Oxygen vacancies refilling and potassium ions intercalation of δ-manganese dioxide with high structural stability toward 2.3 V high voltage asymmetric supercapacitors

Intercalation chemistry engineering strategy enabled high mass loading and ultrastable electrodes for High-Performance aqueous electrochemical energy storage devices

Aqueous electrochemical energy storage devices (AEESDs) are considered one of the most promising candidates for large-scale energy storage infrastructure due to their high affordability and safety. Developing electrodes with the merits of high energy density and long lifespan remains a challenging issue toward the practical application of AEESDs. Research attempts at electrode materials, nanostructure configuration, and electronic engineering show the limitations due to the inherent contradictions associated with thicker electrodes and ion-accessible kinetics. Herein, we propose an intercalation chemistry engineering strategy to enhance the electrolyte ion (de)intercalation behaviors during the electrochemical charge-discharge. To validate this strategy, the prototypical model of a high-mass-loading MnO2-based electrode is used with controlled intercalation of Na+ and H2O. Theoretical and experimental results reveal that an optimal content of Na+ and H2O on the MnO2-based electrode exhibits superior electrochemical performance. Typically, the resultant electrode exhibits an impressive areal capacitance of 1551 mF/cm2 with a mass loading of 9.7 mg/cm2 (at 1 mA/cm2). Furthermore, the assembled full-cell with obtained MnO2-based electrode delivers a high energy density of 0.12 mWh/cm2 (at 20.02 mW/cm2) and ultra-high cycling stability with a capacitance retention percentage of 89.63 % (345 mF/cm2) even after 100,000 cycles (tested over 72 days).

MoO2 Nanoclusters Embedded in Hierarchical Nitrogen Doped Carbon Nanoflower as Electrocatalytic Mediators in Aqueous Zinc-Tellurium Batteries: Enhancing Electrochemical Kinetics of Tellurium Redox Reaction

Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising devices for large-scale energy storage systems owing to their high theoretical capacity, environmental friendliness, and safety. However, the ionic intercalation or surface redox mechanisms in conventional cathode materials generally result in unsatisfactory capacities. Conversion-type aqueous zinc-tellurium (Zn-Te) batteries have recently gained widespread attention owing to their high theoretical specific capacities. However, it remains an enormous challenge to improve the slow kinetics of the aqueous Zn-Te batteries. Here, MoO2 nanoclusters embedded in hierarchical nitrogen-doped carbon nanoflower (MoO2 /NC) hosts are successfully synthesized and loaded with Te in aqueous Zn-Te batteries. Benefitting from the highly dispersed MoO2 nanoclusters and hierarchical nanoflower structure with a large specific surface area, the electrochemical kinetics of the Te redox reaction are significantly improved. As a result, the Te-MoO2 /NC electrode exhibits superior cycling stability and a high specific capacity of 493 mAh g-1 at 0.1 A g-1 . Meanwhile, the conversion mechanism is systematically explored using a variety of ex situ characterization methods. Therefore, this study provides a novel approach for enhancing the kinetics of the Te redox reaction in aqueous Zn-Te batteries.