Prof. Zilong Tang’s Group reports Novel Vanadate Cathodes for High‐Rate Lithium‐Ion Batteries
A research team led by Prof. Zilong Tang at the School of Materials and Engineering published their research results entitled “Glass-ceramic-like vanadate cathodes for high-rate lithium-ion batteries” in Advanced Energy Materials on December 3rd, 2019. According to the protocol in their previous report about lithium titanate hydrates anodes (Nature Communications, 2017, 8: 627), this work focused on the problems of the low volume energy density, poor coulombic efficiency and rapid capacity decay for nanostructured electrodes.
Nanomaterials are good candidates in high-rate batteries because of their short diffusion distance and fast kinetics, yet they often suffer from extensive side reactions with organic electrolytes and are prone to agglomerate due to anomalously large surface areas. On the other hand, while micron-size materials provide better stability, the lattice diffusivity is often too slow for lithium ion intercalation over the same length scale in a short time. From this perspective, micron-scale dense nanocrystalline materials with a short-circuit diffusion pathway as well as a low surface area can effectively solve the above issues.
Figure 1 (a) In situ XRD patterns and (b) contour plot of magnified low-angle regions upon heating. (c) Calculated grain size. (d) Schematic phase transition process with varying grain sizes.
This work demonstrated that a fine tuning of the heat-treatment process (top-down method) for micro-sized vanadate plates can create a glass-ceramic-like structure with abundant internal boundaries (thus allowing fast lithium ion diffusion) yet a very small surface area (thus minimizing contact and side reactions with organic electrolytes). The obtained vanadate cathodes exhibit an impressive high-rate capacity, better ionic kinetics and cycling stability.
Figure 2 (a-d) Electrochemical performances of glass-ceramic-like vanadate cathodes. (e) Comparison of rate performance with literature data in vanadate related systems.
This top-down approach to create dense nanocrystalline electrode materials is rather simple compared with the common method of forming secondary particles via bottom-up assembly (such as spray drying, self-agglomeration during coprecipitation, et al.), which could also be applicable to other transition metal oxide electrodes, especially those derived from hydrates.
The corresponding authors are Prof. Zilong Tang from Tsinghua University, and Dr. Shitong Wang and Dr. Yanhao Dong from the Massachusetts Institute of Technology. The first author is Yutong Li, a PhD candidate under the supervision of Prof. Tang. This project was financially supported by the National Science Foundation of China.
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