Synthesis of Lithium Storage Intermetallic Compounds for Rechargeable Battery and their Structural Analysis using X-ray and Neutron

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Recently, lithium storage intermetallic compounds have been extensively investigated because of an increasing demand for higher capacity anode for next generation's rechargeable lithium batteries. To enhance volumetric charge and discharge capacities of the anode, we focused on rare-earth elements due to their large densities, and proposed new materials, such as CeSn_3 and LaSn_3. The volumetric capacities of CeSn_3 and LaSn_3 electrodes were about three times larger than those of graphite one practically used, suggesting an attractive alternative electrode. The electrode, however, exhibited poor reversibility at the first charge-discharge cycle and cyclability as well as other alloy electrodes previously reported.The drawbacks have been overcome by adding lithium to CeSn_3 and LaSn_3 using mechanical alloying. To discuss the improvement of electrode performance for mechanically lithiated CeSn_3 (Li_xCeSn_3) electrodes, the charge-discharge mechanism was investigated by electrochemical measurements and some experiments using X-ray and neutron. As a result, it was found that the Li_xCeSn_3 consists of CeSn_3 and unknown Li-Ce-Sn phases. The CeSn_3 phase of active material appears to be finely dispersed in the Li-Ce-Sn phase which plays a role as an inactive matrix. Therefore, it is considered that the CeSn_3 of small grain size facilitated the escape of lithium which had deeply inserted in the grain and the Li-Ce-Sn matrix released the stress generated at lithium insertion.