Lithium–sulfur (Li–S) batteries are considered as one of the most promising next-generation energy storage devices because of their ultrahigh theoretical energy density beyond lithium-ion batteries. The cycling stability of Li metal anode largely determines the prospect of practical applications of Li–S batteries. This review systematically summarizes the current advances of Li anode protection in Li–S batteries regarding both fundamental understanding and regulation methodology. First, the main challenges of Li metal anode instability are introduced with emphasis on the influence from lithium polysulfides. Then, a timeline with 4 stages is presented to afford an overview of the developing history of this field. Following that, 3 Li anode protection strategies are discussed in detail in aspects of guiding uniform Li plating/stripping, reducing polysulfide concentration in anolyte, and reducing polysulfide reaction activity with Li metal. Finally, 3 viewpoints are proposed to inspire future research and development of advanced Li metal anode for practical Li–S batteries.

Lithium-sulfur (Li-S) batteries are deemed as high-promising next-generation energy storage technique due to their ultrahigh theoretical energy density, where the sulfur cathodes with high specific capacity guarantee the energy density advantage and directly determine the battery performances. After decades of exploration, the most promising sulfur cathodes are sulfur/carbon composite (S/C) cathodes and sulfurized polyacrylonitrile (SPAN) cathodes. In this manuscript, recent advances on S/C and SPAN cathodes in Li-S batteries are comprehensively reviewed. The electrochemical reaction circumstances on S/C and SPAN cathodes are firstly introduced and compared to reveal the working mechanisms of the two types of Li-S batteries. The S/C cathodes mainly undergo solid-liquid-solid multi-phase conversion processes with typical double-plateau charge-discharge polarization curves. In comparison, the SPAN cathodes follow solid-solid conversion and exhibit single-plateau charge-discharge characteristics. Following that, key challenges and targeted optimizing strategies of the S/C and SPAN cathodes are respectively presented and discussed. For Li-S batteries with S/C cathodes, the main optimizing strategies are electrode structure modification, efficient electrocatalyst design, and redox comediation. For SPAN cathodes, the main optimizing strategies are electrode structure modification, morphology regulation by co-polymerization, heteroatom doping at molecular level, and extrinsic redox mediation. At last, current research status of Li-S batteries with S/C or SPAN cathodes are systematically analyzed through the comparison of several battery parameters, and perspectives on challenges and opportunities of S/C and SPAN cathodes in Li-S batteries are presented to guide future researches.

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.