LNMCO/C сore/shell nanoparticles for Li-ion batteries

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During the past decades lithium-ion batteries have been predominating in the portable energy storage devices due to much higher electrochemical characteristics compared to other rechargeable battery systems. Nowadays Li-ion batteries are being required not only for application in mobile phone and portable computers but also in new applications such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and electric vehicles (EV) and in other promising areas.

Low thermal stability, high cost and toxicity of the commercial material LiCoO2 forced many researchers to search for alternative cathode material for Li-ion batteries. It was found that the layered lithium transition metal oxide LiaNibMncCodO2 with the structure of the α-NaFeO2 type is more attractive because it has higher capacity (> 250mAh/g), electric conductivity and stable cyclic performance.

There are several preparation methods of cathode materials: solid state reaction, microwave heating method, co-precipitation of hydroxides or insoluble salts, cryochemical and others. However, all of them have inherent disadvantages, namely, duration of the process (> 24 hours); high process temperature (> 800 °C); insufficient homogenization; high particle size (0,3 - 20μm) and wide particle size distribution; and still low capacity and electric conductivity of the obtained materials.

Our research group developed a new method to synthesize cathode nanoparticulated (<100 nm) core/shell-structured LNMCO/C with metal oxides in the core. The shell being a carbon layer, high electric conductivity and material stability of the material is provided. By means of transmission electron microscopy it was shown that the thickness of the carbon layer doesn’t exceed 5 nm, while the average size of crystallites is less than 100 nm.

 

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