Anode Material For Na-ion Batteries Research Articles

Enhanced electrochemical behavior of Na0.66Li0.22Ti0.78O2/C layered P2-type composite anode material for Na-ion batteries

Within this paper, we present a comprehensive characterization of Na0.66Li0.22Ti0.78O2 – inexpensive, zero-strain anode material for Na-ion batteries in terms of the sodium-ion transport mechanism and electrochemical performance. Na0.66Li0.22Ti0.78O2 was synthesized via a citrate assisted sol-gel method for the first time, which resulted in a four times higher specific surface area as compared to the conventional synthesis method. EIS and DC polarization experiments showed that electrical conductivity in Na0.66Li0.22Ti0.78O2 is mainly ionic with bulk conductivity of 1.54·10−4 S cm−1 at room temperature and enthalpy of Na-ion migration equal to 0.37 eV. Structural changes during intercalation/deintercalation were investigated using operando X-ray diffraction and revealed that lattice parameters monotonically evolve, and P2 structure is maintained during the whole range of sodium insertion/extraction. GITT technique revealed that the chemical diffusion coefficient of sodium changes within two orders of magnitude between 4.8·10−12 cm2 s−1 and 2.5·10−10 cm2 s−1, and such changes were correlated with evolution of occupancy of sodium sites, and contraction of the interlayer gap. Electrochemical tests in both half and full cells show excellent performance of Na0.66Li0.22Ti0.78O2 in a wide range of current loads. The supremacy of sol-gel method fabricated materials is especially visible under high currents (10C), where 60% of theoretical capacity is preserved, which is two times higher than in the materials obtained via a standard high-temperature solid-state reaction. Full cells with a Na0.72Li0.24Mn0.76O2 cathode provided 2.88 V mid-point voltage and a discharge capacity of 132 mAh g−1. Such results prove that Na0.66Li0.22Ti0.78O2 anodes may find their applications in both large-scale energy storage systems and high-power output devices.

Origin of anomalous high-rate Na-ion electrochemistry in layered bismuth telluride anodes

Summary van der Waals layered metal chalcogenide Bi2Te3 has shown exceptional capacity and rate capability in alkali-ion batteries but the underlying reaction mechanism with Li+, Na+, and K+ remains undiscovered. It is unexpected that Na+ electrochemistry outperforms Li+ and K+ at high current densities. Here, in situ transmission electron microscopy is used to uncover nanoscale transformations during lithiation, sodiation, and potassiation, which follows two-step conversion and alloying reactions with Li+ and Na+, and three-step intercalation-conversion-alloying reactions with K+. Counterintuitively, sodiation exhibits the highest reaction kinetics, and its origin can be elucidated by first-principles and finite-element simulations in two aspects. The lower interfacial strain accommodation energy between Bi2Te3 and its Na-conversion products allows more facile sodiation phase transformation than Li- and K-ion reactions. The higher electrochemo-mechanical stress concentration at the concave-shaped sodiation reaction front facilitates continued Na-ion diffusion and reaction propagation. These fundamental insights are essential for fast-charging alkali-ion batteries.

Electrophoretically deposited NiSb2O6-carbon black composite film as a potential anode for sodium-ion battery

In this manuscript, we propose nickel antimony oxide (NiSb 2 O 6 , NSO), crystallized in the tri-rutile form, as a high capacity conversion-type anode material for the sodium-ion batteries. The material is synthesized via co-precipitation method followed by calcination at high temperatures. X-ray diffraction studies confirm the formation of a phase pure tri-rutile NSO powder after calcination at 1000 °C for 5 h. The as-prepared powder is then electrophoretically deposited on a copper foil along with carbon black as conductive additive to develop uniform, porous, and adherent NSO‑carbon black films. The deposited film is then tested as an anode for sodium-ion battery, which delivers a specific capacity of 255mAhg −1 after 50 cycles at a specific current of 100mAg −1 , with a coulombic efficiency of ~98%. The deposited film also exhibits good cycling stability as well as rate capability. Furthermore, the film delivers a specific capacity of 140mAhg −1 after 100 cycles, when cycled at a higher specific current (750mAg −1 ). • NiSb 2 O 6 , a new Na-ion battery anode material is developed. • Electrophoretic deposition method is used to fabricate NiSb 2 O 6 ‑carbon black anode. • EPD grown electrodes exhibit good electrochemical properties.

Prediction of chemically ordered dual transition metal carbides (MXenes) as high-capacity anode materials for Na-ion batteries.

Na-ion batteries have attracted tremendous attention. In this work, various electrochemical properties of three titanium zirconium dual transition metal carbides (TiZrCO2, Ti2ZrC2O2, and TiZr2C2O2) as anode materials for Na-ion batteries are systemically investigated by using density functional theory calculations. Firstly, all these three systems are dynamically stable and exhibit good conductivities. Besides, all of them can realize energetically favorable double-layer adsorption of Na atoms on each side, which endows them with obviously higher capacities than their corresponding mono-titanium- and zirconium-based MXenes. Moreover, their low diffusion energy barriers (<0.3 eV) and suitable open circuit voltages further indicate that these three titanium zirconium dual transition metal carbides are promising anode materials for Na-ion batteries. More importantly, our work opens an avenue to exploit other dual transition metal carbides as high-performance anode materials for Na-ion batteries.

Theoretical investigation of the intercalation mechanism of VS2/MXene heterostructures as anode materials for metal-ion batteries

Ti2CO2 is one of the lightest MXenes, which is beneficial for achieving higher capacity as electrode material for batteries. However, its semiconductor conductivity has a negative effect on its charging/discharging rate and cyclability performance as electrode materials for batteries. Integrating two different two-dimensional materials to form heterostructures is an effective strategy to optimize the properties of materials. In this work, two heterostructures VS2/Ti2CT2 (T = O and S) are constructed and their electrochemical performances as anode materials for Li, Na and Mg-ion batteries are explored based on first-principles calculations. First of all, the lattice mismatch of these two heterostructures are relatively small, particularly, the lattice mismatch of VS2/Ti2CS2 is as low as 0.63%. Besides, compared with common graphene/Ti2CO2 and MoS2/Ti2CO2 heterostructures, VS2/Ti2CT2 simultaneously exhibit superior metal conductivities and stronger adsorption properties towards Li, Na and Mg atoms, thus achieving higher capacities. Considering the strong adsorption properties, suitable diffusion energy barriers, low open circuit voltages and high capacities, VS2/Ti2CO2 and VS2/Ti2CS2 are proposed to be promising high-performance anode materials for Mg-ion batteries, and VS2/Ti2CS2 is a preferable anode material for Na-ion batteries.

Difference in the electron energy loss spectra between the spinel-type Na3LiTi5O12 and Li4Ti5O12 clarified by density functional theory calculations

Li4Ti5O12 is an anode material for Li-ion batteries, and Na3LiTi5O12 is a candidate anode material for Na-ion batteries. Both materials have a spinel framework of Ti–O bonds; hence, the electronic structures are similar. However, the difference between Li4Ti5O12 and Na3LiTi5O12 is detected via electron energy loss spectra (EELS). Density functional theory calculations of the highest energy regions of the titanates show that the difference is caused by the orbital overlaps between the Rydberg orbitals of the O atoms in the 32e sites and alkali metal atoms in the 8a sites. When the 8a sites are occupied by Li, the interaction becomes large, and the peaks in the density of states and EELS become sharp. In contrast, when the 8a sites are occupied by Na, the interaction becomes small, and the peaks in the density of states and EELS become broad. These results imply that the cations in the 8a sites can interact with the Ti–O spinel framework and affect the resulting properties.

Carbon Paper as a Promising Free Standing Anode for Sodium Ion Batteries

Porous conducting carbon fiber composite papers have been developed by a two-step process. This involves fabrication of carbon fiber preform followed by composite formation. Different composite papers have been developed by varying the final heat treatment temperature of the composite, viz. 800 °C, 1100 °C, 1400 °C, 1800 °C and 2300 °C. The study gives an insight as to how the structure, porosity, morphology, electrical and mechanical properties of the carbon/carbon composites vary with temperature; and further the effect of these variations on the performance of the composites as anode material for Na-ion batteries. The sample heat-treated to 800 °C showed high reversible capacity of 278 mAh g−1 at a current density of 37 mA g−1. Additionally, high columbic efficiency (>99%) and 72% retention of the initial capacity has been demonstrated for 1000 cycles. This exceptional performance is attributed to the small crystallite size, large d-spacing and disordered structure of the sample which favors the insertion/de-insertion of sodium ion into the composite anode. Hence, it seems as a promising anode material for sodium-ion batteries.

Hierarchical TiO2 microspheres with enlarged lattice spacing for rapid and ultrastable sodium storage

Intercalation-type TiO2 anode materials have garnered extensive interest for use in Na-ion batteries owing to their low cost and excellent stability. However, such materials are limited by their unsatisfactory specific capacity, particularly at high rates. Herein, we demonstrated the synthesis of hierarchical anatase TiO2 microspheres with enlarged lattice spacings using a simple salt template-assisted spray pyrolysis technique. The broad lattice distance can not only promote ionic transfer but also reduce the band gap with locally enhanced differential charge density, according to density functional theory calculations. Consequently, the resultant sample exhibited reversible specific capacities as high as 362 and 141.8 mA h g−1 at 50 and 5 A g−1, respectively. Impressively, the sample retained specific capacities of 154 mA h g−1 at 1.0 A g−1 after 1600 cycles and of 93.4 mA h g−1 at 5 A g−1 after 7700 cycles. To the best of our knowledge, the Na storage performance of the prepared sample is one of the best among that of TiO2-dominated anode materials. These findings provide new insight into the preparation of novel anode materials for Na-ion batteries with high ionic and electronic conductivities.

Active MoSx Nanoparticle Pillars Embedded in Reduced Graphene Oxide As Anode Materials for High Performance Na-Ion Batteries

As the use of large-scale energy storage devices (i.e. electric vehicles, smart grids.) are increased in recent years, research on the energy storage system is constantly being developed.1 Li-ion batteries are extensively used for energy applications. However, there are some obstacles to its application to large-scale energy systems, such as the limited lithium resources, unstable supply, and cost issues.2 Na-ion batteries have been considered as one of the most promising alternative to Li-ion batteries owing to the low-cost and abundance of sodium element. However, the ionic radius of Na+ (1.06 Å) is larger than Li+ (0.76 Å).3 It leads to severe structural deformation of electrode materials, accompanied by phase change or structural pulverization during cycling.4 To effectively accommodate the larger Na ion into the electrode structure and enhance the cell performance, we need to find suitable anode material for Na-ion batteries. There have been many attempts to develop the carbonaceous electrode materials for Na-ion batteries such as hard carbon, N-doped porous carbon fiber, and expanded graphite.5 , 6 Among them, the expanded graphite alternative could be a good choice due to (i) extended interlayer space for proper accommodation of large Na ions and (ii) stable structural feature with long range order for sufficient stress relaxation during Na intercalation. However, side-reactions between Na ions and a lot of anion pillars (e.g. epoxide and hydroxyl) are often found in the carbon layers, resulted in degradation of the cell performances. Therefore, proper pillar candidate should be introduced to optimize the expanded graphite anode for high performance Na-ion batteries.A representative layered 2-D molydisulfide (MoS2) has been recognized as a promising anode material for Na-ion batteries.7 The MoS2 materials operate via intercalation of sodium at the beginning and a subsequent four-electron conversion reactions.8 The S-Mo-S layer are stacked by van der Waals forces, providing a large interlayer spacing. The large interlayer spacing of MoS2 (~6.2 Å vs. 3.4 Å of graphite) could allow facile transport of Na+ during initial intercalation reaction.9 However, MoS2 has low electronic conductivity and internal strain during sodiation/desodiation. Therefore, many strategies have been considered to develop the cell performance with tailored design, morphology control, (nanocomposite, core-shell structure etc.), and hybridization with carbon materials (carbon nanofibers, amorphous carbon etc.)10 , 11.In this presentation, we introduce the expanded graphite material employing MoSx as bi-functional conversion reaction anode and pillar species between graphite interlayers. The MoSx-expanded graphite anode material synthesized via self-assembly of poly-cationic molybdenum-sulfide source and negatively charged graphite oxide flakes. We demonstrate that the morphological and structural changes of crystalline MoSx pillars under the different thermal temperature in reduction conditions. We attempt to solve the irreversible capacity problems by chemically forming SEI-layer on the electrode surface. We also elucidate the electrochemical reaction mechanisms and structural changes during charge/discharge reaction. M. D. Slater, D. Kim, E. Lee and C. S. Johnson, Adv Funct Mater, 2013, 23, 947-958.Y. Kim, K. H. Ha, S. M. Oh and K. T. Lee, Chem-Eur J, 2014, 20, 11980-11992.Y. Li, Y. Liang, F. C. R. Hernandez, H. D. Yoo, Q. An and Y. Yao, Nano Energy, 2015, 15, 453-461.J. H. Li, H. K. Wang, W. Wei and L. J. Meng, Nanotechnology, 2019, 30.E. Edison, S. Sreejith, C. T. Lim and S. Madhavi, Sustain Energ Fuels, 2018, 2.Y. Wen, K. He, Y. J. Zhu, F. D. Han, Y. H. Xu, I. Matsuda, Y. Ishii, J. Cumings and C. S. Wang, Nat Commun, 2014, 5.J. F. Mao, T. F. Zhou, Y. Zheng, H. Gao, H. K. Liu and Z. P. Guo, J Mater Chem A, 2018, 6, 3284-3303.R. Wang, S. Wang, Y. Zhang, D. Jin, X. Tao and L. Zhang, Nanoscale, 2018, 10, 11165-11175.W. H. Ryu, J. W. Jung, K. Park, S. J. Kim and I. D. Kim, Nanoscale, 2014, 6, 10975-10981.T. S. Sahu and S. Mitra, Sci Rep-Uk, 2015, 5.H. Hou, X. Qiu, W. Wei, Y. Zhang and X. Ji, Adv Energy Mater, 2017, 7, 1602898.

Super-Expanded Graphite Anodes Achieved By Employing Metallic Pillars for High Capacity Sodium-Ion Batteries

Na-ion battery is a promising energy storage systems for future large scale applications to replace the existing Li-ion batteries. Because of the similar structural configuration and electrochemical mechanisms to Li-ion batteries, Na-ion batteries could be potentially realized to the current relevant industries. Utilizing Na resources instead of Li can further alleviate problems regarding (i) localized distribution of lithium resources and (ii) expensive commodity price for Li-ion batteries.[1, 2, 4] However, larger radius of the sodium ion (0.98 Å) than lithium ion (0.69 Å) results in the low electrochemical performance (e.g. capacity, cycle life, and rate capability) for the electrode materials in Na-ion cell.[1] Previous researches to ensure the affordable sites in anode materials have been studied for Na-ion batteries, thereby enabling reversible electrochemical reaction in Na accommodation layer.Graphite is an typical anode material with a theoretical capacity of 350 mAh/g for commercialized lithium ion batteries.[3] However, the graphite materials often suffer from poor capacity issue in Na-ion cells due to low stability and unfavorable intercalation of large Na ion into the graphite layers.[4, 5] In this regard, non-graphitic materials (i.e. hard carbon) exhibiting high capacity around 300 mAh/g have been suggested as an alternative instead of the graphite.[5] However, their expensive material cost and low structural stability resulted from low crystallinity become critical reason to seek better carbon alternatives for Na-ion cells.Expanding the interlayer of graphite has been emerged as a favorable solution to develop carbon based anode material for Na-ion batteries. Extended interlayer space and stable long range order of the expanded graphite anodes enable the excellent electrochemical performance with Na ions.[6] Although there are many advantages of the expanded graphite anodes, parasitic reactions easily occurs between Na ions and a lot of anion pillars (e.g., epoxide and hydroxyl) in the carbon layers easily deteriorate the cell performances. High performance of expanded graphite anodes should be accomplished by developing the strategy to apply proper pillar components between the expanded layers.In this work, we present a simple and powerful strategy to fabricate the expanded graphite anode materials for Na-ion batteries by introducing trivalent (Al3+) and hexavalent (W6+) pillar species between graphene layers.[7] Negatively charged graphene oxide (GO) layers can be self-assembled owing to the electrostatic attractive interaction with positively charged cations in the dispersing solution of GO sheets. As a result, we obviously find out the crystalline planes in regard to super-expanded layers (~7 Å) in contrast with the pristine distance for graphite without any pillars. We examined its morphology and structures of the expanded graphite anode materials and successfully achieved improved electrochemical properties of Na-ion batteries employing the expanded graphite. We will also explain concentration effects of the metal pillars on Na intercalation kinetics in the expanded graphitic anodes for Na-ion batteries. KEYWORDS Na-ion battery, Anode, Expanded graphite, Metallic pillar References [1] Verónica Palomares, Paula Serras, Irune Villaluenga, Karina B. Hueso, Javier Carretero-González and Teófilo Rojo, Energy Environ. Sci., 2012, 5, 5884[2] Won-Hee Ryu, Hope Wilson, Sungwoo Sohn, Jinyang Li, Xiao Tong, Evyatar Shaulsky, Jan Schroers, Menachem Elimelech, and André D. Taylor, ACS Nano, 2016, 10, 3257–3266.[3] Naoki Nitta, Feixiang Wu, Jung Tae Lee and Gleb Yushin, Mater. Today., 2015, 18(5), 252-264.[4] Won-Hee Ryu, Ji-Won Jung, Kyusung Park, Sang-Joon Kim and Il-Doo Kim, Nanoscale, 2014, 6, 10975-10981.[5] Jang-Yeon Hwang, Seung-Taek Myung and Yang-Kook Sun, Chem. Soc. Rev., 2017, 46, 3529-3614[6] Yang Wen, Kai He, Yujie Zhu, Fudong Han, Yunhua Xu, Isamu Matsuda, Yoshitaka Ishii, John Cumings & Chunsheng Wang, Nat. Commun., 2014, 5, 4033[7] Seongji Pyo, Wonsik Eom, You Jin Kim, Sang Hoon Lee, Tae Hee Han, Won-Hee Ryu (in press). Super-Expansion of Assembled Reduced Graphene Oxide Interlayers by Segregation of Al Nanoparticle Pillars for High-Capacity Na-Ion Battery Anodes., ACS Appl. Mater. Interfaces., doi: 1021/acsami.0c00659

Indium-Doped Rutile Titanium Oxides As Anode Materials for Na-Ion Batteries

Na-ion batteries (NIBs) have been recently considered as an attractive alternative to Li-ion batteries (LIBs) for large-sized rechargeable batteries because Na’s resource has a lower cost and a wider availability compared to Li’s resource. Na+ has a 2.4 times larger ionic volume than Li+, resulting in slower kinetics of its host materials of negative electrode (anodes). We have recently developed various compounds as novel anode materials of NIB [1-6], and have particularly focused on rutile-type TiO2 with very favorable ion-diffusion path along its c-axis. However, rutile TiO2 has two problems as anode materials: the very low diffusion coefficient along ab in-plane direction and the poor electronic conductivity.To address the issues, the authors have conducted two kinds of approaches: the doping of impurity elements into the crystal structure [1] and the improvement in the crystallinity of TiO2 particles [2]. The approaches could improve the electronic conductivity and the trapping at grain boundaries, leading to a remarkable enhancement in the anode performances. In particular, the Nb-doped TiO2 electrode [6] and Ta-doped TiO2 electrode [5] showed remarkably-enhanced anode performances. Nevertheless, there still remains a serious problem that the capacity steeply increases or decreases in the initial several tens of cycles even by Nb-doping and Ta-doping. The dopings of Nb and Ta have another effect of expanding crystal lattice of rutile TiO2 because the sites of Ti4+ (ionic diameter: 121 pm) are substituted with Nb5+ (128 pm) and Ta5+ (128 pm). This expansion is accompanied by an increase in size of Na+ diffusion path, which is favorable for improving the Na+ insertion−extraction properties. Since the ionic diameter of Na+ (204 pm) is larger than that of Li+ (152 pm), the size expansion of ion diffusion path is more important for NIB compared with LIB.Indium (In) has a much larger ionic size of 160 pm than Nb and Ta. It is thus expected that the larger size will change the doping effects on Na+ insertion−extraction properties. In the previous study, the authors have not systematically investigated the dependence of In doping amount on the anode properties. Therefore, in this study, we evaluated the anode properties of In-doped rutile electrodes with various doping amounts to clarify the influence of In doping. In addition to this, we used an anionic surfactant for the hydrothermal synthesis of TiO2 to reduce its particle length [6].We prepared In-doped rutile TiO2 by a facile one-pot hydrothermal synthesis [6-8]. For the reduction of the particle length, we used a solution of the anionic surfactant (Sodium dodecyl sulfate: SDS) for the synthesis. We investigated the influences of In doping and the particle morphology on the Na+ storage properties. The X-ray diffraction analyses revealed that the solid solubility limit was found to be 0.8 at.% in In-doped TiO2. With increasing the In amount from to 0.8 at.%, the lattice parameters of rutile TiO2 were increased, indicating the expansion of diffusion path size for Na+. The degree of size expansion by In doping is comparable to the change by 6 at.% of Nb doping. The remarkable feature is that the similar size increasing can be achieved even with a much smaller doping amount in the case of In doping because of its larger ionic size. The improvement in the electronic conductivity was also confirmed by 0.8 at.% In doping into TiO2.In the case where no surfactant was used, the best anode performance was obtained for 0.8 at.%. In-doped TiO2 electrode by the benefits of three doping effects: (i) expanded diffusion-path size, (ii) improved electronic conductivity, and (iii) reduced electron charge density in the path. A further enhancement in the performance was achieved for the In-doped TiO2 with a reduced particle-length by the synthesis in the SDS surfactant solution. This electrode exhibited a better cycle stability, and maintained high discharge capacities of 240 mA h g−1 for 200 cycles. The reason is probably that Na+ can be inserted in the inner part of TiO2 particles because of its reduced particle-length.

Mechanical Behavior of Na-Ion Battery Anode Material

Na-ion batteries (NIB) are been developed as an alternative to Li-ion batteries due to cost and scarcity of Li metal, but one of the major issues is capacity fade due to stress generation in electrodes during sodiation/desodiation process. Stress generation occurs due to volume expansion of Na when it alloys and dealloys with the anode. Here, we chose Ge as a representative anode material and measured its stress response during sodiation/desodiation cycling. The mechanical behavior of Ge due to sodiaiton/desodiation is compared and contrasted with that due to lithation/delithation. In this talk the interesting observations from this in-situ measurements and their implications will be presented.

P-doped CoSe2 nanoparticles embedded in 3D honeycomb-like carbon network for long cycle-life Na-ion batteries

We report for the first time a Na-ion battery anode material composed of P-doped CoSe2 nanoparticles (P-CoSe2) with the size of 5–20 nm that are uniformly embed in a 3D porous honeycomb-like carbon network. High rate capability and cycling stability are achieved simultaneously. The honeycomb-like carbon network is rationally designed to support high electrical conductivity, rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe2 nanoparticles. In particular, heteroatom P-doping within CoSe2 introduces stronger P-Co bonds and additional P-Se bonds that significantly improve the structure stability of P-CoSe2 for highly stable sodiation/desodiation over long-term cycling. P-doping also improves the electrical conductivity of the CoSe2 nanoparticles, leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities. Benefiting from the unique nanostructure and atomic-level P-doping, the P-CoSe2(2:1)/C anode delivers an excellent cycle stability with a specific capacity of 206.9 mA h g−1 achieved at 2000 mA g−1 after 1000 cycles. In addition, this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach. This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials.

TiO2 nanotube/g-C3N4/graphene composite as high performance anode material for Na-ion batteries

To improve the electrochemical kinetics and alleviate the structural collapse of TiO2 in the process of charge/discharge, TiO2 nanotubes (TiO2NT) anchored on a large-area graphitic carbon nitride/reduced graphene oxide (g-C3N4/RGO) hybrid nanosheets have been designed by alkaline hydrothermal method. This unique architecture ensures the uniform distribution of TiO2NT and inhibits the natural tendency to agglomeration of RGO to a large extent. When applied as anode material for Na-ion batteries (NIBs), the resultant sample delivers high reversible capacities of 138.5 mAh g−1 after 244 cycles at 0.1 A g−1 and good rate capability (103.3 mAh g−1 at 0.8 A g−1). These excellent sodium storage behaviors are attributed to the double coating effect of g-C3N4/RGO nanosheets on TiO2 nanotubes, which can reduce the volume change in the cycle. Therefore, TiO2 nanotubes/graphite phase carbon nitride/graphene composite (TiO2NT/g-C3N4/RGO) should be a promising and attractive NIBs anode material.

Sb-based intermetallics and nanocomposites as stable and fast Na-ion battery anodes

To achieve high-performance Sb-based anodes for Na-ion battery (NIB), various approaches for obtaining amorphous C-containing Sb composite (Sb@C), Sb-based intermetallic compounds (TiSb2 and NbSb2), and Na-inactive metal carbide and amorphous C-containing Sb composites (Sb@TiC@C and Sb@NbC@C) have been introduced. First, Sb@C was prepared using a simple solid-state ball-milling, and then its potential as a NIB anode material was investigated. The electrochemical phase change mechanism of Sb during the sodiation/desodiation of Sb@C was investigated using various ex situ analytical techniques. Sb was found to sequentially transform into NaSb and Na3Sb during sodiation and NaSb and Sb during desodiation. Second, as another trial to further improve the electrochemical performance of Sb, Sb-based intermetallic compounds of TiSb2 and NbSb2 were synthesized by alloying reaction via a simple solid state heat-treatment and their potential as NIB anode materials was investigated. Lastly, the Sb@TiC@C and Sb@NbC@C nanocomposites comprising tiny (~3–5 nm) Sb nanocrystallites and Na-inactive metal carbide (TiC/NbC) matrix embedded in buffering amorphous C were synthesized by alloying and dealloying reaction. The Sb@TiC@C and Sb@NbC@C demonstrated highly reversible, stable capacity (Sb@TiC@C: 746 mAh cm−3, Sb/NbC/C: 726 mAh cm−3 after 100 cycles) and fast rate capability with exceptional capacity retentions after 400 cycles (Sb@TiC@C: ~710 mAh cm−3 at 2 C rate, Sb@NbC@C: ~680 mAh cm−3 at 2 C rate). Therefore, the Sb-based nanocomposites synthesized by alloying and dealloying are considered to be possible new anode materials for use in high-performance NIBs.

Sodium Storage Mechanism Investigations through Structural Changes in Hard Carbons

Hard carbons, due to their relatively low cost and good electrochemical performance, are considered the most promising anode materials for Na-ion batteries. Despite the many reported structures of ...

Hard carbon derived from coconut shells, walnut shells, and corn silk biomass waste exhibiting high capacity for Na-ion batteries

Hard carbons derived from renewable biomass were explored as anodes for Na-ion batteries and delivered a high reversible capacity (315 mAh g −1 ) and capacity retention (93%). An “adsorption-intercalation” mechanism is proposed to explain the observed performances. In recent years, hard carbon materials have gained significant interest as anode materials for Na-ion batteries. Biomass waste is considered one of the most interesting, renewable, available, and cost-effective precursor to obtain hard carbon (HC); however, HC properties must be finely tuned to achieve performance comparable to those provided by Li-ion batteries. In this work, three biomass wastes (coconut shells, walnut shells, and corn silk) were evaluated as potential precursors for HC preparation involving a pyrolysis process and subsequent acid washing to remove the inorganic impurities. All obtained materials exhibited low and similar specific surface areas (<10 m 2 ⋅g −1 ), but they presented different structures and surface functionalities. The walnut shell HC possessed a lower amount of inorganic impurities and oxygen-based functional groups compared to the coconut shell and corn silk HCs, leading to higher initial coulombic efficiency (iCE). The structural organization was higher in the case of the walnut shell HC, while the corn silk HC revealed a heterogeneous structure combining both highly disordered carbon and localized graphitized domains. All HCs delivered high initial reversible capacities between 293 and 315 mAh g −1 at 50 mA g −1 current rate, which remained rather stable during long-term cycling. The best capacity (293 mAh g −1 after 100 charge/discharge cycles) and highest capacity retention (93%) was achieved in walnut HCs in half-cells, which could be associated with its higher sp 2 C content, better organized structure, and fewer impurities. An “adsorption-insertion” Na storage mechanism is suggested based on several techniques. The walnut HCs exhibited an attractive energy density of 279 Wh/kg when tested in full cells.

Carbon-encapsulated Sb6O13 nanoparticles for an efficient and durable sodium-ion battery anode

In this communication, nano-thin carbon-encapsulated Sb6O13 nanoparticles (Sb6O13NPs@C) synthesized innovatively in a one-pot manner were demonstrated as a high-performance anode material for Na-ion batteries. The synthesized Sb6O13NPs@C bearing irregular nanopores showed an average size of around 60 nm and possessed the 13.6 wt% carbon shell composition, with the mesopores generated by the Sb6O13NPs@C aggregation. The as-assembled Na-ion battery with Sb6O13NPs@C exhibited both excellent rate performance (the capacity of as high as 239 mA h g−1 at a current density of 1000 mA g−1) and cycling stability (89.64% capacity retained after 170 cycles). The in-depth understanding of the working principle of the Sb6O13NPs@C nanocomposite anode for the Na-ion battery was also provided.

First-principles study of a substitutionally doped phosphorene as anode material for Na-ion batteries

An effective strategy to design high-performance anode materials is a significant task for rechargeable batteries technologies. Recently, sodium-ion batteries have attracted extensive attention because can be considered as an alternative for lithium-ion batteries in large-scale renewable energy storage applications due to abundant sodium resources and similar electrochemical mechanisms. In this paper, the first-principles density-functional theory calculations have been carried out to estimate the potential prospects of substitutionally doped monolayer of black phosphorus (BP) as an anode material for Na-ion batteries. It was found that the BP monolayer has negative binding energies for Sc, Co, Cu, B, F, and Cl dopants. Moreover, it was also shown that after sodium adsorbing, F and Cl atoms diffuse from phosphorene lattice on the surface of Na, which eliminates these materials from application in energy storage systems. Given these advantages, it is expected that Sc-, Co-, Cu- and B-doped phosphorus monolayers are promising anode materials for Na-ion batteries, with a maximum value of specific capacity of 438.6 mAh/g for B-doped system.

Density functional theory study on the Ti3CN and Ti3CNT2 (T = O, S and F) as high capacity anode material for Na ion batteries

MXenes are the promising anode materials for the Na ion batteries (NIBs) because of their high ion capacity and low diffusion barrier to Na. The surface groups have great influence on the energy storage properties. In this paper, we performed density functional theory (DFT) calculation to study the adsorption energies, diffusion behaviors and electronic properties of Na on the Ti3CN and Ti3CNT2 monolayers (T = O, S and F functional groups). The surfaces on N and C sides of Ti3CNT2 monolayer have different adsorption behaviors to Na. The Ti3CNO2 and Ti3CNS2 exhibit better adsorptive properties to Na with the adsorption energy (Ead) of −1.702 eV and −1.626 eV, while the F functional group can reduce the value of Ead. The diffusion barriers of Na on the Ti3CNO2 and Ti3CNS2 are only 0.037 eV and 0.045 eV, which could enable the NIBs to have very fast charge/discharge rate. The theoretical capacities of Na on Ti3CNO2, Ti3CNS2 and Ti3CNF2 can reach 530 mAh g−1, 458 mAh g−1 and 516 mAh g−1, respectively. The results show that the Ti3CN, Ti3CNO2 and Ti3CNS2 can be promising anode materials for NIBs.