Electrostatic Self-Assembly strategy Stabilizes perylene anode: Assisting Ultra-High-Voltage aqueous potassium ion micro batteries

Aqueous zinc ion microbatteries (AZIMBs) are promising due to its safety and economy. However, the relatively high redox potential (−0.76 V vs. SHE) limitation of zinc metal seriously reduces the voltage of AZIMBs. In contrast, potassium metal has a very low redox potential (−2.93 V vs. SHE), which can provide higher voltage. Thus, we develop the first aqueous potassium ion microbatteries (APIMBs). Since potassium metal is unstable in aqueous electrolytes, we used 3,4,9,10-perylene tetracarboxylic diimide (PTCDI). To improve the stability of traditional perylene anode, the electrostatic self-assembly strategy is used to synthetic PTCDI/MXene anode with ultra-high cycle life (79.94 % capacity retention after 10,000 Galvanostatic Charge-Discharge (GCD) cycles at 10.0 A g −1 ) and low redox potential (−1.20 V vs. Ag/AgCl). The KFeMnHCF cathode with high capacity and voltage is selected to build ultra-high-voltage APIMBs with a voltage up to 2.6 V, excellent energy density (202.81 μWh cm −2 ), power density (7.99 mW cm −2 ), cycle life (89.17 % after 2500 GCD cycles at 5.0 mA cm −2 ), and flexibility (95.13 % under 180°). This work provides a promising direction for developing potassium storage materials and APIBs.