Achieving high-capacity and durable sodium storage by constructing a binder-free nanotube array architecture of iron phosphide/carbon.

The conversion-type anode material of iron phosphide (FeP) promises enormous prospects for Na-ion battery technology due to its high theoretical capacity and cost-effectiveness. However, the poor reaction kinetics and large volume expansion of FeP significantly degrade the sodium storage, which remains a daunting challenge. Herein, we demonstrate a binder-free nanotube array architecture constructed by FeP@C hybrid on carbon cloth as advanced anodes to achieve fast and stable sodium storage. The nanotubular structure functions in multiple roles of providing short electron/ion transport distances, smooth electrolyte diffusion channels, and abundant active sites. The carbon layer could not only pave high-speed pathways for electron conductance but also cushion the volume change of FeP. Benefiting from these structural virtues, the FeP@C anode receives a high reversible capacity of 881.7 mAh/g at 0.1 A/g, along with a high initial Coulombic efficiency of 90% and excellent rate capability and cyclability in half and full cells. Moreover, the sodium energy reaction kinetics and mechanism of FeP@C are systematically studied. The present work offers a rational design and construction of high-capacity anode materials for high-energy-density Na-ion batteries.

Manipulating the Host-Guest Chemistry of Cucurbituril to Propel Highly Reversible Zinc Metal Anodes.

Rechargeable aqueous zinc-ion batteries are practically plagued by the short lifespan and low Coulombic efficiency (CE) of Zn anodes resulting from random dendrite deposition and parasitic reactions. Herein, the host-guest chemistry of cucurbituril additive with Zn2+ to achieve longstanding Zn anodes is manipulated. The macrocyclic molecule of cucurbit[5]uril (CB[5]) is delicately designed to reconstruct both the CB[5]-adsorbed electric-double layer (EDL) structure at the Zn interface and the hydrated sheath of Zn2+ ions. Especially benefiting from the desirable carbonyl rims and suitable hydrophobic cavities, the CB[5] has a strong host-guest interaction with Zn2+ ions, which exclusively permits rapid Zn2+ flux across the EDL interface but retards the H2O radicals and SO4 2-. Accordingly, such a unique particle redistributor warrants long-lasting dendrite-free deposition by homogenizing Zn nucleation/growth and significantly improved CE by inhibiting side reactions. The Zn anode can deliver superior reversibility in CB[5]-containing electrolyte with a ninefold increase of cycle lifetime and an elevated CE of 99.7% under harsh test conditions (10 mA cm-2/10 mA h cm-2). The work opens a new avenue from the perspective of host-guest chemistry to propel the development of rechargeable Zn metal batteries and beyond.

Resolving Deactivation of Low-Spin Fe Sites by Redistributing Electron Density toward High-Energy Sodium Storage.

Prussian blue (PB) has been an emerging class of cathode material for sodium-ion batteries due to its low cost and high theoretical capacity. However, their working voltage and capacity are substantially restricted due to the deactivation of low-spin Fe sites. Herein, we demonstrate a universal strategy to activate the low-spin Fe sites of PB by hybridizing them with the π-π conjugated electronic conductors. The redistribution of electron density between π-π conjugated conductors and PB effectively promotes the participation of low-spin Fe sites in sodium storage. Consequently, the low-spin Fe-induced plateau is greatly aroused, resulting in a high specific capacity of 148.4 mAh g-1 and remarkable energy density of 444.2 Wh kg-1. In addition, the excellent structural stability enables superior cycling stability over 2500 cycles and outstanding rate performance. The work will provide fundamental insight into activating the low-spin Fe sites of PB for advanced battery technologies.

A Seamless Metal-Organic Framework Interphase with Boosted Zn2+ Flux and Deposition Kinetics for Long-Living Rechargeable Zn Batteries.

Zn metal has received immense interest as a promising anode of rechargeable aqueous batteries for grid-scale energy storage. Nevertheless, the uncontrollable dendrite growth and surface parasitic reactions greatly retard its practical implementation. Herein, we demonstrate a seamless and multifunctional metal-organic framework (MOF) interphase for building corrosion-free and dendrite-free Zn anodes. The on-site coordinated MOF interphase with 3D open framework structure could function as a highly zincophilic mediator and ion sifter that synergistically induces fast and uniform Zn nucleation/deposition. In addition, the surface corrosion and hydrogen evolution are significantly suppressed by the interface shielding of the seamless interphase. An ultrastable Zn plating/stripping is achieved with elevated Coulombic efficiency of 99.2% over 1000 cycles and prolonged lifetime of 1100 h at 10 mA cm-2 with a high cumulative plated capacity of 5.5 Ah cm-2. Moreover, the modified Zn anode assures the MnO2-based full cells with superior rate and cycling performance.

Ultrafine MoS2 Nanosheets Vertically Patterned on Graphene for High-Efficient Li-Ion and Na-Ion Storage.

Hierarchically two-dimensional (2D) heteroarchitecture with ultrafine MoS2 nanosheets vertically patterned on graphene is developed by using a facile solvothermal method. It is revealed that the strong interfacial interaction between acidic Mo precursors and graphene oxides allows for uniform and tight alignment of edge-oriented MoS2 nanosheets on planar graphene. The unique sheet-on-sheet architecture is of grand advantage in synergistically utilizing the highly conductive graphene and the electroactive MoS2, thus rendering boosted reaction kinetics and robust structural integrity for energy storage. Consequently, the heterostructured MoS2@graphene exhibits impressive Li/Na-ion storage properties, including high-capacity delivery and superior rate/cycling capability. The present study will provide a positive impetus on rational design of 2D metal sulfide/graphene composites as advanced electrode materials for high-efficient alkali-metal ion storage.

Building Ohmic Contact Interfaces toward Ultrastable Zn Metal Anodes.

Zn metal holds grand promise as the anodes of aqueous batteries for grid-scale energy storage. However, the rampant zinc dendrite growth and severe surface side reactions significantly impede the commercial implementation. Herein, a universal Zn-metal oxide Ohmic contact interface model is demonstrated for effectively improving Zn plating/stripping reversibility. The high work function difference between Zn and metal oxides enables the building of an interfacial anti-blocking layer for dendrite-free Zn deposition. Moreover, the metal oxide layer can function as a physical barrier to suppress the pernicious side reactions. Consequently, the proof-of-concept CeO2 -modified Zn anode delivers ultrastable durability of over 1300 h at 0.5-5 mA cm-2 and improved Coulombic efficiency, the feasibility of which is also evidenced in MoS2 //Zn full cells. This study enriches the fundamental comprehension of Ohmic contact interfaces on the Zn deposition, which may shed light on the development of other metal battery anodes.

Mechanistic investigation of silver vanadate as superior cathode for high rate and durable zinc-ion batteries.

Rechargeable aqueous Zn-ion batteries have shown considerable potential for stationary grid-scale energy storage systems owing to their characteristics of low cost and non-pollution. Nevertheless, the development of high-performance cathode materials is still a formidable challenge. In this work, for the first time, we report a superior silver vanadate (ß-AgVO3) cathode for Zn-ion batteries, and demonstrate the fundamental Zn2+ storage mechanism in detail. In sharp contrast to the previously-reported layered vandium-based materials, the ß-AgVO3 cathode experiences an initial phase transition to form a layered Zn3V2O7(OH)2·2H2O through a displacement/reduction reaction of Zn2+/Ag+ in the first discharge process. The in situ generated Ag0 along with the residual Ag+ and structural water within the framework afford high electronic/ionic conductivity, thus enabling enhanced Zn2+ intercalation/deintercalation kinetics in the layered phase. As a consequence, the cathode can deliver remarkable rate performance (103 mAh g-1 at 5000 mA g-1) and long-term cycling stability (95 mAh g-1 after 1000 cycles at 2000 mA g-1). The present study offers a totally new insight into the exploration of non-layered-structured vandium-based cathodes for high performance Zn-ion batteries.