Mingjiong Zhou

In situ crosslinked PVA–PEI polymer binder for long-cycle silicon anodes in Li-ion batteries

A novel polymer binder, synthesized via in situ thermal cross-linking of water-soluble polyvinyl alcohol (PVA) and poly(ethylene imine) (PEI) precursor, is applied as a functional network binder to enhance the electrochemical performance of a silicon anode. The Si anode with PVA–PEI binder exhibits high specific capacity (3072.9 mA h g−1) in the initial cycle, high initial coulombic efficiency of 83.8% and excellent long-term cycling stability (1063.1 mA h g−1 after 300 cycles). Furthermore, the Si anode containing PVA–PEI binder also exhibits excellent rate performance, reaching a high specific capacity of 1590 mA h g−1 even at high current density of 10 A g−1. These outstanding electrochemical properties are ascribed to the reversibly-deformable polymer network and the binders strong adhesion to the silicon particles. This low-cost and eco-friendly polymer binder has great potential to be used for silicon anodes in next generation Li-ion batteries.

Hierarchical porous ZnMnO3 yolk–shell microspheres with superior lithium storage properties enabled by a unique one-step conversion mechanism

ZnMnO3 has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity. However, it suffers from capacity fading because of the large volumetric change during cycling. Here, porous ZnMnO3 yolk–shell microspheres are developed through a facile and scalable synthesis approach. This ZnMnO3 can effectively accommodate the large volume change upon cycling, leading to an excellent cycling stability. When applying this ZnMnO3 as the anode in lithium-ion batteries, it shows a remarkable reversible capacity (400 mA h g−1 at a current density of 400 mA g−1 and 200 mA h g−1 at 6400 mA g−1) and excellent cycling performance (540 mA h g−1 after 300 cycles at 400 mA g−1) due to its unique structure. Furthermore, a novel conversion reaction mechanism of the ZnMnO3 is revealed: ZnMnO3 is first converted into intermediate phases of ZnO and MnO, after which MnO is further reduced to metallic Mn while ZnO remains stable, avoiding the serious pulverization of the electrode brought about by lithiation of ZnO.