Sodium-ion battery composite negative electrode material, preparation method thereof, sodium-ion battery and negative electrode plate of sodium-ion battery
By mixing hard carbon with graphite in sodium-ion batteries, graphite acts as a "skeleton" to improve compaction density and conductive network, solving the problem of low compaction density of hard carbon anode materials and achieving improved volumetric energy density and cost-effectiveness in batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-24
AI Technical Summary
The low compaction density of hard carbon anode materials in existing sodium-ion batteries results in insufficient volumetric energy density, making it difficult to promote in applications with high space utilization. Furthermore, existing improvement methods are costly or have limited effectiveness.
Hard carbon materials and graphite materials are mixed in a certain proportion, with graphite serving as a "skeleton" functional additive. The mixture is uniformly mixed by dry or wet methods to improve the compaction density and conductive network structure of the electrode materials.
It significantly improves the compaction density and volumetric energy density of electrode materials, enhances slurry processing performance, reduces production costs, and has good potential for commercial application.
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Figure CN121726367A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of secondary battery technology, and more specifically, to a sodium-ion battery composite negative electrode material and its preparation method, as well as a sodium-ion battery and its negative electrode sheet. Background Technology
[0002] With the ever-increasing demand for energy storage, sodium-ion batteries, due to their abundant sodium resources and low cost, are considered an important supplement to lithium-ion batteries in the field of large-scale energy storage. Among the key materials of sodium-ion batteries, the performance of the anode material directly determines the overall energy density and cycle life of the battery. Hard carbon materials, due to their suitable sodium intercalation potential, high reversible specific capacity, and relatively mature preparation process, have become the most commercially promising anode material for sodium-ion batteries and are widely used in the design and manufacturing of existing sodium-ion batteries.
[0003] In actual electrode fabrication, hard carbon materials are typically formed into electrode sheets through processes such as stirring and dispersion, coating, and rolling. However, because hard carbon is essentially an amorphous carbon material with irregular particle morphology and numerous micropores and structural defects, it is difficult to achieve efficient densification during compaction. Therefore, under current electrode processing conditions, the compaction density of hard carbon anodes is generally low, typically not exceeding 1.0 g / cm³. This low compaction density limits the amount of active material per unit volume, resulting in high electrode porosity and significantly reducing the volumetric energy density of the battery. This problem severely restricts the promotion and use of sodium-ion batteries in applications with high space utilization requirements (such as electric vehicles and portable electronic devices).
[0004] To improve the overall performance of hard carbon anodes, existing technologies mainly focus on optimizing their electrochemical properties through structural control or surface modification of the hard carbon materials themselves, such as adjusting the type of precursor, controlling the pyrolysis temperature, or introducing heteroatom doping. In addition, some studies have attempted to combine hard carbon with one-dimensional or two-dimensional carbon nanomaterials (such as carbon nanotubes and graphene) to improve their conductive network and mechanical stability. However, due to the high flexibility and easy stacking characteristics of these carbon nanomaterials, slippage or interlayer rearrangement easily occurs during rolling, failing to effectively provide rigid support. Therefore, their contribution to improving the overall electrode compaction density is limited, and they often lead to increased costs and process complexity.
[0005] Meanwhile, graphite, as the most mainstream anode material in lithium-ion batteries, possesses a highly ordered layered structure and excellent intrinsic density. Its compaction density under the same processing conditions can reach over 1.6 g / cm³, exhibiting good volume utilization efficiency. However, in sodium-ion battery systems, due to the large radius of sodium ions, it is difficult to stably intercalate into the graphite interlayer to form intercalation compounds in conventional ester electrolytes, resulting in extremely low reversible capacity (typically not exceeding 35 mAh / g) and poor cycle performance. Therefore, in the general understanding of those skilled in the art, graphite is considered unsuitable as an anode material for sodium-ion batteries, and related technical routes have long been excluded. There is also a lack of technical inspiration for using it to improve the processing performance of other anode materials. Based on the above situation, existing technologies have not yet proposed a technical solution that can significantly improve the compaction density of hard carbon-based electrodes while also possessing good feasibility and cost-effectiveness.
[0006] In view of this, the present invention is proposed. Summary of the Invention
[0007] The purpose of this invention is to provide a sodium-ion battery composite negative electrode material and its preparation method, as well as a sodium-ion battery and its negative electrode sheet, to improve the above-mentioned technical problems.
[0008] This invention is implemented as follows: In a first aspect, the present invention provides a sodium-ion battery composite anode material, which is a mixture of hard carbon material and graphite material, wherein the mass of the graphite material accounts for 1% to 20% of the sodium-ion battery composite anode material, and the powder tap density of the sodium-ion battery composite anode material is greater than 0.7 g / cm³.
[0009] In an optional embodiment, the graphite material accounts for 10% to 20% of the mass of the sodium-ion battery composite negative electrode material, preferably 8% to 12%.
[0010] In an optional embodiment, the particle size D50 of the graphite material is 3μm~15μm; In an optional embodiment, the graphite material is a near-spherical artificial graphite with a D50 of 9 μm to 11 μm.
[0011] In an optional embodiment, the specific surface area of the hard carbon material is 20 m² / g to 30 m² / g, preferably 22 m² / g to 28 m² / g, and the tap density of the powder is 0.6 g / cm³ to 0.7 g / cm³, preferably 0.63 g / cm³ to 0.68 g / cm³.
[0012] In an optional embodiment, the powder tap density of the sodium-ion battery composite negative electrode material is 0.7 g / cm³ to 0.88 g / cm³, and the electrode sheet compaction density is greater than 1.2 g / cm³.
[0013] In an optional embodiment, the electrode compaction density of the sodium-ion battery composite negative electrode material is 1.3 g / cm³ to 1.6 g / cm³.
[0014] Secondly, the present invention provides a method for preparing a sodium-ion battery composite negative electrode material as described in any of the foregoing embodiments, comprising: uniformly mixing the hard carbon material and the graphite material in a preset ratio by a dry or wet method.
[0015] Thirdly, the present invention provides a sodium-ion battery negative electrode sheet, which includes a current collector and a coating coated on the current collector, the coating including a conductive agent, a binder, and a sodium-ion battery composite negative electrode material as described in any of the foregoing embodiments.
[0016] Fourthly, the present invention provides a sodium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the sodium-ion battery negative electrode sheet described in the foregoing embodiments.
[0017] This invention offers the following advantages: It innovatively breaks through the traditional misconception that "graphite lacks sodium storage capacity and therefore has no application value," redefining graphite as a "physical functional additive" rather than a primary active substance. Based on its high density and rigid particle characteristics, graphite acts as a "skeleton" in a hard carbon matrix, effectively reducing material porosity during the rolling process, thereby significantly improving compaction density. By moderately reducing specific capacity, a net gain in volumetric energy density is achieved. The introduction of graphite not only improves the compaction density of the electrode material, but its excellent lubrication properties also significantly improve the slurry's processing performance, ensuring coating uniformity. Simultaneously, graphite may construct a more efficient conductive network structure, which is beneficial for improving the material's rate performance. Furthermore, compared to high-cost nanomaterials such as carbon nanotubes and graphene, the graphite used in this technology is a mature, readily available industrial raw material with significant cost advantages, adding almost no additional production costs and possessing outstanding commercial application potential. Moreover, the material preparation process is simple, cost-effective, and has good feasibility for large-scale production. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a SEM image of pure hard carbon from Comparative Example 1 of this invention. Figure 2 This is a SEM image of the sodium-ion battery composite negative electrode material of Example 1 of the present invention; Figure 3 This is a SEM image of the sodium-ion battery composite negative electrode material of Comparative Example 4 of the present invention. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0021] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.
[0022] In the description of this invention, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural 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 a single or multiple.
[0023] The following is a detailed description of a sodium-ion battery composite negative electrode material, its preparation method, and the sodium-ion battery and its negative electrode sheet provided by the present invention.
[0024] Some embodiments of the present invention provide a sodium-ion battery composite anode material, which is a mixture of hard carbon material and graphite material, wherein the mass of graphite material accounts for 1% to 20% of the sodium-ion battery composite anode material, and the powder tap density of the sodium-ion battery composite anode material is greater than 0.7 g / cm³.
[0025] Through extensive research and practice, the inventors broke through the traditional misconception that "graphite lacks sodium storage capacity and therefore has no application value," redefining graphite as a "physical functional additive" rather than a primary active substance. By controlling the graphite content and powder tap density parameters, combined with its inherent high density and rigid particle characteristics, graphite plays a structural "skeleton" role in a hard carbon matrix. This design effectively suppresses material porosity formation during the rolling process, thereby significantly improving the compaction density of the electrode material. Through technological optimization, an optimal balance between specific capacity and volumetric energy density was achieved, ultimately resulting in a net increase in volumetric energy density.
[0026] The introduction of graphite materials has multiple technical advantages: First, it significantly improves the electrode compaction density of the electrode material; second, it significantly improves the slurry processing performance due to its excellent lubrication properties, ensuring the uniformity of electrode coating; and third, it may construct a more complete conductive network structure, which plays an important role in improving the rate performance of the material.
[0027] From an industrialization perspective, compared to high-cost nanomaterials such as carbon nanotubes and graphene, the graphite used in this technology is a mature, readily available industrial raw material. It not only does not significantly increase production costs but also demonstrates outstanding commercial application prospects due to its excellent cost-effectiveness. This material selection strategy ensures both performance improvement and cost control, providing a practical and feasible technical solution for large-scale production.
[0028] For reference, the mass percentage of graphite material in the sodium-ion battery composite anode material is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, respectively. In some embodiments, the content of graphite material is further optimized, with the mass percentage of graphite material in the sodium-ion battery composite anode material being 10% to 20%, more preferably 8% to 12%.
[0029] In some embodiments, in order to enable the graphite material to be fully mixed with the hard carbon material and to play a better structural "skeleton" role and to suppress the formation of porosity during the rolling process, the particle size D50 of the graphite material can be selected as 3μm~15μm.
[0030] Among them, spherical artificial graphite with a moderate particle size is more conducive to forming composite cathode materials with hard carbon, resulting in excellent packing performance (high tap density) and direct conversion to the highest electrode compaction density after rolling. Specifically, in some embodiments, the graphite material is spherical artificial graphite with a D50 of 9μm~11μm.
[0031] In some embodiments, the specific surface area of the hard carbon material is 20 m² / g to 30 m² / g, preferably 22 m² / g to 28 m² / g, and the tap density of the powder is 0.6 g / cm³ to 0.7 g / cm³, preferably 0.63 g / cm³ to 0.68 g / cm³. Hard carbon with this specific surface area is predominantly characterized by a suitable mesoporous / microporous ratio, providing sufficient Na₂O₃. + The storage sites are optimized to avoid increased ion diffusion resistance caused by excessive micropores, thus balancing rate performance and cycle stability. The hard carbon particles in this tap density range have uniform morphology (no excessive agglomeration or excessively fine particle size), are tightly packed, and have appropriate porosity. This reduces the internal contact resistance of the electrode and provides channels for electrolyte wetting, ensuring high electron / ion conduction efficiency at high rates.
[0032] In some embodiments, the powder tap density of the sodium-ion battery composite anode material is 0.7 g / cm³ to 0.88 g / cm³, and the electrode compaction density is greater than 1.2 g / cm³. Preferably, the electrode compaction density of the sodium-ion battery composite anode material is 1.3 g / cm³ to 1.6 g / cm³. The composite anode material with the above-mentioned larger electrode compaction density can achieve better volumetric energy density and specific capacity.
[0033] Some embodiments of the present invention also provide a method for preparing a sodium-ion battery composite negative electrode material as described in any of the foregoing embodiments, comprising: uniformly mixing the hard carbon material and the graphite material in a preset ratio by a dry or wet method.
[0034] Furthermore, some embodiments of the present invention also provide a sodium-ion battery negative electrode sheet, which includes a current collector and a coating coated on the current collector, the coating including a conductive agent, a binder, and a sodium-ion battery composite negative electrode material as described in any of the foregoing embodiments.
[0035] Furthermore, some embodiments of the present invention also provide a sodium-ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the sodium-ion battery negative electrode sheet described in the aforementioned embodiments.
[0036] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0037] Example 1 This embodiment provides a method for preparing a composite negative electrode material for sodium-ion batteries, which includes: Hard carbon and graphite were dry-mixed in a three-dimensional mixer for 4 hours to ensure uniform mixing, thus obtaining the sodium-ion battery composite anode material. The mass ratio of hard carbon to graphite was 90:10, and the hard carbon was biomass-derived hard carbon with a specific surface area of 25 m². 2 / g, tap density 0.65g / cm³ 3 The graphite is a near-spherical artificial graphite with a D50 of 10 μm.
[0038] Example 2 The only difference between this embodiment and Embodiment 1 is that the graphite is artificial graphite with D50=3μm and a micro powder morphology.
[0039] Example 3 The only difference between this embodiment and Embodiment 1 is that the graphite is flake-shaped natural graphite with D50=15μm.
[0040] Comparative Example 1 This comparative example uses pure hard carbon from Example 1.
[0041] Comparative Example 2 The only difference between this comparative example and Example 1 is that sheet-like nanoscale graphene oxide (GO) is used instead of graphite.
[0042] The negative electrode materials of Examples 1-3 and Comparative Examples 1-2, the conductive agent SuperP, and the binder PAA-Na (polyacrylic acid) were stirred in deionized water at a mass ratio of 92:4:4 to prepare a uniform slurry. The slurry was coated onto aluminum foil, dried at 100°C, and cold-pressed to obtain the negative electrode sheet. The powder tap density of the sodium-ion battery composite negative electrode material and the compaction density of the electrode sheet were measured. The compaction density of the electrode sheet was calculated by measuring the areal density, thickness, and coating area of the electrode sheet. The results are shown in Table 1.
[0043] Table 1
[0044] Analysis of the results in Table 1 shows that micron-sized bulk graphite materials (Examples 1 and 3) exhibit a significantly superior performance to nanosheet graphite (Comparative Example 2) in improving electrode compaction density. This phenomenon confirms that graphite can only fully function as a "skeleton structure" for pore suppression when it exists in the form of micron-sized particles. Among them, artificial graphite with a near-spherical morphology and moderate particle size distribution (Example 1) exhibits the best performance. The outstanding packing characteristics of this material (manifested as the highest tap density) directly translate into the highest electrode compaction density after the rolling process. It is worth noting that nanocarbon materials such as graphene oxide (GO) should be avoided because they are prone to interlayer slip and re-stacking, and cannot provide a stable rigid support structure. This finding is fundamentally different from the traditional design approach of mainly improving the conductivity of composite materials by adding conductive agents.
[0045] Example 4 The only difference between this embodiment and Embodiment 1 is that the mass ratio of hard carbon to graphite is 95:5.
[0046] Example 5 The only difference between this embodiment and Embodiment 1 is that the mass ratio of hard carbon to graphite is 88:12.
[0047] Example 6 The only difference between this embodiment and Embodiment 1 is that the mass ratio of hard carbon to graphite is 85:15.
[0048] Example 7 The only difference between this embodiment and Embodiment 1 is that the mass ratio of hard carbon to graphite is 80:20.
[0049] Comparative Example 3 The only difference between this comparative example and Example 1 is that the mass ratio of hard carbon to graphite is 75:25.
[0050] Comparative Example 4 The only difference between this comparative example and Example 1 is that the mass ratio of hard carbon to graphite is 70:30.
[0051] Comparative Example 5 The only difference between this comparative example and Example 1 is that the mass ratio of hard carbon to graphite is 50:50.
[0052] The negative electrode materials of Examples 1, 4-7 and Comparative Examples 1, 3-5, the conductive agent SuperP, and the binder PAA-Na (polyacrylic acid) were mixed in deionized water at a mass ratio of 92:4:4 to prepare a homogeneous slurry. The slurry was coated onto aluminum foil, dried at 100°C, and cold-pressed to obtain a negative electrode sheet. Electrochemical performance was then tested. The specific test method was as follows: using the prepared negative electrode as the working electrode and sodium metal as the counter / reference electrode, a CR2032 button cell was assembled, and charge-discharge tests were performed at room temperature (voltage range 0.01V~2.0V). The test results are shown in Table 2.
[0053] Table 2
[0054] The experimental results in Table 2 show that the compaction density increases monotonically with increasing graphite content, but the rate of increase gradually slows down. The increase in compaction density is most significant within the graphite content range of 0% to 15%; however, the rate of increase plateaus after the content exceeds 20%. The maximum volumetric capacity clearly occurs in the graphite content range of 10% to 15%, reaching a peak of 399 mAh / cm³. When the graphite content further increases to 20%, the volumetric capacity decreases. This indicates that the change in volumetric capacity is not a gradual transition after a simple trade-off between various factors, but rather exhibits a clear and sharp optimal range. The above technical effects are non-obvious and cannot be directly derived by those skilled in the art based on existing technology, demonstrating the innovation and technological breakthrough of this technical solution.
[0055] Cross-sections of the electrodes prepared from the pure hard carbon of Comparative Example 1, the composite anode materials of Example 1, and Comparative Example 4 were observed using scanning electron microscopy. The corresponding SEM images are shown below. Figures 1-3 As shown.
[0056] from Figure 1 It can be seen that the structure is loose, with a large number of irregular pores and irregular particle accumulations, which explains its low compaction density (0.98 g / cm³). 3 The direct cause of ).
[0057] from Figure 2 It can be seen that the material exhibits a highly dense microstructure, with a significantly reduced porosity compared to its original state. Microscopic observation reveals that spherical graphite particles are uniformly distributed within the hard carbon amorphous matrix. These graphite particles play a dual role in the structure: firstly, they act as rigid support units, filling the macroscopic pores between hard carbon particles; secondly, they effectively suppress compressive elastic deformation of the material during the rolling process, thereby promoting a more compact packing morphology. This structural feature significantly improves the overall density of the material.
[0058] from Figure 3It can be seen that although the material has high density, obvious graphite particle enrichment can be observed in its microstructure. Due to the excessively high graphite phase content, the continuous phase structure of the hard carbon matrix is disrupted, potentially leading to the formation of numerous graphite-graphite direct contact interfaces. Microscopic analysis suggests that this structural feature may adversely affect the conduction of sodium ions throughout the electrode. Furthermore, because the graphite phase itself has low electrochemical activity, this structural defect will significantly reduce the material's specific capacity. This microstructural feature can reasonably explain the experimentally observed phenomenon: when the graphite content reaches 30%, the material's volumetric capacity has fallen back to a level comparable to that at 5% content.
[0059] Full battery performance verification Experimental scheme: Prussian white cathode material was used, and composite anode materials from Comparative Example 1, Example 1, and Example 9 were used to prepare anode sheets according to the aforementioned method. A full cell (CR2032) was assembled, and the electrolyte was 1M NaPF6 in EC / DEC. Testing: The volumetric energy density based on the full cell volume was calculated. The results are shown in Table 3.
[0060] Table 3
[0061] The experimental results in Table 3 show that, in the final full-cell application, using the negative electrode material of Example 1 (containing 10% graphite) can increase the volumetric energy density of the battery by 31%; while using the negative electrode material within the range defined in Comparative Example 4 (containing 30% graphite), the increase in volumetric energy density is only 21%, showing a significant difference between the two. These results fully demonstrate that the selection of graphite content represents a significant and substantial advancement in improving battery energy density, exhibiting unexpected technical effects, significant technological advantages, and broad commercial application prospects.
[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A sodium-ion battery composite negative electrode material, characterized in that, It is a mixture of hard carbon material and graphite material, wherein the mass of the graphite material accounts for 1% to 20% of the sodium-ion battery composite anode material, and the powder tap density of the sodium-ion battery composite anode material is greater than 0.7 g / cm³.
2. The sodium-ion battery composite negative electrode material according to claim 1, characterized in that, The graphite material accounts for 10% to 20% of the mass of the sodium-ion battery composite anode material, preferably 8% to 12%.
3. The sodium-ion battery composite negative electrode material according to claim 1, characterized in that, The particle size D50 of the graphite material is 3μm~15μm.
4. The sodium-ion battery composite negative electrode material according to claim 1, characterized in that, The graphite material is a near-spherical artificial graphite with a D50 of 9μm to 11μm.
5. A sodium-ion battery composite negative electrode material according to any one of claims 1 to 4, characterized in that, The specific surface area of the hard carbon material is 20 m² / g to 30 m² / g, preferably 22 m² / g to 28 m² / g, and the tap density of the powder is 0.6 g / cm³ to 0.7 g / cm³, preferably 0.63 g / cm³ to 0.68 g / cm³.
6. A sodium-ion battery composite negative electrode material according to any one of claims 1 to 4, characterized in that, The powder tap density of the sodium-ion battery composite negative electrode material is 0.7 g / cm³ to 0.88 g / cm³, and the electrode sheet compaction density is greater than 1.2 g / cm³.
7. The sodium-ion battery composite negative electrode material according to claim 6, characterized in that, The compressive density of the sodium-ion battery composite negative electrode material is 1.3 g / cm³ to 1.6 g / cm³.
8. A method for preparing a sodium-ion battery composite negative electrode material as described in any one of claims 1 to 7, characterized in that, It includes: The hard carbon material and the graphite material are uniformly mixed in a preset ratio using a dry or wet method.
9. A sodium-ion battery negative electrode sheet, characterized in that, It includes a current collector and a coating applied to the current collector, the coating including a conductive agent, a binder, and a sodium-ion battery composite negative electrode material as described in any one of claims 1 to 7.
10. A sodium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the sodium-ion battery negative electrode sheet according to claim 9.