Graphite-based composite negative electrode material and preparation method thereof

Abstract

The application discloses a graphite-based composite negative electrode material and a preparation method thereof, and comprises the following steps: a graphite core; a three-dimensional curved conductive framework which is inserted between layers of the graphite core; and a multi-metal compound nanocage which is uniformly loaded on the surface of the graphite core after being coated by a graphene-based coating layer. By constructing a three-level synergistic structure of graphite-three-dimensional curved conductive framework-multi-metal compound nanocage, gradient embedding and storage of lithium / sodium ions are realized, so that the negative electrode material has high specific capacity, excellent rate performance and super-long cycle life.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a graphite-based composite anode material and its preparation method. Background Technology

[0002] Graphite has become the primary anode material for commercial lithium-ion batteries due to its low cost, stable structure, and good conductivity. However, the narrow interlayer spacing of graphite (approximately 0.335 nm) restricts the rapid migration of lithium ions, resulting in poor rate performance and inability to meet fast charging requirements. Furthermore, its theoretical capacity is relatively low (approximately 372 mAh·g). -1 This limits further improvements in battery energy density.

[0003] To overcome these drawbacks, researchers have attempted to combine graphite with other high-capacity materials. Bending graphene nanoparticles (such as Cl-cHBC) possess large interlayer spacing (approximately 1.34 nm) and pseudocapacitive behavior, enabling rapid lithium-ion storage, but they exhibit poor intrinsic conductivity and low tap density. Bimetallic sulfides (such as NiS2-Co3S4), based on conversion reactions, can provide capacities far exceeding the theoretical capacity of graphite, but they suffer from significant volume expansion during charge and discharge, leading to electrode structure pulverization and rapid capacity decay.

[0004] Existing composite solutions are mostly limited to binary systems (such as graphite / sulfide, graphite / organic materials), making it difficult to simultaneously address the issues of fast ion transport, high capacity, and volume stability while maintaining high conductivity. For example, directly mixing sulfides with graphite often results in unsatisfactory cycle performance due to interfacial instability and volume effects. Therefore, developing a multifunctional composite anode material that integrates the advantages of all parties and features an innovative structural design is of great significance. Summary of the Invention

[0005] In view of this, the present invention provides a graphite-based composite anode material and its preparation method. By constructing a three-level structure of graphite-three-dimensional bent conductive framework-multi-metal compound nanocage, the gradient embedding and storage of lithium / sodium ions are realized, enabling the anode material to have high specific capacity, excellent rate performance and ultra-long cycle life.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention discloses a graphite-based composite anode material, comprising: Graphite core; A three-dimensional curved conductive framework is inserted into the interlayer of the graphite core; A multi-metallic compound nanocage, after being coated with a graphene-based coating layer, is uniformly loaded onto the surface of the graphite core.

[0007] The graphite core serves as the primary conductive framework and structural support, ensuring the macroscopic conductivity and mechanical strength of the electrode. A three-dimensional bent conductive framework (Cl-cHBC) exists between the graphite layers through intercalation, effectively expanding the interlayer spacing and forming fast ion channels preferentially used for lithium intercalation over graphite, while mitigating the risk of lithium plating at low potentials. The open nanocage structure of the polymetallic compound nanocage (NiS2-Co3S4@rGO) provides abundant reactive sites. The rGO coating enhances the conductivity of the sulfide while effectively suppressing its volume expansion during charge and discharge. This component, as a high-capacity unit, provides the main capacity through conversion reactions.

[0008] The graphite-Cl-cHBC-sulfide tertiary structure constructed in this invention guides Li+ to achieve gradient embedding. Specifically, Li+ preferentially embeds into the large interlayer spacing region of Cl-cHBC (where the embedding barrier is low), then enters the graphite interlayer, and finally undergoes a transformation reaction at the sulfide / electrolyte interface. This mechanism can disperse ion flow and reduce local stress, thereby avoiding failure problems caused by overloading of a single component.

[0009] In this structure, graphite provides a stable, continuous conductive network; Cl-cHBC not only provides fast ion channels, but its high lithium intercalation potential also helps reduce the risk of lithium plating on the graphite surface; sulfide nanocages contribute high capacity and maintain structural integrity under the constraint of rGO. The synergistic effect of these three components significantly improves the overall performance of the material.

[0010] A further embodiment: the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is (35-60):(17-30):(30-40), which ensures the optimal balance of conductive network, ion channels, and active capacity.

[0011] A further option: the graphite core is a mesophase carbon microsphere.

[0012] A further embodiment: the three-dimensional curved conductive framework is a chlorinated twisted hexabenzo[a]cobalamin.

[0013] A further option: the multimetallic compound nanocage is a bimetallic sulfide.

[0014] A further option: the bimetallic sulfide is NiS2-Co3S4.

[0015] A further approach: After the insertion of the bent graphene nanoparticles, the interlayer spacing of the graphite core is 0.5 nm to 1.0 nm. Interlayer spacing is a key structural parameter determining material properties. If the interlayer spacing is less than 0.5 nm, the expansion is insufficient and will still limit the rapid transport of ions, resulting in limited improvement in kinetic performance; if the interlayer spacing is greater than 1.0 nm, the van der Waals forces between the graphite layers will be excessively weakened, causing irreversible structural collapse during cycling, and the tap density will also decrease significantly.

[0016] Secondly, this invention discloses a method for preparing the graphite-based composite anode material as described above, comprising the following steps: S1. The graphite core and the three-dimensional curved conductive framework are mixed according to the mass ratio, and the mixture is ball-milled and heat-treated to obtain the intercalation composite. S2. Preparation of multi-metal compound nanocages coated with graphene-based coating layers; S3. The intercalation composite obtained in step S1 is mixed with the multi-metal compound nanocage obtained in step S2, and then dispersed, dried and heat-treated to obtain the composite anode material.

[0017] A further option: In step S1, the heat treatment temperature is 300-350℃, the time is 30-60 minutes, and the heat treatment is carried out in an inert atmosphere.

[0018] Further solution: Step S2 specifically involves: The nickel-cobalt Prussian blue analog precursor was etched to obtain a nanocage structure; Carbon material is coated onto the surface of the nanocage structure and combined with graphene oxide. After heat treatment, a precursor composite is obtained. The precursor complex was subjected to a sulfurization reaction with a sulfur source to obtain a multi-metal compound nanocage coated with the graphene-based coating layer.

[0019] Thirdly, the present invention discloses an electrode sheet, wherein the active material layer of the electrode sheet comprises the graphite-based composite negative electrode material as described above.

[0020] Fourthly, the present invention discloses a lithium-ion battery or a sodium-ion battery, which includes the electrode sheet as described above.

[0021] The present invention also provides a method for preparing the composite anode material, comprising the following steps: Step 1: Preparation of graphite composites with bent graphene nanoparticles (G-CHBC) Graphite (such as MCMB) and bent graphene nanoparticles (such as Cl-cHBC) are placed in a ball mill jar at a mass ratio, and an organic solvent (such as N-methylpyrrolidone, NMP) is added. The mixture is ball-milled for 2-6 hours to ensure that Cl-cHBC is fully dispersed and embedded between the graphite layers. After drying the mixture, it is heat-treated at 300-350°C for 30-60 minutes in an inert atmosphere (such as argon) to improve the crystallinity and stability of the composite.

[0022] Step 2: Preparation of reduced graphene oxide-coated bimetallic sulfide nanocages (NiS2-Co3S4@rGO) S2.1: Nickel-cobalt Prussian blue analog cubic precursors were synthesized by co-precipitation method.

[0023] S2.2: Under mild conditions, the precursor is selectively etched with ammonia (e.g., for 15 minutes) to remove the cubic vertices and form an open nanocage structure.

[0024] S2.3: Ni-CoPBA@PDA is obtained by coating a polydopamine layer (i.e., carbon material) onto the surface of a nanocage through in-situ polymerization.

[0025] S2.4: Mix Ni-CoPBA@PDA with graphene oxide solution at a mass ratio of (3-5):1, stir, freeze dry, and anneal at 600-700℃ under an inert atmosphere to obtain Ni-Co PBA@rGO.

[0026] S2.5: Ni-Co PBA@rGO and excess sulfur powder were placed upstream and downstream of a tube furnace, respectively, and subjected to a sulfidation reaction at 400-500℃ for 1-3 hours under an inert atmosphere to finally obtain NiS2-Co3S4@rGO nanocages.

[0027] Step 3: Constructing a ternary composite anode material The G-CHBC obtained in step one and the NiS2-Co3S4@rGO nanocages obtained in step two were mixed in a solvent at a mass ratio of (60-70):(30-40), and then uniformly dispersed by ultrasonication or ball milling. The mixture was then dried and subjected to a short-term heat treatment (e.g., 30 minutes) at 250-300℃ in an inert atmosphere to enhance interfacial bonding, yielding the final ternary composite anode material.

[0028] Compared with the prior art, the beneficial effects of the present invention are: The composite anode material provided by this invention achieves the following through the construction of a multi-layer structure: a graphite core, a three-dimensional curved conductive framework, and a multi-metal compound nanocage. This results in: 1) the three-dimensional curved conductive framework being inserted into the graphite interlayers to expand the interlayer spacing, forming a fast ion transport channel that guides the preferential embedding of lithium / sodium ions and disperses the ion flow, avoiding the risk of lithium plating due to low graphite potential; 2) the multi-metal compound nanocage serving as a high-capacity active unit, providing high specific capacity through conversion reactions, with its graphene-based coating effectively suppressing volume expansion during charging and discharging; and 3) the graphite core acting as a stable three-dimensional conductive network and structural support. The resulting composite anode material exhibits high capacity, fast charging capability, and long-cycle stability, significantly outperforming existing single or binary composite anode materials.

[0029] Furthermore, the ball milling and heat treatment processes used in this invention are relatively simple, have good compatibility with existing electrode manufacturing processes, and are conducive to large-scale industrial production. Detailed Implementation

[0030] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0033] The reagents used in the following examples and comparative examples, along with their respective manufacturers and suppliers, are as follows: The manufacturer of the mesophase carbon microspheres (MCMB) is BTR New Materials Group Co., Ltd., and the model number is MCMB-10. Chlorinated twisted hexabenzo[cHBC]: synthesized according to the method described in the literature [Adv. Funct. Mater. 2025, 15,2408762], with a purity ≥98%, hexachloro-substituted, and a molecular twist angle ≈30°; The manufacturer of graphene oxide (GO) is Nanjing Xianfeng Nanomaterials Technology Co., Ltd., and the model number is XF002. The sulfur powder is manufactured by Sinopharm Chemical Reagent Co., Ltd., and its model number is 10010318. The manufacturer of dopamine is Sigma-Aldrich, and the model number is H8502. The reagents described above are only for illustrating the source and composition of the reagents used in the experiments of this invention, so as to provide full disclosure, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0034] Example 1 Step 1: Weigh 4.0 g of MCMB graphite and 2.0 g of Cl-CHBC, add 100 mL of NMP solvent, and ball mill in a planetary ball mill at 400 rpm for 4 hours. Dry the ball-milled slurry at 80 °C for 12 hours, and then anneal the resulting powder at 330 °C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated is obtained, denoted as G-CHBC.

[0035] Step 2: A cubic precursor of nickel-cobalt Prussian blue analogue was synthesized using a co-precipitation method (preparation method as described in patent CN117247029A, hereinafter the same), denoted as Ni-Co PBA. The obtained Ni-Co PBA was etched with ammonia for 15 minutes to obtain nanocages with an open structure. Then, polydopamine was coated on the surface of the etched nanocages to obtain Ni-Co PBA@PDA. 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide were dispersed in water, stirred for 2 hours, and then freeze-dried. The dried product was then annealed at 700°C for 2 hours under an argon atmosphere to obtain Ni-Co PBA@rGO. Finally, 0.5 g of Ni-CoPBA@rGO and 1.0 g of sulfur powder were placed upstream and downstream of a tube furnace, respectively, and sulfurized at 500 °C for 2 hours under argon protection. After the reaction was completed, the mixture was naturally cooled to obtain a graphene-based coating layer-coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0036] Step 3: Take 3.0 g of G-CHBC obtained in Step 1 and 2.0 g of NiS2-Co3S4@rGO obtained in Step 2, disperse them in ethanol, and sonicate for 2 hours to ensure uniform mixing. After drying the mixture, the resulting powder is heat-treated at 280℃ for 30 minutes under an argon atmosphere, and then naturally cooled to obtain a graphite-based composite anode material. In the composite material obtained in this example, the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is approximately 40:20:40.

[0037] Example 2 Step 1: Weigh 4.5 g of MCMB graphite and 1.5 g of Cl-CHBC, add 100 mL of NMP solvent, and ball mill in a planetary ball mill at 400 rpm for 4 hours. Dry the ball-milled slurry at 80 °C for 12 hours, and then anneal the resulting powder at 330 °C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated is obtained, denoted as G-CHBC.

[0038] Step 2: A cubic precursor of nickel-cobalt Prussian blue analogue, denoted as Ni-CoPBA, was synthesized using a co-precipitation method. The obtained Ni-Co PBA was etched with ammonia for 15 minutes to obtain nanocages with an open structure. Then, polydopamine was coated onto the surface of the etched nanocages to obtain Ni-Co PBA@PDA. 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide were dispersed in water, stirred for 2 hours, and then freeze-dried. The dried product was then annealed at 700°C for 2 hours under an argon atmosphere to obtain Ni-Co PBA@rGO. Finally, 0.5 g of Ni-Co PBA@rGO and 1.0 g of sulfur powder were placed upstream and downstream of a tube furnace, respectively, and sulfurized at 500°C for 2 hours under argon protection. After the reaction, the mixture was allowed to cool naturally to obtain a graphene-coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0039] Step 3: Take 3.5 g of G-CHBC obtained in Step 1 and 1.5 g of NiS2-Co3S4@rGO obtained in Step 2, disperse them in ethanol, and sonicate for 2 hours to ensure uniform mixing. After drying the mixture, the resulting powder is heat-treated at 280℃ for 30 minutes under an argon atmosphere, and then naturally cooled to obtain a graphite-based composite anode material. In the composite material obtained in this embodiment, the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is approximately 52.5:17.5:30.

[0040] Example 3 Step 1: Weigh 3.5 g of MCMB graphite and 2.5 g of Cl-CHBC, add 100 mL of NMP solvent, and ball mill in a planetary ball mill at 400 rpm for 4 hours. Dry the ball-milled slurry at 80 °C for 12 hours, and then anneal the resulting powder at 330 °C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated is obtained, denoted as G-CHBC.

[0041] Step 2: A cubic precursor of nickel-cobalt Prussian blue analogue, denoted as Ni-CoPBA, was synthesized using a co-precipitation method. The obtained Ni-Co PBA was etched with ammonia for 15 minutes to obtain nanocages with an open structure. Then, polydopamine was coated onto the surface of the etched nanocages to obtain Ni-Co PBA@PDA. 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide were dispersed in water, stirred for 2 hours, and then freeze-dried. The dried product was then annealed at 700°C for 2 hours under an argon atmosphere to obtain Ni-Co PBA@rGO. Finally, 0.5 g of Ni-Co PBA@rGO and 1.0 g of sulfur powder were placed upstream and downstream of a tube furnace, respectively, and sulfurized at 500°C for 2 hours under argon protection. After the reaction, the mixture was allowed to cool naturally to obtain a graphene-coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0042] Step 3: Take 2.5 g of G-CHBC obtained in Step 1 and 2.5 g of NiS2-Co3S4@rGO obtained in Step 2, disperse them in ethanol, and sonicate for 2 hours to ensure uniform mixing. After drying the mixture, the resulting powder is heat-treated at 280℃ for 30 minutes under an argon atmosphere, and then naturally cooled to obtain a graphite-based composite anode material. In the composite material obtained in this embodiment, the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is approximately 35:25:40.

[0043] Example 4 Step 1: Weigh 4 grams of MCMB graphite and 2 grams of Cl-CHBC, add 100 ml of NMP solvent, and ball mill in a planetary ball mill at 400 rpm for 4 hours. Dry the ball-milled slurry at 80°C for 12 hours, and then anneal the resulting powder at 330°C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated is obtained, denoted as G-CHBC.

[0044] Step 2: A cubic precursor of nickel-cobalt Prussian blue analogue, denoted as Ni-CoPBA, was synthesized using a co-precipitation method. The obtained Ni-Co PBA was etched with ammonia for 10 minutes to obtain nanocages with an open structure. Then, polydopamine was coated onto the surface of the etched nanocages to obtain Ni-Co PBA@PDA. 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide were dispersed in water, stirred for 2 hours, and then freeze-dried. The dried product was then annealed at 700°C for 2 hours under an argon atmosphere to obtain Ni-Co PBA@rGO. Finally, 0.5 g of Ni-Co PBA@rGO and 1.0 g of sulfur powder were placed upstream and downstream of a tube furnace, respectively, and sulfurized at 500°C for 2 hours under argon protection. After the reaction, the mixture was allowed to cool naturally to obtain a graphene-based coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0045] Step 3: Take 3 grams of G-CHBC obtained in Step 1 and 2 grams of NiS2-Co3S4@rGO obtained in Step 2, disperse them in ethanol, and sonicate for 2 hours to ensure uniform mixing. After drying the mixture, the resulting powder is heat-treated at 280°C for 30 minutes under an argon atmosphere, and then naturally cooled to obtain a graphite-based composite anode material. In the composite material obtained in this embodiment, the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is approximately 40:20:40.

[0046] Example 5 Step 1: Weigh 4.0 g of MCMB graphite and 2.0 g of Cl-CHBC, add 100 mL of NMP solvent, and ball mill in a planetary ball mill at 400 rpm for 4 hours. Dry the ball-milled slurry at 80 °C for 12 hours, and then anneal the resulting powder at 330 °C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated is obtained, denoted as G-CHBC.

[0047] Step 2: Synthesize a cubic precursor of a nickel-cobalt Prussian blue analogue, denoted as Ni-Co PBA. Etch the obtained Ni-Co PBA with ammonia for 15 minutes to obtain nanocages with an open structure. Then, coat the surface of the etched nanocages with polydopamine to obtain Ni-Co PBA@PDA. Disperse 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide in water, stir for 2 hours, and then freeze-dry. Anneal the dried product at 700 °C for 2 hours under an argon atmosphere to obtain Ni-CoPBA@rGO. Finally, place 0.5 g of Ni-Co PBA@rGO and 1.0 g of sulfur powder upstream and downstream of a tube furnace, respectively, and sulfurize at 500 °C for 2 hours under argon protection. After the reaction, allow it to cool naturally to obtain a graphene-based coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0048] Step 3: Take 3.0 g of G-CHBC obtained in Step 1 and 2.0 g of NiS2-Co3S4@rGO obtained in Step 2, disperse them in ethanol, and sonicate for 2 hours to ensure uniform mixing. After drying the mixture, the resulting powder is heat-treated at 280℃ for 30 minutes under an argon atmosphere, and then naturally cooled to obtain a graphite-based composite anode material. In the composite material obtained in this example, the mass ratio of the graphite core, the three-dimensional curved conductive framework, and the multi-metal compound nanocage is approximately 40:20:40.

[0049] Comparative Example 1 Mesophase carbon microspheres of graphite were used as the active material and directly applied to the preparation of electrode sheets without any composite treatment.

[0050] Comparative Example 2 Step 1: Take 4.0 g of mesophase carbon microspheres graphite and 2.0 g of chlorinated twisted hexabenzo[a]col], add 100 mL of N-methylpyrrolidone solvent, and place in a planetary ball mill and ball mill at 400 rpm for 4 hours.

[0051] Step 2: The ball-milled slurry was dried at 80°C for 12 hours. The resulting powder was then placed in a tube furnace and annealed at 330°C for 50 minutes under an argon atmosphere. After natural cooling, a graphite composite with a three-dimensional curved conductive framework intercalated was obtained, denoted as G-CHBC.

[0052] Comparative Example 3 A cubic precursor of a nickel-cobalt Prussian blue analogue, denoted as Ni-Co PBA, was synthesized using a co-precipitation method. The obtained Ni-Co PBA was etched with ammonia for 15 minutes to obtain nanocages with an open structure. Then, polydopamine was coated onto the surface of the etched nanocages to obtain Ni-Co PBA@PDA. 1.0 g of Ni-Co PBA@PDA and 0.25 g of graphene oxide were dispersed in water, stirred for 2 hours, and then freeze-dried. The dried product was then annealed at 700 °C for 2 hours under an argon atmosphere to obtain Ni-Co PBA@rGO. Finally, 0.5 g of Ni-Co PBA@rGO and 1.0 g of sulfur powder were placed upstream and downstream of a tube furnace, respectively, and sulfurized at 500 °C for 2 hours under argon protection. After the reaction, the mixture was allowed to cool naturally to obtain a graphene-coated multimetallic compound nanocage, denoted as NiS2-Co3S4@rGO.

[0053] Test case I. Electrode preparation The materials prepared in Examples 1-5 and Comparative Examples 1-3 were used as active materials and mixed with conductive agent acetylene black and binder PVDF at a mass ratio of 8:1:1. 1.2-1.5 mL of N-methylpyrrolidone solvent was added per 1.0 g of total solid powder, and the mixture was ground uniformly in a mortar to form a slurry. The slurry was coated onto copper foil and dried in a vacuum drying oven at 80°C for 12 hours, then cut into circular electrode sheets with a diameter of 12 mm. The active material loading on each electrode sheet was approximately 1.5-2.0 mg·cm³. -2 .

[0054] II. Button Battery Assembly Using the electrode sheet prepared above as the working electrode and the lithium metal sheet as the counter and reference electrodes, CR2032 coin cells were assembled in an argon-filled glove box (with water and oxygen content both below 0.1 ppm). The separator was a Celgard 2400 polypropylene microporous membrane, and the electrolyte was a 1M LiPF6 solution dissolved in a ethylene carbonate / diethyl carbonate (volume ratio 1:1) mixed solvent, with 5% fluoroethylene carbonate added as a film-forming additive. Approximately 80 μL of electrolyte was added to each cell.

[0055] III. Electrochemical Performance Testing The assembled coin cells were left to stand at room temperature for 12 hours to allow the electrolyte to fully wet the electrode materials. Constant current charge-discharge tests were then performed using a Blue Battery testing system, with a voltage window of 0.01-3.0 V (vs. Li / Li). + The test items include: First Coulomb efficiency and 0.1 A·g -1 Reversible capacity test: at 0.1 A·g-1 The battery was charged and discharged at a current density of [value missing], and the specific capacity of the first charge and the specific capacity of the first discharge were recorded. The initial coulombic efficiency (first discharge specific capacity / first charge specific capacity × 100%) was calculated. The discharge specific capacity of the second cycle was taken as 0.1 A·g [value missing]. -1 The reversible capacity below.

[0056] Cyclic performance test: at 1 A·g -1 The battery was subjected to constant current charge-discharge cycle test at a current density of 100 times, and the discharge specific capacity of the 100th cycle was recorded.

[0057] Rate performance testing: Tests were conducted at different current densities (0.1 A·g⁻¹). -1 0.2 A·g -1 0.5 A·g -1 1A·g -1 2 A·g -1 5 A·g -1 The battery was subjected to charge-discharge tests, with 5 cycles at each current density. The discharge specific capacity at each current density was recorded, including 5 A·g. -1 The discharge specific capacity at low rates is used as an evaluation index for high-rate performance.

[0058] The test results of each embodiment and comparative example are shown in Table 1 below.

[0059] Table 1

[0060] As shown in Table 1, the ternary composite anode materials prepared in Examples 1-5 of this invention exhibit significantly better capacity, rate performance, and cycle stability than the single or binary materials in the comparative examples. Specifically, compared to Comparative Example 1 (pure graphite), the specific capacity of the embodiments of this invention is increased by more than 4 times, and the high-rate performance is significantly improved from below 50 mAh·g. -1 Increased to 600 mAh·g -1 The above demonstrates that the introduction of a three-dimensional curved conductive framework and multi-metal compound nanocages significantly improves the lithium storage capacity and rate performance of the material. Compared with Comparative Example 2 (graphite + framework binary system), the embodiments of the present invention achieve significantly improved lithium storage capacity and rate performance at 1 A·g. -1 The higher capacity retention after 100 cycles and the approximately 2-fold improvement in high-rate performance demonstrate the contribution of the multi-metal compound nanocage to the capacity and its synergistic effect with graphite and the framework. Compared with Comparative Example 3 (sulfide@rGO single system), the cycling stability of the embodiments of the present invention is significantly improved, with less capacity decay after 100 cycles, demonstrating the key role of the graphite core as a structural support and conductive network in suppressing sulfide volume expansion and improving cycling stability.

[0061] The above results demonstrate that the three-level synergistic structure of graphite core-three-dimensional bent conductive framework-multi-metal compound nanocage constructed in this invention achieves complementary advantages of each component, and possesses high capacity, excellent rate performance and ultra-long cycle life, representing a significant technological advancement.

[0062] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0063] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A graphite-based composite anode material, characterized in that, include: Graphite core; A three-dimensional curved conductive framework is inserted into the interlayer of the graphite core; A multi-metallic compound nanocage, after being coated with a graphene-based coating layer, is uniformly loaded onto the surface of the graphite core.

2. The graphite-based composite anode material according to claim 1, characterized in that, The mass ratio of the graphite core, the three-dimensional curved conductive framework and the multi-metal compound nanocage is (35-60):(17-30):(30-40).

3. The graphite-based composite anode material according to claim 1, characterized in that, The graphite core is a mesophase carbon microsphere.

4. The graphite-based composite anode material according to claim 1, characterized in that, The three-dimensional curved conductive framework is a chlorinated twisted hexabenzo[a]kJ.

5. The graphite-based composite anode material according to claim 1, characterized in that, The multimetallic compound nanocage is a bimetallic sulfide.

6. The graphite-based composite anode material according to claim 5, characterized in that, The bimetallic sulfide is NiS2-Co3S4.

7. The graphite-based composite anode material according to claim 1, characterized in that, After the three-dimensional curved conductive framework is inserted, the interlayer spacing of the graphite core is 0.5 nm to 1.0 nm.

8. A method for preparing the graphite-based composite anode material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. The graphite core and the three-dimensional curved conductive framework are mixed according to the mass ratio, and the mixture is ball-milled and heat-treated to obtain the intercalation composite. S2. Preparation of multi-metal compound nanocages coated with graphene-based coating layers; S3. The intercalation composite obtained in step S1 is mixed with the multi-metal compound nanocage obtained in step S2, and then dispersed, dried and heat-treated to obtain the composite anode material.

9. The preparation method according to claim 8, characterized in that, In step S1, the heat treatment temperature is 300-350℃, the time is 30-60 minutes, and the heat treatment is carried out in an inert atmosphere.

10. The preparation method according to claim 8, characterized in that, Step S2 is as follows: The nickel-cobalt Prussian blue analog precursor was etched to obtain a nanocage structure; Carbon material is coated onto the surface of the nanocage structure and combined with graphene oxide. After heat treatment, a precursor composite is obtained. The precursor complex was subjected to a sulfurization reaction with a sulfur source to obtain a multi-metal compound nanocage coated with the graphene-based coating layer.

11. An electrode sheet, characterized in that, The active material layer of the electrode sheet comprises the graphite-based composite negative electrode material as described in any one of claims 1-7.

12. A lithium-ion battery or sodium-ion battery, characterized in that, It includes the electrode sheet as described in claim 11.

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