Simultaneously Suppressing Shuttle Effect and Dendrite Growth in Lithium-Sulfur Batteries via Building Dual-Functional Asymmetric-Cellulose Gel Electrolyte.

Polysulfides huttling and interfacial instability of Lithium-anode are the main technical issues hindering commercialization of high-energy-density lithium-sulfur batteries. Simply addressing the problem of polysulfide shuttling or lithium dendrite growth can result in safety hazards or short lifespan. To synchronously tackle the aforementioned issues, the authors have designed an asymmetric cellulose gel electrolyte, a defective and ionized UiO66/black phosphorus heterostructure coating layer (Di-UiO66/BP) and a cationic cellulose gelelectrolyte (QACA). Defective and ionized engineered UiO66 particles significantly enhances performance of UiO66/BP layer in anchoring free polysulfides, promoting smooth and effective polysulfide conversion and expediting the redox kinetics of sulfur cathode, therefore suppressing polysulfide shuttling. QACA electrolyte with numerous cationic groups can interact with anions via electrostatic adsorption, thus enhancing lithium-ion transference number and contributing to formation of stable solid electrolyte interface to suppress lithium dendrite growth. Owing to the superior performance of QACA/Di-UiO66/BP, the final cells exhibit outstanding electrochemical performance, presenting high sulfur utilization (1420.1 mAh g-1 at 0.1 C), high-rate capacity (665.4 mAh g-1 at 4 C) and long cycle lifespan. This work proposes a strategy of designing asymmetric electrolytes to simultaneously address the challenges in both S-cathode and Li-anode, which contributes to advanced Li-S batteries and their practical application.

Huang Y ，Cheng F ，Cai C ，Fu Y ... -  《-》

Emerging Strategies for Gel Polymer Electrolytes with Improved Dual-Electrode Side Regulation Mechanisms for Lithium-Sulfur Batteries.

Although GPE still has the risk of shuttling due to the incomplete removal of liquid electrolytes compared to SPE, which has the most promise of eliminating polysulfide shuttling, researchers have made abundant efforts to eliminate as much of the polysulfide shuttling effect as possible while retaining the unique advantages of GPE. For example, physical barrier to polysulfides by improving the pore size of GPE or fabricating multidimensional structures by different preparation methods. Further chemical adsorption of polysulfides by adding nanofillers to increase polar sites to create polar-polar interactions with polysulfides or to create Lewis acid-base interactions. However, although chemical adsorption can indeed highly immobilize polysulfides, it still brings disadvantages such as loss of active material. Therefore, other researchers have employed GPE with ion-selective permeability that has electrostatic repulsive force or steric hindrance to polysulfides to better inhibit polysulfide shuttling. However, modifying only the cathode side is not enough to enhance this overall properties of Li-S cells. These problems of poor Li+ transport, lithium dendrite growth, and poor SEI due to uneven lithium ion deposit on Li anode side still affect the overall performance of Li-S cells. Therefore, a GPE to improve these problems on the Li anode side is summarized below. Compared with an all-solid electrolyte, GPE, which has a partially liquid electrolyte, clearly has advantages such as strong interfacial contact, good anode interface compatibility, and high flexibility. However, it is still not comparable to the ionic conductivity, etc. of pure liquid electrolyte only. Therefore, the problems on the lithium metal anode side are mainly focused on the lithium ion transport problems and the problems of lithium dendrite growth and inhomogeneous SEI at the lithium anode interface. Facing the problems in these two aspects, researchers have given many improvement solutions respectively. For the lithium ion transport problem, researchers have instead provided pathways for lithium ion transport by adding amorphous nanofibers or nanofillers to reduce the crystallinity of the polymer and improve the ionic conductivity. Alternatively, the migration number of lithium ions can be increased by limiting the anions in the electrolyte. As for the interfacial problems of lithium anodes, researchers have effectively suppressed the growth of lithium dendrites or inhomogeneous lithium plating/stripping phenomena mainly by adding nanofillers to increase the mechanical strength of GPE or by participating in the generation of SEI.

Cui Y ，Li J ，Yuan X ，Liu J ，Zhang H ，Wu H ，Cai Y ... -  《-》

All-cellulose gel electrolyte with black phosphorus based lithium ion conductors toward advanced lithium-sulfurized polyacrylonitrile batteries.

Sulfurized polyacrylonitrile (SPAN) have been regarded as a promising cathode in high-energy-density lithium-sulfur batteries. However, severe safety issues derived from the electrolyte leakage and the uncontrollable lithium dendrite growth have seriously hindered the practical usage of Li-SPAN batteries. To address these issues, an eco-friendly and porous cellulose gel electrolyte (GE) was designed and prepared by UV photopolymerization and phase inversion methods. Also, covalent functional black phosphorous nanosheets (denoted as BP-Li) were fabricated and chosen as superior Li+ conductors in cellulose GE, ensuring the rapid ion transmission and suppressing the growth of lithium dendrites. As expected, the cellulose/BP-Li GE exhibited satisfactory ionic conductivity up to 5.21 × 10-3 S cm-1 with the high lithium ion transference number of 0.72. The Li-SPAN battery assembled with cellulose/BP-Li GE delivered high capacity of 938.8 mAh g-1 after 500 cycles with the capacity retention of 72.8 %. Hence, the cellulose/BP-Li GE displayed its promising usage in Li-SPAN batteries.

Huang Y ，Wang Y ，Fu Y 《-》

Nontraditional Approaches To Enable High-Energy and Long-Life Lithium-Sulfur Batteries.

Zhao C ，Amine K ，Xu GL 《-》

N, S-Coordinated Co Single Atomic Catalyst Boosting Adsorption and Conversion of Lithium Polysulfides for Lithium-Sulfur Batteries.

Boosting reversible solid-liquid phase transformation from lithium polysulfides to Li2 S and suppressing the shuttling of lithium polysulfides from the cathode to the lithium anode are critical challenges in lithium-sulfur batteries. Here, sulfiphilic single atomic cobalt implanted in lithiophilic heteroatoms-dopped carbon (SACo@HC) matrix with a CoN3 S structure for high-performance lithium-sulfur batteries is reported. Density functional theory calculation and in situ experiments demonstrate that the optimal CoN3 S structure in SACo@HC can effectively improve the adsorption and redox conversion efficiency of lithium polysulfides. Consequently, the S-SACo@HC composite with sulfur loading of 80 wt% delivers a high capacity of 1425.1 mAh g-1 at 0.05 C and outstanding rate performance with 745.9 mAh g-1 at 4 C. Furthermore, a capacity of 680.8 mAh g-1 at 0.5 C with a low electrolyte/sulfur ratio (6 µL mg-1 ) can be achieved even after 300 cycles. With the harsh conditions of lean electrolyte (E/S = 4 µL mg-1 ) and high sulfur loading (5.4 mg cm-2 ), a superior area capacity of 5.8 mAh cm-2 can be obtained. This work contributes to building a profound understanding of the adsorption and interface engineering of lithium polysulfides and provides ideas to tackle the long-standing polysulfide shuttle problem of lithium-sulfur batteries.

Liu K ，Wang X ，Gu S ，Yuan H ，Jiang F ，Li Y ，Tan W ，Long Q ，Chen J ，Xu Z ，Lu Z ... -  《-》