Three-Dimensional Graphene-Wrapped Co0.85se@C As High Volumetric Capacity Anode Material For Lithium-Ion Batteries

To overcome the drawbacks of poor long-term cyclic and large volume expansion for selenides, which have high theoretical specific capacity and are promising candidates to fulfill the requirement of high volumetric energy density for lithium-ion batteries, we prepared a novel three-dimensional graphene-wrapped Co0.85Se@C composite (3D-G@Co0.85Se@C) through a capillary evaporation-induced drying method. This process leads to a shrinkage of graphene assembly, generating an ideal configuration compact composite material. XPS analysis confirms that the C-O-Co is formed from reactions between the Co0.85Se@C and oxygen-containing groups on graphene oxide during the preparation process. Such a strong covalent interaction between the Co0.85Se@C and graphene, together with its compact structure are favorable to high volumetric capacity. The electrochemical measurements show that the specific capacity of the GCS is about 1022.5 mAh g(-1) after 200 cycles at 0.1 A g(-1), corresponding to a remarkably reversible volumetric capacity of 2096.1 mAh cm(-3). Moreover, good long-cycling durability and rate performance are also achieved. Consequently, this composite is a promising electrode material with high volumetric capacity in lithium-ion batteries.