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

Abstract

The invention provides a hard carbon negative electrode material. A 2theta value VC corresponding to a diffraction peak of a (002) crystal face in an XRD spectrogram, an ID / IG value VD / G of a Raman spectrum and an oil absorption value VDBP (measured by mL / 100g) meet the following conditions: VC / VDBP + VD / G is greater than or equal to 0.8 and less than or equal to 12.60. Therefore, the hard carbon negative electrode material can be ensured to have good dynamic performance and high capacity exerting performance at the same time. The invention also provides a negative electrode adopting the hard carbon negative electrode material, a sodium ion battery and a device.

Description

Technical Field

[0001] This application relates to the technical field of sodium-ion batteries, and particularly to a hard carbon negative electrode material, a negative electrode, a sodium-ion battery and a device. Background Art

[0002] The global lithium resources are scarce and the prices are at a high level, which restricts the development of lithium-ion batteries. The market has begun to seek alternative solutions for lithium-ion batteries. Since the energy storage principle of sodium-ion batteries is basically the same as that of lithium-ion batteries, and the reserves of sodium resources are abundant, sodium-ion batteries are more promising to meet the low-cost requirements for large-scale energy storage devices in the future.

[0003] Currently, the hard carbon material is widely used as the negative electrode active material in sodium-ion batteries. With the increasing requirements for the comprehensive performance of sodium-ion batteries, higher requirements are correspondingly put forward for the hard carbon negative electrode material. However, the hard carbon negative electrode material used in current sodium-ion batteries cannot make the sodium-ion battery have both a high energy density and good fast charging performance. Summary of the Invention

[0004] In view of this, this application provides a hard carbon negative electrode material. By defining that a certain relationship is satisfied among multiple parameters of the hard carbon negative electrode material, it can be ensured that the hard carbon negative electrode material can have both a high capacity performance and good kinetic performance, and further make the sodium-ion battery prepared with this hard carbon negative electrode material have both a high energy density and fast charging performance.

[0005] Specifically, in the first aspect of this application, a hard carbon negative electrode material is provided. 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 I D / I G value in the Raman spectrum of the hard carbon negative electrode material is V D / G , and 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.

[0006] When the above parameters V C , V D / G , V DBP of the hard carbon negative electrode material satisfy the above relational expression and the defined range, its kinetic performance is good and the capacity performance is high, which is beneficial to preparing a sodium-ion battery with both a high energy density and fast charging performance.

[0007] The second aspect of the present application provides a negative electrode, which includes the hard carbon negative electrode material described in the first aspect of the present application. Since the negative electrode contains the above-mentioned hard carbon negative electrode material, the negative electrode can be used to provide a sodium ion battery that takes into account both fast charging performance and high energy density.

[0008] The third aspect of the present application provides a sodium ion battery, including the negative electrode described in the first aspect of the present application and a positive electrode. The sodium ion battery has good fast charging performance and relatively high energy density.

[0009] The fourth aspect of the present application provides a device with the sodium ion battery described in the third aspect of the present application, and the device is an electrical equipment or an energy storage system. Description of the Drawings

[0010] Figure 1 It is the XRD spectrum of the hard carbon negative electrode material of Example 3 of the present application.

[0011] Figure 2 It is the Raman spectrum of the hard carbon negative electrode material of Example 3 of the present application. Detailed Embodiments

[0012] The embodiments of the present application provide a hard carbon negative electrode material that can endow a sodium ion battery with both relatively high energy density and fast charging performance.

[0013] Specifically, the embodiments of the present application provide a hard carbon negative electrode material. 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 I D / I G value in the Raman spectrum of the hard carbon negative electrode material is V D / G , and 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.

[0014] The above parameter V C 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. The above V D / GSpecifically, it is the ratio of the peak area of the characteristic peak D peak to the peak area of the characteristic peak G peak 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 site situation for the insertion and extraction of sodium ions, affect the kinetic performance of the hard carbon material, and also affect the overpotential during the charge and discharge process, thereby affecting the capacity performance of the hard carbon negative electrode material. The above-mentioned oil absorption value determines the compatibility between the hard carbon negative electrode material and the electrolyte. Generally speaking, the higher the oil absorption value of the negative electrode material, the more conducive it is to the infiltration of the electrolyte into the negative electrode and the efficient diffusion of active ions in the negative electrode; in addition, the oil absorption value V DBP is also related to the overpotential during the charge and discharge process of the negative electrode material, affecting the capacity performance of the hard carbon negative electrode material.

[0015] However, through a large number of experiments, the inventors of this application found that when V C 、V D / G 、V DBP satisfies 0.80 ≤ V C / V DBP + V D / G ≤ 12.60, the hard carbon negative electrode material has a high capacity performance. At the same time, it can improve its compatibility with the electrolyte, reduce the diffusion impedance and charge transfer impedance of active ions, ensure good kinetic performance, and thus enable the sodium-ion battery prepared with this hard carbon negative electrode material to achieve both high capacity performance and fast charging performance. In this application, the above-mentioned V C / V DBP + V D / G can specifically 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. In some embodiments of this application, 1.0 ≤ V C / V DBP + V D / G ≤ 10.0. In this case, the above-mentioned hard carbon negative electrode material can better balance high capacity performance and good kinetic performance. In some embodiments, 1.28 ≤ V C / V DBP + V D / G ≤ 4.12.

[0016] In the embodiments of this application, the V C is in the range of 20 - 26. That is, 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 in the range of 20° - 26°. Among them, V CWithin this range, it is more conducive to ensuring that the hard carbon anode material has a relatively high sodium storage capacity, laying a foundation for the high-capacity performance thereof. Specifically, V C can be 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, etc. In some embodiments of the present application, the V C is within the range of 22 - 25. In this case, the carbonization degree of the hard carbon anode material is more appropriate, its sodium storage capacity is higher, the capacity performance is higher, and at the same time, the kinetic performance is relatively good.

[0017] In the embodiments of the present application, the V D / G is within the range of 0.5 - 10.0. Among them, when V D / G is within this range, it is more conducive to ensuring that the degree of defects on the surface of the hard carbon anode material is appropriate, which is beneficial for it to exhibit good dynamic performance and will not cause the overpotential during charge and discharge to be too large, reducing its capacity performance, or the reversible capacity to decrease due to excessive defects. Specifically, V D / G 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 is within the range of 1.0 - 3.5. In this case, the capacity performance of the hard carbon anode material is better, the irreversible capacity is lower, and the first Coulombic efficiency of the battery is improved.

[0018] In the embodiments of the present application, the V DBP is within the range of 10 - 100. That is, the oil absorption value of the hard carbon anode material is within the range of 10 - 100 mL / 100 g. Among them, when the oil absorption value of the hard carbon anode material is within this range, it is more conducive to ensuring good compatibility between it and the electrolyte, thereby facilitating the electrolyte to infiltrate the anode containing the hard carbon anode material, promoting the efficient diffusion of active sodium ions in the anode, and the oil absorption value within this range is also more conducive to the hard carbon anode material having a relatively high first Coulombic efficiency, etc. Specifically, V DBP 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 is within the range of 40 - 80. In this case, it is more conducive for the hard carbon anode material to balance good kinetic performance and relatively high capacity performance.

[0019] In this application, when it is necessary to test the above parameters of the hard carbon anode material in the anode, the hard carbon anode material can be first separated from the anode, and then the separated anode is immersed in an aqueous solution for 2 days and ultrasonically treated until the dressing on the anode current collector completely falls off. Then, the obtained dressing solution is subjected to differential centrifugation and washed with water to obtain a crude hard carbon material. Further, the obtained crude hard carbon material is placed in an HCl solution with a certain concentration and dissolved by stirring or ultrasonic treatment to help accelerate the dissolution and remove the dissolved components in the SEI film adhered to the hard carbon material. Subsequently, solid-liquid separation is carried out by centrifugation or filtration, and the obtained hard carbon material is dried at 80-100 °C to obtain a hard carbon anode material powder that can be used for physical and chemical property tests.

[0020] In this application, the parameter V of the above hard carbon anode material C is obtained by: performing XRD testing on the hard carbon anode material to obtain an XRD spectrum; among them, a Cu target is used as the cathode ray source during the testing; during the testing process, the scanning rate is 10° / min. Single crystal silicon powder (purity ≥ 99.99%) is used as the internal standard substance, and the single crystal silicon powder is pulverized with an agate mortar and all passes through a 45 μm 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, that is, the value of V C is obtained.

[0021] The parameter V of the above hard carbon anode material D / G is obtained by: performing Raman spectroscopy testing on the hard carbon anode material. Specifically, a Renishaw Invia device can be used for the testing, the excitation wavelength is 532 nm, and the wavenumber range is 100-4000 cm -1 . Then, the peak area I D of the characteristic peak D peak and the peak area I G of the characteristic peak G peak are obtained by integration from the measured Raman spectrum, and the ratio of I D to I G is calculated to obtain the above V D / G .

[0022] The above oil absorption value V DBPThe method for obtaining is as follows: Measure 70 mL of the hard carbon anode material sample with a measuring cylinder and weigh its mass m. Place the hard carbon anode material sample with mass 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. Then add the test oil (specifically linseed oil) to the hard carbon anode 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 continuously increases. Read the oil absorption volume V1 corresponding to the maximum torque of the test sample shown on the oil absorption value test instrument. 70% of V1 is the actual volume of oil absorbed by the sample. Divide 70% of V1 by the above m to calculate the volume of oil absorbed by the sample per unit mass, that is, obtain the oil absorption value V of the hard carbon anode material sample. DBP 。

[0023] In the embodiment of the present application, the D50 of the hard carbon anode material is 2 μm - 20 μm. A suitable particle size D50 can ensure a suitable specific surface area of the hard carbon anode material, which is beneficial to the insertion / extraction of active ions therein, making its own electrochemical kinetic performance more suitable, and is beneficial to the anode maintaining a high tap density. Among them, the D50 refers to the particle size corresponding to when the cumulative volume percentage of the hard carbon anode material particles reaches 50%. The D50 can be obtained by performing laser particle size analysis and testing on the hard carbon anode material. The specific testing method refers to the laser diffraction method for particle size distribution in GB / T 19077 - 2016 / ISO13320:2009.

[0024] In the embodiment of the present application, the hard carbon anode material can be obtained by carbonizing a carbon precursor material. Among them, the carbon precursor material can include, but is not limited to, one or more of resin, anthracite, asphalt, and biomass. Among them, the biomass can be at least one of coconut shell, rice husk, starch, sucrose, bamboo, polysaccharide, and straw.

[0025] Exemplarily, a preparation method of the above hard carbon anode material may include the following steps: (1) Heat the carbon precursor material in an airtight atmosphere to 200 - 500 °C for pre-carbonization treatment to obtain pre-carbonized material; (2) Crush the pre-carbonized material and then perform pickling treatment; (3) After drying the pickled material, heat it to 1000 - 1400 °C at a heating rate of 50 °C / min in a nitrogen atmosphere, keep it warm for 10 h and then cool down, and obtain the hard carbon anode material after sieving and demagnetization. Among them, the temperature of the pickling can be 80 - 100 °C, and hydrochloric acid is used as the main pickling reagent (the weight percentage range can be 20 - 32%). The drying can be carried out in the range of 80 - 100 °C.

[0026] Among them, the above carbonization degree parameter V of the hard carbon anode material C and parameter VD / G It can be regulated by controlling process conditions such as the type of carbon precursor material and carbonization process. Among them, the above parameter V of the hard carbon negative electrode material D / G It can be regulated by controlling process conditions such as the type of carbon precursor material, the temperature of pre-carbonization, the carbonization temperature and the heat preservation time; it can also be regulated by further surface modification and / or surface coating of the obtained hard carbon negative electrode material. Among them, the above oil absorption value V of the hard carbon negative electrode material DBP It can be regulated by controlling the particle size, specific surface area, and whether to coat of the hard carbon negative electrode material.

[0027] The embodiment of the present application also provides a negative electrode, which includes the above-mentioned hard carbon negative electrode material provided by the embodiment of the present application. Generally, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one 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 by 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.

[0028] Among them, the above-mentioned binder and conductive agent are both materials well-known to those skilled in the art. Exemplarily, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyacrylate (such as polymethyl methacrylate, polyacrylate methyl, polyacrylate ethyl, etc.), polyolefin (such as polypropylene, polyethylene, etc.), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), sodium alginate, etc., but not limited thereto. The conductive agent can be 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 nanotube, graphene, etc., but not limited thereto. In addition, the negative electrode current collector may include, but is not limited to, copper foil, aluminum foil, copper alloy foil, aluminum alloy foil, carbon-coated copper foil, carbon-coated aluminum foil, copper-coated film or aluminum-coated film, etc.

[0029] The embodiment of the present application also provides a sodium ion battery, which includes the above-mentioned negative electrode of the embodiment of the present application. The sodium ion battery has good fast charging performance, high energy density and good safety performance.

[0030] In this application, the sodium-ion battery can be a liquid battery using a liquid electrolyte, a semi-solid battery using a semi-solid electrolyte, or a solid-state electrolyte using a solid electrolyte. In some embodiments, the liquid battery can include a positive electrode, a negative electrode, and a separator and an electrolyte disposed between the positive electrode and the negative electrode. In other embodiments, the secondary semi-solid battery can include a positive electrode, a negative electrode, and a semi-solid electrolyte disposed between the positive electrode and the negative electrode. In still other embodiments, the solid-state battery can include a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode.

[0031] Similar to the structure of the negative electrode, the positive electrode 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. Among them, the positive electrode active materials suitable for sodium-ion batteries can include, but are not limited to, one or more of layered sodium transition metal oxides, Prussian blue materials, Prussian white materials, polyanion materials (such as Na3V(PO3)3N, Na3V2(PO4)3, NaFePO4, etc.).

[0032] The embodiments of this application also provide a device, which includes the above-mentioned sodium-ion battery of the embodiments of this application. The above-mentioned device can be an electric device such as a vehicle (such as a car, a motorcycle, a bicycle, etc.), an electric toy, a 3C product (such as a mobile phone, a laptop computer, a tablet computer, a pen input computer, an e-book player, a wearable device, etc.); or it can be an energy storage system, etc. Among them, the electric devices powered by the above-mentioned lithium battery have a long running time and a fast charging speed.

[0033] The technical solutions of the embodiments of this application will be further described below in multiple embodiments.

[0034] Embodiment 1

[0035] Preparation of a hard carbon negative electrode material:

[0036] (1) Heat the carbon precursor material in an airtight atmosphere to 200-500 °C for pre-carbonization treatment to obtain pre-carbonized material; (2) After pulverizing the pre-carbonized material, use hydrochloric acid as the main pickling reagent (the weight percentage range can be 20-32%) to perform pickling treatment on it at 80-100 °C; (3) After drying the pickled material at 80-100 °C, heat it to 1000-1400 °C at a heating rate of 50 °C / min in a nitrogen atmosphere for carbonization, keep it warm for 10 h and then cool it down, and obtain the hard carbon negative electrode material after screening and demagnetization.

[0037] By controlling process conditions such as the type of carbon precursor material, pre-carbonization temperature, carbonization temperature, and heat preservation time, a hard carbon negative electrode material that can meet the requirements shown in Table 1 is obtained. This hard carbon negative electrode material can be fabricated into a negative electrode and a sodium-ion battery.

[0038] Among them, the preparation of the negative electrode for a 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 obtain a negative electrode slurry; uniformly coating the negative electrode slurry on an aluminum foil current collector and drying to form a negative electrode active material layer with a surface density of 80 m 2 / g.

[0039] The preparation of a sodium-ion full battery includes:

[0040] 1) Preparation of the positive electrode sheet: Mixing the positive electrode active material - sodium nickel iron manganese oxide (chemical formula: NaNi 0.33 Fe 0.33 Mn 0.34 O2) with a conductive agent carbon nanotube and a binder PVDF in a mass ratio of 97:1:2, stirring the resulting mixed powder with a solvent N-methylpyrrolidone (NMP) in a homogenizer to make a positive electrode slurry; uniformly coating the positive electrode slurry on aluminum foil and drying to form a positive electrode active material layer.

[0041] 2) Preparation of the electrolyte: Mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 to obtain a mixed solvent; adding fluoroethylene carbonate (FEC) with a volume of 1 wt% of the volume of this mixed solvent, and adding a certain amount of sodium hexafluorophosphate (NaPF6) as the electrolyte sodium salt to make the required electrolyte. Among them, the concentration of NaPF6 in this electrolyte is 1.0 mol / L.

[0042] 3) Assembly of the sodium-ion full battery: Stacking the above positive electrode sheet, polypropylene separator, and negative electrode in sequence, placing them in an outer packaging aluminum-plastic film, and injecting the above electrolyte, and preparing a laminated soft-pack full battery with a rated capacity of 1.2 Ah through processes such as vacuum packaging, standing, formation, and grading.

[0043] The preparation of a sodium-ion coin-type half battery includes: cutting the above negative electrode into a circular sheet with a diameter of 13 μm to obtain a circular sheet with hard carbon; stacking a sodium sheet with a diameter of 18 mm and a thickness of 0.50 mm, a glass fiber battery filter paper separator, and the above circular sheet with hard carbon in sequence, placing them in a coin-type stainless steel shell, and injecting the electrolyte in 2) above, and obtaining a coin-type half battery after encapsulation. Among them, this sodium sheet serves as the "negative electrode" of this coin-type half battery, and the electrode sheet with hard carbon serves as the "positive electrode" of this coin-type half battery.

[0044] Among them, the charge-discharge test method for the button half-cell includes: in a constant-temperature test cabinet at 25°C, after the assembled button half-cell is left standing for 12 h, a charge-discharge test is carried out. The test process is as follows: first, a constant-current discharge is carried out at a current of 0.05 mA until 0.0 V, then a constant-voltage discharge is carried out at 0.0 V until the current drops to 10 μA, and the discharge ends, completing the sodiation process of the hard carbon; after standing for 30 min, the charging test (i.e., desodiation) is carried out, and a constant-current charge is carried out at a current of 0.10 mA until 2.5 V; the first sodiation capacity and the first desodiation capacity are recorded respectively, and the units are mAh. Among them, the first Coulomb efficiency of the button half-cell = the first desodiation capacity / the first sodiation capacity × 100%; the specific capacity of the negative hard carbon material is equal to the ratio of the first desodiation capacity to the mass of the hard carbon material in the electrode sheet, and the unit is mAh / g.

[0045] The above electrochemical performance test of the full cell:

[0046] First, each full cell is constant-volume, specifically including: in a constant-temperature test cabinet at 25°C, the sodium-ion full cell is charged at a constant current and constant voltage of 0.20 C until 4.0 V, and then charged at a constant voltage until the cut-off current is 0.05 C, which is recorded as the charging capacity C1; then, a constant-current discharge is carried out at 0.20 C until the voltage is 2.0 V, which is recorded as the discharge capacity C2.

[0047] Among them, the test method for the charge rate performance is: in a constant-temperature test cabinet at 25°C, the sodium-ion full cell with a discharge capacity of C2 is charged at a constant current of 2 C until 4.0 V, and the charging capacity at this time is recorded as C3; then the charge rate performance at 2.00 C is: C3 / C1 * 100%.

[0048] Among them, the test method for the discharge rate performance is: in a constant-temperature test cabinet at 25°C, the fully charged sodium-ion full cell with a capacity of C1 in the above constant-volume step is discharged at a constant current of 2.00 C until 2.0 V, and the discharge capacity at this time is recorded as C4; then the discharge rate performance at 2 C is: C4 / C2 * 100%.

[0049] Examples 2-15 and Comparative Examples 1-2

[0050] According to Table 1, the hard carbon negative electrode materials required for Examples 2-15 and Comparative Examples 1-2 are provided, and based on the method described in Example 1, they are respectively prepared into sodium-ion button cells and full cells, and relevant electrochemical performance tests are carried out. The results are summarized in Table 2. Among them, Figure 1 、 Figure 2 The XRD spectrum and Raman spectrum of the hard carbon negative electrode material in Example 3 of the present application are respectively provided.

[0051] Table 1

[0052] Serial number <![CDATA[Degree of carbonization V C > <![CDATA[I D / I G Value V D / G > <![CDATA[Oil absorption value V DBP > <![CDATA[V C / V DBP +V D / G > Example 1 21.05 0.65 85.00 0.90 Example 2 23.39 1.08 56.10 1.50 Example 3 24.08 1.98 75.00 2.30 Example 4 23.78 2.29 95.00 2.54 Example 5 21.30 2.33 52.00 2.74 Example 6 26.00 2.55 62.00 2.97 Example 7 22.60 3.42 65.20 3.77 Example 8 22.18 3.78 82.00 4.05 Example 9 24.55 5.03 50.00 5.52 Example 10 20.32 7.36 15.00 8.71 Example 11 25.62 8.98 28.00 9.90 Example 12 20.20 10.00 11.00 11.84 Example 13 23.25 7.65 120.00 7.84 Example 14 24.27 0.40 40.00 1.01 Example 15 19.89 10.7 13.00 12.23 Comparative example 1 19.57 11.80 9.60 13.84 Comparative example 2 26.50 0.12 57.00 0.59

[0053] Table 2

[0054]

[0055] From the comparison of the test results of the batteries in the above Examples 1-15 and Comparative Examples 1-2, it can be learned that the (V C / V DBP +V D / G ) value of the hard carbon negative electrode material in the examples of this application is controlled between 0.80 and 12.60. The overall electrochemical performance of the button cells made of it is relatively excellent. Among them, the first sodiation specific capacity can remain above 245 mAh / g, the first Coulombic efficiency of charge-discharge is above 80%, the discharge capacity retention rate at 2C discharge rate is above 90%, and the charge capacity retention rate of most of the charge at 2C charge rate is above 90%. Generally speaking, the electrochemical performance of the button cells in the examples of this application is better than that of the comparative example cells made of hard carbon negative electrode materials with (V C / V DBP +V D / G ) values not within 0.80-12.60. This shows that by controlling the hard carbon negative electrode material to meet 0.80≤V C / V DBP +V D / G ≤12.60, its sodium storage capacity and kinetic performance can be better balanced, so that the sodium-ion battery has a higher energy density and better rate performance, etc.

[0056] In addition, from the comparison between Example 14 and the previous Examples 1-12, it can be learned that when (V C / V DBP +V D / G ) is within the range of 0.80-12.60, if V D / G is within the range of 0.50-10.00, it is more beneficial for the sodium-ion battery to have good rate performance. From the comparison between Example 13 and the previous Examples 1-12, it can be learned that when (V C / V DBP +V D / G ) is within the range of 0.80-12.60, if V DBP is in the range of 10.00-100.00, it is more beneficial for the sodium-ion battery to have a higher first Coulombic efficiency. From the comparison between Example 15 and the previous Examples 1-12, it can be learned that when (V C / V DBP +V D / G ) is within the range of 0.80-12.60, if Vc is in the range of 20-26 and V D / GWhen in the range of 0.50 - 10.00, it is more beneficial for the sodium-ion battery to have a higher specific capacity and initial Coulombic efficiency.

[0057] The above are exemplary embodiments of the present application, which are described in more specific and detailed terms, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope 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 1-3, 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 to 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, The 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, characterized in that, The negative electrode includes the hard carbon negative electrode material according to any one of claims 1 - 10.

12. A sodium ion battery, the sodium ion battery includes the negative electrode according to claim 11, and a positive electrode.

13. An apparatus comprising the sodium ion battery according to claim 12, wherein, The device is an electrical equipment or an energy storage system.

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