Phase-Selective Synthesis of Ruthenium Phosphide in Hybrid Structure Enables Efficient Hybrid Water Electrolysis Under pH-Universal Conditions.

Hydrazine-assisted hybrid water electrolysis is an energy-saving approach to produce high-purity hydrogen, whereas the development of pH-universal bifunctional catalysts encounters a grand challenge. Herein, a phase-selective synthesis of ruthenium phosphide compounds hybrid with carbon forming pancake-like particles (denoted as Rux P/C-PAN, x = 1 or 2) is presented. The obtained RuP/C-PAN exhibits the highest catalytic activity among the control samples, delivering ultralow cell voltages of 0.03, 0.27, and 0.65 V to drive 10 mA cm-2 using hybrid water electrolysis corresponding to pH values of 14, 7, and 0, respectively. Theoretical calculation deciphers that the RuP phase displays optimized free energy for hydrogen adsorption and reduced energy barrier for hydrazine dehydrogenation. This work may not only open up a new avenue in exploring universally compatible catalyst to transcend the limitation on the pH value of electrolytes, but also push forward the development of an energy-saving hydrogen generation technique based on emerging hybrid water electrolysis.

Tailoring Nitrogen Species in Disk-Like Carbon Anode Towards Superior Potassium Ion Storage.

Carbon materials, as promising anode candidates for K+ storage due to their low cost, abundant sources, and high physicochemical stability, however, encounter limited specific capacity and unfavorable cycling stability that seriously hinder their practical applications. Herein, a feasible strategy to tailor and stabilize the nitrogen species in unique P/N co-doped disk-like carbon through the Sn incorporation (P/NSn -CD) is presented, which can largely enhance the specific capacity and cycling capability for K+ storage. Specifically, it delivers a high specific capacity of 439.3 mAh g-1 at 0.1 A g-1 and ultra-stable cycling capability with a capacity retention of 93.5% at 5000 mA g-1 over 5000 cycles for K+ storage. The underlying mechanism for the superior K+ storage performance is investigated by systematical experimental data combined with theoretical simulation results, which can be derived from the increased edge-nitrogen species, improved content and stability of P/N heteroatoms, and enhanced ionic/electronic kinetics. After coupling P/NSn -CD anode with activated carbon cathode, the KIHCs can deliver a high energy density of 171.7 Wh kg-1 at 106.8 W kg-1 , a superior power density (14027.0 W kg-1 with 31.2 Wh kg-1 retained), and ultra-stable lifespan (89.7% retention after 30 K cycles with cycled at 2 A g-1 ).

Natural Soft/Rigid Superlattices as Anodes for High-Performance Lithium-Ion Batteries.

Volume expansion and poor conductivity are two major obstacles that hinder the pursuit of the lithium-ion batteries with long cycling life and high power density. Herein, we highlight a misfit compound PbNbS3 with a soft/rigid superlattice structure, confirmed by scanning tunneling microscopy and electrochemical characterization, as a promising anode material for high performance lithium-ion batteries with optimized capacity, stability, and conductivity. The soft PbS sublayers primarily react with lithium, endowing capacity and preventing decomposition of the superlattice structure, while the rigid NbS2 sublayers support the skeleton and enhance the migration of electrons and lithium ions, as a result leading to a specific capacity of 710 mAh g-1 at 100 mA g-1 , which is 1.6 times of NbS2 and 3.9 times of PbS. Our finding reveals the competitive strategy of soft/rigid structure in lithium-ion batteries and broadens the horizons of single-phase anode material design.

Designed Formation of Hybrid Nanobox Composed of Carbon Sheathed CoSe2 Anchored on Nitrogen-Doped Carbon Skeleton as Ultrastable Anode for Sodium-Ion Batteries.

Research on sodium-ion batteries (SIBs) has recently been revitalized due to the unique features of much lower costs and comparable energy/power density to lithium-ion batteries (LIBs), which holds great potential for grid-level energy storage systems. Transition metal dichalcogenides (TMDCs) are considered as promising anode candidates for SIBs with high theoretical capacity, while their intrinsic low electrical conductivity and large volume expansion upon Na+ intercalation raise the challenging issues of poor cycle stability and inferior rate performance. Herein, the designed formation of hybrid nanoboxes composed of carbon-protected CoSe2 nanoparticles anchored on nitrogen-doped carbon hollow skeletons (denoted as CoSe2 @C∩NC) via a template-assisted refluxing process followed by conventional selenization treatment is reported, which exhibits tremendously enhanced electrochemical performance when applied as the anode for SIBs. Specifically, it can deliver a high reversible specific capacity of 324 mAh g-1 at current density of 0.1 A g-1 after 200 cycles and exhibit outstanding high rate cycling stability at the rate of 5 A g-1 over 2000 cycles. This work provides a rational strategy for the design of advanced hybrid nanostructures as anode candidates for SIBs, which could push forward the development of high energy and low cost energy storage devices.

Designed One-Pot Strategy for Dual-Carbon-Protected Na3 V2 (PO4 )3 Hybrid Structure as High-Rate and Ultrastable Cathode for Sodium-Ion Batteries.

Sodium-ion batteries have attracted tremendous attention due to their much lower cost and similar working principle compared with lithium-ion batteries, which have been invited great expectation as energy storage devices in grid-level applications. The sodium superionic conductor Na3 V2 (PO4 )3 has been considered as a promising cathode candidate; however, its intrinsic low electronic conductivity results in poor rate performance and unsatisfactory cycling performance, which severely impedes its potential for practical applications. Herein, we developed a facile one-pot strategy to construct dual carbon-protected hybrid structure composed of carbon coated Na3 V2 (PO4 )3 nanoparticles embedded with carbon matrix with excellent rate performance, superior cycling stability and ultralong lifespan. Specifically, it can deliver an outstanding rate performance with a 51.5 % capacity retention from 0.5 to 100 C and extraordinary cycling stability of 80.86 % capacity retention after 6000 cycles at the high rate of 20 C. The possible reasons for the enhanced performance could be understood as the synergistic effects of the strengthened robust structure, facilitated charge transfer kinetics, and the mesoporous nature of the Na3 V2 (PO4 )3 hybrid structure. This work provides a cost-effective strategy to effectively optimize the electrochemical performance of a Na3 V2 (PO4 )3 cathode, which could contribute to push forward the advance of its practical applications.

Hybrid ion/electron interfacial regulation stabilizes the cobalt/oxygen redox of ultrahigh-voltage lithium cobalt oxide for fast-charging cyclability.

High-voltage and fast-charging LiCoO2 (LCO) is key to high-energy/power-density Li-ion batteries. However, unstable surface structure and unfavorable electronic/ionic conductivity severely hinder its high-voltage fast-charging cyclability. Here, we construct a Li/Na-B-Mg-Si-O-F-rich mixed ion/electron interface network on the 4.65 V LCO electrode to enhance its rate capability and long-term cycling stability. Specifically, the resulting artificial hybrid conductive network enhances the reversible conversion of Co3+/4+/O2-/n- redox by the interfacial ion-electron cooperation and suppresses interface side reactions, inducing an ultrathin yet compact cathode electrolyte interphase. Simultaneously, the derived near-surface Na+/Mg2+/Si4+-pillared local intercalation structure greatly promotes the Li+ diffusion around the 4.55 V phase transition and stabilizes the cathode interface. Finally, excellent 3 C (1 C = 274 mA g-1) fast charging performance is demonstrated with 73.8% capacity retention over 1000 cycles. Our findings shed new insights to the fundamental mechanism of interfacial ion/electron synergy in stabilizing and enhancing fast-charging cathode materials.

Engineering Electronic Transfer Dynamics and Ion Adsorption Capability in Dual-Doped Carbon for High-Energy Potassium Ion Hybrid Capacitors.

Sodium and potassium ions energy storage systems with low cost and high energy/power densities have recently drawn increasing interest as promising candidates for grid-level applications, while the lack of suitable anode materials with fast ion diffusion kinetics highly hinders their development. Herein, we develop a nanoscale confined in situ oxidation polymerization process followed by a conventional carbonization treatment to generate phosphorus and nitrogen dual-doped hollow carbon spheres (PNHCS), which can realize superior sodium and potassium ion storage performance. Importantly, the density functional theory calculation and combined characterizations, e.g., in situ Raman spectroscopy and ex situ X-ray photoelectron spectroscopy, decipher that the P/N doping can enhance the electronic transfer dynamics and ion adsorption capability, which are responsible for enhanced electrochemical performance. Inspiringly, the practicability of the PNHCS anode is demonstrated by assembling the potassium ion hybrid capacitors (KIHCs), where the prominent energy density is 178.80 Wh kg-1 at a power density of 197.65 W kg-1, with excellent cycling stability, can be achieved. This work not only promotes the development of efficient anode material for sodium/potassium ion storage devices but also deciphers the embedded ion storage mechanism.

Rational Design of Unique MoSe2-Carbon Nanobowl Particles Endows Superior Alkali Metal-Ion Storage Beyond Lithium.

Attracted by the rich earth abundance and low-cost advantages, alkali metal-ion (Na/K)-based energy storage devices have attracted wide interest as promising candidates for energy economizing in recent years. Unfortunately, the lack of suitable host materials with high capacity and long life span for alkali metal-ion storage has severely impeded their practical application in large-scale energy storage devices. Herein, we present a promising anode candidate composed of ultrasmall MoSe2 clusters embedded in a nitrogen-doped hollow carbon nanobowl substrate to form unique MoSe2-Carbon nanobowl particles (denoted as MoSe2⊂CNB). MoSe2⊂CNB demonstrates exceptional electrochemical properties for alkali metal-ion storage including sodium and potassium. In situ Raman spectroscopy and galvanostatic intermittent titration measurements reveal the possible reason for the high performance of MoSe2⊂CNB. Notably, the assembled potassium-ion hybrid capacitors could manifest an extraordinary energy density of 130.7 W h kg-1 at 0.2 A g-1, a high power density of 13,607 W kg-1, and an enviable cycle life after 6000 cycles, further reflecting the great developmental potential for energy storage devices in practical applications. This work provides a new method to design functional nanostructures for electrode materials to drive the development and application of possible energy storage devices.

Dual-Functional Template-Induced In Situ Polymerization Process Enables the Hierarchical Carbonaceous Nanotubes with Simultaneous Sn Cluster Incorporation and Nitrogen-Doping for Superior Potassium-Ion Storage.

Potassium ion-based energy storage devices have received extensive attention for grid-level applications due to their abundant natural resources and low cost. However, the large ionic radius of K+ leads to inferior capacities and cyclic stability, which hinders their practical application. Herein, hierarchical carbonaceous nanotubes with simultaneous ultrasmall Sn cluster incorporation and nitrogen doping (denoted as u-Sn@NCNTs) are fabricated using MnO2 nanowires as a dual-functional template (in situ polymerization and shape-directing agents) and subsequent carbonization treatment. The u-Sn@NCNTs exhibit a superior K+ storage capability with a high reversible capacity (220.1 mA h g-1 at 0.1 A g-1) and long cycling stability (149.9 mA h g-1 at 1 A g-1 after 4000 cycles). Besides, the u-Sn@NCNTs exhibit superior cycling stability up to 10000 cycles at 5 A g-1 for Na+ storage. The potassium storage mechanism and kinetics are investigated based on ex situ X-ray photoelectron spectroscopy, in situ Raman spectrum, and galvanostatic intermittent titration technique. More importantly, u-Sn@NCNTs can be used as the anode for potassium ion hybrid capacitors, achieving a superior energy density of 181.4 W h kg-1 at a power density of 185 W kg-1 with excellent cycling capability. This work could push forward the development and application of carbonaceous-based anode materials for next-generation high-performance rechargeable batteries.

Phosphorus-doping-induced kinetics modulation for nitrogen-doped carbon mesoporous nanotubes as superior alkali metal anode beyond lithium for high-energy potassium-ion hybrid capacitors.

Alkali metal ion beyond lithium based energy storage systems have recently attracted increasing attention due to their unique advantages of high natural abundance and low cost. Herein, we report the fabrication of P,N-codoped carbon mesoporous nanotubes (denoted as PNC-MeNTs) through a facile two-step strategy with MnO2 nanowires as a dual-function sacrificing template, where the in situ oxidative polymerization formation of pyrrole-aniline-phytic acid composite nanotubes and a subsequent carbonization treatment are involved. The PNC-MeNTs exhibit outstanding electrochemical performance for both Na+ and K+ storage, respectively, where high specific capacities of 287.2 mA h g-1 and 219.6 mA h g-1 at 0.1 A g-1 and remarkable cycling stability over 10 000 cycles at 10 A g-1 and 3000 cycles at 1 A g-1 can be achieved. More importantly, potassium-ion hybrid capacitors with a PNC-MeNT anode and an activated carbon cathode can deliver remarkable energy/power density of 175.1 W h kg-1/160.6 W kg-1, as well as a long cycling life. The possible origins and storage mechanisms are investigated with combined characterization methods including in situ Raman spectroscopy and a galvanostatic intermittent titration technique. This study may introduce a new avenue for designing carbonaceous electrode candidates for future high-performance energy storage devices.