Metal-Organic Frameworks (MOFs) as Sandwich Coating Cushion for Silicon Anode in Lithium Ion Batteries.

A novel metal-organic framework (MOF) sandwich coating method (denoted as MOF-SC) is developed for hybrid Li-ion battery electrode preparation, in which the MOF films are casted on the surface of a silicon layer and sandwiched in between the active silicon and the separator. The obtained electrodes show improved cycling performance. The areal capacity of the cheap and readily-available micro sized Si treated with MOF-SC can reach 1700 μAh cm-2 at 265 μA cm-2 and maintain at 850 μAh cm-2 after 50 cycles. Beyond the above, the commercial nano sized Si treated by MOF-SC also shows greatly enhanced areal capacity and outstanding cycle stability, 600 μAh cm-2 for 100 cycles without any apparent fading. By virtue of the novel structure prepared by the MOFs, this new MOF-SC structure serves as an efficient protection cushion for the drastic volume change of silicon during charge/discharge cycles. Furthermore this MOF layer, with large pore volume and high surface area, can adsorb electrolyte and allow faster diffusion of Li+ as evidenced by decreased impedance and improved rate performance.