Foamy copper-based lithium ion battery negative electrode material as well as preparation method and application thereof

Abstract

The invention provides a foamy copper-based lithium ion battery negative electrode material as well as a preparation method and application thereof. The lithium ion battery negative electrode material comprises foamy copper and an active substance, the active substance comprises a carbon nanotube and a silicon-based material, and the mass ratio of the foamy copper to the carbon nanotube to the silicon-based material is (10-20): (0.1-0.2): 1. The foamy copper is used as a matrix, the carbon nano tube and the silicon-based material are used as active substances, and the porosity and the average pore size of the foamy copper are regulated and controlled, so that the binding capacity of the foamy copper matrix, the active substances and lithium metal is improved, and meanwhile, the loading capacity of the active substances is improved. The lithium metal battery assembled by adopting the negative electrode material can obtain excellent cycling stability, first discharge specific capacity and rate capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a kind of foam copper-based lithium ion battery negative material and its preparation method and application. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic devices, electric vehicles and large-scale energy storage due to their high energy density, long cycle life and no memory effect. As a key component of lithium ion batteries, the performance of negative electrode material plays a decisive role in the overall performance of the battery. At present, the commercialized lithium ion battery negative material is mostly graphite, but the theoretical specific capacity of graphite negative electrode is relatively low, only 372 mAh / g, which cannot meet the growing demand for high energy density batteries.

[0003] To improve the energy density and comprehensive performance of lithium ion batteries, researchers continue to explore new negative materials. Like metal oxides, alloy-based negative materials, although they have high theoretical specific capacity, they will experience significant volume changes during charging and discharging, which will damage the material structure and reduce the cycle stability. Therefore, it is of great practical significance to develop a new type of lithium ion battery negative material with high specific capacity, good cycle stability and rate performance.

[0004] Foam copper has a three-dimensional network porous structure, showing high specific surface area, good electrical conductivity and excellent mechanical properties. Using foam copper as a substrate to construct lithium ion battery negative material can provide a fast channel for lithium ion transport, alleviate the volume change of electrode material during charging and discharging, and thus improve the battery performance. However, there are still some problems in the current research on foam copper-based lithium ion battery negative material, such as insufficient adhesion between electrode material and foam copper substrate, low active material loading, etc., which restricts its practical application. In addition, the active lithium metal negative electrode will react with the electrolyte to form an unstable solid electrolyte interface (SEI), which will adversely affect the rate performance and stability of lithium batteries.

[0005] Therefore, how to develop a foam copper-based lithium ion battery negative material, which combines foam copper as a substrate with electrode material and simultaneously loads high content of active material, to prepare a lithium ion battery with high specific capacity, good cycle stability and rate performance, is a problem to be solved in the present application. SUMMARY

[0006] The present application aims to provide a kind of foam copper-based lithium ion battery negative material and its preparation method and application, to solve the problems of low specific capacity, poor cycle stability and insufficient adhesion between electrode material and substrate of existing lithium ion battery negative material.

[0007] In one aspect, a foamed copper-based lithium-ion battery negative electrode material is provided, the foamed copper-based lithium-ion battery negative electrode material comprising foamed copper and an active material, the active material comprising carbon nanotubes and a silicon-based material, the mass ratio of the foamed copper, carbon nanotubes and silicon-based material being (10-20):(0.1-0.2):1.

[0008] As a further improvement, the method for preparing the foamed copper comprises the following steps:

[0009] S2-1: uniformly mixing copper powder with a pore-forming agent, adding water to form a mixture, then pressing the mixture to form a blank and drying the blank;

[0010] S2-2: sintering the dried blank under a nitrogen atmosphere, raising the temperature at a rate of 5-10°C / min to 800-900°C and maintaining the temperature for 1-3h to obtain a sintered blank;

[0011] S2-3: immersing the sintered blank in flowing water for 30-60min, removing the water from the blank by centrifugation and drying the blank to obtain foamed copper.

[0012] As a further improvement, the pore-forming agent in step S2-1 comprises one or more of anhydrous calcium chloride, sodium chloride and potassium carbonate.

[0013] As a further improvement, the particle size of the copper powder in step S2-1 is 2-5μm, and the volume ratio of the copper powder to the pore-forming agent is 1:(0.25-0.5).

[0014] As a further improvement, the carbon nanotubes have a tube diameter of 10-30nm and a length of 1-10μm.

[0015] As a further improvement, the method for preparing the silicon-based material comprises the following steps:

[0016] S6-1: mixing silicon nanoparticles and acrylamide in deionized water, stirring the mixture at room temperature to form a uniform A solution;

[0017] S6-2: adding an initiator and a crosslinking agent to water, stirring the mixture to form a uniform B solution, adding the B solution dropwise to the A solution to form a solution C, and then adding 1-3 drops of a promoter to the solution C to form an intermediate;

[0018] S6-3: annealing the intermediate in an argon environment at a rate of 2-5°C / min to a temperature of 500-600°C for 1-5h to obtain a silicon-based material.

[0019] As a further improvement, the initiator is ammonium persulfate, the crosslinking agent is N,N'-methylenebisacrylamide, and the promoter is tetramethylethylenediamine.

[0020] In another aspect, the present application also provides a preparation method of a foamed copper-based lithium ion battery negative electrode material, comprising the following steps:

[0021] S8-1: Cut the foamed copper into the required size, and then sequentially clean it with deionized water and anhydrous ethanol for 15-30 min; put the cleaned foamed copper into a hydrochloric acid solution with a mass fraction of 5%-10% for immersion for 5-10 min; finally, rinse it with deionized water until it is neutral, and dry it with nitrogen to obtain the pretreated foamed copper for standby;

[0022] S8-2: Weigh a certain amount of carbon nanotubes and silicon-based materials, and add them to deionized water containing sodium dodecyl benzene sulfonate, and ultrasonically disperse them for 30-60 min to obtain a dispersion liquid for standby;

[0023] S8-3: Soak the pretreated foamed copper in the dispersion liquid, and ultrasonically treat it for 10-20 min, then take out the treated material, and vacuum dry it at 60-80℃ for 12-24 h to obtain the foamed copper-based lithium ion battery negative electrode material.

[0024] As a further improvement, in step S8-3, the ultrasonic power in the ultrasonic treatment is 100-500 W, and the ultrasonic time is 30-60 min.

[0025] In addition, the present application provides a foamed copper-based lithium ion battery negative electrode material for use in a high-stability lithium ion battery.

[0026] The present application has the following advantages:

[0027] In the foamed copper-based lithium ion battery negative electrode material of the present application, the silicon-based material has a high theoretical specific capacity of up to 4200 mAh / g or more, which can provide more lithium ion storage sites, thereby significantly improving the specific capacity of the negative electrode material. The discharge platform of the silicon-based material is relatively low, and the potential is relatively close to that of lithium metal. This enables the silicon-based negative electrode material to output a relatively high voltage during battery discharge, thereby improving the overall performance and energy utilization efficiency of the battery. At a current density of 0.1 A / g, the initial discharge specific capacity can reach 1200-1500 mAh / g, which is much higher than that of traditional graphite negative electrode materials. The high conductivity of foamed copper and the presence of carbon nanotube networks provide a fast channel for the transmission of lithium ions and electrons, enabling the battery to maintain a relatively high capacity at a high current density.

[0028] The three-dimensional reticular porous structure of the foamed copper provides good support for the active material, can effectively alleviate the volume change of the silicon-based material in the charging and discharging process, and reduce the shedding and structure damage of the active material. Meanwhile, the network structure formed by the carbon nanotubes enhances the bonding force between the silicon-based material and the foamed copper matrix, and further improves the cycle stability of the overall electrode material. After 500 charging and discharging cycles, the capacity retention rate of the battery can still reach more than 85%.

[0029] The preparation method of the present application adopts conventional processes such as ultrasonic dispersion, is simple to operate, easy to control, low in cost, and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0030] The present application will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present application and are only used to illustrate the present application, but not to limit the present application. Other combinations and various modifications within the concept of the present application can be made without departing from the spirit or scope of the present application.

[0031] In the following examples, the compound monomers and related reagents used can be purchased from the market, wherein the commercial foamed copper is purchased from Kunshan Development Zone Yinghui Xiong Electronic Material Business Department; the nanoscale silicon is purchased from Shanghai Superwei Nanotechnology Co., Ltd., and the model number is CW-Si-001.

[0032] The following examples and comparative examples both include the following steps:

[0033] Preparation of foamed copper A-C:

[0034] The method for preparing foamed copper A includes the following steps:

[0035] S2-1: The copper powder with a particle size of 3 μm and anhydrous calcium chloride are mixed uniformly according to a mass ratio of 4:1, water is added to form a mixture, the copper powder and the anhydrous calcium chloride are fully mixed uniformly, then the mixture is pressed into a blank and dried to remove the water in the blank;

[0036] S2-2: The dried blank is placed in a nitrogen atmosphere and sintered at a temperature rising rate of 10 ℃ / min to 830 ℃ and kept for 3 h to obtain a sintered blank;

[0037] S2-3: The sintered blank is soaked in flowing water for 30 min, after the soaking is completed, the water in the blank is removed by centrifugation, and then dried to obtain foamed copper A.

[0038] The method for preparing foamed copper B and the raw materials are basically the same as those for preparing foamed copper A, and the difference lies in that in step S2-1, the copper powder with a particle size of 3 μm is replaced by copper powder with a particle size of 4 μm, and the anhydrous calcium chloride is replaced by sodium chloride, and the mass ratio of the copper powder with a particle size of 4 μm and the sodium chloride is 3:1.

[0039] The method and raw materials for preparing the foamed copper C are basically the same as those for preparing the foamed copper A, except that the copper powder with a particle size of 3 μm in step S2-1 is replaced by copper powder with a particle size of 5 μm, the anhydrous calcium chloride is replaced by potassium carbonate, and the mass ratio of the copper powder with a particle size of 5 μm to the potassium carbonate is 4:1.5.

[0040] Preparation of the silicon-based material D:

[0041] S6-1: 3 g of silicon nanoparticles with a particle size of 50 nm and 10 g of acrylamide were mixed in deionized water, and stirred at room temperature for 30 min to form a uniform A solution;

[0042] S6-2: ammonium persulfate and N,N'-methylenebisacrylamide were added to water and stirred to form a B solution, which was then added dropwise to the A solution to form a solution C, and then 2 drops of tetramethyl ethylenediamine were added dropwise to the solution C to form an intermediate substance;

[0043] S6-3: The intermediate substance was heated to 550°C at a heating rate of 5°C / min in an argon environment, and annealed for 3 h to obtain the silicon-based material D.

[0044] Preparation of a foamed copper-based lithium ion battery negative electrode material:

[0045] S8-1: The prepared foamed copper A-C was cut into a size of 5 cm x 5 cm, and then sequentially cleaned with deionized water and anhydrous ethanol under ultrasonic for 20 min; the cleaned foamed copper was immersed in a 5% hydrochloric acid solution for 10 min; finally, it was washed with deionized water until neutral, and dried with nitrogen to obtain a pretreated foamed copper for standby;

[0046] S8-2: Carbon nanotubes and 1 g of the silicon-based material D were weighed and added to 20 mL of deionized water containing 2 g of sodium dodecylbenzenesulfonate, and ultrasonically dispersed for 30-60 min to obtain a dispersion liquid for standby;

[0047] S8-3: The pretreated foamed copper was immersed in the dispersion liquid and ultrasonically treated for 15 min, and then the treated substance was taken out and vacuum dried at 70°C for 12 h to obtain a foamed copper-based lithium ion battery negative electrode material.

[0048] Example 1 provides a foamed copper-based lithium ion battery negative electrode material, which comprises foamed copper A and an active substance, the active substance comprising carbon nanotubes and a silicon-based material D, the carbon nanotubes having a tube diameter of 10 nm and a length of 5 μm, and the mass ratio of the foamed copper A, the carbon nanotubes and the silicon-based material D being 15:0.2:1.

[0049] Example 2 provides a foam copper-based lithium ion battery negative electrode material, which comprises foam copper B and an active material, the active material comprises carbon nanotubes and a silicon-based material D, the carbon nanotubes have a tube diameter of 15 nm and a length of 1 μm, and the mass ratio of the foam copper B, the carbon nanotubes and the silicon-based material D is 10:0.1:1.

[0050] Example 3 provides a foam copper-based lithium ion battery negative electrode material, which comprises foam copper C and an active material, the active material comprises carbon nanotubes and a silicon-based material D, the carbon nanotubes have a tube diameter of 15 nm and a length of 4 μm, and the mass ratio of the foam copper C, the carbon nanotubes and the silicon-based material D is 12:0.2:1.

[0051] Example 4 provides a foam copper-based lithium ion battery negative electrode material, the components and preparation method used are basically the same as those of Example 1, except that the foam copper A is replaced by a commercially available foam copper.

[0052] Example 5 provides a foam copper-based lithium ion battery negative electrode material, the components and preparation method used are basically the same as those of Example 1, except that the silicon-based material D is replaced by a nano-silicon.

[0053] Comparative Example 1 provides a foam copper-based lithium ion battery negative electrode material, the components and preparation method used are basically the same as those of Example 1, except that the mass ratio of the foam copper A, the carbon nanotubes and the silicon-based material D is 5:0.3:1.

[0054] The foam copper-based lithium ion battery negative electrode materials obtained in Examples 1-5 and Comparative Example 1 are prepared into lithium battery negative electrodes, and the electrochemical performance is tested and characterized, and the specific steps are as follows:

[0055] In an argon atmosphere glove box, the foam copper-based lithium ion battery negative electrode materials obtained in Examples 1-5 and Comparative Example 1 are cut into circular pieces with a diameter of 12 μm, and are stacked together with lithium metal pieces with a diameter of 12 μm and a thickness of 0.7 mm, the purity of the lithium metal pieces is greater than 99%, a tablet press is used to apply a pressure of 10 MPa until the negative electrode material is completely embedded in the lithium metal piece, the negative electrode material and the lithium metal piece are pressed together to obtain a foam copper / lithium metal composite electrode for standby.

[0056] The above-mentioned standby foam copper / lithium metal composite electrode is used as the negative electrode of a symmetrical battery, and a CR2032 button cell shell is used. Li / Cu button cells are assembled in an argon-filled glove box. The glove box is filled with argon, and the water and oxygen values are both 0.1 ppm. The assembled battery mainly consists of a positive electrode shell, a negative electrode shell, a positive electrode, a negative electrode, a separator, an electrolyte, and a stainless steel spring sheet and a stainless steel gasket. The assembly sequence is positive electrode shell / positive electrode / separator / negative electrode / stainless steel gasket / stainless steel spring sheet / negative electrode shell. The separator used is a PP separator, and the electrolyte is dropped on the separator to fully soak the separator. The electrolyte used is 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME)-based lithium bis(trifluoromethylsulfonate) imide (LiTFSI) electrolyte. The preparation method of the electrolyte is as follows: 1 mol of LiTFSI is dissolved in a mixed solution of 1 L of DOL and DME to prepare a premix, and then 2% of LiNO3 additive based on the total mass of the premix is added to prepare the electrolyte. The volume ratio of DOL:DME is 1:1.

[0057] Cycle capacity retention rate test: The above-prepared battery is placed on a new Wei machine for cycle performance test at a test temperature of 25°C; 1C charging to 4.5V and constant voltage charging to 0.05C static for 10 min, 1C discharging to 3.0V static for 10 min, and the discharge capacity obtained in this step is the initial capacity. The cycle test is carried out in this process, and the ratio of the discharge capacity of each cycle to the initial capacity is taken as the total coordinate, and the cycle number is taken as the horizontal coordinate to obtain the cycle performance curve, i.e. the cycle retention rate curve. The capacity retention rate after 500 cycles = (the discharge capacity of the 500th cycle / the discharge capacity of the first cycle) x 100%, and the 500-cycle cycle capacity retention rate is obtained by calculation.

[0058] First discharge specific capacity test: the charge and discharge cut-off voltage is 2V and 0.005V respectively, the test process is 0.1C discharging to 0.005V, 0.05C discharging to 0.005V, static for 10 min, 0.01C discharging to 0.005V, static for 10 min, and the first discharge capacity is recorded; 0.05C charging to 2.0V, static for 10 min, recording the first charge capacity, and the test process is repeated for 2 cycles. The first discharge specific capacity = the first discharge capacity / the mass of the negative electrode material.

[0059] Rate performance test: at a test temperature of 25 DEG C, the above-prepared battery is placed on a new Wei machine to perform rate performance test; 1C charging to 4.5V and constant voltage charging to 0.05C static 10 min, 0.2C discharging to 3.0V static 10 min, the discharge capacity obtained in this step is the initial capacity; 1C charging to 4.5V and constant voltage charging to 0.05C static 10 min, 2C discharging to 3.0V static 10 min, the discharge capacity obtained in this step is recorded as 2C capacity; 2C discharge rate = (2C discharge capacity / initial discharge capacity) x 100%, and the 2C discharge rate is obtained by calculation.

[0060] The test results are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] As can be seen from Examples 1-3, the foam copper-based lithium ion battery negative electrode material provided by the application uses foam copper as a carrier and skeleton, and carbon nanotubes and silicon-based materials as active materials, wherein the silicon-based materials are uniformly dispersed in the carbon nanotubes, and the mass ratio of the foam copper, carbon nanotubes and silicon-based materials is (10-20):(0.1-0.2):1. The lithium battery assembled in this way has high cycle stability, initial specific discharge capacity and rate performance.

[0065] As can be seen from the comparison between Example 1 and Examples 4-5, when the silicon-based material and the foam copper are prepared by the method provided by the application, the lithium battery assembled in this way has better cycle stability, initial specific discharge capacity and rate performance.

[0066] As can be seen from the comparison between Example 1 and Comparative Example 1, when the mass ratio of the foam copper, carbon nanotubes and silicon-based materials in the negative electrode material provided by the application is within a suitable range, the lithium battery assembled by the foam copper-based lithium ion battery negative electrode material provided by the application has stronger combination ability of the foam copper as the matrix with the active substances, i.e. the carbon nanotubes and the silicon-based materials, and higher loading capacity of the active substances. Therefore, the lithium battery assembled in this way has excellent cycle stability, initial specific discharge capacity and rate performance.

[0067] In summary, the application provides a foam copper-based lithium ion battery negative electrode material, a preparation method and application thereof. Foam copper is used as a matrix, and carbon nanotubes and silicon-based materials are used as active substances. By adjusting the porosity and average pore size of the foam copper, the combination ability of the foam copper matrix with the active substances and lithium metal is improved, and the loading capacity of the active substances is also improved. The lithium metal battery assembled by using the negative electrode material has excellent cycle stability, initial specific discharge capacity and rate performance.

[0068] The above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A foam copper-based lithium-ion battery negative electrode material, characterized in that: The copper foam-based lithium-ion battery negative electrode material comprises copper foam and an active substance, wherein the active substance comprises carbon nanotubes and a silicon-based material, and the mass ratio of the copper foam, the carbon nanotubes and the silicon-based material is (10-20): (0.1-0.2)：1。 2. The foam copper-based lithium-ion battery negative electrode material according to claim 1, characterized in that: The preparation method of the copper foam comprises the following steps: S2-1: Evenly mix the copper powder and the pore-forming agent, add water to form a mixture, and then press to form a blank and dry it; S2-2: sintering the dried blank in a nitrogen atmosphere at a heating rate of 5-10°C / min to 800-900°C and maintaining the temperature for 1-3 hours to obtain a sintered blank; S2-3: Soak the sintered blank in running water for 30-60 minutes. After soaking, remove the water by centrifugation and then dry to obtain foamed copper.

3. The foam copper-based lithium-ion battery negative electrode material according to claim 2, characterized in that: In step S2-1, the pore-forming agent comprises one or more of anhydrous calcium chloride, sodium chloride and potassium carbonate.

4. The foam copper-based lithium-ion battery negative electrode material according to claim 2, characterized in that: In step S2-1, the particle size of the copper powder is 2-5 μm, and the volume ratio of the copper powder to the pore-forming agent is 1: (0.25-0.5)。 5. The foam copper-based lithium-ion battery negative electrode material according to claim 1, characterized in that: The carbon nanotubes have a diameter of 10-30 nm and a length of 1-10 μm.

6. The foam copper-based lithium-ion battery negative electrode material according to claim 1, characterized in that: The method for preparing the silicon-based material comprises the following steps: S6-1: Silicon nanoparticles and acrylamide were mixed in deionized water and stirred at room temperature to form a uniform solution A; S6-2: Add the initiator and crosslinker to water and stir evenly to form solution B, which is then added dropwise to solution A to form solution C. Subsequently, 1-3 drops of accelerator are added dropwise to solution C to form an intermediate substance; S6-3: heating the intermediate material to 500-600° C. at a heating rate of 2-5° C. / min in an argon environment, and annealing for 1-5 hours to obtain a silicon-based material.

7. The foam copper-based lithium-ion battery negative electrode material according to claim 6, characterized in that: In step S6-2, the initiator is ammonium persulfate, the cross-linking agent is N,N'-methylenebisacrylamide, and the accelerator is tetramethylethylenediamine.

8. The method for preparing a foam copper-based lithium-ion battery negative electrode material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S8-1: Cut the copper foam into the required size, and then ultrasonically clean it with deionized water and anhydrous ethanol for 15-30 minutes in sequence; soak the cleaned copper foam in a 5%-10% hydrochloric acid solution for 5-10 minutes; finally rinse it with deionized water until it is neutral, and blow dry it with nitrogen to obtain the pretreated copper foam for use; S8-2: Weigh a certain amount of carbon nanotubes and silicon-based materials, add them to deionized water containing sodium dodecylbenzenesulfonate, and ultrasonically disperse them for 30-60 minutes to obtain a dispersion for later use; S8-3: Immerse the pretreated copper foam in the dispersion and ultrasonically treat it for 10-20 minutes. Then take out the treated material and vacuum dry it at 60-80°C for 12-24 hours to obtain a copper foam-based lithium-ion battery negative electrode material.

9. The method for preparing a foam copper-based lithium-ion battery negative electrode material according to claim 8, characterized in that: In step S8-3, the ultrasonic power during the ultrasonic treatment is 100-500 W, and the ultrasonic time is 30-60 min.

10. Use of the foam copper-based lithium ion battery negative electrode material according to any one of claims 1 to 7 in a high-stability lithium ion battery.

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