Research on polyanionic cathode materials for 3500mah 18650 battery has made progress

As a representative member of the post-lithium era, 3500mah 18650 battery are extremely attractive and have great application prospects in large-scale energy storage systems. Research on 3500mah 18650 battery (SIBs) has become a hot topic due to its abundant resources, high cost-effectiveness and long service life. Polyanionic sodium-based materials are one of the most promising electrode materials in SIBs. They have good structural stability, safety and high operating voltage. However, the relatively low electrical conductivity and specific capacity of this material limits their applications.

A research team led by Researcher Li Xianfeng, Researcher Zhang Huamin, and Associate Researcher Zheng Qiong from the Energy Storage Technology Research Department of the Dalian Institute of Chemical Physics has made new progress in the research of polyanion cathode materials for 3500mah 18650 battery. The research results were published in "American Chemical Society Energy Letters" superior.

3500mah 18650 battery have the advantages of abundant resources, low cost, and high cost performance, and have good application prospects in the fields of electric bicycles, low-speed electric vehicles, distributed energy storage, and large-scale energy storage. The working principle of 3500mah 18650 battery is similar to that of lithium-ion batteries. The cathode material determines the energy density of 3500mah 18650 battery. Polyanionic compounds have the advantages of higher voltage, higher theoretical specific capacity, and stable structure, making them one of the preferred cathode materials for 3500mah 18650 battery. In order to improve its rate performance, optimize full battery performance, further reduce material preparation costs, and achieve large-scale preparation of materials, it is an urgent problem to be solved. Researchers have carried out a series of studies on the structural unit control of polyanion cathode materials for 3500mah 18650 battery, sodium deintercalation mechanism, carbon composite preparation, full battery and soft pack battery construction, etc., and have achieved high-performance sodium vanadium trifluorophosphate, Efficient synthesis and application of vanadium-based polyanionic compounds such as sodium fluorophosphate and sodium vanadium phosphate.

Sodium vanadium trifluorophosphate has a three-dimensional network structure formed by the intermittent connection of [V2O8F3] dioctahedron and [PO4] tetrahedron, which is conducive to the rapid insertion and extraction of Na+. Its theoretical energy density is 500Wh/kg, which is equivalent to the energy density of LiFePO4 in lithium-ion batteries (550Wh/kg). It has attracted much attention in recent years.

The research team proposed a low-temperature solvothermal-ball milling preparation method to achieve a green and economical synthesis of highly conductive carbon-coated sodium vanadium fluorophosphate (Na3V2(PO4)2F3). The study found that the solvent type and pH value play a key role in the morphology and product purity of Na3V2(PO4)2F3 during the low-temperature solvothermal process. In the acidic environment of ethanol and water blend solvents, the crystals have high surface energy, and high purity and high yield Na3V2(PO4)2F3 can be obtained. Effectively improve its ion diffusion and electronic conduction capabilities. The sodium-ion battery assembled from Na3V2(PO4)2F3 has a high specific capacity of 138mAh/g at a current of 0.5C, and its capacity can still maintain 122mAh/g at a high current of 40C. This low-temperature solvothermal-ball milling method will provide a new strategy for the practical application of low-cost, high-performance sodium-ion battery technology.

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