Negative pole piece of sodium ion battery and sodium ion battery
By employing a gradient-designed double-layer hard carbon layer structure in the negative electrode of a sodium-ion battery, the problem of homogenization of electrode microstructure in existing technologies has been solved, resulting in an overall performance improvement for sodium-ion batteries, particularly in terms of energy density, rate performance, and cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 深圳为方能源科技有限公司
- Filing Date
- 2026-03-10
- Publication Date
- 2026-05-12
AI Technical Summary
The homogenization of the microstructure of existing sodium-ion battery anode plates makes it impossible to effectively balance the contradiction between high-rate charge and discharge capability and long-term cycle stability, and lacks a spatial dimension of functional gradient distribution design.
A double-layer hard carbon structure is adopted. The particle size and interlayer spacing of the hard carbon particles in the first and second hard carbon layers are designed in a gradient manner. The particle size of the hard carbon particles in the first layer is larger than that in the second layer, and the interlayer spacing is smaller than that in the second layer. Combined with conductive agents, binders and dispersants, a differentiated electrode structure is formed.
The comprehensive performance optimization of the sodium-ion battery negative electrode sheet was achieved, improving energy density, rate performance and cycle stability, and enhancing the overall electrochemical performance of the sodium-ion battery.
Smart Images
Figure CN122025544A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sodium-ion batteries, and more particularly to a sodium-ion battery negative electrode sheet and a sodium-ion battery. Background Technology
[0002] Sodium-ion batteries, as a promising type of electrochemical energy storage device, leverage the widespread distribution of sodium resources, economical manufacturing costs, and safe and reliable operation, demonstrating significant practical value in large-scale stationary energy storage facilities and lightweight electric vehicles. The negative electrode material, as a key component of the battery system, fundamentally impacts the battery's energy storage capacity, charge / discharge speed characteristics, lifespan, and environmental adaptability.
[0003] Hard carbon materials are widely recognized as the most promising anode material for sodium-ion batteries at present due to their moderate preparation cost, convenient raw material acquisition, reasonable sodium ion intercalation potential range, and high theoretical sodium storage capacity. The sodium storage behavior of hard carbon materials is mainly achieved through the reversible intercalation and deintercalation of sodium ions between graphite-like microcrystalline layers, accompanied by surface adsorption and pore filling mechanisms in defect regions and microporous structures within the material. However, current mainstream hard carbon anode manufacturing processes generally employ a single particle size or a simple physical mixture of hard carbon particles to form a highly homogeneous electrode coating. This homogeneous structure results in a lack of functional gradient distribution in the electrode's spatial dimension, making it impossible to effectively balance the contradiction between high-rate charge / discharge capability and long-term cycle stability in practical applications. Specifically, under high-current conditions, the uniformity of ion transport paths easily leads to local concentration gradient imbalances, while during repeated charge / discharge processes, the non-uniformity of volume changes easily induces stress concentration and structural damage within the electrode. While existing research has explored optimizing the performance of hard carbon through surface chemical modification or the introduction of auxiliary components, these methods primarily focus on homogenizing the overall material properties. They fail to establish a spatially ordered functional gradient system at the macroscopic structural level of the electrode and lack systematic structural design tailored to the performance requirements of different regions. Therefore, there is an urgent need to develop a novel negative electrode structure that can achieve synergistic optimization of multiple performance parameters through a spatially gradient layout, thereby significantly improving the overall electrochemical performance of sodium-ion batteries.
[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention
[0005] The purpose of this application is to provide a sodium-ion battery negative electrode and a sodium-ion battery to solve the above-mentioned problems.
[0006] To achieve the above objectives, this application adopts the following technical solution: This application provides a sodium-ion battery negative electrode sheet, including a substrate, a first hard carbon layer, and a second hard carbon layer, wherein the first hard carbon layer is disposed between the substrate and the second hard carbon layer. Based on the total mass of the raw materials for the first hard carbon layer and the second hard carbon layer being 100%, each layer independently comprises: 80%-97% hard carbon particles, 1%-8% conductive agent, 1%-6% binder, and 1%-6% dispersant; Wherein, the particle size of the hard carbon particles in the first hard carbon layer is larger than that of the hard carbon particles in the second hard carbon layer; the interlayer spacing of the hard carbon particles in the first hard carbon layer is smaller than that of the hard carbon particles in the second hard carbon layer.
[0007] Optionally, the substrate includes copper foil or aluminum foil; And / or, The thickness of the substrate is 3-20 μm.
[0008] Optionally, the areal density of the first hard carbon layer and the areal density of the second hard carbon layer are each independently 30-200 g / m³. 2 .
[0009] Optionally, the hard carbon particles in the first hard carbon layer and the second hard carbon layer each independently include at least one of biomass hard carbon, resin hard carbon, coal-based hard carbon, or pitch-based hard carbon.
[0010] Optionally, the particle size distribution of the hard carbon particles in the first hard carbon layer is: D10 is 2.0-3.2 μm, D50 is 5.5-7.5 μm, and D90 is 10.0-15.0 μm; And / or, The particle size distribution of the hard carbon particles in the second hard carbon layer satisfies the following: D10 is 1.5-3.0 μm, D50 is 3.5-5.5 μm, and D90 is 8.0-12.0 μm.
[0011] Optionally, the interlayer spacing d002 of the hard carbon particles in the first hard carbon layer is 0.376-0.382 nm; And / or, The interlayer spacing d002 of the hard carbon particles in the second hard carbon layer is 0.383-0.389 nm.
[0012] Optionally, the conductive agent includes one or more of conductive carbon black SP, acetylene black, Ketjen black, carbon nanotubes, graphene, and conductive graphite.
[0013] Optionally, the adhesive includes styrene-butadiene rubber.
[0014] Optionally, the dispersant includes sodium carboxymethyl cellulose.
[0015] This application also provides a sodium-ion battery, including the negative electrode sheet of the sodium-ion battery.
[0016] Compared with the prior art, the beneficial effects of this application include: The sodium-ion battery anode sheet provided in this application employs a gradient design of the particle size and interlayer spacing of hard carbon particles, resulting in structural differences between the inner and outer hard carbon materials. This synergistically optimizes the overall performance of the sodium-ion battery anode sheet. By sequentially stacking a first hard carbon layer and a second hard carbon layer on both sides of a substrate, and by gradient-designing the particle size and interlayer spacing of the two hard carbon layers, the problem of homogenization of electrode microstructure in existing technologies can be effectively solved. This structural design enables differentiated transport and storage of sodium ions in different active layers, thereby synergistically optimizing the energy density, rate performance, and cycle stability of the anode material, and comprehensively improving the overall performance of the sodium-ion battery. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.
[0018] Figure 1 This is a schematic diagram of the structure of the negative electrode sheet of a sodium-ion battery provided in the example. Detailed Implementation
[0019] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.
[0020] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.
[0021] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.
[0022] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.
[0023] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.
[0024] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).
[0025] To better explain the technical solution provided in this application, the technical solution provided in this application will be described in general before the specific implementation.
[0026] Traditional sodium-ion battery hard carbon anode sheets are typically designed with a single-component or simply mixed active layer structure, resulting in a homogenized microstructure that makes it difficult to simultaneously optimize multiple key performance aspects. Existing research on the modification or composite coating of hard carbon materials focuses primarily on optimizing the uniformity of the material bulk, lacking solutions for systematic and gradient design at the electrode structure level. Consequently, it is difficult to comprehensively improve the overall performance of sodium-ion batteries.
[0027] Therefore, in a first aspect, the application provides a sodium-ion battery negative electrode sheet, including a substrate, a first hard carbon layer, and a second hard carbon layer, wherein the first hard carbon layer is disposed between the substrate and the second hard carbon layer; Based on the total mass of the raw materials for the first hard carbon layer and the second hard carbon layer being 100%, each layer independently comprises: 80%-97% hard carbon particles, 1%-8% conductive agent, 1%-6% binder, and 1%-6% dispersant; Wherein, the particle size of the hard carbon particles in the first hard carbon layer is larger than that of the hard carbon particles in the second hard carbon layer; the interlayer spacing of the hard carbon particles in the first hard carbon layer is smaller than that of the hard carbon particles in the second hard carbon layer.
[0028] Optionally, based on the total mass of the raw materials of the first hard carbon layer and the second hard carbon layer being 100%, the amount of hard carbon particles used independently can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or any value between 80% and 97%; the amount of conductive agent can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any value between 1% and 8%; the amount of binder can be 1%, 2%, 3%, 4%, 5%, 6%, or any value between 1% and 6%; and the amount of dispersant can be 1%, 2%, 3%, 4%, 5%, 6%, or any value between 1% and 6%.
[0029] In one optional embodiment, the substrate comprises copper foil or aluminum foil; And / or, The thickness of the substrate is 3-20 μm.
[0030] Optionally, the thickness of the substrate can be 3μm, 5μm, 10μm, 15μm, 20μm, or any value between 3 and 20μm.
[0031] In one optional embodiment, the areal density of the first hard carbon layer and the areal density of the second hard carbon layer are each independently 30-200 g / m². 2 .
[0032] Optionally, the areal density of the first hard carbon layer and the areal density of the second hard carbon layer can each be independently 30 g / m². 2 50 g / m 2 70 g / m 2 90 g / m 2 110 g / m 2 130 g / m 2 150 g / m 2 170 g / m 2 200 g / m 2 Or 30-200 g / m 2 Any value between.
[0033] In an optional embodiment, the hard carbon particles in the first hard carbon layer and the second hard carbon layer each independently include at least one of biomass hard carbon, resin hard carbon, coal-based hard carbon, or pitch-based hard carbon.
[0034] In an optional embodiment, the particle size distribution of the hard carbon particles in the first hard carbon layer is: D10 is 2.0-3.2 μm, D50 is 5.5-7.5 μm, and D90 is 10.0-15.0 μm; And / or, The particle size distribution of the hard carbon particles in the second hard carbon layer satisfies the following: D10 is 1.5-3.0 μm, D50 is 3.5-5.5 μm, and D90 is 8.0-12.0 μm.
[0035] Optionally, in the particle size distribution of the hard carbon particles in the first hard carbon layer, D10 can be 1.5μm, 2μm, 2.5μm, 3μm, or any value between 1.5 and 2.5μm; D50 can be 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, or any value between 5.5 and 7.5μm; D90 can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any value between 10.0 and 15.0μm.
[0036] Optionally, in the second hard carbon layer, the particle size distribution of the hard carbon particles includes: D10 can be 1.5μm, 2μm, 2.5μm, 3μm, or any value between 1.5 and 3μm; D50 can be 3.5μm, 4μm, 4.6μm, 5μm, 5.5μm, or any value between 3.5 and 5.5μm; D90 can be 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, or any value between 8 and 12μm.
[0037] In an optional embodiment, the interlayer spacing d002 of the hard carbon particles in the first hard carbon layer is 0.376-0.382 nm; And / or, The interlayer spacing d002 of the hard carbon particles in the second hard carbon layer is 0.383-0.389 nm.
[0038] Optionally, the interlayer spacing d002 of the hard carbon particles in the first hard carbon layer can be 0.376 nm, 0.377 nm, 0.378 nm, 0.379 nm, 0.380 nm, 0.381 nm, 0.382 nm, or any value between 0.376 and 0.382 nm.
[0039] Optionally, the interlayer spacing d002 of the hard carbon particles in the second hard carbon layer can be 0.383 nm, 0.384 nm, 0.385 nm, 0.386 nm, 0.387 nm, 0.388 nm, 0.389 nm, or any value between 0.383 and 0.389 nm.
[0040] In one optional embodiment, the conductive agent includes one or more of conductive carbon black SP, acetylene black, Ketjen black, carbon nanotubes, graphene, and conductive graphite.
[0041] In an optional embodiment, the adhesive comprises styrene-butadiene rubber (SBR).
[0042] In an optional embodiment, the dispersant comprises sodium carboxymethyl cellulose (CMC).
[0043] Secondly, this application also provides a sodium-ion battery, including the negative electrode sheet of the sodium-ion battery.
[0044] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.
[0045] The specifications of the hard carbon particles used in the examples and comparative examples are shown in Table 1: Table 1. Specifications of the hard carbon particles used in the examples and comparative examples.
[0046] In the examples and comparative examples, hard carbon 1 (purchased from BTR New Materials Group Co., Ltd.), hard carbon 2 (purchased from Chengdu Baisige Technology Co., Ltd.), hard carbon 3 (purchased from Wuhan Tianna Technology Co., Ltd.), hard carbon 4 (purchased from Jinan Shengquan Group Co., Ltd.), sodium carboxymethyl cellulose (CMC purchased from Nippon Paper Co., Ltd.), and styrene-butadiene rubber (SBR, purchased from Shanghai Daoying Industrial Co., Ltd.) were used.
[0047] Example 1 This embodiment provides a sodium-ion battery negative electrode sheet, the structure of which is as follows: Figure 1 As shown: The coating comprises a substrate, a first hard carbon layer (coating 1), and a second hard carbon layer (coating 2); the first hard carbon layer is located between the substrate and the second hard carbon layer; wherein the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 40 g / m³. 2 The areal density of the second hard carbon layer is 40 g / m³.2 .
[0048] Based on the total mass of the raw materials for the first hard carbon layer being 100%, it includes: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0049] The total mass of the raw materials for the second hard carbon layer is calculated as 100%, including: 96% hard carbon 2, 1% SP, 1% CMC, and 2% SBR.
[0050] This embodiment also provides a method for preparing the negative electrode sheet of the sodium-ion battery, the specific steps of which are as follows: Slurries for the first hard carbon layer and the second hard carbon layer were prepared separately. The first hard carbon layer slurry and the second hard carbon layer slurry were then applied to the substrate by double-layer extrusion. After drying, the sodium-ion battery negative electrode sheet was obtained.
[0051] This embodiment also provides a sodium-ion battery, using the aforementioned negative electrode sheet; the positive electrode substrate is made of 12µm aluminum foil, the separator is a PP / PE / ceramic composite separator, and the electrolyte is a mixture of sodium hexafluorophosphate, EC, EMC, PC, etc. After assembly into a battery, battery capacity testing is performed to calculate the first-cycle efficiency, and then the cycle capacity retention rate at room temperature and low temperature (-10℃) is tested.
[0052] Example 2 This embodiment provides a sodium-ion battery negative electrode sheet: The device includes a substrate, a first hard carbon layer, and a second hard carbon layer; the first hard carbon layer is located between the substrate and the second hard carbon layer; wherein the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 40 g / m³. 2 The areal density of the second hard carbon layer is 40 g / m³. 2 .
[0053] Based on the total mass of the raw materials for the first hard carbon layer being 100%, it includes: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0054] The total mass of the raw materials for the second hard carbon layer is calculated as 100%, including: 96% hard carbon 3, 1% SP, 1% CMC, and 2% SBR.
[0055] This embodiment also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Embodiment 1.
[0056] This embodiment also provides a sodium-ion battery, using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Embodiment 1. After assembly into a battery, a battery capacity test is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10℃) is tested.
[0057] Example 3 This embodiment provides a sodium-ion battery negative electrode sheet: The device includes a substrate, a first hard carbon layer, and a second hard carbon layer; the first hard carbon layer is located between the substrate and the second hard carbon layer; wherein the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 30 g / m³. 2 The areal density of the second hard carbon layer is 50 g / m³. 2 .
[0058] Based on the total mass of the raw materials for the first hard carbon layer being 100%, it includes: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0059] The total mass of the raw materials for the second hard carbon layer is calculated as 100%, including: 96% hard carbon 3, 1% SP, 1% CMC, and 2% SBR.
[0060] This embodiment also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Embodiment 1.
[0061] This embodiment also provides a sodium-ion battery, using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Embodiment 1. After assembly into a battery, a battery capacity test is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10℃) is tested.
[0062] Comparative Example 1 This comparative example provides a sodium-ion battery negative electrode sheet: The device includes a substrate, a first hard carbon layer, and a second hard carbon layer; the first hard carbon layer is located between the substrate and the second hard carbon layer; wherein the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 30 g / m³. 2 The areal density of the second hard carbon layer is 50 g / m³. 2 .
[0063] Based on the total mass of the raw materials for the first hard carbon layer being 100%, it includes: 96% hard carbon 2, 1% SP, 1% CMC, and 2% SBR.
[0064] The total mass of the raw materials for the second hard carbon layer is calculated as 100%, including: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0065] This comparative example also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Example 1.
[0066] This comparative example also provides a sodium-ion battery using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Example 1. After assembly into a battery, battery capacity testing is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10°C) is tested.
[0067] Comparative Example 2 This comparative example provides a sodium-ion battery negative electrode sheet: It includes a substrate and a hard carbon layer; the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 80 g / m². 2 .
[0068] Based on the total mass of the raw materials for the hard carbon layer being 100%, it includes: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0069] This comparative example also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Example 1.
[0070] This comparative example also provides a sodium-ion battery using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Example 1. After assembly into a battery, battery capacity testing is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10°C) is tested.
[0071] Comparative Example 3 This comparative example provides a sodium-ion battery negative electrode sheet: It includes a substrate and a hard carbon layer; the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 80 g / m². 2 .
[0072] Based on the total mass of the raw materials for the hard carbon layer being 100%, it includes: 96% hard carbon 2, 1% SP, 1% CMC, and 2% SBR.
[0073] This comparative example also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Example 1.
[0074] This comparative example also provides a sodium-ion battery using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Example 1. After assembly into a battery, battery capacity testing is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10°C) is tested.
[0075] Comparative Example 4 This comparative example provides a sodium-ion battery negative electrode sheet: It includes a substrate and a hard carbon layer; the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 80 g / m². 2 .
[0076] Based on the total mass of the raw materials for the hard carbon layer being 100%, it includes: 48% hard carbon 1, 48% hard carbon 2, 1% SP, 1% CMC, and 2% SBR.
[0077] This comparative example also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Example 1.
[0078] This comparative example also provides a sodium-ion battery using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Example 1. After assembly into a battery, battery capacity testing is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10°C) is tested.
[0079] Comparative Example 5 This comparative example provides a sodium-ion battery negative electrode sheet: The device includes a substrate, a first hard carbon layer, and a second hard carbon layer; the first hard carbon layer is located between the substrate and the second hard carbon layer; wherein the substrate is an aluminum foil with a thickness of 12 μm. The areal density of the first hard carbon layer is 30 g / m³. 2 The areal density of the second hard carbon layer is 50 g / m³. 2 .
[0080] Based on the total mass of the raw materials for the first hard carbon layer being 100%, it includes: 96% hard carbon 4, 1% SP, 1% CMC, and 2% SBR.
[0081] The total mass of the raw materials for the second hard carbon layer is calculated as 100%, including: 96% hard carbon 1, 1% SP, 1% CMC, and 2% SBR.
[0082] This comparative example also provides a method for preparing the negative electrode sheet of the sodium-ion battery, which is the same as in Example 1.
[0083] This comparative example also provides a sodium-ion battery using the aforementioned negative electrode sheet; the remaining raw materials are the same as in Example 1. After assembly into a battery, battery capacity testing is performed, the initial efficiency is calculated, and then the cycle capacity retention rate at room temperature and low temperature (-10°C) is tested.
[0084] The electrical performance of the sodium-ion batteries provided in the examples and comparative examples is shown in Table 2: Table 2 shows the electrical performance of the sodium-ion batteries provided in the examples and comparative examples.
[0085] As can be seen, the embodiment not only has high capacity and first-time efficiency, but also good room temperature cycling performance and low temperature cycling performance. This is due to the directional design of the electrode. The hard carbon on the surface has excellent kinetic performance. During charging and discharging, the surface layer with the largest ion flux first inserts or de-inserts sodium ions, improving kinetic performance. The hard carbon at the bottom layer has good electronic conductivity. During charging and discharging, the bottom layer with the largest electron flux quickly transfers electrons, reducing battery polarization. Furthermore, its high first-time efficiency and capacity help to improve the battery capacity.
[0086] Comparative Example 1 uses the opposite approach, resulting in poorer battery cycle performance and lower initial efficiency. Comparative Examples 2 and 3 use a single structure, which cannot simultaneously meet the requirements of capacity and cycle stability. Comparative Example 4 uses a direct mixing method, which achieves some balance, but the overall effect is not as good as the examples. Comparative Example 5 uses graphite hard carbon 4, which has a larger particle size. Although the design is similar to Example 1, due to insufficient material kinetics, sodium precipitation is still easy during cycling, leading to poor cycle stability.
[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended 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. Such 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.
[0088] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
Claims
1. A sodium-ion battery negative electrode sheet, characterized in that, include: A substrate, a first hard carbon layer, and a second hard carbon layer; the first hard carbon layer is disposed between the substrate and the second hard carbon layer; Based on the total mass of the raw materials for the first hard carbon layer and the second hard carbon layer being 100%, each layer independently comprises: 80%-97% hard carbon particles, 1%-8% conductive agent, 1%-6% binder, and 1%-6% dispersant; Wherein, the particle size of the hard carbon particles in the first hard carbon layer is larger than that of the hard carbon particles in the second hard carbon layer; the interlayer spacing of the hard carbon particles in the first hard carbon layer is smaller than that of the hard carbon particles in the second hard carbon layer.
2. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The substrate includes copper foil or aluminum foil; And / or, The thickness of the substrate is 3-20 μm.
3. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The areal density of the first hard carbon layer and the areal density of the second hard carbon layer are each independently 30-200 g / m³. 2 .
4. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The hard carbon particles in the first hard carbon layer and the second hard carbon layer each independently include at least one of biomass hard carbon, resin hard carbon, coal-based hard carbon, or pitch-based hard carbon.
5. The sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The particle size distribution of the hard carbon particles in the first hard carbon layer is as follows: D10 is 2.0-3.2 μm, D50 is 5.5-7.5 μm, and D90 is 10.0-15.0 μm; And / or, The particle size distribution of the hard carbon particles in the second hard carbon layer satisfies the following: D10 is 1.5-3.0 μm, D50 is 3.5-5.5 μm, and D90 is 8.0-12.0 μm.
6. The sodium-ion battery negative electrode sheet according to claim 4, characterized in that, The interlayer spacing d002 of the hard carbon particles in the first hard carbon layer is 0.376-0.382 nm; And / or, The interlayer spacing d002 of the hard carbon particles in the second hard carbon layer is 0.383-0.389 nm.
7. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and conductive graphite.
8. The sodium-ion battery negative electrode sheet according to claim 1, characterized in that, The adhesive includes styrene-butadiene rubber.
9. The sodium-ion battery negative electrode sheet according to any one of claims 1-8, characterized in that, The dispersant includes sodium carboxymethyl cellulose.
10. A sodium-ion battery, characterized in that, Includes the sodium-ion battery negative electrode sheet as described in any one of claims 1-9.