First Principle Material Genome Approach for All Solid-State Batteries

Due to ever-increasing concern about safety issues in using alkali metal ionic batteries, all solid-state batteries (ASSBs) have attracted tremendous attention. The foundation to enable high-performance ASSBs lies in delivering ultra-fast ionic conductors that are compatible with both alkali anodes and high-voltage cathodes. Such a challenging task cannot be fulfilled, without solid understanding covering materials stability and properties, interfacial reactions, structural integrity, and electrochemical windows. Here in this work, we will review recent advances on fundamental modeling in the framework of material genome initiative based on the density functional theory (DFT), focusing on solid alkali batteries. Efforts are made in offering a dependable road chart to formulate competitive materials and construct "better" batteries.

Li intercalation in an MoSe_(2) electrocatalyst:In situ observation and modulation of its precisely controllable phase engineering for a high-performance flexible Li-S battery

Sophisticated efficient electrocatalysts are essential to rectifying the shuttle effect and realizing the high performance of flexible lithium-sulfur batteries(LSBs).Phase transformation of MoSe_(2) from the 2H phase to the 1T phase has been proven to be a significant method to improve the catalytic activity.However,precisely controllable phase engineering of MoSe_(2) has rarely been reported.Herein,by in situ Li ions intercalation in MoSe_(2),a precisely controllable phase evolution from 2H-MoSe_(2) to 1T-MoSe_(2) was realized.More importantly,the definite functional relationship between cut-off voltage and phase structure was first identified for phase engineering through in situ observation and modulation methods.The sulfur host(CNFs/1T-MoSe_(2))presents high charge density,strong polysulfides adsorption,and catalytic kinetics.Moreover,Li-S cells based on it display capacity retention of 875.3mAh g^(-1) after 500 cycles at 1 C and an areal capacity of 8.71mAh cm^(-2) even at a high sulfur loading of 8.47mg cm^(-2).Furthermore,the flexible pouch cell exhibiting decent performance will endow a promising potential in the wearable energy storage field.This study proposes an effective strategy to precisely control the phase structure of MoSe_(2),which may provide the reference to fabricate the highly efficient electrocatalysts for LSBs and other energy systems.

Insights into electrochemical nitrogen reduction reaction mechanisms:Combined effect of single transition-metal and boron atom

Developing single-atom catalysts(SACs) for electrochemical devices is a frontier in energy conversion.The comparison of stability,activity and selectivity between various single atoms is one of the main research focuses in SACs.However,the in-depth understanding of the role that the coordination atoms of single atom play in the catalytic process is lacking.Herein,we proposed a graphene-like boroncarbon-nitride(BCN) monolayer as the support of single metal atom.The electrocatalytic nitrogen reduction reaction(eNRR) performances of 3 d,4 d transition metal(TM) atoms embedded in defective BCN were systematically investigated by means of density functional theory(DFT) computations.Our study shows that the TM-to-N and B-to-N π-back bonding can contribute to the activation of N_(2).Importantly,a combined effect is revealed between single TM atom and boron atom on eNRR:TM atom enhances the nitrogen reduction process especially in facilitating the N_(2) adsorption and the NH3 desorption,while boron atom modulates the bonding strength of key intermediates by balancing the charged species.Furthermore,Nb@BN3 possesses the highest electrocata lytic activity with limiting potential of-0.49 V,and exhibits a high selectivity for nitrogen reduction reaction(NRR) to ammonia compared with hydrogen evolution reaction(HER).As such,this work can stimulate a research doorway for designing multi-active sites of the anchored single atoms and the innate atoms of substrate based on the mechanistic insights to guide future eNRR research.

Coupling effect of the conductivities of Li ions and electrons by introducing LLTO@C fibers in the LiNi0.8Co0.15Al0.05O2 cathode

To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.

Nitrogen/sulphur dual-doped hierarchical carbonaceous fibers boosting potassium-ion storage

The carbon materials as anode electrodes have been widely studied for potassium ion batteries(PIBs).However,the large size of potassium ions prevents their intercalation/deintercalation,resulting in poor storage behaviors.Herein,a novel design of N/S codoped hierarchical carbonaceous fibers(NSHCF)formed from nanosheets self-assembled by catalyzing Aspergillus niger with Sn is reported.The asprepared NSHCF at 600℃(NSHCF-600)exhibits a high reversible capacity of 345.4 m Ah g^(-1) at 0.1 A g^(-1) after 100 cycles and an excellent rate performance of 124.5 m Ah g^(-1) at 2 A g^(-1).The excellent potassium storage performance can be ascribed to the N/S dual-doping,which enlarges interlayer spacing(0.404 nm)and introduces more defects.The larger interlayer spacing and higher pyridinic N active sites can promote K ions diffusion and storage.In addition,the ex situ transmission electron microscopy reveals the high reversibility of potassiation/depotassiation process and structural stability.

Atomic Layer Coated Al_(2)O_(3) on Nitrogen Doped Vertical Graphene Nanosheets for High Performance Sodium Ion Batteries

Heteroatom doped graphene materials are considered as promising anode for high-performance sodium-ion batteries(SIBs).Defective and porous structure especially with large specific surface area is generally considered as a feasible strategy to boost reaction kinetics;however,the unwanted side reaction at the anode hinders the practical application of SIBs.In this work,a precisely controlled Al_(2)O_(3)coated nitrogen doped vertical graphene nanosheets(NVG)anode material has been proposed,which exhibits excellent sodium storage capacity and cycling stability.The ultrathin Al_(2)O_(3)coating on the NVG is considered to help construct an advantageous interface between electrode and electrolyte,both alleviating the electrolyte decomposition and enhancing sodium adsorption ability.As a result,the optimal Al_(2)O_(3)coated NVG materials delivers a high reversible capacity(835.0 mAh g^(-1))and superior cycling stability(retention of 92.3%after 5000 cycles).This work demonstrates a new way to design graphene-based anode materials for highperformance sodium-ion batteries.

ZnO Interface Modified LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)Toward Boosting Lithium Storage

In this work,an amorphous ZnO was coated on LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)using a sol-gel strategy method.The NCM coated with 1 wt.%Zn O and a thickness of about 3 nm exhibits an improved cycling performance,accompanied by a lower capacity fading(from 194.8 to 133.8 m Ah g^(-1),i.e.,68%)than that of the pristine one(i.e.,only 34%)after 300 cycles at 0.2 C.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)indicate that the Zn O coating can improve extraction/insertion of Li+and inhibit the increase in impedance of the NCM cathode material.This approach may benefit the performance improvement of the Ni-rich cathode materials in Lithium-ion batteries(LIBs).

Influence of Halide Choice on Formation of Low-Dimensional Perovskite Interlayer in Efficient Perovskite Solar Cells

Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.

In-plane grain boundary induced defect state in hierarchical NiCo-LDH and effect on battery-type charge storage

Domain boundaries are regarded as the effective active sites for electrochemical energy storage materials due to defects enrichment therein.However,layered double hydroxides(LDHs)tend to grow into single crystalline nano sheets due to their unique two-dimentional(2D)lattice structure.Previously,much efforts were made on the designing hierarchical structure to provide more exposed electroactive sites as well as accelerate the mass transfer.Herein,we demonstrate a strategy to introduce low angle grain boundary(LAGB)in the flakes of Ni/Co layered double hydroxides(NiCo-LDHs).These defect-rich nano flakes were self-assembled into hydrangea-like spheres that further constructed hollow cage structure.Both the formation of hierarchical structure and grain boundaries are interpreted with the synergistic effect of Ni2+/Co2+ratio in an“etching-growth”process.The domain boundary defect also results in the preferential formation of oxygen vacancy(Vo).Additionally,density functional theory(DFT)calculation reveals that Co substitution is a critical factor for the formation of adjacent lattice defects,which contributes to the formation of domains boundary.The fabricated battery-type Faradaic NiCo-LDH-2 electrode material exhibits significantly enhanced specific capacitance of 899 C·g^(−1)at a current density of 1 A·g^(−1).NiCo-LDH-2//AC asymmetric capacitor shows a maximum energy density of 101.1 Wh·kg^(−1)at the power density of 1.5 kW·kg^(−1).

纳米结构硫化镉光催化分解水产氢综述

太阳能驱动光催化分解水制氢是实现可持续制氢气的一种有效策略.硫化镉半导体光催化剂基于其较强的可见光响应、适宜的氧化还原反应带边位置以及优异的电荷传输性能而备受关注.本文综述了近年来国内外在提高硫化镉基光催化剂制氢性能的设计、改性和制备等方面的研究进展.首先简要介绍了光催化制氢的基本概念和机理,阐述了硫化镉光催化制氢的基本性质、重要进展和瓶颈,综述了该材料的发展前景.随后,重点讨论了硫化镉基光催化剂光催化分解水产氢的各种改性策略,其中有效的策略是产生更多的载流子,促进电荷的有效分离,促进界面电荷转移,加速电荷利用,以及抑制电荷诱导的自光腐蚀.针对每一种改性策略,都详细讨论了影响光催化剂性能的重要因素和未来潜在的研究方向.最后介绍了纳米结构硫化镉和硫化镉基纳米复合材料在光催化分解水产氢中的发展前景和面临的挑战.本综述将为开发镉基半导体光催化剂提供重要和及时的理论指导,并促进其在太阳能氢气生产中的应用.

A review on 2D MoS_(2) cocatalysts in photocatalytic H_(2) production

Owing to their unique physicochemical,optical and electrical properties,two-dimensional(2D)MoS_(2) cocatalysts have been widely applied in designing and developing highly efficient composite photocatalysts for hydrogen generation under suitable light irradiation.In this review,we first elaborated on the fundamental aspects of 2D MoS_(2) cocatalysts to include the structural design principles,synthesis strategies,strengths and challenges.Subsequently,we thoroughly highlighted and discussed the modification strategies of 2D MoS_(2) H2-evolution cocatalysts,including doping heteroatoms(e.g.metals,non-metals,and co-doping),designing interfacial coupling morphologies,controlling the physical properties(e.g.thickness,size,structural defects or pores),exposing the reactive facets or edge sites,constructing cocatalyst heterojunctions,engineering the interfacial bonds and confinement effects.In the future,the forefront challenges in understanding and in precise controlling of the active sites at molecular level or atomic level should be carefully studied,while various potential mechanisms of photogenerated-electrons interactions should be proposed.The applications of MoS_(2) cocatalyst in the overall water splitting are also expected.This review may offer new inspiration for designing and constructing novel and efficient MoS_(2)-based composite photocatalysts for highly efficient photocatalytic hydrogen evolution.

A flexible metallic TiC nanofiber/vertical graphene 1D/2D heterostructured as active electrocatalyst for advanced Li–S batteries

The realistic application of lithium-sulfur(Li-S)batteries has been severely hindered by the sluggish conversion kinetics of polysulfides(LiPS)and inhomogeneous deposition of Li_(2)S at high sulfur loading and low electrolyte/sulfur ratio(E/S).Herein,a flexible Li-S battery architecture based on electrocatalyzed cathodes made of interfacial engineered TiC nanofibers and in situ grown vertical graphene are developed.Integrated 1D/2D heterostructured electrocatalysts are realized to enable highly improved Li^(+)and electron transportation together with significantly enhanced affinity to LiPS,which effectively accelerate the conversion kinetics between sulfur species,and thus induce homogeneous deposition of Li_(2)S in the catalyzed cathodes.Consequently,highly active electro-electrocatalystsbased cells exhibit remarkable rate capability at 2C with a high specific capacity of 971 mAh g^(-1).Even at ultra-high sulfur loading and low E/S ratio,the battery still delivers a high areal capacity of 9.1 mAh cm^(-2),with a flexible pouch cell being demonstrated to power a LED array at different bending angles with a high capacity over 100 cycles.This work puts forward a novel pathway for the rational design of effective nanofiber electrocatalysts for cathodes of high-performance Li-S batteries.

In-situ Construction of Sulfur-doped g-C_(3)N_(4)/defective g-C_(3)N_(4) Isotype Step-scheme Heterojunction for Boosting Photocatalytic H_(2) Evolution

The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H_(2).Unfortunately,the variant energy-level matching between two different semiconductor confers limited the photocatalytic performance.Herein,a newfangled graphitic-carbon nitride(g-C_(3)N_(4))based isotype step-scheme heterojunction,which consists of sulfur-doped and defective active sites in one microstructural unit,is successfully developed by in-situ polymerizing N,N-dimethylformamide(DMF)and urea,accompanied by sulfur(S)powder.Therein,the polymerization between the amino groups of DMF and the amide group of urea endows the formation of rich defects.The propulsive integration of S-dopants contributes to the excellent fluffiness and dispersibility of lamellar g-C_(3)N_(4).Moreover,the developed heterojunction exhibits a significantly enlarged surface area,thus leading to the more exposed catalytically active sites.Most importantly,the simultaneous introduction of S-doping and defects in the units of g-C_(3)N_(4) also results in a significant improvement in the separation,transfer and recombination efficiency of photo-excited electron-hole pairs.Therefore,the resulting isotype step-scheme heterojunction possesses a superior photocatalytic H_(2) evolution activity in comparison with pristine g-C_(3)N_(4).The newly afforded metal-free isotype step-scheme heterojunction in this work will supply a new insight into coupling strategies of heteroatoms doping and defect engineering for various photocatalytic systems.

g-C_(3)N_(4) encapsulated ZrO_(2) nanofibrous membrane decorated with CdS quantum dots: A hierarchically structured, self-supported electrocatalyst toward synergistic NH3 synthesis

The advancement of electrocatalytic N2 reduction reaction (NRR) toward ambient NH3 synthesis lies in the development of more affordable electrocatalysts than noble metals. Recently, various nanostructures of transition metal compounds have been proposed as effective electrocatalysts;however, they exist in the form of loose powders, which have to be immobilized on a matrix before serving as the electrode for electrolysis. The matrix, being it carbon paper, carbon cloth or metal foam, is electrocatalytically inactive, whose introduction inevitably raises the invalid weight while sacrificing the active sites of the electrode. Herein, we report on the fabrication of a flexible ZrO2 nanofibrous membrane as a novel, self-supported electrocatalyst. The heteroatom doping can not only endow the nanofibrous membrane with excellent flexibility, but also induce oxygen vacancies which are responsible for easier adsorption of N2 on the ZrO2 surface. To improve the electrocatalytic activity, a facile SILAR approach is employed to decorate it with CdS quantum dots (QDs), thereby tuning its Fermi level. To improve the conductivity, a g-C3N4 nanolayer is further deposited which is both conductive and active. The resulting hierarchically structured, self-supported electrocatalyst, consisting of g-C3N4 encapsulated ZrO2 nanofibrous membrane decorated with CdS QDs, integrates the merits of the three components, and exhibits a remarkable synergy toward NRR. Excellent NH3 yield of 6.32 × 10−10 mol·s−1cm−2 (−0.6 V vs. RHE) and Faradaic efficiency of 12.9% (−0.4 V vs. RHE) are attained in 0.1 M Na2SO4.

Uncovering the Mechanism for Urea Electrochemical Synthesis by Coupling N2 and CO_(2) on Mo2C-MXene

In this work, the catalytic activities of MoC-MXene for the co-synthesis of urea from Nand COare reported by well-defined density functional theory(DFT) method. The calculated results show that the presence of surface functional groups is not conducive to the CO/N(C/N) coupling process in urea synthesis reaction. The exposed MoC on the surface can realize urea synthesis at the limit point of 0.69 eV, but the large transition state energy barrier(1.50 eV)indicates that bare MoC is not a promising urea catalyst. Loading single atoms can improve the urea synthesis performance of bare MoC. The energy barrier of urea synthesis reaction and the transition state energy barrier of C/N coupling reaction have dropped significantly by the atomic loading of Fe and Ti on bare MoC. Moreover, Ti doped MoC exhibits better catalytic selectivity toward urea production, making it an excellent catalyst for urea synthesis. We hope this work can pave the way for the electrochemical synthesis of urea.

Complex permittivity-dependent plasma confinement-assisted growth of asymmetric vertical graphene nanofiber membrane for high-performance Li-S full cells

Vertical graphene(VG),possessing superior chemical,physical,and structural peculiarities,holds great promise as a building block for constructing a high-energy density lithium-sulfur(Li-S)battery.Therefore,it is desirable to develop a new VG growth technique with a novel structure to enable wide applications.Herein,we devise a novel complex permittivity-dependent plasma confinement-assisted VG growth technique,via asymmetric growing a VG layer on one side of N-doped carbon nanofibers for the first time,using a unique lab-built high flux plasma-enhanced chemical vapor deposition system,as a bifunctional nanofiber membrane to construct Li-S batteries with low neg-ative/positive(N/P)and electrolyte/sulfur(E/S)ratios.The unique nanofiber membrane could simultaneously protect the cathode and anode,enabling an excellent electrochemical performance with low N/P and E/S ratios in Li-S bat-teries.Such a full cell delivers high gravimetric energy density and volumetric energy density of 340 Wh kg^(-1) and 547 Wh L^(-1),respectively,at low N/P(2:1)and E/S(4:1)ratios.Furthermore,a pouch cell achieves a high areal capacity of 7.1 mAh cm^(-2) at a sulfur loading of 6 mg cm^(-2).This work put forward a novel pathway for the design of high-energy density Li-S batteries.

Computational screening study of double transition metal carbonitrides M′_(2)M″CNO_(2)-MXene as catalysts for hydrogen evolution reaction

Two-dimensional(2D)transition metal carbonitrides(MXene)have attracted growing interest in electrocatalytic hydrogen production due to its structural and electronic properties.In this work,the hydrogen evolution reaction(HER)activity of all 64 Oterminated ordered double transition metal carbonitrides in the form of M′_(2)M″CNO_(2)(M′=Ti,V,Cr,Zr,Nb,Mo,Hf,Ta;M″=Ti,V,Cr,Zr,Nb,Mo,Hf,Ta)has been investigated by well-defined density functional theory(DFT)calculations.The results indicate that there are 11M′_(2)M″CNO_(2)-MXene candidates whose HER performance is superior to that of Pt.Moreover,according to the stability screening,it is proved that Ti_(2)NbCNO_(2),Mo_(2)TiCNO_(2),and Ti_(2)VCNO_(2) are more stable than other candidates.Especially,Ti_(2)NbCNO_(2) have the potential to be perfect HER catalyst with the small Gibbs free energies of hydrogen adsorption(ΔGH)value of 0.02 eV,abundant catalytic sites on the C-side,and better stability.This work paves the way on designing excellent HER catalyst candidates based on M′_(2)M″CNO_(2)-MXenes.

Regulation of the pore structure of carbon nanosheets based electrocatalyst for efficient polysulfides phase conversions

The practical applications of lithium-sulfur(Li-S)batteries are hampered by the sluggish redox kinetics and polysulfides shuttle in the cyclic process,which leads to a series of problems including the loss of active materials and poor cycling efficiency.In this paper,the pore structures of carbon nanosheets based electrocatalysts were precisely controlled by regulating the content of water-soluble KCl template.The relationship between pore structures and Li-S electrochemical behavior was studied,which demonstrates a key influence of pore structure in polysulfides phase conversions.In the liquid-sloid redox reaction of polysulfides,the micropores and small mesopores(d<20 nm)exhibited little impact,while the meso-pores(d>20 nm)and macropores played a decisive role.As a typical exhibition,the nickel-embedded carbon nanosheets(Ni-CNS)with a high content of large mesopores and macropores can aid Li-S batteries in exhibiting stable cycling performance(760.1 mAh g^(-1)at 1 C after 300 cycles)and superior rate capac-ity(847.8 mAh g^(-1)at 2 C).Furthermore,even with high sulfur loading(8 mg cm^(−2))and low electrolyte(E/S is around 6μL mg^(-1)),the high area capacity of 7.7 mAh cm^(−2)at 0.05 C could be achieved.This work can provide a guideline for the design of the pore structure of carbon-based electrocatalysts toward high-efficiency sulfur species redox reactions,and afford a general,controllable,and simple approach to constructing high performance Li-S batteries.