A Layer-Structured Electrode Material Reformed by a PO4-O2 Hybrid Framework toward Enhanced Lithium Storage and Stability

• Published in: Advanced energy materials 2016-04, Vol.6 (7), p.n/a
• Main Authors: Min, Sul Hee, Jo, Mi Ru, Choi, Si-Young, Kim, Yong-Il, Kang, Yong-Mook
• Format: Article
• Language: English
• Subjects: batteries; electrodes; hybrid materials; Lithium; lithium storage; Phase transitions; surface modifications
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201501717

The surface framework of LiCoO2 is modified through a surface treatment called phosphidation, which suppressed the unwanted phase transition occurring above 4.2 V. The surface instability of LiCoO2 toward organic electrolytes is simultaneously improved by changing its surface structure from an O2‐based framework to a PO4‐based framework that can protect against HF attack during cycling. Phosphidated LiCoO2 is successfully synthesized that showed greater stability in its bulk and surface structures. The phosphidated form enables faster Li+ diffusion and prevents irreversible phase transitions, especially when charged above 4.2 V, and consequently demonstrates excellent cycling performance and rate capabilities. The improved kinetics and stability resulting from phosphidation make LiCoO2 highly suitable as a high‐voltage cathode material for use in lithium ion batteries. Improvement of the structure and surface stabilities of a LiCoO2 cathode is demonstrated by changing the surface design from an O2‐framework to a PO4‐framework of LiCoO2. With its advantages of easy synthesis, high structural stability, and high‐surface stability from chemical attack, this surface modified LiCoO2 (phosphidated LiCoO2) shows great potential for use in lithium rechargeable batteries at high‐voltage ranges.