Lithium metal battery cell, composite negative electrode material, battery device, and electric device

Abstract

The application relates to the technical field of batteries, and discloses a lithium metal battery monomer, a composite negative electrode material, a battery device and a power utilization device. The lithium metal battery monomer comprises a negative electrode sheet, the negative electrode sheet comprises a composite negative electrode material, and the composite negative electrode material comprises a graphene composite material; the graphene composite material comprises graphene and metal oxide particles loaded on the surface of the graphene, and the metal oxide comprises at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO and Al2O3. The composite negative electrode material has reduced nucleation overpotential and high lithium affinity, can reduce the formation of lithium dendrites, and can significantly improve the high-rate long-cycle capacity retention rate and average coulomb efficiency of the lithium metal battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a lithium metal battery cell, a composite negative electrode material, a battery device, and an electrical device. Background Technology

[0002] With the increasing demand for long driving range in electric vehicles and consumer electronics, the development of high-energy-density batteries has become an important research direction in the field of battery technology. The U.S. Department of Energy has proposed a 500Wh / kg... -1 The goals further clarify the development direction of next-generation high-energy-density batteries. Against this backdrop, lithium metal, due to its high theoretical specific capacity (3860 mAh / g) and low standard electrode potential, is considered a key material for improving battery energy density and increasing battery storage capacity. As an anode material, lithium metal can significantly improve battery energy density, which is of great significance for promoting the development of electric vehicles and high-performance electronic products.

[0003] Despite the advantages mentioned above, in practical applications, the deposition and extraction of lithium during charging and discharging are uncontrollable, and lithium dendrites are easily formed on the surface of the anode. Summary of the Invention

[0004] In view of the above problems, this application provides a lithium metal battery cell, a composite anode material, a battery device, and an electrical device, aiming to solve the problems of lithium dendrite formation in lithium metal battery anodes and rapid capacity decay during cycles.

[0005] In a first aspect, embodiments of this application provide a lithium metal battery cell, including a negative electrode sheet, the negative electrode sheet including a composite negative electrode material, the composite negative electrode material including a graphene composite material; the graphene composite material including graphene and metal oxide particles loaded on the surface of the graphene, the metal oxide including at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

[0006] The composite anode material of this application embodiment has a reduced nucleation overpotential and high lithiophilicity, which can reduce the formation of lithium dendrites. First, its high lithiophilicity stems from lithiophilic metal oxides. Due to the strong electronegativity of oxygen, these metal oxides can form Li-O bonds with lithium. This dipole interaction can guide the uniform deposition of lithium, thereby reducing the overpotential for lithium nucleation. A lower nucleation overpotential means that lithium ions are more easily uniformly reduced on the anode surface to form metallic lithium, reducing the formation of lithium dendrites. Some metals in the metal oxides, such as Zn and Al, can form alloys with Li. This alloying effect lowers the heterogeneous nucleation barrier, further enhancing lithiophilicity and facilitating uniform lithium deposition. Second, the graphene composite material, by combining lithiophilic metal oxide particles with graphene, not only enhances the lithiophilicity of the graphene composite material but also inhibits the stacking of graphene and the agglomeration of metal oxides, thereby increasing the specific surface area and electroactive surface area of ​​graphene and improving its electrochemical performance.

[0007] This application's embodiments, by constructing a graphene-lithophile metal oxide framework, can significantly reduce the concentration gradient of lithium metal during deposition due to lithium-ion diffusion and lower the local current density. This reduction helps extend the sand time, i.e., the time for lithium dendrite formation, thereby extending cycle life. Lithium dendrites are a common problem in lithium-ion batteries, potentially leading to short circuits and thermal runaway, thus reducing battery cycle life and safety. By extending the sand time, the composite lithium metal anode material can suppress dendrite growth, thereby extending battery cycle life.

[0008] Graphene composite materials can be used as anode materials in "anode-free" lithium metal batteries. A "anode-free" lithium metal battery refers to a battery in which the anode does not contain pre-deposited active lithium metal during the manufacturing process. In this type of battery, during the first charge, lithium ions migrate from the positive electrode to the negative electrode and deposit a lithium metal layer on the surface of the negative electrode. The graphene composite material used in this type of battery primarily serves as a host material, providing a structural framework to support the subsequently deposited lithium metal, while also utilizing the inherent properties of graphene composite materials to optimize battery performance.

[0009] In some embodiments, the number density deviation of the metal oxide particles over at least 90% of the area of ​​the graphene does not exceed ±15%; and / or, the average distance between any two adjacent metal oxide particles does not exceed 20 nm.

[0010] This indicates that the metal oxide particles on the graphene surface are highly dispersed. These particles are uniformly dispersed on the graphene surface. This uniformity helps guide the uniform nucleation and deposition of lithium metal, promoting a flat and dense lithium deposition morphology in the composite lithium metal anode material. This morphology helps reduce the growth of lithium dendrites in lithium metal batteries and improves the cycle performance of the battery.

[0011] In some embodiments, the composite negative electrode material satisfies at least one of the following conditions:

[0012] (1) The mass of the metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material;

[0013] (2) The specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g;

[0014] (3) The particle size of the graphene composite material is 5μm to 30μm;

[0015] (4) The particle size of the metal oxide particles is 5nm to 30nm.

[0016] Thus, by adjusting the performance parameters of composite lithium metal anode materials, the electrochemical performance, structural stability, and energy density of composite lithium metal anode materials can be further optimized, thereby further improving the cycle stability and safety of the battery.

[0017] In some embodiments, the metal oxide particles are TiO2 particles, which are mesoporous. Thus, on the one hand, the mesoporous structure of the TiO2 particles can further improve the wettability of the electrolyte, reduce the concentration gradient, and thereby further inhibit dendrite growth. On the other hand, mesoporousness helps to further increase the electrochemical active area of ​​the graphene composite material, improve the reaction kinetics of the battery, and thus enhance the high-rate cycling performance in lithium metal batteries.

[0018] In some embodiments, the pore size of the mesopores in the TiO2 particles is 3 nm to 5 nm. This results in uniform mesopores in the TiO2 particles, further suppressing dendrite growth.

[0019] In some embodiments, the composite anode material further includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

[0020] Lithium metal is combined with graphene composite materials to form the negative electrode of a lithium metal battery. The graphene composite material's reduced nucleation overpotential and high lithium affinity improve the stability of the lithium metal negative electrode, suppress lithium dendrite formation, and enhance the overall battery performance.

[0021] In some embodiments, the lithium metal accounts for 25% to 80% of the total mass of the composite anode material. This allows for a better balance between the safety, energy density, and cycle stability of lithium metal batteries.

[0022] Secondly, embodiments of this application provide a composite negative electrode material, including a graphene composite material, wherein the graphene composite material includes graphene and metal oxide particles loaded on the surface of the graphene, and the material of the metal oxide particles includes at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

[0023] In some embodiments, the number density deviation of the metal oxide particles over at least 90% of the area of ​​the graphene does not exceed ±15%; and / or, the average distance between any two adjacent metal oxide particles does not exceed 20 nm.

[0024] In some embodiments, the composite negative electrode material satisfies at least one of the following conditions:

[0025] (1) The mass of the metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material;

[0026] (2) The specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g;

[0027] (3) The particle size of the graphene composite material is 5μm to 30μm;

[0028] (4) The particle size of the metal oxide particles is 5nm to 30nm.

[0029] In some embodiments, the metal oxide particles are TiO2 particles, and the TiO2 particles have mesoporous structures.

[0030] In some embodiments, the pore size of the mesopores in the TiO2 particles is 3 nm to 5 nm.

[0031] In some embodiments, the composite anode material further includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

[0032] In some embodiments, the lithium metal accounts for 25% to 80% of the total mass of the composite anode material.

[0033] Thirdly, embodiments of this application provide a method for preparing a composite negative electrode material, comprising the following steps:

[0034] A metal salt, reducing sugar, graphene oxide, and a solvent are mixed to obtain a mixed solution; the metal salt includes at least one of titanium salt, zinc salt, copper salt, zirconium salt, nickel salt, cobalt salt, and aluminum salt; the mixed solution is subjected to a hydrothermal reaction to obtain a graphene composite material.

[0035] In this embodiment, the preparation process of the graphene composite material utilizes the anchoring effect of reducing sugars and a hydrothermal reaction to in-situ load lithiophilic metal oxide particles onto the surface of graphene sheets. The addition of reducing sugars facilitates the anchoring and uniform dispersion of lithiophilic metal oxides on the graphene surface. The lithiophilic metal oxide particles synthesized by this method are uniformly distributed on the graphene surface, exhibiting hyperdispersion, which is beneficial for further guiding the uniform nucleation and deposition of lithium metal. This hyperdispersion can be determined by transmission electron microscopy image analysis. Simultaneously, the aldehyde groups in the molecular structure of the reducing sugars also possess reducing properties, which can reduce graphene oxide to obtain three-dimensional porous reduced graphene oxide (rGO), thus improving electrochemical performance.

[0036] In some embodiments, the temperature of the hydrothermal reaction is 160°C to 200°C; and / or, the time of the hydrothermal reaction is 10h to 14h.

[0037] Thus, within the aforementioned temperature range, the reaction can be better controlled to proceed at a gentler pace, contributing to the acquisition of products with more uniform morphology. Controlling the hydrothermal reaction time within this range allows for the production of products with more ideal crystal size and morphology.

[0038] In some embodiments, the concentration of graphene oxide in the mixed solution is 1.5 mg / mL to 2.5 mg / mL; and / or, the mass ratio of graphene oxide to the metal salt is 1:(2.5 to 5); and / or, the mass ratio of the reducing sugar to the metal salt is 1:(10 to 20).

[0039] Thus, by optimizing the above preparation conditions, the hydrothermal reaction can be carried out more gently, while the prepared graphene composite material has better electrochemical performance and structural stability.

[0040] In some embodiments, the method for preparing the composite negative electrode material further includes the step of depositing lithium metal on the surface and / or in the pores of the graphene composite material.

[0041] This method involves depositing lithium metal onto a graphene composite material to form a composite lithium metal anode material. Lithium metal preferentially nucleates at sites on lithium-bearing metal oxide particles. This preferential nucleation guides uniform lithium metal deposition and reduces dendrite formation. By electrochemically depositing lithium metal onto the graphene composite material, the deposition process can be controlled, thereby improving the cycle stability and rate performance of lithium metal batteries.

[0042] In some embodiments, lithium metal is deposited on the surface and / or in the pores of the graphene composite material using electrochemical deposition or self-discharge.

[0043] High-performance composite anode materials can be prepared by combining lithium metal with graphene composites through electrochemical deposition or self-discharge.

[0044] In some embodiments, the graphene composite material is combined with lithium metal to form a coin cell, and the coin cell is subjected to electrochemical discharge deposition on a charge / discharge apparatus, wherein the current density of the electrochemical discharge deposition is 0.5 mA / cm². 2 ~5mA / cm 2 The deposition rate was 0.5 mAh / cm³. 2 ~14mAh / cm 2 After deposition, the coin cell is disassembled to obtain the composite negative electrode material; or, an electrolyte is dropped onto the graphene composite material, and lithium metal is bonded to the graphene composite material to form a primary cell. After 1 to 5 hours of self-discharge, the composite negative electrode material is obtained.

[0045] In this way, a more appropriate amount of lithium metal can be deposited, which not only improves the volumetric energy density but also optimizes long-term cycling stability.

[0046] Fourthly, embodiments of this application provide a battery device including the aforementioned lithium metal battery cell. Thus, due to the improved cycle stability of the lithium metal battery cell, the battery device exhibits superior performance.

[0047] Fifthly, embodiments of this application provide an electrical device including the aforementioned lithium metal battery cell or the aforementioned battery device, wherein the lithium metal battery cell or the battery device is used to store or provide electrical energy. Thus, the performance of the electrical device is improved.

[0048] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0049] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0050] Figure 1 This is a cross-sectional structural diagram of the electrode sheet in some embodiments of this application;

[0051] Figure 2 This is a schematic diagram of the structure of the electrode assembly in some embodiments of this application;

[0052] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0053] Figure 4 This is a schematic diagram illustrating the synthesis process of UMTGA and the deposition behavior of lithium metal in some embodiments of this application;

[0054] Figure 5 The following are images of UMTGA from some embodiments of this application: (a)-(b) are SEM images; (c)-(d) are TEM images; (e) is a HAADF-STEM image and the corresponding C, O, and Ti elemental distribution images;

[0055] Figure 6 The following are images of UMTGA in some embodiments of this application: (a)-(b) are HRTEM images of UMTGA; (c)-(d) are STEM images of UMTGA.

[0056] Figure 7 The following are spectra of UMTGA in some embodiments of this application: (a) XRD spectrum; (b) XPS spectrum; (c) Infrared spectrum; (d) Nitrogen adsorption-desorption isotherm of UMTGA; (e) DFT pore size distribution diagram; (f) Thermogravimetric curve.

[0057] Figure 8 The diagrams show the simulated binding energy between the electrode material and lithium atoms; (a) is the simulated binding energy between the Cu electrode and lithium atoms; (b) is the simulated binding energy between the GA electrode and lithium atoms; (c) is the simulated binding energy between the (101) crystal plane TiO2 UMTGA electrode and lithium atoms; and (d) is the simulated binding energy between the (001) crystal plane TiO2 UMTGA electrode and lithium atoms.

[0058] Figure 9 The diagrams show the simulated migration paths of lithium atoms on the electrode material surface. (a) shows the simulated migration path of Li atoms on the (101) crystal plane of a TiO2 UMTGA electrode; (b) shows the simulated migration path of Li atoms on the (001) crystal plane of a TiO2 UMTGA electrode; (c) shows the simulated migration path of Li atoms on the GA electrode surface; (d) shows the simulated migration path of Li atoms on the Cu electrode surface; and (e) shows the Li ion diffusion barrier diagram. In the diagrams, "Cu" represents the Cu electrode, "graphene" represents the GA electrode, "TiO2 / (101)-C" represents the (101) crystal plane of a TiO2 UMTGA electrode, and "TiO2 / (001)-C" represents the (001) crystal plane of a TiO2 UMTGA electrode.

[0059] Figure 10The figures show simulated lithium ion concentration gradient and growth morphology on the electrode material surfaces; (a) simulated lithium ion concentration gradient on the Cu electrode surface; (b) simulated lithium ion concentration gradient on the GA electrode surface; (c) simulated lithium ion concentration gradient on the UMTGA electrode surface; (d) simulated lithium growth morphology on the Cu electrode surface; (e) simulated lithium growth morphology on the GA electrode surface; and (f) simulated lithium growth morphology on the UMTGA electrode surface. In the figures, "Cu" represents the Cu electrode, "graphene" represents the GA electrode, and "TiO2@G" represents the UMTGA electrode.

[0060] Figure 11 Figure 1 shows the deposition / stripping morphology evolution of lithium metal on a UMTGA electrode; where (a) represents the deposition morphology at 1 mAh / cm³. 2 SEM image of the UMTGA electrode surface after deposition; (b) shows the deposition of 3 mAh / cm³. 2 SEM image of the UMTGA electrode surface after deposition; (c) shows the deposition of 5 mAh / cm³. 2 SEM image of the UMTGA electrode surface after removal; (d) shows the 2mAh / cm² electrode surface after removal. 2 SEM images of the UMTGA electrode surface after removal; (e)-(f) show the 5mAh / cm² stripping. 2 SEM image of the UMTGA electrode surface; (g) shows the corresponding positions of images (a)-(f) in the charge-discharge curve;

[0061] Figure 12 The graphs show the electrochemical performance of the half-cells, where (a) is the coulombic efficiency (CE) test graph of the Cu electrode of Comparative Example 1 and the UMTGA electrode of Example 1 at a gradient current density; (b) is the coulombic efficiency (CE) test graph of the Cu electrode of Comparative Example 1 and the UMTGA electrode of Example 1 at a current density of 2 mA / cm². 2 (c) shows the coulombic efficiency (CE) test results for the half-cell at different current densities, with each lithium metal deposition / stripping cycle lasting 1 hour.

[0062] Figure 13 SEM images of the lithium metal deposition morphology of the working electrode of the half-cell after cycling are shown; (a)-(c) are SEM images of the lithium metal deposition morphology of the UMTGA electrode after cycling at a current density of 2 mA / cm²; (d)-(f) are SEM images of the lithium metal deposition morphology of the Cu electrode after cycling at a current density of 2 mA / cm².

[0063] Figure 14 The graph shows the electrochemical performance of the half-cell; where (a) shows the performance of the Cu electrode, GA electrode, and UMTGA electrode at a current density of 1 mA / cm². 2 The capacity is 1 mA / cm 2(a) Coulomb efficiency test graph; (b) Comparison graph of overpotential during the first cycle; (c) Charge-discharge curves of UMTGA electrode at different cycles;

[0064] Figure 15 The figure shows the interface impedance fitting diagram of the half-cell after cycling; where (a) is the impedance at 1 mA / cm². 2 (a) Impedance plot after cycling at current density; (b) Fitted curve of lithium-ion diffusion coefficient;

[0065] Figure 16 The graphs show the electrochemical performance of the full cell; (a) shows the rate performance test and subsequent long-cycle test at 5C rate for LFP / UMTGA–Li and LFP / Cu–Li batteries; (b) shows the charge-discharge curves of LFP / UMTGA–Li battery at different test rates; and (c) shows the charge-discharge curves of LFP / Cu–Li battery at different test rates.

[0066] Figure 17 The images show the negative electrode morphology of the LFP full cell after cycling; (a)-(c) are SEM images of the negative electrode morphology of the LFP / UMTGA–Li cell; (d)-(f) are SEM images of the negative electrode morphology of the LFP / Cu–Li cell.

[0067] Figure 18 The graphs show the electrochemical performance of the full cell; (a) shows the rate performance test and subsequent long-cycle test at 3C rate for the NCM811 / UMTGA–Li and NCM811 / Cu–Li batteries; (b) shows the charge-discharge curves of the NCM811 / UMTGA–Li battery at different test rates; and (c) shows the charge-discharge curves of the NCM811 / Cu–Li battery at different test rates.

[0068] Figure 19 The images show the negative electrode morphology after full cell cycling; (a)-(c) are SEM images of the negative electrode morphology of the NCM811 / UMTGA–Li battery; (d)-(f) are SEM images of the negative electrode morphology of the NCM811 / Cu–Li battery.

[0069] The reference numerals in the detailed embodiments are as follows:

[0070] 10-Electrode; 1-Current collector; 2-Active material layer;

[0071] 20 - Electrode assembly; 101 - Negative electrode; 102 - Positive electrode; 201 - Negative electrode tab; 202 - Positive electrode tab; 203 - Separator;

[0072] 40 - Battery device;

[0073] 50 - Electrical appliance; 501 - Controller; 502 - Motor; Detailed Implementation

[0074] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0075] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0076] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0077] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0078] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0079] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0080] Lithium metal, as a battery anode material, possesses a high theoretical specific capacity, meaning that lithium metal batteries can store more electrical energy for the same weight. Lithium metal also has a low standard electrode potential, allowing it to generate higher voltages within the battery, thereby increasing its energy density. Despite these advantages, the practical application of lithium metal anodes still faces some challenges, primarily the difficulty in controlling lithium deposition and dissolution during charging and discharging, which can easily lead to the formation of uneven lithium dendrite structures on the anode surface. These dendrites not only degrade battery performance but may also pose safety risks.

[0081] Based on this, embodiments of this application propose a lithium metal battery cell, including a negative electrode sheet, the negative electrode sheet including a composite negative electrode material, the composite negative electrode material including a graphene composite material; the graphene composite material includes graphene and metal oxide particles loaded on the surface of graphene, the metal oxide including at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

[0082] The composite anode material in this application contains a variety of lithium-loving metal oxides (such as TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3). These metal oxides can form stable chemical bonds with lithium (such as Li-O bonds), thereby reducing the overpotential for lithium ion nucleation on the anode surface. This helps to uniformly deposit lithium ions on the anode surface and reduces the formation of lithium dendrites.

[0083] Graphene possesses a large specific surface area and porous structure, providing abundant lithium-ion deposition sites. Metal oxide particles loaded on the graphene surface further enhance the lithiophilicity of these sites, enabling uniform distribution and deposition of lithium ions on the material surface.

[0084] The composite structure of graphene and metal oxides can reduce the local current density of lithium ions during deposition, thus decreasing the formation of lithium dendrites. This helps extend the battery's cycle life and improve safety. The porous structure of graphene and the loading of lithium-philic metal oxides increase the material's electroactive surface area, improving the lithium-ion transport rate and charge storage capacity. This contributes to improving the overall electrochemical performance of the battery, including higher capacity and better rate performance.

[0085] In some embodiments, the number density deviation of metal oxide particles over at least 90% of the graphene area does not exceed ±15%.

[0086] The above data can be obtained through transmission electron microscopy (TEM). TEM images are acquired in multiple different sample regions. Using image processing software or manual techniques, the number of lithophile metal oxide particles in each selected image region is counted. The particle number density is obtained by dividing the number of particles in each image region by the area of ​​that region. The average particle number density of all selected image regions is calculated as the average particle number density of the entire sample. For the particle number density of each image region, its deviation from the average value is calculated. Using the above method, the results of multiple experiments in the samples of this application embodiment show that the particle number density deviation in at least 90% of the image regions does not exceed ±15%. This indicates that the distribution of lithophile metal oxide particles is very uniform in most graphene surface regions, without obvious aggregation or sparseness. This uniform distribution contributes to the uniformity of lithium metal deposition, reduces the non-uniformity of local current density, and thus further inhibits the growth of lithium dendrites.

[0087] In some embodiments, the average distance between any two adjacent metal oxide particles does not exceed 20 nm. This indicates that the spacing between particles is very small, forming dense lithiophilic sites. This high-density particle distribution can provide more lithium metal deposition sites, further promoting uniform lithium metal deposition.

[0088] In some embodiments, the mass of metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material. As examples, the mass percentage of metal oxide particles can be typical but not limiting values ​​such as 45%, 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, and 70%. By controlling the mass percentage of metal oxide particles within the above range, the graphene composite material can exhibit better lithiophilicity while retaining a certain proportion of graphene to maintain good conductivity. This balance helps improve the overall electrochemical performance of the battery.

[0089] In some embodiments, the specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g. This specific surface area is obtained through the BET specific surface area test. BET specific surface area refers to the specific surface area of ​​a material calculated using the Brunauer-Emmett-Teller (BET) theory. It represents the total surface area per unit mass of material, typically expressed in square meters per gram (m²). 2 The unit is (g). It is calculated by measuring the amount of nitrogen adsorbed by the material during the nitrogen adsorption and desorption process. As an example, the specific surface area of ​​the graphene composite material is 160 m². 2 / g、170m 2 / g、180m 2 / g、190m2 / g、200m 2 / g、210m 2 / g、220m 2 / g、230m 2 / g、240m 2 / g、250m 2 / g、260m 2 / g、270m 2 / g、280m 2 Typical but not limiting values ​​such as / g. This implies that graphene composites have a large specific surface area, providing more lithium metal deposition sites.

[0090] In some embodiments, the particle size of the graphene composite material is 5 μm to 30 μm. As an example, the particle size of the graphene composite material can be typical but not limiting values ​​such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm. This results in a graphene composite material with a moderate particle size, which is easy to disperse uniformly and improves overall performance.

[0091] In some embodiments, the particle size of the metal oxide particles is 5 nm to 30 nm. As an example, the particle size of the metal oxide particles can be typical but not limiting values ​​such as 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, and 30 nm. This indicates that the uniform particle size of the metal oxide particles is beneficial for guiding the uniform nucleation and deposition of lithium metal. Therefore, the composite anode material of this application embodiment has a flat and dense lithium deposition morphology.

[0092] In some embodiments, the metal oxide particles are TiO2 particles, and the TiO2 particles have mesopores.

[0093] The term "mesoporous" typically refers to pores with a diameter between 2 nm and 50 nm. The mesoporous structure of TiO2 particles can be ordered or disordered. Mesoporous structures can shorten electrolyte transport pathways and reduce concentration gradients in the electrolyte. During battery charging and discharging, the lithium-ion concentration in the electrolyte changes. Mesoporous TiO2, by providing more channels and a larger contact area, helps to achieve a more uniform distribution of lithium ions on the electrode surface, reducing localized excessively high or low concentrations, thereby lowering the concentration gradient.

[0094] In some embodiments, the pore size of the mesopores in the TiO2 particles is 3 nm to 5 nm. As examples, the pore size can be typical but not limiting values ​​such as 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm, 4 nm, 4.3 nm, 4.5 nm, 4.7 nm, and 5 nm.

[0095] In some embodiments, the composite anode material further includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

[0096] In some embodiments, the mass of lithium metal accounts for 25% to 80% of the total mass of the composite lithium metal anode material. As examples, the mass percentage of lithium metal can be typical but not limiting values ​​such as 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%. The mass percentage of lithium metal in the composite anode affects the battery's cycle performance and energy density. If the mass percentage of lithium metal is too low, it will result in insufficient active lithium, thus affecting cycle performance. Conversely, if the mass percentage of lithium metal is too high, it will lead to uneven lithium deposition, thereby affecting the battery's long-term cycle stability. Simultaneously, due to the increased anode volume, the battery's volumetric energy density will also decrease. Controlling the mass percentage of lithium metal in the composite lithium metal anode within the above-mentioned range allows for a better balance between battery safety, energy density, and cycle stability.

[0097] Secondly, embodiments of this application provide a composite negative electrode material, including a graphene composite material, which includes graphene and metal oxide particles loaded on the surface of the graphene. The metal oxide particles are made of at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

[0098] In some embodiments, the number density deviation of metal oxide particles over at least 90% of the area of ​​graphene does not exceed ±15%.

[0099] In some embodiments, the average distance between any two adjacent metal oxide particles does not exceed 20 nm.

[0100] In some embodiments, the mass of the metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material;

[0101] In some embodiments, the specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g;

[0102] In some embodiments, the particle size of the graphene composite material is 5 μm to 30 μm;

[0103] In some embodiments, the particle size of the metal oxide particles is 5 nm to 30 nm.

[0104] In some embodiments, the metal oxide particles are TiO2 particles, and the TiO2 particles have mesopores.

[0105] In some embodiments, the pore size of the mesopores in the TiO2 particles is 3 nm to 5 nm.

[0106] In some embodiments, the composite anode material further includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

[0107] In some embodiments, the mass of lithium metal accounts for 25% to 80% of the total mass of the composite anode material.

[0108] Thirdly, this application provides a method for preparing a composite negative electrode material, comprising the following steps: mixing a metal salt, a reducing sugar, graphene oxide and a solvent to obtain a mixed solution; the metal salt includes at least one of titanium salt, zinc salt, copper salt, zirconium salt, nickel salt, cobalt salt and aluminum salt; and subjecting the mixed solution to a hydrothermal reaction to obtain a graphene composite material.

[0109] The term "hydrothermal reaction" here refers to a chemical reaction carried out at high temperatures using water as a solvent. In a hydrothermal reaction, water is not only the solvent but also the reaction medium. Under suitable temperature conditions, hydrothermal reactions can promote crystal nucleation and growth, resulting in crystals with specific morphologies and sizes.

[0110] In the hydrothermal reaction process of this application embodiment, the metal salt is hydrolyzed to form a metal alkoxide complex, which is further dehydrated to generate metal oxide nanocrystals. Graphene sheets provide a substrate during the hydrothermal synthesis process, allowing the metal oxide nanocrystals to grow on them, forming a composite material.

[0111] Reducing sugars are sugars that can act as reducing agents. They contain free aldehyde groups (-CHO) or ketone groups (-CO-), which can react with certain oxidizing agents, causing the latter to be reduced. Common reducing sugars include glucose, fructose, lactose, and maltose.

[0112] Reducing sugars, through their hydroxyl groups, coordinate with metal oxide nanocrystals, promoting the anchoring and uniform dispersion of metal oxides on the graphene surface, thus resulting in high dispersibility of the in-situ grown metal oxide particles. Inorganic metal salts can be selected, such as titanium salts, zinc salts, copper salts, zirconium salts, nickel salts, cobalt salts, and aluminum salts; suitable choices include Ti(SO4)2, ZnSO4, CuSO4, Zr(SO4)2, NiSO4, CoSO4, and Al2(SO4)3.

[0113] The addition of reducing sugars enhances the interaction between metal oxide particles and the graphene substrate. This is because the aldehyde groups in the reducing sugar molecules have reducing properties, which can not only reduce graphene oxide to obtain highly conductive, three-dimensionally porous reduced graphene oxide (rGO), but also form MOC bonds between the metal oxide and graphene, where M represents a metal element. This bonding makes the bond between the metal oxide particles and graphene more robust. The TiO2 particles prepared by this method also exhibit mesoporous properties.

[0114] In some embodiments, the hydrothermal reaction temperature is 160°C to 200°C. In a hydrothermal reaction, temperature has a significant impact on the solubility of substances and the reaction rate. As examples, the hydrothermal reaction temperature can be typical but not limiting values ​​such as 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, and 200°C. Controlling the hydrothermal reaction temperature within the above range can improve the solubility of reactants in the solvent and further promote crystal nucleation and growth. In some alternative embodiments, the hydrothermal reaction temperature is 170°C to 190°C.

[0115] In some embodiments, the hydrothermal reaction time is 10 h to 14 h. The hydrothermal reaction time affects the crystal growth and morphology. A shorter time may result in incomplete crystal growth, while a longer time may result in overgrowth. As examples, the hydrothermal reaction time can be typical but not limiting values ​​such as 10 h, 11 h, 12 h, 13 h, and 14 h. Controlling the hydrothermal reaction time within the above range helps to prepare materials with better morphology and properties. In some optional embodiments, the hydrothermal reaction time is 11 h to 13 h.

[0116] In some embodiments, the concentration of graphene oxide in the mixed solution is 1.5 mg / mL to 2.5 mg / mL. The concentration of graphene oxide affects the strength and morphology of the synthesized material. If the concentration is too low, the synthesized material may become brittle due to insufficient bonding between the graphene oxide sheets; while if the concentration is too high, the material may easily stack, affecting its porosity and electrochemical properties. As examples, the concentration of graphene oxide in the mixed solution can be typical but not limiting values ​​such as 1.5 mg / mL, 1.8 mg / mL, 2.0 mg / mL, 2.1 mg / mL, 2.3 mg / mL, and 2.5 mg / mL.

[0117] In some embodiments, the mass ratio of graphene oxide to metal salt is 1:(2.5–5). This ratio affects the interaction between graphene oxide and the metal oxide and the formation of the composite structure. As examples, the mass ratio of graphene oxide to metal salt can be typical but not limiting values ​​such as 1:2.5, 1:3, 1:3.5, 1:3.5, 1:4, 1:4.5, and 1:5. Regulating the mass ratio of graphene oxide to metal salt within the above range allows for a uniform distribution of metal oxide particles on the graphene oxide sheets, avoiding agglomeration caused by excessively high local concentrations.

[0118] In some embodiments, the mass ratio of glucose to metal salt is 1:(10-20). Glucose plays two key roles in the hydrothermal reaction: as a coordination anchoring agent and as a reducing agent. If too little glucose is added, it may not achieve the anchoring effect, affecting the uniformity of dispersion. If too much glucose is added, the solution will become viscous, which is not conducive to the reaction and the formation of the material. As examples, the mass ratio of glucose to metal salt can be typical but not limiting values ​​such as 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and 1:20. Controlling the mass ratio of glucose to metal salt within the above range allows for better control of the morphology and structure of the material.

[0119] In some embodiments, lithium metal is deposited on the surface and / or in the pores of the graphene composite material using electrochemical deposition or self-discharge.

[0120] Electrochemical deposition is a method that uses an electric current to reduce and deposit metal ions onto a graphene composite material. In a specific example, electrochemical deposition of lithium metal includes the following steps: assembling a coin cell using a graphene composite material as the positive electrode material, copper foil as the positive electrode current collector, and lithium metal as the negative electrode; discharging the coin cell at a specific current density to deposit lithium metal; disassembling the coin cell; cleaning and drying the positive electrode to obtain the composite negative electrode material.

[0121] "Self-discharge" refers to the process by which lithium metal deposits on the surface or in the pores of a graphene composite material due to its interaction with the material in the absence of an external current. In a specific example, a micro-galvanic cell is formed by using a graphene composite material as the positive electrode material and copper foil as the positive electrode current collector. An electrolyte is then dropped onto this positive electrode, and a lithium sheet is tightly bonded to it to form a micro-galvanic cell. After a certain period of self-discharge, the composite negative electrode material is prepared.

[0122] Both electrochemical deposition and self-discharge methods can be used to bond lithium metal to graphene composites. Electrochemical deposition allows for better control of the deposition process. The above preparation method combines the advantages of graphene and metal oxides, achieving high lithium affinity, uniform lithium deposition, and suppression of lithium dendrite growth. The method involves providing a graphene composite material and depositing lithium metal onto the surface and pores of the graphene composite material. This method is simple and easy to operate.

[0123] In some embodiments, a coin cell is constructed by combining graphene composite material with lithium metal, and the coin cell is subjected to electrochemical discharge deposition on a charge / discharge apparatus at a current density of 0.5 mA / cm². 2 ~5mA / cm 2 The deposition rate was 0.5 mg / cm³. 2 ~14mg / cm 2 After deposition, the coin cell was disassembled to obtain the composite anode material.

[0124] In some embodiments, an electrolyte is dropped onto a graphene composite material, and lithium metal is bonded to the graphene composite material to form a primary battery. After 1 to 5 hours of self-discharge, a composite negative electrode material is obtained.

[0125] Fourthly, embodiments of this application provide a battery device including the aforementioned lithium metal battery cell, thereby improving the performance of the battery device by employing the aforementioned lithium metal battery cell.

[0126] The following is a detailed description of each component of a lithium metal battery cell.

[0127] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the electrode 10 in some embodiments of this application. The electrode 10 includes a current collector 1 and an active material layer 2, the active material layer 2 being disposed on at least one side of the current collector 1.

[0128] Current collector 1 refers to the component used to collect current. Current collector 1 can be a negative current collector. Generally, it can be copper foil; the corresponding active material layer 2 coated on the negative current collector is a negative active material layer, and the resulting electrode 10 is a negative electrode electrode. In addition, current collector 1 can be of various shapes, such as strip or square, which is not limited here.

[0129] The active material layer 2 includes a graphene composite material and a binder. The graphene composite material serves as a framework for lithium metal deposition and can be directly used as a negative electrode in a full cell, forming a negative electrode-free lithium metal full cell; alternatively, it can be used as a conventional lithium metal composite negative electrode after pre-depositing lithium metal to form a composite electrode. Optionally, the graphene composite material is in powder form. The binder is a material that binds the graphene composite material together to enhance the electronic contact between the composite material and the current collector 1. The binder can be, but is not limited to, styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyacrylate (PAA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), etc.

[0130] The current collector 1 has a first surface and a second surface opposite to each other along the thickness direction of the current collector 1. At least one side of the current collector 1 includes the first surface and / or the second surface of the current collector 1. It is understood that the active material layer 2 may be disposed on the first surface, or on the second surface, or the active material layer 2 may be disposed on both the first surface and the second surface.

[0131] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the electrode assembly 20 in some embodiments of this application. The electrode assembly 20 is the component in the battery where the electrochemical reaction occurs. The electrode assembly 20 is mainly formed by winding or stacking an electrode structure that integrates a negative electrode 101 and a positive electrode 102, and a separator 203 is usually provided between adjacent negative electrode 101 and positive electrode 102.

[0132] [Negative electrode plate]

[0133] The negative electrode 101 includes a negative electrode current collector and a negative electrode material layer, the negative electrode material layer being coated on the surface of the negative electrode current collector. Taking a lithium metal battery as an example, the material of the negative electrode current collector can be copper, and the negative electrode active material can be metallic lithium. The negative electrode can include a lithium metal negative electrode (including no negative electrode), a carbon material negative electrode, and other non-carbon material negative electrodes.

[0134] It should be noted that "negative electrode-free" refers to a secondary battery that uses copper foil directly as the negative electrode, without any pre-deposited active lithium metal. The working principle of a negative electrode-free battery is as follows: during charging, lithium ions in the lithium-containing positive electrode material pass through the separator and combine with electrons transferred from the external circuit to form lithium metal, which is then deposited on the copper foil of the negative electrode current collector. During discharging, the lithium metal on the copper foil of the negative electrode current collector dissolves and returns to the electrolyte, then passes through the separator and is re-embedded in the positive electrode material.

[0135] In some embodiments, the negative electrode active material may further include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and tin-based materials.

[0136] In some embodiments, the negative electrode active material may also include a binder. Examples of binders include styrene-butadiene rubber, polyacrylate, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0137] In some embodiments, the negative electrode active material further includes a conductive agent. Examples of conductive agents include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, etc.

[0138] In some embodiments, the negative electrode sheet of a lithium metal battery can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent to form a negative electrode slurry, coating the negative electrode slurry onto a negative electrode current collector, and obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0139]

Positive Electrode

[0140] The positive electrode 102 includes a positive current collector and a positive active material layer, with the positive active material layer coated on the surface of the positive current collector. Taking a lithium metal battery as an example, the material of the positive current collector can be aluminum, and the positive material layer includes the positive electrode material, which can be lithium iron phosphate, ternary positive electrode material, etc.

[0141] In some embodiments, the positive electrode sheet of a lithium metal battery can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent to form a positive electrode slurry, coating the positive electrode slurry onto a positive current collector, and obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0142]

Isolation Film

[0143] The separator 203 is a porous plastic film that allows lithium ions in the electrolyte to pass through freely, but isolates the negative electrode 101 and the positive electrode 102, preventing electrons inside the battery from passing through freely. The separator 203 can be made of materials such as PP (polypropylene) or PE (polyethylene).

[0144] Fifthly, embodiments of this application provide an electrical device, including a lithium metal battery cell (as described in the first aspect) or a battery device (as described in the third aspect). The lithium metal battery cell or battery device is used to store or provide electrical energy. The performance of the electrical device using the aforementioned lithium metal battery cell is improved.

[0145] The lithium metal battery cells or battery devices disclosed in some embodiments of this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power system comprising the batteries disclosed in this application can be used to construct such an electrical device.

[0146] Electrical devices can include, but are not limited to, vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools. Vehicles can include, but are not limited to, gasoline-powered cars, natural gas-powered cars, or new energy vehicles. New energy vehicles can include, but are not limited to, pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles. Spacecraft include airplanes, rockets, space shuttles, and spacecraft. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0147] For ease of explanation, the following embodiments will be described using a vehicle 50 as an example of an electrical device according to an embodiment of this application.

[0148] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 50 provided in some embodiments of this application. A battery device 40 is disposed inside the vehicle 50, and the battery device 40 may be located at the bottom, front, or rear of the vehicle 50. The battery device 40 can be used to power the vehicle 50; for example, the battery device 40 can serve as the operating power source for the vehicle 50. The vehicle 50 may also include a controller 501 and a motor 502. The controller 501 is used to control the battery device 40 to supply power to the motor 502, for example, to meet the power needs of the vehicle 50 during starting, navigation, and driving.

[0149] In some embodiments of this application, the battery device 40 can not only serve as the operating power source for the vehicle 50, but also as the driving power source for the vehicle 50, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 50.

[0150] In some embodiments of this application, the battery device 40 may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells connected in series, parallel, or mixed configurations via a busbar.

[0151] A single battery cell can be a rechargeable battery. A rechargeable battery is a battery cell that can be recharged after it has been discharged, allowing the active materials to be activated and the cell to continue to be used.

[0152] The battery cells can be lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0153] The following description is based on specific embodiments.

[0154] Example 1

[0155] This embodiment provides a lithium metal battery cell, the negative electrode of which includes a composite negative electrode material, the composite negative electrode material including a graphene composite material; the graphene composite material includes graphene and TiO2 particles loaded on the surface of graphene.

[0156] (1) Preparation of composite anode materials without lithium metal

[0157] This composite anode material is a graphene composite material, comprising graphene and TiO2 particles in situ grown on the graphene surface. The TiO2 particles account for 65.8% of the total mass of the graphene composite material. The TiO2 particles have mesopores with a pore size of 3 nm to 5 nm. The specific surface area of ​​this graphene composite material is 275.4 m². 2 / g.

[0158] Its preparation method includes the following steps:

[0159] 0.8 g Ti(SO4)2, 40 mg glucose, and 0.16 g graphene oxide were added to a beaker, and distilled water was added to prepare an 80 mL mixed solution with a final graphene oxide concentration of 2 mg / mL. After stirring and sonicating for one hour, the mixed solution was transferred to the inner liner of a reactor. The inner liner was placed in an octagonal screw reactor and kept at 180°C for 12 hours in an oven. After the reactor was allowed to cool naturally to room temperature, the material was removed, cleaned, and freeze-dried to obtain the graphene composite material, i.e., a lithium-free composite anode material, denoted as UMTGA.

[0160] (2) Preparation of UMTGA electrode

[0161] UMTGA and polyvinylidene fluoride (PVDF) binder were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 9:1. The slurry was then coated onto the copper foil current collector, and the electrode was dried at 60°C for 24 hours.

[0162] (3) Diaphragm

[0163] The diaphragm used is a Celgard 2325 disc diaphragm with a diameter of 19 mm.

[0164] (4) Preparation of half-cell

[0165] The UMTGA electrode, separator, and lithium metal sheet were stacked in sequence, with the UMTGA electrode as the working electrode and the lithium metal sheet as the counter electrode, to assemble a coin cell. Assembly was completed in an argon-filled glove box with O2 < 0.1 ppm and H2O < 0.1 ppm. The electrolyte was a mixed solvent of 1,3-dioxolane (DOL) and dimethoxyethane (DME) in a 1:1 volume ratio, containing 1 mol of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) per liter of electrolyte and 2 wt.% LiNO3.

[0166] (5) Preparation of negative electrode sheet and preparation of composite negative electrode material containing lithium metal

[0167] The above half-cell was subjected to 1 mA / cm 2 Discharged at a current density of 12 mAh / cm³, with the discharge cutoff capacity set at 12 mAh / cm³. 2 A corresponding 12 mAh / cm² deposit was formed on the working electrode. 2 The lithium metal was then used. The half-cell was then disassembled, and the working electrode was cleaned with dimethyl ethylene glycol (DME) and dried to obtain the negative electrode sheet. The negative electrode sheet consisted of a copper foil current collector and a composite negative electrode material containing lithium metal, with the lithium metal accounting for 68.4% of the total mass of the composite negative electrode material.

[0168] (6) Preparation of LFP full cells

[0169] Lithium iron phosphate (LiFePO4), carbon black (COP), and polyvinylidene fluoride (PVDF) (PVDF) were dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto an aluminum foil current collector. After drying in an oven at 80°C, a layer of positive electrode active material was obtained, which was then rolled and slit to obtain the LFP positive electrode sheet.

[0170] The LFP positive electrode, separator, and negative electrode were stacked in sequence and assembled in an argon-filled glove box with O2 < 0.1 ppm and H2O < 0.1 ppm. The electrolyte was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio, containing 1 mol of lithium hexafluorophosphate (LiPF6) per liter, and 1 wt% vinylene carbonate (VC) and 10 wt% fluoroethylene carbonate (FEC).

[0171] (6) Preparation of NCM full cells

[0172] The positive electrode active material is NCM811 (a nickel-cobalt-manganese ternary positive electrode material, specifically with the chemical formula LiNi). 0.8 Co 0.1 Mn 0.1O2), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector aluminum foil. After drying in an oven at 80°C, a positive electrode active material layer is obtained, which is then rolled and slit to obtain an NCM positive electrode sheet.

[0173] The NCM positive electrode, separator, and negative electrode were stacked in sequence and assembled in an argon-filled glove box with O2 < 0.1 ppm and H2O < 0.1 ppm. The electrolyte was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio, containing 1 mol of lithium hexafluorophosphate (LiPF6) per liter, and 1 wt% vinylene carbonate (VC) and 10 wt% fluoroethylene carbonate (FEC).

[0174] Example 2

[0175] The difference between Example 2 and Example 1 is that the amount of each reactant added is different in the preparation process of the graphene composite material.

[0176] This graphene composite material comprises graphene and TiO2 grown in situ on the graphene surface, with TiO2 particles accounting for 53.8% of the total mass of the graphene composite material. The TiO2 particles are mesoporous, with pore sizes ranging from 3 nm to 5 nm. The specific surface area of ​​this graphene composite material is 248.7 m². 2 / g.

[0177] Its preparation method includes the following steps:

[0178] 0.42 g Ti(SO4)2, 40 mg glucose, and 0.16 g graphene oxide were added to a beaker, and distilled water was added to prepare an 80 mL solution with a final graphene oxide concentration of 2 mg / mL. After stirring and sonicating for one hour, the mixture was transferred to the inner liner of a reactor. The inner liner was placed in an octagonal screw reactor and kept at 180°C for 12 hours. Afterward, the reactor was allowed to cool naturally to room temperature, the material was removed, cleaned, and freeze-dried to obtain the graphene composite material.

[0179] Example 3

[0180] The difference between Example 3 and Example 1 is that the amount of each reactant added is different in the preparation process of the graphene composite material.

[0181] This graphene composite material comprises graphene and TiO2 grown in situ on the graphene surface, with TiO2 particles accounting for 58.40% of the total mass of the graphene composite material. The TiO2 particles are mesoporous, with pore sizes ranging from 3 nm to 5 nm. The specific surface area of ​​this graphene composite material is 259.6 m². 2 / g.

[0182] Its preparation method includes the following steps:

[0183] 0.6 g Ti(SO4)2, 40 mg glucose, and 0.16 g graphene oxide were added to a beaker, and distilled water was added to prepare an 80 mL solution with a final graphene oxide concentration of 2 mg / mL. After stirring and sonicating for one hour, the mixture was transferred to the inner liner of a reactor. The inner liner was placed in an octagonal screw reactor and kept at 180°C for 12 hours. Afterward, the reactor was allowed to cool naturally to room temperature, the material was removed, cleaned, and freeze-dried to obtain the graphene composite material.

[0184] Example 4

[0185] The difference between Example 4 and Example 1 is that the mass of lithium metal accounts for 30% of the total mass of the composite anode material.

[0186] Its preparation method includes the following steps:

[0187] A coin cell was assembled using a UMTGA electrode as the positive electrode and lithium metal as the negative electrode. The coin cell achieved an output of 1 mA / cm². 2 Discharge at a current density of 0V, with a discharge cutoff capacity below 0V set at 5mAh / cm³. 2 Corresponding to a deposition of 5mAh / cm 2 Lithium metal is used to form a composite lithium metal electrode material. The coin cell is then disassembled, and the electrodes are cleaned with dimethyl ethylene glycol (DME), dried, and the composite lithium metal electrode material is obtained.

[0188] Example 5

[0189] The difference between Example 5 and Example 1 is that the graphene composite material includes graphene and ZnO grown in situ on the graphene surface, with the ZnO particles accounting for 45.8% of the total mass of the graphene composite material. The specific surface area of ​​this graphene composite material is 172.5 m². 2 / g.

[0190] Its preparation method includes the following steps:

[0191] 0.54 g ZnSO4, 40 mg glucose, and 0.16 g graphene oxide were added to a beaker, and distilled water was added to prepare an 80 mL solution with a final graphene oxide concentration of 2 mg / mL. After stirring and sonicating for one hour, the mixture was transferred to the inner liner of a reaction vessel. The inner liner was placed in an octagonal screw reaction vessel and kept in an oven at 180°C for 12 hours. Afterward, the reaction vessel was allowed to cool naturally to room temperature, the material was removed, cleaned, and freeze-dried to obtain the graphene composite material.

[0192] Example 6

[0193] The difference between Example 6 and Example 1 is that the graphene composite material includes graphene and Al2O3 grown in situ on the graphene surface, with the Al2O3 particles accounting for 50.2% of the total mass of the graphene composite material. The specific surface area of ​​this graphene composite material is 169.4 m². 2 / g.

[0194] Its preparation method includes the following steps:

[0195] 1.14 g Al2(SO4)3, 40 mg glucose, and 0.16 g graphene oxide were added to a beaker, and distilled water was added to prepare an 80 mL solution with a final graphene oxide concentration of 2 mg / mL. After stirring and sonicating for one hour, the mixture was transferred to the inner liner of a reactor. The inner liner was placed in an octagonal screw reactor and kept in an oven at 180°C for 12 hours. Afterward, the reactor was allowed to cool naturally to room temperature, the material was removed, cleaned, and freeze-dried to obtain the graphene composite material.

[0196] Comparative Example 1

[0197] The difference between Comparative Example 1 and Example 1 is that the negative electrode material of Comparative Example 1 is reduced graphene oxide.

[0198] Comparative Example 2

[0199] The difference between Comparative Example 2 and Example 1 is that the negative electrode sheet of Comparative Example 2 is made of copper foil (without negative electrode material), and the working electrode of the half cell is also made of copper foil.

[0200] Material property testing

[0201] To verify the progressiveness of the embodiments of this application, the samples of the embodiments and comparative examples were subjected to the following tests:

[0202] 1. X-ray diffraction (XRD)

[0203] Powder X-ray diffraction (XRD) can be used to analyze the composition, crystal phase, and crystal structure of materials, possessing strong analytical capabilities. Its principle is as follows: X-rays are irradiated onto the material, causing reflection, and the reflected X-rays undergo interference. According to nλ = 2dsinθ, under a fixed wavelength, different interplanar spacings d will result in corresponding changes in the diffraction angle θ. Therefore, phase analysis can be achieved by using the characteristic diffraction angles corresponding to the characteristic crystal planes of different materials. The relative positions of atoms can be determined by the magnitude of the diffraction peak intensities. In this application, XRD was performed using a Rigaku (Ultima IV–185) X-ray diffractometer. The test parameters were: Cu target / Kα rays, tube voltage 40kV, tube current 40mA, and wavelength... The scanning speed is 6° / min, the step size is 0.02°, and the scanning range is 5° to 90°.

[0204] 2. Scanning electron microscope (SEM)

[0205] Scanning electron microscopy (SEM) uses an electron beam to scan the sample surface to obtain information about the material's surface morphology. When the electron beam bombards the sample surface, the interaction between the electron beam and the material generates secondary and scattered electrons, which, through further processing, become the corresponding morphological image. SEM resolution is approximately 2 nm. Through SEM testing, in-depth and detailed analysis of the microstructure and structure of materials can be performed, and the morphology of lithium metal deposition can be well characterized. This application uses a Hitachi S-4800 scanning electron microscope (Japan) to characterize the material morphology and lithium metal deposition morphology.

[0206] 3. Energy-dispersive X-ray spectroscopy (EDX)

[0207] Energy-dispersive X-ray spectroscopy (EDX) is often combined with surface imaging (SEM) for testing. By performing EDX tests on selected areas, the elemental distribution and composition information of the material surface can be obtained intuitively. EDX can also perform semi-quantitative analysis of different atomic percentages in materials. This application uses a TECNAI G2F20 energy dispersive spectrometer from the Netherlands to test and analyze the elemental composition of the material surface.

[0208] 4. Transmission electron microscope (TEM)

[0209] Transmission electron microscopy (TEM) can observe fine structures below 200 nm. TEM focuses an electron beam onto the surface of a thin sample, producing solid-angle scattering. The scattering angle is related to the sample morphology and thickness, thus forming a corresponding image. TEM can study material morphology and the size of loaded particles, while high-magnification lenses, due to their high magnification, can analyze the phase composition of the material by measuring the lattice fringe spacing. This application uses a TEM from JEOL Ltd. (JEOL – 2010) to analyze the material morphology and particle size.

[0210] 5. X-ray photoelectron spectroscopy (XPS)

[0211] X-ray photoelectron spectroscopy (XPS) is a commonly used testing method for surface analysis. XPS signal depth is 3 nm. When X-rays irradiate the sample surface, electrons are excited to form photoelectrons. Different elements produce photoelectrons with different energies. Therefore, by analyzing the photoelectron energies, information about the elemental composition and chemical bonding of the material surface can be obtained. This patent uses the monochromatic Al Kα (1486.6 eV) light source of a Thermo Fisher Scientific (ESCALAB 250Xi) photoelectron spectrometer to perform qualitative and quantitative analysis of the elemental chemical composition of the material surface.

[0212] 6. Fourier Transform Infrared Spectroscopy (FT-IR)

[0213] Fourier transform infrared spectroscopy (FT-IR) is an effective method for analyzing functional groups on the surface of materials. It works by irradiating the material surface with infrared light; due to the stretching vibrations and rotations of molecules on the surface, they absorb infrared light and undergo transitions. By recording the absorption of infrared light by the molecules, an infrared spectrum is obtained. The distribution information of functional groups on the material surface can be obtained by comparing the spectrum with the positions of standard absorption peaks. Sample preparation typically involves grinding and mixing the sample with KBr, pressing it into a thin sheet, and fixing it onto a test piece for infrared testing. This patent uses a Thermal (Nicolet IS10) Fourier transform infrared spectrometer from the USA for qualitative analysis of the functional groups on the material surface, with 10 scans and a resolution of 4 cm⁻¹. –1 The test range is 4000cm. –1 ~500cm –1 .

[0214] 7. Scanning Transmission Electron Microscopy (STEM)

[0215] Scanning transmission electron microscopy (STEM) combines the technical features of transmission electron microscopy (TEM) and scanning electron microscopy (SEM), providing high-resolution images and detailed elemental analysis. It can capture HAADF-STEM (High-Angle Annular Dark Field-Scanning Transmission Electron Microscopy) images and is mainly used for high-resolution material characterization.

[0216] 8. Specific surface area and pore size distribution analysis (BET)

[0217] Specific surface area measurement (Brunauer-Emmett-Teller, BET method) is a commonly used method for characterizing the pore structure and pore size distribution of materials. This application uses an ASAP 2460 physical adsorption analyzer (USA) to measure and characterize the specific surface area and pore size distribution of the materials.

[0218] 9. DFT theoretical simulation calculation

[0219] Based on the first principles of density functional theory (DFT), this study primarily employs the generalized gradient approximation (GGA) and the Perdew-Burke-Ernzerhof (PBE) functional for theoretical calculations. Projected enhanced wave (PAW) potentials were chosen to describe the interactions between ion nuclei. Furthermore, a plane-wave basis set with a kinetic energy cutoff of 450 eV was used to consider valence electrons. The Gaussian tailing method and a width of 0.05 eV were used to allow partial occupancy of the Kohn-Sham orbitals. When the energy change is less than 10... –5 At eV, the electron energy is considered self-consistent. When the energy change is less than eV... At this point, geometric optimization is considered convergent. In the model, a vacuum spacing perpendicular to the structural plane is set. Brillouin zone integration was performed on the structure using 4×4×1 Monkhorst-Pack k-point sampling. Finally, the adsorption energy (Eads) was calculated as Eads = Ead / sub - Ead - Esub, where Ead / sub, Ead, and Esub are the optimized adsorbate / substrate system, the adsorbate in the structure, and the pure surface structure, respectively. This application primarily selected TiO2(101) and TiO2(001) surfaces to calculate the adsorption and migration energies. TiO2(101) and TiO2(001) refer to different crystal planes of titanium dioxide (TiO2). U-correction was applied for Ti. Finally, the migration path was determined using the climbing elastic band method.

[0220] 10. COMSOL Lithium Ion Concentration Distribution Simulation

[0221] Finite element analysis performed by COMSOL Multiphysics is frequently used to study multi-field coupling and concentration distribution. In this application, the migration of lithium ions in the liquid (electrolyte) and solid phases is considered in the model, driven by both electric field and diffusion.

[0222] The finite element simulation employs a coupled physical model of electrostatic and diffused mass transport, with the following equations:

[0223]

[0224] In the formula, φ represents the electric potential, E represents the electric field, D is the lithium-ion diffusion coefficient, c is the lithium-ion concentration, u is the lithium-ion mobility in the electrolyte, N is the lithium-ion flux vector, and t is the diffusion time. These structures are simulated using a conventional model domain with finite element methods. In the calculation, the potential difference through the electrolyte is set. The value was 8 mV. To study the ion transport behavior of a finite liquid electrolyte during long-term cycling, the same physical model was established, and the ratio of the diffusion coefficient of Li ions in the liquid electrolyte to that in the solid particles was reduced to 10.0. The mobility of lithium ions in both the liquid electrolyte and the solid particles was defined by the Nernst-Einstein equation. Other boundary conditions were that the bottom boundary of the two simulation regions was a Dirichlet boundary with φ0 = 0 V and c0 = 0 M, and the top boundary was also a Dirichlet boundary with φ1 = 1 mV and c1 = 1.0 M. This application uses COMSOL finite element simulation to simulate the lithium ion concentration distribution field on the material surface to theoretically explain the material's advantages and dendrite suppression effect.

[0225] Material property results

[0226] Figure 4 The diagram illustrates the synthesis process of the graphene composite material UMTGA in Example 1 and the deposition behavior of lithium metal. In the synthesis of the graphene composite material UMTGA, mesoporous TiO2 particles are in-situ loaded onto the surface of graphene sheets using the anchoring effect of glucose and a hydrothermal reaction. Following a subsequent freeze-drying process, the graphene composite material UMTGA is obtained. In the preparation of the composite anode material containing lithium metal, lithium metal is electrochemically deposited onto the graphene composite material. As discharge proceeds, UMTGA first undergoes a pre-lithiation stage, followed by preferential nucleation of lithium metal on the highly lithiophilic TiO2 particles. Subsequently, lithium metal undergoes further deposition and growth within the UMTGA.

[0227] like Figure 5 These are some spectra of UMTGA from Example 1, wherein, Figure 5Images (a)-(b) in the table are SEM images, showing that UMTGA exhibits a porous structure with clearly visible pores. When magnified to a scale bar of 200 nm, TiO2 nanoparticles can be seen loaded onto the surface of the graphene sheets. Figure 5 Images (c)-(d) in the figure are TEM images, which further demonstrate that the graphene sheet surface is uniformly and densely loaded with nanoparticles, with a particle size of about 20 nm. Figure 5 (e) in the image shows the HAADF-STEM image and the corresponding elemental distribution, indicating that C is uniformly distributed in the selected region, O and Ti have similar profiles, and the signal is concentrated at the white nanoparticles, demonstrating the successful loading and hyperdispersion of TiO2.

[0228] Figure 6 These are some spectra of UMTGA from Example 1, wherein, Figure 6 Images (a)-(b) in the image are high-magnification UMTGA images, showing that the nanoparticles have a typical lattice fringe spacing of 0.352 nm, corresponding to the (101) crystal plane of TiO2. Furthermore, the presence of voids between the nanoparticles indicates that the TiO2 particles are mesoporous, with pore sizes between 3 and 5 nm.

[0229] Figure 6 (c)-(d) are STEM images from UMTGA. This high-angle annular dark-field image shows that there are many black voids in the middle of the white TiO2 nanoparticles, indicating the mesoporous nature of TiO2.

[0230] Figure 7 These are some spectra of UMTGA from Example 1. Figure 7 (a) in the figure is the XRD spectrum of UMTGA, which shows that graphene and TiO2 were successfully combined in UMTGA. The structure of TiO2 belongs to the anatase type, and a characteristic peak appears at the corresponding 2θ position. Figure 7 (b) is the XPS plot of UMTGA, which shows that the atomic proportions of C, O and Ti in UMTGA are 65.41%, 26.6% and 7.99%, respectively. Figure 7 (c) shows the infrared spectrum of UMTGA, indicating that both GA and UMTGA contain C–O–C functional groups in addition to the –OH functional group. This is because during the hydrothermal reaction, the C–O–C, C–OH, and O=C–OH functional groups in graphene oxide can react with the –OH groups in glucose molecules to form C–O–C bonds, while UMTGA still contains C–O–C bonds at 400 cm⁻¹. -1 ~800cm -1 There is a peak within the range, which corresponds to the Ti–O–C bond. This indicates that there is a valence bond between TiO2 nanoparticles and graphene, which is grown in situ on the surface of graphene sheets.

[0231] Figure 7 (d) in the figure represents the BET nitrogen adsorption-desorption isotherm of UMTGA, indicating that the composite material UMTGA has a temperature of 275.4 m. 2 The large specific surface area of ​​ / g and the obvious saturation adsorption plateau and hysteresis loop in the curve indicate that the material contains mesoporous material. Figure 7 (e) in the figure is the pore size distribution diagram of UMTGA. The pore size distribution curve also shows that the material contains a hierarchical pore structure with pore sizes of 0.68 nm, 1.27 nm, 3.18 nm, 5.04 nm, 25.25 nm, 34.33 nm, and 68.50 nm. Figure 6 The HRTEM images (a)-(b) show that the mesopore size of TiO2 is mainly 3.18 nm and 5.04 nm.

[0232] Thermogravimetric analysis was performed on UMTGA in air atmosphere, and the results are as follows: Figure 7 As shown in (f), graphene undergoes a thermal reaction as temperature increases, leading to a decrease in the mass of the composite material. Some oxidation reactions occur in localized temperature regions, resulting in a very small increase in mass, which is normal. At 800℃, the mass tends to stabilize, at which point the remaining mass is the mass of TiO2, indicating that TiO2 accounts for 65.8% of the total mass of the composite material.

[0233] like Figure 8 As shown, the binding energy between the material and lithium atoms was simulated using first-principles calculations. The results show that lithium has the highest binding energy with graphene loaded with TiO2 (two different crystal planes), with the highest binding energy (4.93 eV) between lithium and graphene loaded with (101)-type TiO2. Anatase TiO2 is mainly (101)-type, indicating that the introduction of TiO2 can enhance the lithium affinity of the composite material and reduce the nucleation overpotential. A high binding energy of 4.77 eV is also found between lithium and graphene loaded with (001)-type TiO2. The lowest binding energies are between lithium atoms and copper, and between lithium atoms and graphene, at 2.62 eV and 1.25 eV, respectively.

[0234] like Figure 9 As shown, DFT simulations of the lithium-ion diffusion pathway indicate that the energy barrier for lithium migration is lowest in the graphene composite material with (101)-plane TiO2, followed by the graphene composite structure with (001)-plane TiO2. This suggests that the composite material can accelerate lithium-ion diffusion and migration, reduce the lithium-ion concentration gradient, and facilitate the formation of a uniform lithium deposition morphology and the acquisition of rapid reaction kinetics.

[0235] like Figure 10 As shown, the lithium ion concentration gradients on the surfaces of copper, graphene, and TiO2-loaded graphene were simulated using COMSOL. Figure 10In the figure, (a)-(c) correspond to the simulation of the lithium ion concentration distribution field on the surface of the three electrodes, while Figure 10 Figures (d)-(f) in the figure correspond to the simulated lithium growth morphology on the three electrode surfaces. As shown in the figure, lithium on the copper surface easily forms a tip effect, generating lithium dendrites; on the graphene surface, the lithium ion concentration distribution is relatively uniform, but rounded protrusions are also generated, resulting in an uneven and irregular growth morphology. In contrast, the TiO2-loaded graphene surface exhibits a uniform lithium ion flow distribution, yielding a uniform and smooth deposition morphology.

[0236] Half-cell performance test

[0237] 1. Deposition and stripping behavior test

[0238] The half-cell of Example 1 was subjected to an A / cm test at 0.5 mA / cm. 2 At current density, controlling the discharge capacity below 0V corresponds to a lithium deposition rate of 1 mAh / cm³. 2 3mAh / cm 2 5mAh / cm 2 After deposition, the battery was disassembled, the electrodes were cleaned and dried in a glove box to obtain the working electrode for morphology characterization.

[0239] Figure 11 The deposition and stripping behavior of lithium metal on UMTGA electrodes is shown: as follows Figure 11 As shown, SEM electron microscopy results indicate that as the lithium deposition amount increases from 1 mAh / cm³, the lithium deposition rate increases from 1 mAh / cm³ to 1 mAh / cm³. 2 ( Figure 11 (a) to 3mAh / cm 2 ( Figure 11 From (b) to 5mAh / cm 2 ( Figure 11 In (c), the electrode exhibits a dendrite-free morphology, allowing lithium metal to fill the pores within the graphene. However, as the exfoliation capacity increases ( Figure 11 In (d)-(f), the electrode still exhibits a dendrite-free morphology, with lithium metal peeled off from the framework. Magnified SEM images reveal the framework structure of UMTGA, indicating that UMTGA effectively suppresses lithium dendrite growth and demonstrates good reversibility. These SEM analyses demonstrate that UMTGA can effectively reduce the contact area between lithium metal and the electrolyte, reduce electrolyte consumption, and extend the cycle life of lithium metal batteries.

[0240] 2. Coulomb efficiency test

[0241] Coulombic efficiency is defined as the percentage of lithium metal stripping capacity to deposition capacity per charge-discharge cycle, and is one of the important indicators for evaluating the reversibility of the lithium metal deposition / stripping process. This application's embodiments demonstrate coulombic efficiency testing by assembling half-cells.

[0242] The test method is as follows: set the initial current density to 1 mA / cm². 2 Under these conditions, tests were conducted for 5 weeks (weeks); 1 mA / cm 2 After testing, the current density was increased to 2 mA / cm². 2 The test was continued for 5 weeks; afterwards, the current density was increased to 3 mA / cm². 2 And it was tested for 5 weeks as well. At 3mA / cm 2 After the test is completed, the current density is adjusted back to 2 mA / cm². 2 The capacity is 1mAh / cm 2 Conduct the test.

[0243] Figure 12 The coulombic efficiency test graphs for the half-cells of Example 1 and Comparative Example 2 are shown below. Figure 12 As shown in (a), under gradient-increasing current density and capacity, the UMTGA electrode of Example 1 exhibits a smooth curve and maintains high coulombic efficiency, while the copper foil electrode of Comparative Example 2 shows significant fluctuations. In the subsequent 2mA / cm... 2 Under the conditions of current density and controlling the weekly deposition and stripping time to be half an hour ( Figure 12 In Example (b), the UMTGA electrode of Example 1 had an average coulombic efficiency of 94.9% during lithium metal deposition / stripping cycles of 16 to 120 weeks. However, the copper foil electrode of Comparative Example 2 showed a decrease in coulombic efficiency after only 16 weeks, and a sharp fluctuation in coulombic efficiency occurred after 45 weeks. This was due to the interface instability caused by dendrite growth under high current density.

[0244] The test results of the voltage-time curves of the half-cells of Example 1 and Comparative Example 3 at different current densities are as follows: Figure 12 As shown in (c), the half-cell of Example 1 operates at 1 mA / cm². 2 2mA / cm 2 4mA / cm 2 6mA / cm 2 8mA / cm 2 The half-cell of Example 1 exhibited hysteresis voltages of 42mV, 52mV, 78mV, 79mV, and 87mV at current densities of [specific values ​​missing], while the half-cell of Comparative Example 2 showed hysteresis voltages of 59mV, 73mV, 112mV, 95mV, and 109mV at the corresponding current densities. Comparing the voltage-time curves, the half-cell of Example 1 maintained a low overpotential and stable cycling under gradually increasing current densities, indicating that the battery possesses good lithium metal deposition / stripping kinetics and low interfacial impedance. However, the half-cell of Comparative Example 2 exhibited a relatively large hysteresis voltage, and this hysteresis voltage increased further when the current density increased to 6mA / cm². 2Afterwards, the voltage curve became unstable and showed large fluctuations, indicating that the battery became unstable under high current.

[0245] like Figure 13 SEM characterization of the lithium metal deposition morphology of the half-cell after cycling showed that the lithium metal deposited on the UMTGA electrode in Example 1 exhibited a uniform and dense morphology. Figure 13 In (a)-(c)), however, the lithium metal on the copper foil in Comparative Example 2 exhibits many cracks, and a loose and porous structure can be seen when magnified. Figure 13 (d)-(f)). This indicates that UMTGA can effectively suppress lithium dendrite growth and achieve uniform electrochemical deposition of lithium, thereby extending the cycle life of the battery.

[0246] 3. Long-cycle coulombic efficiency test

[0247] Test conditions: The test current density is set to 1 mA / cm². 2 The charge / discharge capacity is set to 1 mAh / cm³. 2 Perform long-cycle testing.

[0248] like Figure 14 As shown in (a), the coulombic efficiency of the Cu electrode in Comparative Example 2 fluctuated during the test, indicating instability. After 105 cycles of lithium metal deposition / stripping, the coulombic efficiency began to decline significantly. This was due to the aggravation of side reactions caused by lithium dendrite growth. Compared to the Cu electrode in Comparative Example 2, the GA electrode in Comparative Example 1 showed improvement, with a higher average coulombic efficiency during 117 cycles of lithium metal deposition / stripping. However, after 117 cycles, fluctuations in coulombic efficiency and overcharging occurred, indicating that the side reactions intensified, the electrolyte was depleted, and stable cycling could not continue. The half-cell of Example 1 was tested at a current density of 1 mA / cm². 2 The charge / discharge capacity is 1mAh / cm³. 2 Under the test conditions, the average coulombic efficiency reached 98.0% during 300 cycles of lithium metal deposition / stripping. These test results demonstrate that the UMTGA of Example 1 effectively reduces local current density and suppresses dendrite growth, thereby improving electrode reversibility.

[0249] Figure 14 Figure (b) shows the nucleation overpotential curve for the first cycle. As shown in the figure, the nucleation overpotentials of the Cu electrode in Comparative Example 2, the GA electrode in Comparative Example 1, and the UMTGA electrode in Example 1 are 56 mV, 38 mV, and 24 mV, respectively. This indicates that the introduced ultra-dispersed mesoporous TiO2 can enhance the lithiophilicity of the substrate, reduce the nucleation overpotential of lithium metal, and guide the uniform deposition of lithium. UMTGA undergoes a lithiation reaction to form Li before lithium metal deposition. 0.5 TiO2 also helps to improve lithophileness.

[0250] Figure 14 (c) shows the charge-discharge curves of the half-cell of Example 1 at different cycle numbers. Except for the first cycle, the charge-discharge curves of the half-cell of Example 1 show a high degree of consistency, indicating that lithium metal can be stably stripped / deposited and maintain a high coulombic efficiency.

[0251] Figure 15 (a) in the figure represents the UMTGA battery at 1 mA / cm 2 Nyquist plot after cycling at current density; Figure 15 (b) shows the fitted curve of the lithium-ion diffusion coefficient. Impedance testing analysis using Zview software revealed that the UMTGA battery has an impedance value of 12.2 Ω, significantly lower than the 44.6 Ω of Comparative Example 2. Furthermore, the fitting of the lithium-ion diffusion coefficient at low frequencies also indicates that the Li-UMTGA battery has an impedance of 9.54 × 10⁻⁶. –9 cm 2 The diffusion coefficient is 3.95 × 10⁻⁶ / s, compared to 3.95 × 10⁻⁶ in Comparative Example 2. –10 cm 2 The increase in density by an order of magnitude indicates that UMTGA can accelerate lithium-ion diffusion, guide uniform lithium metal deposition, suppress side reactions, and stabilize the battery interface.

[0252] LFP Full Battery Performance Testing

[0253] like Figure 16 As shown in (a), the LFP full cell of Example 1 (hereinafter referred to as LFP / UMTGA–Li cell) released specific capacities of 133 mAh / g, 127 mAh / g, 121 mAh / g, 109 mAh / g, 103 mAh / g, 96 mAh / g, 90 mAh / g, and 68 mAh / g at test rates of 0.5C, 1C, 2C, 4C, 6C, 8C, 10C, and 15C (1C = 170 mA / g), respectively. The LFP full cell of Comparative Example 2 (hereinafter referred to as LFP / Cu–Li cell) released specific capacities of 127 mAh / g, 121 mAh / g, 110 mAh / g, 96 mAh / g, 90 mAh / g, 83 mAh / g, 77 mAh / g, and 64 mAh / g at the corresponding rates, which are all lower than the values ​​of the LFP / UMTGA–Li cell. In subsequent high-rate cycling at 5C, the LFP / UMTGA–Li battery still retained a specific capacity of 80 mAh / g after 1120 cycles, achieving a capacity retention of 87.8%, with an average coulombic efficiency of 99.8% over the 1120-cycle charge-discharge period. The LFP / Cu–Li battery, however, began to show capacity decay only after 580 cycles, dropping to 17 mAh / g by 680 cycles, at which point the coulombic efficiency began to fluctuate dramatically. The charge-discharge curves show (…). Figure 16In (b)-(c)), at different test rates, the LFP / UMTGA–Li cell has a lower voltage hysteresis than the LFP / Cu–Li cell.

[0254] Figure 17 This is a SEM image of the negative electrode morphology after a full cycle of an LFP cell. Figure 17 (a)-(c) are SEM images of the negative electrode (hereinafter referred to as UMTGA-Li electrode) of Example 1 at different magnifications. No dendrites are formed on the surface of the UMTGA-Li electrode, and the lithium metal exhibits a flat and dense morphology. Figure 17 Images (d)-(f) in the diagram are SEM images of the negative electrode (hereinafter referred to as the Cu-Li electrode) of Comparative Example 2 at different magnifications. The Cu-Li electrode surface shows many obvious cracks. After SEM magnification, it was found that the lithium metal in local areas exhibits a loose, porous, granular structure with very incomplete filling. This indicates that UMTGA can guide the uniform deposition of lithium metal, suppress dendrite growth, and stabilize the electrochemical cycling of the negative electrode.

[0255] NCM Full Battery Performance Testing

[0256] like Figure 18 As shown: The NCM full cell of Example 1 (hereinafter referred to as NCM811 / UMTGA–Li cell) released 147mAh / g, 143mAh / g, 132mAh / g, 118mAh / g, 107mAh / g, 97mAh / g, 88mAh / g, 81mAh / g, 73mAh / g, and 66mAh / g at rates of 0.5C, 1C, 2C, 4C, 6C, 8C, 10C, 12C, 14C, and 16C (1C = 170mAh / g), respectively. The NCM full cell (hereinafter referred to as NCM811 / Cu-Li battery) in Comparative Example 2 had capacities of 150mAh / g, 142mAh / g, 129mAh / g, 112mAh / g, 101mAh / g, 91mAh / g, 81mAh / g, 71mAh / g, 62mAh / g, and 54mAh / g at the corresponding rates. Except for a slightly higher capacity at 0.5C rate, the capacity was lower than that of the NCM811 / UMTGA-Li battery at all other rates. In subsequent 3C rate cycling, the NCM811 / UMTGA-Li battery released 121mAh / g of capacity in the first week and still released 84mAh / g of capacity after 900 cycles, with a capacity retention rate as high as 69.4%. In contrast, the NCM811 / Cu-Li battery began to show a significant capacity decay at 768 weeks, and the capacity was only 10mAh / g at 800 weeks.

[0257] The negative electrode morphology of the cycled NCM811 / UMTGA–Li and NCM811 / Cu–Li batteries was characterized by SEM, such as... Figure 19 As shown, after cycling, the UMTGA–Li electrode surface exhibits a smooth and flat lithium metal deposition morphology, indicating that the UMTGA electrode can effectively suppress dendrite growth, which is beneficial for high-rate long-cycle operation of the full cell. In contrast, the Cu–Li electrode surface has a large number of cracks and dendrites, which leads to rapid consumption of active materials, causing fluctuations in the battery's coulombic efficiency and shortening the cycle life of the full cell.

[0258] Table 1 shows the performance data of the composite anode materials of each embodiment and Comparative Example 1, as well as their LFP full cell performance data.

[0259] Table 1

[0260]

[0261] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A lithium metal battery cell, characterized in that, The device includes a negative electrode sheet, the negative electrode sheet comprising a composite negative electrode material, the composite negative electrode material comprising a graphene composite material; the graphene composite material comprising graphene and metal oxide particles loaded on the surface of the graphene; the metal oxide particles comprising at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

2. The lithium metal battery cell according to claim 1, characterized in that, The number density deviation of the metal oxide particles over at least 90% of the area of ​​the graphene does not exceed ±15%; and / or the average distance between any two adjacent metal oxide particles does not exceed 20 nm.

3. The lithium metal battery cell according to claim 1 or 2, characterized in that, The composite negative electrode material satisfies at least one of the following conditions: (1) The mass of the metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material; (2) The specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g; (3) The particle size of the graphene composite material is 5μm to 30μm; (4) The particle size of the metal oxide particles is 5nm to 30nm.

4. The lithium metal battery cell according to any one of claims 1 to 3, characterized in that, The metal oxide particles are TiO2 particles, and the TiO2 particles have mesopores.

5. The lithium metal battery cell according to claim 4, characterized in that, The mesopores of the TiO2 particles have a pore size of 3 nm to 5 nm.

6. The lithium metal battery cell according to any one of claims 1 to 5, characterized in that, The composite anode material also includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

7. The lithium metal battery cell according to claim 6, characterized in that, The lithium metal accounts for 25% to 80% of the total mass of the composite anode material.

8. A composite negative electrode material, characterized in that, The invention includes a graphene composite material comprising graphene and metal oxide particles supported on the surface of the graphene, wherein the metal oxide particles are made of at least one of TiO2, ZnO, CuO, ZrO2, NiO, CoO, and Al2O3.

9. The composite negative electrode material according to claim 8, characterized in that, The number density deviation of the metal oxide particles over at least 90% of the area of ​​the graphene does not exceed ±15%; and / or the average distance between any two adjacent metal oxide particles does not exceed 20 nm.

10. The composite negative electrode material according to claim 8 or 9, characterized in that, The composite negative electrode material satisfies at least one of the following conditions: (1) The mass of the metal oxide particles accounts for 45% to 70% of the total mass of the graphene composite material; (2) The specific surface area of ​​the graphene composite material is 160 m². 2 / g~280m 2 / g; (3) The particle size of the graphene composite material is 5μm to 30μm; (4) The particle size of the metal oxide particles is 5nm to 30nm.

11. The composite negative electrode material according to any one of claims 8 to 10, characterized in that, The metal oxide particles are TiO2 particles, and the TiO2 particles have mesopores.

12. The composite negative electrode material according to claim 11, characterized in that, The mesopores of the TiO2 particles have a pore size of 3 nm to 5 nm.

13. The composite negative electrode material according to any one of claims 8 to 12, characterized in that, The composite anode material also includes lithium metal, which is loaded on the surface and / or in the pores of the graphene composite material.

14. The composite anode material according to claim 13, wherein the lithium metal accounts for 25% to 80% of the total mass of the composite anode material.

15. A method for preparing a composite negative electrode material, characterized in that, Includes the following steps: A metal salt, reducing sugar, graphene oxide, and a solvent are mixed to obtain a mixed solution; the metal salt includes at least one selected from titanium salt, zinc salt, copper salt, zirconium salt, nickel salt, cobalt salt, and aluminum salt. The mixed solution was subjected to a hydrothermal reaction to obtain a graphene composite material.

16. The method for preparing the composite negative electrode material according to claim 15, characterized in that, The temperature of the hydrothermal reaction is 160℃~200℃; and / or the time of the hydrothermal reaction is 10h~14h.

17. The method for preparing the composite negative electrode material according to claim 15 or 16, characterized in that, The concentration of graphene oxide in the mixed solution is 1.5 mg / mL to 2.5 mg / mL; And / or, the mass ratio of the graphene oxide to the metal salt is 1:(2.5-5); And / or, the mass ratio of the reducing sugar to the metal salt is 1:(10-20).

18. The method for preparing the composite negative electrode material according to any one of claims 15 to 17, characterized in that, Lithium metal is deposited on the surface and / or in the pores of the graphene composite material using electrochemical deposition or self-discharge.

19. The method for preparing the composite negative electrode material according to claim 18, characterized in that, The graphene composite material was combined with lithium metal to form a coin cell. The coin cell was then subjected to electrochemical discharge deposition on a charge-discharge apparatus at a current density of 0.5 mA / cm². 2 ~5mA / cm 2 The deposition amount was 0.5 mAh / cm³. 2 ~14mAh / cm 2 After deposition, the coin cell is disassembled to obtain the composite anode material; or, An electrolyte is dropped onto the graphene composite material, and lithium metal is bonded to the graphene composite material to form a primary battery. After 1 to 5 hours of self-discharge, the composite negative electrode material is obtained.

20. A battery device, characterized in that, Includes the lithium metal battery cell according to any one of claims 1 to 7.

21. An electrical appliance, characterized in that, Includes a lithium metal battery cell according to any one of claims 1 to 7 or a battery device according to claim 20, wherein the lithium metal battery cell or the battery device is used to store or provide electrical energy.

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