Integrated Uniformly Microporous C4 N/Multi-Walled Carbon Nanotubes Composite Toward Ultra-Stable and Ultralow-Temperature Proton Batteries

A Long-Range Planar Polymer with Efficient π-Electron Delocalization for Superior Proton Storage

Due to the unique "Grotthus mechanism", aqueous proton batteries (APBs) are promising energy devices with intrinsic safety and sustainability. Although polymers with tunable molecular structures are ideal electrode materials, their unsatisfactory proton-storage redox behaviors hinder the practical application in APB devices. Herein, a novel planar phenazine (PPHZ) polymer with a robust and extended imine-rich skeleton is synthesized and used for APB application for the first time. The long-range planar configuration achieves ordered molecular stacking and reduced conformational disorder, while the high conjugation with strong π-electron delocalization optimizes energy bandgap and electronic properties, enabling the polymer with low proton diffusion barriers, high redox activity, and superior electron affinity. As such, the PPHZ polymer as an electrode material exhibits fast, stable, and unrivaled proton-storage redox behaviors with a large capacity of 273.3 mAh g-1 at 0.5 A g-1 (1 C) in 1 M H2SO4 electrolyte, which is the highest value among proton-inserted electrodes in aqueous acidic electrolytes. Dynamic in situ techniques confirm the high redox reversibility upon proton uptake/removal, and the corresponding protonation pathways are elucidated by theoretical calculations. Moreover, a pouch-type APB cell using PPHZ electrode exhibits an ultralong lifespan over 30 000 cycles, further verifying its promising application prospect.

Searching High-Potential Dihydroxynaphthalene Cathode for Rocking-Chair All-Organic Aqueous Proton Batteries

The lack of acid-proof high-potential cathode largely limits the development and competitiveness of proton batteries. Herein, the authors systematically investigated six dihydroxynaphthalenes (DHNs) and found that 2,6-DHN delivered the best cathode performance in proton battery with the highest redox potential (0.84 V, vs SHE) and a specific capacity of 91.6 mAh g-1 at 1 A g-1 . In situ solid-state electropolymerization of DHNs is responsible for the voltage and capacity fading of DHNs, and 2,6-DHN's excellent electrochemical performance is derived from its high polymerization energy barrier. By compounding with rGO, the 2,6-DHN/rGO electrode can maintain a specific capacity of 89 mAh g-1 even after 12 000 cycles at 5 A g-1 . When it is paired with the 2,6-dihydroxyanthraquinone (DHAQ) anode, the assembled rocking-chair all-organic proton battery exhibited a high cell voltage of 0.85 V, and excellent energy/power densities (70.8 Wh kg-1 /850 W kg-1 ). This study showcases a new-type high-potential proton-containing organic cathode and paves the way for constructing a high-voltage rocking-chair proton battery. Also, in situ solid-state electropolymerization will inspire the further study of phenol-based small-molecule electrodes.

Modifying Electronic Structure of Bismuth Telluride Through S Doping and Te Vacancy Engineering for Enhanced Zn-Ion Storage Ability in Aqueous Zn-proton Hybrid Ion Batteries

Bismuth chalcogenides are used as cathode materials in Zn-proton hybrid ion batteries, which exhibit an ultraflat discharge plateau that is favorable for practical applications. Unfortunately, their capacity is not competitive, and their charge storage mechanisms are ambiguous, both of which hinder their further development. In this study, S-doped Bi2 Te3- x (SBT) nanosheets are prepared by tellurizing a Bi2 O2 S precursor using a hydrothermal process. As revealed by density functional theory analyses, the S dopant and its induced Te vacancies can distinctly manipulate the electronic structure of SBT, resulting in decent electrical conductivity and more negative adsorption energy to Zn2+ . These advantages boost the Zn2+ storage ability of SBT materials. Consequently, compared with defect-free Bi2 Te3 , the SBT cathodes have superior specific capacity, rate capability, and cycling stability.