High energy Li-ion capacitors with conversion type Mn₃O₄ particulates anchored to few layer graphene as the negative electrode

We report the fabrication of high energy Li-ion capacitors (LICs) using conversion type Mn₃O₄ octahedrons anchored to few layer graphene (Mn₃O₄-G) as the negative electrode with activated carbon (AC) as the positive one. First, the Mn₃O₄-G composite is prepared via a hydrothermal approach using commercially available graphene nanosheets. Li-storage studies of both electrodes (AC and Mn₃O₄-G) are conducted in single electrode/half-cell configuration with metallic Li to assess the mass balance. Prior to the fabrication of LICs, Mn₃O₄-G is pre-lithiated in Swagelok fittings with Li and subsequently paired with the desired loading of AC. The AC/Mn₃O₄-G based LIC delivered a maximum energy density of ∼142 W h kg^-1 with excellent cyclability of 9000 cycles with ∼80% retention. This result certainly provides new avenues for the development of high energy LICs using conversion type negative electrodes rather than traditional insertion type anodes.