Supersonically Sprayed Carbon-Coated Bimetallic Zn2SnO4 with Reduced Graphene Oxide for Rapid-Charging, Binder-Free, and Long-Term-Stable Lithium-Ion-Battery Anodes

Abstract

High capacity, rapid-charging, and long-term recyclability are the essential characteristics of high-performance lithium-ion battery (LIB) electrodes, which are particularly important in the electric vehicle industry. Bimetallic Zn2SnO4 nanoparticles wrapped in carbon shells were supersonically sprayed with reduced graphene oxide (rGO) nanosheets to fabricate rapid-charging, binder-free, and long-term-stable LIB anodes. The fabricated Zn2SnO4/C@rGO composite exhibited high capacity retention and specific capacity over a wide range of current densities. Zn2SnO4 was first reduced to metal oxides (ZnO and SnO2) and then to metals (Zn and Sn) during the lithiation process. The reduced metals were successively alloyed with Li+ ions, which in turn formed LiZn and LiSn. These cyclic conversions and alloying processes enhanced the performance of the LIBs, resulting in a high capacity of 1126 mAh⋅g-1 after 400 cycles at a high current density of 1000 mA·g-1; such high performance indicates the rapid-charging capability of the fabricated LIB anodes. The agglomeration of identical oxide particles was reduced during the long-term cycling process by introducing bimetallic Zn2SnO4, which was reduced to ZnO and SnO2 in the first cycle. Metal formation through the conversion and subsequent alloying processes caused the pulverization of ZnO and SnO2, whose mixture favorably alleviated agglomeration of identical oxides owing to the distinct grain boundaries of ZnO and SnO2. In addition, ZnO and SnO2 particles were confined within a carbon shell, which originated from the introduction of polyvinylpyrrolidone. The carbon shell further alleviated the particle agglomeration for Zn2SnO4/C@rGO, which is identified as the optimal case, yielding a capacity retention of 106% for the first reversible capacity at a current density of 1000 mA⋅g-1 after 400 cycles.