We report an electrochemical CO2 reduction reaction catalyzed by a paramagnetic and conductive CuO/Cu interface with spins polarized by a moderate external magnetic field (MF) of ∼800 gauss, achieving a ∼30% increase in CO2-to-C2+ Faradaic efficiency (FE) compared to that in the absence of the MF in a flow cell electrolyzer. At a current density of 400 mA/cm2, the CO2-to-C2+ FE reached 86.7 ± 2.7% with 47.9 ± 1.4% cathodic energy efficiency (EE) in contrast to the CO2-to-C2+ FE of 67.6% with 36.4% of EE in the absence of MF. Notably, ethanol production exhibits a much higher response to the MF (∼55.6% increase in FE) than ethylene (∼6.4% increase in FE) at 400 mA/cm2. In situ surface-enhanced Raman spectroscopy (SERS) captured magnetic-field-enhanced *CO coverage and ethanol-forming C2 intermediates on CuO/Cu, providing direct spectroscopic evidence of spin-modulated pathway selection. Computational study suggests that the enhancement of ethanol selectivity is due to the reduced reaction kinetic barrier under MF, while the ethylene selectivity is less affected, mainly due to the insensitivity of the kinetic barriers under MF.

Crystallographic texture is common in polycrystalline materials and has an important influence on the physicochemical performance of the materials. In this work, using the electron backscatter diffraction technique, the orientation distribution map of individual battery cathode particles was plotted. Through a combination of multiscale characterization approaches, the morphology, structure, chemical composition, and orientation information within individual secondary particles can be captured simultaneously. The pristine secondary particles have a pronounced out-of-plane texture, which results in the inhomogeneity of strain within the particles. Such inhomogeneous strain is associated with the crack formation and growth of secondary particles during delithiation, which further influence their electrochemical–mechanical behaviors. These findings elucidate the underlying texture evolution within polycrystal cathode particles and shed light on the mechanism of performance degradation.

The degradation of Ni-rich cathodes during long-term operation at high voltage has garnered significant attention from both academia and industry. Despite many post-mortem qualitative structural analyses, precise quantification of their individual and coupling contributions to the overall capacity degradation remains challenging. Here, by leveraging multiscale synchrotron X-ray probes, electron microscopy, and post-galvanostatic intermittent titration technique, the thermodynamically irreversible and kinetically reversible capacity loss is successfully deconvoluted in a polycrystalline LiNi0.83Mn0.1Co0.07O2 cathode during long-term charge/discharge cycling in full cell configuration. Contradicting the dramatic capacity loss, the layered structure remains highly alive even after 1000 cycles at 4.6 V while undergoing a three-order of magnitude reduction in the mass transfer kinetics, leading to almost fully recoverable capacity under kinetic-free conditions. Such kinetic dormant behavior after cycling is not simply ascribed to poor chemical diffusion by reconstructed cathode surface but highly synchronizes with the lattice strain evolution stemming from the structural heterogeneity between deeply delithiated layered and degraded rock-salt phases at high voltage. These findings deepen the degradation mechanism of high-voltage cathodes to achieve long-cycling and fast-charging performance.

Intercalation-type layered oxides are the most promising positive electrodes for next-generation sodium-ion batteries due to their high energy density, low cost, and tunable chemistry. However, these materials are often subjected to substantial phase transitions and lattice changes when cycled at high voltage, leading to fast capacity decay. In this work, we demonstrate a strategically performed low-temperature heat treatment of the desodiated electrode for mitigating the pernicious structural changes in layered P2-type Na2/3Ni1/3Mn2/3O2 electrode. An intergrowth framework forms and consists of a primary layered structure and secondary disordered rock-salt-like nano domains. This intergrowth structure manifests significant enhancement in cycling stability with negligible electro-chemo-mechanical changes due to small lattice variation. Our study demonstrates an effective approach for performance improvements through a straightforward heat treatment and provides insights into the ability to nanoengineering and interface engineering in intergrowth structures.

Surface reconstruction and the associated severe strain propagation have long been reported as the major cause of cathode failure during fast charging and long-term cycling. Despite tremendous attempts, no known strategies can simultaneously address the electro-chemomechanical instability without sacrificing energy and power density. Here we report an epitaxial entropy-assisted coating strategy for ultrahigh-Ni LiNixCoyMn1-x-yO2 (x >= 0.9) cathodes via an oriented attachment-driven reaction between Wadsley-Roth phase-based oxides and the layered-oxide cathodes. The high anti-cracking and anti-corrosion tolerances as well as the fast ionic transport of the entropy-assisted surface effectively improved the fast charging/discharging capability, wide temperature tolerance and thermal stability of the ultrahigh-Ni cathodes. Comprehensive analysis from the primary and secondary particle level to the electrode level using multi-scale in situ synchrotron X-ray probes reveals greatly reduced lattice dislocations, anisotropic lattice strain and oxygen release as well as improved bulk/local structural stability, even when charging beyond the threshold state of charge (75%) of layered cathodes. Layered Ni-rich oxide cathodes are susceptible to challenges with surface reconstruction and strain propagation, limiting their cyclability. The authors propose a solution involving oriented attachment-driven reactions, utilizing Wadsley-Roth nanocrystals and layered oxide to induce an epitaxial entropy-assisted coating, effectively addressing these issues.

This study investigates the electrochemical behavior of molybdenum disulfide (MoS2) as an anode in Li-ion batteries, focusing on the extra capacity phenomenon. Employing advanced characterization methods such as in situ and ex situ X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, the research unravels the complex structural and chemical evolution of MoS2 throughout its cycling. A key discovery is the identification of a unique Li intercalation mechanism in MoS2, leading to the formation of reversible LixMoS2 phases that contribute to the extra capacity of the MoS2 electrode. Density function theory calculations suggest the potential for overlithiation in MoS2, predicting Li5MoS2 as the most energetically favorable phase within the lithiation-delithiation process. Additionally, the formation of a Li-rich phase on the surface of Li4MoS2 is considered energetically advantageous. After the first discharge, the battery system engages in two main reactions. One involves operation as a Li-sulfur battery within the carbonate electrolyte, and the other is the reversible intercalation and deintercalation of Li in LixMoS2. The latter reaction contributes to the extra capacity of the battery. The incorporation of reduced graphene oxide as a conductive additive in MoS2 electrodes notably improves their rate capability and cycling stability.

The demands for sustainable energy systems underscores the importance in developing sodium-ion batteries (NIBs) with earth abundant raw materials, enhanced energy density, prolonged lifespan, and reduced cost. Among potential candidates for such advancements, intercalation-type layered transition metal oxide (LTMO) positive electrode materials are attractive due to their notable high theoretical specific capacity and tunable chemistry. However, LTMO electrodes are often subjected to anisotropic changes during cycling. Repeated anisotropic changes cause host structure strain, eventually leading to material degradation. Regulating the electrostatic interactions is generally perceived to be a viable approach for structure stabilization in layered oxides during cycling, but conventional synthesis approaches have been unable to tame the effect. Here, we demonstrate negligible anisotropic changes in layered P2-type Na0.67Ni0.33Mn0.67O2 through regulation of electrostatic repulsion realized by modulation of transition metal ions occupancy. The electrode exhibits a capacity retention of 83.3% in 100 cycles between 2 - 4.3 V, which is significantly better than the 36.9% retention of the pristine sample. Our study emphasizes the highly correlated nature of the redox mechanism that deserves the attention and is critical for high-energy batteries.

High energy-density Ni-rich layered cathodes suffer a long-standing challenge of severe performance deterioration at high potentials. Besides, it is of great challenge to develop a universal mitigation strategy to address numerous deterioration causes. Herein, to probe the dominant deterioration root for guiding rational development, we perform an in-depth investigation of LiNi 0.83 Mn 0.1 Co 0.07 O 2 in full cells with graphite anode for 1000 cycles at different state-of-charges. Intriguingly, severe capacity retention of harvest cathodes (like 54% at 4.6 V) is inconsistent with insignificant material degradation via synchrotron-based X-ray characterizations. To unpuzzle this, we deconvolute the overall performance deterioration of cycled cathode into irreversible and reversible losses. Our evaluation unveils Ni-rich cathodes are mostly alive (like 88% at 4.6 V) but kinetically inhibited in long-term cycling at high potentials. The evolution of Li + diffusion is of greater significance than that of electrical impedance. The exacerbated cathode-electrolyte interface, mainly rock-salt phase, is speculated experimentally and analytically as the predominant root for severe chemical diffusion and performance deterioration. Our findings highlight the upmost importance of stabilizing the cathode-electrolyte interface for deploying Ni-rich cathodes at higher potentials to awaken more energy and longer lifespan.

Increasing the energy density of lithium-ion batteries, and thereby reducing costs, is a major target for industry and academic research. One of the best opportunities is to replace the traditional graphite anode with a high-capacity anode material, such as silicon. However, Si-based lithium-ion batteries have been widely reported to suffer from a limited calendar life for automobile applications. Heretofore, there lacks a fundamental understanding of calendar aging for rationally developing mitigation strategies. Both open-circuit voltage and voltage-hold aging protocols were utilized to characterize the aging behavior of Si-based cells. Particularly, a high-precision leakage current measurement was applied to quantitatively measure the rate of parasitic reactions at the electrode/electrolyte interface. The rate of parasitic reactions at the Si anode was found 5 times and 15 times faster than those of LiNi0.8Mn0.1Co0.1O2 and LiFePO4 cathodes, respectively. The imbalanced charge loss from parasitic reactions plays a critical role in exacerbating performance deterioration. In addition, a linear relationship between capacity loss and charge consumption from parasitic reactions provides fundamental support to assess calendar life through voltage-hold tests. These new findings imply that longer calendar life can be achieved by suppressing parasitic reactions at the Si anode to balance charge consumption during calendar aging.

Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energy-density lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li2CO3 impurity content on LiNi0.83Mn0.1Co0.07O2 cathodes using air, tank-air, and O2 synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li2CO3 impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li2CO3 content and severe performance deterioration of Ni83 cathodes. The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Ni-rich cathodes and prepares us for searching for rational strategies.

Microsized Sn is a promising anode material for sodium-ion batteries in terms of cost, specific capacity, and volumetric energy density, which however suffers from huge volume changes and rapid cell degradation upon cycling. Despite recent advances via nanostructured electrode design and interface engineering, the correlation between mechanical stability, solid-electrolyte interphase (SEI) and reaction kinetics/reversibility remains controversial and elusive. Here, by combining in situ scanning electron microcopy and X-ray absorption spectroscopy as well as X-ray photoelectron spectroscopy, we have investigated the underlying electro-chemomechanical behavior and their coupling effects during charge/discharge of microsized Sn anode. Our results revealed that microsized Sn is pulverized into nanoparticles with simultaneous formation of numerous voids and pores upon the 1st charge/discharge, while the electrolytes composition plays a critical role on the consequent parasitic reactions and eventually the sodiation/de-sodiation reversibility. In contrast to carbonate-based electrolytes, ether-based electrolytes enabled formation of inorganic species dominated SEI with improved mechanical strength, thus leading to higher specific capacity and improved cycling stability. The present findings are crucial for future development of microsized anode materials for rechargeable batteries with high volumetric energy density.

The mesoporous silica shell coating hydrogenolysis nano-catalysts alters the molecular weight distributions of cleaved polymer chains compared to catalysts without a shell. The shell, composed of radially aligned narrow cylindrical nanopores, reduces the formation of low-valued gaseous products and increases the median molecular weight of the product, thus enhancing the value of the products for polymer upcycling. To understand the role of the mesoporous shell, we have studied the spatial distribution of polystyrene chains, used as a model polymer, in the nanochannels in both the melt phase and solution phase. In the melt, we observed from small-angle X-ray scattering experiments that the infiltration rate of the polymer into the nanochannels is inversely proportional to the molecular weight, which is consistent with theory. In theta solution experiments using UV-vis spectroscopy, we found that the shell significantly enhances polymer adsorption compared to nanoparticles without pores. In addition, the degree of polymer adsorption is not a monotonic function of molecular weight but initially increases with the molecular weight before eventually decreasing. The molecular weight for the peak adsorption increases with the pore diameter. This adsorption behavior is rationalized as resulting from a balance between the mixing entropy gain by surface adsorption and the conformational entropy penalty incurred by chains confined in the nanochannels. The spatial distribution of polymer chains in the nanochannels is visualized by energy-dispersive X-ray spectroscopy (EDX), and inverse Abel-transformed data reveals a less uniform polymer distribution along the primary pore axis for longer chains.

Group IV elements and their oxides, such as Si, Ge, Sn and SiO have much higher theoretical capacity than commercial graphite anode. However, these materials undergo large volume change during cycling, resulting in severe structural degradation and capacity fading. Al2O3 coating is considered an approach to improve the mechanical stability of high-capacity anode materials. To understand the effect of Al2O3 coating directly, we monitored the morphology change of coated/uncoated Sn particles during cycling using operando focused ion beam-scanning electron microscopy. The results indicate that the Al2O3 coating provides local protection and reduces crack formation at the early stage of volume expansion. The 3 nm Al2O3 coating layer provides better protection than the 10 and 30 nm coating layer. Nevertheless, the Al2O3 coating is unable to prevent the pulverization at the later stage of cycling because of large volume expansion.

MoO 2 nanoparticle anodes show increased capacity beyond the expected value derived from the conversion reaction due to the formation of a Li-rich layer and morphological changes that affect capacity during cycling.

High-voltage operation is essential for the energy and power densities of battery cathode materials, but its stabilization remains a universal challenge. To date, the degradation origin has been mostly attributed to cycling-initiated structural deformation while the effect of native crystallographic defects induced during the sophisticated synthesis process has been significantly overlooked. Here, using in situ synchrotron X-ray probes and advanced transmission electron microscopy to probe the solid-state synthesis and charge/discharge process of sodium layered oxide cathodes, we reveal that quenching-induced native lattice strain plays an overwhelming role in the catastrophic capacity degradation of sodium layered cathodes, which runs counter to conventional perception-phase transition and cathode interfacial reactions. We observe that the spontaneous relaxation of native lattice strain is responsible for the structural earthquake (e.g., dislocation, stacking faults and fragmentation) of sodium layered cathodes during cycling, which is unexpectedly not regulated by the voltage window but is strongly coupled with charge/discharge temperature and rate. Our findings resolve the controversial understanding on the degradation origin of cathode materials and highlight the importance of eliminating intrinsic crystallographic defects to guarantee superior cycling stability at high voltages.

Oxygen redox at high voltage has emerged as a transformative paradigm for high-energy battery cathodes such as layered transition-metal oxides by offering extra capacity beyond conventional transition-metal redox. However, these cathodes suffer from voltage hysteresis, voltage fade and capacity drop upon cycling. Single-crystalline cathodes have recently shown some improvements, but these challenges remain. Here we reveal the fundamental origin of oxygen redox instability to be from the domain boundaries that are present in single-crystalline cathode particles. By investigating single-crystalline cathodes with different domain boundaries structures, we show that the elimination of domain boundaries enhances the reversible lattice oxygen redox while inhibiting the irreversible oxygen release. This leads to significantly suppressed structural degradation and improved mechanical integrity during battery cycling and abuse heating. The robust oxygen redox enabled through domain boundary control provides practical opportunities towards high-energy, long-cycling, safe batteries. Oxygen redox instability at high voltages hinders the application of high-energy battery cathodes. Here the authors report that elimination of domain boundaries in single-crystal cathodes improves the redox stability and consequently the electrochemical performance in extended high-voltage cycling.

The commercialization of nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) has been hindered by its continuous loss of practical capacity and reduction in average working voltage. To address these issues, surface modification has been well-recognized as an effective strategy. Different from the coatings reported in literature to date, in this work, we for the first time report a sulfide coating, amorphous Li2S via atomic layer deposition (ALD). Our study revealed that the conformal nano-Li2S coating shows exceptional protection over the NMC811 cathodes, accounting for the dramatically boosted capacity retention from similar to 11.6% to similar to 71% and the evidently mitigated voltage reduction from 0.39 to 0.18 V after 500 charge-discharge cycles. In addition, the Li2S coating remarkably improved the rate capability of the NMC811 cathode. Our investigation further revealed that all these beneficial effects of the ALD-deposited nano-Li2S coating lie in the following aspects: (i) maintain the mechanical integrity of the NMC811 electrode; (ii) stabilize the NMC electrode/electrolyte interface; and (iii) suppress the irreversible phase transition of NMC structure. Particularly, this study also has revealed that the nano-Li2S coating has played some unique role not associated with traditional non-sulfide coatings such as oxides. In this regard, we disclosed that the Li2S layer has reacted with the released O-2 from the NMC lattices, and thereby has dramatically mitigated electrolyte oxidation and electrode corrosion. Thus, this study is significant and has demonstrated that sulfides may be an important class of coating materials to tackle the issues of NMCs and other layered cathodes in lithium batteries. (C) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

The primary research on anode materials of lithium-ion batteries have been focused on increasing the specific capacity, while the working potential that is also closely related to the practical energy density of batteries has been paid much less attention. In this work, starting from micrometer-sized silicon and black phosphorus, we have reported a high-energy silicon-phosphorus/carbon anode (denoted as mSPC) via a high-energy ball milling process, which demonstrates an average discharge working potential of 0.3 V versus lithium, together with a high reversible capacity of > 2000 mAh/g, high initial coulombic efficiency of 84%, excellent cycle stability, and superior rate capability up to 15 A/g. Furthermore, in situ focused-ion-beam scanning electron microscopy reveals that the volume change of the mSPC anode during repeated (de) lithiation is effectively alleviated. In contrast, starting from nanometer-sized silicon, the resulted anode (denoted as nSPC) not only presents a lower reversible capacity (~ 1200 mAh/g), but also exhibits a higher charge/discharge working potential, leading to reduced energy density. Our results indicate the importance of composition/structure control in tailoring the working potential and specific capacity of alloying-type anodes towards high-energy lithium-ion batteries. The interaction of silicon and phosphorus could tune the working potential and specific capacity of anode materials for lithium-ion batteries, leading to significantly improved energy density and power density.