Excellent Rate Capability Research Articles

Oxalate and adipate mediated fabrication of CuO nanocrystallites for their electrochemical and supercapacitance studies

Cupric oxide (CuO) has been comprehensively studied in the field of electrochemistry due to its high Tc-Superconducting property. The present work focus on two different CuO materials i.e. CuO-1 and CuO-2 nanocrystallites which are successfully synthesized from their oxalate and adipate precursors respectively. The calcination temperature for the synthesis of CuO from their precursors is ascertained by TGA analysis of the dicarboxylates. Both the CuO materials are thoroughly characterized by SEM–EDS, XRD, IR and XPS spectroscopic techniques. As a candidate for supercapacitor electrode material, CuO-1/C and CuO-2/C showed a specific capacitance of 4.15 F/g and 22.24 F/g using cyclic voltammetry, 10.4 F/g and 46.6 F/g using GCD curves respectively at a current density of 1 A/g. Also, the CuO-1/C and CuO-2/C showed a specific energy density (Es) 1.59 Wh kg−1 and 0.36 Wh kg−1 at a specific power density (Ps) of 0.02 kW kg−1 and 0.025 kW kg−1 respectively. Moreover, the CuO-2/C exhibits ≈ 96.1% coulombic efficiency following 1000 cycles, whereas, CuO-1/C lags in coulombic efficiency with only 51.8%. As a better candidate, CuO-2/C exhibited excellent rate capability with an outstanding cycling stability of 93.7% retention after 1,000 cycles. The factors contributing to the significant specific capacitance of CuO-2/C along with better stability and reproducibility are its low electrolyte resistance Rs (2.47Ω) and charge transfer resistance Rct (1.01 Ω).

3D Printing of Tungstate Anion Modulated 1T‐MoS2 Composite Cathodes for High‐Performance Lithium–Sulfur Batteries

AbstractLithium–sulfur (Li–S) batteries can offer high capacity and energy‐density, but face challenges like low conductivity, lithium polysulfides (LiPSs) shuttling, and limited reaction kinetics. In this study, the electronic configuration of Mo 4d orbital in MoS2 is modulated through a one‐step method involving tungstate anion (WO42−) modulation to form a stable 1T‐MoS2/carbon composite (1T‐W‐MoS2/C). When WO42− is introduced, it causes a transfer of electrons to Mo in 2H‐MoS2, resulting in the generation of a stable 1T phase. In the composite, 1T‐MoS2 nanosheets exhibit remarkable electronic conductivity, hydrophilicity, and catalytic activity, facilitating the LiPSs adsorption and Li+ transport. Meanwhile, the WO42− modulation can create abundant adsorption/catalytic sites with defects on the basal surface and edges of MoS2, facilitating the efficient catalysis of LiPSs conversion. Furthermore, the 3D‐printed electrodes without utilization of binders and current collectors can ensure high mass loading and promote ion diffusion and electrolyte penetration. Theoretical and experimental results confirm that 1T‐W‐MoS2/C can catalyze LiPSs conversion, suppress LiPSs shuttling, and enhance sulfur reaction kinetics. Therefore, the 3D‐printed 1T‐W‐MoS2/C/S cathode exhibits a high initial capacity and excellent rate capability, achieving an areal capacity of 7.37 mAh cm−2 with a sulfur loading of 8.89 mg cm−2.

Metal alkoxides: A new type of reversible anode materials for stable and high-rate lithium-ion batteries

Metal-organic compounds have attracted significant attention for lithium-ion battery (LIB) anodes. However, their practical application is severely hindered by the poor structural stability and sluggish Li+ reaction kinetics. Herein, we proposed a new type of metal–organic compound, metal alkoxides, for high-performance LIBs. A series of metal-alkoxide/graphene composites with different transition metal centers and alkoxide anions are prepared to investigate the structural stability, Li-storage ability, and Li+ diffusion kinetics. The results reveal that the metal centers and alkoxide anions have significant influence on the structural stability, molar mass, and electronic structures, which are highly related to the Li-storage performance. Among them, Co-EG/rGO (EG represents the ethylene glycol anion) delivers the best performance involving high specific capacity (975 mAh g−1 at 0.2 A g−1), excellent rate capability (400.8 mAh g−1 at 10 A g−1), and stable cycling performance (86.8 % capacity retention after 600 cycles) due to its stable structure, smaller molar mass, and favorable electronic structure. Moreover, the Li-storage mechanism and solid electrolyte interphase (SEI) evolution of the Co-EG/rGO electrode are studied in detail through multiple ex-situ/in-situ characterizations. This work provides a new type of metal alkoxide anode material for high-rate and long-life LIBs toward practical energy applications.

"Lasagna"-Structured SnS-TaS2 Misfit Layered Sulfide for Capacitive and Robust Sodium-Ion Storage.

Stannous sulfide (SnS), a conversion-alloying type anode for sodium-ion batteries, is strong Na+ storage activity, a low voltage platform, and high theoretical capacity. However, grain pulverization induced by intolerable volume change and phase aggregation causes quick capacity degradation and unsatisfactory rate capability. Herein, a novel "lasagna" strategy is developed by embedding a SnS layer into the interlayer of an electrochemically robust and electron-active TaS2 to form a misfit layered (SnS)1.15TaS2 superlattice. For Na+ storage, the rationally designed (SnS)1.15TaS2 anode exhibits high specific capacity, excellent rate capability, and robust cycling stability (729 mAh cm-3 at 15 C after 2000 cycles). Moreover, the as-assembled (SnS)1.15TaS2 || Na3V2(PO4)3 full cells achieve robust and fast Na+ storage performance with ≈100% capacity retention after 650 cycles at 15 C, which also demonstrates good low-temperature performance at -20°C with a capacity retention of 75% and 2 C high-rate charge/discharge ability.

Boosting proton intercalation via sulfur anion doping in V2O3 cathode materials towards high capacity and rate performance of aqueous zinc ion batteries

Aqueous zinc-ion batteries (ZIBs) are a prospective solution for grid-scale energy storage. V2O3 has emerged as a promising cathode candidate with reversible two-electron redox capability for ZIBs. However, it still faces problems such as poor electronic conductivity and sluggish ion embedding kinetics. Herein, we report sulfur anion-doped V2O3 with tunneled structure based on a facile carbothermal reduction method, which can exhibit the significant impact of sulfur anion-doping on proton storage in vanadium-based cathode materials for high capacity and rate performance of ZIBs. The covalent bonds in S-V-O lead to accelerated charge transfer and elevated electronic conductivity. In-situ X-ray diffraction, synchrotron-based X-ray absorption spectroscopy combined with DFT calculations demonstrate that S doping effectively diminishes the adsorption and embedding energies of H+ in V2O3 and greatly boosts proton insertion kinetics. The co-intercalation of H+/Zn2+ helps compensate for the deficiency of Zn2+ insertion/extraction kinetics. Amorphous transition of crystalline V2O3 initiated from initial charging is conducive to mitigating stress and retaining stable cycling capacity. The typical sulfur-doped V2O3 achieves remarkable capacity (470.4 mAh·g−1 at 0.5 A·g−1), excellent rate capability (264.6 mAh·g−1 at 10 A·g−1) and stable long-term cyclability (231.2 mAh·g−1 at 10 A·g−1 after 2000 cycles). Furthermore, the corresponding pouch cells can deliver 26 mAh at 1 A·g−1 after 250 cycles, holding great potential for practical applications.

Tuning the microstructure of biomass-derived hard carbons by controlling the impurity removal process for enhanced Na ion storage performance

Biomass-derived hard carbons are promising anode materials of sodium-ion batteries (SIBs) due to their low cost, renewability and high specific capacity. However, there are inevitably some impurities in biomasses that may not only affect the purity, but microstructure and electrochemical performance of hard carbons. Although the impurities can be removed by appropriate treatments after carbonization, the microstructure of hard carbons can hardly be changed. In this work, taking ficus macrophylla leaves (FMLs) as the model biomass, the effects of impurities and their removing process on the microstructure and Na ion storage performance of hard carbons are investigated. It is found that the presence of Ca and Si-bearing impurities in FMLs results in more graphite-like structure in hard carbons because of their catalytic graphitization effect. The acid and base washing processes after carbonization can mostly get rid of the inorganic impurities is unable to increase the plateau region capacities associating to Na ion insertion in the interlayer of graphitic microcrystals and Na metal filling in micropores. By contrast, by stepwisely removing the Ca and Si-bearing impurities from raw materials before carbonization, hard carbons with high purity, larger interlayer space and more micropores are produced, which exhibit a high reversible specific capacity of 336 mAh g−1 at 20 mA g−1, a high initial Coulombic efficiency of 93 %, excellent rate capability (245 mAh g−1 at 2 A g−1) and robust cycle stability. This study implies that controlling the impurity removal process can simultaneously tune the microstructure of hard carbon anodes derived from biomasses towards high performance Na ion storage.

A Highly Reversible Sn‐Air Battery Possessing the Ultra‐Low Charging Potential with the Assistance of Light

AbstractAqueous Sn‐air batteries are attracting a great deal of interest in recent years due to the ultra‐high safety, low cost, dendrite‐free and highly reversible Sn anode. However, the slurry oxygen reduction/evolution reaction (ORR/OER) kinetics on the air cathodes seriously affect the Sn‐air battery performances. Although various advanced catalysts have been developed, the charge overpotentials (~1000 mV) of these Sn‐air batteries are still not satisfactory. Herein, iron oxide (Fe2O3) modified titanium dioxide (TiO2) nanorods with heterogeneous structure are firstly synthesized on Ti mesh (Fe2O3@TiO2/Ti), and the obtained Fe2O3@TiO2/Ti films are further applied as catalytic electrodes for Sn‐air batteries. The core–shell heterogeneous structure of Fe2O3@TiO2/Ti can effectively facilitate the conversion of electrochemical intermediates and separation of photo‐excited electrons and holes to activate oxygen‐related reaction processes. Density functional theory (DFT) and experimental results also confirm that Fe2O3@TiO2/Ti can not only act as the electrocatalysts to improve ORR/OER properties, but also exhibit the superior photo‐catalytic activity to promote charging kinetics. Hence, the Fe2O3@TiO2/Ti‐based Sn‐air batteries show ultra‐low overpotential of ~40 mV, excellent rate capability and good cycling stability under light irradiation. This work will shed light on rational photo‐assisted catalytic cathode design for new‐type metal‐air batteries.

A Highly Reversible Sn-Air Battery Possessing the Ultra-Low Charging Potential with the Assistance of Light.

Aqueous Sn-air batteries are attracting a great deal of interest in recent years due to the ultra-high safety, low cost, dendrite-free and highly reversible Sn anode. However, the slurry oxygen reduction/evolution reaction (ORR/OER) kinetics on the air cathodes seriously affect the Sn-air battery performances. Although various advanced catalysts have been developed, the charge overpotentials (~1000 mV) of these Sn-air batteries are still not satisfactory. Herein, iron oxide (Fe2O3) modified titanium dioxide (TiO2) nanorods with heterogeneous structure are firstly synthesized on Ti mesh (Fe2O3@TiO2/Ti), and the obtained Fe2O3@TiO2/Ti films are further applied as catalytic electrodes for Sn-air batteries. The core-shell heterogeneous structure of Fe2O3@TiO2/Ti can effectively facilitate the conversion of electrochemical intermediates and separation of photo-excited electrons and holes to activate oxygen-related reaction processes. Density functional theory (DFT) and experimental results also confirm that Fe2O3@TiO2/Ti can not only act as the electrocatalysts to improve ORR/OER properties, but also exhibit the superior photo-catalytic activity to promote charging kinetics. Hence, the Fe2O3@TiO2/Ti-based Sn-air batteries show ultra-low overpotential of ~40 mV, excellent rate capability and good cycling stability under light irradiation. This work will shed light on rational photo-assisted catalytic cathode design for new-type metal-air batteries.

Highly Crystalline Multivariate Prussian Blue Analogs via Equilibrium Chelation Strategy for Stable and Fast Charging Sodium-Ion Batteries.

Prussian blue analogs (PBAs) have been widely recognized as superior cathode materials for sodium-ion batteries (SIBs) owing to numerous merits. However, originating from the rapid crystal growth, PBAs still suffer from considerable vacancy defects and interstitial water, making the preparation of long-cycle-life PBAs the greatest challenge for its practical application. Herein, a novel equilibrium chelation strategy is first proposed to synthesize a high crystallinity (94.7%) PBAs, which is realized by modulating the chelating potency of strong chelating agents via "acid effect" to achieve a moderate chelating effect, forcefully breaking through the bottleneck of poor cyclic stability for PBAs cathodes. Impressively, the as-prepared highly crystalline PBAs represent an unprecedented level of electrochemical performance including ultra-long lifespan (10000 cycles with 86.32% capacity maintenance at 6Ag-1), excellent rate capability (82.0mAhg-1 at 6Ag-1). Meanwhile, by pairing with commercial hard carbon, the as-prepared PBAs-based SIBs exhibit high energy density (350Whkg-1) and excellent capacity retention (82.4% after 1500 cycles), highlighting its promising potential for large-scale energy storage applications.

Dual Strategy of Morphology Optimization and Interlayer Expansion in VS2 Cathode Toward High-Performance Mg-Li Hybrid Ion Batteries.

Combining the merits of the dendrite-free formation of a Mg anode and the fast kinetics of Li ions, the Mg-Li hybrid ion batteries (MLIBs) are considered an ideal energy storage system. However, the lack of advanced cathode materials limits their further practical application. Herein, we report a dual strategy of morphology optimization and interlayer expansion for the construction of hierarchical flower-like VS2 architecture coated by N-doped amorphous carbon layers. This tailored hierarchical flower-like structure coupled with homogeneous N-doped amorphous carbon layers cooperatively provide more active sites and buffer volume changes, thus realizing the enhancement of capacity and structural stability. Moreover, the enlarged interlayer spacing caused by the cointercalation of polyvinylpyrrolidone and ammonium ions can effectively promote the charge transfer rate and facilitate the rapid ion diffusion, as further demonstrated by electrochemical results and theoretical calculations. These features endow the hierarchical flower-like VS2 cathode with superior specific energy density (644.4 Wh kg-1, average voltage of 1.2 V vs Mg2+/Mg) and excellent rate capability (181.1 mAh g-1 at 2000 mA g-1). Systematic ex situ characterization measurements are employed to reveal the ion storage mechanism, which confirms that Li+ storage plays a leading role in the capacity contribution of MLIBs. Our strategy is in favor of providing useful insights to design and construct MLIBs with high energy density and excellent rate performance.

Flexible self‐supporting organic cathode with interface engineering for high‐performance and wide‐temperature sodium‐ion batteries

AbstractFlexible electrode design with robust structure and good performance is one of the priorities for flexible batteries to power emerging wearable electronics, and organic cathode materials have become contenders for flexible self‐supporting electrodes. However, issues such as easy electrolyte solubility and low intrinsic conductivity contribute to high polarization and rapid capacity decay. Herein, we have designed a flexible self‐supporting cathode based on perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA), interfacial engineering enhanced by polypyrrole (PPy), and carbon nanotubes (CNTs), forming the interconnected and flexible PTCDA/PPy/CNTs using polymerization reaction and vacuum filtration methods, effectively curbing those challenges. When used as the cathode of sodium‐ion batteries, PTCDA/PPy/CNTs exhibit excellent rate capability (105.7 mAh g−1 at 20 C), outstanding cycling stability (79.4% capacity retention at 5 C after 500 cycles), and remarkable wide temperature application capability (86.5 mAh g−1 at −30°C and 115.4 mAh g−1 at 60°C). The sodium storage mechanism was verified to be a reversible oxidation reaction between two Na+ ions and carbonyl groups by density functional theory calculations, in situ infrared Fourier transform infrared spectroscopy, and in situ Raman spectroscopy. Surprisingly, the pouch cells based on PTCDA/PPy/CNTs exhibit good mechanical flexibility in various mechanical states. This work inspires more rational designs of flexible and self‐supporting organic cathodes, promoting the development of high‐performance and wide‐temperature adaptable wearable electronic devices.

Towards practical Li-ion full batteries with glass anodes

Vanadium (V)-based glasses have recently garnered considerable attention as promising anode materials for lithium-ion batteries (LIBs) due to their abundance of Li+ storage sites, neglectable volume expansion upon lithiation/delithiation, and facile preparation. However, the inherently low electronic conductivity and relatively low energy density of V-based glass anodes hinder its application in full LIBs. In this work, we tackled this challenge by optimizing the chemical composition of the V-based glass anode to achieve high-performance half and full cells. We investigated the impact of partially substituting B2O3 for P2O5 in 50V2O5-(50-x)P2O5-xB2O3 (mol%) (VPB) glass series on its structure and electrochemical performances. The glass with 30 mol% B2O3 (VPB30 glass) was found to deliver the highest electronic conductivity, an enhanced reversible capacity of 470 mA h g−1 at 1 A g−1 after 500 cycles, and an excellent rate capability. The optimized performances were ascribed to the boosted lithium-ion diffusivity and the increased lithium storage sites. We assembled a full cell by coupling a VPB30 glass anode with a LiCoO2 cathode to test its cycling performance. The VPB30//LiCoO2 cell exhibits the required power density, and hence, high practicality. Our work implied the practical application of glass anodes in high-performance LIBs.

Boosting the intercalation reaction of FeOF-based cathode toward highly reversible lithium storage

FeOF as an intercalation-conversion cathode features a high theoretical capacity toward high energy density lithium-ion batteries (LIBs). However, the inadequate intercalation process and poor reversibility of redox reaction deteriorate its practical capacity and cycling stability. Herein, a S-substitution strategy in FeOF (FeOF-S) is proposed to boost the intercalation reaction and enhance the reaction kinetics, achieving a record-high capacity of 668 mAh g−1 at 0.05 A g−1 and a long cycling stability up to 1500 cycles at 0.5 A g−1. Under this strategy, the Li+ intercalation energy of FeOF-S is remarkably reduced in thermodynamics, promoting the intercalation capacity to 230 mAh g−1 which is 50% higher than that of FeOF. Furthermore, a nearly zero band gap with superior electronic conduction is achieved in FeOF-S, leading to excellent rate capability with much enhanced pseudo-capacitance contribution. This work presents new insights into the regulation of thermodynamics and kinetics toward the boosted electrochemical performance of conversion-type electrodes for high energy density LIBs.

KOH-activated hollow carbon spheres with surface functionalization for high-capacity and long-cycle-life lithium-selenium batteries

Lithium-selenium (Li-Se) batteries are considered promising alternatives to lithium-ion batteries due to their higher volumetric capacity and energy density. However, they still face limitations in efficiently utilizing the active selenium. Here, we develop surface-functionalized mesoporous hollow carbon nanospheres as the selenium host. By using KOH activation, the surface of the carbon nanospheres is functionalized with hydroxyl groups, which greatly improve the utilization of selenium and facilitate the conversion of lithium selenides, leading to much higher capacities compared to ZnCl2 activation and untreated carbon nanospheres. Theory and experimental evidence suggest that surface hydroxyl groups can enhance the reduction conversion of polyselenides to selenides and facilitate the oxidation reaction of selenides to elemental selenium. In-situ and ex-situ characterization techniques provided additional confirmation of the hydroxyl groups electrochemical durability in catalyzing selenium conversion. The meticulously engineered Se cathode demonstrates a high specific capacity of 594 mA h g−1 at 0.5C, excellent rate capability of 464 mA h g−1 at 2C, and a stable cycling performance of 500 cycles at 2C with a capacity retention of 84.8 %, corresponding to an ultra-low-capacity decay rate of 0.0144 % per cycle, surpassing many reported lithium-selenium battery technologies.

Developing a high-performance hybrid supercapacitor with the controlled assembly of a hierarchical 3D flower-like NiCo double hydroxide nano/microarchitecture electrode material

The design of hierarchical nano/microarchitectures containing multiple elemental compositions has attracted significant interest due to their ability to offer morphological, enhanced conductive, and exceptional electrochemical capabilities in the field of energy storage. Herein, a 3D flower-like porous nano/microarchitecture of NiCo double hydroxide (NCDH-1) was synthesized using a facile hydrothermal technique for supercapacitor electrode materials. The 3D hierarchical structure formed by the network arrangement of 2D nanosheets comprises of many open spaces between the nanosheets. These nanosheets lead to a large specific surface area, abundant active sites, and multiple channels for the transport of electrons/ions. These factors boost redox processes and facilitate the rapid transfer of electrons/ions into the electrode material. The NCDH-1 electrode material, with its hierarchical 3D nano/microarchitecture, exhibits the supreme capacitance (Csp) of 2199 F g−1 at 1 A g−1 and demonstrates excellent rate capability, retaining 58.2 % at 20 A g−1. The hybrid supercapacitor configured using 3D flower-like NCDH-1 and commercial grade activated carbon (AC; MSP-20) electrodes demonstrates an impressive Csp of 232 F g−1 at 1 A g−1, a superior energy density of 72.5 Wh kg−1, and an excellent cycle lifetime. Thus, the approach outlined in this work offers a promising strategy for developing 3D nano/microarchitecture metal hydroxides with potential applications in energy storage systems.

Elevating capacitive features of hydrothermally produced CeVS3 utilizing rGO for supercapacitor applications

This work presents the fabrication of a novel CeVS3/rGO nanocomposite using an easy hydrothermal route for supercapacitor applications. Physical studies revealed that CeVS3 showed flakes-like morphology, which is successfully decorated on reduced graphene oxide (rGO) sheets in nanocomposite. The electrochemical studies exhibited that fabricated CeVS3/rGO showed improved capacitive behavior with notable specific capacitance (Cs) of 1516 F/g at 1 A/g current density (jd) as well as excellent rate capability due to combined effect of CeVS3 nanoflakes and rGO sheets. Nanocomposite also demonstrated a lower resistance of 0.21 Ω than pure material, which have a charge transfer resistance (Rct) of 0.48 Ω. Furthermore, a two-electrode symmetric study was carried out in KOH solution (2.0 M), demonstrating a specific energy (SE) of 18.73 Wh/kg and specific power (SP) of 264.5 W/kg with remarkable cyclic stability after 5000 cycles. These findings demonstrated that innovative CeVS3/rGO can be utilized in next-generation supercapacitor applications.

Efficient synthesis and lithium storage performance of SiO2/TiO2 composite film anode by plasma electrolytic oxidation

SiO2/TiO2 composite films with different phase ratios have been successfully fabricated via the one-step plasma electrolytic oxidation (PEO) method in an alkaline electrolyte on Ti foil to obtain a binder-free anode for Li-ion batteries. The formed composite films present porous morphology of TiO2 with a uniform distribution of SiO2. The specific capacity can stabilize above 400 mAh/g at the current density of 100 μA cm−2 for 500 cycles, together with the apparent improved initial coulombic efficiency of 88.7 % and excellent rate capability, which arises from the peculiar structure and the synergic enhancement effect of SiO2 active materials and TiO2 matrix. This work provides an efficient and low-cost route for the preparation of Li-ion battery binder-free anodes and enriches the application of plasma electrolysis technology in energy field.

MoSSe-graphene based sandwiched nanolayer hybrid as high-performance lithium sulfur-selenium (LiSSe) battery cathodes

Rechargeable lithium batteries have demonstrated highly promising storage of energy systems because of their advantageous characteristics such as high energy density, extended cycle life, increased output power, and improved safety. To meet the ever-increasing high energy demands for powering hybrid and electric vehicles, it is necessary to develop electrode materials that possess high capacity and excellent rate capability. Hence, this work focuses on a MoSSe-Graphene based sandwiched nanolayer hybrid electrode material (MoSSe-Gr) for efficient Lithium-sulfur-selenium batteries applications. The MoSSe-Gr was synthesized through the solvothermal route, and subsequent calcination of the material at 800 °C under an inert atmosphere. Scanning electron microscopy (SEM), X-aray diffratometry (XRD), high-resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman shifts examinations reveal that graphitization of organic solvent from the precursor solution entrapped in the MoSSe interlayer spacing took place during calcination process, forming MoSSe-Graphene hybrid sandwich nanolayers. When employed as a cathodic material in a LiSSe battery, the hybrid sandwiched layers exhibited high-speed charging capability and extended cycle life. Specifically, the MoSSe-Gr material demonstrated a high-rate capability, delivering high capacities of 806.58/100, 668.42/500, 585.83/1000, 409.25/5000, and 284.16/10000 mAh/g/mA/g.

Realization of Enhanced Interfacial Lithium-Ion Transfer in Composite Polymer Electrolytes via Grafting Oligo-PEG Molecular Brushes on Silica-Coated Nanofibers for All-Solid-State Lithium Metal Batteries.

Polyether-based polymer electrolytes are attractive but still challenging for high-energy-density solid-state lithium metal batteries due to their limited Li-ion conductivity at room temperature. Herein, an oligomeric polyethylene glycol methyl ether methacrylate (PEGMEM)-modified silica-coated polyimide fibrous scaffold (PINF@PEGMEM-SiO2) was introduced in polyethylene glycol dimethyl ether (PEGDME) to enhance the Li-ion transportation at room temperature. PINF@PEGMEM-SiO2 was developed to build a continuous and interconnected interface for continuous Li-ion transportation in bulk. The carbonyl groups (C═O) of PEGMEM on SiO2 can promote the dissociation of lithium salts and enhance the migration of free Li ions at the interface. The same -C-C-O- unit contained in both PEGMEM and PEGDME ensures the compatibility of PEGMEM at the interface and PEGDME in the bulk. The prepared PEGDME-based polymer electrolyte exhibits a high ionic conductivity of 1.14 × 10-4 S cm-1 at 25 °C and an improved Li-ion transference number of 0.41. Furthermore, LiFePO4/Li and LiNi0.8Co0.1Mn0.1O2/Li cells with excellent cyclability and rate capability at ambient temperature are obtained.

Surface-to-bulk engineering with high-valence W6+ enabling stabilized single-crystal LiNi0.9Co0.05Mn0.05O2 cathode

Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for next-generation lithium batteries on account of their high capacity, while its practical application was hindered by structural instability and slow Li+ transfer kinetics. Herein, a surface-to-bulk engineered single-crystal LiNi0.9Co0.05Mn0.05O2 (Ni90) cathode, which features W-doped bulk and Li2WO4 surface layer, was successfully achieved by a one-step high-valence W6+ modification. The as-obtained W-modified Ni90 delivers excellent cycling stability (89.8% capacity retention after 300 cycles at 0.5 C) and rate capability. The enhanced electrochemical performance was ascribed to the doped-W induced stabilized lattice oxygen, reduced Li+/Ni2+ mixing and inhibited H2-H3 phase transition in the bulk, and Li2WO4 layer generated stabilized cathode/electrolyte interface. In addition, the thinner LiF-rich cathode electrolyte interphase (CEI) on surface and smaller grain size for W-modified Ni90 benefit to its Li+ diffusion dynamics. The effect of high-valence W6+ on single-crystal Ni-rich cathode was firstly revealed in detail, which deepens the understanding of electrochemical behavior of Ni-rich cathode with high-valence cations modification, and provides clues for design of high-performance layered cathodes.