Thin buffer layer assist carbon-modifying separator for long-life lithium metal anodes

The guided Li dendrite growth by carbon-modifying separator is believed to be an effective strategy for enhancing life of lithium metal batteries(LMBs).However,the weak adhesions,as well as the large interface impedance between the smooth separator and the carbon functional layer(CFL) lead to an easily peeling of the CFL after repetitive cycles.Herein,we propose a promising solution by an inserting thin buffer layer(TBL) to strengthen the adhesion between CFL and separator as a double modifying layer(C-TBL) of the LMBs separator,which greatly improves the stability of the CFL and provides an effective Li metal anode protection.Owing to the sufficient ionic conductivity,chemical stability and strong adhesion to the separator of the TBL,it can avoid the failure of the CFL functionality with small interface impedance.Moreover,the CFL effectively reduces localized flux of Li+ through its abundant pores.The Li/Li cell with C-TBL separator displays the Li dendrite-free and stable cycling performance for at least 1500 h.When LiFePO_(4)(LFP) is employed as the cathode electrode,the assembled full cell with C-TBL separator shows the excellent rate performance and outstanding cycling capability.Our study builds a stable Li+conducting "bridge" between the functional layer and the separator in stabilizing Li metal anode,and provides a fresh idea of the artificial separator of LMBs.

MXenes for metal-ion and metal-sulfur batteries:Synthesis,properties,and electrochemistry

In 2011,a new class of 2D materials was discovered;after 2012,they began to be concerned;in 2017,the“gold rush”of the materials was triggered,and they are exactly MXenes.2D MXenes,a new class of transition metal carbides,carbonitrides and nitrides,have become the star and cutting-edge research materials in the field of emerging batteries systems due to their unique 2D structure,abundant surface chemistry,and excellent physical and electrochemical properties.This review focuses on the MXene materials and summarizes the recent advancements in the synthesis techniques and properties,in addition to a detailed discussion on the electrochemical energy storage applications,including alkali-ion(Li^(+),Na^(+),K^(+))storage,lithium-sulfur(Li–S)batteries,sodiumsulfur(Na–S)batteries,and metal anode protection.Special attentions are given to the elaborate design of nano-micro structures of MXenes for the various roles as electrodes,multifunctional components,S hosts,modified separators,and metal anode protective layers.The paper ends with a prospective summary of the promising research directions in terms of synthesis,structure,properties,analysis,and production on MXene materials.

Interface issues of lithium metal anode for high-energy batteries: Challenges, strategies, and perspectives

Lithium(Li)metal is considered as one of the most promising anode materials for next-generation high-energy-density storage systems.However,the practical application of Li metal anode is hindered by interfacial instability and air instability due to the highly reactivity of Li metal.Unstable interface in Li metal batteries(LMBs)directly dictates Li dendrite growth,“dead Li”and low Coulombic efficiency,resulting in inferior electrochemical performance of LMBs and even safety issues.In addition,its sensitivity to ambient air leads to the severe corrosion of Li metal anode,high requirements of production and storage,and increased manufacturing cost.Plenty of efforts in recent years have overcome many bottlenecks in these fields and hastened the practical applications of high-energy-density LMBs.In this review,we focus on emerging methods of these two aspects to fulfill a stable and low cost electrode.In this perspective,design artificial solid electrolyte interphase(SEI)layers,construct three-dimensional conductive current collectors,optimize electrolytes,employ solid-state electrolytes,and modify separators are summarized to be propitious to ameliorate interfacial stability.Meanwhile,ex situ/in situ formed protective layers are highlighted in favor of heightening air stability.Finally,several possible directions for the future research on advanced Li metal anode are addressed.

Highly efficient catalytic scavenging of oxygen free radicals with graphene-encapsulated metal nanoshields

Normal levels of oxygen free radicals play an important role in cellular signal transduction, redox homeostasis, regulatory pathways, and metabolic processes. However, radiolysis of water induced by high-energy radiation can produce excessive amounts of exogenous oxygen free radicals, which cause severe oxidative damages to all cellular components, disrupt cellular structures and signaling pathways, and eventually lead to death. Herein, we show that hybrid nanoshields based on single-layer graphene encapsulating metal nanoparticles exhibit high catalytic activity in scavenging oxygen superoxide （·O2^-）, hydroxyl （·OH）, and hydroperoxyl （HO2·） free radicals via electron transfer between the single-layer graphene and the metal core, thus achieving biocatalytic scavenging both in vitro and in vivo. The levels of the superoxide enzyme, DNA, and reactive oxygen species measured in vivo dearly show that the nanoshields can efficiently eliminate harmful oxygen free radicals at the cellular level, both in organs and circulating blood. Moreover, the nanoshields lead to an increase in the overall survival rate of gamma ray-irradiated mice to up to 90%, showing the great potential of these systems as protective agents against ionizing radiation.

Garnet/polymer hybrid ion-conducting protective layer for stable lithium metal anode

Rechargeable Li metal batteries using Li metal anodes have attracted worldwide interest because of their high energy density. The critical barriers limiting their commercial application include uncontrolled dendritic Li growth and the unstable Li-electrolyte interface. Considerable efforts have been directed towards solving these problems, e.g., modifying the electrolyte, creating artificial interfacial layers for the Li metal, and constructing three-dimensional structures for the Li metal. However, stabilizing the Li metal interface remains challenging because of the highly reactive nature of the Li metal. In this study, we utilize a Li-ion conducting hybrid film comprising a garnet-type ion conductor and a poly（ethylene oxide）-based polymer electrolyte as a protective layer to stabilize the Li-electrolyte interface and mitigate the growth of Li dendrites. The hybrid ion-conducting layer can block Li dendrites from proliferating and accommodate Li volume expansion because of its robust mechanical properties. Moreover, the ion-conducting layer allows Li deposition only underneath it, rather than on the surface, functioning as a permanent protective layer to ensure the stability of the Li metal over a long cycling life. The dendrite-inhibiting effect of the ion-conducting protective layer is visually evidenced by in situ microscopy using planar batteries. The protective Li metal anode exhibits excellent cycling stability and low voltage hysteresis （-15 mV at 0.2 mA-cm-2） for a cycle life as long as 1,000 h. It also shows a high Coulombic efficiency （-99.5%） in a full cell against a LiFePO4 cathode, exhibiting promise for application in Li metal batteries. Our results imply that the ion-conducting protective layer markedly improves the metal anode, yielding safe, long-life, and high-energy-density batteries.

MXene derivative Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure as bi-functional barrier for Li-S batteries

The shuttle effect of polysulfides during the charging and discharging of lithium-sulfur(Li-S)batteries and the growth of Li dendrites are crucial obstacles to hinder the commercialization of Li-S batteries.Heterostructure engineering is an effective strategy to accelerate catalytic conversion and suppress the dissolution of polysulfides.Herein,we report a Ta_(4)C_(3)-Ta_(2)O_(5) heterostructure composite as a bi-functional modified separator that not only achieves effective protection for lithium metal but also accelerates the polysulfides redox kinetics process.This heterostructure possesses efficient chemical anchoring and abundant active sites to immobilize polysulfides by synergistic effect,which endows a stable long cycling performance for Li-S batteries.This corresponds to an initial high capacity of 801.9 mAh g^(–1) at 1 C with a decay rate of 0.086%for 500 cycles.Due to its high Young’s modulus(up to 384 GPa),Ta_(4)C_(3) contributes to forming a protective layer on the Li metal surface to inhibit the growth of Li dendrites.Accordingly,the symmetrical cell has a stable overpotential for 700 cycles at 20 mA cm^(–2)/20 mAh cm^(–2).So,this“one stone two birds”design affords a novel perspective for high-energy Li-S battery storage system design and Li metal protection.

Electrical and Corrosion Properties of Titanium Aluminum Nitride Thin Films Prepared by Plasma-Enhanced Atomic Layer Deposition

Titanium-aluminum-nitride（TiAlN） films were grown by plasma-enhanced atomic layer deposition（PEALD）on 316 L stainless steel at a deposition temperature of 200 °C. A supercycle, consisting of one AlN and ten TiN subcycles, was used to prepare TiAlN films with a chemical composition of Ti（0.25）Al（0.25）N（0.50）. The addition of AlN to TiN resulted in an increased electrical resistivity of TiAlN films of 2800 μΩ cm, compared with 475 μΩ cm of TiN films, mainly due to the high electrical resistivity of AlN and the amorphous structure of TiAlN. However, potentiostatic polarization measurements showed that amorphous TiAlN films exhibited excellent corrosion resistance with a corrosion current density of 0.12 μA/cm^2, about three times higher than that of TiN films, and about 12.5 times higher than that of 316 L stainless steel.