Multifunctional Free-Standing Gel Polymer Electrolyte with Carbon Nanofiber Interlayers for High-Performance Lithium-Sulfur Batteries

In Situ Phosphorization for Constructing Ni5P2-Ni Heterostructure Derived from Bimetallic MOF for Li-S Batteries

Heterostructured materials commonly consist of bifunctions due to the different ingredients. For host material in the sulfur cathode of lithium-sulfur (Li-S) batteries, the chemical adsorption and catalytic activity for lithium polysulfides (LiPS) are important. This work obtains a Ni5P2-Ni nanoparticle (Ni5P2-NiNPs) heterostructure through a confined self-reduction method followed by an in situ phosphorization process using Al/Ni-MOF as precursors. The Ni5P2-Ni heterostructure not only has strong chemical adsorption, but also can effectively catalyze LiPS conversion. Furthermore, the synthetic route can keep Ni5P2-NiNPs inside of the nanocomposites, which have structural stability, high conductivity, and efficient adsorption/catalysis in LiPS conversion. These advantages make the assembled Li-S battery deliver a reversible specific capacity of 619.7 mAh g- 1 at 0.5 C after 200 cycles. The in situ ultraviolet-visible technique proves the catalytic effect of Ni5P2-Ni heterostructure on LiPS conversion during the discharge process.

Bifunctional K3PW12O40/Graphene Oxide-Modified Separator for Inhibiting Polysulfide Diffusion and Stabilizing Lithium Anode

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation batteries due to their high theoretical energy density. However, the practical application of Li-S batteries is still hindered by several challenges, such as the polysulfide shuttle and the growth of lithium dendrites. Herein, we introduce a bifunctional K3PW12O40/graphene oxide-modified polypropylene separator (KPW/GO/PP) as a highly effective solution for mitigating polysulfide diffusion and protecting the lithium anode in Li-S batteries. By incorporating KPW into a densely stacked nanostructured graphene oxide (GO) barrier membrane, we synergistically capture and rapidly convert lithium polysulfides (LiPSs) electrochemically, thus effectively suppressing the shuttling effect. Moreover, the KPW/GO/PP separator can stabilize the lithium metal anode during cycling, suppress dendrite formation, and ensure a smooth and dense lithium metal surface, owing to regulated Li+ flux and uniform Li nucleation. Consequently, the constructed KPW/GO/PP separator delivered a favorable initial specific capacity (1006 mAh g-1) and remarkable cycling performance at 1.0 C (626 mAh g-1 for up to 500 cycles with a decay rate of 0.075% per cycle).

Cellulose Acetate-Based High-Electrolyte-Uptake Gel Polymer Electrolyte for Semi-Solid-State Lithium-Oxygen Battery with Long-Cycling Stability

The lithium-oxygen battery has inspired great research interests owing to its ultrahigh theoretical energy density and has been considered as one of the promising secondary batteries. However, there are still some challenges in its practical application, like liquid organic electrolyte evaporation in the semi-open system and instability in the high-voltage oxidizing environment. In this work, a cellulose acetate-based gel polymer electrolyte (CA@GPE) is proposed, whose cross-linked microporous structure ensures the ultrahigh liquid electrolyte uptake of 2391%. The prepared CA@GPE exhibits a high lithium-ion transference number of 0.595, a satisfying ionic conductivity of 0.47 mS cm -1 and a wide electrochemical stability window up to 5.0 V. The Li//Li symmetric cell employing CA@GPE could cycle stably over 1200 h. The lithium-oxygen battery with CA@GPE presents a superb cycling lifetime of 370 cycles at 0.1 mA cm -2 under 0.25 mAh cm -2 . This work offers a possible strategy to realize long-cycling stability lithium-oxygen batteries.

Emerging Strategies for Gel Polymer Electrolytes with Improved Dual-electrode Side Regulation Mechanisms for Lithium-sulfur Batteries

Lithium-sulfur (Li-S) batteries, known for its high energy density, are limited in practical application by lithium dendrite growth, polysulfide "shuttle effect", and safety issues. Gel polymer electrolytes that combine high ionic conductivity and safety are the key to solving these problems. Based on the special reaction mechanism of Li-S batteries, this paper summarizes in detail the GPE types for different key problems existing in cathodes and anodes, and discusses their corresponding action mechanisms and improvement methods. Finally, the current challenges and future development direction of GPEs for Li-S batteries are summarized and prospected.

Methods to Improve Lithium Metal Anode for Li-S Batteries

The lithium-sulfur (Li-S) battery has received a lot of attention because it is characterized by high theoretical energy density (2,600 Wh/kg) and low cost. Though many works on the “shuttle effect” of polysulfide have been investigated, lithium metal anode is a more challenging problem, which leads to a short life, low coulombic efficiency, and safety issues related to dendrites. As a result, the amelioration of lithium metal anode is an important means to improve the performance of lithium sulfur battery. In this paper, improvement methods on lithium metal anode for lithium sulfur batteries, including adding electrolyte additives, using solid, and/or gel polymer electrolyte, modifying separators, applying a protective coating, and providing host materials for lithium deposition, are mainly reviewed. In addition, some challenging problems, and further promising directions are also pointed out for future research and development of lithium metal for Li-S batteries.

A review of flexible lithium–sulfur and analogous alkali metal–chalcogen rechargeable batteries

This review summarizes recent progress in flexible Li–S and analogous alkali metal–chalcogen batteries, including flexible chalcogen cathodes, flexible alkali metal anodes, flexible solid-state electrolytes, and flexible battery prototypes.