Excellent Electronic Conductivity Research Articles

First-principles study on discharge electrochemical performance of layered two-dimensional FeS2 cathode

The electrochemical performance of the cathode material directly determines the energy density of the battery. The high cathode potential of the cathode increases the output voltage of the battery. The adsorption energy and the upper limit of Li+ adsorption by the cathode have significant effects on Li+ storage capacity. Li+ diffusion barrier in the cathode affects the charging and discharging efficiency. Cycle stability is determined by the reversibility of the cathode structure. Working potential window is related to the change of HOMO/LUMO during discharge. Appling the first-principles calculations, we explore the electrical properties, Li+ adsorption energy, Li+ diffusion barrier, working potential window, and theoretical capacity of layered 2D-FeS2 cathode during discharge. Layered 2D-FeS2 with excellent electronic conductivity accelerates conversion efficiency of electrons and holes with each other. 2D-FeS2 after discharge is 2D-Li2FeS2. Both of them have the same lattice structure P-3M1. The diffusion rate of Li+ is faster during the initial 2D-FeS2 discharge. Working potential window of layered 2D-FeS2 is 2.27 ∼ 1.81 V, the theoretical capacity is 893.56 mAh/g. The working potential of layered 2D-FeS2 increases with its LUMO/HOMO redox capacity. This work theoretically confirmed the reversibility of the structure of layered 2D-FeS2 after discharge and investigated its electrochemical properties.

Rapid production of kilogram-scale graphene nanoribbons with tunable interlayer spacing for an array of renewable energy

Graphene nanoribbons (GNRs) are widely recognized as intriguing building blocks for high-performance electronics and catalysis owing to their unique width-dependent bandgap and ample lone pair electrons on both sides of GNR, respectively, over the graphene nanosheet counterpart. However, it remains challenging to mass-produce kilogram-scale GNRs to render their practical applications. More importantly, the ability to intercalate nanofillers of interest within GNR enables in-situ large-scale dispersion and retains structural stability and properties of nanofillers for enhanced energy conversion and storage. This, however, has yet to be largely explored. Herein, we report a rapid, low-cost freezing-rolling-capillary compression strategy to yield GNRs at a kilogram scale with tunable interlayer spacing for situating a set of functional nanomaterials for electrochemical energy conversion and storage. Specifically, GNRs are created by sequential freezing, rolling, and capillary compression of large-sized graphene oxide nanosheets in liquid nitrogen, followed by pyrolysis. The interlayer spacing of GNRs can be conveniently regulated by tuning the amount of nanofillers of different dimensions added. As such, heteroatoms; metal single atoms; and 0D, 1D, and 2D nanomaterials can be readily in-situ intercalated into the GNR matrix, producing a rich variety of functional nanofiller-dispersed GNR nanocomposites. They manifest promising performance in electrocatalysis, battery, and supercapacitor due to excellent electronic conductivity, catalytic activity, and structural stability of the resulting GNR nanocomposites. The freezing-rolling-capillary compression strategy is facile, robust, and generalizable. It renders the creation of versatile GNR-derived nanocomposites with adjustable interlay spacing of GNR, thereby underpinning future advances in electronics and clean energy applications.

Template-free route to PEDOT nanofibers for 3D electrodes with ultrahigh capacitance and excellent cycling stability

The rapid growth of the electronics industry has increased the demand for electrochemical capacitors with a combination of high capacitance, high energy and power density, and long cycling stability. To achieve this, a rational design of electrode materials with high surface area, suitable porosity, and excellent electronic and ionic conductivity is required. Herein, high aspect ratio poly(3,4-ethylenedioxythiophene) (PEDOT) nano and microfibers with increased accessible surface area and porosity are grown on a three-dimensional laser-scribed graphene (LSG) network through a facile vapor phase polymerization process. The resultant electrode showed an outstanding areal capacitance of 1463 mF cm−2. To the best of our knowledge, this is the highest value reported so far for a vapor phase polymerized PEDOT/LSG supercapacitor. It also displayed an impressive capacitance retention of over 89.7% after 10,000 cycles at a current density of 30 mA cm−2 with a potential window of 1.0 V. Furthermore, the capacitive current contribution is a remarkable 96% with a maximum energy and power density of 75.21 µWh cm−2 and 136 mW cm−2, respectively. This binderless nanofiber composite electrode offers the advantages of better adhesion, improved specific surface area, suitable porosity, and enhanced electronic and ionic conductivity.

Topotactic conversion synthesis of Ta4+-doped TaO@C and its enhanced photocatalytic and lithium-ion battery performance

Carbon coated highly crystalline tantalum oxide (TaO@C) nanoparticles with self-doping Ta4+ and lattice oxygen were successfully prepared by via a topotactic conversion strategy by annealing polydopamine-coated (NH4)2Ta2O3F6 mesocrystals. TaO@C sample exhibits not only satisfactory photocatalytic performance on methylene blue (MB) degradation with a efficiency of 57.66% and 31.81% under ultraviolet and visible light illumination for 3 h, but also superior lithium storage properties with high reversible capacity, high rate capability (140 mAh g−1 at 1250 mA g−1) and outstanding cyclic stability (∼109 mAh g−1 at 1250 mA g−1 current density after 900 cycles with 0.01% capacity varying per cycle capacity retention)). It is primarily attributed to the synergistic effect among large surface area (42.61 m2·g−1), fine particle size (<60 nm), core-shell structure with tight carbon coating and porous structure, and defects, leading to excellent electronic conductivity and lower bandgap energy. Furthermore, surface pseudocapacitive makes great contribution on good rate capability.

Modulation of Hot Electrons via Interface Engineering of Au@ZnIn2S4/MXene for Efficient Photoelectrochemical Seawater Splitting under Visible Light

Interface engineering in hybrid plasmonic metal/semiconductor heterostructures is an efficient approach to enhance the catalytic performance of photocatalysts and photoelectrochemical cells in harvesting and converting sunlight, especially in the range of visible light. Plasmon-induced hot electron injection plays a crucial role in the transfer of plasmonic energy from a plasmonic metal to semiconductor in a plasmonic metal/semiconductor system. Herein, the efficient injection and utilization of hot electrons are achieved by fabrication of a Au@ZnIn2S4/Ti3C2 (Au@ZIS/Ti3C2) system, in which the core–shell Au@ZIS nanoparticles with well-defined interfaces are anchored on the 2D Ti3C2 surface. The core–shell Au@ZIS nanostructure is first constructed by a cation exchange reaction method. The well-defined interface of the Au core and ZIS shell optimizes the electron transfer pathway and greatly promotes the extraction of hot electrons from Au to ZIS. Furthermore, the electrons concentrated on ZIS can be further transferred to Ti3C2 owing to its excellent electron mobility and conductivity, leading to highly efficient separation and transfer of electrons through a two-step transfer process. The activities of photoelectrochemical (PEC) seawater splitting demonstrate that the integration of Au and ZIS into an optimized core–shell structure and its further modification by Ti3C2 results in a drastic improvement in PEC activity. Therefore, Au@ZIS/Ti3C2 shows the highest photocurrent density and smallest charge transfer resistance among various samples, accompanied by 6.5 and 10.8 orders of enhancement in PEC H2 evolution compared to reference samples of ZIS/Ti3C2 and Au/Ti3C2. Elaborate design and construction of core–shell plasmonic metal@semiconductor nanostructure with a well-defined interface and 2D MXene support would provide a feasible and promising method to enhance the performance of PEC seawater splitting.

Constructing a Strong Interfacial Interaction in a Rh/RGO Catalyst to Boost Photocatalytic Hydrogen Evolution under Visible Light Irradiation

Herein, we implanted the Rh2O3 nanoparticles (NPs) on the surface of reduced graphene oxide (RGO) by a hydrothermal reaction. After sensitized by Eosin Y, the Rh2O3 transferred into metal Rh to construct a strong interaction interface between Rh NPs and RGO. The fabricated Rh/RGO catalyst exhibited high performance for photocatalytic H2 evolution under visible light irradiation. About 98.1 mmol·g–1·h–1 H2 evolution rate was achieved with a maximum apparent quantum efficiency of 79.3% at 520 nm, which was superior to that of Rh (13.9 mmol·g–1·h–1) and Rh mixed with RGO (32.7 mmol·g–1·h–1) catalysts. The enhanced H2 evolution performance was attributed to the excellent electron conduction ability of RGO and the strong interaction between Rh NPs and RGO, which could accelerate the electron transfer and prolong the charge lifetime. In addition, the strong interaction could ensure the strong anchoring to maintain the excellent stability of the Rh/RGO catalyst. Our work will provide an avenue to design high-performance catalysts by fabricating a strong interfacial interaction strategy for photocatalytic H2 evolution.

Solvothermal synthesis of hybrid nanoarchitectonics nickel-metal organic framework modified nickel foam as a bifunctional electrocatalyst for direct urea and nitrate fuel cell

Urea and nitrate-based fuel cells have emerged as promising electricity generation devices. However, most of these catalysts are expensive and limited in supply, which limits their practical applications. Hence, metal-organic frameworks (MOF) have been explored as catalysts due to their low cost, easy preparation, and high redox activity. Here, we synthesize nickel-based MOF (Ni-MOF) via one-pot solvothermal technique as bifunctional electrocatalyst for the direct urea and nitrate fuel cell. The as-synthesized Ni-MOF is deposited on nickel foam (NF) and used as working electrode (Ni-MOF/NF) which demonstrates a peak current density of 188 mA/cm2 for urea oxidation reaction (UOR) and −14 mA/cm2 for nitrate reduction reaction (NRR) at an onset potential of ∼ 1.58 V (vs RHE), and ∼ 1.12 V (vs RHE), respectively The enhanced functionality of the Ni-MOF/NF electrode can be attributed to the high catalytic efficacy of the Ni-MOF. This is mainly due to the presence of multiple oxidation states of N (i.e., Ni2+/3+) and excellent electronic conductivity of the organic ligands in MOF structure. Moreover, Ni-MOF/NF electrodes retain ∼ 71.2% and ∼ 83.9% capacity after 20000 s of UOR and NRR, respectively. This efficacy of the as-fabricated electrocatalyst proves MOF as a promising platform for direct fuel cell applications.

Effectively morphology-controlled NiMn layered double hydroxide microflowers by conductive silver nanowires for supercapacitor electrodes

Effective ion and electron transport pathways provide an effective method to further improve the energy storage performance of layered double hydroxide (LDH) for supercapacitors. Here, microflower-like NiMn LDH/silver nanowires (Ag NWs) composites for high-performance supercapacitors are constructed by a convenient hydrothermal method, in which silver nanowires are found to not only ensure excellent electron conductivity but also have a positive effect on the growth of LDH nanosheets to form the unique three-dimensional open pore structure. In addition, the significantly increased interlayer spacing of the composite enables fast ion transport. In particular, NiMn LDH/Ag NWs exhibits higher specific capacitance (1436.30 F·g−1 at 2 A·g−1) in a three-electrode system, which is 121.29% of the specific capacitance of pure NiMn LDH. The asymmetric supercapacitor assembled with NiMn LDH/Ag NWs and AC electrode exhibits high specific capacitance of 215.63 F·g−1 at 2 A·g−1, superior energy density of 71.95 Wh·kg−1 and excellent cycling stability, illustrating that the NiMn LDH/Ag NWs composite is the promising material for supercapacitor applications.

Heterostructured plasmonic LaB6/TiO2 nanoparticles with enhanced photocatalytic degradation toward environmental remediation

Plasmonic lanthanum hexaborides hybrid with semiconducting TiO2 to form heterostructure is regard as an effective strategy to enhance the photocatalytic activity by local surface plasmonic resonance effect. In this work, we firstly present the plasmonic lanthanum hexaboride are coupled with TiO2 to fabricate the LaB6@TiO2 heterostructures via a simple sol-gel approach. Thanks to the excellent electron conductivity and local surface plasmonic resonance effect of LaB6, the optimized 5 wt%-LaB6@TiO2 heterostructures shows an enhancement in the photocatalytic degradation of both of rhodamine B and tetracycline. Specifically, the degradation efficiency of these two pollutants (20 mg/L) reaches to 95% and 92%, which are much greater than the degradation efficiency of pristine TiO2 and commercial TiO2 (P25), indicating that plasmonic LaB6 as co-catalysts effectively improve the electron-hole separation. Therefore, the plasmonic LaB6 assisted LaB6@TiO2 heterostructures with enhanced photocatalytic activity should have potential application for effective degradation of organic dyes and antibiotics.

Garnet-type solid-state mixed ionic and electronic conductor

Low ion and electron conductivities of the cathode and poor cathode interface performance severely limit the application of garnet solid-state batteries. While various approaches have been developed to improve the cathode interface contact or enhance ion and electron transport, none of these methods can simultaneously achieve high interfacial electrochemical activity and chemical stability. In this work, we propose to develop a single-phase garnet-type mixed ionic and electronic conductor (MIEC) as the cathode framework, which is expected to achieve the unification of high activity and high stability at the cathode interface. Combining first-principles calculations and ultrafast sintering techniques, we have synthesized and screened a series of garnet-type MIECs by introducing transition metals into garnet SSEs. Among the garnet-type MIECs, Li43Fe3La24Zr12Ta4O96 (3Fe) not only exhibits an excellent electronic conductivity of up to 2.87 × 10−4 S cm−1 but also maintains an ionic conductivity of 4.57 × 10−5 S cm−1. The high electronic conductivity is believed to originate from the high-temperature reduction phase formed during the rapid sintering process under inert conditions. A small polaron hopping mechanism is proposed to explain the electronic conductivity based on electronic structure calculations and activation energy analysis. Since garnet-type MIECs have the same crystal structure as garnet solid-state electrolytes (SSEs) and transition metal elements similar to those of oxide cathode materials, they potentially have good cosintering stability with both electrolytes and cathodes. This work provides a new strategy to solve the cathode interface problem in garnet solid-state batteries.

Effect of sulfurized polyacrylonitrile-g-rGO composition on the specific capacity and cycling stability of lithium sulfur batteries

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for the commercialization of lithium-sulfur batteries with extremely stable cycling performance. However, its inherent low sulfur content and poor electrical conductivity severely impairs its electrochemical performance. In this work, we construct a sulfur cathode in the form of a unique bamboo-shaped structured nanofiber, using SPAN as the bamboo stalk and reduced graphene oxide (rGO) as the bamboo joint, thus ensuring that the SPAN has excellent electronic conductivity. Polyacrylonitrile grafted with rGO (PAN-g-rGO) is an effective composite of ultra-high molecular weight PAN (UHMW PAN) and rGO at the molecular level. The UHMW PAN precursor can provide high sulfur loading, and the bamboo joint-like rGO can offer short-range accelerated electron transfer, thus effectively enhancing the electrochemical performance of the battery. Sulfurized PAN-g-rGO fiber (SFPAN-g-rGO) with a sulfur content of approximately 53 wt% is fabricated using PAN-g-rGO with a molecular weight of 3.6 × 105 Da as the precursor. The battery has a high reversible specific capacity (1463 mAh g−1 at 0.2C), excellent C-rate performance (1239 mAh g−1 at 2C), and good cycling stability (guaranteed over 800 cycles). In addition, the electrode offers a high reversible specific capacity of 1383 mAh g−1 at 0.1C and 1280 mAh g−1 at 0.2C when tested under a lean electrolyte (E/S: 10 μL mg−1) and high mass loading (4.8 mg cm−2), thus illustrating its good development potential.

A hierarchical SiO2-microsphere-graphene host enabling superior long-term cycling for lithium-metal anodes

Metallic lithium (Li) is considered to be one of the most promising anodes for Li-ion batteries due to its high theoretical capacity and low reduction potential. However, dendritic growth and substantial volume variations during battery operation make it difficult for commercialization. Here, a graphene and SiO2 composites material was presented as a lithiophilic host to enable superior long-term cycling for Li-metal anode. The porous skeleton of graphene with excellent electronic conductivity can effectively reduce the actual current density and suppress the volume expansion. And the SiO2 particles with excellent ionic conductivity can significantly suppress the growth of Li dendrites and regulate the nucleation sites. So doping SiO2 nanoparticles between graphene sheets can significantly suppress the growth of Li dendrites and the volume expansion effect of metallic Li deposition, while also providing good electrochemical performance. Benefitting from these synergistic effects, the Li-GF@SiO2 battery exhibits excellent electrochemical reversibility over 500 cycles depositing 1 mAh cm−2 of metallic Li at a current density of 1 mA cm−2, and the coulombic efficiency of the Li-GF@SiO2 battery is still as high as 97%, but the Li-Cu battery decays after 75 cycles. So this hierarchical SiO2-microsphere-graphene host demonstrates great potential for Li batteries.

Facile and effective defect engineering strategy boosting ammonium vanadate nanoribbon for high performance aqueous zinc-ion batteries

Vanadium-based oxides have gained widespread attention as promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their abundant valences, high theoretical capacity and low cost. However, the intrinsic sluggish kinetics and unsatisfactory conductivity have severely hampered their further development. Herein, a facile and effective defect engineering strategy was developed at room temperature to prepare the defective (NH4)2V10O25·8H2O (d-NHVO) nanoribbon with plenty of oxygen vacancies. Owing to the introduction of oxygen vacancies, the d-NHVO nanoribbon possessed more active sites, excellent electronic conductivity and fast ion diffusion kinetics. Benefiting from these advantages, the d-NHVO nanoribbon as an aqueous zinc-ion battery cathode material exhibited superior specific capacity (512 mAh g−1 at 0.3 A g−1), excellent rate capability and long-term cycle performance. Simultaneously, the storage mechanism of the d-NHVO nanoribbon was clarified via comprehensive characterizations. Furthermore, the pouch battery based on the d-NHVO nanoribbon was fabricated and presented eminent flexibility and feasibility. This work provides a novel thought for simple and efficient development of high- performance vanadium-based oxides cathode materials for AZIBs.

Facile preparation of conductive carbon-based membranes on dielectric substrates.

Graphene has attracted much research attention due to its outstanding chemical and physical properties, such as its excellent electronic conductivity, making it as a useful carbon material for a variety of application fields of photoelectric functional devices. Herein, a new method for synthesizing conductive carbon membranes on dielectric substrates via a low-temperature thermodynamic driven process is developed. Although the obtained films exhibit low crystallinity, their electrical, wetting, and optical properties are acceptable in practice, which opens up a new avenue for the growth of carbon membranes and may facilitate the applications of transparent electrodes as potential plasma-free surface-enhanced Raman scattering (SERS) substrates.

Nickel sulfide/nickel phosphide heterostructures anchored on porous carbon nanosheets with rapid electron/ion transport dynamics for sodium-ion half/full batteries

Nickel-based materials have been extensively deemed as promising anodes for sodium-ion batteries (SIBs) owing to their superior capacity. Unfortunately, the rational design of electrodes as well as long-term cycling performance remains a thorny challenge due to the huge irreversible volume change during the charge/discharge process. Herein, the heterostructured ultrafine nickel sulfide/nickel phosphide (NiS/Ni2P) nanoparticles closely attached to the interconnected porous carbon sheets (NiS/Ni2P@C) are designed by facile hydrothermal and annealing methods. The NiS/Ni2P heterostructure promotes ion/electron transport, thus accelerating the electrochemical reaction kinetics benefited from the built-in electric field effect. Moreover, the interconnected porous carbon sheets offer rapid electron migration and excellent electronic conductivity, while releasing the volume variance during Na+ intercalation and deintercalation, guaranteeing superior structural stability. As expected, the NiS/Ni2P@C electrode exhibits a high reversible specific capacity of 344 mAh g−1 at 0.1 A g−1 and great rate stability. Significantly, the implementation of NiS/Ni2P@C//Na3(VPO4)2F3 SIB full cell configuration exhibits relatively satisfactory cycle performance, which suggests its widely practical application. This research will develop an effective method for constructing heterostructured hybrids for electrochemical energy storage.

Two-dimensional CrP2 with high specific capacity and fast charge rate for lithium-ion battery

The electrode material is regarded as one of the key factors that determine the performance of lithium-ion batteries (LIBs). However, it is still a challenge to search for an anode material with large capacity, low diffusion barrier, and good stability. In the present work, two new CrP2 monolayers (Pmmn-CrP2 and Pmma-CrP2) are predicted by means of first principles swarm structure search. Our study shows that both the two CrP2 monolayers have high dynamical and thermal stability, as well as excellent electron conductivity. Additionally, Pmmn-CrP2 exhibits a remarkably high storage capacity of 705 mA⋅h⋅g−1 for Li, meanwhile the diffusion energy barrier of Li on the surface of this monolayer is 0.21 eV, ensuring it as a high-performance anode material for LIBs. We hope that our study will inspire researchers to search for new-type two-dimensional (2D) transition metal phosphides for the electrode materials of LIBs.

Hydrogel-derived nitrogen-doped porous carbon framework with vanadium nitride decoration for supercapacitors with superior cycling performance

Transition metal nitrides (TMNs) and their composites with carbon materials hold tremendous potential for supercapacitor (SC) electrodes because of their excellent electronic conductivity and electrochemical activity. However, realizing cycling stable TMN/carbon-based supercapacitors with economically viable and environmentally-friendly approaches remains a significant challenge. Significantly, polyacrylamide (PAM) hydrogel, as a water-soluble linear polymer electrolyte, is expected to be a remarkable candidate precursor for preparing N-doped porous carbon (NPC) due to the high contents of carbon and nitrogen elements. In this study, vanadium nitride (VN) embedded in PAM hydrogel-derived NPC was fabricated successfully via an ammonia-free process. The VN/NPC delivers a high specific capacitance of 198.3 F g−1 at a current density of 1 A g−1, with a remarkable cycling stability of 107% after 16,000 cycles. The electrochemical performances of VN/NPC compared to bare VN nanoparticles are strongly improved due to the composite structure. Additionally, the VN/NPC-based solid-state symmetric device delivers an excellent energy density of 21.97 µWh cm−2 at a power density of 0.5 mW cm−2, and an outstanding cycling durability of 90.9% after 18,000 cycles. This work paves the way to design metal nitride/porous carbon materials, which also opens up unique horizons for the recovery of hydrogel electrolyte.

A Laser-Processed Carbon-Titanium Carbide Heterostructure Electrode for High-Frequency Micro-Supercapacitors.

Micro-supercapacitors (MSCs) are an important energy storage component for future miniaturized electronic systems, yet their key performance indexes such as high-frequency response, energy density, and cycle life still have a large room to be improved. Herein, a laser-processed carbon-titanium carbide heterostructure (LCTH) electrode is demonstrated, which can excellently address the above key challenges by employing a unique one-step laser-processing fabrication method. Different from the other reported electrode structures, this LCTH electrode shows a heterogeneous structure, featuring the carbon nanofoam layer which provides extremely short ion transport channels and abundant electrochemical active sites, and the underlying titanium carbide layer which can provide excellent electron conductivity and contribute to the pseudo-capacitance. The assembled symmetric supercapacitor can stably work at the voltage window of 3.5V at an ultra-high frequency of approximately 1121.3Hz, exhibiting an ultra-high areal specific energy density of 721 µFV2 cm-2 at 120Hz and a cycle life of 140 000 cycles with capacitance retention of 100.95%, which is superior to most reported MSCs. The as-fabricated MSC is compatible with the contemporary embedded electronic component fabrication processes, which shows significant advantages in large-scale fabrication and system integration, demonstrating a broad prospect for future system-in-package applications.

Detailed Study of Sulfur Poisoning and Recovery of Ni-YSZ-Based Anodes Operating up to 1.8 W cm-2 in a Biogas Fuel

Ni-YSZ (nickel-yttrium-stabilized zirconia) is a common anode for solid oxide fuel cells (SOFCs) because of its excellent catalytic performance and electronic conductivity. It shows that the nickel anode-supported cell exhibits good cell performance in a biogas fuel of 36CH4-36CO2-20H2O-4H2-4CO. Unfortunately, natural biogas fuels often contain sulfur, so using nickel anodes is not always straightforward. This paper investigates the sulfur poisoning and the recovery of BaCe0.7Zr0.1Y0.1Yb0.1O3-δ- (BCZYYb-) (Ce, Y, and Yb codoped barium zirconate) impregnated nickel anode-supported cells operating up to 1.8 W cm-2 in the biogas. The in situ gas analysis reveals that the suppression of the reforming reactions might cause sulfur poisoning in a 4 ppm (v) H2S (hydrogen sulfide) in open circuit conditions, whereas the current degradation in working conditions could be attributed to the deactivation of reforming reactions and catalyst activity. The incidence of water-gas shift reactions is associated with the degradation rate of these two reactions. After removing the H2S, the recovery is accelerated by a steam hydrogen fuel, indicating that steam facilitates the efficient release of sulfur from nickel sites.

Optimized TiO Subcompounds and Elastic Expanded MXene Interlayers Boost Quick Sodium Storage Performance

AbstractTo develop quick‐charge sodium‐ion battery, it is significant to optimize insertion‐type anode to afford fast Na+ diffusion rate and excellent electron conductivity. First‐principles calculations reveal the TiO subcompound superiority for Na+ diffusion following Ti(II)O &gt; Ti(III)O &gt; Ti(IV)O. Hence, in situ growth of amorphous TiO subcompounds with rich oxygen defects based on Ti3C2Tx‐MXene is developed. Meanwhile, the composite presents expanded MXene interlayer spacing and much enhanced conductivity. The synergistic effect of enhanced electron/ion conduction gives a high capacity of 107 mAh g−1 at 50 A g−1, which gives 50% and 150% increasements compared with one counterpart without valence adjustment and another one without MXene expansion. It only needs 20 s (at 30 A g−1) to complete the discharge/charge process and obtains a capacity of 144.5 mAh g−1, which also shows a long‐term cycling stability at quick‐charge mode (121 mAh g−1 after 10000 cycles at 10 A g−1). The enhanced performance comes from fast electron transfer among TiO subcompounds contributed by rich‐defect amorphous TiO2–x, and a reversible change of elastic MXene with interlayer spacing between 1.4 and 1.9 nm during Na+ insertion/extraction process. This study provides a feasible route to boost the kinetics and develop quick‐charge sodium‐ion battery.