Research progress of carbon negative electrode materials for 18650 battery rechargeable

18650 battery rechargeable are new energy storage devices with high energy density and high power density. The research on their negative electrode materials mainly focuses on carbon materials. The working principle of carbon negative electrodes for 18650 battery rechargeable is analyzed, the preparation methods and electrochemical properties of activated carbon/graphite composite materials and three-dimensional carbon materials that can be used as negative electrodes for 18650 battery rechargeable are reviewed, the shortcomings in the current research on carbon materials for 18650 battery rechargeable are analyzed, and it is pointed out that the research focus of carbon negative electrode materials for 18650 battery rechargeable should be on in-depth research on their energy storage mechanism. Using quantum chemical calculation methods to study the relationship between the structure and performance of carbon materials is also a focus of future research.

1 Introduction to 18650 battery rechargeable

18650 battery rechargeable refer to a new energy storage device that combines double-layer capacitor energy storage and lithium ion deintercalation/embedding energy storage. They have high energy density and high power density and are expected to be widely used in special aerospace, special special, electric vehicles, electronic information and instrumentation, which are in urgent need of energy storage devices with high energy density, high power density and other performance. At present, the research on supercapacitor battery energy storage devices has gradually become a hot topic.

As one of the key materials for 18650 battery rechargeable, the negative electrode material should have the characteristics of both lithium-ion battery negative electrode materials and supercapacitor electrode materials. So far, carbon materials are the only commercialized negative electrode materials for lithium-ion secondary batteries and supercapacitor negative electrode materials, and there is still a lot of room for development in new and high-performance development. Therefore, carbon materials are still one of the hot spots in the research field of lithium-ion secondary battery negative electrode materials and supercapacitor negative electrode materials. Selecting carbon materials with wide sources, low prices and excellent performance as negative electrode materials for 18650 battery rechargeable has broad application prospects.

At present, there are relatively few studies specifically on carbon negative electrode materials for 18650 battery rechargeable, but there are literature reports that certain methods have been used to prepare carbon materials with excellent double-layer capacitance performance and lithium-ion battery performance. This paper mainly reviews the research status of carbon materials with both double-layer capacitance and lithium-ion battery performance, points out the current shortcomings of these materials, and analyzes the future research direction of carbon negative electrode materials for 18650 battery rechargeable.

2 Research progress of carbon negative electrode materials for 18650 battery rechargeable

In order to meet the requirements of lithium ion deintercalation/intercalation energy storage, the negative electrode of 18650 battery rechargeable should meet the following requirements: small free energy change in lithium ion intercalation reaction, high diffusion rate of lithium ions in the solid structure of the negative electrode, highly reversible intercalation reaction and good conductivity, stable thermodynamic properties and no reaction with electrolyte. At the same time, in order to meet the requirements of good double-layer energy storage, the negative electrode of 18650 battery rechargeable should also have good electrochemical stability, suitable pore structure and specific surface area, high potential window and other properties to ensure good performance in high-voltage battery systems, especially high-rate performance. Current research is mainly divided into two categories: one is to composite activated carbon with graphite intercalation compounds based on the requirements of activated carbon for double-layer energy storage and graphite intercalation compounds for lithium ion deintercalation/intercalation energy storage; the other is to prepare carbon materials with three-dimensional pores using different template methods based on the requirements of double-layer energy storage and lithium ion deintercalation/intercalation energy storage for different carbon pore sizes.

2.1 Activated carbon and graphite composite materials

Activated carbon is the earliest carbon electrode material used in supercapacitors and is also the most studied electrode material. As a supercapacitor electrode material, the advantages of activated carbon are good conductivity, ultra-high specific surface area (up to 2000m2/g or more), and adjustable pore structure. In addition, activated carbon also has the advantages of abundant raw materials, low price, good processing performance, and stable chemical properties. Among the carbon negative electrode materials for lithium-ion batteries, graphite intercalation compounds (GIC) are the most successfully applied. Compared with other embedded materials, this carbon material has a higher Faraday capacity, high cycle efficiency and low electrochemical potential. At present, the mesophase carbon microspheres (CMS) in GIC negative electrode materials are conducive to the embedding and de-embedding of lithium ions from all directions of the sphere due to their spherical particles and highly ordered layer stacking structure, avoiding the defects of graphite sheet swelling, collapse and poor cycle performance caused by excessive anisotropy of other graphite materials. CMS has become one of the main negative electrode materials used in long-life lithium-ion batteries and power batteries due to its superior properties. Li Jie et al. prepared a new negative electrode material by combining activated carbon with CMS. Its specific capacity in lithium-ion batteries reached 301.2 mA·h/g, and its specific capacity in supercapacitors reached 25 F/g. The potential window was increased to 3.5 VvsLi/Li+, and the energy density was increased to 40.3 W·h/kg. Because the outer layer of carbon material is expected to protect the inner layer of CMS, it can effectively prevent the co-embedding of solvated lithium ions and organic solvents from damaging the CMS layers, and has better battery characteristics.

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