Aqueous electrochemical energy storage (EES) devices have attracted considerable attention due to their advantages of low cost and high safety. However, the freeze of aqueous electrolytes usually causes the dramatic loss of ionic conduction capacity, thereby seriously restricting the low‐temperature application of such EES devices. Herein, different from traditional frozen electrolytes, a Zn(ClO4)2 salty ice with superior ionic conductivity (1.3 × 10−3 S cm−1 even at −60 °C) is discovered. It is attributed to the unique 3D ionic transport channels inside such ice, which enables the fast transport of both Zn2+ ions and ClO4− ions inside the ice at low temperatures. Using this Zn(ClO4)2 salty ice as an electrolyte, as‐built zinc ion hybrid capacitor is able to work even at −60 °C (with 74.2% of the room temperature capacity), and exhibits an ultra‐long cycle life of 70 000 cycles at low temperature. This discovery provides a new insight for constructing low‐temperature EES devices using salty ices as electrolytes.
Although sodium-ion batteries (SIBs) and potassiumion batteries (PIBs) are promising prospects for next-generation energy storage devices, their low capacities and inferior kinetics hinder their further application. Among various phosphate-based polyanion materials, titanium pyrophosphate (TiP 2 O 7 ) possesses outstanding ion transferability and electrochemical stability. However, it has rarely been adopted as an anode for SIBs/PIBs due to its poor electronic conductivity and nonreversible phase transitions. Herein, an ultrastable TiP 2 O 7 with enriched oxygen vacancies is prepared as a SIB/PIB anode through P-containing polymer mediation carbonization, which avoids harsh reduction atmospheres or expensive facilities. The introduction of oxygen vacancies effectively increases the pseudocapacitance and diffusivity coefficient and lowers the Na insertion energy barrier. As a result, the TiP 2 O 7 anode with enriched oxygen vacancies exhibits ultrastable Na/K ion storage and superior rate capability. The synthetic protocol proposed here may offer a simple pathway to explore advanced oxygen vacancy-type anode materials for SIBs/PIBs.
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