A composite lithium metal material, its preparation method and application, and a composite lithium metal anode.

Abstract

This invention belongs to the field of lithium battery technology, specifically relating to a composite lithium metal material, its preparation method and application, and a composite lithium metal anode. The composite lithium metal material of this invention includes lithium metal, and lithium titanate and carbon materials dispersed in the lithium metal. A composite lithium metal anode is obtained by hot pressing the composite lithium metal material of this invention. The lithium titanate and carbon materials, acting as a lithiophilic support structure, synergistically improve the interfacial and structural stability of the composite lithium metal anode during cycling. This maintains the high capacity advantage of lithium metal while improving the problems of infinite volume change and uncontrollable lithium dendrite growth in lithium metal anodes, resulting in excellent cycle stability for the composite lithium metal anode. The preparation method of the composite lithium metal anode of this invention has the advantages of ease of operation and good repeatability.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a composite lithium metal material, its preparation method and application, and a composite lithium metal anode. Background Technology

[0002] Lithium-ion batteries possess high specific energy and a high voltage plateau, and are environmentally friendly with long cycle times, making them widely used in many fields such as portable medical devices and electric vehicles. Currently, most common lithium-ion batteries use graphite and its composite materials as the negative electrode, which exhibits relatively excellent electrochemical and cycle performance. However, commercially available graphite negative electrodes have a low specific capacity, 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 range 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 (relative to -3.04V for the standard hydrogen electrode), are considered ideal anode materials for next-generation high-energy-density lithium-ion batteries. However, the "no host" nature and high reactivity of lithium metal cause it to face problems such as unlimited volume change and uncontrollable lithium dendrite growth during charge and discharge, resulting in rapid capacity decay and poor cycle stability in lithium-ion batteries. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a composite lithium metal material, its preparation method and application, and a composite lithium metal anode. The composite lithium metal anode prepared using the composite lithium metal material of this invention results in a full cell exhibiting excellent cycle stability.

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

[0006] Preferably, the mass ratio of lithium metal 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 lithium metal to the carbon material is 1:(0.1 to 10).

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

[0010] Carbon materials, titanium dioxide, and lithium metal are mixed and melted to carry out an in-situ lithiation reaction to obtain the composite lithium metal material.

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

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

[0013] Preferably, the in-situ lithiation reaction is carried out at a temperature of 350–370°C for 10–20 minutes.

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

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

[0016] The composite lithium metal anode is in the form of a thin sheet, and the thickness of the composite lithium metal anode is 30-600 μm.

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

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

[0019] This invention employs lithium titanate and carbon materials as a lithiophilic support structure. Lithium titanate (LiTiO2) has a special crystal structure composed of Li + and Ti 3+ Alternating arrangement forms, this structure allows Li + Rapid movement provides excellent ionic and electronic conductivity for the composite lithium metal anode. Uniformly distributed lithium-ion titanate effectively regulates lithium ions, ensuring their uniform distribution on the electrode and achieving uniform lithium deposition while suppressing lithium dendrite formation. The addition of carbon materials improves the conductivity of lithium titanate, thus enabling the composite lithium metal anode to maintain cycle stability under high current. The synergistic effect of lithium titanate and carbon materials enhances the interfacial and structural stability of the composite lithium metal anode during cycling, maintaining the high capacity of lithium metal while mitigating the problems of unlimited volume change and uncontrollable lithium dendrite growth in lithium metal anodes. The assembled full cell exhibits excellent cycle stability.

[0020] The present invention also provides a composite lithium metal anode, which has an easy-to-operate preparation process and good repeatability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0023] Figure 2 The image shows the physical product of the composite lithium metal anode (titanium dioxide, carbon fiber, lithium metal in a mass ratio of 0.5:0.3:1) prepared in Example 1.

[0024] Figure 3 The diagram shows the composition and distribution of the composite lithium metal anode (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1) prepared in Example 1.

[0025] Figure 4 The graph shows a comparison of charge-discharge cycles at 1C between the composite lithium metal anode (titanium dioxide, carbon fiber or carbon microspheres, lithium metal mass ratio of 0.5:0.3:1, thickness 200 μm) prepared in Example 1, the unmodified lithium metal anode, and the full battery assembled with lithium iron phosphate.

[0026] Figure 5 The graph shows a comparison of charge-discharge cycles at 0.5C between the composite lithium metal anode (titanium dioxide, carbon fiber, lithium metal mass ratio 0.5:0.3:1, thickness 50 μm) prepared in Example 2, the unmodified lithium metal anode, and the full battery assembled with lithium iron phosphate.

[0027] Figure 6 The images show a comparison of the charge-discharge cycles at 1C of the composite lithium metal anode (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.4:1:1, with a thickness of 200 μm) and the unmodified lithium metal anode prepared in Example 3, and the full cell assembled with ternary NCM811.

[0028] Figure 7 The graph shows a comparison of charge-discharge cycles at different rates of the full battery assembled with the composite lithium metal anode prepared in Example 1 and lithium iron phosphate.

[0029] Figure 8The graph shows a comparison of charge-discharge cycles of lithium iron phosphate full cells assembled with composite lithium metal anodes of different mass ratios at different rates. In the graph, Li-1 refers to a mass ratio of titanium dioxide, carbon fiber, and lithium metal of 1:1:1; Li-2 refers to a mass ratio of titanium dioxide, carbon fiber, and lithium metal of 0.5:0.3:1; Li-3 refers to a mass ratio of titanium dioxide, carbon fiber, and lithium metal of 0.4:1:1; and Li-4 refers to a mass ratio of titanium dioxide, carbon fiber, and lithium metal of 0.1:0.1:1. Detailed Implementation

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

[0031] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

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

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

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

[0035] The composite lithium metal anode was prepared using the composite lithium metal material of the present invention. Lithium titanate (LiTiO2) has a special crystal structure, which is composed of Li + and Ti 3+ Alternating arrangement forms, this structure allows Li + Rapid movement provides excellent ionic and electronic conductivity for the composite lithium metal anode. Lithium titanate and carbon materials, as lithiophilic support structures, can synergistically improve the interfacial and structural stability of the composite lithium metal anode during cycling. This maintains the high capacity advantage of lithium metal while improving the problems of infinite volume change and uncontrollable lithium dendrite growth in lithium metal anodes. The assembled full cell exhibits excellent cycle stability.

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

[0037] Carbon materials, titanium dioxide, and lithium metal are mixed and melted to carry out an in-situ lithiation reaction to obtain the composite lithium metal material.

[0038] In this invention, the carbon material is preferably a heat-treated carbon material. The heat treatment preferably includes immersing the carbon material in a strong oxidizing solvent, followed by washing and drying. The strong oxidizing solvent is preferably a mixture of concentrated nitric acid and concentrated hydrochloric acid, with a volume ratio of (1-10):(1-10), more preferably 1:1. The immersion temperature is preferably 100-120°C, and the immersion time is preferably 1 hour. The washing is preferably water washing until neutral; the drying temperature is preferably 120°C, and the drying time is preferably 16 hours. The heat treatment removes impurities from the surface of the carbon material and simultaneously makes it easier for the carbon material to adsorb onto metallic lithium.

[0039] In this invention, before mixing the carbon material, titanium dioxide, and lithium metal, the process further includes: dehydrating the carbon material and titanium dioxide; the dehydration treatment is preferably carried out under a vacuum atmosphere, the temperature of the dehydration treatment is preferably 100-120°C, and the time is preferably 12-24 hours.

[0040] In this invention, the preferred mass ratio of titanium dioxide, carbon material, and lithium metal is (0.1–10):(0.1–10):1, more preferably (1–10):(1–10):1, and specifically can be 1:1:1, 0.5:0.3:1, 0.4:1:1, or 0.1:0.1:1. This mass ratio ensures that there is no excessive amount of lithium titanate and carbon material, which would lead to particle agglomeration on the surface of the composite lithium metal anode, hindering lithium metal deposition and stripping; nor is there insufficient amount of lithium titanate and carbon material to form a sufficient framework structure.

[0041] In this invention, the mixing of carbon material, titanium dioxide, and lithium metal is preferably carried out by pressing the carbon material and titanium dioxide into the lithium metal using a rolling process. Both the carbon material and titanium dioxide are preferably in powder form, and their particle sizes are independently preferably 5–15 nm. The rolling process is preferably carried out in a glove box filled with argon gas. Lithification begins after the titanium dioxide and lithium metal come into contact during the pressing process.

[0042] In this invention, the preferred temperature for the in-situ lithiation reaction is 350–370°C, and the preferred stirring time is 10–20 min, more preferably 15–20 min. The in-situ lithiation reaction is preferably carried out under molten heating conditions, and this invention does not have specific requirements for the stirring rate. During the stirring process, titanium dioxide and lithium react fully to form lithium titanate, and all components are mixed uniformly. The in-situ lithiation reaction is preferably carried out in a glove box filled with argon gas.

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

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

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

[0046] The composite lithium metal anode is in the form of a thin sheet, and the thickness of the composite lithium metal anode is 30-600 μm.

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

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

[0049] In this invention, the preferred hot-pressing temperature is 80–100°C, and the preferred time is 5 minutes. The hot-pressing method used in this invention facilitates the stretching of composite lithium metal materials into composite lithium metal electrode sheets with controllable thickness.

[0050] This invention prepares a composite lithium metal anode by melting and hot pressing titanium dioxide, carbon materials, and lithium metal. The raw materials after melting and mixing are hot-pressed to obtain a composite lithium metal anode with controllable thickness. In this invention, lithium titanate, which is lithium-philic, and carbon materials with excellent conductivity work together to improve the problems of lithium dendrites and volume changes in the lithium metal anode, thus obtaining a composite lithium metal anode with excellent rate performance and cycle stability.

[0051] To further illustrate the present invention, the composite lithium metal material, its preparation method and application, and the composite lithium metal anode provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] (1) Pretreatment of carbon fiber (or carbon microspheres): Heat treatment (immersion at 100℃) in 100mL of a mixture of concentrated sulfuric acid and concentrated nitric acid (V:V = 1:1) for 1h. After heat treatment, cool the carbon fiber (or carbon microspheres) to room temperature, wash with deionized water and dry at 120℃ for 16h.

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

[0055] (3) Dry titanium dioxide, dry carbon fiber (or carbon microspheres), and lithium metal are mixed together by roller pressing in a mass ratio of 0.5:0.3:1.

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

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

[0058] Figure 1 The image shows a SEM image of the composite lithium metal anode (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1) prepared in Example 1. Figure 2 This is a photograph of the composite lithium metal anode (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1) prepared in Example 1. Microscopically, the surface of the composite lithium metal anode material is relatively rough due to the protrusion of the LiTiO2 particles, exhibiting a close contact between LiTiO2 and Li metal without any cracks. Macroscopically, the surface is smooth and dense, without any cracks, consistent with the physical properties of lithium metal electrode sheets.

[0059] Figure 3 The diagram shows the composition and distribution of the composite lithium metal anode (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 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 anode.

[0060] Application Example 1

[0061] The composite lithium metal anode prepared in Example 1 was cut into a circular piece with a diameter of 16 mm. This circular piece was used as the anode, and LFP (lithium iron phosphate) material was used as the cathode, with a lithium iron phosphate loading of 5 mg·cm³. -2 Traditional commercial liquid electrolytes (battery grade, Guangzhou Tinci Advanced Materials Co., Ltd.) and commercial PE separators (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were used to assemble button cells. All battery assembly was carried out in a glove box with water and oxygen content below 0.1 ppm.

[0062] The charge and discharge performance of the full battery is as follows Figure 4As shown, compared with the Li||LFP full cell constructed from pure lithium sheets, the assembled LiTiO2 / carbon fiber||LFP full cell has an initial capacity of 149.09 mAh·g under 1C cycling. -1 After 350 cycles, the capacity was 131.45 mAh·g. -1 The capacity retention rate was 88.16%; the assembled LiTiO2 / carbon microsphere || LFP full cell retained a capacity of 104 mAh·g after 300 cycles at 1C. -1 The capacity retention rate was 71.72%; the Li||LFP full cell constructed from pure lithium sheets exhibited a capacity decay of 78.68 mAh·g after 200 cycles at 1C. -1 The capacity retention rate was 55.11%. It can be seen that the discharge specific capacity of the assembled LiTiO2 / carbon fiber||LFP full cell did not show a significant downward trend, and its long-term cycling performance was more stable.

[0063] Example 2

[0064] (1) Carbon fiber pretreatment: Heat treatment (immersion at 100℃) in 100mL of a mixture of concentrated sulfuric acid and concentrated nitric acid (V:V=1:1) for 1h. After heat treatment, cool the carbon fiber to room temperature, wash it with deionized water and dry it at 120℃ for 16h.

[0065] (2) The carbon fibers and titanium dioxide obtained in step (1) are dried at high temperature (120°C, 12h) in a vacuum atmosphere to obtain dried carbon fibers and dried titanium dioxide.

[0066] (3) Dry titanium dioxide, dry carbon fiber, and metallic lithium are mixed together by roller pressing in a mass ratio of 0.5:0.3:1;

[0067] (4) The mixture from step (3) is mixed and stirred at 370°C in a molten state for 20 minutes to obtain a uniformly mixed composite lithium metal material;

[0068] (5) The composite lithium metal material from step (4) is hot-pressed to obtain a composite lithium metal anode with a thickness of 50 μm.

[0069] Application Example 2

[0070] The composite lithium metal anode prepared in Example 2 was cut into a circular piece with a diameter of 16 mm. This circular piece was used as the anode, and LFP material was used as the cathode. The LFP loading was 8 mg·cm³. -2 Traditional commercial liquid electrolytes (battery grade, Guangzhou Tinci Advanced Materials Co., Ltd.) and commercial PE separators (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were used to assemble button cells. All battery assembly was carried out in a glove box with water and oxygen content below 0.1 ppm.

[0071] The charge and discharge performance of the full battery is as follows Figure 5 As shown, compared to the Li||LFP full cell constructed from pure lithium sheets, the assembled LiTiO2 / carbon fiber||LFP full cell has an initial capacity of 162.08 mAh·g under 0.5C cycling. -1 After 80 cycles, the capacity was 154.51 mAh·g. -1 The capacity retention rate was 95.32%; however, the Li||LFP full cell constructed from pure lithium sheets showed a significant capacity decrease after 18 cycles at 0.5C, and a sharp reduction to 62.94 mAh·g after 21 cycles. -1 It can be seen that the discharge specific capacity of the LiTiO2 / carbon fiber||LFP full cell assembled with a 50μm composite lithium metal anode does not show a significant decreasing trend, and its long-cycle performance is stable, making it suitable for high power density batteries.

[0072] Example 3

[0073] (1) Carbon fiber pretreatment: Heat treatment (immersion at 100℃) in 100mL of a mixture of concentrated sulfuric acid and concentrated nitric acid (V:V=1:1) for 1h. After heat treatment, cool the carbon fiber to room temperature, wash it with deionized water and dry it at 120℃ for 16h.

[0074] (2) The carbon fibers and titanium dioxide obtained in step (1) are subjected to high-temperature dehydration treatment (120°C, 12h) in a vacuum atmosphere to obtain dried carbon fibers and dried titanium dioxide.

[0075] (3) Dry titanium dioxide, dry carbon fiber and lithium metal are mixed together by roller pressing at a mass ratio of 0.4:1:1;

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

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

[0078] Application Example 3

[0079] The composite lithium metal anode prepared in Example 3 was cut into a circular piece with a diameter of 16 mm. This circular piece was used as the anode, and the ternary NCM811 (lithium nickel cobalt manganese oxide) material was used as the cathode, with a loading of 5 mg·cm³. -2 Traditional commercial liquid electrolytes (battery grade, Guangzhou Tinci Advanced Materials Co., Ltd.) and commercial PE separators (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were used to assemble button cells. All battery assembly was carried out in a glove box with water and oxygen content below 0.1 ppm.

[0080] The charge and discharge performance of the full battery is as follows Figure 6 As shown, compared to the Li||NCM811 full cell constructed from pure lithium sheets, the assembled LiTiO2 / carbon fiber||NCM811 full cell has an initial cycling capacity of 168.37 mAh·g at 1C. -1 After 150 cycles, the capacity is 164.54 mAh·g. -1 The capacity retention rate was 97.72%; while the Li||NCM811 full cell constructed from pure lithium sheets showed a gradual decrease in capacity retention rate after 70 cycles at 1C, dropping to 80% after 100 cycles. These results indicate that the obtained LiTiO2 / carbon fiber||NCM811 full cell exhibits more stable cycling performance at 1C, with no significant decrease in discharge specific capacity. The assembled LiTiO2 / carbon fiber||NCM811 full cell demonstrates effective long-term cycling stability in practical battery applications.

[0081] Application Example 4

[0082] The composite lithium metal anode (dried titanium dioxide, dried carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1, with a thickness of 200 μm) prepared in Example 1 was cut into discs with a diameter of 16 mm. These discs were used as the anode, and lithium iron phosphate was used as the cathode with a loading of 5 mg·cm³. -2 Traditional commercial liquid electrolytes (battery grade, Guangzhou Tinci Advanced Materials Co., Ltd.) and commercial PE separators (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were used to assemble button cells. All battery assembly was carried out in a glove box with water and oxygen content below 0.1 ppm.

[0083] The rate performance of the full battery, such as Figure 7 As shown, the assembled LiTiO2 / carbon fiber ||LFP full cells exhibit discharge specific capacities of 158.78, 156.19, 149.67, 140.94, and 123.15 mAh·g at discharge rates of 0.2C, 0.5C, 1C, 2C, and 5C, respectively. -1 And it recovers to 149.34 mAh·g at 1C. -1 The above results demonstrate that the assembled LiTiO2 / carbon fiber ||LFP full cell can adapt to charge and discharge at different currents and possesses excellent rate performance.

[0084] An ultrathin composite lithium metal anode was prepared using titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1. The assembled LiTiO2 / carbon fiber || LFP full cell exhibited excellent rate performance and long-term cycle stability. Titanium dioxide reacts with lithium metal in situ to form LiTiO2, which possesses a unique crystal structure. + and Ti 3+Alternating arrangement forms, this structure allows Li + Rapid movement provides excellent ionic and electronic conductivity for the composite lithium metal anode. Lithium titanate and carbon materials, as lithiophilic support structures, synergistically enhance the interfacial and structural stability of the composite lithium metal anode during cycling. This maintains the high capacity advantage of lithium metal while mitigating the problems of infinite volume change and uncontrollable lithium dendrite growth in lithium metal anodes, resulting in excellent long-term cycling stability for the composite lithium metal anode.

[0085] Examples 4-5

[0086] (1) Carbon fiber pretreatment: Heat treatment (immersion at 100℃) in 100mL of a mixture of concentrated sulfuric acid and concentrated nitric acid (V:V=1:1) for 1h. After heat treatment, cool the carbon fiber to room temperature, wash it with deionized water and dry it at 120℃ for 16h.

[0087] (2) The carbon fibers and titanium dioxide obtained in step (1) are dried at high temperature (120°C, 12h) in a vacuum atmosphere to obtain dried carbon fibers and dried titanium dioxide.

[0088] (3) Four composite lithium metal anodes were prepared by mixing 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 using the rolling method.

[0089] (4) The mixture from step (3) is mixed and stirred at 370°C in a molten state for 20 minutes to obtain a uniformly mixed composite lithium metal material;

[0090] (5) The composite lithium metal material from step (4) is hot-pressed to obtain a composite lithium metal anode with a thickness of 200 μm.

[0091] The prepared composite lithium metal anode was cut into circular pieces with a diameter of 16 mm. These were used as the anode, and LFP material was used as the cathode. The LFP loading was 5 mg·cm³. -2 Traditional commercial liquid electrolytes (battery grade, Guangzhou Tinci Advanced Materials Co., Ltd.) and commercial PE separators (12HP, Liaoyuan Hongtu Lithium Battery Separator Technology Co., Ltd.) were used to assemble button cells. All battery assembly was carried out in a glove box with water and oxygen content below 0.1 ppm.

[0092] The assembled button cells were designated as Li-1 (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 1:1:1), Li-2 (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.5:0.3:1), Li-3 (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.4:1:1), and Li-4 (titanium dioxide, carbon fiber, and lithium metal in a mass ratio of 0.1:0.1:1). The rate performance of the cells with different mass ratios is as follows: Figure 8 As shown, the assembled LiTiO2 / carbon fiber ||LFP full cells were tested at rates of 0.2C, 0.5C, 1C, 2C, 5C, and 1C. The specific discharge capacities of the Li-2 full cells were 158.78, 156.19, 149.67, 140.94, and 123.15 mAh·g, respectively. -1 And it recovers to 149.34 mAh·g at 1C. -1 The LiTiO2 / carbon fiber || LFP full cell exhibits superior performance across all rate capabilities compared to Li-1, Li-3, and Li-4 full cells. However, excessive lithium titanate and carbon fiber can lead to particle agglomeration on the surface of the composite lithium metal anode, hindering lithium metal deposition and stripping; insufficient lithium titanate and carbon fiber are insufficient to form a structural framework. The Li-2 assembled LiTiO2 / carbon fiber || LFP full cell demonstrates excellent rate performance and cycle stability, showing broad application potential.

[0093] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A composite lithium metal anode, characterized by, The material of the composite metal lithium negative electrode is a composite metal lithium material; The composite metal lithium negative electrode is in a sheet shape, and the thickness of the composite metal lithium negative electrode is 30-600 microns; The preparation method of the composite metal lithium material comprises the following steps: The carbon material, titanium dioxide and metal lithium are mixed and subjected to in-situ lithiation reaction in a molten state to obtain the composite metal lithium material; The composite metal lithium material comprises metal lithium, lithium titanate and carbon material dispersed in the metal lithium; The mass ratio of the titanium dioxide, carbon material and metal lithium is (0.1-1):(0.1-1):1; The carbon material, titanium dioxide and metal lithium are mixed by using a rolling method to press the carbon material and titanium dioxide into the metal lithium; The temperature of the in-situ lithiation reaction is 350-370 DEG C, and the time is 10-20 min; the in-situ lithiation reaction is stirring in a heated molten state.

2. The composite lithium metal anode of claim 1, wherein, The carbon material comprises one or more of graphene, carbon fiber, carbon microsphere, graphite, soft carbon, hard carbon and carbon nanotube.

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