Achieving High Lithium Storage Capacity and Long-Term Cyclability of Novel Cobalt Germanate Hydroxide/Reduced Graphene Oxide Anodes with Regulated Electrochemical Catalytic Conversion Process of Hydroxyl Groups

To develop ternary transition-metal germanate anodes with superior lithium storage performances for lithiumion batteries, a novel capacity counterbalance approach in one compound is designed by introducing an electrocatalytic conversion-type component with a positive cycling trend to compensate the negative cycling trend of the GeO2 component. Novel cobalt germanate hydroxide (CGH) nanoplates chemically bonded on reduced graphene oxide (RGO) sheets are thus synthesized with a mild one-pot hydrothermal approach, constructing maximal face-to-face contact interfaces with interfacial bonds to boost the electrochemical conversion reactions. Furthermore, the hydroxyl groups (Co-OH) of CGH nanoplates are regulated by thermal annealing treatments, thus controlling the capacity contribution resulting from the electrocatalytic conversion reaction of LiOH to exactly offset the capacity fading of GeO2. The results on the CGH electrodes at different cycling potentials confirm the stepwise electrochemical reactions of Co, GeO2, and LiOH. The equilibrium of these electrochemical reactions ensures a stable cycling capacity without obvious fluctuations. Consequently, the optimal CGH/RGO hybrid anode delivers a reversible capacity as high as 1136 mA h g(-1) at 0.1 A g(-1) until 100 cycles. It also exhibits a long cyclability with a retained capacity of 560 mA h g(-1) at 1 A g(-1) until 1000 cycles. This work demonstrates a general and efficient capacity counterbalance method to highly boost lithium storage performances in terms of high capacity and long-term cyclability.