Enhanced Cycling Performance of All-Solid-State Li-S Battery Enabled by PVP-Blended PEO-Based Double-Layer Electrolyte.

Despite the high specific capacity of Li-S battery, shuttle effect of lithium polysulfides (LiPSs) and safety issue pose a great challenge to realize its commercial application. Replacing liquid electrolyte with poly (ethylene oxide) (PEO) -based solid-state electrolyte is considered as a promising method to boost the safety, but the shuttle effect of LiPSs cannot be completely eliminated. In this work, a new kind of double-layer PEO-based polymer electrolyte is designed to restrict the LiPSs. The layer next to cathode consists of PEO and poly(vinylpyrrolidone) (PVP). The other layer consists of PEO. PVP with abundant of amide groups has been proved to have strong affinity to LiPSs. The strong interaction between LiPSs and carbonyl groups in amide is verified by Attenuated Total Reflection-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy tests. As a result, the assembled Li-S battery exhibits a specific capacity of 1100 mAh g-1 and capacity retention of 347 mAh g-1 after 200 cycles at 60 °C and 0.05 C, while the capacity retention of the battery without PVP-blended PEO electrolyte remains only 27 % at the same conditions.

Large Scale Synthesis of Three-dimensional Hierarchical Porous Framework with High Conductivity and its Application in Lithium Sulfur Battery.

Quick capacity loss due to the polysulfide shuttle effects and poor rate performance caused by low conductivity of sulfur have always been obstacles to the commercial application of lithium sulfur batteries. Herein, an in-situ doped hierarchical porous biochar materials with high electron-ion conductivity and adjustable three-dimensional (3D) macro-meso-micropore is prepared successfully. Due to its unique physical structure, the resulting material has a specific surface area of 2124.9 m2 g-1 and a cumulative pore volume of 1.19 cm3 g-1 . The presence of micropores can effectively physically adsorb polysulfides and mesopores ensure the accessibility of lithium ions and active sites and give the porous carbon material a high specific surface area. The large pores provide channels for the storage of electrolyte and the transmission of ions on the surface of the substrate. The combined effect of these three kinds of pores and the N doping formed in-situ can effectively promote the cycle and rate performance of the battery. Therefore, prepared cathode can still reach a reversible discharge capacity of 616 mAh g-1 at a rate of 5 C. After 400 charge-discharge cycles at 1 C, the reversible capacity is maintained at 510.0 mAh g-1 . This new strategy has provided a new approach to the research and industrial-scale production of adjustable hierarchical porous biochar materials.

In situ fabrication of graphene-carbon nanochain webs as anodes for Li-ion batteries.

Carbon nanochain webs-sandwiched graphene has been successfully fabricated via in situ polymerization and subsequent carbonization. Such a novel nano-micro structure not only provides high conductivity, but also improves the cycling stability and rate capability during Li-ion storage. It shows a charge capacity of 1103.2 mA h g(-1) at 0.05 A g(-1) after 50 cycles.

Enhancement Effects of Co Doping on Interfacial Properties of Sn Electrode-Collector: A First-Principles Study.

The Co doping effects on the interfacial strength of Sn electrode-collector interface for lithium-ion batteries are investigated by using first-principles calculations. The results demonstrate that by forming strong chemical bonds with interfacial Sn, Li, and Cu atoms, Co doping in the interface region can enhance interfacial strengths and stabilities during lithiation. With doping, the highest strengths of Sn/Cu (1.74 J m-2) and LiSn/Cu (1.73 J m-2) interfaces are 9.4 and 17.7% higher than those of the corresponding interface systems before doping. Besides, Co doping can reduce interface charge accumulation and offset the decreasing interfacial strength during lithiation. Furthermore, the interfacial strength and electronic stability increase with rising Co content, whereas the increasing formation heat may result in thermodynamic instability. On the basis of the change of formation heat with Co content, an optimal Co doping content has been provided.