Cu/Li4Ti5O12 scaffolds as superior anodes for lithium-ion batteries

Abstract

Nanostructured active materials with both high-capacity and high-rate capability have attracted considerable attention, but they remain a great challenge to be realized. Herein, we report a new route to fabricate a bicontinuous Cu/Li4Ti5O12 scaffold that consists of Li4Ti5O12 nanoparticles (LTO NPs) with highly exposed (111) facets and nanoporous Cu scaffolds, which enable simultaneous high-capacity and high-rate lithium storage. It is a ‘one stone, two birds’ strategy. When tested as the anode in lithium-ion batteries LIBs, Cu/LTO showed superior performance, such as a lifespan greater than 2000 cycles and an ultrafast charging time (<45 s). Notably, the ultrahigh capacity slightly larger than the theoretical value was also observed in Cu/LTO at low current density. Density functional theory calculations and detailed characterizations revealed that the highly exposed (111) facets on the edge are the reason for its unique storage mechanism (8a+16c), which is different from the transition between 8a and 16c in bulk LTO. Encapsulating tiny electroactive particles inside nanoporous electrodes can boost the storage and recharge rates of lithium-ion batteries. Researchers have recently identified Li4Ti5O12 (LTO) nanoparticles as promising battery anodes because they have numerous visible and highly reactive crystal planes. Now, Xi Wang from the National Institute for Materials Science in Japan and co-workers have discovered a way to exploit the potential of LTO by enclosing these crystals in a scaffold-like template made from nanoporous copper. This template is more conductive than typical current collectors and traps the nanoparticles inside smooth, curved pores that expose many valuable LTO crystal planes. The improved electron and ion transport kinetics of the team's design produced remarkable results — ultrahigh capacities exceeding theoretical values, battery lifetimes of over 2,000 charge cycles and blazingly fast 45-second charge times. We report a new ‘one stone two birds’ strategy to fabricate a bicontinuous Cu/L4T5O12 electrode consisting of nanoporous Cu scaffold and the encapsulated nanoparticles with highly exposed (111) planes. These architectures provide rapid pathways for ion and electron transport and realize the additional lithium storage capacity on the surfaces of LTO, realizing the high-rate and high-capacity lithium storage.