State of the art commercial LIBs use low cost, long cycle life graphite anode with a theoretical limit of 372 mAh g-1. In contrast, theoretical capacities of alloying anodes such as Si, Ge, Sn are several to ten folds higher. However, alloying electrodes suffer from large volume expansion and entailing rapid capacity loss. Here, the issues were effectively tackled using porous asymmetric membrane structure that can be fabricated on a large scale using a straightforward phase inversion method as inspired from commercial water desalination technology. Various kinds of phase inversion methods have been developed to obtain asymmetric porous membranes that contain Si, Ge, SnO2, SiOx and V2O5. 90% initial capacity at ~1400 mAh g-1 can be retained in 300 cycles for co-axial Si asymmetric membrane electrode. SnO2 asymmetric membranes synthesized using a combined approach involving sol-gel chemistry and phase inversion showed a specific capacity of 500 mAh g-1 with more than 96% capacity retention in 400 cycles applying a current density of 600 mA g-1. Nearly 100% capacity retention of 700 mAh g-1 at 400 mA g-1 was observed in 160 cycles for sandwiched germanium asymmetric membranes that were etched with hydrogen peroxide solutions. The asymmetric membranes were characterized by using electron microscopes, powder X-ray diffractometer, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric and surface area analyzers. The relationship among electrochemical performance, phase invention dynamics, membrane geometry, membrane porosity, membrane coating and concentration of active materials was explored and clearly identified. Most recently, the same concept has been extended to sodium ion battery successfully.

Asymmetric membrane structure: General solution for stabilizing high capacity lithium ion battery anodes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.