Hierarchically structured LiFePO4 was successfully synthesized by ionic liquid solvothermal method. These hierarchically structured LiFePO4 samples were constructed from nanostructured platelets with their (010) facets mainly exposed. To the best of our knowledge, facet control of a hierarchical LiFePO4 crystal has not been reported yet. Based on a series of experimental results, a tentative mechanism for the formation of these hierarchical structures was proposed. After these hierarchically structured LiFePO4 samples were coated with a thin carbon layer and used as cathode materials for lithium-ion batteries, they exhibited excellent high-rate discharge capability and cycling stability. For instance, a capacity of 95% can be maintained for the LiFePO4 sample at a rate as high as 20 C, even after 1000 cycles.
Hierarchically structured LiFePO4 was synthesized by a one-step solvothermal reaction at low temperature using ionic liquid (IL) as a solvent. For a typical process, firstly, IL was pre-heated to 50°C to insure the precursor to be well dissolved. Secondly, CH3COOLi, FeSO4·7H2O and NH4H2PO4 in a mole ratio of 1:1:1 as the precursors were added into 10 mL IL under vigorous stirring for 30 min. Then, the obtained homogeneous solution was transferred into a 20 mL Teflon-lined stainless steel autoclave, and heated at 200°C for 24 h. After cooled to room temperature, the green precipitate was washed thoroughly with water and ethanol for several times, and dried under vacuum at 60°C overnight. To investigate the process of LFP formation, the samples were synthesized with different concentrations of precursor (0.1, 0.2 and 0.4 mmol) and donated as LFP-1, LFP-2 and LFP-3.
Hydrothermal synthesis of carbon-coated LiCoPO4 …
Uniform carbon coating on electrode materials for lithium ion battereis is an effective method to increase the cyclic stability of lithium ion cells. By a novel in situ technique of solid state reaction of carbon precursor pillared metal hydroxides having uniform carbon coating on oxide electrodes such as LiNi1-x-yCoxMnyO2, LiMn2-xN1-xO4, LiNi1-x-yCoxAlyO2, NaNi1-x-yCoxMnyO2, Li2MnO3: LiNi1-x-yCoxMnyO2 has been achieved. A improved cyclic stability of the uniform carbon coated cathode materials compared to that of bare materials for lithium ion battereis is demonstrated