Reversible Conversion Reaction Research Articles

Initiating Reversible Aqueous Copper-Tellurium Conversion Reaction with High Volumetric Capacity through Electrolyte Engineering.

Pursuing conversion-type cathodes with high volumetric capacity that can be used in aqueous environments remains rewarding and challenging. Tellurium (Te) is a promising alternative electrode due to its intrinsic attractive electronic conductivity and high theoretical volumetric capacity yet still to be explored. Herein, the kinetically/thermodynamically co-dominat copper-tellurium (Cu-Te) alloying phase-conversion process and corresponding oxidation failure mechanism of tellurium are investigated using in situ synchrotron X-ray diffraction and comprehensive ex situ characterization techniques. By virtue of the fundamental insights into the tellurium electrode, facile and precise electrolyte engineering (solvated structure modulation or reductive antioxidant addition) is implemented to essentially tackle the dramatic capacity loss in tellurium, affording reversible aqueous Cu-Te conversion reaction with an unprecedented ultrahigh volumetric capacity of up to 3927mAhcm-3 , a flat long discharge plateau (capacity proportion of ≈81%), and an extraordinary level of capacity retention of 80.4% over 2000 cycles at 20Ag-1 of which lifespan thousand-fold longer than Cu-Te conversion using CuSO4 -H2 O electrolyte. This work paves a significant avenue for expanding high-performance conversion-type cathodes toward energetic aqueous multivalent-ion batteries.

Nanocrystal Conversion Chemistry within Slit-like 2D Nanogap for High-Rate Cyclic Stability of Lithium-Ion Battery Anodes.

Nanoscale optimization of late transition-metal oxides for fixing the reversible lithiation/delithiation mechanism with an in-depth mechanistic understanding of nanocrystal (NC) conversion chemistry is important for furthering next-generation Li-ion battery (LIB) technologies. Herein, 1 nm-thin Ni3CoOx (1 nm-NCO) nanosheets synthesized through isomorphic transformation of NiCo layered double hydroxides within a two-dimensional (2D)-SiO2 envelope are chosen. The interconversion of metal/metal-oxide NCs under redox-switching thermal treatment, while retaining reversibility, inspired the accomplishment of identical consequences under the harsh operational conditions of LIB redox cycles by application of the thin-NCO-defined 2D nanospace. During charge/discharge cycles, 1 nm-NCO covered with an in situ formed solid-electrolyte-interphase layer enables fully reversible interconversion between the reactive NC redox pairs, as evidenced by detailed morphological and electrochemical analyses, thus providing high-rate capability with a specific capacity of 61.2% at 5.0 C relative to 0.2 C, outstanding cycle stability delivering a reversible capacity of 1169 mAh g-1, and 913 mAh g-1 with high average Coulombic efficiency (>99.2%) at 3.0 and 5.0 C for 1000 cycles, respectively, which has not been achieved with other transition-metal oxides. Such a nanospace-confinement effect on sustainability of reactive NCs to follow-up a highly reversible conversion reaction at fast charging in LIBs is operative within a slit-like ultrathin 2D nanogap from 1 nm-NCO only, as a relatively thicker 7 nm-NCO anode, with accompanying larger space available, has evidenced poor reversibility of NCs and inadequate cyclic stability under potential high-power density LIB application.

WS2 Nanosheet Loaded Silicon-Oxycarbide Electrode for Sodium and Potassium Batteries

Transition metal dichalcogenides (TMDs) such as the WS2 have been widely studied as potential electrode materials for lithium-ion batteries (LIB) owing to TMDs' layered morphology and reversible conversion reaction with the alkali metals between 0 to 2 V (v/s Li/Li+) potentials. However, works involving TMD materials as electrodes for sodium- (NIBs) and potassium-ion batteries (KIBs) are relatively few, mainly due to poor electrode performance arising from significant volume changes and pulverization by the larger size alkali-metal ions. Here, we show that Na+ and K+ cyclability in WS2 TMD is improved by introducing WS2 nanosheets in a chemically and mechanically robust matrix comprising precursor-derived ceramic (PDC) silicon oxycarbide (SiOC) material. The WS2/SiOC composite in fibermat morphology was achieved via electrospinning followed by thermolysis of a polymer solution consisting of a polysiloxane (precursor to SiOC) dispersed with exfoliated WS2 nanosheets. The composite electrode was successfully tested in Na-ion and K-ion half-cells as a working electrode, which rendered the first cycle charge capacity of 474.88 mAh g-1 and 218.91 mAh g-1, respectively. The synergistic effect of the composite electrode leads to higher capacity and improved coulombic efficiency compared to the neat WS2 and neat SiOC materials in these cells.

A solid-to-solid metallic conversion electrochemistry toward 91% zinc utilization for sustainable aqueous batteries.

The diffusion-limited aggregation (DLA) of metal ion (Mn+) during the repeated solid-to-liquid (StoL) plating and liquid-to-solid (LtoS) stripping processes intensifies fatal dendrite growth of the metallic anodes. Here, we report a new solid-to-solid (StoS) conversion electrochemistry to inhibit dendrites and improve the utilization ratio of metals. In this StoS strategy, reversible conversion reactions between sparingly soluble carbonates (Zn or Cu) and their corresponding metals have been identified at the electrode/electrolyte interface. Molecular dynamics simulations confirm the superiority of the StoS process with accelerated anion transport, which eliminates the DLA and dendrites in the conventional LtoS/StoL processes. As proof of concept, 2ZnCO3·3Zn(OH)2 exhibits a high zinc utilization of ca. 95.7% in the asymmetry cell and 91.3% in a 2ZnCO3·3Zn(OH)2 || Ni-based full cell with 80% capacity retention over 2000 cycles. Furthermore, the designed 1-Ah pouch cell device can operate stably with 500 cycles, delivering a satisfactory total energy density of 135 Wh kg−1.

Iron Fluoride Confined in Carbon Nanofibers for Lithium and Sodium Battery Cathodes

Today, lithium (sodium) battery cathodes based on the intercalation/deintercalation of lithium (sodium) ions are approaching their instinctive limits, which remains a big challenge for the development of next-generation batteries. Iron fluorides (FeF2, FeF3), a potential alternative to current intercalation cathodes, are believed to offer much higher capacity and higher energy due to their reversible conversion reactions during charging/discharging. However, their structural degradation and capacity fading upon cycling could block the road to future applications. To address these issues, we developed a stable iron fluoride cathode based on nanoconfined FeF3 in carbon nanofibers for lithium and sodium batteries. The produced FeF3 /C nanocomposite is free-standing and can be produced using an electrospinning-based strategy with post carbonization and fluorination process. When tested in lithium cells, the nanocomposite can exhibit a high specific capacity up to 550 mAh g– 1 and a cycle stability over 400 cycles [1]. When tested in sodium cells, the nanocomposite can deliver a high specific capacity of 230 mAh g– 1 in sodium-difluoro(oxalato)borate (NaDFOB) electrolyte [2]. The performance especially cycle stability was further improved by atomic layer deposition (ALD) of Al2O3 coating on nanofiber surface [3]. We find the coating can reduce the direct contact between active material and liquid electrolyte, minimize active material dissolution and significantly improve the overall performance.[1] W. Fu, E. Zhao, Z. Sun, X. Ren, A. Magasinski, G. Yushin, Iron Fluoride–Carbon Nanocomposite Nanofibers as Free-Standing Cathodes for High-Energy Lithium Batteries, Advanced Functional Materials 28 (2018) 1801711.[2] Z. Sun, W. Fu, M.Z. Liu, P. Lu, E. Zhao, A. Magasinski, M. Liu, S. Luo, J. McDaniel, G. Yushin, A nanoconfined iron(iii) fluoride cathode in a NaDFOB electrolyte: towards high-performance sodium-ion batteries, Journal of Materials Chemistry A 8 (2020) 4091-4098.[3] Z. Sun, M. Boebinger, M. Liu, P. Lu, W. Fu, B. Wang, A. Magasinski, Y. Zhang, Y. Huang, A.Y. Song, M.T. McDowell, G. Yushin, The roles of atomic layer deposition (ALD) coatings on the stability of FeF3 Na-ion cathodes, Journal of Power Sources 507 (2021) 230281.

A conversion-type lithium artificial synapse with dispersed nano-silica fabricated by UV-curing method

The rapid growth of information puts forward new requirements for computer including denser memory capacity and faster response beyond the traditional von Neumann architecture. One promising strategy is to employ novel computing devices such as artificial synapses (AS). Here, an Au/LPSE-SiO2/Si AS (LPSE-SiO2 AS) with a simple sandwich structure was fabricated by UV curing. LPSE-SiO2 AS emulated synaptic plasticity including excitatory postsynaptic current, paired-pulse facilitation, and spike-dependent plasticity. It also simulated the memory strengthening and forgetting analogue to biological system. The realization of synaptic plasticity is due to the homogeneously dispersed nano-silica in LPSE, which acts as lithium ions trapping center and conducts a reversible electrochemical conversion reaction with Li ions with pulse stimulation. These results indicate the potential for LPSE-SiO2 AS in future large-scale integrated neuromorphic networks.

FeF3 as Reversible Cathode for All‐Solid‐State Fluoride Batteries

Fluoride batteries are attracting intensive attention because they can provide a higher energy density than conventional lithium‐ion batteries. Among various metal fluorides, FeF3 is a promising candidate for the cathode material of fluoride batteries because of its high theoretical capacity. In this report, the reversibility of an FeF3 cathode is investigated in conjunction with fluorite‐type Ba0.6La0.4F2.4 as the electrolyte and Pb as the counter‐electrode material. For the first time, the discharge–charge performance of a fluoride battery using FeF3 cathode is investigated. The initial discharge capacity is 579 mAh g−1, and a capacity of 461 mAh g−1 is retained at the 10th cycle. The reversible conversion reaction mechanism for FeF3 is clarified by X‐ray diffraction and X‐ray adsorption spectroscopy. The results revealed that FeF3 is reduced to FeF2 at the first‐stage plateau and then to Fe metal at the second‐stage plateau; they also reveal that the reverse process proceeded during charging. Ex situ scanning electron microscopy observations show that the morphology of the cathode changed reversibly and that, when the battery is in the discharged state, voids are present because of shrinkage of the electrode.

Realizing High-Performance Lithium Storage by Fabricating FeTiO3 Nanoparticle-Impregnated Multichannel Carbon Nanofibers with Promoted Reaction Kinetics.

In this paper, a free-standing film of ilmenite FeTiO3 nanoparticle-impregnated porous multichannel N-doped carbon nanofibers (NF-FTO) is fabricated via electrospinning technology. The as-prepared NF-FTO film is highly flexible and can be tailored to a suitable size to assemble into lithium-ion batteries. The introduction of a conductive N-doped carbon matrix is conducive to the improvement of intrinsic electronic conductivity and the acceleration of Li+ diffusion kinetics. The construction of the porous structure and highly parallel channels facilitates the transfer of electrolyte to FTO particles through the pores and shortens the transport path of lithium ions. Thus, the self-supporting electrode yields an initial charge capacity of 718.5 mAh g-1 at 50 mA g-1, a high-rate performance of 410.4 mAh g-1 at 3 A g-1, and an outstanding cycling performance with no capacity decay after 1500 cycles at 3 A g-1. By ex situ X-ray diffraction and transmission electron microscopy analysis, the reaction mechanism of NF-FTO is determined as a reversible conversion reaction. Furthermore, the assembled LiFePO4/NF-FTO full cell delivers an initial discharge capacity of 521 mAh g-1 and superb rate performance.

Amorphous carbon nanofibers incorporated with ultrafine GeO2 nanoparticles for enhanced lithium storage performance

As a potential anode material with high theoretical specific capacity, the practical application of GeO 2 is largely hindered by huge volume change and low reactivity, Herein, we proposed the engineering of dual amorphous GeO 2 @C nanofibers via facile electrospinning and thermal annealing process. In this design, numerous ultrafine GeO 2 particles are evenly anchored in carbon nanofibers, which could relief the stress in the carbon material during the lithium/delithiation process. Moreover, the low binding energy of Ge-O bond in the dual amorphous GeO 2 /C nanofibers render for convenient charge transfer. As a result, the electrode delivers highly reversible conversion (GeO 2 + 4Li ↔ Ge + 2Li 2 O) and alloying (Ge + 4.4Li ↔ GeLi 4.4 ) reaction. Furthermore, the GeO 2 @C nanofibers with large specific surface area also supply more active sites for pseudocapacitive lithium storage. Benefitting from the typical structure, the dual amorphous GeO 2 @C nanofibers electrode exhibits high reversible capacity of 1053 mAh g −1 at 0.3 A g −1 after 1000 cycle, and superior rate capacity of 476 mAh g −1 at 5 A g −1 . The excellent electrochemical performance endows dual amorphous GeO 2 @C nanofibers competitive electrode material for next-generation lithium-ion batteries. • Dual amorphous GeO 2 @C nanofibers were prepared by a facile and efficient approach. • Dual amorphous GeO 2 @C nanofibers display outstanding lithium storage properties. • Dual amorphous structure benefits for superior lithium storage.

Vertically oriented MoSe0.4S1.6/N-doped C nanostructures directly grown on carbon nanotubes as high-performance anode for potassium-ion batteries

A novel sandwiched hybrid nanoplates vertically anchor on carbon nanotubes. The nanomaterials have facile K-ion intercalation and rapid K-ion transport simultaneously, and can maintain high reversible conversion reaction. The nanomaterials deliver enhanced conductivity and accelerated diffusion kinetics. The as-prepared electrode improves cycle stability and rate performance with reversible capacity. • A novel hybrid nanostructures were prepared for MoSe 0.4 S 1.6 / N -doped C directly grown on carbon nanotubes as high-performance anode. • The electrode improves excellent cycle stability and rate performance with reversible capacity. • The assembled full batteries of coin-type and soft-packed-type can readily lighted up LED bulbs and power the little motor to spin. • The obtained nanomaterials have facile K-ion intercalation and rapid K-ion transport simultaneously. Potassium-ion batteries are a promising candidate for future large-scale energy storage systems due to their merits of cost-effectiveness, high safety, and high-power operation. However, developing suitable anode materials with outstanding kinetics and excellent structural stability remain a great challenge. Herein, in this work, a novel sandwiched hybrid nanoplates vertically anchor on carbon nanotubes, which can improve more edge planes such as (0 0 2) plane to expose. The hybrid nanoplates are consist of N -doped C sandwiched monolayer MoSe 0.4 S 1.6 . The N -doped C layers can adequately contact with S/Se atoms. The introduction of Se in the lattice effectively endows the electrode with fast reaction kinetics and superior cycle stability, with an admirable reversible capacity of 143.7 mAh/g after 1500 cycles at 2.0 A/g. The Se in the lattice can inhibit the agglomeration of Mo atom clusters, and maintain high reversible conversion reaction. Benefit from Se doping, the electrodes have facile K-ion intercalation and rapid K-ion transport simultaneously. Finally, the K-ion full batteries were assembled with prepotassium-perylenetetracarboxylic dianhydride (prepotassium-PTCDA) as a cathode to demonstrate the practical application.

Architectural van der Waals Bi2S3/Bi2Se3 topological heterostructure as a superior potassium-ion storage material

• A hexagram-like 1D/2D van der Waals heterostructure (vdWH) composed of regularly crosslinked Bi 2 S 3 nanowires on Bi 2 Se 3 nanoplates was fabricated. • The Bi 2 S 3 /Bi 2 Se 3 vdWH potassium ion anode delivers a specific capacity over 600 mA h g -1 at 50 mA g −1 and a high-rate capability up to 2500 mA g −1 . • The behavior of heterogeneous interfacial reaction in terms of the trapping ability and diffusion kinetics was realized. • The potassium ion battery exhibits an energy density of 208 Wh Kg −1 over 850 cycles. • The potassium ion hybrid capacitor exhibits an energy density of 106 Wh Kg −1 over 3000 cycles. We design a hexagram-like 1D/2D van der Waals heterostructure composed of regularly crosslinked aligned 1D Bi 2 S 3 nanowires on 2D Bi 2 Se 3 nanoplates, termed Bi 2 S 3 /Bi 2 Se 3 vdWHs, for use as anode materials for potassium ion batteries (PIBs) and hybrid capacitors (PIHCs). Thanks to the mixed dimensional topological heterostructures, the abundant network-contacted heterojunctions facilitate ordered ion/electron transport around the surface network and interior topological materials, and simultaneously promoting the K + diffusion, electron transfer, and electrolyte infiltration. The Bi 2 S 3 /Bi 2 Se 3 vdWHs deliver an attractive specific capacity over 600 mA h g -1 at 50 mA g −1 , a high-rate capability up to 2500 mA g −1 , and excellent cycling stability. Theoretical models, in tandem with operando X-ray diffraction and HRTEM analysis reveal the behavior of heterogeneous interfacial reaction in terms of the trapping ability and diffusion kinetics, confirming the reversible conversion reaction of Bi 2 S 3 /Bi 2 Se 3 vdWHs. Finally, the full cells of PIBs and PIHCs coupled with Bi 2 S 3 /Bi 2 Se 3 vdWHs anodes exhibit excellent performances of 208 and 106 Wh kg −1 over 850 and 3000 cycles, respectively, demonstrating their feasibility towards practical applications. Our study provides a new insight into architectural strategies for heterogeneous interfaces to realize intelligent kinetic control strategies of chalcogenide topological materials for advanced energy storage.

Cu3PS4: a sulfur-rich metal phosphosulfide with superior ionic diffusion channel for high-performance potassium ion batteries/hybrid capacitors

The emerging conversion-type chalcogenide anode materials for potassium ion storage may propose high theoretical specific capacity (>600 mA h g−1) and high compatibility with electrolytes, but currently the reported performance falls behind this goal due to severe material pulverization, polysulfide shuttle effect, and slow potassium ion diffusion during a charge/discharge process. Here, we report that Cu3PS4, a sulfur-rich orthorhombic metal phosphosulfide, can achieve highly reversible multiple conversion reactions, including the formation of KP and K2S along with 9 electrons transfer and efficient diffusion of potassium ions. Moreover, we introduce a layer graphite surface coating to enhance the overall conductivity of the electrodes, decrease the internal resistance, and render specific electronic channel with fast kinetic diffusion. During cycling, a tightly connected K-CuPS junctions were formed to establish an ultra-stable heterostructure to entrap polysulfides in materials via an appropriate and uniform affinity. In electrochemical tests, Cu3PS4 potassium ion anodes exhibit the highest capacity of 649.3 mA h g−1 at a current density of 0.05 A/g, reaching 94.4 % of its theoretical capacity (687.3 mA h g−1), and showed an ultra-stable 3000 cycle life and high-rate capability up to 8 A/g. Furthermore, the full battery and hybrid capacitor show attractive energy density and long cycle life of 82.5 W h kg−1 for 800 cycles and 80.3 W h kg−1 for 5000 cycles, respectively. This work provides promising results for metal phosphosulfide applications in high-efficiency potassium-ion storage devices, and may also be instructive for material advancements in related energy fields.

Construction of SnS-Mo-graphene nanosheets composite for highly reversible and stable lithium/sodium storage

• We report the simple synthesis of ternary SnS-Mo-GNs composite. • The composite has the structure of SnS nanoparticles tightly bonded with Mo and GNs. • The Mo and GNs function as dual buffer to suppress the Sn agglomeration during cycling. • The composite exhibits superior reversibility and cycleability for Li/Na-storage. Sn-based chalcogenides are considered as one of the most promising anode materials for lithium-ion batteries (LIBs) because of their high capacities through both conversion and alloying reactions. However, the realization of full capacities of Sn-based chalcogenides is mainly hindered by the large volume variation and inferior reversibility of conversion reaction during cycling. In present work, a new ternary SnS-Mo-graphene nanosheets (SnS-Mo-GNs) composite is fabricated by a simple and scalable plasma milling method, in which SnS nanoparticles are tightly bonded with Mo and GNs. The Mo and GNs additives can effectively alleviate the large volume change of SnS upon cycling, which leads to a stable electrochemical framework. Moreover, they can significantly suppress the Sn agglomeration in lithiated SnS, which enables highly reversible conversion reaction during cycling. As anode for LIBs, the SnS-Mo-GNs composite exhibits a high initial coulombic efficiency of 86.9% (almost complete reversibility of SnS, ∼97.3%), high cyclic coulombic efficiency after initial three cycles (> 99.5%), and long lifespan (up to 600 cycles). Moreover, it also demonstrates superior electrochemical performance for sodium storage. Thus, this work demonstrates a potential anode for batteries application and provides a viable strategy to obtain highly reversible and stable anodes for lithium/sodium storage.

From Copper to Basic Copper Carbonate: A Reversible Conversion Cathode in Aqueous Anion Batteries.

Dual-ion batteries that use anions and cations as charge carriers represent a promising energy-storage technology. However, an uncharted area is to explore transition metals as electrodes to host carbonate in conversion reactions. Here we report the reversible conversion reaction from copper to Cu2 CO3 (OH)2 , where the copper electrode comprising K2 CO3 and KOH solid is self-sufficient with anion-charge carriers. This electrode dissociates and associates K+ ions during battery charge and discharge. The copper active mass and the anion-bearing cathode exhibit a reversible capacity of 664 mAh g-1 and 299 mAh g-1 , respectively, and relatively stable cycling in a saturated mixture electrolyte of K2 CO3 and KOH. The results open an avenue to use carbonate as a charge carrier for batteries to serve for the consumption and storage of CO2 .

From Copper to Basic Copper Carbonate: A Reversible Conversion Cathode in Aqueous Anion Batteries

AbstractDual‐ion batteries that use anions and cations as charge carriers represent a promising energy‐storage technology. However, an uncharted area is to explore transition metals as electrodes to host carbonate in conversion reactions. Here we report the reversible conversion reaction from copper to Cu2CO3(OH)2, where the copper electrode comprising K2CO3 and KOH solid is self‐sufficient with anion‐charge carriers. This electrode dissociates and associates K+ ions during battery charge and discharge. The copper active mass and the anion‐bearing cathode exhibit a reversible capacity of 664 mAh g−1 and 299 mAh g−1, respectively, and relatively stable cycling in a saturated mixture electrolyte of K2CO3 and KOH. The results open an avenue to use carbonate as a charge carrier for batteries to serve for the consumption and storage of CO2.

Glyoxal‐Based Electrolytes in Combination with Fe2O3@C‐Based Electrodes for Lithium‐Ion Batteries

AbstractIn this study, we report for the first time about using glyoxal‐based electrolytes in combination with a Fe2O3@C‐based conversion type anode for application in lithium‐ion batteries (LIBs). We show that at room temperature (RT) the use of these alternative electrolytes is possible, but it is not more advantageous than that of the conventional LP30. At 60 °C, on the other hand, utilizing a glyoxal‐based electrolyte appears very promising since the Fe2O3@C‐based electrode, cycled in combination with 1 M LiTFSI in TEG:PC+2 % VC, displays a high specific capacity (800 mAh g−1) and a high stability over 500 cycles. X‐ray photoelectron spectroscopy (XPS) measurements indicate that these high performances are possible thanks to the generation of a thermally stable and thick SEI, which is particularly favorable for maintaining a highly reversible conversion reaction.

Insight into Reversible Conversion Reactions in SnO2 -Based Anodes for Lithium Storage: A Review.

Various anode materials have been widely studied to pursue higher performance for next generation lithium ion batteries (LIBs). Metal oxides hold the promise for high energy density of LIBs through conversion reactions. Among these, tin dioxide (SnO2 ) has been typically investigated after the reversible lithium storage of tin-based oxides isreported by Idota and co-workers in 1997. Numerous in/ex situ studies suggest that SnO2 stores Li+ through a conversion reaction and an alloying reaction. The difficulty of reversible conversion between Li2 O and SnO2 is a great obstacle limiting the utilization of SnO2 with high theoretical capacity of 1494mA h g-1 . Thus, enhancing the reversibility of the conversion reaction has become the research emphasis in recent years. Here, taking SnO2 as a typical representative, the recent progress is summarized and insight into the reverse conversion reaction is elaborated. Promoting Li2 O decomposition and maintaining high Sn/Li2 O interface density are two effective approaches, which also provide implications for designing other metal oxide anodes. In addition, some in/ex situ characterizations focusing on the conversion reaction are emphatically introduced. This review, from the viewpoint of material design and advanced characterizations, aims to provide a comprehensive understanding and shed light on the development of reversible metal oxide electrodes.

A Composite of Two Dimensional GeSe2 /Nitrogen-Doped Reduced Graphene Oxide for Enhanced Capacitive Lithium-Ion Storage.

A composite of two-dimensional (2D) GeSe2 nanosheets dispersed on N-doped reduced graphene oxide (GeSe2 /N-rGO) is fabricated via a simple hydrothermal method combined with post-selenization process. The high electronic conductivity and the substantial void spaces of the wrinkled N-rGO can improve the electrical conductivity of the active material and accommodate the volume evolution of GeSe2 nanosheets during the (de)lithiation processes, while GeSe2 nanosheets can reduce ion diffusion length effectively. Meanwhile, the unique layered structure is beneficial to the contact of the active material and electrolyte, and the reversibility of conversion reaction has also been improved. Furthermore, kinetics analysis reveals a pseudocapacitance-dominated Li+ -storage mechanism at high rates. In-situ X-ray diffraction analysis discloses that the conversion reaction has played a certain part in Li+ -storage. Thus, the GeSe2 /N-rGO composite delivers excellent rate capability and good long-term stability with a high reversible capacity of 711.0 mA h g-1 after 2000 cycles at 1 A g-1 .

Lithiophilic Nickel Phosphide Modifying Carbon Nanofibers for a Highly Reversible Lithium-Metal Anode

A lithium (Li)-metal battery with high energy density is the most promising system for the next-generation battery. However, detrimental Li dendrite growth induced by uneven Li deposition causes inferior Coulombic efficiency (CE) and infinite volumetric expansion of Li-metal anodes. Herein, a flexible carbon nanofiber membrane modified by nickel phosphide (Ni2P@CNF) is proposed as an effective 3D framework to guide Li deposition behaviors. Even and dense deposition of Li is observed via ex situ/in situ morphological observations, ascribed to the homogeneous Li nucleation on the lithiophilic Ni2P crystalline grains. The efficient utilization of Li is achieved benefiting from the synergistic reversible conversion reactions between Li and Ni2P and plating/stripping of Li. Moreover, the fibrous networks of Ni2P@CNF retain structural stability upon prolonged cycling. Thus, an average CE of 97.6% at 5 mA cm–2 is available. And an extended lifespan of 2000 h at 0.5 mA cm–2 for a symmetrical cell of Ni2P@CNF@Li and 1000 cycles at 5 C (1 C = 170 mA g–1) for a Li||LiFePO4 cell are attained, revealing the great potential of a practical Li-metal anode.

Synergistic Engineering of Sulfur Vacancies and Heterointerfaces in Copper Sulfide Anodes for Aqueous Zn‐Ion Batteries with Fast Diffusion Kinetics and an Ultralong Lifespan

AbstractAqueous Zn‐ion batteries (AZIBs) are promising candidates for implementing large‐scale energy storage, but the adverse side reactions and unsatisfactory cycle life brought by Zn‐metal anodes limit their potential in applications. Herein, an ingenious synthesized CuS1–x@polyaniline (PANI) is proposed as an attractive conversion‐type Zn‐metal‐free anode for AZIBs, in which appropriate S‐vacancies and PANI heterointerfaces can be simultaneously constructed. This “killing three birds with one stone” strategy stabilizes the anode structure by utilizing organic–inorganic heterointerfaces and enhances Zn2+ storage, benefiting from abundant S‐vacancies, as well as initiating fast Zn2+ transport kinetics based on the joint effect of the two. Operando X‐ray absorption fine structure and synchrotron X‐ray diffraction further reveal the highly reversible conversion reaction of CuS1–x@PANI via a distinct crystallization–amorphous transformation mechanism. These features endow CuS1–x@PANI with sufficient zinc‐ion storage capacity (215 mA h g−1 at 100 mA g−1) and reliable current abuse tolerance (154.3 mA h g−1 at 1 A g−1 after 1000 cycles). Moreover, when matched with the optimized ZnxMnO2 cathode, the full battery achieves a record‐high cycling performance of 10 000 cycles (80% capacity retention) at a superhigh current density of 10 A g−1. This study provides new opportunities for developing high‐performance rocking‐chair AZIBs.