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.
In recent years, the metal ion hybrid micro-supercapacitor (MSC) comprised of the battery-type Faradaic cathode based electrode and capacitor-type anode based electrode, can realize both high power and energy density, which becomes one of the most hottest areas of energy device. Herein, we demonstrated a zinc-ion hybrid micro-supercapacitor (ZIHMSC) by designing a Ti 3 C 2 T x MXene based electrode as capacitor-type anode and vanadium pentoxide (V 2 O 5 ) based electrode as battery-type cathode. In addition, the polyacrylamide (PAM) hydrogel where ZnSO 4 dissolved was chosen as the electrolyte, which effectively avoids the security risks, unlike other hybrid MSC based on the organic electrolytes. Meanwhile, the flexible ZIHMSC also exhibits well electrochemical properties, displaying a remarkable capacitance (129 mF cm −2 under 0.34 mA cm −2 ), high energy density (48.9 μWh cm −2 at 673 μW cm −2 ) and well-cycle stability (retaining ~ 77% capacitance after 10,000 cycles). This work supports a prospective routine for constructing the new-generation flexible micro-energy storage systems.
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