Hydrothermal synthesis of Li2MnSiO4: Mechanism and influence of precursor concentration on electrochemical properties

The effect of the precursor concentration on the electrochemical properties of hydrothermally synthesized Li2MnSiO4 is investigated. The synthesis mechanism is investigated by analyzing the chemical reaction as a function of reaction time. Results show that Li2MnSiO4 is synthesized by a dissolution-recrystallization mechanism through an intermediate Mn(OH)2 phase. Smaller particles produced from higher concentration precursor solution. Li2MnSiO4 with smaller particle size shows larger initial discharge capacity than that of Li2MnSiO4 with larger particle size which are synthesized from lower concentration precursor solution. A maximum initial charge capacity of 323 mAh g−1 and discharge capacity of 177 mAh g−1 are achieved through hydrothermal synthesis using a 2.1 M solution, while it shows serious capacity fading. Li2MnSiO4 synthesized from 2.1 M solution shows 32% of capacity retention after 20 cycles. Smaller particle size of Li2MnSiO4 can induce more serious side reaction with electrolyte due to its larger specific surface area, which results in structural instability during charge-discharge tests.