Preparation And Lithium Storage Properties Of Mn-based Mixed Transition Metal Oxide Anode Materials For Lithium-ion Batteries

Rechargeable lithium-ion batteries ?LIBs? are the dominant power sources for applications in portable consumer electronics, electric vehicles ?EVs? and hybrid electric vehicles ?HEVs? because of their high energy densities, low self-discharge property and long cycle life. However, current lithium-ion battery technologies are still far from satisfactory to meet the increasingly diverse ranges of applications. Among all components for LIBs, anode materials are one of the key factors to influence the cycling stability and specific capacity of the battry. The graphite electrode with low capacity is hard to meet consumer demand for capacity and other properties at now. Therefore, the research and development of novel anodes with large specific capacity have great significance, and is also the main purpose of this paper. It is of great importance to explore novel anodes with large specific capacity. The main points are summarized as follows:1. MC₂O₄·xH₂O?M=Zn, Mn? rod-shaped precursors was synthesized via a innovative co-precipitation reaction, which takes place in ethanol/water mixed solvent system,using oxalic acid as precipitating agent. And one-dimensional spinel ZnMn2O4 products with micro-nano structure were obtained after calcining the oxalate precursors.Experiment results showed porous ZnMn2O4 nanorods were assembled by granular.Compared with non-uniform granular products, one-dimensional ZnMn2O4 anode material with micro-nano structure exhibits excellent electrochemical performance. It delivers a high discharge capacity of 1741.5 mAh g-1 at frist discharge, and a high discharge capacity of 512.8 and 374.6 mAh g-1 with high capacity retention of 81.3%and 75.5% after 300 cycles at 0.5 and 1 C rate. The unique micro-nanostructured architecture favors for shortening the electron and lithium diffusion lengths, facilitating the efficient diffusion of electrolyte into the inner region of the electrode and accomodating the volume change associated with repeated Li+ charge and discharge process.2. The co-precipitation reaction in ethanol/water mixed solvent system was demonstrated to be a general method for synthesizing one dimensional micro-nano structured Mn-based mixed transition metal oxide anode materials. A series of Mn-based mixed transition metal oxides, including ZnMnO3 and AMn2O4?A=Ni,Fe, Cu,Mg? have been successfully prepared. Test results show that most of one-dimensional micro-nano structure manganese anode materials with good lithium storage properties were synthesised by the general method. Among them, ZnMnO3 and NiMn2O4 anodes exhibit better lithium storage property. ZnMnO3 anodes can deliver a high frist discharge capacity of 581.6 mAh g-1 and a high discharge capacity of 382.9 mAh g-1 with good capacity retention of 65.8% after 300 cycles at 0.5 C rate. NiMn2O4 anodes can deliver a high frist discharge capacity of 704.2 mAh g-1 and a discharge capacity of 292.9 mAh g-1 after 200 cycles at 0.5 C rate. And FeMn2O4 anodes showed good cycle performance and deliver a high discharge capacity of 1017.3 mAh g-1 after 500 cycles at 0.5 C rate with good coulomb efficiency of more than 99%.3. Fe₂O₃ hierarchical arrays and Fe₂O₃ nanorod arrays have been prepared by in-situ hydrothermal chemical oxidation method and hydrothermal deposition approach, respectively. Their wettability and electrochemical performances have been investigated. The results showed that, compared with Fe₂O₃ nanorod array film,Fe₂O₃ hierarchical array film exhibits better wettability performance. The contact angle of Fe₂O₃ hierarchical array film becomes smaller with the surface free energy increasing due to change of polar force. The contact angle of Fe₂O₃ nanorod array film becomes larger with the surface free energy decreasing due to change of dispersion force. The anodes which are direct growth on the substrate have more excellent electrochemical performance. Fe₂O₃ hierarchical array film can deliver a high discharge capacity of 512.8 and 374.6 mAh g-1 with great capacity retention of 81.3% and 75.5%after 300 cycles at 0.5 and 1 C rate. And Fe₂O₃ hierarchical array film exhibits better electrochemical performance than Fe₂O₃ nanorod array film due to its better contact with the electrolyte.