Interface-reinforced solid-state electrochromic Li-ion batteries enabled by in-situ liquid-solid transitional plastic glues

The electrochromic Li-ion batteries(ELIBs) combine the functions of electrochromism and energy storage,realizing the display of energy-storage levels by visual signals. However, the accompanying interfacial issues including physical contact and(electro)chemical stability should be taken into account when the conventional liquid/gel electrolytes are replaced with solid-state counterparts. Herein, the in-situ liquid-solid transitional succinonitrile(SCN) plastic glues are constructed between electrodes and poly(ethylene oxide)(PEO) polymer electrolytes, enabling an interface-reinforced solid-state ELIB.Specifically, the liquid SCN precursor can adequately wet electrode/PEO interfaces at high temperature,while it returns back to solid state at room temperature, leading to seamless interfacial contact and smooth ionic transfer without changing the solid state of the device. Moreover, the SCN interlayer suppresses the direct contact of PEO with electrodes containing high-valence metal ions, evoking the improved interfacial stability by inhibiting the oxidation of PEO. Therefore, the resultant solid-state ELIB with configuration of LiMn_(2)O_(4)/SCN-PEO-SCN/WO_(3) delivers an initial discharge capacity of 111 m A h g^(-1) along with a capacity retention of 88.3% after 200 cycles at 30 ℃. Meanwhile, the electrochromic function is integrated into the device by distinguishing its energy-storage levels through distinct color changes. This work proposes a promising solid-state ELIB with greatly reinforced interfacial compatibility by introducing in-situ solidified plastic glues.

Two-Dimensional Graphitic Carbon-Nitride(g-C_(3)N_(4))-Coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)Cathodes for High-Energy-Density and Long-Life Lithium Batteries

High-capacity nickel-rich layered oxides are promising cathode materials for high-energy-density lithium batteries.However,the poor structural stability and severe side reactions at the electrode/electrolyte interface result in unsatisfactory cycle performance.Herein,the thin layer of two-dimensional(2D)graphitic carbon-nitride(g-C_(3)N_(4))is uniformly coated on the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(denoted as NCM811@CN)using a facile chemical vaporization-assisted synthesis method.As an ideal protective layer,the g-C_(3)N_(4)layer effectively avoids direct contact between the NCM811 cathode and the electrolyte,preventing harmful side reactions and inhibiting secondary crystal cracking.Moreover,the unique nanopore structure and abundant nitrogen vacancy edges in g-C_(3)N_(4)facilitate the adsorption and diffusion of lithium ions,which enhances the lithium deintercalation/intercalation kinetics of the NCM811 cathode.As a result,the NCM811@CN-3wt%cathode exhibits 161.3 mAh g^(−1)and capacity retention of 84.6%at 0.5 C and 55°C after 400 cycles and 95.7 mAh g^(−1)at 10 C,which is greatly superior to the uncoated NCM811(i.e.129.3 mAh g^(−1)and capacity retention of 67.4%at 0.5 C and 55°C after 220 cycles and 28.8 mAh g^(−1)at 10 C).The improved cycle performance of the NCM811@CN-3wt%cathode is also applicable to solid–liquid-hybrid cells composed of PVDF:LLZTO electrolyte membranes,which show 163.8 mAh g^(−1)and the capacity retention of 88.1%at 0.1 C and 30°C after 200 cycles and 95.3 mAh g^(−1)at 1 C.

Sandwiched N-carbon@Co_(9)S_(8)@Graphene nanosheets as high capacity anode for both half and full lithium-ion batteries

Transition metal sulfides(TMSs) are promising candidates for replacing graphite anode in LIBs. However,the low conductivity and structural collapse caused by the large volume change during lithium insertion and extraction greatly limit its application. Herein, we report a unique design of a two-dimensional(2 D) sandwich structure of N-doped carbon@Co9 S8@graphene(N–C@Co9 S8@G) with multilayer structure. Electrochemical tests reveal that the N–C@Co9 S8@G nanosheets possess a high reversible capacity(1009 mAhg^(-1) at 0.1 Ag^(-1)), and excellent rate capability(422mAhg^(-1) at 10 Ag^(-1)) and long cycle life(853 m Ahg^(-1) at 1Ag^(-1) for 500 cycles). Experimental studies reveal that capacitive storage contributes to the high reversible capacity. The lithium storage kinetics are studied by Galvanostatic intermittent titration technique(GITT) and electrochemical impedance spectroscopy(EIS). Meanwhile, the potential of N–C@Co9 S8@G anode in a full cell using Li Co O2 as the cathode is also demonstrated, exhibiting a high reversible capacity of 300mAhg^(-1) cycles at 0.1Ag^(-1). The strategy proposed in this work paves the way to engineering high performance anodes in LIBs.

Dendrite-structured FeF_(2) consisting of closely linked nanoparticles as cathode for high-performance lithium-ion capacitors

Lithium-ion capacitors(LICs)are regarded as a good choice for next-generation energy storage devices,which are expected to exhibit high energy densities,high power densities,and ultra-long cycling stability.Nevertheless,only a few battery-type cathode materials with limited kinetic properties can be employed in LICs,and their electrochemical properties need to be optimized urgently.Here,we exploit a new dendrite-structured FeF_(2) consisting of closely linked primary nanoparticles using a facile solvothermal method combined with the subsequent annealing treatment.This particular architecture has favorable transport pathways for both lithium ions and electrons and exhibits an ultrafast chargedischarge capability with high reversible capacities.Furthermore,a well-designed LIC employing the prepared dendrite-structured FeF_(2) as the battery-type cathode and commercialized activated carbon(AC)as supercapacitor-type anode was constructed in an organic electrolyte containing Li ions.The LIC operates at an optimal voltage range of 1.1-3.8 V and shows a maximum high energy density of 152 W h kg^(-1) and a high power density of 4900 W kg^(-1) based on the total mass of cathode and anode.Long-term cycling stability(85%capacity retention after 2000 cycles)was achieved at 1 A g^(-1).This work suggests that the dendrite-structured FeF_(2) is a prime candidate for high-performance LICs and accelerates the development of hybrid ion capacitor devices.

Heterogeneous electrolyte membranes enabling double-side stable interfaces for solid lithium batteries

The solid polymer electrolyte(SPE) is one of the most promising candidates for building solid lithium batteries with high energy density and safety due to its advantages of flexibility and light-weight.However,the conventional monolayered electrolytes usually exhibit unstable contacts with either high-voltage cathodes or Li-metal anodes during cell operation.Herein,heterogeneous dual-layered electrolyte membranes(HDEMs) consisting of the specific functional polymer matrixes united with the designed solid ceramic fillers are constructed to address the crucial issues of interfacial instability.The electrolyte layers composed of the high-conductivity and oxidation-resistance polyacrylonitrile(PAN) combined with Li_(0.33)La_(0.557)TiO_(3) nanofibers are in contact with the high-voltage cathodes,achieving the compatible interface between the cathodes and the electrolytes.Meanwhile,the electrolyte layers composed of the highstability and dendrite-resistance polyethylene oxide(PEO) with Li_(6.4)La_(3) Zr_(1.4)Ta_(0.6)O_(12) nanoparticles are in contact with the Li-metal anodes,aiming to suppress the dendrite growth,as well as avoid the passivation between the PAN and the Li-metal.Consequently,the solid LiNi_(0.6)Co_(0.2)Mn_(0.2)O2‖Li full cells based on the designed HDEMs show the good rate and cycling performance,i.e.the discharge capacity of 170.1 mAh g^(-1) with a capacity retention of 78.2% after 100 cycles at 0.1 C and 30℃.The results provide an effective strategy to construct the heterogeneous electrolyte membranes with double-side stable electrode/-electrolyte interfaces for the high-voltage and dendrite-free solid lithium batteries.

In situ Observation of Li Deposition-Induced Cracking in Garnet Solid Electrolytes

Lithium(Li)penetration through solid electrolytes(SEs)induces short circuits in Li solid-state batteries(SSBs),which is a critical issue that hinders the development of high energy density SSBs.While cracking in ceramic SEs has been often shown to accompany Li penetration,the interplay between Li deposition and cracking remains elusive.Here,we constructed a mesoscale SSB inside a focused ion beam-scanning electron microscope(FIB-SEM)for in situ observation of Li deposition-induced cracking in SEs at nanometer resolution.Our results revealed that Li propagated predominantly along transgranular cracks in a garnet Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO).Cracks appeared to initiate from the interior of LLZTO beneath the electrode surface and then propagated by curving toward the LLZTO surface.The resulting bowl-shaped cracks resemble those from hydraulic fracture caused by high fluid pressure on the surface of internal cracks,suggesting that the Li deposition-induced pressure is the major driving force of crack initiation and propagation.The high pressure generated by Li deposition is further supported by in situ observation of the flow of filled Li between the crack flanks,causing crack widening and propagation.This work unveils the dynamic interplay between Li deposition and cracking in SEs and provides insight into the mitigation of Li dendrite penetration in SSBs.

Design of Solid Electrolytes with Fast Ion Transport:Computation-Driven and Practical Approaches

For next-generation all-solid-state metal batteries,the computation can lead to the discovery of new solid electrolytes with increased ionic conductivity and excellent safety.Based on computational predictions,a new proposed solid electrolyte with a flat energy landscape and fast ion migration is synthesized using traditional synthesis methods.Despite the promise of the predicted solid electrolyte candidates,conventional synthetic methods are frequently hampered by extensive optimization procedures and overpriced raw materials.It is impossible to rationally develop novel superionic conductors without a comprehensive understanding of ion migration mechanisms.In this review,we cover ion migration mechanisms and all emerging computational approaches that can be applied to explore ion conduction in inorganic materials.The general illustrations of sulfide and oxide electrolyte structures as well as their fundamental features,including ion migration paths,dimensionalities,defects,and ion occupancies,are systematically discussed.The major challenges to designing the solid electrolyte and their solving strategies are highlighted,such as lattice softness,polarizability,and structural disorder.In addition to an overview of recent findings,we propose a computational and experimental approach for designing high-performance solid electrolytes.This review article will contribute to a practical understanding of ion conduction,designing,rapid optimization,and screening of advanced solid electrolytes in order to eliminate liquid electrolytes.

Evaluation of solid electrolytes: Development of conventional and interdisciplinary approaches

Solid-state lithium batteries(SSLBs)have received considerable attention due to their advantages in thermal stability,energy density,and safety.Solid electrolyte(SE)is a key component in developing high-performance SSLBs.An in-depth understanding of the intrinsic bulk and interfacial properties is imperative to achieve SEs with competitive performance.This review first introduces the traditional electrochemical approaches to evaluating the fundamental parameters of SEs,including the ionic and electronic conductivities,activation barrier,electrochemical stability,and diffusion coefficient.After that,the characterization techniques to evaluate the structural and chemical stability of SEs are reviewed.Further,emerging interdisciplinary visualization techniques for SEs and interfaces are highlighted,including synchrotron X-ray tomography,ultrasonic scanning imaging,time-of-flight secondary-ion mass spectrometry,and three-dimensional stress mapping,which improve the understanding of electrochemical performance and failure mechanisms.In addition,the application of machine learning to accelerate the screening and development of novel SEs is introduced.This review article aims to provide an overview of advanced characterization from a broad physical chemistry view,inspiring innovative and interdisciplinary studies in solid-state batteries.

Revealing the reason for the unsuccessful fabrication of Li_(3)Zr_(2)Si_(2)PO_(12) by solid state reaction

NASICON type Li_(3)Zr_(2)Si_(2)PO_(12)can be synthesized via cation exchange method with Na_(3)Zr_(2)Si_(2)PO_(12)as precursor,which retains the skeleton structure and achieves an ionic conductivity higher than 3 mS cm^(-1)at room temperature.However,large-scale fabrication via cation exchange reaction seems unlikely considering the expensive precursors and complicated preparation process.Herein,the viability of solid-state reaction to prepare Li_(3)Zr_(2)Si_(2)PO_(12)is explored,which has important implication for its industrialization.The sintering was conducted using the raw materials of LiOH,SiO_(2),ZrO_(2)and NH_(4)H_(2)PO_(4)with the nominal stoichiometric ratio of Li_(3)Zr_(2)Si_(2)PO_(12).The results show that the final product is a Li_(3)PO_(4)·2ZrSiO_(4)composite with negligible Li+conductivity,other than the expected Li_(3)Zr_(2)Si_(2)PO_(12)with high Li+conductivity.Combined with thermodynamic calculations based on density functional theory(DFT),the competition between Li_(3)PO_(4)·2ZrSiO_(4)and Li_(3)Zr_(2)Si_(2)PO_(12)with NASICON phase is analyzed.It was found that the formation energy(AG)of Li_(3)PO_(4)·2ZrSiO_(4)is lower than that of Li_(3)Zr_(2)Si_(2)PO_(12).In addition,the decomposition of Li_(3)Zr_(2)Si_(2)PO_(12)with Li_(3)PO_(4)-2ZrSiO_(4)as products is a thermodynamically spontaneous reaction.The influences related to the coordination structures on the structural stability of NZSP are discussed as well.These results demonstrate that the fabrication of Li_(3)Zr_(2)Si_(2)PO_(12)through high-temperature sintering is difficult,and the development of a synthetic method with mild conditions is essential for the Li_(3)Zr_(2)Si_(2)PO_(12)preparation.

Multilayered structure of N-carbonenvelopediron oxide/graphene nanocomposites as an improved anode for Li-ion battery

Transition metal oxides with high capacity are considered a promising electrode material for lithium-ion batteries(LIBs).Nevertheless,the huge volume expansion and poor conductivity severely hamper their practical application.In this work,a carbon riveting method is reported to address the above issues by designing multilayered N-doped carbon(N-carbon) enveloped Fe3O4/graphene nanosheets.When evaluated as a negative electrode,the N-carbon/Fe3O4/graphene nanocomposites demonstrate greatly enhanced electrochemical properties compared with Fe3O4/graphene.The N-carbon/Fe3O4/graphene presents a superior reversible capacity(807 mAh/g) over Fe3O4/graphene(540 mAh/g).Furthermore,it affords a considerable capacity of 550 mAh/g at 1 A/g over 700 cycles,indicating supe rb cycling stability.The structure-property correlation studies reveal that the carbon riveting layer is essential for enhancing the lithium diffusion kinetics.The good electrochemical properties and effective structure design make the carbon riveting strategy quite general and reliable to manipulate high performance electrodes for future LIBs.

Polydopamine-mediated synthesis of Si@carbon@graphene aerogels for enhanced lithium storage with long cycle life

The application of Si as the anode materials for lithium-ion batteries(LIBs) is still severely hindered by the rapid capacity decay due to the structural damage caused by large volume change(> 300%) during cycling. Herein, a three-dimensional(3 D) aerogel anode of Si@carbon@graphene(SCG) is rationally constructed via a polydopamine-assisted strategy. Polydopamine is coated on Si nanoparticles to serve as an interface linker to initiate the assembly of Si and graphene oxide, which plays a crucial role in the successful fabrication of SCG aerogels. After annealing the polydopamine is converted into N-doped carbon(N-carbon) coatings to protect Si materials. The dual protection from N-carbon and graphene aerogels synergistically improves the structural stability and electronic conductivity of Si, thereby leading to the significantly improved lithium storage properties. Electrochemical tests show that the SCG with optimized graphene content delivers a high capacity(712 m Ah/g at 100 m A/g) and robust cycling stability(402 m Ah/g at 1 A/g after 1500 cycles). Furthermore, the full cell using SCG aerogels as anode exhibits a reversible capacity of 187.6 m Ah/g after 80 cycles at 0.1 A/g. This work provides a plausible strategy for developing Si anode in LIBs.

Tungsten oxide thin films for highly sensitive triethylamine detection

Metal oxide semiconductor(MOS)thin films are promising sensing layer for integration in gas sensor devices for detecting toxic and harmful molecules.Herein,tungsten oxide(WO_(3))thin films are deposited on interdigital electrodes by vacuum thermal evaporation to realize batch fabrication of high-performance gas sensors.Subsequent annealing at different temperatures allows for regulation of the concentration of oxygen vacancies in the WO_(3) films,which has been found to exert a great influence on the sensor properties.In addition,the surface structure of WO_(3) films is also highly dependent on the annealing temperature.Gas sensing investigations show that the WO_(3) sensor annealed at 500℃ pos-sesses the best sensing properties for detecting triethylamine(TEA)including very high response,good selectivity,fast response,and low limit of detection(63 ppb).The excellent sensor performances are attributed to the enhanced adsorption of oxidative oxygen species due to the presence of abundant oxygen vacancies.The scalable fabrication of WO_(3) thin film gas sensors and the oxygen vacancy engi-neering strategy proposed herein may shed some light to developing high performance environmental sensors.