Effects of hexamethylenetetramine as an electrolyte additive on elevated temperature performance of graphite/LiMn2O4 batteries

Spinel LiMn2O4-based lithium-ion batteries are widely applied in electric two-wheeler and low-speed vehicles due to their low cost and low toxicity. Nevertheless, the Mn deposition at the anode originated from Mn dissolution of LiMn2O4 causes a poor elevated temperature cycle life of graphite/LiMn2O4 batteries. Herein, a graphite/LiFePO4 cell with specific Mn2+ added in the electrolyte is provided as an efficient evaluation method to research Mn2+ deposition. Besides, an effective strategy by adding a ligand hexamethylenetetramine (HMTA) as an electrolyte additive is proposed to prevent Mn2+ depositing. HMTA effectively “locks in” Mn2+ through strong coordination, as confirmed by Raman spectroscopy and density functional theory (DFT) calculations. Moreover, the CV and XPS results indicate that the adsorption of HMTA is able to significantly inhibit side reactions at the anode/electrolyte interface. By adopting this strategy, the capacity retention of graphite/LiMn2O4 cell is enhanced from 68.9