Lithium-sulfur (Li-S) battery is considered as a promising energy storage system due to its ultrahigh theoretical energy density of 2,600 Wh·kg⁻¹. Redox mediation strategies have been proposed to promote the sluggish sulfur redox kinetics. Nevertheless, the applicability of redox mediators in practical high-energy-density Li-S batteries has seldomly been manifested. In this work, 5,7,12,14-pentacenetetrone (PT) is proposed as an effective redox mediator to promote the sulfur redox kinetics under practical working conditions. A high initial specific discharge capacity of 993 mAh·g⁻¹ is achieved at 0.1 C with high-sulfur-loading cathodes of 4.0 mg_S·cm⁻² and low electrolyte/sulfur (E/S) ratio of 5 μL·mg_S⁻¹. More importantly, practical Li-S pouch cells with the PT mediator realize an actual initial energy density of 344 Wh·kg⁻¹ and cycle stably for 20 cycles wih a high capacity retention of 88%. This work proposes an effective redox mediator and further verifies the redox mediation strategy for practical high-energy-density Li-S batteries.

Oxygen reduction reaction (ORR) constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells. However, the kinetics of ORR is very sluggish and thus high-performance ORR electrocatalysts are highly regarded. Despite recent progress on minimizing the ORR half-wave potential as the current evaluation indicator, in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized. In this paper, a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation. Independent parameters regarding exchange current density, electron transfer number, and electrochemical active surface area can be respectively determined following the proposed method. This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.

Aqueous zinc–air batteries (ZABs) are highly regarded as a promising electrochemical energy storage device owing to high energy density, low cost, and intrinsic safety. The employment of seawater to replace the currently used deionized water in electrolyte will bring great economic benefits and broaden the application occasions of ZABs. However, ZABs using seawater-based electrolyte remain uninvestigated without an applicable cathode electrocatalyst or a successful battery prototype. Herein, seawater-based electrolyte is successfully employed in ZABs with satisfactory performances. The influence of chloride anions on the cathode electrocatalytic reactivity and battery performance is systemically investigated. Both noble-metal-based and noble-metal-free electrocatalysts are applicable to the chloride-containing alkaline electrolyte. Further evaluation of ZABs with seawaterbased electrolyte demonstrates comparable battery performances with the conventional electrolyte in terms of polarization, capacity, and rate performance. This study demonstrates a successful prototype of seawater-based ZABs and enlightens the utilization of natural resources for clean and sustainable energy storage.