Nitrogen-doping-regulated coal pitch-based potassium ion battery negative electrode material and preparation method thereof

Abstract

The invention relates to a nitrogen-doping-regulated coal pitch-based potassium ion battery negative electrode material which is prepared by the following steps: S1, uniformly mixing coal pitch and triazole to obtain a precursor mixture; s2, putting the precursor mixture in the step S1 into a high-pressure reaction kettle, carrying out nitrogen doping-carbonization integrated treatment in an inert atmosphere by adopting a sand bath furnace in a manner of sweeping, blowing and heating at the same time, and cooling to obtain a primary carbonized product needle coke; s3, putting the primary carbonization product in the step S2 into a tubular furnace, and performing secondary carbonization in an inert protective gas atmosphere to obtain a secondary carbonization product; and S4, carrying out hydrochloric acid cleaning, solid-liquid separation and drying treatment on the secondary carbonization product in the step S3 to obtain the nitrogen-doping-regulated coal pitch-based potassium ion battery negative electrode material. The invention provides a feasible thought for preparing the potassium ion battery negative electrode material which is low in cost, large in scale and good in electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal ion battery negative electrode materials, and particularly relates to a nitrogen-doped coal pitch-based potassium ion battery negative electrode material and a preparation method thereof. BACKGROUND

[0002] There is an increasing demand for sustainable and large-scale energy storage systems. Lithium-ion batteries (LiB) are widely used due to their high energy density, long cycle life and extremely low self-discharge rate. However, as the renewable energy system continues to develop, the resource limitation problem of lithium batteries gradually emerges, so it is urgent to strengthen the in-depth research on post-lithium ion battery technology. Potassium ion batteries (KIB) have attracted much attention in recent years. The abundance of potassium element on earth and low cost make it show significant advantages in large-scale energy storage applications. However, due to its larger size radius, potassium ions will cause significant distortion to the structure of the material during the process of embedding and de-embedding the electrode material, and even may cause the collapse of the structure. This change in structure will directly affect the performance of potassium ion batteries. Therefore, in order to overcome this difficulty, it is essential to research and develop new high-performance electrode materials suitable for potassium ion batteries, so that they can play a greater role in the field of energy storage.

[0003] As the core negative electrode material of new energy storage devices such as potassium ion batteries, hard carbon has great application potential in the field of new energy storage due to its highly adjustable pore structure and excellent electrochemical stability, especially in solving the problem of volume expansion of high-capacity electrode materials. At present, the hard carbon materials applied to potassium ion batteries mainly include biomass-based hard carbon, polymer-based hard carbon and coal-based hard carbon. Biomass-based hard carbon, such as materials prepared by using coconut shell, wood chips, straw and the like as precursors, although it is widely available and low in cost, but the disorder of its structure leads to too large specific surface area, resulting in high irreversible capacity, and the irregular distribution of ion transmission channels makes the potassium ion diffusion efficiency low; polymer-based hard carbon, such as phenolic resin-based hard carbon, although it can control the microstructure through molecular design, but the high-temperature carbonization in the preparation process is easy to cause structure shrinkage, forming a dense carbon layer, which hinders the embedding and de-embedding of potassium ions, and the intrinsic conductivity of the material itself is poor; coal-based hard carbon has complex raw material composition, and the impurity content is high after carbonization, which not only affects the electronic conduction of the material, but also easily causes side reactions, reduces the cycle life of the battery, and becomes the key bottleneck restricting its application. Therefore, it is urgent to provide a nitrogen-doped coal pitch-based potassium ion battery negative electrode material and a preparation method thereof. SUMMARY

[0004] OBJECTIVE The present application is to solve the problems of the prior art, to promote the further development of potassium ion battery technology, the present application proposes a kind of nitrogen-doped regulation coal pitch-based potassium ion battery negative material and preparation method thereof.The prepared material is suitable as the negative electrode of potassium ion battery, with excellent electrochemical performance, providing a new idea for the design of high-performance potassium ion battery negative material.

[0005] To achieve the above object, the present application provides the following technical scheme: A preparation method of nitrogen-doped regulation coal pitch-based potassium ion battery negative material, comprising the following steps: S1: uniformly mix coal pitch and triazole to obtain a precursor mixture; S2: place the precursor mixture in step S1 in a high-pressure reaction kettle, and perform nitrogen-doping-carbonization integrated treatment under inert atmosphere by using sand bath furnace edge scanning blowing heating method, and obtain needle coke after cooling as primary carbonization product; S3: place the primary carbonization product in step S2 in a tube furnace, and perform secondary carbonization under inert protective gas atmosphere to obtain secondary carbonization product; S4: wash the secondary carbonization product in step S3 with hydrochloric acid, perform solid-liquid separation and drying treatment to obtain nitrogen-doped regulation coal pitch-based potassium ion battery negative material.

[0006] As a further description of the above scheme, in step S1, the amount of triazole added is 5%-30% of the mass of coal pitch.

[0007] As a further description of the above scheme, in step S2, the inert atmosphere is nitrogen atmosphere; the pressure in the high-pressure reaction kettle is maintained at 0.1-0.3 MPa; the sand bath furnace is provided with a barrel-shaped cavity, and the high-pressure reaction kettle is placed in the barrel-shaped cavity, and the edge scanning blowing heating is realized by blowing the hot sand at the bottom of the sand bath furnace upward through a blower; the carbonization temperature of the nitrogen-doping-carbonization integrated treatment is 400-500°C, and the holding time is 6-8h; the cooling is to take out the high-pressure reaction kettle and cool it to room temperature in normal temperature water.

[0008] As a further description of the above scheme, in step S3, the inert protective gas is argon; the heating rate of the secondary carbonization is 5-10°C / min, the carbonization temperature is 800-1200°C, and the holding time is 2-3h.

[0009] As a further description of the above scheme, in step S4, the acid solution used for pickling is a mixed solution prepared by mixing deionized water and hydrochloric acid with a concentration of 35%-40% at a volume ratio of 33:7; the solid-liquid separation is performed by suction filtration under a pressure of-0.10 MPa; the drying treatment uses a vacuum oven, and the drying temperature is 80-105°C, and the drying time is 8-12h.

[0010] An apparatus for implementing the above preparation method, comprising a reaction kettle, a sand bath furnace, a nitrogen supply pipeline, a blower, a thermocouple, a first safety valve, a second safety valve, a back pressure valve, a first pressure monitoring instrument, a second pressure monitoring instrument, a separation container and a gas meter, The sand bath furnace has a barrel-shaped cavity, and the reaction kettle is coaxially arranged in the barrel-shaped cavity of the sand bath furnace; The blower is arranged outside the sand bath furnace, and the air outlet end of the blower penetrates the bottom of the sand bath furnace and extends into the sand bath furnace, for blowing the hot sand at the bottom of the sand bath furnace upward; One end of the nitrogen supply pipeline is connected to an external nitrogen source, the other end of the nitrogen supply pipeline is communicated with the gas inlet at the top of the reaction kettle, and a second safety valve is arranged on the nitrogen supply pipeline; The detection end of the thermocouple is inserted into the inside of the reaction kettle for measuring the reaction temperature inside the reaction kettle; The gas outlet end of the reaction kettle is connected with an exhaust pipeline, the first safety valve is installed on the exhaust pipeline, and the second safety valve is installed on the nitrogen supply pipeline; The first pressure monitoring instrument and the second pressure monitoring instrument are respectively installed on the side wall of the reaction kettle and the exhaust pipeline; The gas inlet of the separation container is communicated with the exhaust pipeline through a pipeline; The gas meter is connected in series in the downstream pipeline of the gas outlet end of the separation container, and the back pressure valve is arranged on the downstream pipeline of the gas outlet end of the separation container.

[0011] A nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material is prepared by the above preparation method, the negative electrode material is a nitrogen-doped porous carbon structure, and is suitable for being used as a negative electrode of a potassium ion battery; under a current density of 0.1 A / g, the reversible discharge specific capacity of the potassium ion battery half-cell cycle of the nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material is ≥ 139 mAh / g after 100 cycles.

[0012] A potassium ion battery negative electrode sheet comprises the above-mentioned nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material, a conductive agent and a binder, and the mass ratio of the nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material, the conductive agent and the binder is 8:1:1; the conductive agent is acetylene black, and the binder is sodium carboxymethyl cellulose.

[0013] A potassium ion battery comprises the above-mentioned negative electrode sheet, a positive electrode sheet, a separator and an electrolyte; the electrolyte takes potassium hexafluorophosphate as a solute, and the electrolyte takes ethylene carbonate and diethyl carbonate as solvents in a volume ratio of 1:1. Advantages and effects of the present application: By using coal tar pitch as the basis of potassium ion battery negative electrode material, and combining with triazole doping, the electrochemical performance of the negative electrode material is significantly improved. In terms of preparation method, the coal tar pitch is mixed with triazole, and a unique nitrogen-doping-carbonization integrated and secondary carbonization process is adopted, which is parameter-precise and controllable, reduces the cost, and improves the preparation efficiency; in terms of equipment matching, through the design of sand bath furnace edge sweeping and heating, multi-pressure and temperature monitoring, etc., the stability and safety of the reaction are ensured. Coal tar pitch has rich pore structure and high carbon content, providing a good place for the insertion and extraction of potassium ions. The introduction of triazole further enhances the electrical conductivity and structural stability of the negative electrode material through the interaction between the nitrogen atoms and carbon atoms contained therein, making the battery exhibit more excellent performance during charging and discharging. The discharge specific capacity of CP-10% after 100 cycles is 139.2 mAh / g, which is much higher than the discharge specific capacity of 92.46 mAh / g of the undoped comparative example 1. In addition, the shape of the 2nd and 3rd charging and discharging curves is more similar to the first one, indicating that after the first charging and discharging, the electrochemical reversibility of the material is improved, and the insertion and extraction process of potassium ions is more stable and regular in subsequent cycles. The negative electrode sheet, potassium ion battery composed of the material, and the reasonable conductive agent, binder and electrolyte further optimize the overall performance of the battery, which has great potential in improving energy density and prolonging service life, and provides a highly competitive solution for the commercial application of potassium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The basic flow chart of the preparation method of the nitrogen-doped and regulated coal tar pitch-based potassium ion battery negative electrode material of the embodiment of the present application is shown in the figure. Figure 2 The optical property diagram of the nitrogen-doped and regulated coal tar pitch-based potassium ion battery negative electrode material of the embodiment of the present application is shown in the figure. Figure 3 The cycle performance test results of the half-cell assembled by the prepared potassium ion carbon negative electrode material at a current density of 100 mA / g are shown in the figure. Figure 4 The charge-discharge curve diagram of the half-cell assembled by the prepared potassium ion carbon negative electrode material at a current density of 100 mA / g is shown in the figure.

[0015] The figure mark is explained as follows: 1-first safety valve, 2-exhaust pipe, 3-second safety valve, 4-nitrogen supply pipe, 5-reaction kettle, 6-sand bath furnace, 7-blower, 8-first pressure monitoring instrument, 9-thermocouple, 10-second pressure monitoring instrument, 11-back pressure valve, 12-gas meter, 13-separation container. DETAILED DESCRIPTION

[0016] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0017] In the following examples, the instrument information used is as follows: New Wei test system: manufacturer: Shenzhen New Will Electronics Co., Ltd., model: CT-4008T.

[0018] Glove box: manufacturer: Microna (China) Co., Ltd., model: Upure1220.

[0019] Tube furnace: manufacturer: Hefei Kexing Material Technology Co., Ltd., model: GSL-1600X.

[0020] Vacuum drying oven: manufacturer: Hefei Jingke Tianmei Scientific Instrument Co., Ltd., model: DZF-6020.

[0021] Button cell packaging machine: manufacturer: Shenzhen Kexing Co., Ltd., model: MSK-110.

[0022] A preparation method of a nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material, comprising the following steps: S1: uniformly mixing coal tar pitch and triazole to obtain a precursor mixture; S2: placing the precursor mixture in step S1 in a high-pressure reaction kettle, and performing nitrogen-doping-carbonization integrated treatment under inert atmosphere by using a sand bath furnace heating method with scanning and blowing, to obtain a primary carbonization product after cooling; S3: placing the primary carbonization product in step S2 in a tube furnace, and performing secondary carbonization under inert protective gas atmosphere to obtain a secondary carbonization product; S4: washing, solid-liquid separation and drying treatment of the secondary carbonization product in step S3 with hydrochloric acid to obtain a nitrogen-doped coal tar pitch-based potassium ion battery negative electrode material.

[0023] In step S1 of the present application, the addition amount of triazole is 5%-30% of the mass of coal tar pitch.

[0024] In step S2 of the present application, the inert atmosphere is a nitrogen atmosphere; the pressure in the high-pressure reactor is maintained at 0.1-0.3 MPa; the sand bath furnace is provided with a barrel-shaped cavity, and the high-pressure reactor is placed in the barrel-shaped cavity; the heating by blowing is achieved by blowing hot sand at the bottom of the sand bath furnace upward by a blower; the carbonization temperature of the nitrogen-doped-carbon integrated treatment is 400-500 DEG C, and the holding time is 6-8 h; and the cooling is achieved by taking out the high-pressure reactor and placing it in normal temperature water to cool to room temperature. The present application does not need a separate nitrogen-doping step, and simultaneously realizes nitrogen doping during carbonization at 400-500 DEG C, which simplifies the process and reduces the cost; in addition, the present application accommodates the reactor in the barrel-shaped cavity of the sand bath furnace, and cooperates with the blower to blow the hot sand at the bottom upward to realize the heating by blowing, avoids local overheating, ensures the stability of the temperature in the reactor, and provides a guarantee for the uniformity of carbonization and nitrogen doping; the cooperation of pressure and cooling: the pressure of 0.1-0.3 MPa can maintain the effective concentration of nitrogen source in the reaction system, and avoid the premature escape of nitrogen atoms; after the reaction, the reactor is placed in normal temperature water to cool to room temperature, which can quickly fix the porous structure of the primary carbonization product, and no abnormal structure shrinkage occurs.

[0025] In step S3 of the present application, the inert protective gas is argon; the heating rate of the secondary carbonization is 5-10 DEG C / min, the carbonization temperature is 800-1200 DEG C, and the holding time is 2-3 h. The present design can realize the directional arrangement of carbon molecules, and obtain nitrogen-doped porous carbon with excellent conductivity.

[0026] In step S4 of the present application, the acid solution used for pickling is a mixed solution prepared by mixing deionized water and hydrochloric acid with a concentration of 35%-40% at a volume ratio of 33:7; the solid-liquid separation is carried out by suction filtration under a pressure of-0.10 MPa; and the drying treatment adopts a vacuum oven, the drying temperature is 80-105 DEG C, and the drying time is 8-12 h. The acid solution prepared by mixing deionized water and 35%-40% hydrochloric acid at a ratio of 33:7 is used for cleaning in the present application, which can remove impurity ions in the secondary carbonization product, such as metal impurities remaining in coal tar pitch, cooperates with suction filtration under a pressure of-0.10 MPa, and can efficiently separate solid and liquid to avoid the influence of impurity residues on the battery performance; at the same time, vacuum drying at 80-105 DEG C can completely remove water, and the vacuum environment avoids material oxidation, and no capacity fluctuation caused by improper drying occurs in the electrochemical test.

[0027] The device for preparing the above-mentioned nitrogen-doped regulated coal pitch-based potassium ion battery negative electrode material comprises a reaction kettle 5, a sand bath furnace 6, a nitrogen supply pipeline 4, a blower 7, a thermocouple 9, a first safety valve 1, a second safety valve 3, a back pressure valve 11, a first pressure monitoring instrument 8, a second pressure monitoring instrument 10, a separation container 13 and a gas meter 12, and the connection relationship and functions of the components are as follows: the sand bath furnace 6 is integrally formed with a barrel-shaped cavity, the reaction kettle 5 is arranged in the barrel-shaped cavity of the sand bath furnace 6, and the reaction kettle 5 is a core container for coal pitch tar reaction; the air outlet end of the blower 7 penetrates through the bottom of the sand bath furnace 6 and extends into the sand bath furnace 6, and is used for blowing the hot sand at the bottom of the sand bath furnace 6 upward to realize side sweeping and blowing and side heating of the reaction kettle 5, one end of the nitrogen supply pipeline 4 is connected with an external nitrogen source, and is used for introducing nitrogen into the reaction kettle 5 to build an inert atmosphere and prevent unnecessary reactions from occurring during the preparation of acicular coke; the other end of the nitrogen supply pipeline 4 is in communication with the gas inlet at the top of the reaction kettle 5, and the second safety valve 3 is arranged on the nitrogen supply pipeline 4, the detection end of the thermocouple 9 is inserted into the inside of the reaction kettle 5, and is used for accurately measuring the reaction temperature in the inside of the reaction kettle 5 to ensure that the reaction is carried out at a required temperature; the gas outlet end of the reaction kettle 5 is connected with an exhaust pipeline 2, the first safety valve 1 is fixedly installed on the exhaust pipeline 2, the second safety valve is installed on the nitrogen supply pipeline 4, and the first safety valve 1 and the second safety valve 3 are both used for opening pressure relief when the pressure in the system exceeds a preset safety value to avoid equipment damage or accidents; the gas meter 12 is connected in series in a downstream pipeline of the gas outlet end of the separation container 13, and the back pressure valve 11 is arranged on the downstream pipeline of the gas outlet end of the separation container 13, and is used for adjusting the gas pressure to a suitable level of about 0.2 MPa suitable for the metering of the gas meter 12 to ensure the stable operation of downstream equipment; the first pressure monitoring instrument 8 and the second pressure monitoring instrument 10 are respectively installed on the side wall of the reaction kettle 5 and the exhaust pipeline 2, and are used for monitoring the pressure in the system in real time to assist in controlling the reaction conditions; the gas inlet of the separation container 13 is in communication with the exhaust pipeline 2 through a pipeline, and is used for separating and purifying the gas generated by the reaction kettle 5 to remove gas impurities and separate different components; and the gas meter 12 is connected in series in the downstream pipeline of the gas outlet end of the separation container 13, and is used for accurately recording the amount of gas passing through to provide data support for process control, product quantification and cost accounting.

[0028] A nitrogen-doped regulated coal pitch-based potassium ion battery negative electrode material is prepared by the above-mentioned preparation method, the negative electrode material is a nitrogen-doped porous carbon structure, and is suitable for being used as a negative electrode of a potassium ion battery; under a current density of 0.1 A / g, the reversible discharge specific capacity of the potassium ion battery half-cell cycle of the potassium ion battery negative electrode material is greater than or equal to 139 mAh / g after 100 cycles.

[0029] The present invention provides a potassium-ion battery negative electrode sheet, comprising the above-mentioned nitrogen-doped coal tar pitch-based potassium-ion battery negative electrode material, a conductive agent, and a binder, wherein the mass ratio of the nitrogen-doped coal tar pitch-based potassium-ion battery negative electrode material, the conductive agent, and the binder is 8:1:1; the conductive agent is acetylene black, and the binder is sodium carboxymethyl cellulose.

[0030] The present invention provides a potassium-ion battery comprising the aforementioned negative electrode, positive electrode, separator, and electrolyte; wherein the electrolyte uses potassium hexafluorophosphate as a solute and ethylene carbonate and diethyl carbonate in a volume ratio of 1:1 as solvents.

[0031] Example 1 4g of coal tar pitch and 0.2g of triazole were uniformly mixed to obtain a solid powder. The solid powder was filled into a glass liner tube, then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to replace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.1MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to 490℃. The reactor was quickly placed in the sand bath furnace for heating. When the reactor reached 400℃, the timer was started for 6 hours. The reactor was then removed and rapidly cooled in room temperature water. After cooling to room temperature, the black solid was removed, which is the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in a tube furnace filled with argon at a temperature of 800℃, with a heating rate of 5℃ / min and a holding time of 3 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (the volume ratio of deionized water to hydrochloric acid with a concentration of 35%-40% was 33:7), filtered under a pressure of -0.10 MPa, and finally kept in a vacuum oven at a temperature of 80-105°C for 8-12 hours to obtain the final porous carbon material.

[0032] Example 2 4g of coal tar pitch and 0.4g of triazole were uniformly mixed to obtain a solid powder. The solid powder was filled into a glass liner tube, then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to replace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.3MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to 490℃. The reactor was quickly placed in the sand bath furnace for heating. When the reactor reached 475℃, the timer was started for 6 hours. The reactor was then removed and rapidly cooled in room temperature water. After cooling to room temperature, the black solid was removed, which is the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in a tube furnace filled with argon at a temperature of 1000℃, a heating rate of 8℃ / min, and a holding time of 2.5 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (deionized water and 35%-40% hydrochloric acid were mixed at a volume ratio of 33:7) and filtered under a pressure of -0.10 MPa. Finally, the porous carbon material was obtained by holding it in a vacuum oven at a temperature of 80-105°C for 8-12 hours.

[0033] Example 3 4g of coal tar pitch and 0.6g of triazole were uniformly mixed to obtain a solid powder. The solid powder was filled into a glass liner tube, then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to replace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.2MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to be maintained at 490℃. The reactor was quickly placed in the sand bath furnace for heating. When the reactor reached 500℃, the timer was started for 6 hours. The reactor was then removed and placed in room temperature water for rapid cooling. After cooling to room temperature, the black solid was removed, which is the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in a tube furnace filled with argon at a temperature of 1200℃, a heating rate of 6℃ / min, and a holding time of 3 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (the volume ratio of deionized water to hydrochloric acid with a concentration of 35%-40% was 33:7), filtered under a pressure of -0.10 MPa, and finally kept in a vacuum oven at a temperature of 80-105°C for 8-12 hours to obtain the final porous carbon material.

[0034] Example 4 4g of coal tar pitch and 0.8g of triazole were uniformly mixed to obtain a solid powder. The solid powder was filled into a glass liner tube, then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to replace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.2MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to 490℃. The reactor was quickly placed in the sand bath furnace for heating. When the reactor reached 475℃, the timer was started for 7 hours. The reactor was then removed and rapidly cooled in room temperature water. After cooling to room temperature, the black solid was removed, which is the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in a tube furnace filled with argon at a temperature of 1100℃, a heating rate of 10℃ / min, and a holding time of 2 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (the volume ratio of deionized water to hydrochloric acid with a concentration of 35%-40% was 33:7), filtered under a pressure of -0.10 MPa, and finally kept in a vacuum oven at a temperature of 80-105°C for 8-12 hours to obtain the final porous carbon material.

[0035] Example 5 4g of coal tar pitch and 1.2g of triazole were uniformly mixed to obtain a solid powder. The solid powder was filled into a glass liner tube, then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to replace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.2MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to 490℃. The reactor was quickly placed in the sand bath furnace for heating. When the reactor reached 475℃, the timer was started for 8 hours. The reactor was then removed and rapidly cooled in room temperature water. After cooling to room temperature, the black solid was removed, which is the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in a tube furnace filled with argon at a temperature of 900℃, a heating rate of 5℃ / min, and a holding time of 2 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (the volume ratio of deionized water to hydrochloric acid with a concentration of 35%-40% was 33:7), filtered under a pressure of -0.10 MPa, and finally kept in a vacuum oven at a temperature of 80-105°C for 8-12 hours to obtain the final porous carbon material.

[0036] Comparative Example 1 4g of coal tar pitch was filled into a glass liner tube, which was then placed in a high-pressure reactor, and the gaps were tightly sealed with graphite paper. Nitrogen was used to purge the reactor to displace the air inside, followed by pressurization with nitrogen. The pressure inside the reactor was maintained at 0.2MPa by adjusting the back pressure valve. The temperature of the sand bath furnace was adjusted to 490℃. The reactor was quickly placed in the sand bath furnace for heating, and a 6-hour timer was started after the reactor reached 475℃. The reactor was then removed and rapidly cooled in room temperature water. After cooling to room temperature, the black solid was removed, which was the needle coke product. Further, the obtained needle coke product was subjected to a second carbonization in an argon-filled tubular furnace at 1000℃, with a heating rate of 5℃ / min and a holding time of 2 hours. The product obtained from the second carbonization process was sequentially washed with hydrochloric acid (the volume ratio of deionized water to hydrochloric acid with a concentration of 35%-40% was 33:7), filtered under a pressure of -0.10 MPa, and finally kept in a vacuum oven at a temperature of 80-105°C for 8-12 hours to obtain the final porous carbon material.

[0037] The porous carbon materials obtained in each embodiment were mixed with acetylene black and sodium carboxymethyl cellulose in a ratio of 8:1:1, and an appropriate amount of deionized water was added as a solvent. The mixture was continuously stirred to obtain a slurry with a certain degree of fluidity. Then, a 100µm coater was used to evenly coat the slurry onto the surface of the current collector. Finally, the coated battery cells were placed in a vacuum oven and dried at 105°C for 12 hours. During battery assembly, potassium hexafluorophosphate (KPF6) was used as the solute, and ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 were used as the solvent. The electrochemical performance of the potassium-ion battery was tested on a Newway testing system at a current density of 100 mA / g. The test showed that when the amount of triazole added was 10% of the mass of coal tar pitch (labeled as CP-10%), the discharge specific capacity after 100 cycles was 139.2 mAh / g, which is significantly higher than the discharge specific capacity of CP in Comparative Example 1 (92.46 mAh / g). The second and third charge-discharge curves are more similar in shape to the first one, indicating that the electrochemical reversibility of the material is significantly improved after the first charge-discharge.

[0038] In summary, this study used coal tar pitch as the substrate for potassium-ion battery anode materials and employed triazole doping modification to significantly improve the electrochemical performance of the anode material. Coal tar pitch itself has a well-developed porous structure and a high carbon content, which creates excellent spatial conditions for the insertion and extraction of potassium ions. The addition of triazole, through the interaction between its nitrogen and carbon atoms, further enhances the conductivity and structural stability of the anode material, thereby allowing the battery to exhibit superior performance during charge-discharge cycles.

[0039] Figure 1 This is a basic flowchart of the preparation method of nitrogen-doped coal tar pitch-based potassium-ion battery anode material according to an embodiment of the present invention. Each equipment unit is connected by pipelines, enabling continuous processing of raw materials and effective collection of products. The sand bath, as a heating medium, has a large heat capacity and uniform temperature distribution, which can stabilize the temperature inside the reactor, providing a controllable and uniform thermal environment for the reaction.

[0040] Figure 2 Figures a and f illustrate the optical properties of the material. Figure a shows the optical properties of coal tar pitch; Figure b shows the addition of triazole at 5% of the coal tar pitch mass; Figure c shows the addition of triazole at 10% of the coal tar pitch mass; Figure d shows the addition of triazole at 15% of the coal tar pitch mass; Figure e shows the addition of triazole at 20% of the coal tar pitch mass; and Figure f shows the addition of triazole at 30% of the coal tar pitch mass. The material without nitrogen doping exhibits a significant fibrous structure, while with the addition of nitrogen, the material gradually exhibits a coarse-grained and even plate-like morphology. This indicates a better orientation of the molecular arrangement, providing a more suitable structural basis for potassium ion insertion or extraction, and no structural collapse or disordering problems due to improper doping were observed.

[0041] Figure 3 The graph shows the cycling performance of CP and CP-10% at a current density of 0.1 A / g. The discharge specific capacity of CP-10% after 100 cycles is 139.2 mAh / g, which is much higher than the discharge specific capacity of CP in Comparative Example 1 (92.46 mAh / g).

[0042] Figure 4 The chart shows the charge-discharge voltage curves of CP-10% at a current density of 0.1 A / g. The curves for the second and third cycles almost overlap, demonstrating the good reversibility of charge-discharge and excellent cycle stability of this material. Compared with the first cycle, the voltage performance in subsequent cycles is stable in the high specific capacity region, which is beneficial to improving the battery energy density and operational stability, providing strong support for practical applications.

[0043] This application significantly improves the electrochemical performance of potassium-ion battery anode materials by using coal tar pitch as the base material and combining it with triazole doping. In terms of preparation method, an innovative approach is adopted, mixing coal tar pitch and triazole, and employing a unique integrated nitrogen doping-carbonization and secondary carbonization process with precisely controllable parameters, reducing costs and improving preparation efficiency. Regarding equipment, a sand bath furnace with simultaneous blowing and heating, and multi-pressure and temperature monitoring are designed to ensure stable and safe reaction. Coal tar pitch possesses a rich porous structure and high carbon content, providing excellent sites for potassium ion insertion and extraction. The introduction of triazole, through the interaction between its nitrogen and carbon atoms, further enhances the conductivity and structural stability of the anode material, resulting in superior battery performance during charge and discharge. The discharge specific capacity of CP-10% after 100 cycles is 139.2 mAh / g, far exceeding the discharge specific capacity of 92.46 mAh / g of the undoped CP in Comparative Example 1. Furthermore, the second and third charge-discharge curves are more similar in shape to the first, indicating that the electrochemical reversibility of the material is improved after the first charge-discharge cycle. In subsequent cycles, the insertion and extraction of potassium ions are more stable and regular. The negative electrode and potassium-ion battery composed of this material, combined with appropriate conductive agents, binders, and electrolytes, further optimize the overall battery performance, showing great potential in improving energy density and extending lifespan, providing a highly competitive solution for the commercial application of potassium-ion batteries.

[0044] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped coal tar pitch-based potassium-ion battery anode material, characterized in that, Includes the following steps: S1: Mix coal tar pitch and triazole evenly to obtain a precursor mixture; S2: The precursor mixture described in step S1 is placed in a high-pressure reactor and subjected to nitrogen doping-carbonization integrated treatment by a sand bath furnace with simultaneous blowing and heating under an inert atmosphere. After cooling, needle coke, a primary carbonization product, is obtained. S3: Place the primary carbonization product described in step S2 into a tube furnace and perform secondary carbonization under an inert protective gas atmosphere to obtain the secondary carbonization product. S4: The secondary carbonization product described in step S3 is washed with hydrochloric acid, separated into solid and liquid phases, and dried to obtain a nitrogen-doped coal tar pitch-based potassium-ion battery anode material.

2. The preparation method according to claim 1, characterized in that, In step S1, the amount of triazole added is 5%-30% of the mass of coal tar pitch.

3. The preparation method according to claim 1, characterized in that, In step S2, the inert atmosphere is a nitrogen atmosphere; the pressure inside the high-pressure reactor is maintained at 0.1-0.3 MPa; the sand bath furnace has a barrel-shaped cavity, and the high-pressure reactor is placed inside the barrel-shaped cavity. Heating is achieved by blowing hot sand from the bottom of the sand bath furnace upwards using a blower while sweeping and blowing; the carbonization temperature of the nitrogen-doped carbonization integrated treatment is 400-500℃, and the holding time is 6-8h; the cooling is achieved by removing the high-pressure reactor and placing it in room temperature water to cool it to room temperature.

4. The preparation method according to claim 1, characterized in that, In step S3, the inert protective gas is argon; the heating rate of the secondary carbonization is 5-10℃ / min, the carbonization temperature is 800-1200℃, and the holding time is 2-3h.

5. The preparation method according to claim 1, characterized in that, In step S4, the acid solution used for pickling is a mixed solution of deionized water and hydrochloric acid with a concentration of 35%-40% at a volume ratio of 33:7; the solid-liquid separation is carried out by vacuum filtration under a pressure of -0.10MPa; the drying treatment is carried out in a vacuum oven at a drying temperature of 80-105℃ for 8-12 hours.

6. An apparatus for carrying out the preparation method according to any one of claims 1-5, characterized in that, It includes a reaction vessel (5), a sand bath furnace (6), a nitrogen supply pipeline (4), a blower (7), a thermocouple (9), a first safety valve (1), a second safety valve (3), a back pressure valve (11), a first pressure monitoring instrument (8), a second pressure monitoring instrument (10), a separation container (13), and a gas meter (12). The sand bath furnace (6) has a barrel-shaped cavity, and the reaction vessel (5) is placed inside the barrel-shaped cavity of the sand bath furnace (6); The blower (7) is located on the outside of the sand bath furnace (6), and the air outlet of the blower (7) penetrates the bottom of the sand bath furnace (6) and extends into the sand bath furnace (6) to blow the hot sand at the bottom of the sand bath furnace (6) upward. One end of the nitrogen supply pipe (4) is connected to an external nitrogen source, and the other end of the nitrogen supply pipe (4) is connected to the air inlet at the top of the reactor (5). A second safety valve (3) is provided on the nitrogen supply pipe (4). The probe end of the thermocouple (9) is inserted into the reactor (5) to measure the reaction temperature inside the reactor (5); The gas outlet of the reactor (5) is connected to an exhaust pipe (2), the first safety valve (1) is installed on the exhaust pipe (2), and the second safety valve (3) is installed on the nitrogen supply pipe (4). The first pressure monitoring instrument (8) and the second pressure monitoring instrument (10) are respectively installed on the side wall of the reactor (5) and the exhaust pipe (2); The air inlet of the separation container (13) is connected to the exhaust pipe (2) through a pipe; The gas meter (12) is connected in series in the downstream pipe of the gas outlet of the separation container (13), and the back pressure valve (11) is installed on the downstream pipe of the gas outlet of the separation container (13).

7. A nitrogen-doped coal tar pitch-based potassium-ion battery anode material, characterized in that, The anode material is prepared by any one of the preparation methods described in claims 1-5. The anode material is a nitrogen-doped porous carbon structure and is suitable as a negative electrode for potassium-ion batteries. At a current density of 0.1 A / g, the reversible discharge specific capacity of the potassium-ion battery half-cell assembled from the nitrogen-doped coal tar pitch-based potassium-ion battery anode material is ≥139 mAh / g after 100 cycles.

8. A negative electrode sheet for a potassium-ion battery, characterized in that, The material includes the nitrogen-doped coal tar pitch-based potassium-ion battery anode material, conductive agent, and binder as described in claim 7, wherein the mass ratio of the nitrogen-doped coal tar pitch-based potassium-ion battery anode material, conductive agent, and binder is 8:1:1; the conductive agent is acetylene black, and the binder is sodium carboxymethyl cellulose.

9. A potassium-ion battery, characterized in that, It includes the negative electrode, positive electrode, separator, and electrolyte as described in claim 8; the electrolyte uses potassium hexafluorophosphate as the solute and ethylene carbonate and diethyl carbonate in a volume ratio of 1:1 as the solvent.

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