A defect-rich graphitic carbon cathode material, its preparation method and applications

Abstract

This invention discloses a defect-rich graphite-carbon cathode material, its preparation method, and its application as a cathode material in dual-ion batteries. The graphite cathode material comprises an ordered structural portion and a disordered structural portion. The ordered structural portion consists of short-layer graphite sheets and turbine-layer carbon randomly combined, forming abundant defects. The disordered portion consists of the connecting portions of the short-layer graphite sheets. According to this invention, the graphite cathode material increases the anion storage specific capacity of the carbon cathode by increasing the storage sites in the graphite-carbon material, thereby improving the energy density of the dual-ion battery. Controlling the interlayer spacing of graphite and designing the pore structure of the carbon material can improve the anion storage kinetics, further enhancing the rate performance and cycle stability of the battery. Simultaneously, the preparation conditions of the graphite cathode material are milder and simpler, with lower energy consumption, which helps reduce production costs.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, specifically relating to a defect-rich graphite carbon cathode material and its preparation method, as well as the use of the material as a cathode material for dual-ion batteries. Background Technology

[0002] Dual-ion battery technology is an emerging energy storage technology. Based on the synergistic redox energy storage mechanism of anions and cations, it can achieve high energy density, attracting widespread attention. Dual-ion batteries typically use graphite as the positive electrode, offering advantages such as low cost, environmental friendliness, and easy recyclability. Furthermore, the anion-intercalated graphite positive electrode reaction exhibits typical pseudocapacitive characteristics, thus dual-ion batteries also possess high power density, making them highly promising for short-term, high-frequency energy storage. In dual-ion battery systems, graphite is often used as the positive electrode material, loaded onto a current collector to form the positive electrode. However, traditional graphite positive electrodes, due to their limited storage sites and narrow interlayer spacing, typically exhibit low anion storage capacity and poor cycle stability. This means that dual-ion batteries using graphite as the positive electrode material do not have a competitive advantage in energy density compared to traditional lithium-ion batteries.

[0003] Chinese patent CN114430029A discloses a composite modified graphite material obtained by coating the graphite surface with a chemically inert material. This material can improve the interfacial stability of the graphite cathode, thereby enhancing the electrochemical performance of dual-ion batteries. Furthermore, Chinese patents CN116072818A and CN114975868A, respectively, carbonize petroleum coke and pitch materials at temperatures above 1400 degrees Celsius to obtain graphite cathode materials with a high degree of graphitization. These cathode materials exhibit good rate performance and cycle stability.

[0004] However, the aforementioned existing technologies typically focus on optimizing the rate performance and interface structure of traditional graphite cathodes, without addressing the local microstructure within the graphite material, such as storage sites, interlayer spacing, and pore structure. This fails to fully leverage the capacitive storage potential of carbon materials. Furthermore, the synthesis methods of existing technologies often consume significant energy, and the complex structure of graphite materials leads to more complex processing techniques and higher production costs. Therefore, designing a high-capacity, highly stable carbon cathode material is crucial for the commercialization of dual-ion batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to enhance the anion storage capacity of the cathode by developing a graphitic carbon material with abundant storage sites, thereby improving the energy density of dual-ion batteries. Simultaneously, the disordered structure in the graphitic carbon material can mitigate volume changes during charge and discharge, increasing the cycle stability of the dual-ion battery. Furthermore, the graphitic carbon cathode material of this invention can be synthesized at lower temperatures, simplifying the preparation process and significantly reducing actual production costs.

[0006] According to one aspect of the present invention, an object of the present invention is to provide a graphite cathode material comprising an ordered structural portion and a disordered structural portion, wherein the ordered structural portion is formed by a random combination of short-layer graphite sheets and turbine layer carbon, resulting in abundant defects, and the disordered portion is the connecting portion of the short-layer graphite sheets.

[0007] Preferably, the ordered structure portion in the graphite cathode material refers to the essentially ordered arrangement of carbon atoms in the corresponding region, and diffraction peaks of the graphite (002) crystal plane can be observed in the X-ray diffraction pattern. The disordered structure portion refers to the essentially disordered arrangement of carbon atoms in the corresponding region, and the existence of the disordered carbon atom arrangement region has been confirmed by transmission electron microscopy. In addition, vibrational D bands with disordered carbon atoms appear in the Raman spectrum, and I... D / I G The value is as high as 2.84, indicating that the graphite cathode material contains abundant defect structures.

[0008] According to another aspect of the present invention, another object of the present invention is to provide a method for preparing the graphite cathode material, the method comprising the following steps:

[0009] 1) Dissolve the carbon source and iron salt in water and mix thoroughly;

[0010] 2) The mixed solution obtained in step 1) is dried to obtain the precursor, and then calcined and carbonized under an inert atmosphere;

[0011] 3) After cooling the product obtained in step 2), wash it with acid and deionized water to remove residual metal particles, and then dry it to obtain graphitized carbon cathode material.

[0012] Preferably, the carbon source in step 1) is selected from one or more of glucose, sucrose, and starch, with glucose being the most preferred.

[0013] Preferably, the iron salt in step 1) is selected from one or more of potassium ferricyanide, potassium ferrate, potassium tris(oxalate) and ferric chloride, with potassium ferricyanide being the most preferred.

[0014] Preferably, the molar ratio of the carbon source to the iron salt in step 1) is 10:1 to 0.1:1, more preferably 5:1 to 0.5:1, and even more preferably 3:1 to 1:1.

[0015] Preferably, the carbon source concentration in step 1) is 0.15 mol / L to 0.85 mol / L, and more preferably 0.25 mol / L to 0.55 mol / L.

[0016] Preferably, the iron salt concentration in step 1) is 0.05 mol / L to 0.7 mol / L, and more preferably 0.1 mol / L to 0.25 mol / L.

[0017] Preferably, the drying temperature in step 2) is 60-160℃, and more preferably 80-120℃.

[0018] Preferably, the drying time in step 2) is 8-48 hours, more preferably 18-24 hours.

[0019] Preferably, the roasting and carbonization temperature in step 2) is 500-1000℃, more preferably 700-900℃, more preferably 750-850℃, and even more preferably 800℃.

[0020] Preferably, the roasting and carbonization heating rate in step 2) is 0.5-10℃ / min, more preferably 1-8℃ / min, and more preferably 5℃ / min.

[0021] Preferably, the inert atmosphere in step 2) is selected from a nitrogen atmosphere or an argon atmosphere.

[0022] Preferably, the acid used for washing in step 3) is dilute hydrochloric acid or dilute nitric acid.

[0023] According to another aspect of the invention, another object of the invention is to provide the use of the graphite cathode material as a cathode material for a dual-ion battery.

[0024] According to another aspect of the present invention, another object of the present invention is to provide a dual-ion battery, wherein the dual-ion battery uses the graphite cathode material according to the present invention as the cathode material.

[0025] Beneficial effects

[0026] The graphite cathode material according to the present invention has the following advantages:

[0027] 1. By increasing the storage sites in graphite carbon materials, the anion storage specific capacity of the carbon cathode can be improved, thereby increasing the energy density of the dual-ion battery.

[0028] 2. By controlling the interlayer spacing of graphite and designing the pore structure of carbon materials, the anion storage kinetics can be improved, thereby further enhancing the rate performance and cycle stability of the battery.

[0029] 3. The preparation conditions of the graphite cathode material are milder and simpler, with lower energy consumption, which helps to reduce production costs. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 The images show the XRD patterns of the graphite material synthesized in Example 1 and the commercial graphite material.

[0032] Figure 2 The image shows the Raman spectrum of the graphite carbon material synthesized in Example 1.

[0033] Figure 3 TEM of the synthesized graphite carbon material in Example 1

[0034] Figure 4 The image shows an HRTEM image of the graphite carbon material synthesized in Example 1.

[0035] Figure 5 HRTEM image of commercial graphitic carbon materials.

[0036] Figure 6 The charge-discharge curves are for the graphite carbon cathode-based dual-ion battery synthesized in Example 1.

[0037] Figure 7 The rate performance of the dual-ion battery containing the graphite carbon cathode-based dual-ion battery synthesized in Example 1 is shown.

[0038] Figure 8 The graph shows the cycle performance of the graphite carbon cathode-based dual-ion battery synthesized in Example 1.

[0039] Figure 9 The charge-discharge curves are for the graphite carbon cathode-based dual-ion battery synthesized in Example 2.

[0040] Figure 10 The rate performance of the dual-ion battery containing the graphite carbon cathode-based dual-ion battery synthesized in Example 2 is shown.

[0041] Figure 11 The graph shows the cycle performance of the graphite carbon cathode-based dual-ion battery synthesized in Example 2.

[0042] Figure 12 Rate performance of dual-ion batteries containing commercial graphite carbon cathode bases.

[0043] Figure 13 The charge-discharge curves are for a dual-ion battery containing a commercial graphite carbon cathode.

[0044] Figure 14 The graph shows the cycle performance of a dual-ion battery containing a commercial graphite carbon cathode.

[0045] Figure 15 The charge-discharge curves are for the graphite carbon cathode-based dual-ion battery synthesized in Comparative Example 2.

[0046] Figure 16 The rate performance of the dual-ion battery containing the graphite carbon cathode base synthesized in Comparative Example 2 is shown.

[0047] Figure 17 The graph shows the cycle performance of the graphite carbon cathode-based dual-ion battery synthesized in Comparative Example 2.

[0048] Figure 18 The charge-discharge curves are for the graphite carbon cathode-based dual-ion battery synthesized in Comparative Example 3.

[0049] Figure 19 The rate performance of the dual-ion battery containing the graphite carbon cathode base synthesized in Comparative Example 3 is shown.

[0050] Figure 20 The graph shows the cycle performance of the graphite carbon cathode-based dual-ion battery synthesized in Comparative Example 3. Detailed Implementation

[0051] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0052] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0053] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0054] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0055] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0056] In the preparation of the graphite cathode material according to the present invention, iron salt is used as a reactant. The iron salt simultaneously acts as a graphitization catalyst, activator, and dopant. Specifically, at high temperature, the iron ions in the iron salt are converted into elemental iron, which further reacts with carbon to form Fe3C compound. The compound eventually decomposes to form highly graphitized carbon. Meanwhile, potassium salt reacts with carbon at high temperature to produce CO2, causing some of the original carbon atoms to disappear and form micropores, thereby achieving the purpose of activation and pore formation. In addition, the nitrogen element contained therein can replace the positions of carbon atoms, thereby doping into the interior of the carbon material.

[0057] The iron salt is selected from one or more of potassium ferricyanide, potassium ferrate, and potassium tris(oxalate) ferric salt, preferably potassium ferricyanide.

[0058] In addition, unless otherwise stated, the reagents and solvents disclosed below were purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd. X-ray diffraction (XRD) was performed using a D-MAX 2200VPC X-ray diffractometer; Raman spectroscopy was performed using an inVia Raman spectrometer; and TEM was performed using an F30 transmission electron microscope. Electrochemical tests were performed on a Blue Battery testing system (CT002A).

[0059] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0060] Example 1

[0061] 7 mmol of glucose (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) was used as the carbon source and dissolved in 40 ml of deionized water at a molar ratio of 2:1 with 14 mmol of potassium ferricyanide (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.). After uniform mixing, the mixture was dried in a forced-air oven at 100 °C for 20 h to obtain the precursor. Subsequently, the precursor was placed in a tube furnace and carbonized at 800 °C under an argon atmosphere (heating rate of 5 °C / min). After cooling, the collected sample was washed in dilute acid to remove residual metal particles, thus obtaining the graphite cathode material.

[0062] Figure 1 The XRD spectra of the graphite cathode material prepared in this embodiment and the existing commercial graphite material (KS-6, purchased from Dongguan Kelude Experimental Equipment Technology Co., Ltd.) are shown in the figure. As can be seen from the figure, the graphite cathode material prepared according to this embodiment has good crystallinity, indicating that the graphite cathode material contains an ordered structure, while the relatively broad half-width peak indicates the existence of a disordered structure. Figure 2The image shows the Raman spectrum of the graphite cathode material prepared in this embodiment. Figure 2 It can be seen that graphite cathode materials have abundant disordered carbon atom structures (such as edge defects, heteroatoms, etc.). Figure 3 and Figure 4 The images show transmission electron microscope (TEM) images of the graphite cathode material prepared in this embodiment at low and high magnification, respectively. Figure 4 It can be seen that graphite materials contain both ordered and disordered structures. Notably, the short-layer graphite sheets are curved, indicating that the graphite sheets contain a large number of defects, which may improve the storage capacity of carbon cathodes. Figure 5 The image shows a high-resolution TEM image of commercial graphite material. The graphite sheets in the commercial graphite material exhibit a long-range ordered structure, which further proves the highly ordered arrangement of carbon atoms in commercial graphite.

[0063] Example 2

[0064] Compared with Example 1, this example changes the iron salt to potassium trioxalate, while keeping other conditions unchanged.

[0065] Comparative Example 1

[0066] Commercial graphite materials were used as a comparison. From Figure 1 As can be seen from the XRD pattern, the commercial graphite material has better crystallinity compared to the graphite material prepared in Example 1, indicating less internal disorder (i.e., fewer internal defects). Figure 5 This is a high-magnification transmission electron microscope image, which shows the highly ordered arrangement of carbon atoms in commercial graphite materials.

[0067] Comparative Example 2

[0068] Compared to Example 1, the carbonization temperature was changed to 700°C, while other conditions remained the same.

[0069] Comparative Example 3

[0070] Compared to Example 1, the carbonization temperature was changed to 900°C, while other conditions remained the same.

[0071] Test Example 1

[0072] Electrode preparation: First, the prepared graphite material, Super P conductive agent, and polyvinylidene fluoride binder (PVDF) were uniformly mixed in N-methyl-2-pyrrolidone solvent (purchased from Shanghai Maclean Co., Ltd.) at a mass ratio of 8:1:1. The mixture was then uniformly coated onto aluminum foil using a scraping method, followed by drying in an oven at 80℃ for 12 hours. The resulting material was then cut into 10mm round electrode sheets. The active material loading was 1.2±0.2 mg / cm³. 2 .

[0073] Assembly of dual-ion batteries: In a glove box with water and oxygen content <0.01ppm, graphite, lithium sheet, and glass fiber were used as the positive electrode, negative electrode, and separator, respectively. 100μL of 4mol / L LiPF6 / EMC electrolyte was added to assemble R2032 coin cells.

[0074] Electrochemical testing: The battery needs to be left to stand for 12 hours after assembly. The operating voltage range of the dual-ion battery is 1.5-5.1V. Rate performance was evaluated using charge / discharge tests at current densities of 200, 400, 600, 800, 1000, and 2000 mA / g, and long-term cycle stability was evaluated using a charge / discharge test at a current density of 500 mA / g.

[0075] Figure 6 and Figure 7 The figures show the charge-discharge curves and rate performance test graphs of a dual-ion battery using the graphite cathode material prepared in Example 1. Figure 5 and Figure 6 As can be seen, the prepared graphite cathode material exhibits a storage specific capacity as high as 250 mAh / g at 200 mA / g, and even at a high current density of 2000 mA / g, the specific capacity is only 95 mAh / g, indicating that the prepared graphite cathode material possesses excellent anion storage capacity and good rate performance in dual-ion batteries. Furthermore, after high-current testing, the battery capacity did not decrease, indicating that the graphite carbon cathode material prepared in Example 1 has good reversibility. Figure 8 To obtain the long-cycle curve of a dual-ion battery using the graphite cathode material prepared in Example 1, from... Figure 8 As can be seen, after 100 activation cycles in the early stage, the dual-ion battery showed good capacity retention in the subsequent 700 charge-discharge cycles, with the capacity slowly decaying to 85 mAh / g, which again shows that the graphite cathode material prepared in Example 1 has good structural stability.

[0076] Test Example 2

[0077] Compared with Test Example 1, a dual-ion battery was assembled using the graphite cathode material prepared in Example 2, with other conditions remaining unchanged.

[0078] Figure 9 and Figure 10 The figures show the charge-discharge curves and rate performance of a dual-ion battery containing the graphite cathode from Example 2. Figure 8 and Figure 9The results show that the battery exhibits a specific capacity of up to 210 mAh / g at a low current density of 200 mA / g, indicating its excellent ion storage capability. Furthermore, it can still release 66 mAh / g of capacity even at a high current density of 2000 mA / g, demonstrating good rate performance. Figure 11 The figure shows the cycle test results of the dual-ion battery containing the graphite cathode from Example 2. As can be seen from the figure, the capacity of the battery is 67 mAh / g after 800 cycles, indicating that the graphite cathode prepared in Example 2 also has good cycle stability.

[0079] Test Comparison Example 1

[0080] Compared to Test Example 1, a dual-ion battery was assembled using the commercial graphite cathode material from Comparative Example 1, with all other conditions remaining unchanged. It should be noted that the commercial graphite material has a limited number of defect sites and contributes no capacity in the 1.5-3V voltage range; therefore, the operating voltage of the commercial graphite cathode-based dual-ion battery is 3-5.1V.

[0081] Figure 12 and Figure 13 The images show the charge-discharge curves and rate performance test graphs of a dual-ion battery using commercial graphite cathode material. Figure 12 and Figure 13 As can be seen, the specific capacity of commercial graphite cathode materials is 8 mAh / g at a current density of 200 mA / g, while the specific capacity is only 28 mAh / g at a high current density of 2000 mAh / g. This indicates that the anion storage capacity and rate performance of commercial graphite cathode materials are poor, which is related to the fewer ion storage sites inside and the narrower graphite interlayer spacing and pore structure composition. Figure 14 The cycling curves of a dual-ion battery using commercial graphite cathode material are shown below. Figure 14 As can be seen, the overall capacity of the battery remained good during 800 cycles, but the coulombic efficiency fluctuated significantly, indicating that the commercial graphite cathode underwent a large volume change during the cycle, resulting in repeated rupture and regeneration of the cathode / electrolyte interface. The sudden drop in battery capacity after 710 cycles indicates that the electrode active material detached.

[0082] Test Comparison Example 2

[0083] Compared with Test Example 1, a dual-ion battery was assembled using the graphite cathode material prepared in Comparative Example 2, with other conditions remaining unchanged.

[0084] Figure 15 and Figure 16The figures show the charge-discharge curves and rate performance test graphs of a dual-ion battery using the graphite cathode material prepared in Comparative Example 2. The graphs show that the graphite cathode material prepared in Comparative Example 2 has a specific capacity of 152 mAh / g at 200 mA / g, but only 32 mAh / g at a current density of 2000 mA / g, indicating poor anion storage capacity and rate performance. Furthermore, it was observed that after a high-rate test, the battery capacity was reduced to approximately 70% of its original capacity, indicating poor reversibility of the graphite cathode material prepared in Comparative Example 2. Figure 17 The graph shows its long-cycle performance curve. It can be seen from the graph that the capacity decays rapidly in the first 400 cycles, and the capacity is 53 mAh / g after 800 charge-discharge cycles. This indicates that there are many irreversible sites in its microstructure, which leads to poor electrochemical performance.

[0085] Test Comparison Example 3

[0086] Compared with Test Example 1, a dual-ion battery was assembled using the graphite cathode material prepared in Comparative Example 3, with other conditions remaining unchanged.

[0087] Figure 18 and Figure 19 The figures show the charge-discharge curves and rate performance test graphs of a dual-ion battery using the graphite cathode material prepared in Example 3. The graphs show that the graphite cathode material prepared in Example 3 has a specific capacity of 168 mAh / g at 200 mA / g and a specific capacity of 51 mAh / g at a current density of 2000 mA / g, indicating good anion storage capacity and rate performance. However, from... Figure 20 The long-cycle performance curves show that its cycle performance is still poor. Specifically, the battery capacity decays sharply after 230 cycles, which is similar to the cycle performance of commercial graphite in Comparative Example 1. This indicates that excessive graphitization increases the volumetric strain during the anion intercalation process, which leads to the active material being stripped from the current collector. In addition, the battery capacity is only 46 mAh / g after 800 cycles.

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A graphite cathode material, the graphite cathode material comprising an ordered structure portion and a disordered structure portion, wherein the ordered structure portion is composed of short-layer graphite sheets and turbine layer carbon randomly combined, and the disordered portion is the connecting portion of the short-layer graphite sheets; The ordered structure portion in the graphite cathode material refers to the ordered arrangement of carbon atoms in the corresponding regions, and diffraction peaks of the graphite (002) crystal plane can be observed in the X-ray diffraction pattern. The disordered structure portion refers to the disordered arrangement of carbon atoms in the corresponding regions, and the existence of the disordered carbon atom arrangement region was confirmed by transmission electron microscopy. A vibrational D band with disordered carbon atoms appeared in the Raman spectrum, and I... D / I G The value is 2.84; The preparation method of the graphite cathode material includes the following steps: 1) Dissolve the carbon source and iron salt in water and mix them evenly. The iron salt is selected from one or more of potassium ferricyanide, potassium ferrate, and potassium tris(oxalate) ferric salt. 2) The mixed solution obtained in step 1) is dried to obtain the precursor, and then calcined and carbonized under an inert atmosphere at a temperature of 750-850℃. 3) After cooling the product obtained in step 2), wash it with acid and deionized water to remove residual metal particles, and then dry it to obtain graphitized carbon cathode material.

2. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the carbon source in step 1) is selected from one or more of glucose, sucrose, and starch.

3. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the carbon source in step 1) is glucose.

4. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the iron salt in step 1) is potassium ferricyanide.

5. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the molar ratio of the carbon source to the iron salt in step 1) is 10:1 to 0.1:

1.

6. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the molar ratio of the carbon source to the iron salt in step 1) is 5:1 to 0.5:

1.

7. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the molar ratio of the carbon source to the iron salt in step 1) is 3:1 to 1:

1.

8. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the carbon source concentration in step 1) is from 0.15 mol / L to 0.85 mol / L.

9. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the carbon source concentration in step 1) is 0.25 mol / L to 0.55 mol / L.

10. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the iron salt concentration in step 1) is 0.05 mol / L to 0.7 mol / L.

11. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the iron salt concentration in step 1) is 0.1 mol / L to 0.25 mol / L.

12. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the drying temperature in step 2) is 60-160℃.

13. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the drying temperature in step 2) is 80-120℃.

14. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the drying time in step 2) is 8-48h.

15. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the drying time in step 2) is 18-24h.

16. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the calcination and carbonization temperature in step 2) is 800℃.

17. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the calcination and carbonization heating rate in step 2) is 0.5-10℃ / min.

18. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the calcination and carbonization heating rate in step 2) is 1-8℃ / min.

19. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the calcination and carbonization heating rate in step 2) is 5℃ / min.

20. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the inert atmosphere in step 2) is selected from nitrogen atmosphere or argon atmosphere.

21. The graphite cathode material according to claim 1, characterized in that, In the preparation method of the graphite cathode material, the acid used for washing in step 3) is dilute hydrochloric acid or dilute nitric acid.

22. Use of the graphite cathode material according to any one of claims 1 to 21 as a cathode material for a dual-ion battery.

23. A dual-ion battery, wherein the dual-ion battery uses the graphite cathode material according to any one of claims 1 to 21 as the cathode material.

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