Engineering single crystalline Mn sub(3)O sub(4) nano-octahedra with exposed highly active {011} facets for high performance lithium ion batteries

• Published in: Nanoscale 2014-05, Vol.6 (12), p.6819-6827
• Main Authors: Huang, Shao-Zhuan, Jin, Jun, Cai, Yi, Li, Yu, Tan, Hai-Yan, Wang, Hong-En, Van Tendeloo, G, Su, Bao-Lian
• Format: Article
• Language: English
• Subjects: Charge; Charge density; Cycles; Electrochemical analysis; Electrolytes; Exposure; Lithium-ion batteries; Nanostructure
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c4nr01389a

Well shaped single crystalline Mn sub(3)O sub(4) nano-octahedra with exposed highly active {011} facets at different particle sizes have been synthesized and used as anode materials for lithium ion batteries. The electrochemical results show that the smallest sized Mn sub(3)O sub(4) nano-octahedra show the best cycling performance with a high initial charge capacity of 907 mA h g super(-1) and a 50th charge capacity of 500 mA h g super(-1) at a current density of 50 mA g super(-1) and the best rate capability with a charge capacity of 350 mA h g super(-1) when cycled at 500 mA g super(-1). In particular, the nano-octahedra samples demonstrate a much better electrochemical performance in comparison with irregular shaped Mn sub(3)O sub(4) nanoparticles. The best electrochemical properties of the smallest Mn sub(3)O sub(4) nano-octahedra are ascribed to the lower charge transfer resistance due to the exposed highly active {011} facets, which can facilitate the conversion reaction of Mn sub(3)O sub(4) and Li owing to the alternating Mn and O atom layers, resulting in easy formation and decomposition of the amorphous Li sub(2)O and the multi-electron reaction. On the other hand, the best electrochemical properties of the smallest Mn sub(3)O sub(4) nano-octahedra can also be attributed to the smallest size resulting in the highest specific surface area, which provides maximum contact with the electrolyte and facilitates the rapid Li-ion diffusion at the electrode/electrolyte interface and fast lithium-ion transportation within the particles. The synergy of the exposed {011} facets and the smallest size (and/or the highest surface area) led to the best performance for the Mn sub(3)O sub(4) nano-octahedra. Furthermore, HRTEM observations verify the oxidation of MnO to Mn sub(3)O sub(4) during the charging process and confirm that the Mn sub(3)O sub(4) octahedral structure can still be partly maintained after 50 discharge-charge cycles. The high Li-ion storage capacity and excellent cycling performance suggest that Mn sub(3)O sub(4) nano-octahedra with exposed highly active {011} facets could be excellent anode materials for high-performance lithium-ion batteries.