Ultra-Thin Hydrogen-Organic-Framework (HOF) Nanosheets for Ultra-Stable Alkali Ions Battery Storage.

Organic frameworks-based batteries with excellent physicochemical stability and long-term high capacity will definitely reduce the cost, carbon emissions, and metal consumption and contamination. Here, an ultra-stable and ultra-thin perylene-dicyandiamide-based hydrogen organic framework (HOF) nanosheet (P-DCD) of ≈3.5 nm in thickness is developed. When applied in the cathode, the P-DCD exhibits exceptional long-term capacity retention for alkali-ion batteries (AIBs). Strikingly, for lithium-ion batteries (LIBs), at current of 2 A g-1, the large reversible capacity of 108 mA h g-1 shows no attenuation within 5 000 cycles. For sodium-ion batteries (SIBs), the related capacity retains 91.7% within 10 000 cycles compared to the initial state, significantly much more stable than conventional organic materials reported previously. Mechanism studies through ex situ and in situ experiments and theoretical density functional theory (DFT) calculations reveal that the impressive long-term performance retention originates from the large electron delocalization, fast ion diffusion, and physicochemical stability within the ultra-thin 2D P-DCD, featuring π-π and hydrogen bonding stacking, nitrogen-rich units, and low impedance. The advantageous features demonstrate that rationally designed stable and effective organic frameworks pave the way to utilizing complete organic materials for developing next-generation low-cost and highly stable energy storage batteries.

Coupled Ni─Co Dual-Atom Catalyst for Guiding Sulfur and Lithium Evolutions in Lithium-Sulfur Batteries.

The kinetically retarded sulfur evolution reactions and notorious lithium dendrites as the major obstacles hamper the practical implementation of lithium-sulfur batteries (LSBs). Dual metal atom catalysts as a new model are expected to show higher activity by their rational coupling. Herein, the dual-atom catalyst with coupled Ni─Co atom pairs (Ni/Co-DAC) is designed successfully by programmed approaches. The Ni─Co atom pairs alter the local electron structure and optimize the coordination configuration of Ni/Co-DAC, leading to the coupling effect for promoting the interconversion of sulfur and guiding lithium plating/striping. The LSB delivers a remarkable capacity of 818 mA h g-1 at 3.0 C and a low degeneration rate of 0.053% per cycle over 500 cycles. Moreover, the LSB with a high sulfur mass loading of 6.1 mg cm-2 and lean electrolyte dosage of 6.0 µL mgS -1 shows a remarkable areal capacity of 5.7 mA h cm-2.

Molybdenum Atom Engineered Vanadium Disulfide for Boosted High-Capacity Li-Ion Storage.

A drawback with lithium-ion batteries (LIBs) lies in the unstable lithium storage which results in poor electrochemical performance. Therefore, it's of importance to improve the electrochemical functionality and Li-ion transport kinetics of electrode materials for high-performance lithium storage. Here, a subtle atom engineering via injecting molybdenum (Mo) atoms into vanadium disulfide (VS2 ) to boost high capacity Li-ion storage is reported. By combining operando, ex situ monitoring and theoretical simulation, it is confirmed that the 5.0%Mo atoms impart flower-like VS2 with expanded interplanar spacing, lowered Li-ion diffusion energy barrier, and increased Li-ion adsorption property, together with enhanced e- conductivity, to boost Li-ion migration. A "speculatively" optimized 5.0% Mo-VS2 cathode that exhibits a specific capacity of 260.8 mA h g-1 at 1.0 A g-1 together with a low decay of 0.009% per cycle over 500 cycles is demonstrated. It is shown that this value is ≈1.5 times compared with that for bare VS2 cathode. This investigation has substantiated the Mo atom doping can effectively guide the Li-ion storage and open new frontiers for exploiting high-performance transition metal dichalcogenides for LIBs.

Confine, Defect, and Interface Manipulation of Fe3 Se4 /3D Graphene Targeting Fast and Stable Potassium-Ion Storage.

The fast electrochemical kinetics behavior and long cycling life have been the goals in developing anode materials for potassium ion batteries (PIBs). On account of high electron conductivity and theoretical capacity, transition metal selenides have been deemed as one of the promising anode materials for PIBs. Herein, a systematic structural manipulation strategy, pertaining to the confine of Fe3 Se4 particles by 3D graphene and the dual phosphorus (P) doping to the Fe3 Se4 /3DG (DP-Fe3 Se4 /3DG), has been proposed to fulfill the efficient potassium-ion (K-ion) evolution kinetics and thus boost the K-ion storage performance. The theoretical calculation results demonstrate that the well-designed dual P doping interface can effectively promote K-ion adsorption behavior and provide a low energy barrier for K-ion diffusion. The insertion-conversion and adsorption mechanism for multi potassium storage behavior in DP-Fe3 Se4 /3DG composite has been also deciphered by combining the in situ/ex situ X-ray diffraction and operando Raman spectra evidences. As expected, the DP-Fe3 Se4 /3DG anode exhibits superior rate capability (120.2 mA h g-1 at 10 A g-1 ) and outstanding cycling performance (157.9 mA h g-1 after 1000 cycles at 5 A g-1 ).

Phosphorization Engineering on Metal-Organic Frameworks for Quasi-Solid-State Asymmetry Supercapacitors.

Porous carbon and metal oxides/sulfides prepared by using metal-organic frameworks (MOFs) as the precursors have been widely applied to the realm of supercapacitors. However, employing MOF-derived metal phosphides as positive and negative electrode materials for supercapacitors has scarcely been reported thus far. Herein, two types of MOFs are used as the precursors to prepare CoP and FeP4 nanocubes through a two-step controllable heat treatment process. Due to the advantages of composition and structure, the specific capacitances of FeP4 and CoP nanocubes reach 345 and 600 F g-1 at the current density of 1 A g-1 , respectively. Moreover, a quasi-solid-state asymmetric supercapacitor is assembled based on charge matching principle by employing CoP and FeP4 nanocubes as the positive and negative electrodes, respectively, which exhibits a high energy density of 46.38 Wh kg-1 at the power density of 695 W kg-1 . Furthermore, a solar-charging power system is assembled by combining the quasi-solid-state asymmetric supercapacitor and monocrystalline silicon plates, substantiating that the device can power the toy electric fan. This work paves a practical way toward the rational design of quasi-solid-state asymmetry supercapacitors systems affording favorable energy density and long lifespan.

Recent progress in the tailored growth of two-dimensional hexagonal boron nitride via chemical vapour deposition.

Recent years have witnessed many advances in two-dimensional (2D) hexagonal boron nitride (h-BN) materials in both fundamental research and practical applications. This has ultimately been inspired by the unique electrical and optical properties, as well as the excellent thermal and chemical stability of h-BN. However, controllable and scalable preparation of 2D h-BN materials has been challenging. Very recently, the chemical vapour deposition (CVD) technique has shown great promise for achieving high-quality h-BN samples with excellent layer-number selectivity and large-area uniformity, considerably contributing to the latest advancements of 2D material research. In this tutorial review, we provide a systematic summary of the state-of-the-art in the tailored production of 2D h-BN on various substrates by virtue of CVD routes.

Structure and Properties of Reduced Graphene Oxide/Natural Rubber Latex Nanocomposites.

In this work, the morphology and properties of graphene modified natural rubber (NR) was studied. Graphite oxide was chemically reduced with poly(sodium 4-styrenesulfonate) as a stabilizer, then the obtained graphene was blended with NR using latex technique. It is observed that a stable graphene suspension was fabricated by chemical reduction of graphite oxide in the presence of surfactant, while graphene was dispersed homogeneous in NR matrix as tested by WAXD and TEM. Dynamic mechanical analysis showed that storage modulus enhanced dramatically after the incorporation of graphene due to the high surface area of graphene and the exfoliated structure of graphene in NR. The electrical property and thermal conductive properties of NR/graphene nanocomposites improved significantly following the increase in graphene concentration.

Locally boosted Li2S nucleation on VO2 by loading carbon quantum dots for soft-packaged lithium-sulfur pouch cells.

VO2 affords ultrafast polysulfide adsorption on account of its oxidation potential, which matches the sulfur working window (1.7-2.8 V). Nevertheless, its nonconductive surface limits direct sulfur conversion. Herein, we gently load carbon quantum dots on VO2 to increase direct Li2S nucleation by enhanced electron conductivity. As a result, the soft-packaged lithium-sulfur pouch cell yields a capacity retention of 88.8% at 0.5C after 100 cycles and a decay rate of 0.17% per cycle over 200 cycles at 2C. The cell energy density of the multilayer cell is up to 386.1 W h kg-1.

Pre-carbonized nickel-metal organic frameworks to enable lithium-sulfur reactions.

Metal-organic frameworks, a type of porous architecture, have caught wide attention for their pore-rich and special metal-active centres. However, the non-conductive MOFs show limitations in lithium-sulfur batteries (LSBs). Herein, we first synthesized a lamellar nickel-based MOF and subsequently conducted pre-carbonization to attain a conductive Ni-carbon (Ni@C) catalyst. On account of the retained three-dimensional architecture and elevated conductivity, using Ni@C as the interlayer can realize polysulfide-regulated and kinetically promoted LSBs. This work offers a viable strategy to extend the implementation of MOFs in state-of-the-art LSB systems.

An enhanced electrocatalytic oxygen evolution reaction by the photothermal effect and its induced micro-electric field.

Promoting better thermodynamics and kinetics of electrocatalysts is key to achieving an efficient electrocatalytic oxygen evolution reaction (OER). Utilizing the photothermal effect and micro-electric field of electrocatalysts is a promising approach to promote the sluggish OER. Herein, to reveal the relationship of the photothermal effect and its induced micro-electric field with OER performance, NiSx coupled NiFe(OH)y on nickel foam (NiSx@NiFe(OH)y/NF) is synthesized and subjected to the OER under near-infrared (NIR) light. Owing to the photothermal effect and its induced micro-electric field, the OER performance of NiSx@NiFe(OH)y/NF is significantly enhanced. Compared with no NIR light irradiation, the overpotential at 50 mA cm-2 and the Tafel slope of NiSx@NiFe(OH)y/NF under NIR light irradiation were 234.1 mV and 38.0 mV dec-1, which were lower by 12.4 mV and 7.1 mV dec-1, and it exhibited stable operation at 1.6 V vs. RHE for 8 h with 99% activity maintained. This work presents a novel inspiration to understand the photothermal effect-enhanced electrocatalytic OER.

Advanced core-shell hollow carbon nanofibers for ion and electron accessibility in sodium ion batteries.

One-dimensional core-shell hollow carbon nanofibers (HCNFs) have been synthesized by coaxial electrospinning, deacetylation and carbonization, which exhibit multi-surface properties that enhance electrolyte infiltration and facilitate ion/electron transport. The nitrogen-doped hard carbon outer shell compensates for the low conductivity of amorphous carbon, and the inner core carbon supports the stability of core-shell hollow structures. This unique structure ensures the accessibility of electrons/ions during electrochemical reactions and contributes to the superior rate performance of HCNFs. Ultimately, a high retention rate of 77% of the initial capacity value (0.1 A g-1) was demonstrated at a current density of 2 A g-1. The core-shell hollow structure designed in this work greatly optimizes the sodium transport dynamics.

An Electrolyte Engineered Homonuclear Copper Complex as Homogeneous Catalyst for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries suffer from severe polysulfide shuttle, retarded sulfur conversion kinetics and notorious lithium dendrites, which has curtailed the discharge capacity, cycling lifespan and safety. Engineered catalysts act as a feasible strategy to synchronously manipulate the evolution behaviors of sulfur and lithium species. Herein, a chlorine bridge-enabled binuclear copper complex (Cu-2-T) is in situ synthesized in electrolyte as homogeneous catalyst for rationalizing the Li-S redox reactions. The well-designed Cu-2-T provides completely active sites and sufficient contact for homogeneously guiding the Li2S nucleation/decomposition reactions, and stabilizing the lithium working interface according to the synchrotron radiation X-ray 3D nano-computed tomography, small angle neutron scattering and COMSOL results. Moreover, Cu-2-T with the content of 0.25 wt% approaching saturated concentration in electrolyte further boosts the homogeneous optimization function in really operated Li-S batteries. Accordingly, the capacity retention of the Li-S battery is elevated from 51.4% to 86.3% at 0.2 C, and reaches 77.0% at 1.0 C over 400 cycles. Furthermore, the sulfur cathode with the assistance of Cu-2-T realizes the stable cycling under the practical scenarios of soft-packaged pouch cell and high sulfur loading (6.5 mg cm-2 with the electrolyte usage of 4.5 µL mgS -1).

Chlorine bridge bond-enabled binuclear copper complex for electrocatalyzing lithium-sulfur reactions.

Engineering atom-scale sites are crucial to the mitigation of polysulfide shuttle, promotion of sulfur redox, and regulation of lithium deposition in lithium-sulfur batteries. Herein, a homonuclear copper dual-atom catalyst with a proximal distance of 3.5 Å is developed for lithium-sulfur batteries, wherein two adjacent copper atoms are linked by a pair of symmetrical chlorine bridge bonds. Benefiting from the proximal copper atoms and their unique coordination, the copper dual-atom catalyst with the increased active interface concentration synchronously guide the evolutions of sulfur and lithium species. Such a delicate design breaks through the activity limitation of mononuclear metal center and represents a catalyst concept for lithium-sulfur battery realm. Therefore, a remarkable areal capacity of 7.8 mA h cm-2 is achieved under the scenario of sulfur content of 60 wt.%, mass loading of 7.7 mg cm-2 and electrolyte dosage of 4.8 µL mg-1.

Dual-Functional V2 C MXene Assembly in Facilitating Sulfur Evolution Kinetics and Li-Ion Sieving toward Practical Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as one of the most promising candidates to achieve an energy density of 500 Wh kg⁻1 . However, the challenges of shuttle effect, sluggish sulfur conversion kinetics, and lithium-dendrite growth severely obstruct their practical implementation. Herein, multiscale V2 C MXene (VC) with a spherical confinement structure is designed as a high-efficiency bifunctional promotor for the evolution of sulfur and lithium species in Li-S batteries. Combining synchrotron X-ray 3D nano-computed tomography (X-ray 3D nano-CT), small-angle neutron scattering (SANS), and first-principle calculations, it is revealed that the activity of VC can be maximized by tuning the scale, and the as-attained functions are conducted as follows: (i) the VC acts as the efficient lithium polysulfide (LiPS) scavenger due to the large number of active sites; (ii) the VC exhibits significantly improved electrocatalytic function for the Li2 S nucleation and decomposition reaction kinetics owing to the scale effect; and (iii) the VC can regulate the dynamic behavior of Li-ions and thus stabilize the lithium plating/stripping effectively on account of the unique ion-sieving effect.

Regulation of the surface activity of carbon anodes for rationalization of potassium storage.

The gradient temperature was manipulated to construct hollow irregular carbon spheres with regulated intrinsic defects and surface area targeting favorable potassium storage. An enlarged surface area, increased intrinsic defects, and superior conductivity induced more surface-active interfaces. These actions facilitated a high reversible capacity as well as excellent cycling stability.

Manipulating the Li-S reaction kinetics via the V8C7/phosphorus defect-integrated carbon promoter.

V8C7/phosphorus defect-integrated carbon (VPC) is proposed as a dual-function promoter for Li-S chemistry. The well-dispersed V8C7 and phosphorus defects exhibit ample polar sites and remarkable electron conductivity. Such rational integration of dual active centers simultaneously suppresses the shuttle effect and propels the Li-S redox reaction kinetics. Therefore, the S/VPC cathode shows an initial capacity of 1090.0 mA h g-1 and a high retention of 83.5% at 0.2C after 100 cycles and a low decay rate of 0.076% at 2C over 600 cycles.

Nitrogen Balance on Ni-N-C Promotor for High-Energy Lithium-Sulfur Pouch Cells.

The viability of lithium-sulfur (Li-S) batteries toward real implementation directly correlates with unlocking lithium polysulfide (LiPS) evolution reactions. Along this line, designing promotors with the function of synchronously relieving LiPS shuttle and promoting sulfur conversion is critical. Herein, the nitrogen evolution on hierarchical and atomistic Ni-N-C electrocatalyst, mainly pertaining to the essential subtraction, reservation and coordination of nitrogen atoms, is manipulated to attain favorable Li-S pouch cell performances. Such rational evolution behavior realizes the "nitrogen balance" in simultaneously regulating the Ni-N coordination environment, Ni single atom loading, abundant vacancy defects, active nitrogen and electron conductivity, and maximizing the electrocatalytic activity elevation of Ni-N-C system. With such merit, the cathode harvests favorable performances in a soft-packaged pouch cell prototype even under high sulfur mass loading and lean electrolyte usage. A specific energy density up to 405.1 Wh kg-1 is harvested by the 0.5-Ah-level pouch cell.

A review of size engineering-enabled electrocatalysts for Li-S chemistry.

Li-S batteries (LSBs) have received extensive attention owing to their remarkable theoretical capacity (1672 mA h g-1) and high energy density (2600 W h kg-1), which are far beyond those of the state-of-the-art Li-ion batteries (LIBs). However, the retarded sulfur reaction kinetics and fatal shuttle effect have hindered the practical implementations of LSBs. In response, constructing electrocatalysts for Li-S systems has been considered an effective strategy to date. Particularly, size engineering-enabled electrocatalysts show high activity in the sulfur redox reaction, considerably contributing to the latest advances in Li-S system research. In this tutorial review, we provide a systematic summary of nano- to atomic-scale electrocatalysts employed in Li-S chemistry, aiming at figuring out the working mechanism of size engineering-enabled electrocatalysts in the sulfur redox reaction and guiding the rational construction of advanced LSBs toward practically viable applications.

An in-situ electrodeposited cobalt selenide promotor for polysulfide management targeted stable Lithium-Sulfur batteries.

Lithium-sulfur batteries (LSBs) have attracted much attention due to their high theoretical specific capacity, energy density and low cost. However, the commercial application of LSBs is hindered due to the lithium polysulfide (LiPS) shuttle as well as the sluggish reaction kinetics. Herein, cobalt selenide (Co0.85Se) nanowire arrays have been constructed on a carbon-modified separator by an in-situ electrodeposition technique without any other post-treatments such as coating with other ancillary materials. The introduced three-dimensional (3D) conductive carbon layer comprising of carbon nanotube (CNT) and acetylene black (AB) not only serves as the effective support for Co0.85Se (CS) but also builds a hierarchical structure to promote the e- transfer. The as-obtained CS-CNT/AB presents a strong anchoring effect on LiPSs and high electrocatalytic activity for sulfur reaction kinetics. As a result, the LSBs inserted with electrodeposition-enabled CS modified separator exhibit an outstanding rate capability (1560.4 mAh g-1 at 0.1 C) and relatively low capacity decay of only 0.068% per cycle over 500 cycles at 2.0 C. This study provides a promising strategy to realize the rational construction of high-efficiency and long-life LSBs.

Potassium mediated Co-Fe-based Prussian blue analogue architectures for aqueous potassium-ion storage.

Prussian blue analogs (PBAs) with unique structure show great potential for aqueous potassium-ion batteries (AKIBs). Herein, K2Co[Fe(CN)6] and KNi[Co(CN)6] architectures are developed as the cathode candidates for AKIBs. Moreover, the reaction kinetics detection and DFT calculations are employed to analyse the battery performances.