Preparation and characterization of Li2FeP2O7 and its solid solutions as a potential cathode material for lithium-ion battery / Maziidah Hamidi

Lithium ion battery (LIB) has been one of the most studied energy storage system due to its high energy efficiency, long life cycle, high capacity, and relatively high energy density. The need to investigate on a potential improvised LIB is motivated by the depleting fossil fuel and the concerning global warming caused by burning of fossil fuel. However, the mechanism of a LIB involves the chemistry between the LIB components, namely the anode, which is lithium metal for a half-cell, the electrolyte and the cathode. The cathode material of a LIB contributes to the cost effectiveness and performance of these LIBs. Since the introduction of LiCoCh layered oxide in 1996, researchers dedicated efforts into finding a structurally, electronically and electrochemically improved cathode materials including spinel LiMnCU, olivine LiFePO4 and other polyanionic cathodes. Lithium iron pyrophosphate, Li2FeP2O7 has been reported to have a high theoretical capacity of up 220 mAh/g, while the experimental value was reported to be around 110 mAh/g, without any carbon coating or particle downsizing needed making it an interesting subject to explore deeper. However, synthesizing a pure phase Li2FeP2O7 is a challenge, as many reports the existence of secondary phases in the end-product. Low electronic conductivity and high polarization hinders researchers to obtain the optimum capacity of the fabricated LIB. In this work, Li2FeP2O7 was synthesized by using wet ball-milling assisted solid state reaction technique, and the transition metal Fe was then doped by divalent and tetravalent elements to help improve the characteristic and performance of the parent Li2FeP2O7 material.