High-performance Sodium-ion Batteries Research Articles

Liquid Gallium-Assisted Pyrolysis of MOF Affording CNT Non-Hollow Frameworks in High Yields for High-Performance Sodium-Ion Battery Anode.

Carbon materials have great potential for applications in energy, biology, and environment due to their excellent chemical and physical properties. Their preparation by carbonization methods encounters limitations and the carbon loss during pyrolysis in the form of gaseous molecules results in low yield of carbon materials. Herein a low-energy (600°C) and high-yield (82wt.%) carbonization strategy is developed using liquid gallium-assisted pyrolysis of metal-organic frameworks (MOFs) affording the N-doped carbon nanotube (CNT) non-hollow frameworks encapsulating Co nanoparticles. The liquid gallium layer offers protection against air, promotes heat transfer, and limits the escape of small carbonaceous gaseous molecules, which greatly improve the yields of the pyrolysis reaction. Experimental and theoretical results reveal that the synergistic interaction between CNTs and N/O-containing groups gives a non-hollow framework composed of N/O-enriched and open CNTs (NOCNTF-15, 15 denotes the 15mm thickness of the liquid gallium layer during the pyrolysis) with high specific capacity (185mAhg-1 at 10Ag-1) and ultra-stable cyclability (stable operation at 10Ag-1 and 50°C for 20000 cycles). This study provides a unique approach to carbonization that facilitates the practical application of low-cost CNTs and other MOFs-derived carbon materials in high-performance sodium-ion batteries (SIBs).

Heterogeneous carbon coated resin-based hard carbon anode material for high-performance sodium ion batteries

Resin-based hard carbons are promising anode materials for sodium ion batteries (SIBs) due to their high storage capacity and purity. However, the low initial coulombic efficiency (ICE) still hinders their practical application. Crosslinking and high-temperature pyrolysis strategies have been demonstrated to improve ICE effectively, but the complex process and high energy consumption hinder their industrialization. This paper proposes a facile synthesis of resin-based hard carbon with a soft carbon coating strategy to improve ICE. By carbonizing commercial phenolic resin at 1150℃, hard carbon with a reversible capacity of 291.6 mAh g−1 and 82.6 % ICE was obtained. After asphalt-based soft carbon coating, the optimized sample (CHC-1150) with a heterogeneous carbon coating layer of about 8.5 nm displays a high reversible capacity and ICE of 309.8 mAh g−1 and 88.2 %. Moreover, when combined with NaFe1/3Ni1/3Mn1/3O2 cathode, the assembled 18650 cylindrical-type batteries deliver a high ICE of 84.3 %, excellent low-temperature capability and cycling stability. Additionally, the disassembly results after cycling indicate that the soft carbon layer can inhibit the decomposition of electrolytes and avoid sodium plating. These encouraging results suggest that heterogeneous carbon coating should be a promising strategy to promote the electrochemical performance of resin-based hard carbon anode materials for SIBs.

In situ heating-induced loading of anion-rich vacancy Mo–Fe1-xS nanoparticles on mesoporous carbon for high-performance sodium-ion batteries

Inspiriting the kinetics of transition metal sulfide-based anodes is key to optimizing rate performance and cycling stability. To this end, the controllable anion vacancy and large specific surface area are considered as powerful means to improve the performance of sodium-ion batteries due to their unique physical and chemical properties and convenient transport paths. Hence, we have generated Fe3+/MoO42−@cystine nanosheets by solvothermal reaction with iron molybdate nanosheets using cysteine as a sulfur and carbon source. in situ environmental transmission electron microscopy demonstrates that the Fe3+/MoO42−@cystine nanosheets calcined under a vacuum state undergo significant structural evolution, consequentially, the decomposition and carbonization of cystine induces the generation of mesoporous structures with increasing temperature. In the half-cell, Mo–Fe1-xS@mesoporous nitrogen doped carbon-600 showed excellent rate capability at current densities of 0.1–5 A g−1, as well as excellent cycling performance (428.9 mAh g−1 at 2.0 A g-1 after 800 cycles). Mesoporous nitrogen doped carbon and sulfur vacancies induced enhanced conductivity, fast ionic transfer and structural stability, resulting in excellent electrochemical performance of Mo–Fe1-xS@mesoporous nitrogen doped carbon under calcination at 600 °C (Mo–Fe1-xS@MCN-600).

Unlocking the potential of a chemically modified blue phosphorene as anode materials for high-performance sodium-ion batteries

Blue phosphorene (Blu-Pn) has recently been identified as a new two-dimensional (2D) form of black phosphorus via the epitaxial growth method and has shown the ability to host a substantial amount of Na while serving as an anode in sodium-ion batteries (NIBs). However, its structural instability is an issue that hinders its further exploitability in NIBs. In this paper, we propose to chemically modify the Blu-Pn network by substituting six phosphorus atoms with a carbon source in the form of a C6 ring, constructing a new and robust CP2 nanosheet. Based on the state-of-the-art non-local van der Waals corrected density functional theory and ab initio molecular dynamic (AIMD) simulations, we systematically explore the feasibility of the designed CP2 as a potential anode material for NIBs. Adding a C6 ring in the Blu-Pn lattice reduces its energy gap from 2 eV to 1.3 eV, which disappears after Na adsorption, indicating a conductive character. Attributed to the synergistic effect, the adsorption energy of Na on CP2 nanosheet (−2.22 eV) is greatly decreased in comparison to the pristine carbon source (e.g., graphene with −0.78 eV) and pristine Blu-Pn (−1.85 eV). The Na diffusivity on CP2 at 300 K is predicted to be 4.90 × 10−11 m2/s by AIMD. The specific capacity is up to 604.1 mAh/g, which exceeds that of the commercialized graphite anode (372 mA h/g). Ultimately, the designed electrode provides a small open circuit potential of 0.66 V that falls within a desirable voltage range. This work paves the way for exploring Blu-Pn 2D anode materials for NIBs technology and provides valuable insights into surface chemical modification towards the long-term stability of Blu-Pn.

Insight into the configuration of hard-soft carbon composites for high performance sodium-ion batteries

Hard carbon materials are considered suitable anode materials for sodium-ion batteries due to their abundant defect sites and large interlayer distance, which are respectively beneficial to the adsorption/desorption and insertion/extraction behaviors of Na+ during the electrochemical process. However, the poor electrical conductivity resulting from the intrinsic short-range ordered structure in the carbon skeleton and limited active sites significantly hinders their electrochemical performance. Herein, hard and soft carbon composites with various configurations are developed using a layer-by-layer coating method with SiO2 nanospheres as templates. These composites, including the hard carbon coated soft carbon composite structure (SC@HC), soft carbon coated hard carbon composite structure (HC@SC), and uniformly mixed soft and hard carbon composites (HSC), are prepared through confined-carbonization under the outermost SiO2 layer. The resulting hollow nanospheres possess ultra-small diameters (approximately 50 nm), ultra-thin wall thicknesses (5-6 nm), and different hard/soft carbon layer arrangements. Evaluation of sodium storage properties showed that the combination of soft and hard carbon outperformed pure soft or hard carbon, with HC@SC configuration offering materials with larger interlayer spacing, higher defect concentration, and a more complete conductive network. This enhances sodium storage capacity (293 mAh g-1@1 A g-1) and rate performance (242 mAh g-1@5 A g-1). The findings of this study present a novel approach to designing soft and hard carbon composites for high-performance sodium-ion batteries.

Topotactic Syntopogenous Sodium Vanadium Fluoride for High-Performance Sodium-Ion Batteries: Electron and Sodium-Ion Reservoirs in Perovskite/Diperovskite Superlattice.

In order to simultaneously accelerate ion and electron transfer in sodium-ion battery (SIB) cathodes, a topotactic superlattice was utilized, in which the atomically intrinsic lattice-matching effect from inner to external surface can boost the charge transfer due to the disappearance of the heterojunction interface. Herein, a topotactic syntopogenous Na3VF6/NaVF3 superlattice formulated as Na2.9V1.1F6 (NVF) was synthesized by a facile one-step low-temperature hydrothermal reaction. NVF nanoparticles show an excellent Na+ storage capacity (∼205 mAh g-1) in a high voltage window up to 4.2 V with ultralong cycling stability. That is associated with the mixed occupancy of V and Na in NVF. The multivalent V centers serve as electron reservoirs to inhibit phase transformation, and the Na-enriched Na3VF6 with better electron conductivity acts as a Na+ reservoir for effective electron transfer. Highly reversible (de)intercalation of Na+ is achieved in the channel of perovskite-type NaVF3 with structural integrity.

Steric Hindrance Engineering to Modulate the Closed Pores Formation of Polymer-Derived Hard Carbon for High-Performance Sodium-Ion Batteries.

The closed pores play a critical role in improving the sodium storage capacity of hard carbon (HC) anode, however, their formation mechanism as well as the efficient modulation strategy at molecular level in the polymer-derived HCs is still lacking. In this work, the steric hindrance effect has been proposed to create closed pores in the polymer-derived HCs for the first time through grafting the aromatic rings within and between the main chains in the precursor. The experimental data and theoretical calculation demonstrate that steric-hindrance effect from the aromatic ring side group can increase backbone rigidity and the internal free volumes in the polymer precursor, which can prevent the over graphitization and facilitate the formation of closed pores during the carbonization process. As a result, the as-prepared HC anode exhibits a remarkably enhanced discharge capacity of 340.3 mAh/g at 0.1 C, improved rate performance (210.7 mAh/g at 5 C) as well as boosted cycling stability (86.4% over 1000 cycles at 2C). This work provides a new insight into the formation mechanisms of closed pores via steric hindrance engineering, which can shed light on the development of high-performance polymer-derived HC anode for sodium-ion batteries.

Cu-Doped Spherical P2-Type Na0.7Fe0.23-xCuxMn0.77O2 Cathode for High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs), owing to their abundant resources and cost-effectiveness, have garnered considerable interest in the realm of large-scale energy storage. The properties of cathode materials profoundly affect the cycle stability and specific capacity of batteries. Herein, a series of Cu-doped spherical P2-type Na0.7Fe0.23-xCuxMn0.77O2 (x = 0, 0.05, 0.09, and 0.14, x-NFCMO) was fabricated using a convenient hydrothermal method. The successful doping of Cu efficaciously mitigated the Jahn-Teller effect, augmented the electrical conductivity of the material, and diminished the resistance to charge transfer. The distinctive spherical structure remained stable and withstood considerable volumetric strain, thereby improving the cyclic stability of the material. The optimized 0.09-NFCMO cathode exhibited a high specific capacity of 168.6 mAh g-1 at 100 mA g-1, a superior rate capability (90.9 mAh g-1 at 2000 mA g-1), and a good cycling stability. This unique structure design and doping approach provides new insights into the design of advanced electrode materials for sodium-ion batteries.

Ultrathin porous carbon nanosheets with enhanced surface energy storage for high-performance sodium-ion batteries

Ultrathin porous carbon nanosheets with enhanced surface energy storage for high-performance sodium-ion batteries

Low cobalt single atoms loading on N-doped carbon for high Na storage performance

Cobalt single atoms on nitrogen-doped carbon (CoSAs/N-C) were successfully synthesized through the pyrolysis of metal-organic supramolecular self-template. Only 0.12 wt% metal-doped CoSAs/N-C anodes bring a rate capacity enhancement of 195 mAh g−1 compared to the blank group of nitrogen-doped carbon electrodes at 0.1 A g−1. In addition, the CoSAs/N-C anodes exhibit remarkable sodium-ion storage capacities of 285 mAh g−1 after 2000 cycles at 1.0 A g−1 and 133 mAh g−1 with an exceptional cycling stability for 10,000 cycles at an ultra-high current density of 20 A g−1, thereby showcasing excellent Na ion storage performance. Ex-situ X-ray photoelectron spectroscopic study demonstrates that some N atoms in CoSAs/N-C can reversibly store and release Na ions during discharge and charge cycles. The full cell assembled with CoSAs/N-C anode and Na3V2(PO4)3 cathode displays Coulombic efficiency of >99.7 % after 200 cycles at 0.5 A g−1. Density functional theory (DFT) calculations further reveal that the presence of single-atom Co results in a decrease in the Na binding energy surrounding pyrrolic-N and pyridinic-N structures. This moderate binding energy may be beneficial for Na ion adsorption and desorption. This study opens up new possibilities of fabricating advanced metal single atom anodes for high-performance sodium-ion batteries.

BC6NA monolayer as an ideal anode material for high-performance sodium-ion batteries

Selecting an appropriate anode material (AM) has been considered to be a crucial initial step in advancing high-performance batteries. Within this piece of research, we examine the suitability of the BC6NA monolayer (referred to as BC6NAML) as an AM by first-principles calculations. The BC6NAML exhibits metallic behavior consistently, even with varying concentrations of Na atoms, making it an ideal choice for battery usages. Our findings revealed that the theoretical storage capacity for Na-adhered BC6NAML was 406.36 mAhg-1, surpassing graphite, TiO2, BC6NA, and numerous other 2D materials. The BC6NAML also demonstrates a diffusion barrier of 0.39 eV and favorable diffusivity of Na-ions. Although the open-circuit voltage (OCV) of BC6NAML was temperate and lower compared to the OCV of other AMs like TiO2, our results suggested that it is possible to utilize BC6NAML as one of the encouraging host materials for sodium-ion batteries (SIBs). Consequently, this investigation into the potential anodic application of BC6NAML proves valuable for future experimental studies into sodium storage for SIBs.

Small-molecule organic electrode materials on carbon-coated aluminum foil for high-performance sodium-ion batteries

Organic molecular electrode materials are promising candidates in batteries. However, direct application of small molecule materials usually suffers from drastic capacity decay and inefficient utilization of active materials because of their high solubility in organic electrolytes and low electrical conductivity. Herein, a simple strategy is found to address the above issues through coating the small-molecule organic materials on a commercialized carbon-coated aluminum foil (CCAF) as the enhanced electrode. Both the experimental and calculation results confirm that the relatively rough carbon coating on the aluminum foil not only exhibits superior adsorption capacity of small-molecule organic electrode materials with a tight contact interface but also provides continuous electronic conduction channels for the facilitated charge transfer and accelerated reaction kinetics. In addition, the carbon coating also inhibits Al corrosion in electrochemical process. As a result, by using the tetrahydroxy quinone-fused aza-phenazine (THQAP) molecule as an example, the THQAP-CCAF electrode exhibits an excellent rate performance with a high capacity of 220 and 180 mAh g−1 at 0.1 and 2 A/g, respectively, and also a remarkable cyclability with a capacity retention of 77.3% even after 1700 cycles in sodium-ion batteries. These performances are much more superior than that of batteries with the THQAP on bare aluminum foil (THQAP-AF). This work provides a substantial step in the practical application of the small-molecule organic electrode materials for future sustainable batteries.

Transition Metal Selenide-Based Anodes for Advanced Sodium-Ion Batteries: Electronic Structure Manipulation and Heterojunction Construction Aspect.

In recent years, sodium-ion batteries (SIBs) have gained a foothold in specific applications related to lithium-ion batteries, thanks to continuous breakthroughs and innovations in materials by researchers. Commercial graphite anodes suffer from small interlayer spacing (0.334 nm), limited specific capacity (200 mAh g-1), and low discharge voltage (<0.1 V), making them inefficient for high-performance operation in SIBs. Hence, the current research focus is on seeking negative electrode materials that are compatible with the operation of SIBs. Many studies have been reported on the modification of transition metal selenides as anodes in SIBs, mainly targeting the issue of poor cycling life attributed to the volume expansion of the material during sodium-ion extraction and insertion processes. However, the intrinsic electronic structure of transition metal selenides also influences electron transport and sodium-ion diffusion. Therefore, modulating their electronic structure can fundamentally improve the electron affinity of transition metal selenides, thereby enhancing their rate performance in SIBs. This work provides a comprehensive review of recent strategies focusing on the modulation of electronic structures and the construction of heterogeneous structures for transition metal selenides. These strategies effectively enhance their performance metrics as electrodes in SIBs, including fast charging, stability, and first-cycle coulombic efficiency, thereby facilitating the development of high-performance SIBs.

Zero-strain Co-doped Na2FeP2O7/carbon delivers superior rate capability and long-cycle stability for sodium ion batteries

Na2FeP2O7 cathode material exhibits great promise in sodium ion batteries (SIBs), due to its low cost and high structural durability. Nevertheless, the intrinsically poor electronic conductivity and sluggish Na+ diffusion kinetics of Na2FeP2O7 hinder its practical application. Herein, a synergistic cooperation of continuous amorphous carbon layer and optimized Co doping strategy is proposed to design high-performance SIB cathode (Co-doped Na2FeP2O7/C) via in-situ sol–gel method, where Co integration significantly enhances both the electronic conductivity and the Na+ diffusion kinetics, as confirmed by the combination of ex/in-situ characterizations and density functional theory calculations. Valuably, the synergy of amorphous carbon layer and appropriate Co doping restrains the structure stress to “zero-strain”, Which remains beneficial for 0.10Co-NFO@C to display a high capacity of 96.12 mAh g-1 at 0.05C and a high-rate capacity of 61.75 mAh g-1 at 60C with the capacity retention of 79.9% after 5000 cycles. Moreover, optimized Co-doped Na2FeP2O7/C also shows outstanding cycling performance and rate capability when assembled into full batteries (hard carbon as the anode), demonstrating a reversible capacity of ∼110.9 mAh g-1 at 50 mA g−1, and a respectable capacity retention of 78.0% at 500 mA g−1 for 500 cycles. The strategy inspires new advances towards zero-strained cathode materials for high performance SIBs.

A Unique Wide-Spacing Fence-Type Superstructure for Robust High-Voltage O3-Type Sodium Layered Cathode.

Enhancing the energy density of layered oxide cathode materials is of great significance for realizing high-performance sodium-ion batteries and promoting their commercial application. Lattice oxygen redox at high voltage usually enables a high capacity and energy density. But the structural degradation, severe voltage decay, and the resultant poor cycling performance caused by irreversible oxygen release seriously restrict the practical application. Herein we introduce a novel fence-type superstructure (2a × 3a type supercell) into O3-type layered cathode material Na0.9Li0.1Ni0.3Mn0.3Ti0.3O2 and achieve a stable cycling performance at a high voltage of 4.4 V. The fence-type superstructure effectively inhibits the formation of the vacancy clusters resulting from out-of-plane Li migration and in-plane transition metal migration at high voltage due to the wide d-spacing, thereby significantly reducing the irreversible release of lattice oxygen and greatly stabilizing the crystal structure. The cathode exhibits a high energy density of 545 Wh kg-1, a high rate capability (112.8 mAh g-1 at 5C) and a high cycling stability (85.8%@200 cycles with a high initial capacity of 148.6 mAh g-1 at 1C) accompanied by negligible voltage attenuation (98.5%@200 cycles). This strategy provides a distinct spacing effect of superstructure to design stable high-voltage layered cathode materials for Na-ion batteries.

Conductive polymer-coated red phosphorus encapsulated in 3D graphene oxide aerogel for high-performance sodium-ion batteries anode

Relying on the high theoretical capacity for sodium storage, red phosphorus (RP) has attracted tremendous attention. However, its utilization is confronted with numerous limitations, such as substantial volume expansion and inferior conductivity. Herein, a RP anode (P/PPy@rGO) coated by conductive polypyrrole (PPy) was encapsulated in a spatially self-assembled reduced graphene oxide (rGO) aerogel by electrostatic interaction. The coating of PPy can not only enhance the conductivity of RP effectively, but also facilitate the connection between RP and rGO. Moreover, the rGO aerogel can accommodate the volume expansion of RP. Benefited from this unique structure, the P/PPy@rGO electrode can exhibit an enhanced rate performance (619 mAh/g at 5.2A g−1) and excellent cycling stability with a capacity retention of 89.5 % after 100 cycles. This work would contribute to the suitable design of phosphorus-based anode for sodium storage.

Rapid synthesis of two-dimensional MoB MBene anodes for high-performance sodium-ion batteries

Two-dimensional (2D) transition metal borides (MBenes) have emerged as a rising star and hold great potential promise for catalysis and metal ion batteries owing to a well-defined layered structure and excellent electrical conductivity. Unlike well-studied graphene, perovskite and MXene materials in various fields, the research about MBene is still in its infancy. The inadequate exploration of efficient etching methods impedes their further study. Herein, we put forward an efficient microwave-assisted hydrothermal alkaline solution etching strategy for exfoliating MoAlB MAB phase into 2D MoB MBenes with a well accordion-like structure, which displays a remarkable electrochemical performance in sodium ion batteries (SIBs) with a reversible specific capacity of 196.5 mAh g–1 at the current density of 50 mA g–1, and 138.6 mAh g–1 after 500 cycles at the current density of 0.5 A g–1. The underlying mechanism toward excellent electrochemical performance are revealed by comprehensive theoretical simulations. This work proves that MBene is a competitive candidate as the next generation anode of sodium ion batteries.

Demineralization activating highly-disordered lignite-derived hard carbon for fast sodium storage

Lignite, as one of the coal materials, has been considered a promising precursor for hard carbon anodes in sodium-ion batteries (SIBs) owing to its low cost and high carbon yield. Nevertheless, hard carbon directly derived from lignite pyrolysis typically exhibits highly ordered microstructure with narrow interlayer spacing and relatively unreactive interfacial properties, owing to the abundance of polycyclic aromatic hydrocarbons and inert aromatic rings within its molecular composition. Herein, an innovative demineralization activating strategy is established to simultaneously modulate the interfacial properties and the microstructure of lignite-derived carbon for the development of high-performance SIBs. Demineralization process not only creates numerous void spaces in the matrix of lignite precursor to assist aromatic hydrocarbon rearrangement, thereby reducing the ordering and expanding interlayer spacing, but also exposes more interfacial oxygen-containing functional groups to effectively increasing the sodium storage active sites. As a result, the optimal demineralized lignite-derived hard carbon (DLHC 1300) delivers a high reversible capacity of 335.6 mAh/g at 30 mA g−1, superior rate performance of 246.3 mAh/g at 6 A/g and nearly 100 % capacity retention after 1100 cycles at 1A/g. Furthermore, the optimized DLHC 1300 material functions as an outstanding anode in sodium ion full cells. This work significantly advances the development of low-cost, high-performance commercial hard carbon anodes for SIBs.

Selective Lattice Doping Enables a Low-Cost, High-Capacity and Long-Lasting Potassium Layered Oxide Cathode for Potassium and Sodium Storage.

Layered transition metal oxides are highly promising host materials for K ions, owing to their high theoretical capacities and appropriate operational potentials. To address the intrinsic issues of KxMnO2 cathodes and optimize their electrochemical properties, a novel P3-type oxide doped with carefully chosen cost-effective, electrochemically active and multi-functional elements is proposed, namely K0.57Cu0.1Fe0.1Mn0.8O2. Compared to the pristine K0.56MnO2, its reversible specific is increased from 104 to 135 mAh g-1. In addition, the Cu and Fe co-doping triples the capacity under high current densities, and contributes to long-term stability over 500 cycles with a capacity retention of 68 %. Such endeavor holds the potential to make potassium-ion batteries particularly competitive for application in sustainable, low-cost, and large-scale energy storage devices. In addition, the cathode is also extended for sodium storage. Facilitated by the interlayer K ions that protect the layered structure from collapsing and expand the diffusion pathway for sodium ions, the cathode shows a high reversible capacity of 144 mAh g-1, fast kinetics and a long lifespan over 1000 cycles. The findings offer a novel pathway for the development of high-performance and cost-effective sodium-ion batteries.

Four-Electron Redox Reaction in Prussian Blue Analogue Cathode Material for High-Performance Sodium-Ion Batteries

Four-Electron Redox Reaction in Prussian Blue Analogue Cathode Material for High-Performance Sodium-Ion Batteries