Three-dimensional Li-ion transportation in Li_(2)MnO_(3)-integrated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)

Ni-rich layered cathodes(LiNi_xCo_yMn_(2)O_(2))have recently drawn much attention due to their high specific capacities.However,the poor rate capability of LiNi_xCo_yMn_(2)O_(2),which is mainly originated from the twodimensional diffusion of Li ions in the Li slab and Li^(+)/Ni^(2+)cation mixing that hinder the Li^(+)diffusion,has limited their practical application where high power density is needed.Here we integrated Li_(2)MnO_(3)nanodomains into the layered structure of a typical Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)material,which minimized the Li^(+)/Ni^(2+)cationic disordering,and more importantly,established grain boundaries within the NCM811 matrix,thus providing a three-dimensional diffusion channel for Li ions.Accordingly,an average Li-ion diffusion coefficient(D_(Li+))of the Li_(2)MnO_(3)-integrated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811-I)during charge/discharge was calculated to be approximately 6*10^(-10)cm~2 S^(-1),two times of that in the bare NCM811(3*10^(-10)cm~2 S^(-1)).The capacity delivered by the NCM811-I(154.5 mAh g^(-1))was higher than that of NCM811(141.3 mAh g^(-1))at 2 C,and the capacity retention of NCM811-I increased by 13.6%after100 cycles at 0.1 C and 13.4%after 500 cycles at 1 C compared to NCM811.This work provides a valuable routine to improve the rate capability of Ni-rich cathode materials,which may be applied to other oxide cathodes with sluggish Li-ion transportation.

Sourcing the merits of 3D integrated air cathodes for highperformance Zn-air batteries by bubble pump consumption chronoamperometry

Zn-air batteries(ZABs)as a potential energy conversion system suffer from low power density(typically≤200 mW·cm^(−2)).Recently,three-dimensional(3D)integrated air cathodes have demonstrated promising performance over traditional twodimensional(2D)plane ones,which is ascribed to enriched active sites and enhanced diffusion,but without experimental evidence.Herein,we applied a bubble pump consumption chronoamperometry(BPCC)method to quantitatively identify the gas diffusion coefficient(D)and effective catalytic sites density(ρEC)of the integrated air cathodes for ZABs.Furthermore,the D andρEC values can instruct consequent optimization on the growth of Co embedded N-doped carbon nanotubes(CoNCNTs)on carbon fiber paper(CFP)and aerophilicity tuning,giving 4 times D and 1.3 timesρEC over the conventional 2D Pt/C-CFP counterparts.As a result,using the CoNCNTs with half-wave potential of merely 0.78 V vs.RHE(Pt/C:0.89 V vs.RHE),the superaerophilic CoNCNTs-CFP cathode-based ZABs exhibited a superior peak power density of 245 mW·cm^(−2) over traditional 2D Pt/C-CFP counterparts,breaking the threshold of 200 mW·cm^(−2).This work reveals the intrinsic feature of the 3D integrated air cathodes by yielding exact D andρEC values,and demonstrates the feasibility of BPCC method for the optimization of integrated electrodes,bypassing trial-and-error strategy.

Advance in 3D self-supported amorphous nanomaterials for energy storage and conversion

The advancement of next-generation energy technologies calls for rationally designed and fabricated electrode materials that have desirable structures and satisfactory performance.Three-dimensional(3D)self-supported amorphous nanomaterials have attracted great enthusiasm as the cornerstone for building high-performance nanodevices.In particular,tremendous efforts have been devoted to the design,fabrication,and evaluation of self-supported amorphous nanomaterials as electrodes for energy storage and conversion devices in the past decade.However,the electrochemical performance of devices assembled with 3D self-supported amorphous nanomaterials still remains to be dramatically promoted to satisfy the demands for more practical applications.In this review,we aim to outline the achievements made in recent years in the development of 3D self-supported amorphous nanomaterials for a broad range of energy storage and conversion processes.We firstly summarize different synthetic strategies employed to synthesize 3D nanomaterials and to tailor their composition,morphology,and structure.Then,the performance of these 3D self-supported amorphous nanomaterials in their corresponding energy-related reactions is highlighted.Finally,we draw out our comprehensive understanding towards both challenges and prospects of this promising field,where valuable guidance and inspiration will surely facilitate further development of 3D self-supported amorphous nanomaterials,thus enabling more highly efficient energy storage and conversion devices that play a key role in embracing a sustainable energy future.

Fabrication of three-dimensional WO_(3)/ZnWO_(4)/ZnO multiphase heterojunction system with electron storage capability for significantly enhanced photoinduced cathodic protection performance

A novel three-dimensional hierarchical WO_(3)photoelectrode was prepared by solvothermal method,and ZnO was deposited on its surface by electrochemical method.The WO_(3)/ZnWO_(4)/ZnO multiphaseheterojunction photoelectrode was prepared by further annealing treatment to explore the photoinduced cathodic protection(CP)performance.Compared with WO_(3)and ZnO,the photoinduced CP and electron storage capacity performance of WO_(3)/ZnWO_(4)/ZnO is significantly improved in 3.5%NaCl solution without adding any hole scavenger.The electron storage capacity of the WO_(3)/ZnWO_(4)/ZnO heterojunction makes it possible to continuously protect metallic materials in the dark after switching off the light,which can realize long-term and effective photoinduced CP.

Benzoate anions-intercalated NiFe-layered double hydroxide nanosheet array with enhanced stability for electrochemical seawater oxidation

Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy,but detrimental chlorine species(i.e.,chloride and hypochlorite)cause severe corrosion at the anode.Here,we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth(BZ-NiFe-LDH/CC)behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation,affords enlarged interlayer spacing of LDH,inhibits chlorine(electro)chemistry,and alleviates local pH drop of the electrode.It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^(−2)in 1 M KOH.In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis,BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^(−2)in alkaline seawater.Operando Raman spectroscopy studies further identify structural changes of disorderedδ(NiIII-O)during the seawater oxidation process.

Nano-Morphology of a Polymer Electrolyte Fuel Cell Catalyst Layer Imaging, Reconstruction and Analysis

The oxygen reduction reaction （ORR） in the cathode catalyst layer （CCL） of polymer electrolyte fuel cells （PEFC） is one of the major causes of performance loss during operation. In addition, the CCL is the most expensive component due to the use of a Pt catalyst. Apart from the ORR itself, the species transport to and from the reactive sites determines the performance of the PEFC. The effective transport properties of the species in the CCL depend on its nanostructure. Therefore a three-dimensional reconstruction of the CCL is required. A series of two-dimensional images was obtained from focused ion beam- scanning electron microscope （FIB-SEM） imaging and a segmentation method for the two-dimensional images has been developed. The pore size distribution （PSD） was calculated for the three-dimensional geometry. The influence of the alignment and the anisotropic pixel size on the PSD has been investigated. Pores were found in the range between 5 nm and 205 nm. Evaluation of the Knudsen number showed that gas transport in the CCL is governed by the transition flow regime. The liquid water transport can be described within continuum hydrodynamics by including suitable slip flow boundary conditions.