Low-temperature, low-pressure Zn-ion hybrid supercapacitor in extreme near-space application.

The development and utilization of airspace, especially near-space particularly rely on power units with superior tolerance in low-temperature and low-pressure environments to output a stable energy supply. Here we propose a strategy towards low-temperature, low-pressure Zn-ion hybrid supercapacitor based on a weakly hydrogen-bonded electrolyte and a hyacinth-shaped Ti₂CT_x MXene@CC cathode with hierarchical bridge-linked structure, which synergistically reduces the internal resistance of the device and enables the assembled supercapacitor showing a good low-temperature resistance while combining low-gas-voltage safety. The ACN additive weakens the hydrogen bond between water molecules and reshapes the solvation structure of Zn²⁺, thus reducing the ion transfer resistance and achieving a reversible Zn/Zn²⁺ chemical reaction. The bridge-linked hierarchical structure of the hyacinth-shaped Ti₂CT_x MXene@CC cathode provides a rich conductive network and optimizes the ion diffusion path, which reduces the ion diffusion resistance. At -40 °C, the assembled device can still achieve an area specific capacitance of 64.0 mF cm^-2 at a scan rate of 500 mV s^-1, and long-term stability after 20 000 cycles at a current density of 20 mA cm^-2. An integrated temperature and pressure sensing system driven by the supercapacitor successfully realizes the monitoring of atmospheric indicators in extreme environments, providing new ideas for auxiliary power units in airspace and near-space.