Interconnected mesoporous NiO sheets deposited onto TiO2 nanosheet arrays as binder-free anode materials with enhanced performance for lithium ion batteries

Abstract

To meet the requirement of high-performance lithium ion batteries, transition metal oxides have been taken into considerable account to take the place of the commercialized anode material, graphite, which fails to reach a high capacity and satisfactory cycle life in long-term usage. In this study, TiO₂ nanosheet arrays, suffering very little volume changes upon lithium ion intercalation/deintercalation, were synthesized through a facile hydrothermal method as a stable backbone for subsequent chemical bath deposition of interconnected mesoporous NiO sheets with a theoretical capacity of 718 mA h g⁻¹, which is to offset the intrinsically low capacity of TiO₂. The specific surface area for the prepared composites increased by 40.4% and the charge transfer resistance descended remarkably compared with that of pure TiO₂ nanosheet arrays. The unique TiO₂@NiO array structure delivered an average capacity of 420.0 mA h g⁻¹ during 100 cycles at a constant current of 200 mA g⁻¹. The rate performance was improved to be 199.2 mA h g⁻¹ at 1.6 A g⁻¹ and 278.0 mA h g⁻¹ when back to 200 mA g⁻¹, which is better than the pure TiO₂ and NiO. A multitude of factors are responsible for the improved performance, including a larger contact surface between the electrode and electrolyte, a shorter Li ion diffusion pathway within the active material, a higher lithium storage capacity of the overall electrode plus ample open space to accommodate volume variation, which all result from the strategy of effective nanoscale structuring and surface modification. The as-designed batteries are free of binders and conductive additives, which is profitable for mass production and convenient for simplifying the manufacturing protocol.