Electrochemical proton storage provides high energy, fast kinetics, safety, and environmental friendliness for grid‐scale energy storage. However, the development of pseudocapacitive proton supercapacitors with fast chargeability and high stability is still challenging because of the unclear electrochemical reaction mechanism and unsuitable construction strategy. Here it is shown that a multi‐metallic Prussian blue analog—Cu0.82Co0.18HCF, which possesses enhanced electronic structure and ion transport path—can intercalate/de‐intercalate large amounts of proton at high rates. Ion‐induced transformation of magnetism, fast solid‐state proton transport, and reversible insertion/de‐insertion of protons lead to extremely excellent rate capacities and cycling stability for proton storage. An asymmetric pseudocapacitive proton supercapacitor (Cu0.82Co0.18HCF//WO3·nH2O) is fabricated with a voltage window of 1.7 V, delivering a maximum energy density of 35 Wh kg−1 and an energy density of 22 Wh kg−1 at a high power density of 26 kW kg−1. Combining systematical material design and mechanism study, this work not only broadens the preparation of electrode materials but also brings light to the construction of high‐performance devices for efficient proton storage.

Aqueous proton batteries/pseudocapacitors are promising candidates for next‐generation electrochemical energy storage. However, their development is impeded by the lack of suitable electrode materials that facilitate rapid transport and storage of protons. Herein, an open‐layered hydrous tungsten oxide (WO3·nH2O) with larger layer spacing from Aurivillius Bi2WO6 via ion etching is proposed. Particularly, the WO3·nH2O electrode possesses a unique multi‐level nanostructure and presents superior rate performance (254 F g−1 at 1000 mV s−1, surpassing most carbon‐based electrode materials known). In situ X‐ray Diffraction combined with crystallography study demonstrate that the open layered structure with negligible structural strain enables fast and reversible (de)intercalation of protons during electrochemical reaction. Furthermore, a full proton pseudocapacitor (Prussian blue analogues//WO3·nH2O) operating in a wide temperature range from −40 to 25 °C is fabricated. This device can deliver 70% of the room‐temperature capacitance and stably cycle with negligible capacitance fading over 5000 cycles even in the solid‐phase electrolyte at −20 °C. This study provides a valuable strategy to design electrode materials with layered structures for the development of high‐performance aqueous proton batteries/pseudocapacitors at low temperatures.

The sluggish ionic transport in thick electrodes and freezing electrolytes has limited electrochemical energy storage devices in lots of harsh environments for practical applications. Here, a 3D‐printed proton pseudocapacitor based on high‐mass‐loading 3D‐printed WO3 anodes, Prussian blue analog cathodes, and anti‐freezing electrolytes is developed, which can achieve state‐of‐the‐art electrochemical performance at low temperatures. Benefiting from the cross‐scale 3D electrode structure using a 3D printing direct ink writing technique, the 3D‐printed cathode realizes an ultrahigh areal capacitance of 7.39 F cm−2 at a high areal mass loading of 23.51 mg cm−2. Moreover, the 3D‐printed pseudocapacitor delivers an areal capacitance of 3.44 F cm−2 and excellent areal energy density (1.08 mWh cm−2). Owing to the fast ion kinetics in 3D electrodes and the high ionic conductivity of the hybrid electrolyte, the 3D‐printed supercapacitor delivers 61.3% of the room‐temperature capacitance even at −60 °C. This work provides an effective strategy for the practical applications of energy storage devices with complex physical structure at extreme temperatures.