CoGeO2(OH)2 hydrangea assembled with 2D nanoplates towards application of lithium-ion batteries

Abstract Germanium-based materials possess high theoretical capacity of approximately 1000 mAh·g−1, nevertheless, the practical electrochemical performance is severely hampered by poor cyclability due to volumetric expansion of Ge upon cycling. Herein, novel hydrangea-like CoGeO2(OH)2 constructed by 2D nanoplates has been facilely synthesized with the assistance of ethylene glycol and further applied to anode materials for lithium ion storage. The hydrangea-like CoGeO2(OH)2 anode exhibits an enhanced specific capacity of 1174 mAh·g−1 at a current density of 0.5 A g−1 after 100 cycles. Such outstanding electrochemical performance could be accredited to the rationally designed hydrangea-like structure, which can relieve the interval stress aroused by lithiation/de-lithiation, shorten the pathway of electron/ion transportation and take advantage of the pseudocapacitive nature of two dimensional nanosheets that could improve the reaction kinetics and endow the material with remarkable rate capability. Moreover, the inherent Co-bonded hydroxyl groups facilitate the pseudocapacitive effect, and Ge-based component contributes to the capacity. These advantages help CoGeO2(OH)2 hydrangeas gain a competitive edge over other candidates of anode materials for lithium-ion batteries.