Composite metal lithium material, preparation method and application thereof, and composite metal lithium negative electrode

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a composite metal lithium material, a preparation method and application thereof and a composite metal lithium negative electrode. The composite metal lithium material comprises metal lithium, and lithium titanate and a carbon material which are dispersed in the metal lithium. The composite metal lithium negative electrode is prepared from the composite metal lithium material through hot pressing, lithium titanate and a carbon material serve as a lithium-loving supporting structure, the interface stability and the structural stability of the composite metal lithium negative electrode in the circulation process can be synergistically improved, and the advantage of high capacity of lithium metal is kept; and the problems of infinite volume change of the lithium metal negative electrode and uncontrollable growth of lithium dendrites are solved, so that the composite metal lithium negative electrode has excellent cycling stability. The preparation method of the composite metal lithium negative electrode has the advantages of being easy to operate and good in repeatability.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and specifically relates to a composite metal lithium material, a preparation method and application thereof, and a composite metal lithium negative electrode. Background Art

[0002] Lithium-ion batteries boast high specific energy and a high voltage platform, along with environmental friendliness and long cycle times. They are widely used in a wide range of fields, including portable medical devices and electric vehicles. Currently, most common lithium-ion batteries use graphite and its composite materials as negative electrodes. These batteries offer excellent electrochemical and cycling performance, but commercially available graphite negative electrodes have a relatively low specific capacity of only 372 mAh / g.

[0003] In recent years, with the rapid development of electronic devices and electric vehicles, people have placed higher demands on the battery life and high energy density of lithium-ion batteries. Lithium metal anodes, with their extremely high theoretical specific capacity of 3860 mAh / g and extremely low redox potential (-3.04 V relative to the standard hydrogen electrode), are considered to be the ideal anode material for next-generation high-energy-density lithium-ion batteries. However, the "host-less" nature and high reactivity of lithium metal lead to problems such as infinite volume change and uncontrolled growth of lithium dendrites during charge and discharge, resulting in rapid capacity decay and poor cycling stability of lithium-ion batteries. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a composite metal lithium material, a preparation method and application thereof, and a composite metal lithium negative electrode. The composite metal lithium material of the present invention is used to prepare a composite metal lithium negative electrode, and the assembled full battery has excellent cycle stability.

[0005] The present invention provides a composite metal lithium material, comprising metal lithium, and lithium titanate and carbon material dispersed in the metal lithium.

[0006] Preferably, the mass ratio of the metallic lithium to lithium titanate is 1:(0.1-10).

[0007] Preferably, the carbon material includes one or more of graphene, carbon fiber, carbon microspheres, graphite, soft carbon, hard carbon and carbon nanotubes.

[0008] Preferably, the mass ratio of the metallic lithium to the carbon material is 1:(0.1-10).

[0009] The present invention also provides a method for preparing the composite metal lithium material described in the above technical solution, comprising the following steps:

[0010] The carbon material, titanium dioxide and metallic lithium are mixed, melted and subjected to in-situ lithiation reaction to obtain the composite metallic lithium material.

[0011] Preferably, the mass ratio of the titanium dioxide, carbon material and metallic lithium is (0.1-10):(0.1-10):1.

[0012] Preferably, the carbon material, titanium dioxide and metallic lithium are mixed by pressing the carbon material and titanium dioxide into metallic lithium using a roller pressing method.

[0013] Preferably, the temperature of the in-situ lithiation reaction is 350-370° C., and the time is 10-20 minutes.

[0014] The present invention also provides the use of the composite metal lithium material described in the above technical solution or the composite metal lithium material obtained by the above preparation method in the negative electrode of a lithium battery.

[0015] The present invention also provides a composite metal lithium negative electrode, wherein the material of the composite metal lithium negative electrode is the composite metal lithium material described in the above technical solution or the composite metal lithium material obtained by the above preparation method;

[0016] The composite metal lithium negative electrode is in a thin sheet shape, and the thickness of the composite metal lithium negative electrode is 30 to 600 μm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a composite metal lithium material, comprising metal lithium, and lithium titanate and carbon material dispersed in the metal lithium.

[0019] The present invention uses lithium titanate and carbon materials as the lithium-philic support structure. Lithium titanate (LiTiO2) has a special crystal structure. + and Ti 3+ Alternating arrangement, this structure allows Li + Rapid movement can provide good ionic and electronic conductivity for the composite metal lithium negative electrode. Uniformly distributed lithium-philic lithium titanate can effectively regulate lithium ions so that they can be evenly distributed on the electrode, thereby achieving uniform lithium deposition and inhibiting the formation of lithium dendrites; the addition of carbon materials can improve the conductivity of lithium titanate materials, thereby making the composite metal lithium negative electrode have cycle stability under large currents. Lithium titanate and carbon materials synergistically improve the interfacial stability and structural stability of the composite metal lithium negative electrode during the cycle process, which not only maintains the advantage of high capacity of lithium metal, but also improves the problem of unlimited volume change of lithium metal negative electrode and uncontrollable growth of lithium dendrites. The assembled full battery has excellent cycle stability.

[0020] The present invention also provides a composite metal lithium negative electrode, the preparation process of which is easy to operate and has good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 SEM image of the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber, and metallic lithium is 0.5:0.3:1) prepared in Example 1;

[0023] Figure 2 Physical image of the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber, and metallic lithium is 0.5:0.3:1) prepared in Example 1;

[0024] Figure 3 Composition and distribution diagram of the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber, and metallic lithium is 0.5:0.3:1) prepared in Example 1;

[0025] Figure 4 Charge-discharge cycle comparison diagram at 1C of all-solid-state batteries assembled with the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber or carbon microsphere, and metallic lithium is 0.5:0.3:1, thickness 200μm) prepared in Example 1 and unmodified metallic lithium anode and lithium iron phosphate respectively;

[0026] Figure 5 Charge-discharge cycle comparison diagram at 0.5C of all-solid-state batteries assembled with the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber, and metallic lithium is 0.5:0.3:1, thickness 50μm) prepared in Example 2 and unmodified metallic lithium anode and lithium iron phosphate respectively;

[0027] Figure 6 Charge-discharge cycle comparison diagram at 1C of all-solid-state batteries assembled with the composite metal lithium anode (mass ratio of titanium dioxide, carbon fiber, and metallic lithium is 0.4:1:1, thickness 200μm) prepared in Example 3 and unmodified metallic lithium anode and ternary NCM811 respectively;

[0028] Figure 7 Charge-discharge cycle comparison diagram of all-solid-state batteries assembled with the composite metal lithium anode prepared in Example 1 and lithium iron phosphate at different rates;

[0029] Figure 8Charge-discharge cycle comparison diagrams of lithium iron phosphate full cells assembled with composite lithium metal anodes of different mass ratios at different rates. In the figure, Li-1 refers to a mass ratio of titanium dioxide, carbon fiber, and metallic lithium of 1:1:1, Li-2 refers to a mass ratio of titanium dioxide, carbon fiber, and metallic lithium of 0.5:0.3:1, Li-3 refers to a mass ratio of titanium dioxide, carbon fiber, and metallic lithium of 0.4:1:1, and Li-4 refers to a mass ratio of titanium dioxide, carbon fiber, and metallic lithium of 0.1:0.1:1. Detailed implementation mode

[0030] The present invention provides a composite metallic lithium material, comprising metallic lithium, and lithium titanate and carbon material dispersed in the metallic lithium.

[0031] In the present invention, unless otherwise specified, the materials and equipment used are all commercially available products in the art.

[0032] In the present invention, the carbon material preferably comprises one or more of graphene, carbon fiber, carbon microspheres, graphite, soft carbon, hard carbon, and carbon nanotubes; the graphite preferably comprises natural graphite and artificial graphite.

[0033] In the present invention, the mass ratio of the metallic lithium to the lithium titanate is preferably 1:(0.1-10).

[0034] In the present invention, the mass ratio of the metallic lithium to the carbon material is preferably 1:(0.1-10).

[0035] Using the composite metallic lithium material of the present invention to prepare a composite metallic lithium anode, lithium titanate (LiTiO2) has a special crystal structure, formed by the alternating arrangement of Li + and Ti 3+ This structure allows Li + to move quickly, and can provide good ionic and electronic conductivity for the composite metallic lithium anode. Lithium titanate and carbon material, as a lithiumophilic support structure, can synergistically improve the interfacial stability and structural stability of the composite metallic lithium anode during the cycling process, not only maintaining the advantages of high capacity of lithium metal, but also improving the problems of infinite volume change and uncontrollable growth of lithium dendrites of the lithium metal anode. The assembled full cell has excellent cycle stability.

[0036] The present invention also provides a preparation method of the composite metallic lithium material described in the above technical solution, comprising the following steps:

[0037] Mix the carbon material, titanium dioxide, and metallic lithium, and perform in-situ lithiation reaction by melting to obtain the composite metallic lithium material.

[0038] In the present invention, the carbon material is preferably a heat-treated carbon material, and the heat treatment preferably includes: soaking the carbon material in a strongly oxidizing solvent, followed by washing and drying. The strongly oxidizing solvent is preferably a mixed solution of concentrated nitric acid and concentrated hydrochloric acid, and the volume ratio of concentrated nitric acid to concentrated hydrochloric acid is preferably (1 to 10):(1 to 10), more preferably 1:1. The temperature of the soaking is preferably 100 to 120 °C, and the time is preferably 1 h. The washing is preferably water washing until neutral; the drying temperature is preferably 120 °C, and the time is preferably 16 h. The function of the heat treatment is to remove impurities on the surface of the carbon material and at the same time make the carbon material more likely to adsorb onto metallic lithium.

[0039] In the present invention, before mixing the carbon material, titanium dioxide and metallic lithium, it further includes: performing water treatment removal on the carbon material and titanium dioxide; the water treatment removal is preferably carried out in a vacuum atmosphere, and the temperature of the water treatment removal is preferably 100 to 120 °C, and the time is preferably 12 to 24 h.

[0040] In the present invention, the mass ratio of titanium dioxide, carbon material and metallic lithium is preferably (0.1 to 10):(0.1 to 10):1, more preferably (1 to 10):(1 to 10):1, and specifically can be 1:1:1, 0.5:0.3:1, 0.4:1:1 or 0.1:0.1:1. The mass ratio described in the present invention will not cause excessive titanium lithium oxide and carbon material, resulting in particle agglomeration on the surface of the composite metallic lithium anode, which is not conducive to the deposition and stripping of lithium metal; nor will there be too little titanium lithium oxide and carbon material, which is insufficient to form a framework structure.

[0041] In the present invention, the mixing of the carbon material, titanium dioxide and metallic lithium is preferably: by using a roll pressing method, pressing the carbon material and titanium dioxide into metallic lithium. The carbon material and titanium dioxide are both preferably in powder form, and the particle sizes of the carbon material and titanium dioxide are independently preferably 5 to 15 nm; the roll pressing is preferably carried out in a glove box filled with argon protection. During the pressing process, the lithiation reaction starts after titanium dioxide and metallic lithium come into contact.

[0042] In the present invention, the temperature of the in-situ lithiation reaction is preferably 350 to 370 °C, and the stirring time is preferably 10 to 20 min, more preferably 15 to 20 min; the in-situ lithiation reaction is preferably: stirring is carried out in a heated and molten state, and the present invention has no special requirements for the stirring rate. During the stirring process, titanium dioxide and lithium fully react to form lithium titanate, and at the same time, each component is mixed evenly. The in-situ lithiation reaction is preferably carried out in a glove box filled with argon protection.

[0043] The present invention also provides the application of the composite metallic lithium material described in the above technical solution or the composite metallic lithium material obtained by the above preparation method in a lithium battery anode.

[0044] The present invention constructs a composite metal lithium negative electrode with excellent lithiophilicity and conductivity, which can effectively guide the deposition of metal lithium, improve the stability of the lithium metal electrode / electrolyte interface, and improve the problems of lithium dendrites and infinite volume change of the lithium metal negative electrode, thereby obtaining a composite metal lithium negative electrode with excellent cycle stability.

[0045] The present invention also provides a composite metal lithium negative electrode, wherein the material of the composite metal lithium negative electrode is the composite metal lithium material described in the above technical solution or the composite metal lithium material obtained by the above preparation method;

[0046] The composite metal lithium negative electrode is in a thin sheet shape, and the thickness of the composite metal lithium negative electrode is 30 to 600 μm.

[0047] In the present invention, the thickness of the composite metal lithium negative electrode is preferably 50 to 200 μm, specifically 50 μm, 100 μm or 200 μm.

[0048] In the present invention, the composite metal lithium negative electrode is obtained by hot pressing the composite metal lithium material described in the above technical solution or the composite metal lithium material obtained by the above preparation method.

[0049] In the present invention, the temperature of the hot pressing is preferably 80-100° C., and the time is preferably 5 minutes. The hot pressing method used in the present invention is conducive to extending the composite metal lithium material into a composite metal lithium electrode with controllable thickness.

[0050] The present invention prepares a composite metal lithium negative electrode by melting and hot pressing titanium dioxide, carbon material and metallic lithium. The raw materials after melt mixing can be hot pressed to obtain a composite metal lithium negative electrode with controllable thickness. Among them, lithium-philic lithium titanate and carbon material with excellent conductivity synergistically improve the lithium dendrite and volume change problems of the metallic lithium negative electrode, thereby obtaining a composite metal lithium negative electrode with excellent rate performance and cycle stability.

[0051] In order to further illustrate the present invention, the composite metal lithium material, its preparation method and application, and the composite metal lithium negative electrode provided by the present invention are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] (1) Carbon fiber (or carbon microsphere) pretreatment: The carbon fiber (or carbon microsphere) was placed in 100 mL of a mixture of concentrated sulfuric acid and concentrated nitric acid (V:V = 1:1) and heat treated (immersed at 100 °C) for 1 h. After heat treatment, the carbon fiber (or carbon microsphere) was cooled to room temperature, washed with deionized water, and dried at 120 °C for 16 h.

[0054] (2) The carbon fiber (or carbon microspheres) obtained in step (1) and titanium dioxide are subjected to high-temperature drying treatment (120 °C, 12 h) in a vacuum atmosphere to obtain dried carbon fiber (or carbon microspheres) and dried titanium dioxide;

[0055] (3) The dried titanium dioxide, dried carbon fiber (or carbon microspheres), and lithium metal are mixed together in a mass ratio of 0.5:0.3:1 by using a roll pressing method;

[0056] (4) The mixture in step (3) is mixed and stirred at a molten state of 370 °C for 20 min to obtain a uniformly mixed composite lithium metal material;

[0057] (5) The composite lithium metal material in step (4) is hot-pressed (150 °C, 20 min) to obtain a composite lithium metal negative electrode with a thickness of 200 μm.

[0058] Figure 1 is the SEM image of the composite lithium metal negative electrode (mass ratio of titanium dioxide, carbon fiber, and lithium metal 0.5:0.3:1) prepared in Example 1; Figure 2 is the physical image of the composite lithium metal negative electrode (mass ratio of titanium dioxide, carbon fiber, and lithium metal 0.5:0.3:1) prepared in Example 1. From a microscopic perspective, the surface of the composite lithium metal negative electrode material becomes relatively rough due to the protrusion of LiTiO2 particles, and there is a close contact state between LiTiO2 and Li metal, and no cracks appear; from a macroscopic perspective, the surface is smooth and dense, without any cracks, meeting the physical properties of the lithium metal electrode sheet.

[0059] Figure 3 is the composition and distribution diagram of the composite lithium metal negative electrode (mass ratio of titanium dioxide, carbon fiber, and lithium metal 0.5:0.3:1) prepared in Example 1. It can be seen that C, O, and Ti elements are uniformly distributed in the composite lithium metal negative electrode.

[0060] Application Example 1

[0061] The composite lithium metal negative electrode prepared in Example 1 is cut into a circular piece with a diameter of 16 mm. Using it as the negative electrode, LFP (lithium iron phosphate) material as the positive electrode, and the lithium iron phosphate loading is 5 mg·cm -2 , a traditional commercial liquid electrolyte (battery grade, Guangzhou Tianci High-Tech Materials Co., Ltd.) and a commercial PE separator (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) are assembled into a button full cell. The above battery assembly is carried out in a glove box with water and oxygen contents both lower than 0.1 ppm.

[0062] The charge-discharge performance of the full cell is as Figure 4As shown, compared with the Li||LFP full battery constructed with a pure lithium sheet, the assembled LiTiO2 / carbon fiber||LFP full battery has an initial capacity of 149.09 mAh·g at 1C cycling. -1 After 350 cycles, the capacity is 131.45 mAh·g. -1 The capacity retention rate is 88.16%; for the assembled LiTiO2 / carbon microsphere||LFP full battery at 1C cycling, after 300 cycles, the capacity is 104 mAh·g. -1 The capacity retention rate is 71.72%; for the Li||LFP full battery constructed with a pure lithium sheet at 1C cycling, after 200 cycles, the capacity decay is 78.68 mAh·g. -1 The capacity retention rate is 55.11%. It can be seen that for the assembled LiTiO2 / carbon fiber||LFP full battery, the discharge specific capacity shows no obvious downward trend, and the long-cycle performance is more stable.

[0063] Example 2

[0064] (1) Carbon fiber pretreatment: Put the carbon fiber into a mixed solution of 100 mL of concentrated sulfuric acid and concentrated nitric acid (V:V = 1:1) for heat treatment (soak at 100 °C) for 1 h. After heat treatment, cool the carbon fiber to room temperature, wash it with deionized water, and dry it at 120 °C for 16 h;

[0065] (2) Subject the carbon fiber and titanium dioxide obtained in step (1) to high-temperature drying treatment (120 °C, 12 h) in a vacuum atmosphere to obtain dried carbon fiber and dried titanium dioxide;

[0066] (3) Use the roll pressing method to mix the dried titanium dioxide, dried carbon fiber, and metallic lithium together at a mass ratio of 0.5:0.3:1;

[0067] (4) Mix and stir the mixture in step (3) at a molten state of 370 °C for 20 min to obtain a uniformly mixed composite metallic lithium material;

[0068] (5) Subject the composite metallic lithium material in step (4) to hot pressing to obtain a composite metallic lithium negative electrode with a thickness of 50 μm.

[0069] Application Example 2

[0070] Cut the composite metallic lithium negative electrode prepared in Example 2 into circular pieces with a diameter of 16 mm. Use it as the negative electrode, LFP material as the positive electrode, and the LFP loading is 8 mg·cm. -2 Assemble it into a button full battery with a traditional commercial liquid electrolyte (battery grade, Guangzhou Tianci High-Tech Materials Co., Ltd.) and a commercial PE separator (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.). The assembly of the above batteries is carried out in a glove box with the water and oxygen content both lower than 0.1 ppm.

[0071] The charge-discharge performance of the full battery is as follows Figure 5 shown. Compared with the Li||LFP full battery constructed with pure lithium foil, the assembled LiTiO2 / carbon fiber||LFP full battery has an initial capacity of 162.08 mAh·g−1 at 0.5C cycling -1 −1, and the capacity is 154.51 mAh·g−1 after 80 cycles -1 −1, and the capacity retention rate is 95.32%; while for the Li||LFP full battery constructed with pure lithium foil, at 0.5C cycling, the capacity drops significantly after 18 cycles, and sharply decreases to 62.94 mAh·g−1 after 21 cycles -1 . It can be seen that the LiTiO2 / carbon fiber||LFP full battery assembled with the 50-μm composite metal lithium anode has no obvious downward trend in discharge specific capacity, stable long-cycle performance, and is applicable to high-power density batteries

[0072] Example 3

[0073] (1) Carbon fiber pretreatment: The carbon fiber was put into a mixed solution of 100 mL of concentrated sulfuric acid and concentrated nitric acid (V:V = 1:1) for heat treatment (soaked at 100 °C) for 1 h. After heat treatment, the carbon fiber was cooled to room temperature, washed with deionized water, and dried at 120 °C for 16 h

[0074] (2) The carbon fiber and titanium dioxide obtained in step (1) were subjected to high-temperature water removal treatment (120 °C, 12 h) in a vacuum atmosphere to obtain dry carbon fiber and dry titanium dioxide

[0075] (3) The dry titanium dioxide, dry carbon fiber, and lithium metal were mixed together in a mass ratio of 0.4:1:1 by the roll pressing method

[0076] (4) The mixture in step (3) was mixed and stirred at a molten state of 370 °C for 20 min to obtain a uniformly mixed composite metal lithium material

[0077] (5) The composite metal lithium material in step (4) was hot-pressed to obtain a composite metal lithium anode with a thickness of 200 μm

[0078] Application Example 3

[0079] The composite metal lithium anode prepared in Example 3 was cut into circular pieces with a diameter of 16 mm. Using it as the negative electrode, a ternary NCM811 (lithium nickel cobalt manganese oxide) material as the positive electrode, with a loading of 5 mg·cm−2 -2 , a traditional commercial liquid electrolyte (battery grade, Guangzhou Tianci High-Tech Materials Co., Ltd.) and a commercial PE separator (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were assembled into a button full battery. The above battery assembly was carried out in a glove box with the water and oxygen content both lower than 0.1 ppm

[0080] The charge-discharge performance of the full battery is as Figure 6 shown. Compared with the Li||NCM811 full battery constructed with a pure lithium foil, the assembled LiTiO2 / carbon fiber||NCM811 full battery has an initial capacity of 168.37 mAh·g -1 at 1C during the initial cycle, and the capacity is 164.54 mAh·g -1 after 150 cycles, with a capacity retention rate of 97.72%; while for the Li||NCM811 full battery constructed with a pure lithium foil, the capacity retention rate gradually decreases after 70 cycles at 1C, and drops to 80% after 100 cycles. The above results indicate that the obtained LiTiO2 / carbon fiber||NCM811 full battery has better cycling stability at 1C, and there is no obvious downward trend in the discharge specific capacity. The long-cycle stability performance of the assembled LiTiO2 / carbon fiber||NCM811 full battery is effective in actual battery applications.

[0081] Application Example 4

[0082] The composite metal lithium anode prepared in Example 1 (dry titanium dioxide, dry carbon fiber, and metal lithium with a mass ratio of 0.5:0.3:1 and a thickness of 200 μm) was cut into circular pieces with a diameter of 16 mm. Using this as the anode, lithium iron phosphate material as the cathode, and the loading amount was 5 mg·cm -2 , a button full battery was assembled with a traditional commercial liquid electrolyte (battery grade, Guangzhou Tianci High-Tech Materials Co., Ltd.) and a commercial PE separator (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.). The assembly of the above batteries was all carried out in a glove box with the water and oxygen content both lower than 0.1 ppm.

[0083] The rate performance of the full battery is as Figure 7 shown. For the assembled LiTiO2 / carbon fiber||LFP full battery at the rates of 0.2C, 0.5C, 1C, 2C, and 5C, the full battery discharge specific capacities are 158.78, 156.19, 149.67, 140.94, and 123.15 mAh·g -1 , and it recovers to 149.34 mAh·g -1 at 1C. The above results indicate that the assembled LiTiO2 / carbon fiber||LFP full battery can adapt to charge and discharge under different currents and has excellent rate performance.

[0084] By preparing an ultra-thin composite metal lithium anode with a mass ratio of titanium dioxide, carbon fiber, and metal lithium of 0.5:0.3:1, the assembled LiTiO2 / carbon fiber||LFP full battery has excellent rate performance and long-cycle stability. Titanium dioxide reacts with metal lithium in situ to form LiTiO2, and LiTiO2 has a special crystal structure, consisting of Li + and Ti 3+formed by alternating arrangement, and this structure allows Li + to move rapidly, which can provide good ionic and electronic conductivity for the composite lithium metal anode. Lithium titanate and carbon materials, as lithiumophilic support structures, can synergistically improve the interfacial stability and structural stability of the composite lithium metal anode during cycling. It not only retains the advantages of high capacity of lithium metal but also improves the problems of infinite volume change and uncontrollable growth of lithium dendrites in the lithium metal anode, making the composite lithium metal anode have excellent long-cycle stability.

[0085] Examples 4 - 5

[0086] (1) Carbon fiber pretreatment: Put carbon fiber into a mixed solution of 100 mL of concentrated sulfuric acid and concentrated nitric acid (V:V = 1:1) for heat treatment (soaking at 100 °C) for 1 h. After heat treatment, cool the carbon fiber to room temperature, wash it with deionized water, and dry it at 120 °C for 16 h;

[0087] (2) Subject the carbon fiber and titanium dioxide obtained in step (1) to high-temperature drying treatment (120 °C, 12 h) under a vacuum atmosphere to obtain dry carbon fiber and dry titanium dioxide;

[0088] (3) Use the roll pressing method to mix dry titanium dioxide, dry carbon fiber, and metallic lithium in mass ratios of 1:1:1, 0.5:0.3:1 (Example 1), 0.4:1:1 (Example 3), and 0.1:0.1:1 respectively to prepare four composite lithium metal anodes;

[0089] (4) Mix and stir the mixture in step (3) at a molten state of 370 °C for 20 min to obtain a uniformly mixed composite lithium metal material;

[0090] (5) Hot press the composite lithium metal material in step (4) to obtain a composite lithium metal anode with a thickness of 200 μm.

[0091] Cut the prepared composite lithium metal anode into circular pieces with a diameter of 16 mm. Use it as the anode, LFP material as the cathode, and the LFP loading is 5 mg·cm -2 , and assemble it into a button full cell with a traditional commercial liquid electrolyte (battery grade, Guangzhou Tianci High-Tech Materials Co., Ltd.) and a commercial PE separator (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.). The assembly of the above batteries is carried out in a glove box with the water and oxygen content both lower than 0.1 ppm.

[0092] The assembled button full cells are denoted as Li-1 (mass ratio of titanium dioxide, carbon fiber, and lithium metal is 1:1:1), Li-2 (mass ratio of titanium dioxide, carbon fiber, and lithium metal is 0.5:0.3:1), Li-3 (mass ratio of titanium dioxide, carbon fiber, and lithium metal is 0.4:1:1), and Li-4 (mass ratio of titanium dioxide, carbon fiber, and lithium metal is 0.1:0.1:1). The rate performance of full cells with different mass ratios is as Figure 8 shown. The assembled LiTiO2 / carbon fiber||LFP full cells are tested at rates of 0.2C, 0.5C, 1C, 2C, 5C, and 1C. The discharge specific capacities of the Li-2 full cell are 158.78, 156.19, 149.67, 140.94, and 123.15 mAh·g -1 respectively, and it recovers to 149.34 mAh·g at 1C -1 . At each rate, it is superior to the Li-1, Li-3, and Li-4 full cells. More lithium titanate and carbon fiber will cause particle agglomeration on the surface of the composite lithium metal anode, which is not conducive to the deposition and stripping of lithium metal; less lithium titanate and carbon fiber are not enough to form a framework structure. The LiTiO2 / carbon fiber||LFP full cell assembled with Li-2 shows excellent rate performance and cycle stability, and has broad application potential.

[0093] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments according to the embodiments of the present invention without creative work, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A composite lithium metal material, characterized in that, It includes metallic lithium, as well as lithium titanate and carbon material dispersed in the metallic lithium.

2. The composite lithium metal material according to claim 1, characterized in that, The mass ratio of the metallic lithium to the lithium titanate is 1:(0.1 - 10).

3. The composite lithium metal material according to claim 1, characterized in that, The carbon material includes one or more of graphene, carbon fiber, carbon microsphere, graphite, soft carbon, hard carbon, and carbon nanotube.

4. The composite lithium metal material according to claim 1 or 3, characterized in that, The mass ratio of the metallic lithium to the carbon material is 1:(0.1 - 10).

5. The preparation method of the composite lithium metal material according to any one of claims 1 to 4, characterized in that, It includes the following steps: Mix the carbon material, titanium dioxide, and metallic lithium, and perform in-situ lithiation reaction by melting to obtain the composite metallic lithium material.

6. The preparation method according to claim 5, wherein The mass ratio of the titanium dioxide, carbon material, and metallic lithium is (0.1 - 10):(0.1 - 10):

1.

7. The preparation method according to claim 5, characterized in that, The mixing of the carbon material, titanium dioxide, and metallic lithium is as follows: By using the roll pressing method, press the carbon material and titanium dioxide into the metallic lithium.

8. The preparation method according to claim 5, wherein The temperature of the in-situ lithiation reaction is 350 - 370 °C, and the time is 10 - 20 min.

9. Application of the composite metallic lithium material according to any one of claims 1 - 4 or the composite metallic lithium material obtained by the preparation method according to any one of claims 5 - 8 in the negative electrode of a lithium battery.

10. A composite lithium metal anode, characterized in that, The material of the composite metallic lithium negative electrode is the composite metallic lithium material according to any one of claims 1 - 4 or the composite metallic lithium material obtained by the preparation method according to any one of claims 5 - 8; The composite metallic lithium negative electrode is in a flake shape, and the thickness of the composite metallic lithium negative electrode is 30 - 600 μm.

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