Electrochemically Induced Crystallite Alignment of Lithium Manganese Oxide to Improve Lithium Insertion Kinetics for Dye-Sensitized Photorechargeable Batteries

The insertion of lithium into lithium manganese oxide spinel (LiMn2O4 (LMO) to Li2Mn2O4 (L2MO)) was used to store light energy as a form of chemical energy in a dye-sensitized photorechargeable battery (DSPB). Herein, we investigate the effect of crystallite size of LMO on DSPB performance. The crystallite size of graphene-wrapped sub-micrometer-sized LMO (LMO@Gn) was tuned electrochemically from 26 to 34 nm via repeated LMO-to-L2MO transitions. The different crystallite orientations in LMO@Gn particles were ordered in an identical direction by an electric stimulus. The LMO@Gn having a 34 nm crystallite size (L-34 and L-34*) improved DSPB performances in dim light, compared with the smaller-crystallite LMO@Gn (L-26). The overall energy efficiency (eta(overall)) of 13.2%, higher than ever reported, was achieved by adopting the fully crystallized and structure-stabilized LMO@Gn (L-34*) for DSPB. The phase transition between the cubic and tetragonal forms during the LMO-to-L2MO reaction was suspected to be responsible for the structural ordering.

Automated summary

By investigating the effect of crystallite size and structure of LMO on DSPB performance, it was found that fully crystallized and structure-stabilized LMO@Gn significantly improved the performance of DSPB, especially under low light conditions.