Letter pubs.acs.org/NanoLett
Multishelled TiO2 Hollow Microspheres as Anodes with Superior Reversible Capacity for Lithium Ion Batteries Hao Ren,† Ranbo Yu,*,† Jiangyan Wang,‡ Quan Jin,‡ Mei Yang,‡ Dan Mao,‡ David Kisailus,‡ Huijun Zhao,¶ and Dan Wang*,‡ †
Department of Physical Chemistry, School of Metallurgical and Ecological Engineering, University of Science & Technology Beijing, No. 30, Xueyuan Road, Haidian District, Beijing 100083, P. R. China ‡ State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, No. 1, Bei Er Tiao, Zhongguancun, Beijing 100190, P. R. China ¶ Centre for Clean Environment and Energy, Gold Coast Campus, Griffith University, Southport, Queensland 4222, Australia S Supporting Information *
ABSTRACT: Herein, uniform multishelled TiO2 hollow microspheres were synthesized, especially 3- and 4-shelled TiO2 hollow microspheres were synthesized for the first time by a simple sacrificial method capable of controlling the shell thickness, intershell spacing, and number of internal multishells, which are achieved by controlling the size, charge, and diffusion rate of the titanium coordination ions as well as the calcination process. Used as anodes for lithium ion batteries, the multishelled TiO2 hollow microspheres show excellent rate capacity, good cycling performance, and high specific capacity. A superior capacity, up to 237 mAh/g with minimal irreversible capacity after 100 cycles is achieved at a current rate of 1 C (167.5 mA/g), and a capacity of 119 mAh/g is achieved at a current rate of 10 C even after 1200 cycles. KEYWORDS: TiO2, multishelled, hollow microsphere, lithium ion battery, anode, electrode
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this limitation is through purposely designed nano/micro hierarchical structures, which collectively utilize nanoscale building blocks assembled into micron/submicron-sized particles.11,12 Nanostructural units provide enhanced kinetics due to shortened diffusion pathways and large interfacial contact areas, favoring high power densities. Micron-sized particles provide good material stability and afford easy fabrication. Various hierarchically structured TiO2 anodes have been synthesized and used to improve the performance of LIBs.13,14 In addition to hierarchically structured TiO2, recent work using transition metal oxide-based multishelled hollow microspheres demonstrated exceptional performance as anode materials.15,16 These porous and hollow structures possess large interfacial surfaces that allow Li+ to access the nanoparticulate shells from both sides, resulting in a dramatically shortened diffusion path and improved kinetics that are favorable for high rate capacity, better cycle performance, and improved storage capacity. In addition, the porous particles, consisting of concentric nanocrystalline shells, have significant free volume, which can readily adsorb the
ithium ion batteries (LIBs) are one of the most important secondary batteries. In order to enhance capacity and power density, great efforts have been made to develop new electrode materials. Recently, metal oxides such as NiO, Co3O4, and Fe2O3 have been used as electrode materials to improve the capacity of LIBs.1−3 However, these metal oxides often suffer from low power densities (resulting from the low charge/ discharge current densities) and poor cycling performance (due to the irreversible capacity loss). Nanostructured TiO2 has been widely investigated for sensing, environmental remediation, solar energy conversion, and energy storage applications.4−8 As a potential anode in LIBs, nanostructured TiO2 is advantageous due to its low cost and nontoxicity, small volume expansion (
