Rectangular Co3O4 with micro-/nanoarchitectures: charge-driven PDDA-assisted synthesis and excellent lithium storage performance.

For the first time, two dimensional (2D) rectangular Co3O4 with micro-/nanoarchitectures is successfully synthesized by a facile hydrothermal treatment with the assistance of poly(diallyldimethylammonium chloride) (PDDA). Owing to the strong electrostatic interaction, positively charged PDDA molecules are considered as structure directing agents and play a crucial role in the formation of the unique 2D rectangular structure. Material characterization suggests that rectangular Co3O4 is typically endowed with a side length of 3-5 μm and a thickness of around 85 nm, and is composed of numerous interconnected nanocrystals about 15 nm in size. The interconnected nanocrystals provide few trap numbers for the electron transport process and contribute to the mesoporous structure with an average pore size of 18 nm. Thus, the distinctive micro-/nanoarchitectures effectively address the formidable challenges of Co3O4-based anode materials, highly favourable for enhancing lithium ion diffusion, improving electron transport pathways and alleviating volume variation during charge-discharge processes. When rectangular Co3O4 (FST-1) is evaluated as anode material for lithium ion batteries, a high reversible capacity of 1076.9 mA h g(-1) and an excellent first cycle Coulombic efficiency of 88.6% are achieved at a current density of 500 mA g(-1), thus delivering a capacity retention of nearly 100% after 100 cycles. Moreover, when tested at current densities as high as 1000 mA g(-1) and 2000 mA g(-1) for 100 cycles, lithium storage capacities can still be retained at 1020.2 mA h g(-1) and 616.4 mA h g(-1), respectively. Interestingly, by simply varying the reaction conditions or types of positively charged polymers, the polyelectrolyte-assisted hydrothermal route can be successfully extended to synthesize other novel micro-/nanoarchitectures, such as straw-tied-like and urchin-like structures, demonstrating great potential in developing next-generation anode materials for high performance lithium ion batteries.