Ultra-Low Alginate-Based Multifunctional Composite Binders for Enhanced Mechanical, Electrochemical, and Thermal Performance of Li-S Batteries.

The practical application of Li-S batteries, which hold great potential as energy storage devices, is impeded by various challenges, such as capacity degradation caused volume change, polysulfide shuttling, poor electrode kinetics, and safety concerns. Binder plays a crucial role in suppressing volume change of cathode side, thereby enhancing the electrochemical performance of Li-S batteries. In this research, a novel network binder (SA-Co-PEDOT) composed of sodium alginate is presented, Co2+ ions as cross-linking agent and PEDOT as an electronic conductor. The theoretical analysis and experimental testing confirm that the SA-Co-PEDOT binder with synergistic combination of catalytic center and electron transfer network effectively mitigates large volumetric changes during cycling while simultaneously enhancing electrode kinetics through controlling the deposition morphology of sulfur end product and its nucleation and dissolution. As a result, it achieves a capacity of 844 mAh g-1 after 150 cycles at 0.2 C. Moreover, the electrode with SA-Co-PEDOT binder subjected a bending test maintains a capacity of 395 mAh g-1 after 500 cycles at 0.5 C, exhibiting an impressively low decay rate of only 0.11%. Even with an ultra-low content of 2 wt.% SA-Co-PEDOT binder, the electrode still maintains a capacity of 999.7 mAh g-1 after 100 cycles at 0.5 C.

Synergistic Effect of In2O3/NC-Co3O4 Interface on Enhancing the Redox Conversion of Polysulfides for High-Performance Li-S Cathode Materials at Low Temperatures.

Lithium-sulfur (Li-S) batteries are considered as a promising energy storage technology due to their high energy density; however, the shuttling effect and sluggish redox kinetics of lithium polysulfides (LiPSs) severely deteriorate the electrochemical performance of Li-S batteries. Herein, we report a novel configuration wherein In2O3 and Co3O4 are incorporated into N-doped porous carbon as a sulfur host material (In2O3@NC-Co3O4) using metal-organic framework-based materials to synergistically tune the catalytic abilities of different metal oxides for different reaction stages of LiPSs, achieving a rapid redox conversion of LiPSs. In particular, the introduction of N-doped carbon improved the electron transport of the materials. The polar interface of In2O3 and Co3O4 anchors both long- and short-chain LiPSs and catalyzes long-chain and short-chain LiPSs, respectively, even at low temperatures. Consequently, the Li-S battery with In2O3@NC-Co3O4 cathode materials delivered an excellent discharge capacity of 1042.4 mAh g-1 at 1 C and a high capacity retention of 85.1% after 500 cycles. Impressively, the In2O3@NC-Co3O4 cathode displays superior performances at high current density and low temperature due to the enhanced redox kinetics, delivering 756 mAh g-1 at 2 C (room temperature) and 755 mAh g-1 at 0.1 C (-20 °C).

Nanorod In2O3@C Modified Separator with Improved Adsorption and Catalytic Conversion of Soluble Polysulfides for High-Performance Lithium-Sulfur Batteries.

The shuttle effect of soluble lithium polysulfides (LiPSs) poses a crucial challenge for commercializing lithium-sulfur batteries. The functionalization of the separator is an effective strategy for enhancing the cell lifespan through the capture and reuse of LiPSs. Herein, a novel In2O3 nanorod with an ultrathin carbon layer (In2O3@C) was coated on a polypropylene separator. The results demonstrate the adsorption and catalysis of In2O3 on polysulfides, effectively inhibiting the shuttle effect and improving the redox kinetics of LiPSs. Besides, the ultrathin carbon layer increases the reaction sites and accelerates the electrochemical reaction rate. The cell with the In2O3@C interlayer displays excellent reversibility and stability with a 0.029% capacity decay each cycle in 2000 cycles at 2C. In addition, the In2O3@C interlayer significantly improves the cell performance under high current (888.2 mA h g-1 at 2C and room temperature) and low temperature (1007.8 mA h g-1 at 0.1C and -20 °C) conditions.

Studies on Composite Solid Electrolytes with a Dual Selective Confinement Interface Structure of Anions for High-Performance Lithium Metal Batteries.

Solid-state lithium batteries (SSLBs) have attracted much attention due to their good thermal stability and high energy density. However, solid-state electrolytes with low conductivity and prominent interfacial issues have hindered the further development of SSLBs. In this research, inspired from a selective confinement structure of anions, a novel HMOF-DNSE composite solid electrolyte with a dual selective confinement interface structure is proposed based on the semi-interpenetrating structure generated by poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), poly(di-n-butylmethylammonium) bis(trifluoromethanesulfonyl)imide (PDADMATFSI), and a metal-organic frameworks MOF derivative (HMOF) as a filler. The dual-network structure of PVDF-HFP/PDADMATFSI combined with HMOF formed a dual selective confinement interface structure to confine out the movement of large anions TFSI-, thereby enhancing the transfer ability of Li+. Subsequently, the addition of HMOF further improves the transfer of Li+ by binding up TFSI- through its crystal structure. The results show that HMOF-DNSE possesses a high room-temperature ionic conductivity (0.7 mS cm-1), a wide electrochemical window (up to 4.5 V), and a high Li+ transfer number (tLi+) (0.56). LiFePO4/HMOF-DNSE/Li cell shows an excellent capacity of 141.5 mAh g-1 at 1C rate under room temperature, with a high retention of 80.1% after 500 cycles. The material design strategy, which is based on selective confinement interface structures of anions, offers valuable insights into enhancing the electrochemical performance of solid-state lithium batteries.

Micro Area Interface Wetting Structure with Tailored Li+-Solvation and Fast Transport Properties in Composite Polymer Electrolytes for Enhanced Performance in Solid-State Lithium Batteries.

To satisfy the demand for high safety and energy density in energy storage devices, all-solid-state lithium metal batteries with solid polymer electrolytes (SPE) replacing traditional liquid electrolytes and separators have been proposed and are increasingly regarded as one of the most promising candidates as next-generation energy storage systems. In this study, poly(vinylidene fluoride)-hexafluoropropylene/lignosulfonic acid (PVDF-HFP/LSA) composite polymer electrolyte (CPE) membranes with a micro area interface wetting structure were successfully prepared by incorporating LSA into the PVDF-HFP polymer matrix. The enhanced interaction between the polar functional group in LSA and the C═O in N-methylpyrrolidone (NMP) hinders the evaporation of solvent NMP, thus creating a micro area wetting structure, which offers a flexible region for the chain segment movement and enlarging the area of the amorphous zone in PVDF-HFP. From the results of IR and Raman spectroscopy, it was found that the presence of LSA induced unique ion transport channels created by the massive aggregated ion pair (AGG) and contact ion pair (CIP) of ion cluster structures composed of Li+ and multiple TFSI- and, at the same time, effectively reduced the crystallinity of the polymer electrolyte, hence further contributing to the Li+ diffusion. As a result, at a rate of 2 C, the Li|CPE-15|LiFePO4 solid-state battery delivers an initial discharge-specific capacity of 134.9 mAh g-1 and maintains stability with a retention of 84% during 400 charge-discharge cycles while the Li|CPE-0|LiFePO4 battery fails after only a few cycles at the same rate.

Improved Electrochemical Performance of Spinel LiNi0.5Mn1.5O4 Cathode Materials with a Dual Structure Triggered by LiF at Low Calcination Temperature.

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO), which has the advantages of high energy density, low cost, environmental friendliness, and being cobalt-free, is considered one of the most promising cathode materials for the next generation of power lithium-ion batteries. However, the side reaction at the interface between the LNMO cathode material and electrolyte usually causes a low specific capacity, poor rate, and poor cycling performance. In this work, we propose a facilitated method to build a well-tuned dual structure of LiF coating and F- doping LNMO cathode material via simple calcination of LNMO with LiF at low temperatures. The experimental results and DFT analysis demonstrated that the powerful interface protection due to the LiF coating and the higher lithium diffusion coefficient caused by F- doping effectively improved the electrochemical performance of LNMO. The optimized LNMO-1.3LiF cathode material presents a high discharge capacity of 140.3 mA h g-1 at 1 C and 118.7 mA h g-1 at 10 C. Furthermore, the capacity is retained at 75.4% after the 1000th cycle at 1 C. Our research provides a concrete guidance on how to effectively boost the electrochemical performance of LNMO cathode materials.