A Review on Engineering Design for Enhancing Interfacial Contact in Solid-State Lithium–Sulfur Batteries

The utilization of solid-state electrolytes(SSEs)presents a promising solution to the issues of safety concern and shuttle effect in Li–S batteries,which has garnered significant interest recently.However,the high interfacial impedances existing between the SSEs and the electrodes(both lithium anodes and sulfur cathodes)hinder the charge transfer and intensify the uneven deposition of lithium,which ultimately result in insufficient capacity utilization and poor cycling stability.Hence,the reduction of interfacial resistance between SSEs and electrodes is of paramount importance in the pursuit of efficacious solid-state batteries.In this review,we focus on the experimental strategies employed to enhance the interfacial contact between SSEs and electrodes,and summarize recent progresses of their applications in solidstate Li–S batteries.Moreover,the challenges and perspectives of rational interfacial design in practical solid-state Li–S batteries are outlined as well.We expect that this review will provide new insights into the further technique development and practical applications of solid-state lithium batteries.

Improving the interfacial contact between CH_3NH_3PbI_(3–x)Cl_x and Au by LiTFSI solution treatment for efficient photoelectric devices

Organic lead halide compounds with perovskite structure become a promising photovoltaic material for low- cost thin film solar cells in recent years. The property of perovskite/metal interface is a fundamental topic for the effective charge transfer at metal electrodes. In this work, we develop an interface modification method of lithium bis（trifluoromethane sulfonimide） （LiTFSI） solution treatment, which can effectively decrease the charge transfer resistance at the CH3NHaPbI3_xClx/Au interface. After the solution treatment, uniform nan- odots are formed at the surface of CHaNH3PbI3_xCIx films, and the barrier height at CH3NH3PbI3_xCIx/Au interface reduces from 0.51 V to 0.08 V. As a consequence, the efficiency of hole conductor free solar cells with CH3NHaPbI3-xCIx harvester increase from 4.0% to 7.6% under one sun condition. It is also found that the hole conductor free perovskite solar cell can work in a photodetector mode, which has the same output prop- erties with phototransistors. After the LiTFSI solution treatment, the sensitivity of this photodetector can be improved for about one time.

CNTs@S composite as cathode for all-solid-state lithium-sulfur batteries with ultralong cycle life

The main challenges in development of traditional liquid lithium-sulfur batteries are the shuttle effect at the cathode caused by the polysulfide and the safety concern at the Li metal anode arose from the dendrite formation.All-solid-state lithium-sulfur batteries have been proposed to solve the shuttle effect and prevent short circuits.However,solid-solid contacts between the electrodes and the electrolyte increase the interface resistance and stress/strain,which could result in the limited electrochemical performances.In this work,the cathode of all-solid-state lithium-sulfur batteries is prepared by depositing sulfur on the surface of the carbon nanotubes(CNTs@S)and further mixing with Li10GeP2S12 electrolyte and acetylene black agents.At 60℃,CNTs@S electrode exhibits superior electrochemical performance,delivering the reversible discharge capacities of 1193.3,959.5,813.1,569.6 and 395.5 mAhg^-1 at the rate of 0.1,0.5,1,2 and 5 C,respectively.Moreover,the CNTs@S is able to demonstrate superior high-rate capability of 660.3 mAhg^-1 and cycling stability of 400 cycles at a high rate of 1.0 C.Such uniform distribution of the CNTs,S and Li10GeP2S12 electrolyte increase the electronic and ionic conductivity between the cathode and the electrolyte hence improves the rate performance and capacity retention.

Influence of Deposition Temperature on the Electrical and Electrochemical Properties of Carbon-Based Coatings for Metallic Bipolar Plates, Prepared by Cathodic Arc Evaporation

Cathodic arc evaporation is a well-established physical vapor deposition technique which is characterized by a high degree of ionization and high deposition rate. So far, this technique has been mainly used for the deposition of tribological coatings. In this study, anti-corrosive and electrical conductive carbon-based coatings with a metallic interlayer were prepared on stainless steel substrates as surface modification for metallic bipolar plates. Hereby, the influence of the deposition temperature during the deposition of the carbon top layer was investigated. Raman spectroscopy revealed differences in the microstructure at 200°C compared to 300°C and 100°C. Measurements of the interfacial contact resistance showed that the deposited coatings significantly improve the electrical conductivity. There are only minor differences between the different carbon top layers. The corrosion resistance of the coatings was studied via potentiodynamic polarization at room temperature and 80°C. Experiments showed that the coating with a carbon top layer deposited at 200°C, considerably reduces the current density and thus corrosion of the substrate is suppressed.

Self assembled electron blocking and lithiophilic interface towards dendrite-free solid-state lithium battery

The poor interfacial contact is one of the biggest challenges that solid-state lithium batteries suffer from.Reducing the solid-state electrolyte surface energy by transforming the interface from lithiophobic to lithiophilic is effective to promote the interfacial contact, but electronic conductive interphases usually increase the risk of electron attack, thus leading to uncontrollable Li dendrite growth. Herein, we propose a self-assembled thermodynamic stable Li I interphase to simultaneously improve the interfacial contact between the garnet electrolyte Li_7La_(3)Zr_(2)O_(12)(LLZO) and Li anode, and prohibit the electron attack. The direct contact between LLZO and Li and the high temperature Li melting process was ascribed to Zr4+reduction, which facilitated Li dendrite formation and propagation. With the modification of the high lithiophilic I_(2) thin film, the area specific interfacial resistance of LLZO/Li was reduced from 1525 Ω/cm^(2) to 57 Ω/cm^(2). More importantly, LLZO was protected from being reduced due to the outstanding electronic insulativity of the Li I interphase, which leaded to a high critical current density of 1.2/7.0 m A/cm^(2) in the time/capacity-constant modes, respectively.

Design and fabrication of bipolar plates for PEM water electrolyser

Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy carrier steadily accelerates the development of hydrogen production processes,and therein proton exchange membrane(PEM)water electrolysis is deemed a promising long-term strategy for hydrogen preparation and collection.This review retrospects recent developments and applications of bipolar plates(BPs)as key components in PEM fuel cells and water electrolysers.The main content includes multifaceted challenges in the R&D or fabrication of BPs and potential future trends have also been proposed.Specific details cover the BPs matrix(metallic materials and carbon composites)and the surface coating types(metal and compound coatings,carbon-based coatings,and polymer coatings),as well as the influence of flow field design for mass transport.Long-term development and feasible researches of BPs are prospected.Especially in the following aspects:(1)Structural and functional integration of components,such as material fabrication and flow field geometry optimization using 3D printing technology;(2)Introduction of environment-friendly renewable energy for hydrogen production;(3)Research on hydrogen energy reversible systems;(4)Composition optimization of surface coatings based on computational materials science and(5)systematic design expected to evolve into the next generation of BPs.

In-MOF-derived In_(2)S_(3)/Bi_(2)S_(3) heterojunction for enhanced photocatalytic hydrogen production

Transition metal sulfides are commonly studied as photocatalysts for water splitting in solar-to-fuel conversion.However,the effectiveness of these photoca-talysts is limited by the recombination and restricted light absorption capacity of carriers.In this paper,a broad spectrum responsive In_(2)S_(3)/Bi_(2)S_(3)heterojunction is cons-tructed by in-situ integrating Bi_(2)S_(3)with the In_(2)S_(3),derived from an In-MOF precursor,via the high-temperature sulfidation and solvothermal methods.Benefiting from the synergistic effect of wide-spectrum response,effective charge separation and transfer,and strong heterogeneous interfacial contacts,the In_(2)S_(3)/Bi_(2)S_(3)heterojunction demons-trates a rate of 0.71 mmol/(g∙h),which is 2.2 and 1.7 times as much as those of In_(2)S_(3)(0.32 mmol/(g∙h))and Bi_(2)S_(3)(0.41 mmol/(g∙h)),respectively.This paper provides a novel idea for rationally designing innovative heterojunc-tion photocatalysts of transition metal sulfides for photocatalytic hydrogen production.

Solar fuel generation over nature-inspired recyclable TiO_(2)/g-C_(3)N_(4)S-scheme hierarchical thin-film photocatalyst

Preparation of efficient photocatalysts with ease of recovery in solar fuel generation is highly desired to achieve carbon neutralization in carbon dioxide(CO_(2))emissions.Inspired from the forest with superior light penetration and fast gas transport,a TiO_(2)/g-C_(3)N_(4)composite nanowire arrays(NAs)film with maximized light utilization is devised.It is achieved by in-situ coating a thin layer of g-C_(3)N_(4)(as the leaf)on the vertically-oriented TiO_(2)arrays(as tree trunks)on Ti foil(as soil).Benefiting from the effective charge separation by S-scheme charge transfer,intimate contact by the in-situ growth as well as the ingenious structure,the composite,readily recyclable,displays exciting performance in photocatalytic CO_(2)reduction.It is beyond doubt that the combination of heterojunction construction and“nature-inspired biomimetic photocatalyst”design promises practical applications and industrial use.

Electrochemical Properties of Tungsten-Alloying-Modified AISI 430 Stainless Steel as Bipolar Plates for PEMFCs used in Marine Environment

To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel （430 SS） as bipolar plates for proton exchange membrane fuel cells （PEMFCs） used in marine environment, a tungsten alloying layer has been successfully prepared on 430 SS substrate via the plasma surface diffusion alloying technique. The tungsten- modified （W-modified） 430 SS displays a 7-8 Ixm tungsten alloying layer with a body-centered-cubic structure. The W-modified surface also shows a better hydrophobicity with contact angle of 93.5~ and a lower interfacial contact resistance compared with the untreated 430 SS. The potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy measurements show that the corrosion resistance of 430 SS is obviously improved in simulated PEMFC environment （0.05 M H2SO4 ＋ 2 ppm HF ＋ 0.01 M NaC1 solution at 70℃）, after the plasma surface diffusion alloying process.

Construction of 1D/1D WO3 Nanorod/TiO2 Nanobelt Hybrid Heterostructure for Photocatalytic Application

In this work,well-defined 1D/1D WO3 nanorod/TiO2 nanobelt(WNR/TNB)hybrid heterostructure was fabricated by a simple electrostatic self-assembly method.The structure-property correlation was clarified by characterizing the crystal phases,morphologies,optical properties,photoluminescence and photocatalytic performances of the WNR/TNB heterostructures.It was demonstrated that photocatalytic performances of WNR/TNB heterostructure toward mineralization was superior to blank TNB,WNR and randomly mixed counterparts under simulated solar light irradiation,owing predominantly to the intimate interfacial contact between WNR and TNB,forming intimately integrated heterojunction,which promotes the spatial charge carriers transfer and electron relay,hence prolonging the lifetime of photogenerated electron-hole pairs.Moreover,photocatalytic mechanism was elucidated.It is anticipated that our work would provide an alternative strategy to construct diverse heterostructured photocatalysts for solar energy conversion.

Performance of Nb_(0.8)Zr_(0.2) Layer-Modified AISI430 Stainless Steel as Bipolar Plates for Direct Formic Acid Fuel Cells

To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel(430 SS)as bipolar plates for direct formic acid fuel cells(DFAFCs),a Nb_(0.8)Zr_(0.2) layer has been successfully synthesized via the pulsed laser deposition(PLD)technique on the surface of 430 SS.This Nb_(0.8)Zr_(0.2) layer is smooth,uniform,and comparatively compact without any surface flaw and micropore.Investigation under the simulated anodic environment of DFAFCs(0.05 M H_(2)SO_(4)+2 ppm HF+10 M HCOOH at 70℃)shows that the corrosion resistance of 430 SS is obviously ameliorated after the PLD modification.In addition,the interfacial contact resistance of Nb_(0.8)Zr_(0.2)-430 SS(6.0 mΩcm^(2))is much smaller than that of bare 430 SS(151.3 mΩcm^(2))at the clamping force of 140 N cm^(-2).Besides,diff erent from the highly increased interfacial contact resistance of bare 430 SS,the Nb_(0.8)Zr_(0.2)-430 SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.

Ultrathin ZnIn_(2)S_(4)Nanosheets-Supported Metallic Ni_(3)FeN for Photocatalytic Coupled Selective Alcohol Oxidation and H_(2)Evolution

Photocatalytic anaerobic organic oxidation coupled with H_(2)evolution represents an advanced solar energy utilization strategy for the coproduction of clean fuel and fine chemicals.To achieve a high conversion efficiency,the smart design of efficient catalysts by the right combination of semiconductor light harvesters and cocatalyst is highly required.Herein,we report a composite photocatalyst composed of noble metal-free transition metal nitride Ni_(3)FeN decorated on 2D ultrathin ZnIn_(2)S_(4)(ZIS)nanosheets for selective oxidation of aromatic alcohols to aldehydes pairing with H_(2)production.In the composite,ultrathin ZIS serves as a light harvester that greatly shortens the diffusion length of photogenerated charges,while the metallic nitride Ni_(3)FeN acts as an advanced cocatalyst which not only captures the photoelectrons generated from the ultrathin ZIS to promote the charge separation,but also provides active sites to lower the overpotential and accelerate the H_(2)reduction.The best photocatalytic performance is found on ZIS/1.5%M-Ni_(3)FeN,which shows a H_(2)generation rate of 2427.9μmol g^(^(-1))h^(-1)and a benzaldehyde(BAD)production rate of 2460μmol g^(-1)h^(-1),about 7.8-fold as high as that of bare ZIS.This work is anticipated to endorse the exploration of transition metal nitrides as high-performance cocatalysts to promote the coupled photocatalytic organic transformation and H_(2)production.

Spontaneous escape behavior of silver from graphite-like carbon coating and its inhibition mechanism

A series of silver-doped graphite-like carbon coatings was prepared on the surface of aluminum alloy using the magnetron sputtering method. The spontaneous escape behavior and inhibition mechanism of silver from graphite-like carbon coating were studied. The results showed that when the sample prepared with a 0.01-A current on the silver target was placed in an atmospheric environment for 0.5 h, an apparent silver escape phenomenon could be observed. However, the silver escape phenomenon was not observed for samples prepared with a 0.05-A current on the silver target if the sample was retained in a 10^（-1） Pa vacuum environment, even after 48 h. Compared with the sample placed in the atmospheric environment immediately after an ion plating process, the silver escape time lagged for 6 h. Nanometer-thick pure carbon coating coverage could effectively suppress silver escape. When the coating thickness reached700 nm, permanent retention of silver could be achieved in the silver-doped graphite-like carbon coating.As the silver residue content in the graphite-like carbon coating increased from 2.27 at.% to 5.35 at.%, the interfacial contact resistance of the coating decreased from 51mΩcm^2 to 6 mΩcm^2.

Improving the device performances of two-dimensional semiconducting transition metal dichalcogenides: Three strategies

Two-dimensional(2D)semiconductors are emerging as promising candidates for the next-generation nanoelectronics.As a type of unique channel materials,2D semiconducting transition metal dichalcogenides(TMDCs),such as MoS2 and WS2,exhibit great potential for the state-of-the-art fieldeffect transistors owing to their atomically thin thicknesses,dangling-band free surfaces,and abundant band structures.Even so,the device performances of 2D semiconducting TMDCs are still failing to reach the theoretical values so far,which is attributed to the intrinsic defects,excessive doping,and daunting contacts between electrodes and channels.In this article,we review the up-to-date three strategies for improving the device performances of 2D semiconducting TMDCs:(i)the controllable synthesis of wafer-scale 2D semiconducting TMDCs single crystals to reduce the evolution of grain boundaries,(ii)the ingenious doping of 2D semiconducting TMDCs to modulate the band structures and suppress the impurity scatterings,and(iii)the optimization design of interfacial contacts between electrodes and channels to reduce the Schottky barrier heights and contact resistances.In the end,the challenges regarding the improvement of device performances of 2D semiconducting TMDCs are highlighted,and the further research directions are also proposed.We believe that this review is comprehensive and insightful for downscaling the electronic devices and extending the Moore’s law.