New Insight into the Working Mechanism of Lithium-Sulfur Batteries under a Wide Temperature Range

Developing a Multifunctional Cathode for Photoassisted Lithium-Sulfur Battery

Integration of solar cell and secondary battery cannot only promote solar energy application but also improve the electrochemical performance of battery. Lithium-sulfur battery (LSB) is an ideal candidate for photoassisted batteries owing to its high theoretical capacity. Unfortunately, the researches related the combination of solar energy and LSB are relatively lacking. Herein, a freestanding photoelectrode is developed for photoassisted lithium-sulfur battery (PALSB) by constructing a heterogeneous structured Au@N-TiO2 on carbon cloths (Au@N-TiO2/CC), which combines multiple advantages. The Au@N-TiO2/CC photoelectrode can produce the photoelectrons to facilitate sulfur reduction during discharge process, while generating holes to accelerate sulfur evolution during charge process, improving the kinetics of electrochemical reactions. Meanwhile, Au@N-TiO2/CC can work as an electrocatalyst to promote the conversion of intermediate polysulfides during charge/discharge process, mitigating induced side reactions. Benefiting from the synergistic effect of electrocatalysis and photocatalysis, PALSB assembled with an Au@N-TiO2/CC photoelectrode obtains ultrahigh specific capacity, excellent rate performance, and outstanding cycling performance. What is more, the Au@N-TiO2/CC assembled PALSB can be directly charged under light illumination. This work not only expands the application of solar energy but also provides a new insight to develop advanced LSBs.

Empowering Low-Temperature Lithium-Sulfur Batteries: Unlocking the Potential of Transition Metal Alloy-Based Cathode Materials

At low temperatures, lithium-sulfur (Li-S) batteries have poor kinetics, resulting in extreme polarization and decreased capacity. In this study, we investigated the electrochemical performance of Li-S batteries utilizing transition metal alloy-based cathode materials. Specifically, binary transition metal alloys (FeNi, FeCo, and NiCo) are integrated into a porous carbon nanofiber (CNF) matrix as composite cathode material. Our findings reveal that alloying metallic Ni with Fe in the FeNi@CNFs composite enhances the catalytic conversion of sulfur species, mitigating the shuttle effect and improving battery performance even under low temperatures. Li-S batteries employing a Li2S6/FeNi@CNFs cathode exhibited a significantly high initial discharge capacity of 1655 mAh g-1 at 0.1 C. Even at the higher current density of 10 C, the Li2S6/FeNi@CNFs composite can still reach an ultrahigh specific capacity of 828 mAh g-1. In addition, Li2S6/FeNi@CNFs demonstrated exceptional initial discharge capacities of 890.5 and 382.7 mAh g-1 at 0.1 C under -20 and -40 °C, respectively. With an initial capacity of 392.02 mAh g-1 and a capacity retention rate of 88.86% (after 60 cycles) at 0.2 C, the conversion of LiPSs in Li2S6/FeNi@CNFs is significantly enhanced even at ultralow temperatures of -40 °C. The findings of this study hold significant implications for the advancement of extremely low-temperature Li-S batteries.

A multifunctional solution to enhance capacity and stability in lithium-sulfur batteries: Incorporating hollow CeO2 nanorods into carbonized non-woven fabric as an interlayer

Lithium-sulfur batteries (LSBs) hold promise as the next-generation lithium-ion batteries (LIBs) due to their ultra-high theoretical capacity and remarkable cost-efficiency. However, these batteries suffer from the serious shuttle effect, challenging their practical application. To address this challenge, we have developed a unique interlayer (HCON@CNWF) composed of hollow cerium oxide nanorods (CeO2) anchored to carbonized non-woven viscose fabric (CNWF), utilizing a straightforward template method. The prepared interlayer features a three-dimensional (3D) conductive network that serves as a protective barrier and enhances electron/ion transport. Additionally, the CeO2 component effectively chemisorbs and catalytically transforms lithium polysulfides (LiPSs), offering robust chemisorption and activation sites. Moreover, the unique porous structure of the HCON@CNWF not only physically adsorbs LiPSs but also provides ample space for sulfur's volume expansion, thus mitigating the shuttle effect and safeguarding the electrode against damage. These advantages collectively contribute to the battery's outstanding electrochemical performance, notably in retaining a reversible capacity of 80.82 % (792 ± 5.60 mAh g-1) of the initial value after 200 charge/discharge cycles at 0.5C. In addition, the battery with HCON@CNWF interlayer has excellent electrochemical performance at high sulfur loading (4 mg cm-2) and low liquid/sulfur ratio (7.5 µL mg-1). This study, thus, offers a novel approach to designing advanced interlayers that can enhance the performance of LSBs.

Tandem Catalysis inside Double-Shelled Nanocages with Separated and Tunable Atomic Catalyst Sites for High Performance Lithium-Sulfur Batteries

Single-atomic catalysts are effective in mitigating the shuttling effect and slow redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries, but their ideal performance has yet to be achieved due to the multi-step conversion of LiPSs requiring multifunctional active sites for tandem catalysis. Here double-shelled nano-cages (DSNCs) have been developed to address this challenge, featuring separated and tunable single-atom sites as nano reactors that trigger tandem catalysis and promote the efficient electrochemical conversion of LiPSs. This enables high capacity and durable Li-S batteries. The DSNCs, with inner Co-N4 and outer Zn-N4 sites (S/CoNC@ZnNC DSNCs), exhibit a high specific capacity of 1186 mAh g-1 at 1 C, along with a low capacity fading rate of 0.063% per cycle over 500 cycles. Even with a high sulfur loading (4.2 mg cm-2) and a low E/S ratio (6 µL mg-1), the cell displays excellent cycling stability. Moreover, the Li-S pouch cells are capable of stable cycling for more than 160 cycles. These results demonstrate the feasibility of driving successive sulfur conversion reactions with separated active sites, and are expected to inspire further catalyst design for high performance Li-S batteries.