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Summary Building phase interface with enough solid-phase contact is of great importance for improving chemical reaction kinetics and depth. High dispersion of electrode materials, especially at the atomic-level, are known for high interface contact, yet their potential application in batteries is restricted due to low loading. Herein, the atomically dispersed metal Ni (Ni in Ni–N–C is 54.9 wt %) with high loading was achieved by ultrahigh N-doping carbon (N/N–C:29.5 wt %) during the discharging process of nickel sulfide, leading to good reversibility and high-capacity maintenance owing to ultrahigh phase contact during long cycling for sodium-ion batteries. It delivers a stable cycling life (0.061% capacity decay per cycle) compared with the poor cyclability (0.418%) for the Ni agglomeration electrode with lower N-doping. The assembled pouch cells achieve robust stability (92.1% after 50 cycles). DFT calculations reveal that ultrahigh N-doping and electrochemically formed Na2S can provide thermally stable Na2S/Ni/NC structures, inhibiting Ni agglomeration during cycling.

Size and crystallinity of building units in the perovskite layer are of great significance to photovoltaic performance. Thus, to fabricate large-grain-size perovskite materials with the advantage of good crystallinity is quite necessary. The oriented attachment strategy has been proofed as an efficient method to control crystal growth. Herein, we reported on oriented attachment of α-CsPbI3 quantum dots (QDs) into a large-grain-size nanocrystal under moderate ultraviolet (UV) light. By virtue of atomic-resolution TEM and X-ray absorption fine structure (XAFS) spectroscopy, we observed the UV-directed structure-evolution and growth process. This is trigged by UV-light illumination (7 W, 365 nm), which drives the oriented assembly of QDs into a large nanoparticle along {110} facets. Moreover, we also visualized a damage process of the α-CsPbI3 QDs to photoinactive-δ-phase ones and finally into PbI2 under high-power UV-light (100 W, 365 nm) exposure. The findings provide a prototype for fabricating large-size perovskite nanostructures with promising properties.

Oxide semiconductors are key materials in many technologies from flat-panel displays，solar cells to transparent electronics. However, many potential applications are hindered by the lack of high mobility p-type oxide semiconductors due to the localized O-2p derived valence band (VB) structure. In this work, the VB structure modulation is reported for perovskite Ba

Enhancing the high voltage cycling stability is critical for reviving LiCoO2-based layered cathodes, and this requires in-depth understanding of various degradation mechanisms and their contributions to performance decay. Herein, we conduct systematic investigations into the failure mechanisms of LiCoO2 upon high voltage cycling and reveal that the capacity loss is mainly due to bulk structure degradation and the voltage fading is mainly due to the blocking effect of the cathode/electrolyte interphase (CEI) layer. Furthermore, as the novel points of our characterization, we find that (i) the LiCoO2 grains are in a highly delithiated state after high voltage cycling, causing poor thermal stability; (ii) the stripe-shaped O1 phase is verified in the grain bulk, demonstrating irreversible structural changes upon high voltage cycling; and (iii) the surface phase transition layer, though it can be as thick as tens of nanometers, plays a minor role in the deterioration of LiCoO2 performance. Our findings stress that bulk structure stability and the blocking effect of the CEI layer are the two major challenges for high voltage usage of LiCoO2-based layered oxides.

High initial coulombic efficiency is highly desired because it implies effective interface construction and few electrolyte consumption, indicating enhanced batteries’ life and power output. In this work, a high-capacity sodium storage material with FeS nanoclusters (≈1–2 nm) embedded in N, S-doped carbon matrix (FeS/N,S-C) was synthesized, the surface of which displays defects-repaired characteristic and detectable dot-matrix distributed Fe-N-C/Fe-S-C bonds. After the initial discharging process, the uniform ultra-thin NaF-rich (≈6.0 nm) solid electrolyte interphase was obtained, thereby achieving verifiable ultra-high initial coulombic efficiency (≈92 %). The defects-repaired surface provides perfect platform, and the catalysis of dot-matrix distributed Fe-N-C/Fe-S-C bonds to the rapid decomposing of NaSOCF and diethylene glycol dimethyl ether successfully accelerate the building of two-dimensional ultra-thin solid electrolyte interphase. DFT calculations further confirmed the catalysis mechanism. As a result, the constructed FeS/N,S-C provides high reversible capacity (749.6 mAh g at 0.1 A g) and outstanding cycle stability (92.7 %, 10 000 cycles, 10.0 A g). Especially, at −15 °C, it also obtains a reversible capacity of 211.7 mAh g at 10.0 A g. Assembled pouch-type cell performs potential application. The insight in this work provides a bright way to interface design for performance improvement in batteries.

Size and crystallinity of building units in the perovskite layer are of great significance to photovoltaic performance. Thus, to fabricate large-grain-size perovskite materials with the advantage of good crystallinity is quite necessary. The oriented attachment strategy has been proofed as an efficient method to control crystal growth. Herein, we reported on oriented attachment of α-CsPbI

p-Si/n-β-Ga2O3:Nb heterojunctions were fabricated by RF magnetron sputtering of β-Ga2O3:Nb layers on the p-Si substrates. The effects of annealing and Nb doping on the properties of heterojunctions were studied. The crystallinity of the β-Ga2O3:Nb film was enhanced by annealing, which also improved the electrical properties of the heterojunctions. The Nb doping greatly affected the I–V characteristics of annealed heterojunctions. The ideality factor was calculated by performing plots from the forward bias I–V characteristics. The charge transport properties of the heterojunction were discussed. The activation energy of β-Ga2O3:Nb films were estimated based on the temperature dependence of resistance.

Thorough understanding of intergranular cracking mechanism is essential and important for developing superior layered cathodes. As a chemomechanical failure, crack's nucleation and evolution are affected mainly by cycling protocols, but it is still lacking direct and accurate observations. Herein, we develop an experimental protocol to visualize the cracking evolution process by tracing the same secondary particles. Further combining large area cross-sectional observations, we identify two distinctive cracking mechanisms due to different state of charge (SOC). At low SOC, chronic fatigue cracking is dominant. At high SOC, particle bursting makes intergranular cracks quickly saturated during the initial cycles, causing battery rapid performance decay in the beginning. We further validate that cracks are nucleated at the end of charging process and it is the discharging that leads to high density of cracks. Managing individual secondary particle below the critical SOC to prevent particle bursting is essential for achieving high cycling stability of Ni-rich layered cathodes.

Interfacial structure evolution and degradation are critical to the electrochemical performance of LiCoO2 (LCO), the most widely studied and used cathode material in lithium ion batteries. To understand such processes requires precise and quantitative measurements. Herein, we use well-defined epitaxial LCO thin films to reveal the interfacial degradation mechanisms. Through our systematical investigations, we find that surface corrosion is significant after forming the surface phase transition layer, and the cathode electrolyte interphase (CEI) has a double layer structure, an inorganic inner layer containing CoO, LiF, LiOH/Li2O and Li x PF y O z , and an outmost layer containing Li2CO3 and organic carbonaceous components. Furthermore, surface cracks are found to be pronounced due to mechanical failures and chemical etching. This work demonstrates a model material to realize the precise measurements of LCO interfacial degradations, which deepens our understanding on the interfacial degradation mechanisms.

Architecting grain crystallographic orientation can modulate charge distribution and chemomechanical properties for enhancing the performance of polycrystalline battery materials. However, probing the interplay between charge distribution, grain crystallographic orientation, and performance remains a daunting challenge. Herein, we elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. While the holistic “surface-to-bulk” charge distribution prevails in polycrystalline particles, the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains. Compared to the randomly oriented grains, the radially aligned grains exhibit a lower cell polarization and higher capacity retention upon battery cycling. The radially aligned grains create less tortuous lithium ion pathways, thus improving the charge homogeneity as statistically quantified from over 20 million nanodomains in polycrystalline particles. This study provides an improved understanding of the charge distribution and chemomechanical properties of polycrystalline battery materials., The authors here report on the influence of grain orientation on the charge distribution in polycrystalline materials for batteries. The quantitative characterization provides mechanistic insight into the way the grain orientation can be engineered to mitigate the charge heterogeneity.

In-depth understanding interfacial failures and differentiating their contributions to the overall performance decay are in urgent need for cell design and optimization. Herein, with the focus on the frequently observed surface phase transition layer (SPTL) of LiCoO2 layered cathode and by virtue of electrochemical tests and microstructure analysis, we systematically investigate the structural and chemical properties of LiCoO2 SPTL under different cycling conditions and reveal that the LiCoO2 SPTL does not contribute performance decay significantly. In comparison with Ni-contained LiNi1-x-yMnxCoyO2 layered cathodes, LiCoO2 SPTL shows two distinctive features. One is the porous morphology due to severe surface corrosion/dissolution and the other is the spinel-like lattice structure. The porous surface layer enables a percolating surface diffusion and the spinel structure offers a bulk diffusion for Li ions, which jointly leads to a minor blocking effect of Li ion during its intercalation/deintercalation. We experimentally verified that the LiCoO2 SPTL is formed in the discharging process, particularly at lower discharge voltages. Our work deepens the understanding on the LiCoO2 SPTL and its effect on the overall performance decay, which sheds new lights on the interfacial failures of layered cathodes.