Superior High-rate Capability Research Articles

In-situ formation of atomic-level Mn-Sn interfacial compounds for enhanced Li-ion integrated anode

High capacity nanosized SnO2 Li-ion battery anode can realize the reversible conversion of Sn/Li2O to SnO2. However, the coarsening of Sn particles leads to the incompleteness of this reversible reaction and the rapid decay of the reversible capacity. Here, an atom-level Mn–Sn interfacial composite oxide (MnSnO3) is coated on carbon fibers to form an integrated electrode by a simple in-situ technology. Ultrafine Mn nanocrystals can be uniformly dispersed around Sn nanoparticles with synergistic effect, which can effectively inhibit the coarsening of Sn and promote the high reversibility of SnO2 conversion. In addition to the porous nanostructure and binder-free properties, the prepared integrated anode exhibits initial capacity of 1350 mAh g−1 at 0.05 A g−1 with a high Coulombic efficiency of ~77.4%, superior high-rate capability, and stable long-life of more than 1000 cycles. It is hoped that this design will provide a new idea for the development of high-performance SnO2-based anodes.

A carbon-coated shuttle-like Fe2O3/Fe1-x S heterostructure derived from metal-organic frameworks with high pseudocapacitance for ultrafast lithium storage.

Pursuing active, low-cost, and stable electrode materials with superior rate capability and long-life cycling performances for lithium-ion batteries remains a big challenge. In this study, a carbon-coated shuttle-like Fe2O3/Fe1−xS heterostructure is synthesized by simply annealing Fe-based metal–organic frameworks (MIL-88(Fe)) as precursors and sublimed sulfur. Carbon-coated Fe2O3/Fe1−xS displays a unique structure with ultrafine Fe2O3/Fe1−xS nanoparticles distributed in the hollow and porous carbon matrix, which offers a large specific surface area and fast charge transfer ability, and alleviates the volume change upon cycling. When evaluated as an anode material for lithium-ion batteries, it exhibits an ultra-high specific capacity of 1200 mA h g−1 at 0.1 A g−1, and superior high rate capability with a capacity of 345 mA h g−1 at a very high current density of 5.0 A g−1 owing to its high electrical conductivity and enhanced pseudocapacitive contribution from surface effects. The current strategy is promising to synthesize the carbon-coated porous structure from metal–organic frameworks for next-generation energy-storage applications.

A multi-layered composite assembly of Bi nanospheres anchored on nitrogen-doped carbon nanosheets for ultrastable sodium storage.

Bismuth (Bi) is a promising anode candidate for sodium ion batteries (SIBs) with a high volumetric capacity (3765 mA h cm-3) and moderate working potential but suffers from large volume change (ca. 250%) during the sodiation/desodiation process, resulting in pulverization of the electrode, electrical contact loss, excessive accumulation of solid electrolyte interfaces, etc., devastating the cycling stability of the electrode seriously. Addressing this issue significantly relies on rational micro- and nano-structuring. Herein, we prepared a 3D multi-layered composite assembly of Bi/carbon heterojunctions with 0D bismuth nanospheres distributed and anchored on 2D nitrogen-doped carbon nanosheets (NCSs), using a preorganization strategy by taking full advantage of the strong complexation ability of Bi3+. The multi-layered composite assembly is periodic and close-packed, with Bi nanospheres <25 nm, carbon nanosheets ∼30 nm, and an average interlayer space of ∼75 nm. Such a specific architecture provides abundant electrochemically active surfaces and ion migration channels as the Bi nanospheres are attached to the 2D nitrogen-doped carbon nanosheets via a point-to-surface pattern. Moreover, the mono-layer Bi nanospheres oriented along the 2D-surface of NCSs are kinetically favorable for the recognition of Na+ by the active sites of Bi nanospheres as well as for avoiding the long distance migration of Na+ (external diffusion of Na+). Furthermore, thermodynamically, the small size and high surface energy of ultrasmall Bi nanospheres could contribute to high ion mobility (internal diffusion of Na+) and promote electrochemical reactions as well. The multi-layered composite assembly of Bi@NCSs (ML-Bi@NCSs) not only provides a robust 3D framework guaranteeing the whole structural stability but also ensures direct and full contact of each active nano-building block with electrolyte, thereby forming a high-throughput electron/ion transport system. When evaluated as the anode for SIBs, ML-Bi@NCSs deliver superior high-rate capability up to 30 A g-1 (specific capacity: 288 mA h g-1) and long-term cycling stability (capacity retention: 95.8% after 5000 cycles at 10 A g-1 and 90.6% after 10 000 cycles at 20 A g-1, respectively).

CTAB-Assisted Synthesis of C@Na3V2(PO4)2F3 With Optimized Morphology for Application as Cathode Material for Na-Ion Batteries

C@Na3V2(PO4)2F3 samples were obtained by using Cetyl Trimethyl Ammonium Bromide (CTAB) as a surfactant. The optimization of the added amount allowed controlling the eventual nanometric morphology of the particles. The morphological and structural properties of these samples were discussed in the light of solid-state techniques as X-ray diffraction, Raman and XPS spectroscopies, and electron microscopy. Galvanostatic test in sodium half-cells revealed that the nanometric spherical and porous particles provided by the addition of intermediate amounts of CTAB showed excellent cycling stability and superior high rate capability reflected in the minimization of the cell polarization and the determination of a high apparent diffusion coefficient.

Rational synthesis of Cr0.5Nb24.5O62 microspheres as high-rate electrodes for lithium ion batteries

Controllable fabrication of advanced electrode materials is critical for the development of lithium ion batteries (LIBs). Herein, for the first time, we report novel hierarchical porous chromium niobium oxide (Cr0.5Nb24.5O62) microspheres prepared by a facile one-step solvothermal method. The as-prepared Cr0.5Nb24.5O62 microspheres present 3D hierarchical porous structure consisting of cross-linked nanoparticles, high electronic conductivity and large specific surface area. Accordingly, the Cr0.5Nb24.5O62 microspheres show noticeable lithium ion storage performance with superior high-rate capability (199 mAh g−1 at 20C) and good cycling stability with a capacity retention of 95% over 1000 cycles, much better than the bulk Cr0.5Nb24.5O62 and TiNb24O62 counterparts. Our work demonstrates a new high-rate electrode material for high-power energy storage.

In Situ Encapsulating Metal Oxides into Core-Shell Hierarchical Hybrid Fibers for Flexible Zinc-Ion Batteries toward High Durability and Ultrafast Capability for Wearable Applications.

Rechargeable aqueous Zn-ion batteries are promising power sources for the advanced electronics because of their low cost, high safety, environmental friendliness, etc. However, their practical applications are severely restricted by the low energy density, poor rate capability, and low mass loading. In this work, a new type of the core-shell hierarchical structured hybrid fiber with encapsulated metal oxide nanoparticles is reported, which is used as a flexible cathode for aqueous Zn-ion batteries. The hierarchical hybrid fibers, consisting of one-dimensional (1D) central hollow shell and inside carbon network, build bicontinuous conductive pathways and highly porous networks for the in situ formed metal oxide nanoparticles. The core-shell hierarchical structure facilitates fast electron/ion transport and high mass loading; moreover, the 1D structure ensures good pliability and high flexibility. Two transition metal oxides, i.e., Zn2V2O7 and V2O5, are employed to construct the hybrid fibers. Both hybrid fibers exhibit excellent electrochemical properties and superior high rate capabilities. They achieve the capacities of 162 mAh g-1 (for Zn2V2O7) and 409 mAh g-1 (for V2O5) even at a high current density of 8 A g-1. Moreover, the flexible Zn-ion batteries are fabricated on the basis of the hybrid fibers. The superior energy/power density and good long-term cycling stability demonstrate their good energy storage capability and fast charge/discharge capability. Especially, the well-retained performance under high degree of outside deformations further promotes their applications in wearable electronics.

Self-Supporting, Flexible, Additive-Free, and Scalable Hard Carbon Paper Self-Interwoven by 1D Microbelts: Superb Room/Low-Temperature Sodium Storage and Working Mechanism.

Hard carbon is regarded as a promising anode material for sodium-ion batteries (SIBs). However, it usually suffers from the issues of low initial Coulombic efficiency (ICE) and poor rate performance, severely hindering its practical application. Herein, a flexible, self-supporting, and scalable hard carbon paper (HCP) derived from scalable and renewable tissue is rationally designed and prepared as practical additive-free anode for room/low-temperature SIBs with high ICE. In ether electrolyte, such HCP achieves an ICE of up to 91.2% with superior high-rate capability, ultralong cycle life (e.g., 93% capacity retention over 1000 cycles at 200 mA g-1 ) and outstanding low-temperature performance. Working mechanism analyses reveal that the plateau region is the rate-determining step for HCP with a lower electrochemical reaction kinetics, which can be significantly improved in ether electrolyte.

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

SummaryEven though the energy density of O3-type layer-structured metal oxide cathode can fully reach the requirement for large-scale energy storage systems, the cycling lifespan still cannot meet the demand for practical application once it is coupled with a non-sodium-metal anode in full-cell system. Transition metal dissolution into the electrolyte occurs along with continuous phase transformation and accelerates deterioration of the crystal structure, followed by migration and finally deposition on the anode to form a vicious circle. Surface engineering techniques are employed to modify the interface between active materials and the electrolyte by coating them with a thin layer of AlPO4 ion conductor. This stable thin layer can stabilize the surface crystal structure of the cathode material by avoiding element dissolution. Meanwhile, it can protect the anode from increased resistance by suppressing the dissolution-migration-deposition process. This technique is a promising method to improve the lifetime for the future commercialization.

The influence of Li2O incorporation on the electrochemical properties of Li4Ti5O12 thin film electrodes

High quality Li4Ti5O12 anode films were deposited by radio-frequency co-sputtering Li4Ti5O12 and Li2O targets on Pt-coated stainless steel substrates. The use of an additional Li2O target not only compensated the lithium content in the resulting layers but also decreased the impurity content. Consequently, the electrochemical properties of the Li4Ti5O12 anode exhibited better electrochemical properties than an identical film prepared using a single Li4Ti5O12 target. Upon annealing, the co-sputtering Li4Ti5O12 showed a relatively high discharge capacity of 618 mAh/cm3 (theoretical specific capacity of 598.5 mAh/cm3) at a current density of 0.1 C. Also, superior high rate capability with a discharge capacity of 309 mAh/cm3 at 20 C was observed, accompanied by an excellent cycling stability, with a capacity retention ratio exceeding 94% after 500 cycles at 1 C. The co-sputtering using Li2O target is most likely to have enhanced the electrochemical properties of the pure Li4Ti5O12 anode.

Nitrogen and iodine dual-doped 3D porous graphene as a bi-functional cathode catalyst for Li-O2 batteries

A novel nitrogen and iodine co-doped porous graphene with well-defined hierarchical microstructure is synthesized via a hydrothermal self-assembly strategy followed by heat treatment at elevated temperature. Its electrochemical properties as the cathode catalyst for Li–O2 batteries are investigated. Compared to un-doped, nitrogen or iodine single doped porous graphene, nitrogen and iodine co-doped porous graphene shows much higher activity for oxygen reduction reaction and oxygen evolution reaction. As oxygen cathode for Li–O2 batteries, nitrogen and iodine co-doped porous graphene exhibits an outstanding specific reversible capacity up to 14000 mAh g−1 at 200 mA g−1, a superior high-rate capability (5000 mAh g−1 at 1000 mA g−1), and an excellent cycling stability enduring over 225 cycles with a limited capacity of 1000 mA h g−1 at a current density of 500 mA g−1. The fantastic cycling performance can be attributed to a combination of porous structure and dual-doping, which not only provides a large number of channels for oxygen diffusion and electrolyte infiltration, but also supplies abundant active catalytic sites to affect the formation and decomposition of the discharge products with various morphologies. This study provides an effective approach to develop highly-efficient carbon-based catalysts with optimized pore structure and tunable surface chemistry.

CNTs@S composite as cathode for all-solid-state lithium-sulfur batteries with ultralong cycle life

Abstract The main challenges in development of traditional liquid lithium-sulfur batteries are the shuttle effect at the cathode caused by the polysulfide and the safety concern at the Li metal anode arose from the dendrite formation. All-solid-state lithium-sulfur batteries have been proposed to solve the shuttle effect and prevent short circuits. However, solid-solid contacts between the electrodes and the electrolyte increase the interface resistance and stress/strain, which could result in the limited electrochemical performances. In this work, the cathode of all-solid-state lithium-sulfur batteries is prepared by depositing sulfur on the surface of the carbon nanotubes (CNTs@S) and further mixing with Li10GeP2S12 electrolyte and acetylene black agents. At 60 °C, CNTs@S electrode exhibits superior electrochemical performance, delivering the reversible discharge capacities of 1193.3, 959.5, 813.1, 569.6 and 395.5 mAh g−1 at the rate of 0.1, 0.5, 1, 2 and 5 C, respectively. Moreover, the CNTs@S is able to demonstrate superior high-rate capability of 660.3 mAh g−1 and cycling stability of 400 cycles at a high rate of 1.0 C. Such uniform distribution of the CNTs, S and Li10GeP2S12 electrolyte increase the electronic and ionic conductivity between the cathode and the electrolyte hence improves the rate performance and capacity retention.

Integrating TiO₂/SiO₂ into Electrospun Carbon Nanofibers towards Superior Lithium Storage Performance.

In order to overcome the poor electrical conductivity of titania (TiO2) and silica (SiO2) anode materials for lithium ion batteries (LIBs), we herein report a facile preparation of integrated titania–silica–carbon (TSC) nanofibers via electrospinning and subsequent heat-treatment. Both titania and silica are successfully embedded into the conductive N-doped carbon nanofibers, and they synergistically reinforce the overall strength of the TSC nanofibers after annealing (Note that titania–carbon or silica–carbon nanofibers cannot be obtained under the same condition). When applied as an anode for LIBs, the TSC nanofiber electrode shows superior cycle stability (502 mAh/g at 100 mA/g after 300 cycles) and high rate capability (572, 518, 421, 334, and 232 mAh/g each after 10 cycles at 100, 200, 500, 1000 and 2000 mA/g, respectively). Our results demonstrate that integration of titania/silica into N-doped carbon nanofibers greatly enhances the electrode conductivity and the overall structural stability of the TSC nanofibers upon repeated lithiation/delithiation cycling.

Titanium Glycolate@Polythiophene Derivative: Waxberry-Like TiO2@Carbon Composites with High-Pseudo-Capacitive Performance for Sodium Storage

Herein, we describe the preparation of waxberry-like TiO2@carbon core-shell composites through one-pot in-situ polymerization and a subsequent calcination process using polythiophene as both a carbon and a sulfur source. This simple preparative process allows for the simultaneous introduction of sulfur into the TiO2 and carbon (STiO2@SC). The morphology, structure, and electrochemical performance were studied in detail. The introduction of sulfur and the core-shell structure afford STiO2@SC composites with high-pseudocapacitive sodium storage capacity and are thus considered promising anode materials for sodium ion batteries. STiO2@SC composites deliver high reversible capacity (212.9 mA h g−1 at 0.2 A g−1), superior high-rate capability (121.2 mA h g−1 after 2000 cycles at 1 A g−1), excellent cycling stability (capacity retention of ∼100% except 1st cycle at 1 A g−1), and stability against high current variations.

“Bubble-linking-bubble” hybrid fibers filled with ultrafine TiN: a robust and efficient platform achieving fast kinetics, strong ion anchoring and high areal loading for selenium sulfide

A “bubble-linking-bubble” hybrid fiber is an efficient host for selenium sulfide to achieve superior high rate capability and excellent cycling stability.

Cable-like heterogeneous porous carbon fibers with ultrahigh-rate capability and long cycle life for fast charging lithium-ion storage devices.

In this paper, we propose a space-confined foaming approach to fabricate cable-like heterogeneous porous carbon fibers (Si-CPCFs) containing an inner graphitized carbon "conductor" and an outer Si-doping amorphous carbon "shield". Benefiting from the fast Li+ intercalation and high conductivity of the "inner conductor", and the rich pseudocapacitance of the "outer shield", the Si-CPCFs exhibit an ultrahigh-rate capability and cycling performance, leading to a high capacity of 132 mA h g-1 even at an ultra-high current density of 100 A g-1 after 10 000 cycles. The assembled lithium ion hybrid supercapacitors (LIHCs) also deliver a superior energy density of 50 W h kg-1 at an ultra-high power density of 113 kW kg-1, really achieving both a high energy density and power density of LIHCs. The success of the cable-like heterogeneous porous carbon architecture proposes a new direction to circumvent the discrepancy in kinetics and capacity mismatch, and also attracts more attention to heterogeneous nanostructures with multiple functions.

Well-defined Na2Zn3[Fe(CN)6]2 nanocrystals as a low-cost and cycle-stable cathode material for Na-ion batteries

Well-defined Na2Zn3[Fe(CN)6]2 nanocrystals (~300 nm) have been fabricated by a facile controlled crystallization method from low-cost precursors at room temperature. By employing [Fe(CN)6]3−/[Fe(CN)6]4− couples as redox centres, this material can realize a theoretical 1Na-storage capacity of 70 mAh g−1, a superior high-rate capability of 20 C and an impressive cycle life of 1000 cycles, offering a low-cost and high-performance alternative cathode for large-scale Na-ion applications.

Li-Rich Layered/Spinel Cathode Composite 3/4[Li2MnO3·LiCxO2]·1/4[LiCxMnO4] (Cx = Cr1-yCoy) for Li-Ion Batteries

A new series of Li-rich layered/spinel Li-Cr-Co-Mn-O composites are designed and investigated in this article. The high voltage spinel LiCxMnO4 (Cx = Cr1-yCoy) materials are embedded into lithium-rich layered materials and these Li-rich layered/spinel integrated structures exhibit both superior reversible capacities and high rate capabilities as cathode materials for lithium-ion batteries. The Li-rich layered/spinel 3/4[Li2MnO3·LiCxO2]·1/4[LiCxMnO4] (Cx = Cr1-yCoy) composites are synthesized with sol-gel method. XRD, HRTEM and fast Fourier transform (FFT) analysis demonstrate the integrated structure of Li-rich layered component and spinel phase. The electrochemical investigations performed within a wide potential window show an excellent result of the materials with the proper ratio between Co and Cr. All the composite materials exhibit initial discharge capacities over 200 mAh g−1. In particular, y = 0.4 and 0.6 samples show preferable cycling stability among the investigated materials, which is primarily attributed to the high reversible capacity of Li-rich layered component and 3D Li-ion diffusion channels of spinel phase, as well as low charge transfer resistance and Warburg diffusion impedance owing to the synergistic effect of the proper ratio between Co and Cr elements in these composites.

A study on graphene/tin oxide performance as negative electrode compound for lithium battery application

A novel negative (anode) material for lithium-ion batteries, tin oxide particles covered with graphene (SnO/graphene) prepared from graphite was fabricated by hydrothermal synthesis. The structure and morphology of the composite were characterized by Raman spectra, FTIR spectra, XRD, XPS and FESEM. It is observed that the G and 2D bands (1581 and 2831 cm−1, respectively) have more intensity in graphene rather than graphite. EIS was carried out. It is observed that the lowest Warburg impedance coefficient, σw, is 24.39 Ω s0.5 for Li/SnO–graphene (3:1) cell. The reversible specific capacity of Li/SnO–graphene (3:1) cell was about 0.950 Ah g−1 after 100 cycles at current density current 10−2 A g−1. These results indicate that 3 SnO:1 graphene possesses superior cycle performance and high rate capability. The enhanced electrochemical performances can be ascribed to the characteristic structure of tin oxide with graphene shells, which buffer the volume change of the metallic tin and prevent the detachment and agglomeration of pulverized tin.

Enabling a Safe Metallic Sodium Anode Using Chemically-Engineered Porous Copper Matrix with Cylindrical Core-Shell Skeleton

Sodium (Na) metal is the most promising alternative for lithium metal as an anode material for the next-generation energy storage systems due to its high theoretical capacity, low cost and high natural abundance. However, huge volume change and severe dendrite growth of Na metal anode during repeated electrochemical stripping/plating result in rapid electrode degradation, low Coulombic efficiency, and even the risk of explosion caused by short circuit of the batteries. Because of its very soft nature, Na metal is susceptible to deform and degrade during both battery assembly process and electrochemical cycling. The volume and morphology change of the “hostless” Na severely aggravates the growth of Na dendrites. Thus, it is essential to seek an ideal host to support Na metal so as to maintain the high integrity of the electrode. Here we present the employment of a chemically engineered 3D porous copper (Cu) matrix with a cylindrical core-shell skeleton structure as a highly stable host for metallic Na anode, enabling a high Na areal mass loading of 70 mg cm-2, through a facile and cost-effective surface treatment on commercially available Cu foam in forming high performance composite anode for Na-based batteries. We find that the unique surface characteristics of the as-obtained matrix can not only facilitate uniform impregnation and confinement of Na within the matrix pores promoted by the chemical interaction between Na and the matrix, but also can divert the Na plating from the matrix skeleton towards the Na reservoirs within the pores upon cycling. Benefiting from our delicately surface-engineered matrix as a host for Na, we demonstrate an excellent Na anode cycling stability in carbonate electrolyte without any additives over 100 cycles (300 hours) at a current density up to 2 mA cm-2 with a high cycling capacity up to 3 mAh cm-2. A stable rate performance up to 3 mA cm-2 is also demonstrated. A full cell made of Na3V2(PO4)3 as cathode and the as-prepared surface-treated Na composite as anode is further tested, showing superior cycling performance and high rate capability (at 5C) compared with that using bare Na metal as anode. In addition to performance improvement, we systematically investigate the interfacial interactions between treated/untreated Cu matrixes and metallic Na to reveal how the surface property of the matrix skeleton greatly influences the electrochemical stability of Na anode.

Hierarchical flower-like SnS grafted with glucosamine-derived nitrogen-doped carbon with enhanced reversible Li-storage performance

A simple hydrothermal plus annealing method has been developed to fabricate SnS/NC nanocomposites and their electrochemcial Li-storage performance has also been investigated. The as-prepared composites are characterized by XRD, SEM, EDS, Raman, BET and XPS. In this composite, ultrathin SnS nanosheets are well hybridized with glucosamine-derived nitrogen-doped carbon to form hierarchical porous architectures with large surface areas. Benefiting from the desirable structural merits as well as the generated synergism between components, the SnS/NC composite electrode delivers an enormously enhanced electrochemical lithium-storage performance including large reversible capacity of 832 mA h g−1 after 100 cycles, enhanced cyclability and superior high-rate capability.