High-Performance Lithium-Ion Batteries with High Stability Derived from Titanium-Oxide- and Sulfur-Loaded Carbon Spherogels

This study presents a novel approach to developing high-performance lithium-ion battery electrodes by loading titania-carbon hybrid spherogels with sulfur. The resulting hybrid materials combine high charge storage capacity, electrical conductivity, and core-shell morphology, enabling the development of next-generation battery electrodes. We obtained homogeneous carbon spheres caging crystalline titania particles and sulfur using a template-assisted sol-gel route and carefully treated the titania-loaded carbon spherogels with hydrogen sulfide. The carbon shells maintain their microporous hollow sphere morphology, allowing for efficient sulfur deposition while protecting the titania crystals. By adjusting the sulfur impregnation of the carbon sphere and varying the titania loading, we achieved excellent lithium storage properties by successfully cycling encapsulated sulfur in the sphere while benefiting from the lithiation of titania particles. Without adding a conductive component, the optimized material provided after 150 cycles at a specific current of 250 mA g-1 a specific capacity of 825 mAh g-1 with a Coulombic efficiency of 98%.

Harnessing Heteropolar Lithium Polysulfides by Amphoteric Polymer Binder for Facile Manufacturing of Practical Li-S Batteries

Enabling efficient and durable charge storage under high sulfur loading and lean electrolyte remains a paramount challenge for Li-S battery technology to truly demonstrate its commercial viability. This work reports an amphoteric polymer binder, whose negatively and positively charged moieties allow for coregulation of both lithium cations and heteropolar lithium polysulfides through multiple intermolecular interactions. These interactions and the physical properties lead to simultaneously improved Li⁺ transport, polysulfide adsorption and catalysis, cathode robustness and anode stability. Therefore, this multifunctional binder endows Li-S batteries with compelling overall performances even under rigorous conditions. At low sulfur loading and copious electrolyte, the cell shows a low capacity-fading rate of 0.056% cycle-1 upon 700 cycles. At sulfur loading of 6.8 mg cm^-2 and low E/S of 6 µL mg^-1 , the cell still delivers stable areal capacities between 4.2 and 4.8 mAh cm^-2 in 50 cycles without obvious decay at 0.2 C. The commercial feasibility of this work is further manifested by its zero added weight, low material cost, and ease of manufacturing and scale-up. The efficacy and simplicity of this work symbolize an example of lab-scale battery research aiming at improved technology and manufacturing readiness level.

Melamine Foam Derived 2H/1T MoS2 as Flexible Interlayer with Efficient Polysulfides Trapping and Fast Li+ Diffusion to Stabilize Li-S Batteries

Lithium-sulfur (Li-S) batteries featuring high-energy densities are identified as a hopeful energy storage system but are strongly impeded by shuttle effect and sluggish redox chemistry of sulfur cathodes. Herein, annealed melamine foam loaded 2H/1T MoS₂ (CF@2H/1T MoS₂) is prepared as a multifunctional interlayer to inhibit the shuttle effect, improve redox kinetics, and reduce the charge-discharge polarization of Li-S batteries. The CF@2H/1T MoS₂ becomes fragmented structures after assembling the cell, which not only benefits to adsorb and catalyze LiPSs but also to significantly buffer the volume expansion due to a large number of gaps between fragmented structures. Meanwhile, the batteries based on CF@2H/1T MoS₂ interlayer delivers high areal capacity of 5.1 mAh cm^-2 under high sulfur mass loading of 7.6 mg cm^-2 at 0.2 C. Importantly, the experiments of in situ Raman spectra demonstrate that the CF@2H/1T MoS₂ can obviously inhibit the shuttle effect by effectively adsorbing and catalyzing LiPSs. This novel design idea and low-cost melamine foam raw material open up a new way for the application of high-energy density Li-S batteries.

Boosting Performance of Na-S Batteries Using Sulfur-Doped Ti3C2Tx MXene Nanosheets with a Strong Affinity to Sodium Polysulfides

Sodium-sulfur batteries using abundant elements offer an attractive alternative to currently used batteries, but they need better sulfur host materials to compete with lithium-ion batteries in capacity and cyclability. We report an in situ sulfur-doping strategy to functionalize MXene nanosheets by introducing heteroatomic sulfur into the MXene structure form the MAX phase precursor. By employing the vacuum freeze-drying method, a three-dimensional (3D) wrinkled MXene nanoarchitecture with the high specific surface area was prepared. The tailor-made wrinkled sulfur-doped MXene (S-Ti₃C₂T_x) nanosheets were applied as an electrode host material in room temperature sodium-sulfur batteries. The S-Ti₃C₂T_x matrix shows high polarity with sodium polysulfides, restricting the diffusion of sodium polysulfides. The MXene/sulfur electrode can achieve high areal sulfur loading up to 4.5 mg cm^-2 as well as good electrochemical performance (reversible capacity of 577 mAh g^-1 at 2 C after 500 cycles).

Key Parameters Governing the Energy Density of Rechargeable Li/S Batteries

Rechargeable lithium-sulfur batteries have high theoretical capacity and energy density. However, their volumetric energy density has been believed to be lower than that of conventional lithium ion batteries employing metal oxide cathodes like LiCoO2. Here, we study the effects of sulfur loading percentage, develop a simple model and calculate the gravimetric and volumetric energy densities based on the total composition of electrodes in a lithium-sulfur cell, and compare those results with a typical graphite/LiCoO2 cell. From the model output, we have identified and established key parameters governing the energy density of rechargeable Li/S batteries. We find that the sulfur loading percentage has a much higher impact on the volumetric energy density than on the gravimetric energy density. A lithium-sulfur cell can exceed a lithium ion cell's volumetric energy density but only at high sulfur loading percentages (ca. 70%). We believe that these findings may attract more attention of lithium-sulfur system studies to high sulfur loading levels.