Search

LiCl is a promising solid electrolyte, providing it possesses high ionic conductivity. Numerous efforts have been made to enhance its ionic conductivity through aliovalent doping. However, aliovalent substitution changes the intrinsic structure of LiCl, compromising its cost-effectiveness and electrochemical stability. Here, we report nanocrystalline LiCl embedded in amorphous AlOCl compounds with a heterogeneous structure to enhance its ionic conductivity. Nanocrystallization enlarges the LiCl unit cell, while amorphization facilitates interfacial ion transport. As a result, the amorphous AlOCl-modified LiCl nanocrystal (AlOCl-nanoLiCl) demonstrates a high ionic conductivity of 1.02 mS cm–1, which is 5 orders of magnitude higher than that of LiCl. Additionally, it exhibits high oxidative stability, low cost ($19.87 US kg–1), and low Young’s modulus (2–3 GPa). When AlOCl-nanoLiCl is coupled with Li-rich cathodes (Li1.17Mn0.55Ni0.24Co0.05O2, 4.8 V vs Li+/Li), all-solid-state batteries exhibit remarkable long-term cycling stability (>1000 cycles). This work presents a novel strategy to enhance the ionic conductivity of alkaline chlorides without compromising their intrinsic advantages.

Lithium (Li) metal solid-state batteries feature high energy density and improved safety and thus are recognized as promising alternatives to traditional Li-ion batteries. In practice, using Li metal anodes remains challenging because of the lack of a superionic solid electrolyte that has good stability against reduction decomposition at the anode side. Here, we propose a new electrolyte design with an antistructure (compared to conventional inorganic structures) to achieve intrinsic thermodynamic stability with a Li metal anode. Li-rich antifluorite solid electrolytes are designed and synthesized, which give a high ionic conductivity of 2.1 × 10–4S cm–1at room temperature with three-dimensional fast Li-ion transport pathways and demonstrate high stability in Li–Li symmetric batteries. Reversible full cells with a Li metal anode and LiCoO2cathode are also presented, showing the potential of Li-rich antifluorites as Li metal-compatible solid electrolytes for high-energy-density solid-state batteries.

All-solid-state batteries (ASSBs) have garnered significant interest due to their exceptional safety features and high theoretical energy density. Despite extensive research demonstrating the impressive electrochemical performance of ASSBs at moderate and high temperatures, their electrochemical performance significantly degrades in a cold environment, with the underlying mechanism yet to be disclosed. In this review, we examine the ion transport kinetics of ASSBs and emphasize the challenges they face at low temperatures. By examining microscopic kinetic processes, including Li-ion migration within solid electrolytes (SEs), interfacial charge transfer, and bulk electrode diffusion, we outline the critical challenges and specific requirements on SEs, interfaces, and electrodes for low-temperature ASSBs. Based on these insights, a range of materials and chemistry design strategies for high-performance ASSBs at low temperatures are reviewed. Finally, future research directions for improving low-temperature ASSB performance are proposed. This study aims to offer a thorough understanding and crucial insights to improve the low-temperature performance of ASSBs.

Designing Na-ion solid electrolytes (SEs) of high ionic conductivity and excellent chemical/mechanical compatibility with cathode materials remains challenging for all-solid-state Na-ion batteries (ASSNIBs). In this study, we successfully design and synthesize a novel amorphous NaTaCl6halide SE with unprecedented ionic conductivity of 4 × 10−3S cm−1at room temperature. The exceptional ionic conductivity arises from a unique reconstructed amorphous poly-(TaCl6) octahedra network with weakening Na-Cl interactions through high-energy mechanochemical reactions. Notably, the amorphous NaTaCl6halide SE exhibits remarkable mechanical deformability, chemical/electrochemical stability, and outstanding electrochemical performance when coupled with the Na3V2(PO4)3cathode in ASSNIBs, resulting in a remarkable initial Coulombic efficiency of 99.60%, excellent rate performance (85% capacity retention at 2 C), and stable long-cycling profiles (81%/95%/98% capacity retention after 4,000/600/1,500 cycles at 3/1/0.5 C). This discovery of superionic amorphous Na-ion halide SEs opens a promising avenue for advancing high-performance ASSNIBs.

The sodium (Na) superionic conductor is a key component that could revolutionize the energy density and safety of conventional Na-ion batteries. However, existing Na superionic conductors are primarily based on a single-anion framework, each presenting inherent advantages and disadvantages. Here we introduce a family of amorphous Na-ion conductors (Na2O2–MCly, M = Hf, Zr and Ta) based on the dual-anion framework of oxychloride. Benefiting from a dual-anion chemistry and with the resulting distinctive structures, Na2O2–MClyelectrolytes exhibit room-temperature ionic conductivities up to 2.0 mS cm−1, wide electrochemical stability windows and desirable mechanical properties. All-solid-state Na-ion batteries incorporating amorphous Na2O2–HfCl4electrolyte and a Na0.85Mn0.5Ni0.4Fe0.1O2cathode exhibit a superior rate capability and long-term cycle stability, with 78% capacity retention after 700 cycles under 0.2 C (1C = 120 mA g−1) at room temperature. The discoveries in this work could trigger a new wave of enthusiasm for exploring new superionic conductors beyond those based on a single-anion framework.

Graphic Abstract:

Sulfur-based cathode materials have become a research hot spot as one of the most promising candidates for next-generation, high-energy lithium batteries. However, the insulating nature of elemental sulfur or organosulfides has become the biggest challenge that leads to dramatic degradation and hinders their practical application. The disadvantage is more obvious for all-solid-state battery systems, which require both high electronic and ionic migration at the same sites to realize a complete electrochemical reaction. In addition to adding conductive components into the cathode composites, another effective way to realize high-reversibility sulfur-based cathodes is by optimizing the inherent nature of sulfur-based materials to make them “conductive”. Inorganic polysulfide materials including polysulfide molecules, selenium-sulfur solid solutions, and (lithium) metal polysulfides are promising, as they have different structures that can make them intrinsically conductive or becoming conductive during lithiation. They all contain at least one −S–S– bridged bond, which is the intrinsic structural characteristic and the source of the chemical properties of these polysulfide compounds. For example, by balancing the conductivity and reversible capacity, researchers in the US National Aeronautics and Space Administration (NASA) have shown that 500 Wh/kg solid-state Li–Se/S batteries can power cars and even electric aircraft.

High-performance rechargeable oxygen electrodes are key devices for realizing high-specific-energy batteries, including zinc–air and lithium–air batteries. However, these batteries have severe problems of premature decay in energy efficiency by serious corrosion, wide charge–discharge gap, and catalyst peeling off. Herein, we propose a “smart dual-oxygen electrode”, which is composed of an intelligent switch control module + heterostructured Fe1Ni3-LDH/PNCNF OER catalysis electrode layer + ion conductive | electronic insulating membrane + Pt/C ORR catalysis electrode layer, where OER and ORR layers are automatically switched by the intelligent switch control module as required. This smart dual-oxygen electrode offers an ultralow energy efficiency decay rate of 0.0067% after 300 cycles during cycling, much lower than that of the commercial Pt/C electrode (1.82%). The assembled rechargeable zinc–air battery (RZAB) displays a super narrow voltage gap and achieves a high energy efficiency of 71.7%, far higher than that of the existing RZABs (about 50%). Therefore, this strategy provides a complete solution for designing various high-performance metal–air secondary batteries.

Widespread adoption of lithium-sulfur batteries (LSBs) remains inhibited, given their unrealized energy densities, drastic capacity fade, and severe self-discharge stemming from the polysulfide shuttle effect. Although countless endeavors have attempted to overcome this key bottleneck, “shuttle-free” lithium-sulfur batteries (SfLSBs) that operate by single-phase solid-solid conversion are a preeminent technology with vast potential to facilitate universal adoption of LSBs. In this review, we first provide a fundamental understanding of SfLSBs by comparing their operating mechanism with traditional LSBs. Then we present various strategies that have been used to enable SfLSBs in the liquid and solid state, placing particular emphasis on cathode materials. Finally, perspectives ranging from fundamental research to practical engineering design are provided to bolster future endeavors regarding SfLSB technology.

The revival of ternary halides Li–M–X (M = Y, In, Zr, etc.; X = F, Cl, Br) as solid-state electrolytes (SSEs) shows promise in realizing practical solid-state batteries due to their direct compatibility toward high-voltage cathodes and favorable room-temperature ionic conductivities. Most of the reported superionic halide SSEs have a structural pattern of [MCl6]x−octahedra and generate a tetrahedron-assisted Li+ion diffusion pathway. Here, we report a new class of zeolite-like halide frameworks, SmCl3, for example, in which 1-dimensional channels are enclosed by [SmCl9]6–tricapped trigonal prisms to provide a short jumping distance of 2.08 Å between two octahedra for Li+ion hopping. The fast Li+diffusion along the channels is verified through ab initio molecular dynamics simulations. Similar to zeolites, the SmCl3framework can be grafted with halide species to obtain mobile ions without altering the base structure, achieving an ionic conductivity over 10–4S cm–1at 30 °C with LiCl as the adsorbent. Moreover, the universality of the interface-bonding behavior and ionic diffusion in a class of framework materials is demonstrated. It is suggested that the ionic conductivity of the MCl3/halide composite (M = La–Gd) is likely in correlation with the ionic conductivity of the grafted halide species, interfacial bonding, and framework composition/dimensions. This work reveals a potential class of halide structures for superionic conductors and opens up a new frontier for constructing zeolite-like frameworks in halide-based materials, which will promote the innovation of superionic conductor design and contribute to a broader selection of halide SSEs.

Using the electrochemical CO2reduction reaction (CO2RR) with Cu-based electrocatalysts to achieve carbon-neutral cycles remains a significant challenge because of its low selectivity and poor stability. Modulating the surface electron distribution by defects engineering or doping can effectively improve CO2RR performance. Herein, we synthesize the electrocatalyst of Vo-CuO(Sn) nanosheets containing oxygen vacancies and Sn dopants for application in CO2RR-to-CO. Density functional theory calculations confirm that the incorporation of oxygen vacancies and Sn atoms substantially reduces the energy barrier for *COOH and *CO intermediate formation, which results in the high efficiency, low overpotential, and superior stability of the CO2RR to CO conversion. This electrocatalyst possesses a high Faraday efficiency (FE) of 99.9% for CO at a low overpotential of 420 mV and a partial current density of up to 35.22 mA cm–2at −1.03 V versus reversible hydrogen electrode (RHE). The FECOof Vo-CuO(Sn) could retain over 95% within a wide potential area from −0.48 to −0.93 V versus RHE. Moreover, we obtain long-term stability for more than 180 h with only a slight decay in its activity. Therefore, this work provides an effective route for designing environmentally friendly electrocatalysts to improve the selectivity and stability of the CO2RR to CO conversion.

Recent years have witnessed significant advances in all-solid-state lithium batteries (ASSLBs). However, soft breakdown hidden in ASSLBs has been overlooked in most previous research. Moreover, existing assessment criteria are insensitive to detecting soft breakdown. Here, we first discuss the current status of ASSLBs and highlight the challenges of evaluating the soft breakdown phenomenon with the existing evaluation method. A simple but effective strategy—cyclic voltammetry—is then proposed to diagnose soft breakdown in all-solid-state symmetric cells. To establish a standard testing protocol, several critical parameters that have not been well emphasized thus far, including areal capacity, thickness, and porosity of solid electrolytes, are numerically analyzed to understand their significant effect on the energy density of practical all-solid-state pouch cells. With these understandings, we establish a definitive testing benchmark with the aim of guiding the research efforts toward in-depth scientific understanding and practical engineering design.

The quiescent electrolyte causes serious concentration polarization and dendrite problems during the charging and discharging of the battery, which restricts the development of metal secondary batteries and flow batteries. Herein, we report a new concept of ion motors, with which the directional driving and uniformity of the electrolyte are realized to eliminate the concentration polarization and dendritic phenomenon for secondary metal batteries and flow batteries without additional external energy. In this study, a dendrite-free secondary metal battery with ion motors is constructed to eliminate a considerable concentration polarization voltage by a tiny induced counter electromotive force generated by Lorentz force, significantly improving the output power and energy efficiency of the battery. An actual pump-free flow battery with an ion motor is also assembled, which overcomes the problems of low energy efficiency and the complex structure caused by the traditional flow battery requiring 1−2 pumps to drive the electrolyte. The efficiency of ion motors to drive the electrolyte is hundreds of times higher than that of the mechanical pump. Therefore, the ion motor provides a universal strategy for designing more pump-free flow batteries and metal secondary batteries without the risk of dendrites in the future.

Structural evolutions are crucial for determining the performance of high-voltage lithium, manganese-rich layered cathodes. Moreover, interface between electrode and electrolyte plays a critical role in governing ionic transfer in all-solid-state batteries. Here, we unveil two different types of porous structure in Li1.2Ni0.2Mn0.6O2cathode with LiPON solid-state electrolyte. Nanopores are found near the cathode/electrolyte interface at pristine state, where cation mixing, phase transformation, oxygen loss, and Mn reduction are also found. In situLi+extraction induces the evolution of nanovoids, initially formed near the interface then propagated into the bulk. Despite the development of nanovoids, layered structure is conserved, suggesting the nature of nanopores and nanovoids are different and their impact would be divergent. This work demonstrates the intrinsic interfacial layer, as well as the dynamic scenario of nanovoid formation inside high-capacity layered cathode, which helps to understand the performance fading in cathodes and offers insight into the all-solid-state battery design.

In this study, the morphological distribution of Ru on nitrogen-doped graphene (NG) could be rationally regulated viamodulating the combination mode between Ru precursor and the zeolite imidazolate framework-8 (ZIF-8). The cation exchange and host-guest strategies respectively resulted in two different combination modes between Ru precursor and ZIF-8 anchored on graphene. Following pyrolysis of the above precursors, Ru single-atom sites (SASs) with and without Ru nanoparticles (NPs) were formed selectively on NG (denoted as Ru SASs+NPs/NG and Ru SASs/NG, respectively). Ru SASs+NPs/NG exhibited excellent hydrogen evolution reaction (HER) performance in alkaline solutions (η10=12 mV, 12.57 A mg−1Ruat 100 mV), which is much better than Ru SASs/NG. The experimental and theoretical study revealed that Ru SASs could adsorb hydrogen with optimal adsorption strength, while Ru NPs could lower the barrier of water molecule dissociation, and thus Ru SASs and Ru NPs could synergistically promote the catalytic performance of HER in alkaline solutions.

Two-dimensional conductive metal–organic frameworks (2D CMOFs) can be regarded as high-performance electrode substances owing to their rich hierarchical porous architecture and excellent electrical conductivity. However, the sluggish kinetics behavior of electrodes within the bulk structure restricts their advances in energy storage fields. Herein, a series of graphene-based mixed-dimensional composite aerogels are achieved by incorporating the 2D M-tetrahydroxy-1,4-quinone (M-THQ) (M = Cu, Cu/Co, or Cu/Ni) into CNTs@rGO aerogel electrodes using a 3D-printing direct ink writing (DIW) technique. Benefiting from the high capacity of M-THQ and abundant porosity of the 3D-printed microlattice electrodes, an excellent capacitive performance of the M-THQ@CNTs@rGO cathodes is achieved based on the fast electron/ion transport. Furthermore, the 3D-printed lithium-ion hybrid supercapacitor (LIHCs) device assembled with Cu/Co-THQ@CNTs@rGO cathode and C60@VNNWs@rGO anode delivers a remarkable electrochemical performance. More importantly, this work manifests the practicability of printing 2D CMOFs electrodes, which provides a substantial research basis for 3D printing energy storage.

In this work, several carbon-decorated Na3V2(PO4)3materials (NVP@C-750/800/850) are successfully fabricated using a sol–gel approach and subsequent heat treatment. When NVP@C-800 is used as a cathode, it shows an ultralong cycle life (2000 cycles) at a high rate of 10C, which is superior to the other two electrodes and those of reported NVP@C cathodes in the literature. The excellent results of NVP@C-800 are attributed to its nanostructure and the well-defined conductive carbon layer. The symmetric sodium (Na)-ion battery (SIB) with NVP@C-800 as both a cathode and an anode shows a high capacity at 40 mA g–1with a voltage plateau of about 1.79 V and energy density of 113 W h kg–1, revealing that NVP@C is of great application prospect.

Black phosphorus has been reported as a remarkable 2D material due to its unique electrical, optical, and thermal properties, leading to promising device applications in optics, thermoelectricity, physics, material science, and energy storage. Indeed, the intrinsic band structure of black phosphorus is adjustable through doping various heteroatoms to further improve the electrical and optical performance. However, it is difficult for traditional characterization methods (e.g., X-ray diffraction or X-ray photoelectron spectroscopy) to give a clear picture of the local structure around the dopant atoms. To solve this problem, we have applied synchrotron based X-ray absorption spectroscopy techniques like X-ray absorption near edge structure and extended X-ray absorption fine structure combined with density functional theory calculations to reveal the local structure around the Se dopant in Se-doped BP. It is found that Se exists as both dopant and pure Se in Se-doped BP, while the ratio of dopant to pure Se increases with increasing Se content in the raw material. This is the first confirmation of the coexistence of two dopant element phases in the doped-BP literature. Meanwhile, the introduction of Se successfully decreases the bandgap and resistivity of BP. In addition, the bandgap and resistivity can be further reduced by increasing the amount of Se.

Rechargeable all-solid-state Li batteries (ASSLBs) are considered to be the next generation of electrochemical energy storage systems. The development of solid-state electrolytes (SSEs), which are key materials for ASSLBs, is therefore one of the most important subjects in modern energy storage chemistry. Various types of electrolytes such as polymer-, oxide-, and sulfide-based SSEs have been developed to date and the discovery of new superionic conductors is still ongoing. Metal-halide SSEs (Li-M-X, where M is a metal element and X is a halogen) are emerging as new candidates with a number of attractive properties and advantages such as wide electrochemical stability windows (0.36–6.71 V vs Li/Li+) and better chemical stability toward cathode materials compared to other SSEs. Furthermore, some of the metal-halide SSEs (such as the Li3InCl6developed by our group) can be directly synthesized at large scales in a water solvent, removing the need for special apparatus or handling in an inert atmosphere. Based on the recent advances, herein we focus on the topic of metal-halide SSEs, aiming to provide a guidance toward further development of novel halide SSEs and push them forward to meet the multiple requirements of energy storage devices.

Establishing a stable, stress-relieving configuration is imperative to achieve a reversible silicon anode for high energy density lithium-ion batteries. Herein, we propose a silicon composite anode (denoted as T-Si@C), which integrates free space and mixed carbon shells doped with rigid TiO2/Ti5Si3nanoparticles. In this configuration, the free space accommodates the silicon volume fluctuation during battery operation. The carbon shells with embedded TiO2/Ti5Si3nanoparticles maintain the structural stability of the anode while accelerating the lithium-ion diffusion kinetics and mitigating interfacial side reactions. Based on these advantages, T-Si@C anodes demonstrate an outstanding lithium storage performance with impressive long-term cycling reversibility and good rate capability. Additionally, T-Si@C//LiFePO4full cells show superior electrochemical reversibility. This work highlights the importance of rational structural manipulation of silicon anodes and affords fresh insights into achieving advanced silicon anodes with long life.

Al2O3-graphene nanolayers are widely used within integrated micro/nanoelectronic systems; however, their lifetimes are largely limited by fracture both statically and dynamically. Here, we present a static and fatigue study of thin (1–11 nm) free-standing Al2O3-graphene nanolayers. A remarkable fatigue life of greater than one billion cycles was obtained for films <2.2 nm thick under large mean stress levels, which was up to 3 orders of magnitude longer than that of its thicker (11 nm) counterpart. A similar thickness dependency was also identified for the elastic and static fracture behavior, where the enhancement effect of graphene is prominent only within a thickness of ∼3.3 nm. Moreover, plastic deformation, manifested by viscous creep, was observed and appeared to be more substantial for thicker films. This study provides mechanistic insights on both the static and dynamic reliability of Al2O3-graphene nanolayers and can potentially guide the design of graphene-based devices.

Li–O2battery is a promising rechargeable battery candidate due to its ultrahigh theoretical energy density. However, safety issues and poor cycling stability of Li–O2batteries caused by the formation of Li dendrites and the use of organic liquid electrolytes inhibit their practical applications. Here, we propose a hybrid solid electrolyte composed of three-dimensional (3D) porous garnet microstructure (PSSE) infused with gel polymer electrolyte (GPE) (PSSE/GPE) to enhance the safety and cycling stability of Li–O2batteries. In this hybrid solid electrolyte, the 3D garnet microstructure serves as a rigid backbone to suppress Li dendrites, while the consecutive GPE in PSSE serves as an ionic highway, ensuring a high ionic conductivity (1.06 × 10–3S cm–1) in the bulk. Besides, the hybrid electrolyte offers the ability to block O2crossover and maintain good compatibility with Li metal anode and advanced air electrode. As a result, the cycle life of Li symmetric cell is dramatically improved almost 60 times (6000 h, 250 days) by replacing GPE with PSSE/GPE. The Li–O2battery based on PSSE/GPE shows a long cycle life of 194 cycles with a high cycling capacity of 1250 mA h g–1. The present study demonstrates a novel class of hybrid solid electrolyte for high-performance solid-state Li–O2batteries.

Recently, halide solid-state electrolytes (SSEs) have been reported to exhibit high ionic conductivity and good compatibility with cathode materials. However, the air stability of halide-based electrolytes is one important factor related to ionic conductivity upon exposure to air for practical applications. The instability mechanism of Li3InCl6toward air is not clearly understood. Herein, we for the first time report the application of operandooptical microscopy, Raman spectroscopy, synchrotron-based X-ray powder diffraction, and in situX-ray absorption near-edge structure for the study of halide electrolyte air stability. Using these methods, we have been able to track the degradation process of Li3InCl6exposed to air. It is for the first time found that Li3InCl6is hydrophilic in character, leading to the absorption of moisture from the air, and a portion of Li3InCl6reacts with absorbed H2O to form In2O3, LiCl, and HCl. Moreover, the remaining electrolyte absorbs H2O to form a hydrate, Li3InCl6·xH2O. The reaction results in a decrease of ionic conductivity. Additionally, the influence of air stability on the practical application of Li3InCl6has been explored. Li3InCl6shows much better stability against air with low humidity (3%) and in battery dry rooms, making it a promising SSE for application in the commercial lithium-ion manufacturing industry.

The pursuit of a high-capacity anode material has been urgently required for commercializing sodium-ion batteries with a high energy density and an improved working safety. In the absence of thermodynamically stable sodium intercalated compounds with graphite, constructing nanostructures with expanded interlayer distances is still the mainstream option for developing high-performance carbonaceous anodes. In this regard, a surface-functionalized and pore-forming strategy through a facile CO2thermal etching route was rationally adopted to engineer negligible oxygenated functionalities on commercial carbon for boosting the sodium storage process. Benefitted from the abundant ionic/electronic pathways and more active reaction sites in the microporous structure with noticeable pseudocapacitive behaviors, the functionalized porous carbon could achieve a highly reversible capacity of 505 mA h g–1at 50 mA g–1, an excellent rate performance of 181 mA h g–1at 16,000 mA g–1, and an exceptional rate cycle stability of 176 mA h g–1at 3200 mA g–1over 1000 cycles. These outstanding electrochemical properties should be ascribed to a synergistic mechanism, fully utilizing the graphitic and amorphous structures for synchronous intercalations of sodium ions and solvated sodium ion compounds, respectively. Additionally, the controllable generation and evolution of a robust but thin solid electrolyte interphase film with the emergence of obvious capacitive reactions on the defective surface, favoring the rapid migration of sodium ions and solvated species, also contribute to a remarkable electrochemical performance of this porous carbon black.

The high ionic conductivity, air/humidity tolerance, and related chemistry of Li3MX6solid-state electrolytes (SSEs, M is a metal element, and X is a halogen) has recently gained significant interest. However, most of the halide SSEs suffer from irreversible chemical degradation when exposed to a humid atmosphere, which originates from hydrolysis. Herein, the function of the M atom in Li3MX6was clarified by a series of Li3Y1–xInxCl6(0 ≤ x< 1). When the ratio of In3+was increased, a gradual structural conversion from the hexagonal-closed-packed (hcp) anion arrangement to cubic-closed-packed (ccp) anion arrangement has been traced. Compared to hcp anion sublattice, the Li3MX6with ccp anion sublattice reveals faster Li+migration. The tolerance of Li3Y1–xInxCl6towards humidity is highly improved when the In3+content is high enough due to the formation of hydrated intermediates. The correlations among composition, structure, Li+migration, and humidity stability presented in this work provide insights for designing new halide-based SSEs.

Superoxide-based Na–O2batteries have been considered as some of the most promising candidates for next-generation energy storage systems due to their high theoretical energy density and energy efficiency. However, to fully realize the advantages of Na–O2batteries, the underutilization of air electrodes and poor cycling performance caused by limited O2transport in the air electrodes must be addressed. In this work, 3D printing of a reduced graphene oxide (rGO)-based air electrode with a hierarchical porous structure was first demonstrated as being “O2breathable” for Na–O2batteries. The unique cathode structure features noncompetitive and continuous pathways for O2, Na+ions, and electrons. The macropores provide smooth passages to facilitate O2access across the whole electrode, while the micropores between rGO sheets serve as electrolyte reservoirs and accommodate NaO2. The efficiently packed rGO sheets ensure sufficient electronic conductivity within the 3D architecture. Na–O2batteries using these “O2breathable” electrodes can achieve a high capacity of 13484.6 mAh g–1at 0.2 A g–1and a stable cycling performance over 120 cycles with a cutoff capacity of 500 mAh g–1at 0.5 A g–1. The 3D-printed “O2breathable” electrodes evidently demonstrate the importance of a refined balance between electronic conductivity and O2transport for high-performance Na–O2batteries.

This study reports a high-performing nonprecious metal catalyst for the oxygen reduction reaction that is composed of highly dispersed Fe centered active sites on bamboolike carbon nanotubes. NH2-MIL-88B is used as the iron source and ZIF-8 as the carbon source. The precursors are uniformly mixed by ball milling, which destroys their crystal structures. A bamboolike carbon nanotube network results from the pyrolysis of the mixed precursors. The morphology is controlled by the proportion of the precursors and the pyrolysis temperature. The catalyst shows excellent oxygen reduction activity in both half-cell and full-cell tests. The onset potential and half-wave potential are 0.96 and 0.78 V vs RHE, respectively. In the fuel cell test, the current density reaches 0.85 A cm–2at 0.7 V and 1.24 A cm–2at 0.6 V (iR-corrected). The novel synthesis approach of the highly dispersed catalyst provides new strategy in the design of high effective nonprecious metal catalysts for fuel cell.

The enabling of high energy density of all-solid-state lithium batteries (ASSLBs) requires the development of highly Li+-conductive solid-state electrolytes (SSEs) with good chemical and electrochemical stability. Recently, halide SSEs based on different material design principles have opened new opportunities for ASSLBs. Here, we discovered a series of LixScCl3+xSSEs (x= 2.5, 3, 3.5, and 4) based on the cubic close-packed anion sublattice with room-temperature ionic conductivities up to 3 × 10–3S cm–1. Owing to the low eutectic temperature between LiCl and ScCl3, LixScCl3+xSSEs can be synthesized by a simple co-melting strategy. Preferred orientation is observed for all the samples. The influence of the value of xin LixScCl3+xon the structure and Li+diffusivity were systematically explored. With increasing xvalue, higher Li+, lower vacancy concentration, and less blocking effects from Sc ions are achieved, enabling the ability to tune the Li+migration. The electrochemical performance shows that Li3ScCl6possesses a wide electrochemical window of 0.9–4.3 V vs Li+/Li, stable electrochemical plating/stripping of Li for over 2500 h, as well as good compatibility with LiCoO2. LiCoO2/Li3ScCl6/In ASSLB exhibits a reversible capacity of 104.5 mAh g–1with good cycle life retention for 160 cycles. The observed changes in the ionic conductivity and tuning of the site occupations provide an additional approach toward the design of better SSEs.

Critical factors that govern the composition and morphology of discharge products are largely unknown for Na–O2batteries. Here we report a reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) process in a sodium–oxygen battery observed using in situenvironmental-transmission electron microscopy (TEM) experiment. The reaction mechanism and phase evolution are probed using in situelectron diffraction and TEM imaging. The reversible ORR and OER cycling lies upon the nanosized copper clusters that were formed in situby sodiation of CuS. In situelectron diffraction revealed the formation of NaO2initially, which then disproportionated into orthorhombic and hexagonal Na2O2and O2. Na2O2was the major final ORR product that uniformly covered the whole wire-shape cathode. This uniform product morphology largely increased the application feasibility of Na–O2batteries in industry. In the following OER process, the Na2O2transformed to NaO2, which resulted in volume expansion at first, and then the NaO2decomposed to sodium ions and O2gas. Galvanostatic charge/discharge profiles of CuS in real Na–O2cells revealed a maximum capacity over 3 mAh cm–2with a discharge cutoff voltage of 1.8 V and high cycling stability. The nanosized copper catalyst plays a dominating role in controlling the morphology, chemical composition of discharge products, and reversibility of this Na–O2battery. Our finding shines light on the exploration of effective catalysts for the Na–O2battery.

Sulfide solid electrolytes have recently attracted significant interest for use in all-solid-state lithium batteries (ASSLBs) due to their high ionic conductivity. However, one of the main challenges associated with the commercialization of sulfide-based electrolytes is their instability toward air/moisture, which leads to complex processing requirements. Herein, we develop a strategy to not only increase ionic conductivity but also obtain high air stability of the Li10Ge(P1–xSbx)2S12electrolyte system with soft acid Sb substitution. Theoretical calculations predict the Sb substitution in (Ge,P)S4tetrahedral sites, which is further confirmed by the X-ray diffraction Rietveld refinement and synchrotron X-ray absorption fine structure analysis. Opened channels and increased unit cell volume are achieved with an appropriate amount of Sb substitution, leading to an ultrahigh ionic conductivity of 17.3 ± 0.9 mS cm–1. The softer acidity of Sb compared to that of P also ensures strong covalent bonding with S in Li10Ge(P1–xSbx)2S12, which improves the air stability of the electrolyte. Moreover, the air-exposed samples exhibit high ionic conductivities of 12.1–15.7 mS cm–1. Bulk-type ASSLBs assembled with either pristine or air-exposed Li10Ge(P1–xSbx)2S12exhibit high initial Coulombic efficiencies of 92.8 and 91.0%, respectively, with excellent cycling performances of over 110 cycles. The observed variations in the structural parameters and bond strengths provide an effective approach toward designing more ionically conductive and stable solid-state electrolytes.

Metal–organic frameworks (MOFs) are important porous materials. Post-synthetic modification (PSM) of MOFs via the pendant groups or secondary functional groups of organic linkers has been widely used to introduce new or enhance existing properties of MOFs for various practical applications. In this work, we have constructed, for the first time, a novel platform for PSM of MOFs by introducing an anhydride functional group into a hierarchically porous MOF (MIL-121) as an effective anchor. We have demonstrated that the combination of the high reactivity of anhydride and hierarchical porosity makes this protocol particularly novel and important, as it led to excellent opportunities of incorporating not only a wide variety of organic molecules with different sizes and chemical nature but also the noble metal complexes in MOFs. Specifically, we show that the anhydride group decorated in the MOF exhibits a high reactivity toward covalently binding 10 different guest molecules including alcohols, amines, thiols, and noble metal (Pt(II)/Pt(IV)) complexes, whereas the hierarchical pores created in the MOF allow the incorporation of guest species varying in size from methanol to larger molecules such as polyaromatic amines. This novel approach provides the community with a new avenue to prepare MOF-based materials for targeted applications. To illustrate this point, we furnish an example of using this new platform to prepare a Pt-based electrocatalyst which shows excellent catalytic activity toward the oxygen reduction reaction (ORR), a pivotal half-reaction in hydrogen–oxygen fuel cells and other energy storage and conversion devices.

The development of highly active and stable electrocatalysts toward oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is a key for commercial application of fuel cells and water splitting. Here, we report a highly active and stable Pt nanoparticles (NPs) encapsulated in ultrathin two-dimensional (2D) carbon layers derived from the ultrathin 2D metal–organic framework precursor (ZIF-67). Electrochemical tests reveal that our approach not only stabilized Pt NPs successfully but also boosted Pt activities toward ORR and HER. We found that our Pt catalysts encapsulated in ultrathin 2D carbon layers exhibited an ORR activity of 5.9 and 12 times greater than those of the commercial Pt/C and Pt/RGO without 2D carbon layer protection. Our encapsulated Pt catalysts also show more than nine times higher stability than those of Pt/C catalysts. In addition to ORR, our novel encapsulated Pt catalysts display an extraordinary stability and activity toward HER, with a lower overpotential (14.3 mV in acidic media and 37.2 mV in alkaline media) at a current density of 10 mA cm–2than Pt/C catalysts (23.1 mV in acidic media and 92.1 mV in alkaline media). The enhanced electrochemical activities and stability of our encapsulated Pt catalysts are attributed to the synergistic effect of Pt-based NPs and ultrathin 2D carbon layers derived from ZIF-67 with enriched active sites Co–Nx. First-principles simulations reveal that the synergistic catalysis of Pt-based NPs and Co–Nxderived from ZIF-67 improves the activity for ORR and HER.

Sodium–oxygen (Na-O2) batteries are considered a higher-energy-efficiency alternative to the lithium–oxygen (Li-O2) system. The reversible superoxide electrochemistry governing the oxygen reduction and evolution reactions in Na-O2cells results in a relatively lower charging overpotential. Thus, significant research attention has been directed toward Na-O2in the hope of developing a high-energy-storage system. This review provides a brief overview of the most recent research progress in this field with special emphasis on the chemical and electrochemical reaction mechanisms. All major components of the cell including the positive and negative electrodes as well as the electrolyte are covered. Moreover, areas requiring more research attention are specified and potential directions for future research are proposed.

Phosphorene, single- or few-layered black phosphorus, has been rediscovered as a promising two-dimensional material owing to its unique optical, thermal, and electrical properties with potential applications in optoelectronics, nanoelectronics, and energy storage. However, rapid degradation under ambient condition highly limits the practical applications of phosphorene. Solving the degradation problem demands an understanding of the oxidization process. We, for the first time, apply synchrotron-based X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), and scanning transmission X-ray microscopy (STXM) for the nanoscale chemical imaging of phosphorene degradation. Through these methods, we have identified chemical details of the morphological effect and clarified thickness and proximity effects, which control the oxidization process. Furthermore, the entire oxidization process of phosphorene has also been studied by in situ XPS and XANES, showing the step-by-step oxidization process under the ambient condition. Theoretical calculations at the density functional theory level support experimental findings. This detailed study provides a better understanding of phosphorene degradation and is valuable for the development of phosphorene-based materials.

All-solid-state batteries are expected to be promising next-generation energy storage systems with increased energy density compared to the state-of-the-art Li-ion batteries. Nonetheless, the electrochemical performances of the all-solid-state batteries are currently limited by the high interfacial resistance between active electrode materials and solid-state electrolytes. In particular, elemental interdiffusion and the formation of interlayers with low ionic conductivity are known to restrict the battery performance. Herein, we apply a nondestructive variable-energy hard X-ray photoemission spectroscopy to detect the elemental chemical states at the interface between the cathode and the solid-state electrolyte, in comparison to the widely used angle-resolved (variable-angle) X-ray photoemission spectroscopy/X-ray absorption spectroscopy methods. The accuracy of variable-energy hard X-ray photoemission spectroscopy is also verified with a focused ion beam and high-resolution transmission electron microscopy. We also show the significant suppression of interdiffusion by building an artificial layer via atomic layer deposition at this interface.

Abstract: Single-atom catalysis is a powerful and attractive technique with exceptional performance, drastic cost reduction and notable catalytic activity and selectivity. In single-atom catalysis, supported single-atom catalysts contain isolated individual atoms dispersed on, and/or coordinated with, surface atoms of appropriate supports, which not only maximize the atomic efficiency of metals, but also provide an alternative strategy to tune the activity and selectivity of catalytic reactions. This review will highlight the attributes of single-atom catalysis and summarize the most recent advancements in single-atom catalysts with a focus on the design of highly active and stable single atoms. In addition, new research directions and future trends will also be discussed. Graphic Abstract:

Efficient and stable electrocatalysts for oxygen reduction reaction and freestanding electrode structure were developed to reduce the use of polymer binders in the cathode of metal–air batteries. Considering the unique geometrical configurations of helical carbon nanotubes (CNTs) and improved properties compared with straight CNTs, we prepared high-purity Co@CoOx/helical nitrogen-doped carbon nanotubes (Co@CoOx/HNCNTs) on a carbon fiber paper by hydrothermal and single-step in situ chemical vapor deposition strategies. Under an optimized growth time (1 h), the synthesized Co@CoOx/HNCNTs provide richer edge defects and active sites and show prominent electrocatalytic performance toward oxygen reduction reaction (ORR) under alkaline media compared with Co@CoOx/HNCNTs-0.5 h and Co@CoOx/HNCNTs-2 h. The soft X-ray absorption spectroscopy technique is used to investigate the influences of different growth times on the electronic structure and local chemical configuration of Co@CoOx/HNCNTs. Furthermore, the Al–air coin cell employing Co@CoOx/HNCNTs-1 h as the binder-free cathode exhibits an open-circuit voltage of 1.48 V, a specific capacity of 367.31 mA h g–1at the discharge current density of 1.0 mA cm–2, and a maximum power density (Pmax) of 3.86 mW cm–2, which are superior to those of Co@CoOx/HNCNTs-0.5 h and Co@CoOx/HNCNTs-2 h electrodes. This work provides valuable insights into the development of scalable binder-free cathodes, exploiting HNCNT composite materials with an outstanding electrocatalytic performance for ORR in Al–air systems.

We report the effort in designing layered SnS2nanocrystals decorated on nitrogen and sulfur dual-doped graphene aerogels (SnS2@N,S-GA) as anode material of SIBs. The optimized mass loading of SnS2along with the addition of nitrogen and sulfur on the surface of GAs results in enhanced electrochemical performance of SnS2@N,S-GA composite. In particular, the introduction of nitrogen and sulfur heteroatoms could provide more active sites and good accessibility for Na ions. Moreover, the incorporation of the stable SnS2crystal structure within the anode results in the superior discharge capacity of 527 mAh g–1under a current density of 20 mA g–1upon 50 cycles. It maintains 340 mAh g–1even the current density is increased to 800 mA g–1. Aiming to further systematically study mechanism of composite with improved SIB performance, we construct the corresponding models based on experimental data and conduct first-principles calculations. The calculated results indicate the sulfur atoms doped in GAs show a strong bridging effect with the SnS2nanocrystals, contributing to build robust architecture for electrode. Simultaneously, heteroatom dual doping of GAs shows the imperative function for improved electrical conductivity. Herein, first-principles calculations present a theoretical explanation for outstanding cycling properties of SnS2@N,S-GA composite.

3D all-solid-state microbatteries are promising onboard power systems for autonomous devices. The fabrication of 3D microbatteries needs deposition of active materials, especially solid-state electrolytes, as conformal and pinhole free thin films in 3D architectures, which has proven very difficult for conventional deposition techniques, such as chemical vapor deposition and physical vapor deposition. Herein, we report an alternative technique, atomic layer deposition (ALD), for achieving ideal solid-state electrolyte thin films for 3D microbatteries. Lithium tantalate solid-state electrolytes, with well-controlled film composition and film thickness, were grown by ALD at 225 °C using subcycle combination of 1 × Li2O + n× Ta2O5(1 ≤ n≤ 10). The film composition was tunable by varying Ta2O5subcycles (n), whereas the film thickness displayed a linear relationship with ALD cycle number, due to the self-limiting nature of the ALD process. Furthermore, the lithium tantalate thin films showed excellent uniformity and conformity in 3D anodic aluminum oxide template. Moreover, impedance testing showed that the lithium tantalate thin film exhibited a lithium ion conductivity of 2 × 10–8S/cm at 299 K. The lithium tantalate thin films by ALD, featured with well-controlled film thickness and composition, excellent step coverage, and moderate ionic conductivity at room temperature, would be promising solid-state electrolytes for 3D microbatteries.

Aluminum foil is the predominant cathodic current collector in lithium-based batteries due to the high electronic conductivity, stable chemical/electrochemical properties, low density, and low cost. However, with the development of next-generation lithium batteries, Al current collectors face new challenges, such as the requirement of increased chemical stability at high voltage, long-cycle-life batteries with different electrolyte systems, as well as improved electronic conductivity and adhesion for new electrode materials. In this study, we demonstrate a novel graphene-like carbon (GLC) coating on the Al foil in lithium-based batteries. Various physical and electrochemical characterizations are conducted to reveal the electronic conductivity and electrochemical stability of the GLC-Al foil in both carbonate- and ether-based electrolytes. Full-cell tests, including Li–S batteries and high-voltage Li-ion batteries, are performed to demonstrate the significantly improved cycling and rate performance of batteries with the use of the GLC-Al foil as current collectors. The cell using the GLC-Al foil can greatly reduce the potential polarization in Li–S batteries and can obtain a reversible capacity of 750 mAh g–1over 100 cycles at 0.5C. Even with high-sulfur-loading cathodes, the Li–S battery at 1C still maintains over 500 mAh g–1after 100 cycles. In high-voltage Li-ion batteries, the GLC-Al foil significantly improves the high-rate performance, showing an increased retained capacity by over 100 mAh g–1after 450 cycles at 1C compared to the bare foil. It is believed that the developed GLC-Al foil brings new opportunities to enhance the battery life of lithium-based batteries.

Various single-crystalline Ag nanostructures including dendrites, dendritic flowers, and cactus-like rods have been successfully synthesized in high yield through a simple, facile, cost-effective method based on the galvanic replacement reaction. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and energy dispersive X-ray spectroscopy (EDX). The morphology and structure of Ag products can be well controlled by tuning the concentrations of Ag metal salt precursor. Through a series of time-dependent morphological evolution studies, the growth processes of Ag nanostructures have been systematically investigated and the corresponding growth mechanisms have been discussed.

The development of hybrid capacitors (HCs) has become essential for meeting the rising demand for devices that simultaneously deliver high energy with high power. Although the challenge to develop high-performance HCs remains great, it is also simultaneously essential to develop an eco-friendly and cleaner energy storage system for sustainable future use. To date, hybrid capacitors utilize heavily toxic inorganic insertion electrodes and hazardous coke-derived porous carbon adsorption electrodes to host ions. Herein, we present a conceptually novel all-organic sodium hybrid capacitor (OHC), rationally designed by replacing the conventional electrodes with clean, green, and metal free organic molecules, to host ions. A high energy density of ∼95 Wh kg–1and an ultrahigh power density of 7 kW kg–1(based on active mass in both electrodes) are achieved with a low energy loss of ∼0.22% per 100 cycles (∼89% retention after 5000 cycles), outperforming conventional HCs. The outstanding energy–power behavior of OHC bridges the performance gap between batteries and capacitors. This research holds great promise for the development of next-generation eco-friendly, clean, green, and safer high-energy, high-power devices.

The recently surged halide-based solid electrolytes (SEs) are great candidates for high-performance all-solid-state batteries (ASSBs), due to their decent ionic conductivity, wide electrochemical stability window, and good compatibility with high-voltage oxide cathodes. In contrast to the crystalline phases in halide SEs, amorphous components are rarely understood but play an important role in Li-ion conduction. Here, we reveal that the presence of amorphous component is common in halide-based SEs that are prepared via mechanochemical method. The fast Li-ion migration is found to be associated with the local chemistry of the amorphous proportion. Taking Zr-based halide SEs as an example, the amorphization process can be regulated by incorporating O, resulting in the formation of corner-sharing Zr–O/Cl polyhedrons. This structural configuration has been confirmed through X-ray absorption spectroscopy, pair distribution function analyses, and Reverse Monte Carlo modeling. The unique structure significantly reduces the energy barriers for Li-ion transport. As a result, an enhanced ionic conductivity of (1.35 ± 0.07) × 10–3S cm–1at 25 °C can be achieved for amorphous Li3ZrCl4O1.5. In addition to the improved ionic conductivity, amorphization of Zr-based halide SEs via incorporation of O leads to good mechanical deformability and promising electrochemical performance. These findings provide deep insights into the rational design of desirable halide SEs for high-performance ASSBs.

High-energy-density lithium (Li)–air cells have been considered a promising energy-storage system, but the liquid electrolyte-related safety and side-reaction problems seriously hinder their development. To address these above issues, solid-state Li–air batteries have been widely developed. However, many commonly-used solid electrolytes generally face huge interface impedance in Li–air cells and also show poor stability towards ambient air/Li electrodes. Herein, we fabricate a differentiating surface-regulated ceramic-based composite electrolyte (DSCCE) by constructing disparately LiI-containing polymethyl methacrylate (PMMA) coating and Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) layer on both sides of Li1.5Al0.5Ge1.5(PO4)3(LAGP). The cathode-friendly LiI/PMMA layer displays excellent stability towards O2−and also greatly reduces the decomposition voltage of discharge products in Li–air system. Additionally, the anode-friendly PVDF-HFP coating shows low-resistance properties towards anodes. Moreover, Li dendrite/passivation derived from liquid electrolyte-induced side reactions and air/I-attacking can be obviously suppressed by the uniform and compact composite framework. As a result, the DSCCE-based Li–air batteries possess high capacity/low voltage polarization (11,836 mA h g−1/1.45 V under 500 mA g−1), good rate performance (capacity ratio under 1000 mA g−1/250 mA g−1is 68.2%) and long-term stable cell operation (300 cycles at 750 mA g−1with 750 mAh g−1) in ambient air.

Solid-state electrolytes (SSEs) are essential materials in all-solid-state lithium-metal batteries. However, a comprehensive SSE possessing high ionic conductivity, broad electrochemical window, and high thermal stability remains elusive. In this work, a novel bi-phase SSE featuring a shape memory effect is developed by in-situ thermal cross-linking of 2-ethyl cyanoacrylate (CA), polyethylene glycol methyl ether acrylate (PEGMEA), succinonitrile (SN), and fluoroethylene carbonate (FEC) additives. Due to the phase separation phenomenon and interfacial Li-ion conduction, the bi-phase SSE exhibits a room-temperature ionic conductivity of 1.9 mS cm−1. Meanwhile, the bi-phase SSE exhibits a high oxidation potential of 4.9 V (vs Li/Li+), and a lithium-ion transference number (tLi+) of 0.56. Coupling with LiNi0.8Co0.1Mn0.1O2(NCM 811) cathode and 11 µm bi-phase SSE, solid-state lithium metal batteries (SSLMBs) demonstrate long-term cycling stability (capacity retention > 92% after 250 cycles), excellent rate performance (126 mA h g−1at 2 C, and high-voltage stability (208 mA h g−1at 4.5 V). This investigation demonstrates the potential of bi-phase SSEs as a promising material for the development of high-performance SSLMBs.

Previously, antibiotic was crucial for aquaculture development, but brought many negative effects. Cinnamaldehyde (Cia) and Astragaluspolysaccharides (Asp), bioactive ingredients from Astragalus membranaceusand Cinnamomum cassia, have been confirmed their benefits to livestock. This is the first study to investigate the impacts of Cia, Asp and their joint-effect on Largemouth bass (Micropterus salmoides) growth, digestion, histomorphology and flesh quality. Fish with average weight of 72.48 ± 6.81g were divided into 5 groups, fed with basal feed (M0); supplemented with 1g Cia/kg diet (C1); 1.2g Asp/kg (A1); compatibility of 1g Cia and 1.2g Asp/kg (CA1); 1g Cia and 2g Asp/kg (CA2) for 65-day. The results showed that growth, condition factor (CF) and survival rate (SR) were significantly improved in adding-groups. Especially, the greatest CF, SR, higher feed intake and conversion rate, apparent dry matter digestibility were all measured in CA1 group. The CA1 M. salmoidesalso exhibited higher triglyceride, aspartate aminotransferase, alanine aminotransferase and low-density lipoprotein cholesterol contents, while total-cholesterol and high-density lipoprotein cholesterol resulting in fat deposition descended in CA1 group. The activity of digestive enzymes markedly strengthened in A1 and CA1 treatments (P< 0.05). It is consistent with stronger digestive ability, the thinner muscle layers, longer villus, thicker columnar epithelium and lamina propria were found in CA1 and A1 groups. In addition, supplemented Asp was helpful to enhance antioxidant capacity of M. salmoidesmuscle, whilst reducing the malondialdehyde and lipid-peroxide. The nutritional composition was best in the CA1 fillets, richer in protein, least ash and fat. The histological characteristics were improved in CA1 muscles, which is the most resilient. However, most of above indices inhibited in CA2 group, particularly, the intestinal and liver damages occurred. On balance, the supplement with best aquaculture effects is CA1: 1 g Cia+1.2 g Asp/kg diet.

High energy density and high safety are incompatible with each other in a lithium battery, which challenges today's energy storage and power applications. Ni-rich layered transition metal oxides (NMCs) have been identified as the primary cathode candidate for powering next-generation electric vehicles and have been extensively studied in the last two decades, leading to the fast growth of their market share, including both polycrystalline and single-crystal NMC cathodes. Single-crystal NMCs appear to be superior to polycrystalline NMCs, especially at low Ni content (≤60%). However, Ni-rich single-crystal NMC cathodes experience even faster capacity decay than polycrystalline NMC cathodes, rendering them unsuitable for practical application. Accordingly, this work will systematically review the attenuation mechanism of single-crystal NMCs and generate fresh insights into valuable research pathways. This perspective will provide a direction for the development of Ni-rich single-crystal NMC cathodes.Utilization of single-crystal Ni-rich NMC cathodes for high energy density lithium batteries poses significant challenges in terms of performances and safety, yet there exists ample room to address the concerns.

The low performance of palladium (Pd) is a considerable challenge for direct formic acid fuel cells in practical applications. Herein, we develop a simple strategy to synthesize a highly active and durable Pd nanocatalyst encapsulated in ultrathin silica layers with vertically aligned nanochannels covered graphene oxides (Pd/rGO@pSiO2) without blocking active sites by selective deposition. The Pd/rGO@pSiO2catalyst exhibits very high performance for a formic acid oxidation (FAO) reaction compared with the Pd/rGO without protective silica layers and commercial Pd/C catalysts. Pd/rGO@pSiO2shows an FAO activity 3.9 and 3.8 times better than those of Pd/rGO and Pd/C catalysts, respectively. The Pd/rGO@pSiO2catalysts are also almost 6-fold more stable than Pd/C and more than 3-fold more stable than Pd/rGO. The outstanding performance of our encapsulated Pd catalysts can be ascribed to the novel design of nanostructures by selective deposition fabricating ultrasmall Pd nanoparticles encapsulated in ultrathin silica layers with vertically aligned nanochannels, which not only avoid blocking the active sites but also facilitate the mass transfer in encapsulated catalysts. Our work indicates an important method to the rational design of high-performance catalysts for fuel cells in practical applications.

Superoxide-based Na–O2batteries have attracted extensive research attention because of their high theoretical energy density and energy efficiency. However, the poor cycling performance caused by O2/O2–crossover and the uncontrollable Na dendrite growth severely hinder their practical applications. Addressing these issues comprehensively, we successfully developed a hybrid solid-state (HSS) Na–O2battery based on solid-state electrolyte (SSE) and a protected Na anode. The dense structure of SSE effectively suppressed the O2/O2–crossover, thus mitigating the Na degradation and improving the cell reversibility. Solid electrolyte interphase formation on the Na anode in relation to the O2/O2–crossover was further revealed. Additionally, a three-dimensional protection layer on the Na anode facilitated uniform Na deposition within the conductive matrix. Consequently, the fabricated HSS Na–O2battery demonstrated stable cycling for over 160 cycles at 0.2 mA cm–2under the shallow cycling mode. Our results evidently emphasized the critical role of Na anode protection and the importance of O2/O2–blockage for safe and high-performance Na–O2batteries.