High area-capacity Mg batteries enabled by sulfur/copper integrated cathode design

Rechargeable Mg batteries potentially display lower cost and competitive energy density compared with their Li-ion counterparts.However,the practical implementation of high area-capacity cathodes still remains a formidably challenging task.This work presents the sulfur/copper integrated cathodes fabricated by the conventional blade-coating process and slurry-dipping method.The sulfur/copper foil integrated cathodes deliver a high area-capacity of 2.6 mAh cm^(-2)after 40 cycles,while the sulfur/copperfoam integrated cathode exhibits an ultrahigh area-capacity of 35.4 mAh cm^(-2),corresponding to 743.1 Wh L^(-1)at the electrode level(1.5 times higher than the LiCoO_(2)-graphite system).The in-situ formed copper sulfide intermediates with sufficient cation defects can act as functional intermediates to regulate the sulfur electrochemistry during the first discharge process.The subsequent cycles are operated by the reversible displacement reaction between Mg-ions and copper sulfide active substances.In particular,the copper ions prefer to extrude along the[001]direction in copper sulfides lattice and simultaneously the rock-salt MgS crystals are generated.Besides,the nonuniform surface topography of the cycled Mgmetal anode,caused by the spatial inhomogeneity in current distribution,is demonstrated to lead to the battery performance degradation for high area-capacity Mg batteries.

Designing All‑Solid‑State Batteries by Theoretical Computation:A Review

All-solid-state batteries(ASSBs)with solid-state electrolytes and lithium-metal anodes have been regarded as a promis-ing battery technology to alleviate range anxiety and address safety issues due to their high energy density and high safety.Understanding the fundamental physical and chemical science of ASSBs is of great importance to battery development.To confirm and supplement experimental study,theoretical computation provides a powerful approach to probe the thermody-namic and kinetic behavior of battery materials and their interfaces,resulting in the design of better batteries.In this review,we assess recent progress in the theoretical computations of solid electrolytes and the interfaces between the electrodes and electrolytes of ASSBs.We review the role of theoretical computation in studying the following:ion transport mechanisms,grain boundaries,phase stability,chemical and electrochemical stability,mechanical properties,design strategies and high-throughput screening of inorganic solid electrolytes,mechanical stability,space-charge layers,interface buffer layers and dendrite growth at electrode/electrolyte interfaces.Finally,we provide perspectives on the shortcomings,challenges and opportunities of theoretical computation in regard to ASSBs.

Optimization on transport of charge carriers in cathode of sulfide electrolyte-based solid-state lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are considered as promising candidates for novel energy storage technology that achieves energy density of 500 Wh·kg^(−1).However,poor cycle stability resulting from notorious shuttle effect and the safety concerns deriving from flammability of ether-based electrolyte hinder the practical application of Li-S batteries.Because of low solubility to polysulfide,high ionic conductivity,and safety property,sulfide-based electrolytes can fundamentally address above issues.It is widely known that the effective transports of both electrons and ions are basic requirement for redox reaction of active materials in cathode.Thereby,construction of fast and stable ionic and electronic transport paths in cathode is especially pivotal for cycle stability of solid-state Li-S batteries(SSLSBs).In this review,we provide research progresses on facilitating transport of charge carriers in composite cathode of SSLSBs.From perspective of materials,intrinsically conductivity of electrolyte and carbon shows dramatic effect on migration of charge carriers in cathode of SSLSBs,thereby the conductive additives are summarized in the manuscript.Additionally,the charge transport in cathode of SSLSBs fully depends on the physical contact between active materials and conductive additives,therefore we summarized the strategies optimizing interfacial contact and reducing interfacial resistance.Finally,potential future research directions and prospects for SSLSBs with improved energy density and cycle performance are also proposed.

Revealing the importance of suppressing formation of lithium hydride and hydrogen in Li anode protection

The reviving of the“Holy Grail”lithium metal batteries(LMBs)is greatly hindered by severe parasitic reactions between Li anode and electrolytes.Herein,first,we comprehensively summarize the failure mechanisms and protection principles of the Li anode.Wherein,despite being in dispute,the formation of lithium hydride(LiH)is demonstrated to be one of the most critical factors for Li anode pulverization.Secondly,we trace the research history of LiH at electrodes of lithium batteries.In LMBs,LiH formation is suggested to be greatly associated with the generation of H_(2)from Li/electrolyte intrinsic parasitic reactions,and these intrinsic reactions are still not fully understood.Finally,density functional theory calculations reveal that H_(2)adsorption ability of representative Li anode protective species(such as LiF,Li_(3)N,BN,Li_(2)O,and graphene)is much higher than that of Li and LiH.Therefore,as an important supplement of well-known lithiophilicity theory/high interfacial energy theory and three key principles(mechanical stability,uniform ion transport,and chemical passivation),we propose that constructing an artificial solid electrolyte interphase layer enriched of components with much higher H_(2)adsorption ability than Li will serve as an effective principle for Li anode protection.In summary,suppressing formation of LiH and H_(2)will be very important for cycle life enhancement of practical LMBs.

Uncovering the critical impact of the solid electrolyte interphase structure on the interfacial stability

Solid electrolyte interphase(SEI)plays a critical role in determining the interfacial stability,which in turn impacts the plating/stripping process of the lithium metal anode.Substantial research has been focused on the composition of SEI and its contribution to the interfacial stability.Herein,we illustrate the significance of SEI structure,in a comprehensive comparison of a diluted electrolyte(1 M LiTFSI-PC)and a super-concentrated electrolyte(8 M LiTFSI-PC).Illustrated by in situ optical and atomic force microscope observation,homogeneous plating on lithium anode is achieved in the concentrated electrolyte.However,x-ray photoelectron spectroscopy and molecular dynamics simulations reveal that,contrary to the general understanding,the components of SEI is nearly identical for lithium anode cycled in both two electrolytes.Detailed characterizations demonstrate the structure of SEI is quite different.In concentrated electrolyte,a compact structure of SEI layer can be obtained,mainly due to the reduced solubility and outstanding formation kinetics of the interfacial layer.This work provided a new understanding to the excellent performance of super-concentrated electrolyte in lithium metal battery.