To achieve high energy and power density simultaneously in miniaturized electronic devices, a zinc-ion micro-supercapacitor (ZmSC) is constructed for the first time by integrating a battery-type zinc micro-anode and a capacitor-type carbon nanotube micro-cathode. In the meantime, an electroplating method is developed to in situ replenish the zinc anode when needed without destroying the configuration of the ZmSC, in which the micro-cathode, micro-anode and electrolyte of the ZmSC function as the working electrode, counter electrode and plating solution in the plating process, respectively. This strategy effectively avoids the irreversible consumption of the zinc anode and the fading of the capacitance and cycle life. As a result, the prepared ZmSC exhibits an excellent electrochemical performance, including a high area capacitance of 83.2 mF cm⁻² at 1 mA cm⁻², a high energy density of 29.6 μW h cm⁻² and a high power density of 8 mW cm⁻². After 6000 cycles, the ZmSC shows about 87.4% retention (60.9 mF cm⁻²) of its initial area capacitance at 5 mA cm⁻². Furthermore, a higher capacitance (76 mF cm⁻²) and a longer cycling life are obtained after re-plating the zinc anode. This method features a simple configuration and easy operation, and holds great promise for use in other long cycle life zinc-based microdevices.

Microdevice integrating energy storage with wireless charging could create opportunities for electronics design, such as moveable charging. Herein, we report seamlessly integrated wireless charging micro-supercapacitors by taking advantage of a designed highly consistent material system that both wireless coils and electrodes are of the graphite paper. The transferring power efficiency of the wireless charging is 52.8%. Benefitting from unique circuit structure, the intact device displays low resistance and excellent voltage tolerability with a capacitance of 454.1 mF cm⁻², superior to state-of-the-art conventional planar micro-supercapacitors. Besides, a record high energy density of 463.1 μWh cm⁻² exceeds the existing metal ion hybrid micro-supercapacitors and even commercial thin film battery (350 μWh cm⁻²). After charging for 6 min, the integrated device reaches up to a power output of 45.9 mW, which can drive an electrical toy car immediately. This work brings an insight for contactless micro-electronics and flexible micro-robotics.

At relatively low temperature (e.g., −30 °C), most flexible supercapacitors that work well at room temperature will lose their stretchability due to the poor cold intolerance of conventional electrolytes and the absence of intrinsically stretchable electrodes. Herein, an anti-freezing and highly stretchable supercapacitor (AF-SSC) was fabricated for the first time by one-step in situ growth of polyaniline onto an organohydrogel polyelectrolyte from cross-linked polyacrylamide networks soaked by ethylene glycol/water/H₂SO₄. As no extra stretchable substrates (e.g. elastic fiber, polydimethylsiloxane, rubber, etc.) or predefining stretchable structures (e.g. helical, spring, wrinkle, honeycombed structures etc.) are needed in such a design, the prepared AF-SSC shows a high mechanical stretchability of 200% at −30 °C and can be repeatedly stretched for 100 cycles without significant capacitance loss. Besides, an impressive capacitance retention of 73.1% at −30 °C is achieved when the current density increases by 20 times, which is much higher than those of stretchable supercapacitors based on pseudocapacitive materials that operate at room temperature. Furthermore, the device shows an ultralong lifespan with 91.7% capacitance retention after 100 000 cycles at −30 °C, outperforming all stretchable supercapacitors reported previously. With other merits of high compressibility, strong adhesion, good processability and excellent anti-drying ability, the current device is an ideal power source to drive multi-functional electronic components in real-life scenarios.