Lithium ion batteries (LIBs) are a key-enabling technology for addressing the power and energy demands of electric vehicles and stationary electrical storage for renewable energy as well as mobile electronics. However, current lithium ion battery technology is tied in with conventional reaction mechanisms such as insertion, conversion, and alloying reactions even though most future applications like EVs demand much higher energy densities than current ones. In order to achieve the battery performance that all applications expect, much effort has been made to develop new electrode materials to enhance both the energy density and cycle performance of LIBs. Namely, exploring the exceptional reaction mechanism and related electrode materials can be critical for pushing current battery technology to a next level.
Here, we introduce an excellent reaction with Co(OH)2 material, which exhibits an initial charge capacity of 1112 mAh g−1, about twice its theoretical value based on known conventional conversion reaction, and retains its ﬁrst cycle capacity after 30 cycles. The combined results from ex situ XRD, XAS, AIMD simulation, STEM, and XPS measurements indicate that nanosized Co metal particles and LiOH are generated by conversion reaction at high voltages, and CoxHy, Li2O, and LiH are subsequently formed by hydride reaction between Co metal, LiOH, and other lithium species at low voltages, resulting in a anomalously high capacity beyond the theoretical capacity of Co(OH)2. These ﬁndings will provide not only further understanding of exceptional lithium storage of recent nanostructured materials but also valuable guidance to develop advanced electrode materials with high energy density for next-generation batteries. Subsequently, we will also present detailed lithium storage mechanisms for nanostructured anode materials that show anomalously higher capacity than their theoretical limit, at the time of meeting.
Fig. 1. Illustration of the overall electrochemical reaction mechanism of CS-Co(OH)2 anode