Hard carbon anode material, anode, sodium-ion battery, and apparatus

Abstract

A hard carbon anode material, a 2θ value VC corresponding to a diffraction peak of a (002) crystal plane in an XRD pattern of the hard carbon anode material, an ID / IG value VD / G in Raman spectroscopy, and an oil absorption value VDBP measured by mL / 100 g satisfying the following: 0.8≤VC / VDBP+VD / G≤12.60. The present application further provides an anode using the hard carbon anode material, a sodium-ion battery, and an apparatus.

Description

Hard carbon negative electrode material, negative electrode, sodium ion battery and device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311868252.1 and application name “Hard Carbon Negative Electrode Materials, Negative Electrodes, Sodium Ion Batteries and Devices”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of sodium ion batteries, and in particular to a hard carbon negative electrode material, a negative electrode, a sodium ion battery and a device. Background Art

[0003] The global scarcity and high price of lithium resources have constrained the development of lithium-ion batteries. The market has begun to seek alternatives to lithium-ion batteries. However, sodium-ion batteries, due to their similar energy storage principles and abundant sodium resources, are more likely to meet the future demand for low-cost large-scale energy storage devices.

[0004] Currently, hard carbon materials are widely used as negative electrode active materials in sodium-ion batteries. As the comprehensive performance requirements for sodium-ion batteries become increasingly stringent, higher requirements are also being placed on hard carbon negative electrode materials. However, the hard carbon negative electrode materials currently used in sodium-ion batteries cannot achieve both high energy density and good fast charging performance.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a hard carbon negative electrode material, wherein multiple parameters of the hard carbon negative electrode material satisfy a certain relationship, which can ensure that the hard carbon negative electrode material can take into account both high capacity and good kinetic performance, thereby enabling the sodium ion battery made using the hard carbon negative electrode material to take into account both high energy density and fast charging performance.

[0007] Specifically, the first aspect of the present application provides a hard carbon negative electrode material, wherein the 2θ angle value corresponding to the diffraction peak of the (002) crystal plane in the XRD spectrum of the hard carbon negative electrode material is V C °; The Raman spectrum of the hard carbon negative electrode material I D / I G The value is V D / G The oil absorption value of the hard carbon negative electrode material is V DBP mL / 100g; wherein, the hard carbon negative electrode material satisfies: 0.8≤V C / V DBP +V D / G ≤12.6.

[0008] The above parameters V of hard carbon negative electrode materials C 、VD / G 、V DBP When the above relationship and its defined range are met, the kinetic performance is good and the capacity is high, which is conducive to the preparation of a sodium ion battery with both high energy density and fast charging performance.

[0009] In one embodiment, the V C In the range of 20-26.

[0010] In one embodiment, the V D / G In the range of 0.5-10.0.

[0011] In one embodiment, the V DBP In the range of 10-100.

[0012] In one embodiment, 1.0≤V C / V DBP +V D / G ≤10.0.

[0013] In one embodiment, 1.28≤V C / V DBP +V D / G ≤4.12.

[0014] In one embodiment, the V C In the range of 22-25.

[0015] In one embodiment, the V D / G In the range of 1.0-3.5.

[0016] In one embodiment, the V DBP In the range of 40-80.

[0017] In one embodiment, the D50 of the hard carbon negative electrode material is 2 μm-20 μm.

[0018] In a second aspect, the present application provides a negative electrode comprising the hard carbon negative electrode material described in the first aspect of the present application. Due to the inclusion of the hard carbon negative electrode material in the negative electrode, the negative electrode can be used to provide a sodium ion battery that achieves both fast charging performance and high energy density.

[0019] In a third aspect, the present application provides a sodium ion battery comprising the negative electrode described in the second aspect of the present application and a positive electrode. The sodium ion battery has good fast charging performance and high energy density.

[0020] The fourth aspect of the present application provides a device having a sodium ion battery as described in the third aspect of the present application, which is an electrical device or an energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is an XRD spectrum of the hard carbon negative electrode material of Example 3 of the present application;

[0022] FIG2 is a Raman spectrum of the hard carbon negative electrode material of Example 3 of the present application;

[0023] FIG3 is a schematic structural diagram of a negative electrode provided in an embodiment of the present application;

[0024] FIG4 is a schematic structural diagram of a sodium ion battery provided in an embodiment of the present application;

[0025] FIG5 is a schematic structural diagram of a device including a sodium ion battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The embodiments of the present application provide a hard carbon negative electrode material that can enable sodium ion batteries to have both high energy density and fast charging performance.

[0027] Specifically, the embodiment of the present application provides a hard carbon negative electrode material, wherein the 2θ angle value corresponding to the diffraction peak of the (002) crystal plane in the XRD spectrum of the hard carbon negative electrode material is V C °; The Raman spectrum of the hard carbon negative electrode material I D / I G The value is V D / G The oil absorption value of the hard carbon negative electrode material is V DBP mL / 100g; wherein, the hard carbon negative electrode material satisfies: 0.80≤V C / V DBP +V D / G ≤12.60.

[0028] The above parameter V C It can reflect the carbonization degree of the hard carbon negative electrode material, and the specific carbonization degree affects the sodium storage capacity of the hard carbon negative electrode material. D / G Specifically, it is the ratio of the peak area of ​​the characteristic peak D to the peak area of ​​the characteristic peak G in the Raman spectrum of the hard carbon negative electrode material. This ratio can reflect the degree of defects on the surface of the hard carbon material, determine the active sites for embedding and extracting sodium ions, affect the kinetic properties of the hard carbon material, and also affect the overpotential during the charge and discharge process, thereby affecting the capacity of the hard carbon negative electrode material. The above oil absorption value determines the compatibility between the hard carbon negative electrode material and the electrolyte. Generally speaking, the negative electrode material with a higher oil absorption value is more conducive to the electrolyte's infiltration into the negative electrode and the efficient diffusion of active ions in the negative electrode; in addition, the oil absorption value V DBP It is also related to the overpotential of the negative electrode material during the charge and discharge process, which affects the capacity of the hard carbon negative electrode material.

[0029] The inventors of this application have found through a large number of experiments that V C 、V D / G 、V DBPSatisfy 0.80≤V C / V DBP +V D / G When V is less than 12.60, the capacity of the hard carbon negative electrode material is high, and at the same time, it can improve its compatibility with the electrolyte, reduce the diffusion impedance and charge transfer impedance of active ions, and ensure its good kinetic performance, thereby making the sodium ion battery made with the hard carbon negative electrode material have both high capacity and fast charging performance. In this application, the above V C / V DBP +V D / G Specifically, it can be 0.82, 0.85, 0.88, 0.90, 1.00, 1.20, 1.30, 1.50, 2.00, 2.20, 2.50, 2.80, 3.00, 3.50, 3.80, 4.00, 4.10, 4.50, 5.00, 6.00, 7.00, 8.00, 9.00, 10.00, 11.00, 12.00 or 12.50, etc.

[0030] In some embodiments of the present application, 1.0≤V C / V DBP +V D / G ≤10.0. In this case, the hard carbon negative electrode material can better balance high capacity and good kinetic performance. In some embodiments, 1.28≤V C / V DBP +V D / G ≤4.12.

[0031] In the embodiment of the present application, the V C In the range of 20-26. That is, the 2θ value corresponding to the diffraction peak of the (002) crystal plane in the XRD spectrum of the hard carbon negative electrode material is in the range of 20°-26°. C Within this range, the sodium storage capacity of the hard carbon negative electrode material is guaranteed to be high, laying the foundation for its high capacity. C It can be 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25 or 25.5, etc. In some embodiments of the present application, the V C In the range of 22-25. In this case, the carbonization degree of the hard carbon negative electrode material is more appropriate, its sodium storage capacity is higher, its capacity is higher, and its kinetic performance is better.

[0032] In the embodiment of the present application, the V D / G In the range of 0.5-10.0. Among them, V D / GWithin this range, the degree of surface defects of the hard carbon negative electrode material is guaranteed to be appropriate. The appropriate degree of surface defects is beneficial to the dynamic performance of the hard carbon negative electrode material, and will not cause capacity decay due to excessive overpotential during charge and discharge, or reduce the reversible capacity due to excessive defects. Specifically, V D / G It can be 0.60, 0.70, 1.00, 1.50, 2.00, 2.20, 2.30, 2.50, 3.00, 3.20, 3.50, 3.80, 4.00, 5.00, 6.00, 7.00, 8.80, 9.00, 10.00, etc. In some embodiments of the present application, the V D / G In the range of 1.0-3.5, the hard carbon negative electrode material has better capacity, lower irreversible capacity, and improved first coulombic efficiency of the battery.

[0033] In the embodiment of the present application, the V DBP In the range of 10-100. That is, the oil absorption value of the hard carbon negative electrode material is in the range of 10-100mL / 100g. Among them, the oil absorption value of the hard carbon negative electrode material in this range ensures good compatibility with the electrolyte, which is beneficial for the electrolyte to infiltrate the negative electrode containing the hard carbon negative electrode material, promotes the efficient diffusion of active sodium ions in the negative electrode, and the oil absorption value in this range is also more conducive to the hard carbon negative electrode material having a higher first coulomb efficiency, etc. Specifically, V DBP It can be 10, 20, 30, 40, 50, 60, 70, 80, 90, etc. In some embodiments of the present application, the oil absorption value V DBP In the range of 40-80. In this case, it is more conducive to the hard carbon negative electrode material to have both good kinetic performance and high capacity.

[0034] In the present application, when it is necessary to perform the above-mentioned parameter tests on the hard carbon negative electrode material in the negative electrode, the hard carbon negative electrode material can be separated from the negative electrode first, and then the separated negative electrode is placed in an aqueous solution and soaked for 2 days, and ultrasonically treated until the dressing on the negative electrode current collector is completely removed. Then, the obtained dressing solution is subjected to differential centrifugation and washed with water to obtain a crude hard carbon material. Furthermore, the obtained crude hard carbon material is placed in a certain concentration of HCl solution, and stirred or ultrasonically treated to help accelerate the dissolution so as to remove the easily soluble components in the SEI film adhering to the hard carbon material. Subsequently, solid-liquid separation is performed by centrifugation or filtration, and the obtained hard carbon material is dried at 80-100°C to obtain a hard carbon negative electrode material powder that can be tested for physical and chemical properties.

[0035] In this application, the parameter V of the hard carbon negative electrode material is CThe method for obtaining V is as follows: perform XRD testing on the hard carbon negative electrode material to obtain an XRD spectrum; wherein, a Cu target is used as a cathode ray source during the test; during the test, the scanning rate is 10° / min. Single crystal silicon powder (purity ≥ 99.99%) is used as an internal standard substance, and the single crystal silicon powder is crushed with an agate mortar and all passes through a 45μm standard sieve. The position of the (111) peak in the PDF card of the single crystal silicon powder is 28.42°. Then, the 2θ angle value corresponding to the diffraction peak of the (002) crystal plane is found from the obtained XRD spectrum, and V is obtained. C value.

[0036] The parameter V of the above hard carbon negative electrode material D / G The method for obtaining the Raman spectrum of the hard carbon negative electrode material is as follows: the Raman spectrum can be tested by using a Renishaw Invia device with an excitation wavelength of 532 nm and a wave number range of 100 to 4000 cm -1 Then, the peak area I of the characteristic peak D is obtained by integration from the measured Raman spectrum. D and the peak area of ​​characteristic peak G G , calculate I D with I G The above V D / G .

[0037] The above oil absorption value V DBP The method for obtaining the value is as follows: use a measuring cylinder to measure 70 mL of the hard carbon negative electrode material sample and weigh its mass m, place the hard carbon negative electrode material sample with a mass of m in the mixing chamber of the oil absorption value tester S500, and set the torque threshold of the oil absorption value tester to 1.5 Nm, and then add the test oil (specifically linseed oil) to the hard carbon negative electrode material sample in the mixing chamber at a constant speed of 5 mL / min. As the oil absorption of the sample increases, the viscosity of the mixture of the sample and the oil continues to increase. Read the oil absorption value tester to display the oil absorption amount V1 corresponding to the maximum torque of the test sample. 70% of V1 is the volume of oil actually absorbed by the sample. Divide 70% of V1 by the above m to calculate the volume of oil absorbed by the unit mass of the sample, that is, the oil absorption value V of the hard carbon negative electrode material sample is obtained. DBP .

[0038] In the embodiment of the present application, the D50 of the hard carbon negative electrode material is 2μm-20μm. A suitable particle size D50 can ensure that the specific surface area of ​​the hard carbon negative electrode material is appropriate, which is conducive to the embedding / de-embedding of active ions therein, making its own electrochemical kinetic performance more suitable, and is conducive to the negative electrode maintaining a high compaction density. The D50 refers to the particle size corresponding to when the cumulative volume percentage of the hard carbon negative electrode material particles reaches 50%. The D50 can be obtained by performing a laser particle size analysis test on the hard carbon negative electrode material. The specific test method refers to GB / T 19077-2016 / ISO13320:2009 particle size distribution laser diffraction method.

[0039] In an embodiment of the present application, the hard carbon negative electrode material can be obtained by carbonizing a carbon precursor material, wherein the carbon precursor material can include, but is not limited to, one or more of resin, anthracite, asphalt, and biomass. The biomass can be at least one of coconut shell, rice husk, starch, sucrose, bamboo, polysaccharide, and straw.

[0040] For example, a method for preparing the above-mentioned hard carbon negative electrode material may include the following steps: (1) heating a carbon precursor material to a temperature within a range of 200-500°C in an air-tight atmosphere for pre-carbonization treatment to obtain a pre-carbonized material; (2) crushing the pre-carbonized material and then performing an acid wash treatment; (3) drying the acid-washed material, heating it to a temperature within a range of 1000-1400°C at a heating rate of 50°C / min in a nitrogen atmosphere, keeping the temperature for 10 hours, then cooling it, screening it, and demagnetizing it to obtain a hard carbon negative electrode material. The acid wash temperature may be 80-100°C, and hydrochloric acid may be used as the main acid wash reagent (the weight percentage may be in the range of 20-32%). The drying may be performed within the range of 80-100°C.

[0041] Among them, the carbonization degree parameter V of the hard carbon negative electrode material is C and parameter V D / G The above parameters V of the hard carbon negative electrode material can be controlled by adjusting the type of carbon precursor material, carbonization process and other process conditions. D / G The oil absorption value V of the hard carbon anode material can be regulated by adjusting the process conditions such as the type of carbon precursor material, pre-carbonization temperature, carbonization temperature and holding time; and can also be regulated by further surface modification and / or surface coating of the obtained hard carbon anode material. DBP The regulation can be achieved by adjusting the particle size, specific surface area, and whether the hard carbon negative electrode material is coated.

[0042] As shown in Figure 3, the embodiment of the present application further provides a negative electrode 20, which includes the above-mentioned hard carbon negative electrode material provided in the embodiment of the present application. Generally, the negative electrode includes a negative electrode current collector 201 and a negative electrode active material layer 202 provided on at least one side of the surface of the negative electrode current collector. The negative electrode active material layer includes the above-mentioned hard carbon negative electrode material, a binder, and an optional conductive agent. Since the negative electrode uses the above-mentioned hard carbon negative electrode material provided in the present application as the negative electrode active material, the negative electrode can be used to provide a sodium ion battery with both fast charging performance and high energy density.

[0043] Wherein, the above-mentioned binder and conductive agent are materials well known to those skilled in the art. For example, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyacrylate (such as polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, etc.), polyolefin (such as polypropylene, polyethylene, etc.), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), sodium alginate, etc. One or more, but not limited to this. The conductive agent may be each selected from one or more of conductive carbon black (such as acetylene black, Ketjen black, Supper P, 350G carbon black, etc.), furnace black, carbon fiber, carbon nanotubes, graphene, etc., but not limited to this. In addition, the negative electrode current collector may include but not be limited to copper foil, aluminum foil, copper alloy foil, aluminum alloy foil, carbon-coated copper foil, carbon-coated aluminum foil, copper-plated film or aluminum-plated film, etc.

[0044] As shown in FIG4 , the present invention also provides a sodium ion battery 10, which includes the negative electrode 20 of the present invention. The sodium ion battery 10 has good fast charging performance, high charge density, and good safety performance.

[0045] In the present application, the sodium ion battery 10 may be a liquid battery using a liquid electrolyte, a semi-solid battery using a semi-solid electrolyte, or a solid battery using a solid electrolyte.

[0046] In some embodiments, a liquid battery may include a positive electrode, a negative electrode, and a separator and an electrolyte disposed between the positive electrode and the negative electrode.

[0047] In other embodiments, a semi-solid-state battery may include a positive electrode, a negative electrode, and a semi-solid-state electrolyte disposed between the positive electrode and the negative electrode. In still other embodiments, a solid-state battery may include a positive electrode, a negative electrode, and a solid-state electrolyte disposed between the positive electrode and the negative electrode.

[0048] Similar to the negative electrode structure, the positive electrode 30 generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a binder, and an optional conductive agent. Positive electrode active materials suitable for sodium-ion batteries may include, but are not limited to, one or more of layered sodium transition metal oxides, Prussian blue-based materials, Prussian white-based materials, and polyanion-based materials (such as Na₃V(PO₃)₃N, Na₃V2(PO₄)₃, and NaFePO₄).

[0049] As shown in FIG5 , an embodiment of the present application further provides a device 100 comprising the sodium-ion battery 10 of the embodiment of the present application. The device may be a vehicle (e.g., automobile, motorcycle, bicycle, etc.), an electric toy, a consumer electronics product (e.g., a mobile phone, laptop, tablet computer, pen-type computer, e-book player, wearable device, etc.), or an energy storage system. The device may have a long operating time and a fast charging speed when powered by the lithium battery.

[0050] The technical solutions of the embodiments of the present application are further described below with reference to a number of embodiments.

[0051] Example 1

[0052] Preparation of a hard carbon negative electrode material:

[0053] (1) The carbon precursor material is heated to a temperature within the range of 200-500°C in an air-tight atmosphere for pre-carbonization treatment to obtain a pre-carbonized material; (2) The pre-carbonized material is crushed and then pickled at 80-100°C using hydrochloric acid as the main pickling agent (the weight percentage range can be 20-32%); (3) The pickled material is dried at 80-100°C, and then heated to 1000-1400°C at a heating rate of 50°C / min in a nitrogen atmosphere for carbonization. After the heat treatment for 10 hours, the material is cooled, and the hard carbon negative electrode material is obtained after screening and demagnetization.

[0054] By adjusting the process conditions such as the type of carbon precursor material, pre-carbonization temperature, carbonization temperature, and holding time, a hard carbon negative electrode material that meets the requirements shown in Table 1 is obtained. The hard carbon negative electrode material can be prepared into a negative electrode and a sodium ion battery.

[0055] Among them, the preparation of the negative electrode for sodium ion battery includes: mixing the hard carbon negative electrode material of Example 1 shown in Table 1 with a conductive agent (specifically conductive carbon black Super p), a binder CMC, and a binder SBR in a mass ratio of 93:2:2:3, stirring the mixed powder with deionized water to prepare a negative electrode slurry; uniformly coating the negative electrode slurry on an aluminum foil current collector, and drying it to form a surface density of 80m 2 / g of negative electrode active material layer.

[0056] A preparation method for a sodium ion full battery comprises:

[0057] 1) Preparation of positive electrode sheet: The positive electrode active material - sodium nickel iron manganese oxide (chemical formula is NaNi 0.33 Fe 0.33 Mn 0.34 O2) is mixed with a conductive agent carbon nanotube and a binder PVDF in a mass ratio of 97:1:2, and the resulting mixed powder is stirred with a solvent N-methylpyrrolidone (NMP) in a homogenizer to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on an aluminum foil and dried to form a positive electrode active material layer.

[0058] 2) Preparing an electrolyte: Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; fluoroethylene carbonate (FEC) is added at a volume equivalent to 1 wt% of the mixed solvent, and a certain amount of sodium hexafluorophosphate (NaPF6) is added as an electrolyte sodium salt to prepare the desired electrolyte. The concentration of NaPF6 in the electrolyte is 1.0 mol / L.

[0059] 3) Assembly of a sodium-ion full battery: The positive electrode sheet, polypropylene separator, and negative electrode are stacked in order, placed in an outer aluminum-plastic film, and injected with the above-mentioned electrolyte. After vacuum packaging, standing, formation, and capacity division, a laminated soft-pack full battery with a rated capacity of 1.2Ah is prepared.

[0060] A sodium ion button half-cell is prepared, comprising: cutting the aforementioned negative electrode into discs with a diameter of 13 μm to obtain a disc with hard carbon; stacking a sodium disc with a diameter of 18 mm and a thickness of 0.50 mm, a glass fiber battery filter paper separator, and the disc with hard carbon in sequence, placing the disc in a button-shaped stainless steel casing, injecting the electrolyte described in step 2), and encapsulating the casing to obtain a button half-cell. The sodium disc serves as the "negative electrode" of the button half-cell, and the electrode with hard carbon serves as the "positive electrode" of the button half-cell.

[0061] The charge and discharge test method for the button half-cell includes: placing the assembled button half-cell in a constant temperature test cabinet at 25°C for 12 hours and then conducting a charge and discharge test. The test process is as follows: first, discharging at a constant current of 0.05mA to 0.0V, then discharging at a constant voltage of 0.0V until the current drops to 10μA, and then the discharge is completed, completing the sodium insertion process of the hard carbon; after 30 minutes of storage, the charge test (i.e., sodium removal) is performed, charging at a constant current of 0.10mA to 2.5V; recording the first sodium insertion capacity and the first sodium removal capacity, respectively, in mAh. Among them, the first coulombic efficiency of the button half-cell = first sodium removal capacity / first sodium insertion capacity × 100%; the gram capacity of the negative electrode hard carbon material is equal to the ratio of the first sodium removal capacity to the mass of the hard carbon material in the electrode, in units of mAh / g.

[0062] Electrochemical performance test of the above full battery:

[0063] First, the capacity of each full battery was constant, specifically including: in a constant temperature test cabinet at 25°C, the sodium ion full battery was charged to 4.0V at a constant current and constant voltage of 0.20C, and then charged at a constant voltage to a cutoff current of 0.05C, recorded as the charging capacity C1; then discharged at a constant current of 0.20C to a voltage of 2.0V, recorded as the discharge capacity C2.

[0064] Among them, the test method for charge rate performance is: in a constant temperature test cabinet at 25℃, charge the sodium ion full battery with a discharge capacity of C2 to 4.0V at a constant current of 2C, and record the charge capacity at this time as C3; then the charge rate performance of 2.00C is: C3 / C1*100%.

[0065] The test method for discharge rate performance is as follows: in a 25°C constant temperature test cabinet, the fully charged sodium ion battery whose capacity has reached C1 in the above capacity determination step is discharged to 2.0V at a constant current of 2.00C, and the discharge capacity at this time is recorded as C4; the 2C discharge rate performance is: C4 / C2*100%.

[0066] Examples 2-15 and Comparative Examples 1-2

[0067] According to Table 1, the hard carbon negative electrode materials required for Examples 2-15 and Comparative Examples 1-2 were provided. Based on the method described in Example 1, these materials were prepared into sodium ion button cells and full cells, respectively. The relevant electrochemical performance tests were conducted, and the results are summarized in Table 2. Figures 1 and 2 provide the XRD and Raman spectra of the hard carbon negative electrode materials used in Example 3 of the present application, respectively.

[0068] Table 1

[0069] Table 2

[0070] By comparing the test results of the batteries of Examples 1-15 and Comparative Examples 1-2, it can be seen that the (V C / V DBP +V D / G ) value is controlled between 0.80-12.60, and the electrochemical performance of the button battery made by using it is better overall, among which the first sodium removal gram capacity can be maintained above 245mAh / g, the first coulombic efficiency of the button is above 80%, the discharge capacity retention rate at 2C discharge rate is above 90%, and the charging capacity retention rate at 2C charge rate is mostly above 90%. Overall, the electrochemical performance of the button battery of the embodiment of the present application is better than that of the button battery using (V C / V DBP +V D / G ) value is not within the range of 0.80-12.60. This shows that the present invention satisfies the requirement of 0.80≤V by controlling the hard carbon negative electrode material. C / V DBP +V D / G ≤12.60, which can better balance its sodium storage capacity and kinetic performance, so that the sodium ion battery has a higher energy density and better rate performance.

[0071] In addition, it can be seen from the comparison between Example 14 and the aforementioned Examples 1-12 that when (V C / V DBP +V D / G ) is within the range of 0.80-12.60, if V D / G When the ratio is within the range of 0.50-10.00, it is more conducive to the sodium ion battery having good rate performance. From the comparison between Example 13 and the above-mentioned Examples 1-12, it can be seen that when (V C / V DBP +V D / G ) is within the range of 0.80-12.60, if V DBP When the range is 10.00-100.00, it is more conducive to the sodium ion battery having a higher first coulombic efficiency. From the comparison between Example 15 and the above-mentioned Examples 1-12, it can be seen that when (V C / V DBP +V D / G ) is in the range of 0.80-12.60, if Vc is in the range of 20-26 and V D / G When it is in the range of 0.50-10.00, it is more conducive to the sodium ion battery having a higher gram capacity and first coulombic efficiency.

[0072] The above description is of exemplary embodiments of the present application, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, and such modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A hard carbon negative electrode material, characterized in that, The 2θ value corresponding to the diffraction peak of the (002) crystal plane in the XRD pattern of the hard carbon negative electrode material is V C °; in the Raman spectrum of the hard carbon negative electrode material, I D / I G is V D / G , and the oil absorption value of the hard carbon negative electrode material is V DBP mL / 100g; Among them, the hard carbon negative electrode material satisfies: 0.8 ≤ V C / V DBP +V D / G ≤ 12.

6.

2. The hard carbon negative electrode material according to claim 1, characterized in that, The said V C is in the range of 20 - 26.

3. The hard carbon negative electrode material according to claim 1 or 2, characterized in that The said V D / G is in the range of 0.5 - 10.

0.

4. The hard carbon negative electrode material according to any one of claims 1 to 3, characterized in that, The said V DBP is in the range of 10 - 100.

5. The hard carbon negative electrode material according to any one of claims 1-4, characterized in that, 1.0 ≤ V C / V DBP + V D / G ≤ 10.0。 6. The hard carbon negative electrode material according to any one of claims 1-5, characterized in that, 1.28 ≤ V C / V DBP + V D / G ≤ 4.12 7. The hard carbon negative electrode material according to any one of claims 1-6, characterized in that, Said V C is in the range of 22 - 25.

8. The hard carbon negative electrode material according to any one of claims 1-7, characterized in that Said V D / G is in the range of 1.0 - 3.

5.

9. The hard carbon negative electrode material according to any one of claims 1-8, characterized in that, The said V DBP is in the range of 40 - 80.

10. The hard carbon negative electrode material according to any one of claims 1-9, characterized in that, The D50 of the hard carbon negative electrode material is 2 μm - 20 μm.

11. A negative electrode (20), characterized in that, The negative electrode (20) includes the hard carbon negative electrode material according to any one of claims 1 - 10.

12. A sodium ion battery (10), the sodium ion battery (10) includes the negative electrode (20) according to claim 11, and a positive electrode (30).

13. An apparatus (100) comprising a sodium ion battery (10) as claimed in claim 12, wherein, The device (100) is an electrical equipment or an energy storage system.

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