High-rate metal-free MXene microsupercapacitors on paper substrates

MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors (MSCs). Despite its superior electrochemical performance, only a few studies have reported MXene-based ultrahigh-rate (>1000 mV s(-1)) on-paper MSCs, mainly due to the reduced electrical conductance of MXene films deposited on paper. Herein, ultrahigh-rate metal-free on-paper MSCs based on heterogeneous MXene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)-stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing. With a footprint area of only 20 mm(2), the on-paper MSCs exhibit excellent high-rate capacitive behavior with an areal capacitance of 5.7 mF cm(-2) and long cycle life (>95% capacitance retention after 10,000 cycles) at a high scan rate of 1000 mV s(-1), outperforming most of the present on-paper MSCs. Furthermore, the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal-free on-paper MSC arrays, which can also be simultaneously charged/discharged at 1000 mV s(-1), showing scalable capacitive performance. The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on-paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics.