Decoding lithium batteries through advanced in situ characterization techniques

Given the energy demands of the electromobility market,the energy density and safety of lithium batteries(LBs)need to be improved,whereas its cost needs to be decreased.For the enhanced performance and decreased cost,more suitable electrode and electrolyte materials should be developed based on the improved understanding of the degradation mechanisms and structure–performance correlation in the LB system.Thus,various in situ characterization technologies have been developed during the past decades,providing abundant guidelines on the design of electrode and electrolyte materials.Here we first review the progress of in situ characterization of LBs and emphasize the feature of the multi-model coupling of different characterization techniques.Then,we systematically discuss how in situ characterization technologies reveal the electrochemical processes and fundamental mechanisms of different electrode systems based on representative electrode materials and electrolyte components.Finally,we discuss the current challenges,future opportunities,and possible directions to promote in situ characterization technologies for further improvement of the battery performance.

Editorial for special issue on advanced energy storage and materials for the 70th Anniversary of USTB

1. Foreword Energy storage plays a key role in the transition towards a carbon-neutral economy. By balancing power grids and saving surplus energy, it represents a concrete means of improving energy efficiency and integrating more renewable energy sources into electricity systems. A variety of technologies to store energy are developing at a fast pace and increasingly becomingmoremarketcompetitive,includingtraditional electric energy storage, thermal energy storage, and newly developed hydrogen energy storage, etc. The demand for energy storage system with high power and efficiency boosts the development in the advanced techniques and materials,such as batteries, super-capacitors, molten salts, and catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).

Anchoring nitrogen-doped Co_(2)P nanoflakes on NiCo_(2)O_(4)nanorod arrays over nickel foam as high-performance 3D electrode for alkaline hydrogen evolution

Effective and robust electrocatalysts are mainly based on innovative materials and unique structures.Herein,we designed a flakelike cobalt phosphide-based catalyst supporting on NiCo_(2)O_(4)nanorods array,which in-situ grew on the nickel foam(NF)current collector,referring as NCo_(2)P/NiCo_(2)O_(4)/NF electrode.By optimizing the microstructure and electronic structure through 3D hierarchy fabrication and nitrogen doping,the catalyst features with abundant electrochemical surface area,favorable surface wettability,excellent electron transport,as well as tailored d band center.Consequently,the as-prepared N-Co_(2)P/NiCo_(2)O_(4)/NF electrode exhibits an impressive HER activity with a low overpotentials of58 mV at 10 mA cm^(-2),a Tafel slop of 75 mV dec^(-1),as well as superior durability in alkaline medium.This work may provide a new pathway to effectively improve the hydrogen evolution performance of transition metal phosphides and to develop promising electrodes for practical electrocatalysis.

Constructing BaTiO_(3)/TiO_(2)@polypyrrole composites with hollow multishelled structure for enhanced electromagnetic wave absorbing properties

BaTiO_(3)/TiO_(2)@polypyrrole(PPy)composites with hollow multishelled structure(HoMS)were constructed to enhance the electromagnetic wave absorbing properties of BaTiO_(3)-based absorbing material.BaTiO_(3)/TiO_(2)HoMSs were prepared by hydrothermal crystallization using TiO_(2)Ho MSs as template.Then,FeCl3 was introduced to initiate the oxidative polymerization of pyrrole monomer,forming BaTiO_(3)/TiO_(2)@PPy HoMSs successfully.The electromagnetic wave absorbing properties of BaTiO_(3)/TiO_(2)HoMSs and BaTiO_(3)/TiO_(2)@PPy Ho MSs with different shell number were investigated using a vector network analyzer.The results indicate that BaTiO_(3)/TiO_(2)@PPy HoMSs exhibit improved microwave absorption compared with BaTiO_(3)/TiO_(2)HoMSs.In particular,tripled-shelled BaTiO_(3)/TiO_(2)@PPy HoMS has the most excellent absorbing performance.The best reflection loss can reach up to-21.80 dB at 13.34 GHz with a corresponding absorber thickness of only 1.3 mm,and the qualified absorption bandwidth of tripled-shelled BaTiO_(3)/TiO_(2)@PPy HoMS is up to 4.2 GHz.This work paves a new way for the development of high-performance composite microwave absorbing materials.

中空多壳层结构TiN修饰隔膜对锂硫电池性能的增强

锂硫电池(lithium-sulfur(Li-S)batteries)具有远高于锂离子电池的理论比容量.然而,硫的导电性差,充放电过程中体积变化剧烈,其放电中间产物易溶于电解液并穿过隔膜,造成穿梭效应,导致锂硫电池的实测比容量低、循环寿命短.本文设计构筑了中空多壳层结构氮化钛(TiNHoMS),作为锂硫电池隔膜修饰材料,有效解决了上述难题.氮化钛具有优异的导电性,能够催化硫和多硫化锂的氧化还原转化.HoMS具有多个壳层和多层内部空腔,能提供多重空间阻隔和丰富的多硫化锂吸附位点,从而有效抑制穿梭效应,并且能够缩短电子/离子传输路径.得益于此,采用三壳层TiNHoMS修饰隔膜的锂硫电池性能显著提高,远优于采用未修饰隔膜电池的性能.测试结果表明,在1 C电流下,初始比容量由642 mAh/g提高到1134 mAh/g,而且300次循环后比容量仍保持在792 mAh/g.通过一系列电化学表征分析发现,TiNHoMS提高了隔膜对电解液的浸润性,催化了硫正极的氧化还原反应,抑制了多硫化锂的穿梭效应,从而有效地提高了锂硫电池的比容量和循环稳定性.

Nickel-iron in the second coordination shell boost single-atomicsite iridium catalysts for high-performance urea electrooxidation

Single-atom catalysts(SACs)with high catalytic activity as well as great stability are demonstrating great promotion in electrocatalytic energy conversion,which is also a big challenge to achieve.Herein,we proposed a facile synthetic strategy to construct nickel-iron bimetallic hydroxide nanoribbon stabilized single-atom iridium catalysts(Ir-NiFe-OH),where the nickel-iron hydroxide nanoribbon not only can serve as good electronic conductor,but also can well stabilize and fully expose single-atom sites.Adopted as catalyst for urea oxidation reaction(UOR),it exhibited excellent UOR performance that it only needed a low operated potential of 1.38 V to achieve the current density of 100 mA·cm^(-2).In-situ Fourier transform infrared spectroscopy,X-ray absorption spectrum,and density functional theory calculations proved that Ir species are active centers and the existence of both Ni and Fe in the local structure of Ir atom can optimize the d-band center of Ir species,promoting the adsorption of intermediates and desorption of products for UOR.The hydrogen evolution reaction(HER)/UOR electrocatalytic cell demanded voltages of 1.46 and 1.50 V to achieve 50 and 100 mA·cm^(-2),respectively,which demonstrated a higher activity and better stability than those of conventional catalysts.This work opens a new avenue to develop catalysts for UORs with boosted activity and stability.

碳基柔性电极的结构设计、制备和组装

柔性电子器件日益流行,给人们的日常生活带来了巨大的变革,同时也激发了柔性储能器件的设计和研制,其中,柔性锂离子电池引起了广泛的关注.为了获得柔性储能器件,首先需要制备柔性电极,即要求在反复变形状态下,电极能够保持优异的力学和电学性能.碳材料具有优异的力学性能和导电性,不仅能够直接制备柔性电极,还能够与活性材料复合,作为基底提供自支撑的导电网络.但是"刚性"的活性材料与"柔性"基底从力学和形态本质上均不匹配,二者的复合、组装、制备方法及其结合强度直接影响电池的电化学性能.本文综述了近年来碳纳米管、碳纳米线、石墨烯、石墨炔及碳布等碳基柔性电极的发展情况,着重分析了自支撑柔性电极的制备方法、结构特征与电化学性能的关系,同时简要总结了目前几种典型结构的柔性锂离子电池,探讨了碳材料柔性电极面临的挑战,并对其未来发展方向进行了展望.

Bismuth oxychloride hollow microspheres with high visible light photocatalytic activity

Hollow microspheres of two bismuth oxychlorides, BiOC1 and Bi24031Cl10, were successfully synthesized using carbonaceous microsphere sacrificial templates. The phase evolution from BiOC1 to Bi24031Cl10 was easily realized by heating the former at 600 ℃. With a uniform diameter of about 200 nm, an average shell thickness of 40 nm, and basic nanosheets of 〈20 nm, the hollow microspheres of both BLOC1 and Bi24031Cl10 showed high visible light photocatalytic activity towards the degradation of Rhodamine B （RhB）. Besides the effective photo- sensitization process and efficient photointroduced carrier separation, the high photocatalytic activity was believed to result from their hollow-structure- dependent large visible light absorption. Moreover, as a chlorine-deficient analogue, the Bi24031Cl10 hollow spheres possessed a narrower band gap, more dispersive band structure, and higher photocarrier conversion efficiency, which further helped them to exhibit better photocatalytic activity.

Highly active CeO_2 hollow-shell spheres with Al doping

Metal oxide hollow structures are of great inter- est in many current and emerging areas of technology. This paper presents a facile and controlled protocol for the syn- thesis of Al-doped CeO2 hollow-shell spheres （CHS）, where the dopant confers enhanced stability and activity to the ma- terial. These Al-doped CeO2 hollow-shell spheres （ACHS） possess a controllable shell number of up to three, where the sizes of the exterior, middle, and interior spheres were about 250-100 nm,150-50 nm, and 40-10 nm, respectively, and the average shell thickness was -15 nm. The thermal stability of the ACHS structure was enhanced by the homogeneous in- corporation of AI atoms, and more active oxygen species were present compared with those in the non-doped congener. Au NPs supported on ACHS （Au/ACHS） showed superior cat- alytic performance for the reduction of p-nitrophenol. For the same Au NP content, the reaction rate constant （k） of the Au/ACHS was nearly twice that of the non-doped Au/CHS, indicating that AI doping is promising for improving the per- formance of inert or unstable oxides as catalyst supports.

Cobalt hollow nanospheres： controlled synthesis, modification and highly catalytic performance for hydrolysis of ammonia borane

Size tunable cobalt hollow nanospheres with high catalytic activity for the ammonia borane(AB) hydrolysis have been synthesized by using the solvothermal method. The complexation between Co2+and ethylenediamine is observed to be critical for the formation of the cobalt hollow nanospherical structure.The morphology of the cobalt hollow nanospheres can be regulated by adjusting the original ethylenediamine/ethanol volume ratio, reaction time and temperature. Impressively, the magnetic property study reveals that the coercivity of the as-synthesized cobalt hollow nanospheres is much enhanced compared with that of bulk cobalt materials. Meanwhile, Co/Pt bimetal hollow nanospheres(Co Pt HS) and graphene-cobalt hollow composite nanospheres(Co HS-r GO) have also been explored. In comparison with the cobalt hollow nanospheres, both the Co Pt HS and Co HS-r GO show higher catalytic activities and better repeatability for the catalytic hydrogen generation from AB hydrolysis. Moreover, it is noted that these catalysts could be recycled by using the magnetic separation method.

Hollow multishelled structural TiN as multi-functional catalytic host for high-performance lithium-sulfur batteries

Lithium-sulfur(Li-S)battery has attracted extensive attention because of its ultrahigh theoretical energy density and low cost.However,its commercialization is seriously hampered by its short cycling life,mainly due to the shuttle of soluble lithium polysulfides(LiPSs)and poor rate capability due to sluggish reaction kinetics.Although significant efforts have been devoted to solving the problems,it is still challenging to simultaneously address all the issues.Herein,titanium nitride hollow multishelled structure(TiN HoMS)sphere is designed as a multi-functional catalytic host for sulfur cathode.TiN,with good conductivity,can effectively catalyze the redox conversion of S and LiPSs,while its surficial oxidation passivation layer can strongly anchor LiPSs.Besides,HoMS enables TiN nanoparticle subunits to expose abundant active sites for anchoring and promoting conversion of LiPSs,while the multiple shells provide physical barriers to restrict the shuttle effect.In addition,HoMS can buffer the volume expansion of sulfur and shorten the charge transport pathway.As a result,the sulfur cathode based on triple-shelled TiN HoMS exhibits an initial specific capacity of 1016 mAh·g-1 at a high sulfur loading of 2.8 mg·cm-2 and maintains 823 mAh·g-1 after 100 cycles.Moreover,it shows a four times higher specific capacity than the one without TiN host at 2 C.

Multishelled CuO/Cu_(2)O induced fast photo-vapour generation for drinking water

Solar thermal interfacial water evaporation is proposed as a promising route to address freshwater scarcity,which can reduce energy consumption and have unlimited application scenarios.The large semiconductor family with controllable bandgap and good chemo-physical stability are considered as good candidates for photo-evaporation.However,the evaporation rate is not satisfactory because the rational control of nano/micro structure and composition is still in its infancy stage.Herein,by systemically analyzing the photo-thermal evaporation processes,we applied the hollow multishelled structure(HoMS)into this application.Benefiting from the multishelled and hierarchical porous structure,the light absorption,thermal regulation,and water transport are simultaneously optimized,resulting in a water evaporation rate of 3.2 kg·m^(-2)·h^(-1),which is among the best performance in solar-vapour generation.The collected water from different water resources meets the World Health Organization standard for drinkable water.Interestingly,by using the CuO/Cu_(2)O system,reactive oxygen species were generated for water disinfection,showing a new route for efficient solar-vapour generation and a green way to obtain safe drinking water.

Engineering single atomic ruthenium on defective nickel vanadium layered double hydroxide for highly efficient hydrogen evolution

Fabricating single-atom catalysts(SACs)with high catalytic activity as well as great stability is a big challenge.Herein,we propose a precise synthesis strategy to stabilize single atomic ruthenium through regulating vanadium defects of nickel vanadium layered double hydroxides(NiV-LDH)ultrathin nanoribbons support.Correspondingly,the isolated atomically Ru doped NiV-LDH ultrathin nanoribbons(NiVRu-R)were successfully fabricated with a super-high Ru load of 12.8 wt.%.X-ray absorption spectrum(XAS)characterization further confirmed atomic dispersion of Ru.As catalysts for electrocatalytic hydrogen evolution reaction(HER)in alkaline media,the NiVRu-R demonstrated superior catalytic properties to the commercial Pt/C.Moreover,it maintained exceptional stability even after 5,000 cyclic voltammetry cycles.In-situ XAS and density functional theory(DFT)calculations prove that the Ru atomic sites are stabilized on supports through forming the Ru-O-V structure,which also help promote the catalytic properties through reducing the energy barrier on atomic Ru catalytic sites.