Multilayer Core-Sheath Wires with Radially Aligned N-Doped Carbon Nanohole Arrays for Boosting Energy Storage in Zinc-Ion Hybrid Supercapacitors.

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) with the characteristics of low cost, long cycle stability, and good safety have been regarded as potential candidates for wearable energy storage applications. Herein, we reasonably designed a unique binder-free nitrogen-doped (N-doped) porous carbon@TiO2@Ti multilayer core-sheath wire (N-CTNT), which has vertical N-doped carbon nanoholes radially aligned on the wire surface. The unique structure and nitrogen dopants of N-CTNTs have facilitated zinc deposition on N-CTNT to form a hierarchical and robust zinc-carbon composite (Zn@N-CTNTs). A wire-shaped ZHSC was constructed with N-CTNTs and Zn@N-CTNTs as cathode and anode electrodes, respectively. The as-prepared ZHSC has an outstanding specific capacitance of 488 mF cm-2 at 1 mA cm-2. This hybrid supercapacitor also exhibits an excellent energy density of 211 µW h cm-2, good rate performance, and long cycle stability with a capacity retention rate of 90.4% after 16,000 cycles.

Interfacial Manipulation via In Situ Constructed Fast Ion Transport Channels toward an Ultrahigh Rate and Practical Li Metal Anode.

The successful substitution of Li metal for the conventional intercalation anode can promote a significant increase in the cell energy density. However, the practical application of the Li metal anode has long been fettered by the unstable solid electrolyte interface (SEI) layer on the Li metal surface and notorious dendritic Li growth. Herein, a stabilized SEI layer with in situ constructed fast ion transport channels has successfully been achieved by a robust In2S3-cemented poly(vinyl alcohol) coating. The modified Li metal demonstrates significantly enhanced Coulombic efficiency, high rate performance (10 mA cm-2), and ultralong life cycling stability (∼4900 cycles). The Li|LiCoO2 (LCO) cell presents an ultralong-term stable operation over 500 cycles at 1 C with an extremely low capacity decay rate (∼0.018% per cycle). And the Li|LCO full cell with the ultrahigh loading cathode (∼25 mg cm-2) and ultrathin Li foil (∼40 µm) also reveals a prolonged cycling performance under the low negative-to-positive capacity ratio of 2.2. Furthermore, the Li|LCO pouch cell with a commercial cathode and ultrathin Li foil still manifests excellent cycling performance even under the harsh conditions of limited Li metal and lean electrolyte. This work provides a cost-effective and scalable strategy toward high performance practical Li metal batteries.

TiFeNb10O29-δ anode for high-power and durable lithium-ion batteries.

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.

In Situ Trapping Strategy Enables a High-Loading Ni Single-Atom Catalyst as a Separator Modifier for a High-Performance Li-S Battery.

The poor electrochemical reaction kinetics of Li polysulfides is a key barrier that prevents the Li-S batteries from widespread applications. Ni single atoms dispersed on carbon matrixes derived from ZIF-8 are a promising type of catalyst for accelerating the conversion of active sulfur species. However, Ni favors a square-planar coordination that can only be doped on the external surface of ZIF-8, leading to a low loading amount of Ni single atoms after pyrolysis. Herein, we demonstrate an in situ trapping strategy to synthesize Ni and melamine-codoped ZIF-8 precursor (Ni-ZIF-8-MA) by simultaneously introducing melamine and Ni during the synthesis of ZIF-8, which can remarkably decrease the particle size of ZIF-8 and further anchor Ni via Ni-N6 coordination. Consequently, a novel high-loading Ni single-atom (3.3 wt %) catalyst implanted in an N-doped nanocarbon matrix (Ni@NNC) is obtained after high-temperature pyrolysis. This catalyst as a separator modifier shows a superior catalytic effect on the electrochemical transitions of Li polysulfides, which endows the corresponding Li-S batteries with a high specific capacity of 1232.4 mA h g-1 at 0.3 C and an excellent rate capability of 814.9 mA h g-1 at 3 C. Furthermore, a superior areal capacity of 4.6 mA h cm-2 with stable cycling over 160 cycles can be achieved under a critical condition with a low electrolyte/sulfur ratio (8.4 µL mg-1) and high sulfur loading (4.85 mg cm-2). The outstanding electrochemical performances can be attributed to the strong adsorption and fast conversion of Li polysulfides on the highly dense active sites of Ni@NNC. This intriguing work provides new inspirations for designing high-loading single-atom catalysts applied in Li-S batteries.

A High-Rate, Durable Cathode for Sodium-Ion Batteries: Sb-Doped O3-Type Ni/Mn-Based Layered Oxides.

O3-Type layered oxides are widely studied as cathodes for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their rate capability and durability are limited by tortuous Na+ diffusion channels and complicated phase evolution during Na+ extraction/insertion. Here we report our findings in unravelling the mechanism for dramatically enhancing the stability and rate capability of O3-NaNi0.5Mn0.5-xSbxO2 (NaNMS) by substitutional Sb doping, which can alter the coordination environment and chemical bonds of the transition metal (TM) ions in the structure, resulting in a more stable structure with wider Na+ transport channels. Furthermore, NaNMS nanoparticles are obtained by surface energy regulation during grain growth. The synergistic effect of Sb doping and nanostructuring greatly reduces the ionic migration energy barrier while increasing the reversibility of the structural evolution during repeated Na+ extraction/insertion. An optimized NaNMS-1 electrode delivers a reversible capacity of 212.3 mAh g-1 at 0.2 C and 74.5 mAh g-1 at 50 C with minimal capacity loss after 100 cycles at a low temperature of -20 °C. Such electrochemical performance is superior to most of the reported layered oxide cathodes used in rechargeable SIBs.

In Situ Construction of Efficient Interface Layer with Lithiophilic Nanoseeds toward Dendrite-Free and Low N/P Ratio Li Metal Batteries.

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 Li2 S-rich interface layer joint with preplanted Sb nano active sites in hosted Li metal anode is easily achieved with the nanosized Sb2 S3 decorated carbonaceous network. The yielded CC@Sb2 S3 @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|LiNi0.5 Co0.2 Mn0.3 O2 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.

Lithiated Sulfur-Incorporated, Polymeric Cathode for Durable Lithium-Sulfur Batteries with Promoted Redox Kinetics.

Even though lithium-sulfur (Li-S) batteries have made much progress in terms of the delivered specific capacity and cycling stability by the encapsulation of sulfur within conductive carbon matrixes or polar materials, challenges such as low active sulfur utilization and unacceptable Coulombic efficiency are still hindering their commercial use. Herein, a lithium-rich conjugated sulfur-incorporated, polymeric material based on poly(Li2S6-r-1,3-diisopropenylbenzene) (DIB) is developed as a cathode material for high rate and stable Li-S batteries. Motivated by extra Li+ ions affording fast Li+ redox kinetics across the conjugated aromatic backbones, the Li-rich sulfur-based copolymer exhibits high delivery capacities (934 mAh g-1 at 120 cycles), impressive rate capabilities (727 mAh g-1 even under a current of 2 A g-1), and long electrochemical cycling performance over 500 cycles. Moreover, by use of the elastic nature and thermoplastic properties of the sulfur-incorporated, polymeric material, a prototype of a flexible Li-S pouch cell is constructed by using a poly(Li2S6-r-DIB) copolymer cathode and paired with the flexible carbon cloth/Si/Li anode, which exhibits stable electrochemical performance (658 mAh g-1 after 100 cycles) and operational capability even under folding at various angle (30°, 60°, 90°, 120°, 150°, 180°). This work extends the molecular-design approach to obtaining a high-performance organosulfur cathode material by introducing extra Li+ ions to promote redox kinetics, which provides valuable guidance for the development of high-performance Li-S batteries for practical applications.

Uniform and Anisotropic Solid Electrolyte Membrane Enables Superior Solid-State Li Metal Batteries.

Rational structure design is a successful approach to develop high-performance composite solid electrolytes (CSEs) for solid-state Li metal batteries. Herein, a novel CSE membrane is proposed, that consists of interwoven garnet/polyethylene oxide-Li bis(trifluoromethylsulphonyl)imide (LLZO/PEO-LiTFSI) microfibers. This CSE exhibits high Li-ion conductivity and exceptional Li dendrite suppression capability, which can be attributed to the uniform LLZO dispersion in PEO-LiTFSI and the vertical/horizontal anisotropic Li-ion conduction in the CSE. The uniform LLZO particles can generate large interaction regions between LLZO and PEO-LiTFSI, which thus form continuous Li-ion transfer pathways, retard the interfacial side reactions and strengthen the deformation resistance. More importantly, the anisotropic Li-ion conduction, that is, Li-ion transfers much faster along the microfibers than across the microfibers, can effectively homogenize the electric field distribution in the CSE during cycling, which thus prevents the excessive concentration of Li-ion flux. Finally, solid-state Li||LiFePO4 cells based on this CSE show excellent electrochemical performances. This work enriches the structure design strategy of high-performance CSEs and may be helpful for further pushing the solid-state Li metal batteries towards practical applications.

Li2(BH4)(NH2) Nanoconfined in SBA-15 as Solid-State Electrolyte for Lithium Batteries.

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.

Highly Lithiophilic Copper-Reinforced Scaffold Enables Stable Li Metal Anode.

Lithium (Li) metal is regarded as one of the most prospective electrodes for next-generation rechargeable batteries. However, its widespread usage has been fettered by low coulombic efficiency (CE), poor cycling stability, and serious safety concerns, mainly arising from huge volumetric variation, inhomogeneous Li deposition, and dendrite growth during repeated Li plating/stripping cycles. Herein, we propose a facile one-pot electrospinning-derived highly lithiophilic nanocopper-reinforced three-dimensional-structured carbon nanofiber (Cu-CNF) as functional scaffold to stabilize the Li metal. The Cu-CNF scaffolded Li metal demonstrates homogeneous nanoplate-like Li deposition, enhanced CE, and ultrastable long lifespan cycling. As coupled with LiNi0.8Co0.1Mn0.1O2 (NCM811), the cell possesses a remarkably stable high capacity retention of 93% over 300 cycles at 0.2 C. Furthermore, the cells paired with a thick LiFePO4 (LFP) electrode (∼12 mg cm-2) still can deliver a superior cycling performance even under the harsh conditions of an extremely low negative/positive electrode capacity (N/P) ratio (∼1.5) and lean electrolyte. Density functional theory calculations are performed to disclose the mechanism of the enhanced electrochemical performance of Cu-CNF scaffolded Li. This work provides a handy and cost-effective method to design superior performance Li metal anodes for practical applications.

Enabling a Stable Room-Temperature Sodium-Sulfur Battery Cathode by Building Heterostructures in Multichannel Carbon Fibers.

Room-temperature sodium-sulfur (RT Na-S) batteries are widely considered as one of the alternative energy-storage systems with low cost and high energy density. However, the both poor cycle stability and capacity are two critical issues arising from low conversion kinetics and sodium polysulfides (NaPSs) dissolution for sulfur cathodes during the charge/discharge process. Herein, we report a highly stable RT Na-S battery cathode via building heterostructures in multichannel carbon fibers. The TiN-TiO2@MCCFs, fabricated by electrospinning and nitriding techniques, are loaded with the active material S, forming S/TiN-TiO2@MCCFs as the cathode in a RT Na-S battery. At 0.1 A g-1, the cathode produces the capacity of more than 640 mAh g-1 within 100 cycles with a high Coulombic efficiency of nearly 100%. Even at 5 A g-1, the battery still exhibites a capacity of 257.1 mAh g-1 after 1000 cycles. Combining structural and electrochemical analyses with the first-principles calculations reveals that the incorporation of the highly electrocatalytic activity of TiN with the powerful chemisorption of TiO2 well stabilizes S and also alleviates the shuttle effects of polysulfides. This work with simple processes and low cost is expected to promote the further development and application of metal-S batteries.

Bifunctional Fluorinated Separator Enabling Polysulfide Trapping and Li Deposition for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are deemed as one of the most promising next generation energy storage system substitutes for conventional lithium ion batteries due to their high energy density, low cost, and environmental friendliness. The practical application of LSBs has long been blocked by the serious lithium polysulfide (LiPS) shuttle effect and notorious Li dendrite growth, inducing fast capacity decay and limited cycling lifespan. Herein, fluorinated carbon prepared via a safe and scalable strategy has rationally been coated on a separator affording bifunctional fluorinated Celgard (F-Celgard) for LSB construction. The F-Celgard shows superior Li+ flux modulation and LiPS trapping capability, which has been verified by the density function theory calculations. The Li symmetric cells demonstrate long and stable Li plating/stripping with much smaller polarization voltage and dendrite-free Li deposition. In addition, LSBs show superior rate performances with higher discharge capacities and long-time stable cycling over 1000 cycles at 1 C with a low decay rate of ∼0.038% per cycle. With a high sulfur loading (∼5.2 mg cm-2), a high initial areal capacity of ∼4.2 mAh cm-2 can be obtained with a superior capacity retention of ∼91.8% at 0.2 C. This work demonstrates a facile, cost-effective, and scalable strategy toward highly stable LSBs for practical usage.

Investigation on Fabrication of Reduced Graphene Oxide-Sulfur Composite Cathodes for Li-S Battery via Hydrothermal and Thermal Reduction Methods.

Lithium-sulfur (Li-S) battery is considered one of the possible alternatives for next-generation high energy batteries. However, its practical applications are still facing great challenges because of poor electronic conductivity, large volume change, and polysulfides dissolution inducing "shuttle reaction" for the S cathode. Many strategies have been explored to alleviate the aforementioned concerns. The most common approach is to embed S into carbonaceous matrix for constructing C-S composite cathodes. Herein, we fabricate the C-S cathode reduced graphene oxide-S (rGO-S) composites via one step hydrothermal and in-situ thermal reduction methods. The structural features and electrochemical properties in Li-S cells of the two type rGO-S composites are studied systematically. The rGO-S composites prepared by one step hydrothermal method (rGO-S-HT) show relatively better comprehensive performance as compared with the ones by in-situ thermal reduction method (rGO-S-T). For instance, with a current density of 100 mA g-1, the rGO-S-HT composite cathodes possess an initial capacity of 1290 mAh g-1 and simultaneously exhibit stable cycling capability. In particular, as increasing the current density to 1.0 A g-1, the rGO-S-HT cathode retains a reversible capacity of 582 mAh g-1 even after 200 cycles. The enhanced electrochemical properties can be attributed to small S particles uniformly distributed on rGO sheets enabling to significantly improve the conductivity of S and effectively buffer large volume change during lithiation/delithiation.

Green synthesis of graphite from CO2 without graphitization process of amorphous carbon.

Environmentally benign synthesis of graphite at low temperatures is a great challenge in the absence of transition metal catalysts. Herein, we report a green and efficient approach of synthesizing graphite from carbon dioxide at ultralow temperatures in the absence of transition metal catalysts. Carbon dioxide is converted into graphite submicroflakes in the seconds timescale via reacting with lithium aluminum hydride as the mixture of carbon dioxide and lithium aluminum hydride is heated to as low as 126 °C. Gas pressure-dependent kinetic barriers for synthesizing graphite is demonstrated to be the major reason for our synthesis of graphite without the graphitization process of amorphous carbon. When serving as lithium storage materials, graphite submicroflakes exhibit excellent rate capability and cycling performance with a reversible capacity of ~320 mAh g-1 after 1500 cycles at 1.0 A g-1. This study provides an avenue to synthesize graphite from greenhouse gases at low temperatures.

Highly Stable and Ultrahigh-Rate Li Metal Anode Enabled by Fluorinated Carbon Fibers.

The advanced energy storage of an Li metal substituted for graphite anode can provide a significant enhancement in a battery's energy density. Nevertheless, the practical implementation of metallic Li has seriously been fettered by the notorious Li dendrite growth and the huge volumetric variation of Li metal inducing poor cycling performance and safety concerns. In this regard, constructing a robust SEI layer combined with a 3D host to stabilize the Li metal is strongly in demand. Herein, a highly stable hosted Li with an LiF dominated SEI has successfully been achieved through metal-free fluorinated carbon fibers (FCF) with strong lithiophilicity. The metal-free design is cost-effective and can retain the energy density of the Li metal, minimizing the unnecessary energy sacrifice from the extra high gravimetric density lithiophilic sites. The FCF hosted Li delivers a promoted high Coulombic efficiency, homogeneous Li deposition, and ultrahigh rate stable cycling over 1000 cycles at 20 mA cm-2 with a much lower voltage polarization (≈220 mV). Moreover, half cells coupled with LiNi0.8 Co0.1 Mn0.1 O2 , sulfur or even thick LiCoO2 cathode demonstrate superior rate performances and enhanced cycling stability even under a lean electrolyte. This work proves the feasibility of FCF hosted Li for practical usage and provides a novel approach toward cost-effective and high performance lithium metal batteries.

Tailor-Made Gives the Best Fits: Superior Na/K-Ion Storage Performance in Exclusively Confined Red Phosphorus System.

As the most promising anodic candidate for alkali ion batteries, red phosphorus (P) still faces big challenges, such as the poor rate and cycling performance, which are caused by the insulative nature and the large volume change throughout the alloy/dealloy process. To ameliorate above issues, the traditional way is confining P into the carbon host. However, investigations on maximizing P utilization are inadequate; in other words, how to achieve entire confinement with a high loading amount is still a problem. Additionally, the application of P in potassium-ion batteries (PIBs) is in its infant stage, and the corresponding potassiation product is controversial. Herein, a nitrogen-doped stripped-graphene CNT (N-SGCNT) as carbon framework is prepared to exclusively confine ultrafine P to construct P@N-SGCNT composites. Benefitting from the in situ cross-linked structure, N-SGCNT loaded with 41.2 wt % P (P2@N-SGCNT) shows outstanding Na+/K+ storage performance. For instance, P2@N-SGCNT exhibits high reversible capacities of 2480 mAh g-1 for sodium-ion batteries (SIBs) and 762 mAh g-1 for PIBs, excellent rate capabilities of 1770 mAh g-1 for SIBs and 354 mAh g-1 for PIBs at 2.0 A g-1, and long cycling stability (a capacity of 1936 mAh g-1 after 2000 cycles for SIBs and 319 mAh g-1 after 1000 cycles for PIBs). Furthermore, due to this exclusively confined P structure, the K+ storage mechanism with the end product of K4P3 has been identified by experimental and theoretical results.

Fast and Stable Batteries with High Capacity Enabled by Germanium-Phosphorus Binary Nanoparticles Embedded in a Porous Carbon Matrix via Metallothermic Reduction.

Lithium-alloyable materials such as Ge and P have attracted considerable attention as promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity. However, these materials inevitably undergo capacity attenuation caused by large volume expansion in repeated electrochemical processes. Herein, we propose a facile strategy to synthesize germanium-phosphorus binary nanoparticles embedded in porous carbon (GPBN/C) via metallothermic reduction. As an LIB anode, the GPBN/C electrode exhibits outstanding rate performance (368 mAh g-1 at 40 A g-1) and remarkable long-term cycling ability (541 mAh g-1 at 1.0 A g-1 after 1000 cycles). Besides, the GPBN/C composite electrode presents an outstanding cycling performance at wide temperature ranges, showing reversible capacities of 1030 and 696 mAh g-1 at 60 and 0 °C, respectively. Attributed to the formation of highly dispersed Ge-P nanoparticles in a porous carbon matrix, the GPBN/C electrode shows exceptional electrochemical performance. Importantly, our strategy provides an effective way to explore alloy-type electrodes to develop fast and stable high-capacity batteries.

Boosting lithium ion storage of lithium nickel manganese oxide via conformally interfacial nanocoating.

In this work, a conformally interfacial nanocoating strategy is introduced to enhance the lithium ion storage performance of LiNi0.5Mn1.5O4 (LNMO). Stable cycling of LNMO is achieved through La2O3 coating at both room and elevated temperatures. A series of La2O3-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% La2O3-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 La2O3 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.

Homologous Strategy to Construct High-Performance Coupling Electrodes for Advanced Potassium-Ion Hybrid Capacitors.

Potassium-ion hybrid capacitors (PIHCs) have been considered as promising potentials in mid- to large-scale storage system applications owing to their high energy and power density. However, the process involving the intercalation of K+ into the carbonaceous anode is a sluggish reaction, while the adsorption of anions onto the cathode surface is relatively faster, resulting in an inability to exploit the advantage of high energy. To achieve a high-performance PIHC, it is critical to promote the K+ insertion/desertion in anodic materials and design suitable cathodic materials matching the anodes. In this study, we propose a facile "homologous strategy" to construct suitable anode and cathode for high-performance PIHCs, that is, unique multichannel carbon fiber (MCCF)-based anode and cathode materials are firstly prepared by electrospinning, and then followed by sulfur doping and KOH activation treatment, respectively. Owing to a multichannel structure with a large interlayer spacing for introducing S in the sulfur-doped multichannel carbon fiber (S-MCCF) composite, it presents high capacity, super rate capability, and long cycle stability as an anode in potassium-ion cells. The cathode composite of activated multichannel carbon fiber (aMCCF) has a considerably high specific surface area of 1445 m2 g-1 and exhibits outstanding capacitive performance. In particular, benefiting from advantages of the fabricated S-MCCF anode and aMCCF cathode by homologous strategy, PIHCs assembled with the unique MCCF-based anode and cathode show outstanding electrochemical performance, which can deliver high energy and power densities (100 Wh kg-1 at 200 W kg-1, and 58.3 Wh kg-1 at 10,000 W kg-1) and simultaneously exhibit superior cycling stability (90% capacity retention over 7000 cycles at 1.0 A g-1). The excellent electrochemical performance of the MCCF-based composites for PIHC electrodes combined with their simple construction renders such materials attractive for further in-depth investigations of alkali-ion battery and capacitor applications.

A modified 'skeleton/skin' strategy for designing CoNiP nanosheets arrayed on graphene foam for on/off switching of NaBH4 hydrolysis.

CoNiP nanosheet array catalysts were successfully prepared on three-dimensional (3D) graphene foam using hydrothermal synthesis. These catalysts were prepared using 3D Ni-graphene foam (Ni/GF), comprising nickel foam as the 'skeleton' and reduced graphene oxide as the 'skin'. This unique continuous modified 'skeleton/skin' structure ensure that the catalysts had a large surface area, excellent conductivity, and sufficient surface functional groups, which promoted in situ CoNiP growth, while also optimizing the hydrolysis of sodium borohydride. The nanosheet arrays were fully characterized and showed excellent catalytic performance, as supported by density functional theory calculations. The hydrogen generation rate and activation energy are 6681.34 mL min-1 g-1 and 31.2 kJ mol-1, respectively, outperforming most reported cobalt-based catalysts and other precious metal catalysts. Furthermore, the stability of mockstrawberry-like CoNiP catalyst was investigated, with 74.9% of the initial hydrogen generation rate remaining after 15 cycles. The catalytic properties, durability, and stability of the catalyst were better than those of other catalysts reported previously.