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Abstract: Sodium borohydride, NaBH4, was successfully synthesized via solid-state reaction under Ar instead of H2 atmosphere. A 4NaH–NaBO2–2SiO2 ternary mixture was first ball-milled and pressed into pellet, and then calcined under Ar atmosphere at 480°C for 5h. NaBH4 was obtained in 32% yield when the pressing pressure was up to 30MPa. The influence of the pressing pressure on the solid-state reaction was studied; a plausible reaction pathway and the role of the added SiO2 were discussed. [Copyright &y& Elsevier]

The structural characteristics of TiMn1.5Vx (x = 0.1–0.5) alloys and the hysteresis phenomenon in the TiMn1.5Vx-H2 system have been studied. The TiMn1.5Vx alloy consists mainly of the C14 Laves phase plus some of the BCC solid solution phase, depending on x. The lattice parameters of the C14 Laves phase increase slightly as x increases from 0.1 to 0.2 but are invariant with a further increase in x up to 0.3–0.5. The pressure-composition isotherms clearly show a pressure hysteresis in the TiMn1.5Vx-H2 system which decreases with an increase in the x value mainly due to the equilibrium pressure change for hydride formation. The free energy loss during hydride formation is related to not only the volume expansion, but also the elastic strain in the TiMn1.5Vx alloy itself, that is, prior to hydrogen absorption. [ABSTRACT FROM AUTHOR]

The practical implementation of Li metal anode has long been hindered by the significant challenges of notorious dendritic Li growth and severe interphase instability during repeated cycling. Herein, a highly lithiophilic NiSe‐modified host has rationally been constructed to stabilize Li metal by the facile mechanical rolling strategy. The in situ configurated high‐flux Li2Se‐enriched interphase layer can facilitate the fast interfacial charge transfer, high Li plating/stripping reversibility and homogeneous Li nucleation/growth. Consequently, the achieved modified Li metal demonstrates ultrahigh rate capability (10 mA cm−2) and ultralong‐term cycling stability (6600 cycles) with dendrite‐free Li deposition. The Li|LiFePO4 (LFP) cell exhibits an extraordinarily long lifespan cycling stability over 500 cycles with an ultra‐low decay rate of only ≈0.0092% per cycle at 1 C. Furthermore, the 4.5 V high‐voltage Li|LiCoO2 pouch cell with a high areal capacity (≈1.9 mAh cm−2) still reveals an impressively prolonged cyclability over 200 cycles even under the harsh test condition of low negative‐to‐positive‐capacity (N/P) ratio of ≈3.4 and lean electrolyte of ≈5.5 µL mAh−1. This work provides a facile and scalable strategy toward a highly stable Li metal anode for reliable practical usage. [ABSTRACT FROM AUTHOR]

The O3‐type NaNi0.5Mn0.5O2 (NM) layered cathode in sodium ion batteries (SIBs) undergoes structural distortion and capacity degradation during cycling, which seriously hinders its practical application. Herein, lanthanum (La) is employed as a dopant in O3‐NaNi0.5Mn0.5‐xLaxO2 (NML) cathodes, which triggered an “atomic knife” effect, reducing particle size, and stabilizing crystal structure. The larger La ions generated structural strain during grain growth at high temperatures, hindering the movement of grain boundaries and refining the size of NML particles. Comprehensive characterizations illuminated La doping‐induced atomic site occupancy and phase transformations within NML. A competitive phase formation between layered NML and perovskite LaMnO3 (LMO) is observed. Spontaneously formed perovskite LMO provides surface protection. Moreover, strong La─O bonds expand the Na interlayer spacing, enhancing Na+‐ion diffusion. Consequently, NML cathodes exhibit superior long‐term cycling stability and ultrahigh rate capacities compared to pristine NM cathode and most currently reported layered cathodes for SIBs. [ABSTRACT FROM AUTHOR]

Solid electrolytes with high Li-ion conductivity and electrochemical stability are very important for developing high-performance all-solid-state batteries. In this work, Li2(BH4)(NH2) is nanoconfined in the mesoporous silica molecule sieve (SBA-15) using a melting–infiltration approach. This electrolyte exhibits excellent Li-ion conduction properties, achieving a Li-ion conductivity of 5.0 × 10−3 S cm−1 at 55 °C, an electrochemical stability window of 0 to 3.2 V and a Li-ion transference number of 0.97. In addition, this electrolyte can enable the stable cycling of Li|Li2(BH4)(NH2)@SBA-15|TiS2 cells, which exhibit a reversible specific capacity of 150 mAh g−1 with a Coulombic efficiency of 96% after 55 cycles. [ABSTRACT FROM AUTHOR]

Potassium‐ion battery (PIB) is a potential low‐cost energy storage technology owing to the abundant source and wide distribution of potassium element. However, the PIB usually suffers from poor cycling and rate performance induced by volume expansion and sluggish potassiation kinetics. Herein, multichannel carbon fibers (MCCFs) are rationally constructed as freestanding PIB anodes by electrospinning suitable ratio of poly(methyl methacrylate)/polyacrylonitrile with subsequent calcination treatment. The MCCF electrode shows a high reversible capacity/charge capacity of 420.1/304.2 mAh g−1 at current density of 50 mA g−1 and delivers a capacity of 110.9 mAh g−1 over 2000 cycles at a higher current density of 2000 mA g−1. The excellent electrochemical performance is attributed to the unique multichannels in amorphous MCCFs for buffering volume change and facilitating electrolyte infiltration, as well as high conductivity of N‐, O‐doping in MCCFs. This strategy of fabricating multifunctional electrode materials provides an effective approach to develop high‐performance materials for cost‐effective alkali‐ion batteries. [ABSTRACT FROM AUTHOR]

Ion‐insertion capacitors show promise to bridge the gap between supercapacitors of high power densities and batteries of high energy densities. While research efforts have primarily focused on Li+‐based capacitors (LICs), Na+‐based capacitors (SICs) are theoretically cheaper and more sustainable. Owing to the larger size of Na+ compared to Li+, finding high‐rate anode materials for SICs has been challenging. Herein, an SIC anode architecture is reported consisting of TiO2 nanoparticles anchored on a sheared‐carbon nanotubes backbone (TiO2/SCNT). The SCNT architecture provides advantages over other carbon architectures commonly used, such as reduced graphene oxide and CNT. In a half‐cell, the TiO2/SCNT electrode shows a capacity of 267 mAh g−1 at a 1 C charge/discharge rate and a capacity of 136 mAh g−1 at 10 C while maintaining 87% of initial capacity over 1000 cycles. When combined with activated carbon (AC) in a full cell, an energy density and power density of 54.9 Wh kg−1 and 1410 W kg−1, respectively, are achieved while retaining a 90% capacity retention over 5000 cycles. The favorable rate capability, energy and power density, and durability of the electrode is attributed to the enhanced electronic and Na+ conductivity of the TiO2/SCNT architecture. [ABSTRACT FROM AUTHOR]

Utilization of thin Li metal is the ultimate pathway to achieving practical high‐energy‐density Li metal batteries (LMBs), but its practical implementation has been significantly impeded by formidable challenges of poor thinning processability, severe interphase instability and notorious dendritic Li growth. Here we report a practical thin (10–40 μm) Li/Mo/Li2Se with concurrently modulated interphase and mechanical properties, achieved via a scalable mechanical rolling process. The in situ generated Li2Se and Mo not only enhance the mechanical strength enabling the scalable fabrication of thin Li metal, but also promote homogeneous Li electrodeposition. Significantly, the Li/Mo/Li2Se demonstrates ultrahigh‐rate performance (15 mA cm−2) and ultralong‐lifespan cycling sustainability (2700 cycles) with exceptional anti‐pulverization capability. The Li|LiFePO4 cells show substantially prolonged cyclability over 1200 cycles with an ultralow decay rate of ~0.01 % per cycle. Moreover, the Li|LiNi0.8Co0.1Mn0.1O2 pouch cells deliver enhanced cycling stability even under the extremely harsh conditions of low negative‐to‐positive‐capacity (N/P) ratio of ~1.2 and lean electrolyte of ~0.95 g Ah−1, showing an exceptional energy density of 329.2 Wh kg−1. This work sheds light on facile pathway for scalable production of durable thin Li metal anode toward reliable practicability. [ABSTRACT FROM AUTHOR]

The practical usage of Na metal anode is severely prohibited by the instability of the natively formed solid electrolyte interface (SEI) layer and the uncontrollable Na dendrite growth, inducing short cycle life and serious safety concerns. Herein, phosphorylated covalent organic frameworks (P‐COF) is first synthesized and rationally used to construct the robust artificial interface layer for Na metal stabilization. The modified Na metal anode demonstrates high rate performance (5 mA cm−2) and ultralong cycling lifespan (1800 h) with dendrite‐free Na deposition in carbonate‐based electrolyte. And the assembled Na|Na3V2(PO4)3 (NVP) cell also reveals extraordinarily stable cycling at 5 C for 4000 cycles with a quite low decay rate of 0.002% per cycle. Moreover, the Na|NVP full cell with high areal capacity (2.0 mAh cm−2) and thin Na metal (30 µm) still demonstrates prolonged cycling over 500 cycles even under the harsh condition of a low negative‐to‐positive‐capacity (N/P) ratio of 2:3. Furthermore, the Na|NVP pouch cell with an ultrathick cathode (≈17 mg cm−2) also manifests significantly prolonged cycling performance. This work demonstrates a facile and effective strategy toward reliable Na metal batteries. [ABSTRACT FROM AUTHOR]

The practical application of sodium (Na) metal anode has been seriously hindered by the uncontrolled Na dendrite growth and severe volume expansion inducing short battery lifespan and safety concerns. Here, highly sodiophilic and ultrafine ZnS‐modified carbon fibers have been rationally constructed as a scaffold to obviate these drawbacks. The in situ generated Na2S‐reinforced fast ion transport interphase and the effective space confinement synergistically facilitate the fast sodium ion interfacial transfer and the homogeneous and dendrite‐free Na deposition, thus enabling high‐rate and dendrite‐free Na metal anode. The modified Na metal demonstrates ultrahigh rate capability (15 mA cm−2) and ultralong cycling life (5300 cycles). Moreover, the Na|Na3V2(PO4)3 (NVP) cell delivers ultrahigh rate capability (80 C) and extraordinarily ultralong lifespan cycling durability (2980 cycles). The Na|NVP pouch cell also exhibits an extraordinarily ultralong‐term cycle life of over 1070 cycles with an extremely low capacity decay rate of 0.0088% per cycle at 10 C. This work provides a facile and efficient strategy to propel the Na metal anode towards practicability. [ABSTRACT FROM AUTHOR]

The practical utilization of Li metal anodes has been significantly plagued by the challenges of uncontrollable dendritic Li growth and poor interphase instability. Here, the study reports a novel strategy to strengthen interphase and give highly efficient active seeds concurrently to stabilize Li metal via a highly lithiophilic In2O3 decorated porous scaffold. In situ configurated fast‐ion‐transport Li2O‐strengthened interphase layer cooperatively with highly efficient Li13In3 nucleation induction can endow the uniform Li nucleation/growth and high Li utilization efficiency. As a result, the achieved modified Li metal manifests high Coulombic efficiency, ultrahigh rate performance (5 mA cm−2), and ultra‐long lifespan cycling durability (7975 cycles). Importantly, the established Li|LiFePO4 cells exhibit long‐term cycling durability over 600 cycles at 1 C with an ultralow decay rate of ca. 0.017% per cycle. Moreover, the Li|LiCoO2 pouch cells with ultrahigh areal capacity of ca. 3.89 mAh cm−2 also exhibit extraordinarily prolonged cycling performance with excellent capacity retention despite extremely harsh cycling conditions of low negative‐to‐positive‐capacity (N/P) ratio of ca. 1.7 and lean electrolyte of ca. 4.9 g Ah−1. This work enlightens a facile and effective avenue toward highly stable Li metal anode toward reliable practicability. [ABSTRACT FROM AUTHOR]

All‐solid‐state Na‐ion batteries are considered to be one of the most promising candidates for large‐scale applications at low‐cost. Hydride electrolytes have been pursued as a research hotspot more recently, owing to their high Na‐ion conductivities, while there is an urgent need to address their electrochemical stabilities in order to meet the requirements for applications in Na batteries. Herein, a novel and universal strategy is proposed to improve the electrochemical stabilities of hydride electrolytes, which takes advantage of the in situ reactions between hydrides and NaHF2. As a representative example, Na2B12H12 can react with NaHF2 to form NaF nanoparticles that are uniformly embedded in the Na2B12H11F matrix, which exhibits superior electrode compatibilities without apparent reduction in conductivity. The symmetrical Na cell thus derived shows a long‐term cycling and the quasi‐symmetrical Na3V2(PO4)3 cell shows high Coulombic efficiency. They give rise to a stable cycling of the Na||Na3V2(PO4)3 all‐solid‐state batteries with a capacity retention of 87.7% after 100 cycles, which can be attributed to the stabilization of electrolyte/electrode interfaces by the F‐enriched interphases. Beyond Na batteries, the present study sheds timely new light on the development of hydride electrolytes for other long‐waited applications. [ABSTRACT FROM AUTHOR]

Boosting the ultralow temperature (below −30 °C) performance of Na‐ion hybrid capacitors (SIHCs), which integrate the high energy density of batteries with the high output power and long life of supercapacitors, is critical for the application of advanced electronics in extreme environments. However, their low‐temperature performance, especially fast charging capability, is hindered by difficult desolvation and slow pass solid electrolyte interphase (SEI) together with sluggish diffusion within the electrode. Herein, a "single‐solute–single‐solvent" electrolyte is developed and a through‐hole hollow carbon sphere (TH‐HCS) is constructed, and it is demonstrated through theoretical calculations and experimental investigations that the weakly solvated structure and high ionic conductivity facilitate the Na+ transportation at low temperatures, the highly fluorinated SEI facilitates the Na+ migration, and the through‐hole hollow structure alleviates the volume expansion during sodiation, thus ensuring fast kinetics and structural stability. As expected, TH‐HCS using this electrolyte exhibits a high specific capacity of 87.5 mAh g−1 after 11 000 cycles at 1.0 A g−1 and −40 °C. Coupled with activated carbon, the assembled SIHC displays an energy density of 106.1 and 52.0 Wh kg−1 at 25 and −40 °C, respectively, far exceeding the performance of commercial energy storage systems at low temperature. [ABSTRACT FROM AUTHOR]

A new Fe-substituted TiFeNb10O29−δ (TFNO) anode is proposed. TFNO possesses a defective and polycrystalline ReO3 Roth–Wadsley shear structure with a slightly larger lattice volume. Electrochemical behavior results and density functional theory (DFT) calculations show that TFNO can facilitate the kinetics of electron/Li+ transportation and demonstrates pseudocapacitive behavior. Consequently, TFNO exhibits superior high rate capacity and cycling stability compared to pristine TNO, offering 100 mA h g−1 at an ultrahigh rate of 50C and a high capacity retention of 86.7% over 1000 cycles at 10C. This work reveals that TFNO could be a promising anode material for fast-charging, stable, and safe LIBs. [ABSTRACT FROM AUTHOR]

• An Fe single atom catalyst with abundant carbon vacancies (Fe-NNC V) is synthesized via adsorption-pyrolysis method. • The defect enriched Fe-NNC V single atom catalyst exhibits a high half wave potential of 0.924 V in alkaline medium. • The flexible solid-state zinc-air batteries assembled with Fe-NNC V display great cycling stability and foldability. Single-atom catalysts (SACs) have garnered significant interest as promising alternatives for enhancing the oxygen reduction reaction (ORR) in metal-air batteries. However, the rational design and facile synthesis of the highly selective SACs are still of great challenges. Herein, we successfully designed a Fe-N 4 -C SAC implanted in nitrogen-doped nano-carbon substrates with abundant carbon vacancies (Fe-NNC V) through a 'post adsorption-secondary pyrolysis' strategy assisted with melamine-etching, which achieves an asymmetric electronic structure and an optimized d band center. Additionally, the Fe-NNC V SAC exhibits a superior ORR activity with a high half wave potential of 0.924 V and a large diffusion-limiting current density of 5.7 mA cm−2. The aqueous rechargeable zinc-air battery (ZAB) assembled with Fe-NNC V SAC displays a high power-density of 99.1 mW cm−2 and a long-term durability over 310 h. Furthermore, flexible solid-state ZABs based on Fe-NNC V SAC are successfully assembled showing good cycling stability and foldability with high energy efficiency both at room and low temperature. This work provides insights into the optimization of electronic structure of transition metal SACs through defect engineering to achieve high ORR activities and to promote the applications of metal-air batteries. [ABSTRACT FROM AUTHOR]

Highly conducting CNT/polyaniline hybrids were prepared by plasma-induced graft polymerization, i.e., plasma pretreatment of CNTs and further in situ polymerization of aniline. Plasma pretreatment made more aniline grafted on the CNTs' surface by the role of oxygen radicals. SEM images showed that the surfaces of CNTs were uniformly coated by PANI. FTIR showed that there was presence of strong interaction between CNTs and PANI molecular chains. The conductivity of CNT/PANI hybrids with plasma treatment is higher than that of CNT/PANI hybrids without plasma pretreatment (0.443 S/cm at 0 W) or pretreated by acid oxidation method. Importantly, the microwave absorption properties were investigated by measuring complex permeability, complex permittivity and reflection loss in a frequency of 2-18 GHz. The microwave absorption enhancement of CNT/PANI hybrids results mainly from dielectric loss rather than magnetic loss due to higher value of dielectric loss. [ABSTRACT FROM AUTHOR]

With the development of society, sodium‐ion batteries (SIBs) attract more and more attention and are expected to be the next generation of daily energy storage devices. Among the previously reported cathode materials for SIBs, the layered transition metal oxides are considered to be the most competitive cathode materials due to their high specific capacities, simple synthesis process, and many similar advantages to the successful Li transition metal oxides in lithium‐ion batteries (LIBs). This review summarizes the recent progress of layered transition metal oxide cathode materials for SIBs, which mainly include Mn‐based, Ni/Mn‐based, Ni/Co/Mn‐based, and Ni/Fe/Mn‐based layered cathode materials. The remaining challenges and future developments for the layered transition metal oxide cathode materials are also discussed. This review is expected to provide some insights into the development of layered transition metal oxide cathodes for high‐performance SIBs. [ABSTRACT FROM AUTHOR]

Transition metal (TM) single atomic catalysts (MSAC-N-C) derived from doped zeolite imidazolate frameworks (ZIF-8) are considered attractive oxygen reduction reaction (ORR) catalysts for fuel cells and metal-air batteries due to their advantages of high specific surface area, more active catalytic sites, adjustable pore size, and coordination topology features. This review provides an updated overview of the latest advances of MSAC-N-C catalysts derived from ZIF-8 precursors in ORR electrocatalysis. Particularly, some key challenges, including coordination environments regulation of catalysis center in MSAC-N-C, the active sites loading optimization and synergistic effects between TM nanoclusters/nanoparticles and the single atoms on MSAC-N-C catalysis activity, as well as their adaptability in various devices, are summarized for improving future development and application of MSAC-N-C catalysts. In addition, this review puts forward future research directions, making it play a better role in ORR catalysis for fuel cells and metal air batteries. [ABSTRACT FROM AUTHOR]

Li metal is considered as one of the most promising candidates for constructing advanced high‐energy energy storage due to its ultrahigh theoretical capacity and lowest electrochemical potential. However, its practical commercialization is seriously hindered by the challenges of Li dendrite growth, low Coulombic efficiency, and huge volumetric variation. Herein, an efficient in situ generated Li2S‐rich interface layer joint with preplanted Sb nano active sites in hosted Li metal anode is easily achieved with the nanosized Sb2S3 decorated carbonaceous network. The yielded CC@Sb2S3@Li anode demonstrates uniform Li deposition, high Coulombic efficiency, and alleviated volumetric variation. Therefore, the Li symmetric cells show ultralong lifespan stable cycling over 3200 cycles with a very low voltage hysteresis (≈18 mV) at 5 mA cm−2. Impressively, the Li|LiFePO4 full cell delivers an exceptionally prolonged cycling over 180 cycles with a superior capacity retention as high as ≈90% even under the harsh condition of an extremely low negative to positive capacity ratio of ≈0.44 with lean electrolyte (4.4 µL mAh−1). Moreover, the Li|LiNi0.5Co0.2Mn0.3O2 full cell also maintains an excellent cycling performance under the more realistic harsh conditions. This work provides a new avenue and significant step paving the Li metal toward the practical application. [ABSTRACT FROM AUTHOR]

An LaMg2Ni alloy film was prepared by electron beam evaporation plus annealing. Upon hydrogen loading/unloading, the film shows the reversible conversion from a metallic, reflecting state to a semiconducting, color-neutral transparent one. The contrast ratio of the resistivity between two states is over four orders of magnitude. The lower reflection in the dehydrogenated film is attributed to the rough surface originated from the previous hydrogenation. [Copyright &y& Elsevier]

Abstract: Structure stability of RNi3 and RY2Ni9 (R=La, Ce) during cycling of hydrogen absorption/desorption was investigated by both solid-H2 reaction and electrochemical measurements, in order to understand the mechanism responsible for the poor reversibility, and to reveal the differences between RNi3 and RY2Ni9 compounds. It has been found that, all of the cycled RNi3 and RY2Ni9 were subject to partial amorphization. This hydrogen-induced amorphization (HIA) occurred immediately in LaNi3, but proceeded gradually in CeNi3, LaY2Ni9 and CeY2Ni9. The HIA in these compounds is attributed to the RM2 subunits in their crystal structures. [Copyright &y& Elsevier]

[Display omitted] Ti 2 Nb 10 O 29 (TNO) is a suitable electrode for high-performance lithium-ion batteries and capacitors because of its large lithium storage capacity and high Li+ diffusivity. Currently, the rate or power capability of TNO-based systems is limited by the poor electronic conductivity of the material. Here we report our findings in design, synthesis, and characterization of a hierarchical N-rich carbon conductive layer wrapped TNO structure (TNO@NC) using a novel polypyrrole-chemical vapor deposition (PPy-CVD) process. It was found that carbon coating with PPy–carbon partially reduces Ti and Nb cations, forms TiN, and creates oxygen vacancies in the TNO@NC structure that further increase overall electronic and ionic conductivity. Various defect models and density functional theory (DFT) calculations are used to show how oxygen vacancies influence the electronic structure and Li-ion diffusion energy of the TNO@NC composite. The optimized TNO@NC sample shows notable rate capability in half-cells with a reversible capacity of 300 mAh g−1 at 1 C rate and maintains 211 mAh g−1 at a rate of 100 C, which is superior to that of most M x Nb y O z materials. Full cell LiNi 0.5 Mn 1.5 O 4 (LNMO)||TNO@NC lithium-ion batteries (LIB) and active carbon (AC)||TNO@NC hybrid lithium-ion capacitors (LIC) exhibited notable volumetric and gravimetric energy and power densities. [ABSTRACT FROM AUTHOR]

La 2 O 3 nanocoating endows LiNi 0.5 Mn 1.5 O 4 with a stable structure, thin SEI layers and fast lithium ions diffusion, boosting the lithium ion storage performance. • The cycling performance of LiNi 0.5 Mn 1.5 O 4 is highly enhanced by La 2 O 3 coating. • Voltage fade is introduced to evaluate the voltage stability of LiNi 0.5 Mn 1.5 O 4. • The effects of La 2 O 3 coating contents are systematically investigated. • The modified LiNi 0.5 Mn 1.5 O 4 possess a stable structure, thin SEI layers and fast lithium ions diffusion. In this work, a conformally interfacial nanocoating strategy is introduced to enhance the lithium ion storage performance of LiNi 0.5 Mn 1.5 O 4 (LNMO). Stable cycling of LNMO is achieved through La 2 O 3 coating at both room and elevated temperatures. A series of La 2 O 3 -coated LNMO composites with various coating contents ranging from 0 to 3 wt% is prepared, and their electrochemical behaviors are systematically investigated. Among them, the 2 wt% La 2 O 3 -coated LNMO cathode presents the best comprehensive lithium ion storage performance; for instance, it retains more than 75% capacity retention after 500 cycles at room temperature and 93% capacity retention after 50 cycles at an elevated temperature of 55 °C with 1C rate. Moreover, the modified samples show more stable plateau potential than the pristine one during the cycling process. It is believed that the introduction of the La 2 O 3 nanocoating layer can effectively suppress side reactions between electrode and electrolyte, thus maintaining stable structure of electrode material and reducing polarization during cycling. Our work provides an effective approach to improve the electrochemical stability of LNMO high-potential cathode for future large-scale applications of enhanced lithium ion batteries with high energy density and long cycle life. [ABSTRACT FROM AUTHOR]