Anode For Na-ion Batteries Research Articles

The influence of Stone-Wales defects in nanographene on the performance of Na-ion batteries

The effect of the Stone-Wales (SW) defect on the energetic, structural, electronic properties of Na/Na+ adsorption on the Hexa-peri-hexabenzocoronene (HBC) nanographene is investigated using density functional theory calculations. We showed that two kinds of SW defects can be generated in the structure of HBC, and the defected sheets are less stable than the intrinsic HBC by about 63.2–65.3 kcal/mol. The heptagonal ring of SW defect is the most favorable site for the Na and Na+ adsorption and the adsorption energies increase from −0.8 and −33.2 kcal/mol on the intrinsic HBC to −16.7 and −39.3 kcal/mol on the SW-HBC, respectively. The predicted energy barrier for an Na atom to move from a heptagonal ring to another one in the SW-HBC is about 4.9 kcal/mol, indicating a high ion mobility compared to the pristine HBC. The SW defect increases the Na diffusion coefficient from 3.46 × 10−11 to 2.83 × 10−6 cm2/s. Although the SW defect increases the ion mobility, it has an undesirable effect on the cell voltage, if a HBC nanographene is used in the anode of Na-ion batteries.

2D Ti3C2Tz MXene Synthesized by Water-free Etching of Ti3AlC2 in Polar Organic Solvents

Summary The first MXene discovered, Ti3C2Tz, was synthesized by etching of the parent MAX phase, Ti3AlC2, in a solution of concentrated hydrofluoric acid. Since then, several other ways of synthesizing MXenes have been reported, such as electrochemical etching in various electrolytes, high-temperature alkali treatment, molten salt synthesis, etc. The majority of these etching methods, however, use water as their main solvent, limiting direct use of MXenes in water-sensitive applications. In this work, we show that it is possible to etch, and delaminate, MXenes in the absence of water, by using organic polar solvents in the presence of ammonium dihydrogen fluoride. We further show that by using this etching method, it is possible to obtain Ti3C2Tz flakes rich in fluorine terminations. We also demonstrate that electrodes made from Ti3C2Tz etched in propylene carbonate resulted in Na-ion battery anodes with double the capacity to those etched in water.

A computational study on the BN-yne sheet application in the Na-ion batteries

Although Li-ion batteries are extensively applied, short lifetime, high cost, and safety problems limit their application. Na-ion batteries (NIB) might be an alternative to the Li-ion owing to wide availability, low cost, and nontoxicity of Na. Here, we performed density functional theory calculations to investigate the possible application of a graphyne-like BN layer (BN-yne) in the anode of NIBs. The adsorption energies of Na and Na+ on the BN-yne are predicted to be −15.3 and −54.6 kcal/mol, respectively. It was found that the maximum barrier energy for migration of Na atom and Na+ ion through BN-yne surface is about 20.2 and 16.5 kcal/mol, respectively. The calculated cell voltage for the BN-yne are predicted to be and 1.70 V. Using an electric field of −0.02 a. u. much more strengthens the interaction of Na+ with the BN-yne compared to the Na atom, increasing the cell voltage of NIB to 2.10 eV. We showed that a high Na storage capacity (Na4B2N2), high cell voltage and diffusion ability of BN-yne make it a promising candidate for the NIB anode material.

Assembled NiS nanoneedles anode for Na-ion batteries: Enhanced the performance by organic hyperbranched polymer electrode additives

Conversion-type materials provide abundant options for Na-ion battery anodes, but the inferior cycleability and low first-cycle coulombic efficiency block their application in full Na-ion batteries. Herein, hierarchical structures of ultra-thin NiS nanoneedles are prepared and investigated as anodes for Na-ion batteries. A new organic polymer is applied to regulate ultra-thin nanoneedle structure (~10 nm), facilitating solid-state Na+ diffusion and enhancing the rate capability. Significantly, the organic hyperbranched polymer acts as an additive uniformly distributed in the material, offering an elastic framework to prevent nanoparticle aggregation and thus improving the cycleability. The NiS electrode delivers a high capacity of 590 mA h g−1 at 100 mA g−1, and the coulombic efficiency is 93% at the first cycle. The NiS electrode also exhibits an excellent rate performance with 320 mA h g−1 capacity at 20 A g−1, as well as a remarkable cycleability with 90.2% capacity maintained after 1000 cycles. Moreover, the NiS anode shows a good compatibility with Na3V2(PO4)3/C cathode in the full Na-ion cells. The present work introduces a feasible conversion-type NiS anode for Na-ion batteries, and highlights a facile and efficient strategy for the performance improvement of conversion-type anode with such an organic hyperbranched polymer electrode additive.

Surface-dominated storage of heteroatoms-doping hard carbon for sodium-ion batteries

Though the intercalation mechanism of hard carbon anodes for Na-ion batteries (NIBs) gain decent electrochemical performances, the sluggish diffusion kinetics of Na-ions at low potential present huge challenge to high power applications. To improve the rate capability and cycling stability, especially the performance at high rates, herein, a novel N, S co-doping strategy based on the pseudocapacitive mechanism is developed via one-step synthesis, which endows the hard carbon with excellent rate performances and long-term cycling stability. Moreover, the electrochemical behaviors of N, S co-doping carbon materials outperform those of single heteroatom (N) doping materials, owing to the additional effective covalent S bonds and more defects. The optimized NSC2 (derived from 2:1 mass ratio of thiourea and sodium citric) delivers a high reversible capacity of 280 ​mAh g−1 at 0.05 ​A ​g−1 for 200 cycles and 223 ​mAh g−1 at 1 ​A ​g−1 for 2000 cycles, respectively, and preserves 102 ​mAh g−1 at 10 ​A ​g−1. This work provides a universal co-doping approach on modification of hard carbon materials for high power battery applications.

One-pot synthesis of Bi-reduced graphene oxide composite using supercritical acetone as anode for Na-ion batteries

A high-energy–density Bi-reduced graphene oxide (Bi-RGO) composite was synthesized using the quick one-pot supercritical acetone (scACT) method. The unique deoxygenation properties and ultrafast particle formation in scACT led to the simultaneous reduction of graphene oxide to reduced graphene oxide (RGO) and the formation of heterogeneously nucleated, nanosized Bi particles 10–20 nm in size that were tightly anchored to the basal plane of RGO and homogeneously nucleated, large Bi particles 250–950 nm in size. When tested as the anode of Na-ion batteries, the Bi-RGO composite delivered the high reversible capacity of 200 mAh g−1 at 50 mA g−1 and the high volumetric capacity of 60 Ah L−1. In situ X-ray diffraction analysis revealed that the two-step alloying–dealloying Bi → NaBi → hexagonal Na3Bi or cubic Na3Bi reactions depended on the Bi particle size.

Designing a slope-dominated hybrid nanostructure hard carbon anode for high-safety and high-capacity Na-ion batteries

A slope-dominated mechanism is designed by preparing hybrid nanostructure carbon materials using a CVD-like method which provides hard carbon with excellent rate performances and high average discharge potential as an anode for Na-ion batteries.

Recent advances in electrospun one-dimensional carbon nanofiber structures/heterostructures as anode materials for sodium ion batteries

We summarize recent advances in electrospun carbon nanofiber (CNF)-based structures as Na-ion battery anodes, providing in-depth understanding of structure design, heteroatom doping and construction of alloy/metal chalcogenide-CNF heterostructures.

The electrochemical storage mechanism of an In2S3/C nanofiber anode for high-performance Li-ion and Na-ion batteries

There are only a handful of reports on indium sulfide (In2S3) in the electrochemical energy storage field without a clear electrochemical reaction mechanism. In this work, a simple electrospinning method has been used to synthesize In2S3/C nanofibers for the first time. In lithium-ion batteries (LIBs), the In2S3/C nanofiber electrode can not only deliver a high initial reversible specific capacity of 696.4 mA h g-1 at 50 mA g-1, but also shows ultra-long cycle life with a capacity retention of 80.5% after 600 cycles at 1000 mA g-1. In sodium-ion batteries (SIBs), the In2S3/C nanofibers electrode can exhibit a high initial reversible specific capacity (393.7 mA h g-1 at 50 mA g-1) and excellent cycling performance with a high capacity retention of 97.3% after 300 cycles at 1000 mA g-1. The excellent electrochemical properties mainly benefited from In2S3 being encapsulated by a carbon matrix, which buffers the volume expansion and significantly improves the conductivity of the composite. Furthermore, the structural evolution of In2S3 during the first lithiation/delithiation and sodiation/desodiation processes has been illustrated by ex situ XRD. The results confirm that the reaction mechanism of In2S3 in both LIBs and SIBs can be summarized as conversion reactions and alloying reactions, which provide theoretical support for the development of In2S3 in the field of electrochemistry.

Tuning the electronic energy level of covalent organic frameworks for crafting high-rate Na-ion battery anode

Crystalline Covalent Organic Frameworks (COFs) possess ordered accessible nano-channels. When these channels are decorated with redox-active functional groups, they can serve as the anode in metal ion batteries (LIB and SIB). Though sodium's superior relative abundance makes it a better choice over lithium, the energetically unfavourable intercalation of the larger sodium ion makes it incompatible with the commercial graphite anodes used in Li-ion batteries. Also, their sluggish movement inside the electrodes restricts the fast sodiation of SIB. Creating an electronic driving force at the electrodes via chemical manipulation can be a versatile approach to overcome this issue. Herein, we present anodes for SIB drawn on three isostructural COFs with nearly the same Highest Occupied Molecular Orbitals (HOMO) levels but with varying Lowest Unoccupied Molecular Orbitals (LUMO) energy levels. This variation in the LUMO levels has been deliberately obtained by the inclusion of electron-deficient centers (phenyl vs. tetrazine vs. bispyridine-tetrazine) substituents into the modules that make up the COF. With the reduction in the cell-potential, the electrons accumulate in the anti-bonding LUMO. Now, these electron-dosed LUMO levels become efficient anodes for attracting the otherwise sluggish sodium ions from the electrolyte. Also, the intrinsic porosity of the COF favors the lodging and diffusion of the Na+ ions. Cells made with these COFs achieve a high specific capacity (energy density) and rate performance (rapid charging-discharging), something that is not as easy for Na+ compared to the much smaller sized Li+. The bispyridine-tetrazine COF with the lowest LUMO energy shows a specific capacity of 340 mA h g-1 at 1 A g-1 and 128 mA h g-1 at a high current density of 15 A g-1. Only a 24% drop appears on increasing the current density from 0.1 to 1 A g-1, which is the lowest among all the top-performing COF derived Na-ion battery anodes.

Optimizing the Void Size of Yolk–Shell Bi@Void@C Nanospheres for High-Power-Density Sodium-Ion Batteries

Bismuth (Bi) has been demonstrated as a promising anode for Na-ion batteries (NIBs) because it has high gravimetry (386 mA h g-1) and volumetric capacity (3800 mA h cm-3). However, Bi suffers from large volume expansion during sodiation, leading to poor electrochemical performance. The construction of a nanostructure with sufficient void space to accommodate the volume change has been proven effective for achieving prolonged cycling stability. However the excessive void space will definitely decrease the volumetric energy density of the battery. Herein, we design optimized Bi@Void@C nanospheres (Bi@Void@C-2) with yolk-shell structure that exhibit the best cycling performance and enhanced volumetric energy density. The optimized void space not only could buffer the volume change of the Bi nanosphere but also could keep the high volumetric energy density of the battery. The Bi@Void@C-2 shows an excellent rate capacity of 173 mA h g-1 at ultrahigh current density of 100 A g-1 and long-cycle life (198 mA h g-1 at 20 A g-1 over 10 000 cycles). The origin of the superior performance is achieved through in-depth fundamental studies during battery operation using in situ X-ray diffraction (XRD) and in situ transmission electron microscope (TEM), complemented by theoretical calculations and ex situ TEM observation. Our rational design provides insights for anode materials with large volume variation, especially for conversion type and alloying type mechanism materials for batteries (i.e., Li-ion batteries, Na-ion batteries).

Nanointerface-driven pseudocapacitance tuning of TiO2 nanosheet anodes for high-rate, ultralong-life and enhanced capacity sodium-ion batteries

Nanointerface-driven pseudocapacitance tuning is demonstrated as a strategy to substantially improve the Na-ion storage performance of TiO 2 anodes. Excellent electrochemical performance of hybrid TiO 2 nanosheets is credited to the superior Na-ion intercalation pseudocapacitance resulting from anatase-bronze nanointerfaces. • Nanointerface-driven pseudocapacitance boosted Na-ion storage performance. • Anatase-bronze nanointerfaces resulted Na-ion intercalation pseudocapacitance. • Hybrid TiO 2 anode exhibited 12-fold higher pseudocapacitance than previous reports. • This strategy provides new opportunities to design advanced Na-ion battery anodes. Titanium dioxide recently gained attention as sodium-ion battery anode material. However, its practical application is hindered by low specific capacity (~150 mAh/g), and mediocre cycling stability. Here we report for the first time, nanointerface-driven Na-ion intercalation pseudocapacitance tuning as a strategy to substantially improve the performance of TiO 2 anodes. This is achieved by tuning the crystal mismatch between anatase and bronze crystallites of hierarchical TiO 2 nanosheets. Hybrid TiO 2 nanosheets composed of ~10 nm sized anatase (~85%) and bronze (~15%) crystallites exhibited significantly higher pseudocapacitive Na-ion storage compared to phase-pure bronze and anatase TiO 2 nanosheets. High specific capacity of 290 mAh/g (~0.87 mol Na-ions) at a current density of 25 mA/g is obtained for this composition. Hybrid TiO 2 maintained a specific capacity of 120 mAh/g even at a high current density of 1 A/g. Coulombic efficiency (~100%) and cycling stability are outstanding, retaining 90% of the initial capacity after 2500 galvanostatic cycles. These electrochemical performances are noticeably superior to amorphous and crystalline TiO 2 reported earlier. Mechanistic studies proved Na-ion intercalation pseudocapacitance without considerable structural changes. Excellent electrochemical performance of dual-phase hierarchical TiO 2 nanosheets is credited to the superior Na-ion intercalation pseudocapacitance resulting from anatase-bronze nanointerfaces. The demonstrated strategy of nanointerface-driven pseudocapacitance tuning provides new opportunities for the designing of advanced Na-ion battery anodes.

Enhanced Kinetics over VS4 Microspheres with Multidimensional Na+ Transfer Channels for High-Rate Na-Ion Battery Anodes.

Developing 3 D self-assembled nanoarchitectures with well-defined crystal structures is an effective strategy to enhance the electrochemical performances of electrode materials. (1 1 0)-oriented and bridged-nanoblocks self-assembled VS4 microspheres are controllably synthesized by a facile one-step hydrothermal method. The (1 1 0)-bridged structure sets up open pathways for Na+ diffusion among nanoblocks, and the (1 1 0)-oriented structure provides unobstructed pathways for Na+ diffusion in the nanoblocks, which collectively constructs multidimensional Na+ transfer channels in the VS4 microspheres, promoting the electrochemical kinetics. As an anode for Na-ion batteries (SIBs), this material exhibits pseudocapacitive Na+ storage and excellent rate capability, delivering high capacities of 339 and 270 mAh g-1 at rates of 0.1 and 2.0 A g-1 , respectively, with a capacity retention of 79 % in the voltage window of 0.5-3.0 V. In particular, the reversible capacity reaches 575 mAh g-1 after 300 cycles even at 1.0 A g-1 in the voltage window of 0.05-3.0 V, outperforming those of the ever-reported VS4 -based anode materials. This work presents an effective strategy to the exploration and design of high-performance anodes for SIBs.

Regulating Pore Structure of Hierarchical Porous Waste Cork‐Derived Hard Carbon Anode for Enhanced Na Storage Performance

AbstractPorous structure design is generally considered to be a reliable strategy to boost ion transport and provide active sites for disordered carbon anodes of Na‐ion batteries (NIBs). Herein, a type of waste cork‐derived hard carbon material (CC) is reported for efficient Na storage via tuning the pore species. Benefiting from the natural holey texture of this renewable precursor, CCs deliver a novel hierarchical porous structure. The effective skeletal density test combined with small angle X‐ray scattering analysis (SAXS) is used to obtain the closed pore information. Based on a detailed correlation analysis between pore information and the electrochemical performance of CCs, improving pyrolysis temperature to reduce open pores (related to initial capacity loss) and increase closed pores (related to plateau capacity) endows an optimal CC with a high specific capacity of ≈360 mAh g−1 in half‐cells and a high energy density of 230 Wh kg−1 in full‐cells with a capacity retention of 71% after 2000 cycles at 2C rate. The bioinspired high temperature pore‐closing strategy and the new insights about the pore structure–performance relationship provide a rational guide for designing porous carbon anode of NIBs with tailored pore species and high Na storage capacity.

Reduced Graphene Oxides Decorated NiSe Nanoparticles as High Performance Electrodes for Na/Li Storage.

A facile, one-pot hydrothermal method was used to synthesize Nickel selenide (NiSe) nanoparticles decorated with reduced graphene oxide nanosheets (rGO), denoted as NiSe/rGO. The NiSe/rGO exhibits good electrochemical performance when tested as anodes for Na-ion batteries (SIBs) and Li-ion batteries (LIBs). An initial reversible capacity of 423 mA h g−1 is achieved for SIBs with excellent cyclability (378 mA h g−1 for 50th cycle at 0.05 A g−1). As anode for LIBs, it delivers a remarkable reversible specific capacity of 1125 mA h g−1 at 0.05 A g−1. The enhanced electrochemical performance of NiSe/rGO nanocomposites can be ascribed to the synergic effects between NiSe nanoparticles and rGO, which provide high conductivity and large specific surface area, indicating NiSe/rGO as very promising Na/Li storage materials.

Advanced lignin-derived hard carbon for Na-ion batteries and a comparison with Li and K ion storage

Hard carbon is the most attractive anode in Na-ion batteries. The performance of hard carbon relies primarily on the precursors and the synthesis approaches. Lignin, as the second-abundant biopolymer in nature, with the low cost and high carbon yield makes it an ideal precursor for the preparation of hard carbon. However, lignin-derived hard carbon from direct carbonization shows poor electrochemical performance. A low-temperature pre-oxidation is applied in this study to introduce carbonyl groups for enhancing the crosslink of lignin. Consequently, the growth and orientation of graphitic layers during carbonization are inhibited, which in turn increases the layer distance for facilitating the Na ion insertion and leads to exceptional rate capability and superb cyclic life. To gain insights into the charge storage mechanism, a comparison with Li- and K-ion storage in hard carbon is conducted through in-situ Raman tests. There are similarities of alkali-metal ion storage at high voltages but remarkable disparities at low voltages, thus emphasizing the importance of microstructure design of hard carbon depending on the application in various metal-ion batteries.

Continuous/reversible phase transition behaviors and their effect on the hysteresis energy loss of the anodes in Na-ion batteries

Alloying anode materials undergo a continuous and reversible phase transition during battery cycles, and the energy consumed during this process determines the energy efficiency of the anode. In this study, using the combined technique of voltammetric experiments and first-principles calculations, comparative studies are performed on P and Sb anodes to identify their phase transition behaviors, associated with the charge–discharge processes of Na-ion batteries (NIBs). To quantitatively establish the phase transition vs energy efficiency relationship of the anode materials of NIBs, we developed a thermodynamic model that replicates the polarization curves observed in voltammetric measurements. We obtained theoretical polarization curves by analyzing the phase transformation sequence and corresponding changes in the resistivity values of intermediate phases of the Na–P and Na–Sb systems under various applied potentials. The formation of various intermediate metastable phases and their high electrical resistivity are identified to be responsible for the increased loss in energy at the anodes. While filling the knowledge gaps on the reasons as to why the Na–P and Na–Sb systems exhibit different hysteresis losses, the outcomes of this study provide a crude yet basic guideline for the appropriate choice of potential anode materials with superior energy efficiencies suitable for NIBs.

Phase Stability and Electronic Structure of Tin Sulfide Compounds for Li-ion Batteries

Tin is an important component of a variety of promising anode and solid-electrolyte chemistries for Li and Na-ion batteries. Here, we report on a first-principles investigation of phase stability a...

Amorphous Sb2S3 Nanospheres In-Situ Grown on Carbon Nanotubes: Anodes for NIBs and KIBs.

Antimony sulfide (Sb2S3) with a high theoretical capacity is considered as a promising candidate for Na-ion batteries (NIBs) and K-ion batteries (KIBs). However, its poor electrochemical activity and structural stability are the main issues to be solved. Herein, amorphous Sb2S3 nanospheres/carbon nanotube (Sb2S3/CNT) nanocomposites are successfully synthesized via one step self-assembly method. In-situ growth of amorphous Sb2S3 nanospheres on the CNTs is confirmed by X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. The amorphous Sb2S3/CNT nanocomposites as an anode for NIBs exhibit excellent electrochemical performance, delivering a high charge capacity of 870 mA h g−1 at 100 mA g−1, with an initial coulomb efficiency of 77.8%. Even at 3000 mA g−1, a charge capacity of 474 mA h g−1 can be achieved. As an anode for KIBs, the amorphous Sb2S3/CNT nanocomposites also demonstrate a high charge capacity of 451 mA h g−1 at 25 mA g−1. The remarkable performance of the amorphous Sb2S3/CNT nanocomposites is attributed to the synergic effects of the amorphous Sb2S3 nanospheres and 3D porous conductive network constructed by the CNTs.

Engineering of Yolk-Double Shell Cube-like SnS@N-S Codoped Carbon as a High-Performance Anode for Li- and Na-Ion Batteries.

A yolk-double shell cube-like SnS@N-S codoped carbon (YDSC-SnS@NSC) was delicately tailored by a self-templated and selective etching method as well as a self-assembly strategy. Herein, the ZnSn(OH)6 (ZHS) solid nanocubes were used as templates for the formation of a thin carbon shell that encapsulated the active material, thereby preventing the aggregation and maintaining the uniformity. ZHS is then converted into an intermediate ZnS-SnS2 hybrid by a facile thermal sulfidation process. Because SnS2 is insoluble in acidic condition, it is easy to create a yolk-shell architecture by selectively removing the ZnS component. Further heat treatment promoted the melting of SnS2 and resulted in the decomposition of SnS2 into SnS, which is simultaneously accompanied with a heat- and capillary-driven self-assembly to form a SnS inner core and SnS/C double shell. Such nanostructures with an inner void space and robust double shells are useful in buffering the volume expansion of SnS during lithiation and sodiation. Furthermore, N and S atoms doped into the carbon shell can enhance the electrical conductivity, which is beneficial to the fast charge-transfer kinetics. Because of these advantages, YDSC-SnS@NSC as the anode for Li-ion batteries exhibits improved electrochemical properties. Especially, the YDSC-SnS@NSC anode for Na-ion batteries shows an outstanding rate capability of 257 mA h g-1 at 8 A g-1 and an ultrastable long-term cyclic performance at a current density of 1 A g-1 with a capacity retention of 83.5% (340 mA h g-1 at the first cycle and ultimately reached 284 mA h g-1) and only 0.012% capacity decay per cycle for over 1500 cycles. Such superior electrochemical performance demonstrated that this rationally designed anode is promising for application in both Li- and Na-ion storages.