Alleviating self-discharge of printed interdigital supercapacitor based on conjugatedly configured pairs of pre-sodiated manganese oxide

Self-discharge has long hindered the wider application of interdigital electrochemical double layer capacitors (EDLCs). This work reports a conjugatedly configured interdigital supercapacitor based on pairs of pre-sodiated manganese oxides, forming a NaxMnO2 vs. Na1-xMnO2 configuration. Theoretically, the working process involves the consumption of charge carrier on one electrode and replenishment of the same type of charge carrier on the counter electrode, which results in similar reaction environment and reduced concentration gradient at the electrode/electrolyte interface for both the cathode and the anode. Experimentally, a direct ink writing method is used to manufacture the interdigital device with high loading (115.0 +/- 5.0 mg cm-2) and easy operation. As a result, the conjugated interdigital supercapacitors based on NaxMnO2 vs. Na1-xMnO2 exhibits approximately 16.8 times longer duration for the device to loss 50 % of its voltage compared to AC/AC (activated carbon) symmetric interdigital supercapacitors upon aging. Our strategy for suppressing self-discharge based on device-level design is anticipated to be generally applicable for various interdigital devices.