High performance flexible Na hybrid capacitors: from pre-organized triazine crystals/polymers to nitrogen-rich hard carbons
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초록
내용
In order to further improve capacity and rate capability of sodium hybrid capacitors, we develop a versatile synthesis strategy of high performance hard carbon electrode based on pre-organized reactive templates. Shape and size controllable organic crystal of melamine and cyanuric acid hydrogen bonded aggregates (MCA) as reactive templates performs triple duties of (1) structure directing agent, (2) nitrogen source, and (3) porogen. Ratio of MCA to glucose (matrix forming agent) simply controls interlayer spacing, lateral size, and stacking height of graphitic domain, ratio of graphitic to non-graphitic content, nitrogen content, and porosity. This unique structure enables a gravimetric capacity of 389 mAh/g at 250 mA/g, rendering it one of the best hard carbon anode for Na-ion. Hybrid capacitor consisted of the hard carbon anode and activated carbon fiber cathode feature a gravimetric energy density of 220 Wh/kg and a power density of 1000W/kg.