Low Temperature Preparation and Electrochemical Properties of LiFeSi2O6

The growing demand for Li-ion batteries requires the development of inexpensive materials that can be made in a sustainable fashion. Here we report a new low-temperature preparation for and the first electrochemical characterization of LiFeSi₂O₆, a hugely Earth-abundant, rock-forming mineral. We have found that LiFeSi₂O₆ undergoes a reversible electrochemical reaction against Li centered around 2 V with capacities near 60% of the theoretical maximum.
However, an extremely slow rate of cycling (C/200) or small particle size of LiFeSi₂O₆ is required to obtain a reasonable capacity, which indicates that Li⁺-(de)insertion in LiFeSi₂O₆ is kinetically hindered. To understand the origin of this kinetic hindering, we conducted Ritveld refinement of the atomic displacement parameters of LiFeSi₂O₆ against the neutron diffraction data obtained from the HIPD beamline at Los Alamos National Laboratory. The results not only allowed us to clarify the preferred diffusion pathway for Li⁺ ions in LiFeSi₂O₆, but also enabled us to link the kinetic hindering in the material to its structural rigidity, which is indicated by the flat-shaped atomic displacement sphere of oxygen atoms along the polyhedra linkages in the LiFeSi₂O₆ structure.