collector and dried in vacuum at 80°C to obtain a negative electrode 1.

[0057] The obtained negative electrode 1 is dense and uniform, does not slag, and does not fall off from the current collector.

[0058] Example 2

[0059] A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material comprises the following steps:

[0060] a. Weigh 100 mg of bismuth metal powder and grind it thoroughly for 30 min, then dry it at 60 ° C for 2 h to obtain a solid 2

[0061] b. Take 90 mg of solid 2, add 5 mg of super P, grind for 30 min, then add 5 mg of PVDF, and continue grinding for 30 min.

[0062] c. Add an appropriate amount of N-methylpyrrolidone as a solvent to the solid obtained in step b, and stir thoroughly for 12 hours to obtain a uniform negative electrode slurry.

[0063] d. The negative electrode slurry was coated on a copper current collector and dried in vacuum at 80°C to obtain negative electrode 2.

[0064] The obtained negative electrode 2 is dense and uniform, does not slag, and does not fall off from the current collector.

[0065] Example 3

[0066] A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material comprises the following steps:

[0067] a. Weigh 100 mg of bismuth metal powder and grind it thoroughly for 10 min, then dry it at 60 ° C for 2 h to obtain a solid 3

[0068] b. Take 80 mg of solid 3, add 10 mg of superP, grind for 10 min, then add 10 mg of PVDF, and continue grinding for 10 min.

[0069] c. Add an appropriate amount of N-methylpyrrolidone as a solvent to the solid obtained in step b, and stir thoroughly for 12 hours to obtain a uniform negative electrode slurry.

[0070] d. The negative electrode slurry was coated on a copper current collector and vacuum dried at 80°C to obtain negative electrode 3.

[0071] The surface of the obtained negative electrode 3 is rough and has obvious granularity, and some active materials fall off from the current collector.

[0072] Example 4

[0073] A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material comprises the following steps:

[0074] a. Weigh 100 mg of bismuth metal powder and grind it thoroughly for 10 min, then dry it at 60 ° C for 2 h to obtain a solid 4

[0075] b. Take 80 mg of solid 4, add 10 mg of superP, grind for 30 min, then add 10 mg of PVDF, and continue grinding for 30 min.

[0076] c. Add an appropriate amount of N-methylpyrrolidone as a solvent to the solid obtained in step b, and stir thoroughly for 4 hours to obtain a uniform negative electrode slurry.

[0077] d. The negative electrode slurry was coated on a copper current collector and dried in vacuum at 80° C. to obtain negative electrode 4.

[0078] The coating thickness of the obtained negative electrode 4 is uneven, and some active materials fall off from the current collector.

[0079] Example 5

[0080] Room temperature electrochemical performance test of negative electrode materials

[0081] The negative electrode 1 and the lithium sheet are assembled into a Bi||Li half-cell with a separator and an electrolyte, wherein the separator is a Celgard 2325 separator of a lithium-ion battery; the electrolyte is 1M LiTFSI dissolved in ethylene glycol dimethyl ether / 1,3-dioxolane (volume ratio 1:1), and 1% by mass of LiNO3 is added.

[0082] The battery was subjected to constant current charge and discharge test at room temperature 25°C, with a current density of 0.2C, where 1C = 385mA / g. The charge and discharge voltage-specific capacity curve of the bismuth metal negative electrode in the Bi||Li battery at a current density of 0.2C at room temperature 25°C was obtained; ( Figure 1 ). As can be seen from the figure, the negative electrode material has a capacity of about 369mAh / g after the first cycle of charge and discharge activation at 0.2C. After three cycles of discharge, the capacity can still be maintained at 99%.

[0083] Example 6

[0084] Conduct variable temperature electrochemical performance testing on negative electrode materials

[0085] The negative electrode 1 and the lithium sheet are assembled into a Bi||Li half-cell with a separator and an electrolyte, wherein the separator is a Celgard 2325 separator of a lithium-ion battery; the electrolyte is 1M LiTFSI dissolved in ethylene glycol dimethyl ether / 1,3-dioxolane (volume ratio 1:1), and 1% by mass of LiNO3 is added.

[0086] The battery was tested for constant current charge and discharge at 60℃, 25℃, and -20℃, respectively, with a current density of 0.2C, where 1C = 385mA / g. The charge and discharge voltage-specific capacity curves of the bismuth metal negative electrode in the Bi||Li battery at a current density of 0.2C at 60℃, 25℃, and -20℃ were obtained ( Figure 2 ). As can be seen from the figure, the discharge specific capacities of the Bi||Li battery based on bismuth metal anode at 60°C, 25°C, and -20°C are 266mAh / g, 369mAh / g, and 231mAh / g, respectively, indicating that the anode material can operate in a wide temperature range.

[0087] Example 7

[0088] Room temperature electrochemical performance test of Bi||NCM811 lithium-ion battery

[0089] The negative electrode 1 and the NCM811 positive electrode sheet were assembled into a Bi||NCM811 battery with a separator and an electrolyte, wherein the separator was a Celgard 2325 separator of a lithium-ion battery; the electrolyte was 1M LiTFSI dissolved in ethylene glycol dimethyl ether / 1,3-dioxolane (volume ratio 1:1), and 1% by mass of LiNO3 was added.

[0090] The battery was subjected to constant current charge and discharge test at room temperature 25°C, with a current density of 0.1C, where 1C = 188mA / g. The charge and discharge voltage-specific capacity curve of the Bi||NCM811 lithium-ion battery at room temperature 25°C at a current density of 0.1C was obtained ( Figure 3 ). As can be seen from the figure, the Bi||NCM811 lithium-ion battery has a capacity of about 140mAh / g at 0.1C, and after three cycles of discharge, the capacity can still be maintained at about 87%.

[0091] Example 8

[0092] Temperature-dependent electrochemical performance testing of Bi||NCM811 lithium-ion batteries

[0093] The negative electrode 1 and the NCM811 positive electrode sheet were assembled into a Bi||NCM811 battery with a separator and an electrolyte, wherein the separator was a Celgard 2325 separator of a lithium-ion battery; the electrolyte was 1M LiTFSI dissolved in ethylene glycol dimethyl ether / 1,3-dioxolane (volume ratio 1:1).

[0094] The battery was tested for constant current charge and discharge at room temperature (25°C) with a current density of 0.1C, where 1C = 188 mA / g. The electrolyte of the Bi||NCM811 lithium-ion battery decomposes during the charging process, indicating that LiNO3 can effectively increase the voltage window of the electrolyte.

[0095] Example 9

[0096] Temperature-dependent electrochemical performance testing of Bi||NCM811 lithium-ion batteries

[0097] The negative electrode 1 and the NCM811 positive electrode sheet were assembled into a Bi||NCM811 battery with a separator and an electrolyte, wherein the separator was a Celgard 2325 separator of a lithium-ion battery; the electrolyte was 1M LiTFSI dissolved in ethylene glycol dimethyl ether / 1,3-dioxolane (volume ratio 1:1), and 1% by mass of LiNO3 was added.

[0098] The battery was tested for constant current charge and discharge at 60℃, 25℃, -20℃, -40℃, and -50℃, respectively, with a current density of 0.1C, where 1C = 188mA / g. The charge and discharge voltage-specific capacity curves of the Bi||NCM811 lithium-ion battery at 60℃, 25℃, -20℃, -40℃, and -50℃ were obtained at a current density of 0.1C ( Figure 4 ). As can be seen from the figure, the discharge specific capacities of the Bi||NCM811 lithium-ion battery at 60°C, 25°C, -20°C, -40°C and -50°C are 93mAh / g, 140mAh / g, 102mAh / g, 73mAh / g and 38mAh / g, respectively. The Bi||NCM811 lithium-ion can be reversibly charged and discharged in a wide temperature range of -50°C to 60°C, showing application prospects in a wide temperature range environment.

[0099] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0100] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material, characterized in that: It includes an active material, a conductive agent and a binder, wherein the active material is a single substance of bismuth metal; The mass ratio of the active material to the conductive agent and the binder is (6-9.6): (0.2-2): (0.2-2); The conductive agent is one or more of SuperP, acetylene black, Ketjen black, conductive graphite, carbon nanotubes, graphene and carbon fiber; The binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose / sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate, LA132 or gelatin; The negative electrode material is prepared by the following method, which specifically comprises the following steps: S1. Weigh each raw material of the negative electrode material and set aside; S2. Grinding the bismuth metal element sufficiently to obtain an active substance; S3. Add a conductive agent to the active material and continue to grind it thoroughly to mix it evenly to obtain a solid mixture; S4. Add a binder to the solid mixture, and continue to grind it thoroughly to obtain a solid mixture of two; S5. Adding a solvent to the solid mixture II, stirring thoroughly to mix well, to obtain a composite slurry; S6. coating the composite slurry on a copper current collector, and vacuum drying to obtain the negative electrode material.

2. A low-temperature chargeable and dischargeable lithium-ion battery negative electrode material according to claim 1, characterized in that: The grinding time in steps S2-S5 is 30-120 min, the solvent in step S5 is N-methylpyrrolidone or deionized water, and the stirring time in step S5 is 4-12 h.

3. A low-temperature chargeable and dischargeable lithium-ion battery, characterized in that: Contains the negative electrode material according to claim 1 or 2.

4. A low-temperature chargeable and dischargeable lithium-ion battery according to claim 3, characterized in that: The lithium-ion battery also includes a positive electrode material, a separator and an electrolyte, and the electrolyte includes a lithium salt and an organic solvent.

5. A low-temperature chargeable and dischargeable lithium-ion battery according to claim 4, characterized in that: The positive electrode material is selected from one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, nickel-cobalt-manganese ternary material and nickel-cobalt-aluminum ternary material.

6. A low-temperature chargeable and dischargeable lithium-ion battery according to claim 5, characterized in that: The lithium salt is selected from at least one of LiTFSI, LiFSI, LiCF3SO3, LiPF6, LiClO4, LiNO3, LiBF4, LiDFOB and LiBOB; The organic solvent is selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, 1,3-dioxolane, dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran; 7. A low-temperature chargeable and dischargeable lithium-ion battery according to claim 6, characterized in that: The diaphragm is one of polyethylene, polypropylene, polyvinylidene fluoride, polyimide, and glass fiber; The lithium-ion battery is a button-type lithium-ion battery, a columnar lithium-ion battery or a soft-pack lithium-ion battery.

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