Lithium-Sulfur Batteries at Extreme Temperatures:Challenges,Strategies and Prospects

High-energy-density-batteries working at a wide-temperature range are urgently required in many performance-critical areas.Lithium-sulfur batteries(LSB)are promising high-energy-density batteries that have the potential to maintain high performance at extreme temperatures.However,some problems like severe shuttling and safety issues at high temperatures or sluggish reaction kinetics and charge-transfer process at low temperatures decrease the performance and hinder their practical uses in extreme temperature conditions.Therefore,broadening the working temperature of LSB with stable electrochemical performance becomes a crucial topic.In this paper,the key stumbling blocks for high and low-temperature LSB are comprehensively discussed.The solutions from the aspects of electrolyte and electrode materials are discussed to solve the aggravating shuttle effect and thermal safety issues under high temperature and the sluggish reaction kinetics under low temperature.Moreover,some specific promising solutions to extend the operating temperature range of LSB are also proposed and highlighted,which provide potential research directions on the practical LSB application in future.

Enhanced Roles of Carbon Architectures in High-Performance Lithium-Ion Batteries

Lithium?ion batteries(LIBs), which are high?energy?density and low?safety?risk secondary batteries, are underpinned to the rise in electrochemical energy storage devices that satisfy the urgent demands of the global energy storage market. With the aim of achiev?ing high energy density and fast?charging performance, the exploitation of simple and low?cost approaches for the production of high capacity, high density, high mass loading, and kinetically ion?accessible electrodes that maximize charge storage and transport in LIBs, is a critical need. Toward the construction of high?performance electrodes, carbons are promisingly used in the enhanced roles of active materials, electrochemi?cal reaction frameworks for high?capacity noncarbons, and lightweight current collectors. Here, we review recent advances in the carbon engi?neering of electrodes for excellent electrochemical performance and structural stability, which is enabled by assembled carbon architectures that guarantee su cient charge delivery and volume fluctuation bu ering inside the electrode during cycling. Some specific feasible assem?bly methods, synergism between structural design components of carbon assemblies, and electrochemical performance enhancement are highlighted. The precise design of carbon cages by the assembly of graphene units is potentially useful for the controlled preparation of high?capacity carbon?caged noncarbon anodes with volumetric capacities over 2100 mAh cm^(-3). Finally, insights are given on the prospects and challenges for designing carbon architectures for practical LIBs that simultaneously provide high energy densities(both gravimetric and volumetric) and high rate performance.

Stress-assisted design of stiffened graphene electrode structure toward compact energy storage

The low spatial charge-storage density of porous carbons greatly limits volumetric performance in electrochemical capacitors.An increase of charge-storage density requires structural refinements to balance the trade-offs between the porosity and density of materials,but the limited mechanical properties of carbons usually fail to withstand effective densifying processes and obtain an ideal pore structure.Herein,we design the stiffened graphene of superior bending rigidity,enabling the fine adjustments of pore structure to maximize the volumetric capacitance for the graphene-based electrodes.The inplane crumples on graphene sheets are found to contribute largely to the bending rigidity,which is useful to control the structural evolution and maintain sufficient ion-accessible surface area during the assembling process.This makes the capacitance of stiffening activated graphene keep 98%when the electrode density increases by 769%to reach 1.13 g cm^(-3) after mechanical pressure,an excellent volumetric energy density of 98.7 Wh L^(-1) in an ionic-liquid electrolyte is achieved.Our results demonstrate the role of intrinsic material properties on the performance of carbon-based electrodes for capacitive energy storage.

Promoted conversion of polysulfides by MoO_2 inlaid ordered mesoporous carbons towards high performance lithium-sulfur batteries

As polar materials, transition-metal oxides have shown great potentials to improve the adsorption of lithium polysulfides in lithium-sulfur batteries. Herein, a MoO_2-ordered mesoporous carbon (M-OMC)hybrid was designed as the sulfur host, in which MoO_2 is inlaid on the surface of ordered mesoporous carbons that can store active materials and provide fast electron transfer channel due to its ordered pore structure. The MoO_2 can effectively prevent the migration of polysulfides through the chemical adsorption and promote the conversion of polysulfides towards Li-sulfur battery.