3D Interconnected Hierarchically Macro-mesoporous TiO_2 Network Optimized by Biomolecular Self-assembly for High Performance Lithium Ion Battery

Biomolecular self-assembly is an effective synthesis strategy for materials fabrication with unique structural complexity and properties. For the first time, we intergrate inner-particle mesoporosity in a three-dimensional (3D) interconnected macroporous TiO_2 structure via the mediation of biomolecular self-assembly of the lipids and proteins from rape pollen coats and P123 to optimize the structure for high performance lithium storage. Benefitting from the hierarchically 3D interconnected macro-mesoporous structure with high surface area, small nanocrystallites and good electrolyte permeation, such unique porous structure demonstrates superior electrochemical performance, with high initial coulombic efficiency (94.4% at 1C) and a reversible discharge capacity of 161, 145, 127 and 97 mA h g-1 at 2, 5, 10 and 20C for 1000 cycles, with 79.3%, 89.9%, 90.1% and 87.4% capacity retention, respectively. Using SEM, TEM and HRTEM observations on the TiO_2 materials before and after cycling, we verify that the inner-particle mesoporosity and the Li_2Ti_2O_4 nanocrystallites formed during the cycling process in interconnected macroporous structure largely enhance the cycle life and rate performance. Our demonstration here offers opportunities towards developing and optimizing hierarchically porous structures for energy storage applications via biomolecular self-assembly.B. L. Su acknowledges the Chinese Central Government for an “Expert of the State” position in the Program of the “Thousand Talents”. Y. Li acknowledges Hubei Provincial Department of Education for the “Chutian Scholar” program. T. Hasan acknowledges funding from RAEng fellowship (Graphlex) and EPSRC IAA grant EP/K503757/1(GRASS). G. Van Tendeloo and Z. Y. Hu acknowledge support from the EC Framework 7 program ESTEEM2 (Reference 312483). This work is realized in the frame of a program for Changjiang Scholars and Innovative Research Team (IRT_15R52) of Chinese Ministry of Education. This work is also financially supported by Hubei Provincial Natural Science Foundation (2014CFB160), International Science & Technology Cooperation Program of China (2015DFE52870) and Self-determined and Innovative Research Funds of the SKLWUT (2015-ZD-7). We also thank J. L. Xie, X. Q. Liu and T. T. Luo for TEM analysis from Research and Test Center of Materials at Wuhan University of Technology.This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via https://doi.org/10.1039/c6ra00332