An odyssey of lithium metal anode in liquid lithium–sulfur batteries

Improving Rate Performance of Encapsulating Lithium-Polysulfide Electrolytes for Practical Lithium-Sulfur Batteries

The cycle life of high-energy-density lithium-sulfur (Li-S) batteries is severely plagued by the incessant parasitic reactions between Li metal anodes and reactive Li polysulfides (LiPSs). Encapsulating Li-polysulfide electrolyte (EPSE) emerges as an effective electrolyte design to mitigate the parasitic reactions kinetically. Nevertheless, the rate performance of Li-S batteries with EPSE is synchronously suppressed. Herein, the sacrifice in rate performance by EPSE is circumvented while mitigating parasitic reactions by employing hexyl methyl ether (HME) as a co-solvent. The specific capacity of Li-S batteries with HME-based EPSE is nearly not decreased at 0.1 C compared with conventional ether electrolytes. With an ultrathin Li metal anode (50 μm) and a high-areal-loading sulfur cathode (4.4 mgS  cm-2 ), a longer cycle life of 113 cycles was achieved in HME-based EPSE compared with that of 65 cycles in conventional ether electrolytes at 0.1 C. Furthermore, both high energy density of 387 Wh kg-1 and stable cycle life of 27 cycles were achieved in a Li-S pouch cell (2.7 Ah). This work inspires the feasibility of regulating the solvation structure of LiPSs in EPSE for Li-S batteries with balanced performance.

Multifunctional Acetamide Additive Combined with LiNO3 Co-Assists Low-Concentration Electrolyte Interfacial Stability for Lithium Metal Batteries

Lithium metal batteries (LMBs) are expected to upgrade their energy density to meet the growing battery market demand; however, intractable lithium dendrites and prominent electrode-electrolyte interface problems have been the stumbling block to their practical applications. Electrolytes play a crucial role in LMBs and are directly involved in the establishment of the electrode-electrolyte interface. In particular, low-concentration electrolytes (LCEs) can significantly save electrolyte costs, but the interface issue is more noteworthy. Here, multifunctional acetamide (N-methyl-N-(trimethylsilyl)-trifluoroacetamide, MTA) and lithium nitrate (LiNO3) additives were introduced together to enhance the performance of LMBs in LCEs. The MTA additive effectively removes the trace water and corrosive HF from the electrolyte, thus suppressing lithium salt decomposition and enhancing the stability of LCEs. Moreover, the MTA additive can construct an inorganic-rich interphase layer on the cathode/anode surface to protect the electrode. Especially, MTA can cooperate with LiNO3 additive to suppress lithium dendrites and reduce interfacial impedance, thus effectively enhancing lithium metal anode stability. Benefiting from the introduction of MTA and LiNO3 additives in the LCEs, the Li||NMC811 metal battery still has a capacity of 110 mA h g-1 after 500 cycles at room temperature, while the reference batteries have failed. The rate capacity and high temperature (50 °C) performance of the Li||NCM811 batteries have also been significantly improved. Significantly, this research explores a cost-effective method of using multifunctional additives to enhance LMBs' stability in LCEs.

Defect-rich Mo2S3 loaded wood-derived carbon acts as a spacer in lithium-sulfur batteries: forming a polysulfide capture net and promoting fast lithium flux

Due to the sluggish kinetics of sulfur conversion and the large volume change of the lithium anode, along with the formation of lithium dendrites, lithium-sulfur batteries (LSBs) usually exhibit severe capacity decay and poor cycle life. It is necessary to consider the factors associated with cathodes, separators and anodes in an integrated manner to solve the problems existing in LSBs. In this paper, a vertically aligned porous carbon decorated with transition metal sulfides was introduced between a cathode and an anode to comprehensively solve the problems of LSBs. Widely existing natural wood was used as the framework structure, and Mo₂S₃ with abundant sulfur vacancies was deposited into its channels. Theoretical calculations and experimental results have confirmed a low energy barrier for sulfur conversion and the presence of a strong electric field around the spacer, which benefits fast ion transportation. As a result, on employing the multifunctional spacer, LSB full cells delivered a high initial capacity and a long cycle life. This study provides a reference for reducing development cost, simplifying optimization steps and promoting the commercial application of LSBs.

Advanced Composite Lithium Metal Anodes with 3D Frameworks: Preloading Strategies, Interfacial Optimization, and Perspectives

Lithium (Li) metal is regarded as the most promising anode candidate for next-generation rechargeable storage systems due to its impeccable capacity and the lowest electrochemical potential. Nevertheless, the irregular dendritic Li, unstable interface, and infinite volume change, which are the intrinsic drawbacks rooted in Li metal, give a seriously negative effect on the practical commercialization for Li metal batteries. Among the numerous optimization strategies, designing a 3D framework with high specific surface area and sufficient space is a convincing way out to ameliorate the above issues. Due to the Li-free property of the 3D framework, a Li preloading process is necessary before the 3D framework that matches with the electrolyte and cathode. How to achieve homogeneous integration with Li and 3D framework is essential to determine the electrochemical performance of Li metal anode. Herein, this review overviews the recent general fabrication methods of 3D framework-based composite Li metal anode, including electrodeposition, molten Li infusion, and pressure-derived fabrication, with the focus on the underlying mechanism, design criteria, and interfacial optimization. These results can give specific perspectives for future Li metal batteries with thin thickness, low N/P ratio, lean electrolyte, and high energy density (>350 Wh Kg^-1 ).