Single-crystal cathode materials for lithium-ion batteries have attracted increasing interest in providing greater capacity retention than their polycrystalline counterparts. However, after being cycled at high voltages, these single-crystal materials exhibit severe structural instability and capacity fade. Understanding how the surface structural changes determine the performance degradation over cycling is crucial, but remains elusive. Here, we investigate the correlation of the surface structure, internal strain, and capacity deterioration by using operando X-ray spectroscopy imaging and nano-tomography. We directly observe a close correlation between surface chemistry and phase distribution from homogeneity to heterogeneity, which induces heterogeneous internal strain within the particle and the resulting structural/performance degradation during cycling. We also discover that surface chemistry can significantly enhance the cyclic performance. Our modified process effectively regulates the performance fade issue of single-crystal cathode and provides new insights for improved design of high-capacity battery materials.

Interfacial issues commonly exist in solid-state batteries, and the microstructural complexity combines with the chemical heterogeneity to govern the local interfacial chemistry. The conventional wisdom suggests that “point-to-point” ion diffusion at the interface determines the ion transport kinetics. Here, we show that solid-solid ion transport kinetics are not only impacted by the physical interfacial contact but are also closely associated with the interior local environments within polycrystalline particles. In spite of the initial discrete interfacial contact, solid-state batteries may still display homogeneous lithium-ion transportation owing to the chemical potential force to achieve an ionic-electronic equilibrium. Nevertheless, once the interior local environment within secondary particle is disrupted upon cycling, it triggers charge distribution from homogeneity to heterogeneity and leads to fast capacity fading. Our work highlights the importance of interior local environment within polycrystalline particles for electrochemical reactions in solid-state batteries and provides crucial insights into underlying mechanism in interfacial transport.

Iodine-doped sulfurized polyacrylonitrile with high conductivity displays an unprecedented capacity for RT-Na/S and RT-K/S batteries operated in ester-based electrolytes.

Solid‐state electrolytes (SSEs) are attracting growing interest for next‐generation Li‐metal batteries with theoretically high energy density, but they currently suffer from safety concerns caused by dendrite growth, hindering their commercial applications. Interfaces between SSEs and solid lithium are argued to be crucial, affecting dendrite growth and determining solid‐state batteries (SSBs) performance. The buried and localized nature of the interface poses a huge challenge for direct characterization under working conditions. Recent review articles have been devoted to evaluating the conductivity and chemical stability of SSEs. Recognizing this, in this Review, the focus is on understanding lithium dendrite beyond conventional factors and offering a perspective on various surface/interface and microstructural phenomena that require close attention by both experimentalists and theoreticians. The complicated ion‐transport mechanism and chemomechanical information correlated with interface and lithium dendrite are discussed. Rational solutions are provided to engineer functional interfaces to suppress lithium dendrites and accelerate progress towards the commercialization of SSBs.

anode because of the sluggish reaction kinetics and high barrier for the formation of OO bond. [6,7] Noble metalbased catalysts such as IrO 2 and RuO 2 exhibit excellent OER activity, but their high cost and non-renewability limit the wide-spread applications. [8][9][10][11] Therefore, it is of great importance to develop costeffective and stable non-noble metalbased electrocatalysts. [12][13][14][15][16][17][18] Metal-organic frameworks (MOFs), with highly dispersed metal sites, intrinsic high porosity, and high internal surface area, have been considered as potential non-noble metal-based catalysts for OER. [19][20][21][22][23] Among the various MOFsbased OER catalysts, Co-based MOFs have received extensive attention due to the high activity and stability. [24,25] More importantly, the structural flexibility of most Co-based MOFs allows the design and fabrication of bimetallic MOFs with different second metal, leading to higher catalytic performance. [26][27][28][29][30][31][32] For example, Li et al. reported that the CoZn bimetallic MOFs could exhibit OER activity with the overpotential of 320 mV at a current density of 10 mA cm −2 due to dimensionality and pore-geometry. [33] Furthermore, Bu et al. reported that the CoNi bimetallic 2D-MOFs exhibited excellent OER activity with the overpotential of 240 mV at 10 mA cm −2 , thanks to the CoNi coupling effect and the unsaturated active sites. [34] However, although plenty of efficient Co MOFs-based bimetallic OER catalysts have been developed, to the best of our knowledge, the effect of different second metal on the OER catalytic performance of Co-based MOFs has not been systematically investigated. What is worse, it is inappropriate to compare the results in reported works directly, because the reported Co-based MOFs may be different in coordination environment, dimension, and amount of second metal.Herein, we introduce different metal (M = Ni, Cu, Zn) into typical Co MOFs (i.e., ZIF-67) and further study their catalytic performance for OER in alkaline media to uncover the secondmetal effect for Co MOFs. These MOFs were grown on conductive carbon cloth (CC) immediately through a one-step roomtemperature strategy (marked as CoM MOFs/CC). [35] The order of OER activity, which is reflected by overpotential and Tafel slope, for these Co-based MOFs is found to be CoZn MOF/CC > CoNi MOF/CC > CoCu MOF/CC > Co MOF/CC. Furthermore, by Co-based bimetallic metal-organic frameworks (MOFs) have emerged as a kind of promising electrocatalyst for oxygen evolution reaction (OER). However, most of present works forCo-based bimetallic MOFs are still in try-and-wrong stage, while the OER performance trend and the underlying structure-function relationship remain unclear. To address this challenge, Cobased MOFs on carbon cloth (CC) (CoM MOFs/CC, M = Zn, Ni, and Cu) are prepared through a room-temperature method, and their structure and OER performance are compared systematically. Based on the results of overpotential and Tafel slope, the order of OER activity is ordered in the de...

Prussian blue analogues (PBAs) have been regarded as prospective cathode materials for sodium-ion batteries due to tunable chemical composition and structure. Herein, a high-performance rhombohedral nickel hexacyanoferrate is synthesized via a controllable low-temperature reaction process. It can deliver impressive capacity retention of 87.8% after 10 000 cycles at 10C and high rate discharge capacity of 53 mAh g–1 at 40C. According to the structural evolution and lattice water movement, superior electrochemical performance is ascribed to small lattice alteration and high reversibility of rhombohedral–cubic transition upon Na+ insertion/extraction. The environment information of local- and long-range structure evolution is revealed by ex situ X-ray absorption spectroscopy (XAS) and in situ X-ray diffraction (XRD). Importantly, lattice water movement during cycling by Fourier transform infrared (FTIR) measurements offers an experimental validation about Na+ nonlinear migration path, as well as the accumulative lattice distortion effect from large-size Na­(OH2)+ unit. The revealed mechanism points out the modified path for PBAs.

A novel low-cost SiO 2 /Polyvinylchloride (PVC) membrane with different nano-SiO 2 particles loading (0-4 wt %) was prepared by the phase-inversion process. The optimum nano-SiO 2 dosage was determined as 1.5 wt % based on the casting solution compositions, the membranes' mechanical properties and hydrophilicities, the pure water fluxes, microstructures, and absorption of protein.Compared with the bare membrane, the membrane with 1.5 wt % nano-SiO 2 addition presented better capabilities against the protein absorption and bacterial attachment, better antifouling performance, and higher flux recovery ratio in filtration of the supernatant liquor which collected from a secondary sedimentation tank in a municipal wastewater plant. The SiO 2 /PVC membranes have applicable potential in the municipal wastewater treatment for their low price, good antifouling performance and high removal efficiencies of SS (over 97.2%), COD (up to 82.9%) and total bacteria (more than 93.6%).

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