Manganese Silicate Nanosheets for Quasi-Solid-State Hybrid Supercapacitors

Recently, manganese silicates have received much attention focusing on their synthesis and electrochemical properties. The synthesis mainly uses the expensive tetraethyl orthosilicate as a Si source and their electrochemical properties are far from the assumption. Herein, we develop a simple route for the synthesis of manganese silicate nanosheets (MS NSs) with excellent electrochemical properties, which are converted from the natural clay mineral magadiite as a silicon source. The structure and morphology characterizations demonstrate that the well-defined MS NSs are constructed using numerous nanosheets with a thickness of about 15 nm. The morphology of the nanosheets provides a huge number of active sites and effectively promotes the full contact between the material and the electrolyte. As a consequence, MS NSs possess a high specific capacitance of 514 F·g–1 at 0.5 A·g–1. The loose nanosheets can also shorten the ion diffusion distance and buffer structural stress during the charge/discharge process. So, the MS NSs exhibit an anticipated rate capability and long-term cycle stability for 98% capacitance after 10,000 cycles. The quasi-solid-state MS NSs//active carbon hybrid supercapacitor (MS NSs//AC HSC) devices deliver an area capacitance of 195 mF·cm–2 at 1 mA·cm–2 and an energy density of 0.88 Wh·m–2 at 2.25 W·m–2 with a superior cycle stability of approximately 100% after 10,000 cycles. The findings not only prove that magadiite can be a silicon source for synthesizing transition metal silicates as electrode materials for SCs but also open a potential application of natural clay minerals.