A method for preparing asphalt-based carbon-supported metal composite energy storage materials

Abstract

This invention relates to a method for preparing a pitch-based carbon-supported metal composite energy storage material. The method involves mixing a pitch-based precursor with an etchant and ball milling the mixture, followed by a two-stage heating process to obtain porous carbon with a conical pore structure. Metal salts are then loaded onto the surface of this porous carbon, which is calcined in an ammonia atmosphere to obtain a novel metal / carbon composite energy storage material with a nanochannel structure on its surface. This invention employs a two-step heating activation pore-forming method and a carbon structure self-encapsulation and rearrangement method to form a novel energy storage material with an alternating distribution of internal microcrystalline carbon / metal and surface amorphous carbon layers / short-range nanochannel structures. This material can be applied to lithium-ion batteries and supercapacitors. When used in lithium-ion batteries, it exhibits good conductivity, high reversible specific capacity, and high rate performance. After being fabricated into a battery, it remains stable after 200 cycles, and the reversible capacity reaches 863 mAh / g after 200 cycles at a 0.1C current density. When used in the field of supercapacitors, it exhibits excellent rate performance and significantly improves specific capacitance. The specific capacitance can reach 143 F / g at a current density of 0.2 A / g, and the capacitance retention rate can reach 63% at a current density of 10 A / g.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of advanced carbon material preparation technology and electrochemical energy storage materials. Specifically, it relates to a carbon-supported metal composite energy storage material prepared by using pitch-based carbon material as a precursor and coupling it with metal load through activation pore formation. It can be directly applied to the fields of lithium-ion battery anode and supercapacitor electrode. Background Technology

[0002] Lithium-ion batteries and supercapacitors are mainstream electrochemical energy storage devices, and the conductivity, pore structure, ion transport efficiency, and structural stability of the electrode materials directly determine the device performance. Porous carbon materials, due to their wide availability, good conductivity, and high stability, are the core substrate for energy storage electrodes.

[0003] Traditional methods for preparing porous carbon often employ etching with strong alkalis such as KOH, which suffers from problems such as equipment corrosion, wide pore size distribution, easy collapse of pore structure, and poor rate performance. Pitch-based precursors (coal tar pitch, petroleum coke, mesophase pitch, etc.) are rich in polycyclic aromatic hydrocarbons and easily form ordered microcrystalline structures, making them ideal raw materials for preparing high-performance carbon materials. However, conventional activation methods struggle to achieve precise pore size control and uniform metal loading.

[0004] Patent CN118005002A discloses a carbon-based composite material, its preparation method, and its application. This invention typically uses biomass to impregnate metal salts, utilizing the mineralization effect of biomass to enrich the metal salts, and then uses a metal catalyst to grow carbon nanotubes on the surface of the carbon material, increasing the conductivity of the carbon material. However, it suffers from defects such as metal particle agglomeration, structural expansion, and insufficient cycle stability. Patent CN114480907A discloses a carbon-based / metal composite material and its preparation method. This invention mixes alkali metals with metal framework materials and calcines them to obtain the carbon-based / metal composite material, resulting in an atomically dispersed composite carbon / metal composite material. However, it suffers from defects such as long ion transport paths and non-uniform pore structure. The common defects of existing carbon-supported metal composite materials often make it difficult to simultaneously meet the application requirements of high capacity, high rate, and long cycle time. Therefore, developing pitch-based carbon-supported metal composite energy storage materials with controllable pore structure, uniform metal dispersion, and stable structure has significant engineering value and scientific significance for improving the performance of energy storage devices. Summary of the Invention

[0005] (1) Preparation of cone-shaped porous carbon

[0006] A pitch-based precursor and a non-alkaline etchant were mixed at a mass ratio of 10:1-2:1 and ball-milled at 600 r / min for 3 h to obtain a composite powder uniformly coated with the etchant. The powder was then heated in two stages under an argon atmosphere: the first stage was at 300-500 ℃ for 60-120 min at a heating rate of 2 ℃ / min; the second stage was at 600-800 ℃ for 60-120 min at a heating rate of 5 ℃ / min. After acid washing and water washing until neutral, a porous carbon with a conical pore structure was obtained.

[0007] (2) Metal loading and ammonia calcination

[0008] Porous carbon was impregnated in a metal salt-ethanol aqueous solution, with the metal salt loading being 5-10% of the porous carbon mass; dried at 50-60 ℃ for 1-3 h; calcined in an ammonia atmosphere at an ammonia flow rate of 20-100 mL / min, held at 900-1000 ℃ for 1-2 h at a heating rate of 5 ℃ / min, to obtain a metal / carbon composite energy storage material with nanochannels on its surface.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] (1) The hole structure is precise and controllable. Two-stage heating and non-strong alkali etching are used to form a conical hole with a large opening and a small bottom. The hole diameter is evenly distributed, avoiding the disordered hole diameter and structural collapse of traditional strong alkali etching.

[0011] (2) Excellent metal dispersibility, metal salts decompose in situ under ammonia atmosphere, no obvious agglomeration, strong bond with carbon matrix, providing a large number of lithium ion storage sites.

[0012] (3) High efficiency of ion transport, short-range nanochannels are generated in situ on the surface, which greatly shortens the ion transport path and significantly improves the rate performance; high structural stability, with an amorphous carbon layer on the surface covering the internal microcrystalline carbon / metal, which suppresses volume expansion during charge and discharge and improves cycle life. Attached Figure Description

[0013] Figure 1 Region I: Surface amorphous carbon layer / short-range nanochannel structure; Region II: Internal microcrystalline carbon structure / metal composite region;

[0014] ①: Graphite-like microcrystalline structure; ② Amorphous carbon structure; ③ Metal; ④ Short-range nanochannel structure. Detailed Implementation

[0015] Example 1:

[0016] Petroleum coke and K2CO3 were mixed at a mass ratio of 2:1 and ball-milled at 600 r / min for 3 h. The mixture was then heated in a two-stage process under an argon atmosphere: the first stage was at 500 ℃ for 60 min at a heating rate of 2 ℃ / min; the second stage was at 800 ℃ for 60 min at a heating rate of 5 ℃ / min. After acid washing and water washing to neutrality, porous carbon was obtained. The porous carbon was impregnated in a FeCl3-ethanol aqueous solution with a FeCl3 loading of 10% of the porous carbon mass. It was dried at 60 ℃ for 3 h and calcined in an ammonia atmosphere at a flow rate of 100 mL / min, holding at 900 ℃ for 2 h at a heating rate of 5 ℃ / min, yielding Fe / C composite energy storage material 1. When directly assembled into a battery, the reversible capacity reached 752 mAh / g after 200 cycles at a 0.1C current density. After acid washing and water washing to neutrality, it was assembled into a supercapacitor, achieving a specific capacity of 92 mAh / g at a current density of 0.2 A / g. With a current density of 10 A / g, the capacity retention rate can reach 58%.

[0017] Example 2:

[0018] Coal tar pitch and K2CO3 were mixed at a mass ratio of 10:1 and ball-milled at 600 r / min for 3 h. The mixture was then heated in a two-stage process under an argon atmosphere: the first stage was at 300 ℃ for 120 min at a heating rate of 2 ℃ / min; the second stage was at 600 ℃ for 120 min at a heating rate of 5 ℃ / min. After acid washing and water washing to neutrality, porous carbon was obtained. The porous carbon was impregnated in a FeCl3-ethanol aqueous solution with a FeCl3 loading of 10% of the porous carbon mass. It was dried at 60 ℃ for 3 h and calcined in an ammonia atmosphere at a flow rate of 100 mL / min, holding at 900 ℃ for 2 h at a heating rate of 5 ℃ / min, yielding Fe / C composite energy storage material 2. When directly assembled into a battery, the reversible capacity reached 863 mAh / g after 200 cycles at a 0.1C current density. After acid washing and water washing to neutrality, it was assembled into a supercapacitor, achieving a specific capacity of 131 mAh / g at a current density of 0.2 A / g. With a current density of 10 A / g, the capacity retention rate can reach 53%.

[0019] Example 3:

[0020] Coal liquefaction pitch and ZnCl2 were mixed at a mass ratio of 5:1 and ball-milled at 600 r / min for 3 h. The mixture was then heated in two stages under an argon atmosphere: the first stage was at 500 ℃ for 120 min at a heating rate of 2 ℃ / min; the second stage was at 800 ℃ for 120 min at a heating rate of 5 ℃ / min. After acid washing and water washing until neutral, porous carbon was obtained. The porous carbon was impregnated in a Co(NO3)3-ethanol aqueous solution with a Co(NO3)3 loading of 5% of the porous carbon mass. It was dried at 50 ℃ for 3 h and calcined in an ammonia atmosphere at an ammonia flow rate of 20 mL / min, holding at 1000 ℃ for 1 h at a heating rate of 5 ℃ / min. At ℃ / min, Co / C composite energy storage material 3 was obtained. After direct assembly into a battery, the reversible capacity reached 510mAh / g after 200 cycles at a current density of 0.1C. After acid washing and water washing to neutrality, a supercapacitor was assembled. The specific capacity reached 122 F / g at a current density of 0.2A / g, and the capacity retention rate reached 49% at a current density of 10A / g.

[0021] Example 4:

[0022] Mesophase pitch and MgCO3 were mixed at a mass ratio of 3:1 and ball-milled at 600 r / min for 3 h. The mixture was then heated in a two-stage process under an argon atmosphere: the first stage was at 500 ℃ for 60 min at a heating rate of 2 ℃ / min; the second stage was at 800 ℃ for 60 min at a heating rate of 5 ℃ / min. After acid washing and water washing to neutrality, porous carbon was obtained. The porous carbon was impregnated in an aqueous solution of ferric ammonium sulfate dodecahydrate and ethanol, with the ferric ammonium sulfate loading being 10% of the porous carbon mass. It was dried at 60 ℃ for 3 h and calcined in an ammonia atmosphere at a flow rate of 50 mL / min, holding at 1000 ℃ for 2 h at a heating rate of 5 ℃ / min, to obtain Fe / C composite energy storage material 4. When directly assembled into a battery, the reversible capacity reached 792 mAh / g after 200 cycles at a 0.1C current density. After acid washing and water washing to neutrality, it was assembled into a supercapacitor, achieving a specific capacity of 143 mAh / g at a current density of 0.2 A / g. With a current density of 10 A / g, the capacity retention rate can reach 63%.

Claims

1. A method for preparing an asphalt-based carbon-supported metal composite energy storage material, characterized in that, Includes the following steps: (1) The asphalt-based precursor and the etching agent were mixed and ball-milled, and then heated in two stages to obtain porous carbon with a cone-shaped pore structure. (2) After cleaning the porous carbon obtained in step (1), place it in a beaker, immerse it in a metal salt-ethanol solution of 5-10% by weight of the porous carbon, dry it, and then place it in a tube furnace to calcine in an ammonia atmosphere to obtain a novel metal / carbon composite energy storage material with a nanochannel structure on the surface.

2. The preparation method of an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (1), the asphalt-based precursor is selected from one or more of the asphalt carbons such as petroleum coke, coal tar pitch, coal liquefaction pitch, oxidized coke, and mesophase pitch; the etchant is one or more of the non-strong alkaline etchants such as ZnCl2, MgCO3, and K2CO3.

3. The method for preparing an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (1), the asphalt-based precursor and etchant are weighed and added to a zirconia ball mill jar at a mass ratio of 10:1-2:1, and ground at 600 r / min for 3 hours. After ball milling, a composite material with the etchant adhering to the surface of the asphalt-based precursor is obtained. The material is placed in a tube furnace. The first stage of heating is carried out at 300-500 ℃ under an argon atmosphere for 60-120 minutes at a heating rate of 2 ℃ / min. The second stage of heating is carried out at 600-800 ℃ under an argon atmosphere for 60-120 minutes at a heating rate of 5 ℃ / min. After acid washing and cleaning, the product yields porous carbon with a cone-shaped pore structure.

4. The preparation method of an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (1), the composite structure material on the surface of the asphalt-based precursor obtained after ball milling is in the microcrystalline development stage and light component overflow stage inside the asphalt-based precursor during the first stage of slow heating. The internal structure of the asphalt-based precursor gradually develops and becomes orderly. The overflow of light components forms small pores on the surface. The surface etchant begins to melt and flow, filling the pore structure caused by the overflow of light components. During the second stage of heating, the etchant etches along the filled pore structure to form a conical flask pore structure with a "large mouth and small bottom". At the same time, it peels off and destroys the carbon layer structure connected to the pore surface to form a large number of amorphous carbon structures, initially forming a porous carbon structure of "internal microcrystalline carbon - surface amorphous carbon / pore phase distribution structure".

5. The method for preparing an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (2), the mass ratio of the porous carbon, metal salt, and ethanol aqueous solution (50wt.% ethanol + 50% water) is 20:1:20-10:1:20; the metal salt is one or more of the nitrates, chlorides, sulfates, or ferric ammonium sulfates and ferrates of Fe, Al, Co, Ni, and Mg dissolved in the ethanol aqueous solution; the drying refers to placing it in an oven and drying it at 50-60℃ for 1-3 hours.

6. The method for preparing an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (2), the calcination is carried out in an ammonia atmosphere with an ammonia flow rate of 20-100 mL / min, a calcination temperature of 900-1000℃, a heating rate of 5℃ / min, and a holding time of 1-2h.

7. The preparation method of an asphalt-based carbon-supported metal composite energy storage material according to claim 1, characterized in that: In step (2), the porous carbon impregnated with and loaded with metal salts is calcined in an ammonia atmosphere. Under high temperature, the metal salts decompose into free metal ions. At this time, a "deposition-like carbon nanotube generation" reaction will occur under the catalysis of metal ions. The metal ions directly contact the amorphous carbon structure on the surface of the porous carbon and near the pores. However, the amorphous carbon structure remains relatively stable at 900-1000℃ and will not form a free carbon structure. Therefore, only a small amount of amorphous carbon structure in contact with metal ions is captured and redeveloped to form a short-range ordered nanochannel structure. Finally, a new type of energy storage material A is formed by "internal microcrystalline carbon / metal - surface amorphous carbon layer / short-range nanochannel structure phase distribution".

8. The product according to claim 7, characterized in that: Energy storage material A is acid-washed and cleaned to obtain energy storage material B, which can be applied in the field of supercapacitors. The amorphous carbon layer / short-range nanochannel structure on the surface of energy storage material B increases additional capacitance storage sites. At the same time, it creates a pressure difference between the pore opening and the bottom of the pore during charging and discharging, which drives electrolyte ions to pass through the pore opening in an orderly manner and move along the pore wall in an orderly manner. Finally, orderly adsorption and desorption occur at the bottom of the pore. When the current or voltage changes abruptly, the existence of the pressure difference between the tubes maintains the orderly and stable adsorption and desorption of electrolyte ions, while bringing a certain hysteresis effect of ion adsorption and desorption, thereby improving the specific capacity. At the same time, it improves the buffering and instantaneous regulation capabilities of the capacitor carbon. The specific capacity can reach 143 F / g at a current density of 0.2 A / g, and the capacity retention rate can reach 63% at a current density of 10 A / g.

9. The product according to claim 7, characterized in that: Energy storage material A can be directly applied to the field of lithium-ion batteries. The internal microcrystalline carbon / metal structure provides additional storage points for lithium ions, while the surface amorphous carbon structure encapsulates the internal microcrystalline carbon / metal structure, inhibiting expansion and improving the cycle life and stability of the battery. The short-range nanochannel structure provides channels for ion transport, enhancing the conductivity and rate performance of the material. After being made into a battery, energy storage material A can remain stable after 200 cycles, and the reversible capacity after 200 cycles at a 0.1C current density can reach 863mAh / g.

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