Surface adsorption and disordering in LiFePO4 based battery cathodes

A recent study [Kang and Ceder, Nature (London) 458, 190 (2009)] suggested that a Li4P2O7-like “fast ion-conducting surface phase” could form on the surfaces of LiFePO4 particles, enabling ultrafast discharging of Li-ion batteries. We demonstrate that these nanoscale surface films exhibit a self-selecting or “equilibrium” thickness, akin to those observed in simpler binary oxides [Luo and Chiang, Annu. Rev. Mater. Res. 38, 227 (2008)]. These observations can be interpreted as a case of coupled prewetting and premelting. Similar nanoscale intergranular films are also observed. These nanoscale interfacial phenomena can be utilized to tailor nanoparticles for battery and many other applications.

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