Futuristic anode materials for energy storage applications

Lithium-ion batteries (LIBs) with outstanding energy and power density have been extensively studied in recent years and are most suitable for electric vehicles, stationary and storage applications. More recently, sodium, one of the most abundant elements on earth, exhibiting similar physicochemical properties as lithium has been gaining increasing more attention towards the development of sodium nd storage appl physicochemic sodium-ion batteries (SIBs). Group IV alloy-based elements (Si, Sn, Ge) attract more attention in energy storage applications, particularly with respect to LIBs and SIBs, due to their fast lithium or sodium storage capacities, which usually exceed one lithium or sodium per atom of alloy elements (e.g. Li15Si4 or Li4.4Sn). However, the main drawback of this system is that large volume variation limits the cycle-life of such electrodes. Thus to overcome this problem ternary or mixed metal oxide derivatives are being investigated in LIBs and SIBs. In particular, fabrication of mixed transition metal oxides (MTMOs) has been considered as a promising alternate to hard carbon anodes due to their high capacity, realized through conversion reaction of oxides with Na (2 or three times higher) and the significantly low electrode reduction potential. In addition, the conversion anode will form new phases during cycling, which are responsible for the high reversibility and structural stability. In other words, Na2O formed during first sodiation could act as a buffering matrix to accommodate the volume changes and play a key role in preventing the agglomeration of metal nanoparticles. Surface modification with carbonaceous materials is widely considered as a facile approach to buffer the volume expansion and particle aggregation and to enhance the electric conductivity of the mixed metal oxides. These unique features in combination with the easy-to-adopt materials synthesis and customised formulation-cumdesign for such materials have triggered a remarkable attention in energy storage applications. (Image Courtesy: Olabi, A. G., et al. "Critical review of energy storage systems." Energy (2020): 118987