Min Zhao,Dong-Lin Zhao,Hui-Xian Yang,Xin-Yao Han,Ya-Jing Duan,Xin-Min Tian,Wen-Jie Meng
Germanium-based materials are considered to be an alternative material for high energy density lithium-ion battery anodes due to their superior theoretical capacity. However, the severe volume expansion during the lithium insertion and the easily agglomerated tendency of Ge nanoparticles become the key obstacles to the stable cycle and capacity retention of Ge anodes. Herein, we designed a double-layered protective structure in which the cubic hollow Ge@C hybrids are uniformly dispersed on reduced graphene oxide sheets (Ge@C-rGO) through conventional dopamine-coated precursor and subsequent carbothermal reduction processes. In the synthesized Ge@C-rGO hybrids, the large-area rGO sheets cooperate with the amorphous carbon layer to accommodate and buffer the volume expansion of Ge particles, and to ensure that the Ge nanoparticles are in a separated state to the utmost extent. The Ge@C-rGO electrode which is employed in lithium-ion battery owns the reversible capacities of 1183 mAh·g −1 at the specific current of 100 mA g −1 and 710 mAh·g −1 at 1 A g −1 for 200 cycles. In addition, it exhibited good cycle stability, rate reversibility and electronic conductivity, and is a potential anode material with high performance and long-cycle capability.
X T Zhang,Y F Yuan,M Zhu,G C Cai,Z W Tong,Z Y Yang
Low electronic conductivity and large volume variation result in inferior lithium storage performance of ZnO. To overcome these shortcomings of ZnO, herein ZnO nanoparticles are encapsulated in resorcinol–formaldehyde resin-derived hard carbon and then further assembled into a 3-dimensional mesoporous framework structure using a polyvinyl pyrrolidone-derived soft carbon network. The synthesis methods include the polymerization of resorcinol–formaldehyde resin and a polyvinyl pyrrolidone-boiling method. ZnO@dual carbon has af large specific surface area (153.7 m2 g−1) and high porosity. It exhibits excellent cycling performance and high rate capability. After 350 cycles at 500 mA g−1, the ZnO@dual carbon still delivers a discharge capacity of 701 mAh g−1 while the actual discharge capacity of ZnO reaches 950.9 mAh g−1. At 2 A g−1, ZnO@dual carbon delivers the average discharge capacity of 469.6 mAh g−1. The electrochemical performance of ZnO@dual carbon is remarkably superior to those of ZnO@single carbon, pure carbon and pure ZnO nanoparticles, demonstrating the superiority of the dual carbon-assembly structure. This composite structure greatly improves the structural stability of ZnO, enhances its electron conductivity and overall electron transport capacity; which facilitates electrolyte penetration and Li ion diffusion, leading to improved cycling stability and good rate capability.
Qianqian Li,Man Zhang,Yutong Nong,Qichang Pan,Youguo Huang,Hongqiang Wang,Fenghua Zheng,Qingyu Li
Zinc sulfide (ZnS) is considered as a candidate anode material to replace commercial graphite anodes in high-performance lithium-ion batteries (LIBs). However, the significant volume change during the lithiation/delithiation process leads to poor cycle and rate performance, severely limiting the application of the ZnS anode in LIBs. Here, core–shell ZnS@C microrods (ZnS@C MRs) were synthesized via a simple hydrothermal method, followed by in situ polymerization and a sulfidation process. Due to the rationally designed structure, the outer carbon shell can avoid the volume expansion of ZnS, thus maintaining the structural stability. Moreover, the carbon shell can not only enhance the conductivity, but also inhibit direct contact between ZnS and the electrolyte during the repeated lithiation/delithiation process. Accordingly, ZnS@C MRs exhibit outstanding electrochemical performance in LIBs. Specifically, a capacity of 392 mA h g−1 is obtained after 500 cycles at 1.0 A g−1. Moreover, a capacity of 162 mA h g−1 is maintained at 3.0 A g−1.
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