Cation and anion (de)intercalation into MXene/Perovskite oxides for high-rate intercalation pseudocapacitance

• Hybrid electrode comprising multilayer MXene and oxygen deficient perovskite oxide is designed. • Designed hybrid electrode facilitates both cation and anion intercalation. • Dual ion intercalation helps to build high-rate pseudocapacitance. • High voltage symmetric supercapacitor device of 1.6 V is assembled. Intercalation pseudocapacitance is the next hope for electrochemical energy storage devices to offer high energy density without sacrificing power density. Under intercalation pseudocapacitance, ions (e.g. Li + into T-Nb 2 O 5 , but not limited to cation intercalation only) intercalate into the host materials without phase conversions and no limitations from solid-state diffusion, unlike batteries. Here, a concept of both cations and anions (de)intercalation into the hybrid electrode comprising nanocomposite (MLMO) of MXene (Ti 3 C 2 T x ) and perovskite oxides (LaMnO 3-δ , LMO) are demonstrated. Independently, multilayered MXene and oxygen deficient LMO show cation and anion-based intercalation pseudocapacitance, respectively. During analyzing the electrochemical process through ex situ XPS, it is observed that not only K + ions but O H − ions also (via formation of O 2 − ) (de)intercalate into MLMO and contribute to the total charge storage. Accordingly, MLMO exhibits high capacitance retention (70.82%) even at a high current density of 30 A g −1 (313.6 F g −1 ). Next, a fast-kinetics dual-ion intercalated pseudocapacitive symmetric device with 1.6 V is fabricated which shows a high energy density of 34.1 Wh kg −1 and astonishing power density of 14.51 kW kg −1 . This study sheds light on new dual-ion intercalation chemistry and sets a concrete path for the establishment of high energy storage devices with fast-kinetics. Using the intercalation pseudocapacitance approach, the material is designed to offer both cation and anion de(intercalation) to enhance the charge storage. This work enriches the intercalation chemistry and forms a basis to further develop the high-rate energy storage materials.