High-throughput fabrication and testing of lithium battery materials

Abstract

A new method for the high-throughput discovery of cathode materials for lithium ion batteries has been developed. The novelty is in the method of separating the synthesis and electrode fabrication steps, which has resulted in high quality electrochemical data and standard deviation in results of approximately 6 %. This method has then been used to investigate several material systems. Investigations into LiFePC>4 have shown that sol-gel preparations with a sucrose to phosphoric acid ratio of 0.22 give the highest initial capacities and best rate performance. The rate capability of this material was found to be enhanced by ball milling the as synthesised material for 1 h. Further improvements in rate performance could be achieved when Mg was used as a dopant on the Fe site. Investigations of LiFei.xMnxPO4 showed that the capacity is significantly reduced as x is increased due to a well documented reduction in conductivity. The reaction mechanism of the Fe2+/Fe3+ redox couple was seen to change from 1 phase to a 2 phase type on increasing x. On further investigation of the LiMnPO4 material Mg doping was found to alleviate the conductivity limitations and at a rate of C/7 ~60 mA h g"1 was observed. To further validate the method and to demonstrate the versatility of the PoSAT technique in terms of which materials can be investigated, research into LiCoi-x-yNixMnyO2 is also presented. Using a novel approach to obtain thermally graded arrays optimal synthesis temperature and precursor salts were found for LiCoo.33Nio33Mno.33O2. The material prepared from an aqueous mixed metal nitrate solution at 700 °C was found to show a high initial capacity -200 mA h g'1 and acceptable cyclabijity. Using this synthesis method, investigations into the ternary system LiCoi-x-yNixMnyO2 were also undertaken. It was found that in materials containing y>0.5 electrochemical performance similar to LiMn2O4 was observed. The highest performance materials were seen in samples containing roughly equal (>25 % of each) amounts of each metal.

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