Superior Sodium-ion Storage Research Articles

Dual graphitization to fabricate graphitic carbon aerogel for superior sodium-ion storage

Dual graphitization to fabricate graphitic carbon aerogel for superior sodium-ion storage

Joule heating for structure reconstruction of hard carbon with superior sodium ion storage performance

Hard carbon anode for sodium ion batteries still remains many challenges including insufficient cycling life and initial Coulombic efficiency (ICE), weak rate capability and poor compatibility in common ester electrolytes. Here, we propose a Joule heating post-treatment including multifield sintering method to reconstruct the structure of hard carbon from thick graphene layers to more disordered vortex layer structure composed of thin and curved graphite-like domains. The molecular dynamics simulation and differential charge density distribution demonstrate the crucial effect of electric field in strengthening the interaction between the polar molecule groups and the graphene layer, leading to the distortion and expanding of graphene layer. This is a universal and highly efficient strategy to modify various hard carbons within minutes. The optimized hard carbon anode exhibits exceptional rate capability and cycling stability with a high retention rate of 88.4% after 15,000 cycles at 10C in ether electrolyte. It also displays remarkably improved reversible capacity, initial Coulombic efficiency ICE of 89.5% and cycling stability in ester electrolyte. It is revealed by in-situ electrochemical impedance spectroscopy and atomic force microscopy that the spontaneous formation of a thin, stable and inorganic substance-rich solid electrolyte interface layer with significantly improved mechanical property is largely responsible for the outstanding sodium-ion transport kinetics and long lifespan.

Enhancing Ion Adsorption Capability through the Strong Interaction in Co9S8‐Carbon Hybrids Achieves Superior Sodium Ion Storage

AbstractMetal sulfides materials are promising anode candidates for Na+ storage due to their low cost and high theoretical capacity, while the complex phase transition and inevitable volume expansion during cycling restrain their practical applications. Herein, a simple one‐pot manipulation strategy was designed to construct Co9S8 nanoparticles strongly encapsulated in carbon nanotubes (Co9S8@C/NTs) composite structure with enhanced structural stability and reaction kinetics, resulting in greatly improved Na+ storage performance. Specifically, the obtained Co9S8@C/NTs could exhibit a remarkable capacity of 500 mAh g−1 at 0.5 A g−1 after 100 cycles and exceptional cycling stability over 600 cycles with 88 % capacity retention at 1 A g−1. Furthermore, the theoretical calculations combined with systematic characterizations confirm that the strong interaction between Co9S8 and the carbon matrix could greatly enhance the Na+ adsorption ability and facilitate the electron transfer dynamics for superior Na+ storage capability. More importantly, the full cell device can deliver an outstanding energy density of 144.32 Wh kg−1 and a decent cycling life with 82 % capacity retention of almost 100 cycles at 0.1 A g−1. This work could provide more valuable insights for designing advanced metal sulfide nanocomposites and demonstrate fascinating prospects for commercial application.

Facile construction of Cu2-xSe@C nanobelts as anode for superior sodium-ion storage

Transition metal selenides are considered promising electrochemical energy storage materials due to their excellent rate properties and high capacity based on multi-step conversion reactions. However, its practical applications are hampered by poor conductivity and large volume variation for Na+ storage, which resulting fast capacity decay. Herein, a facile metal-organic framework (MOF) derived method is explored to embed Cu2-xSe@C particles into a carbon nanobelts matrix. Such carbon encapsulated nanobelts' structural moderate integral electronic conductivity and maintained the structure from collapsing during Na+ insertion/extraction. Furthermore, the porous structure of these nanobelts endows enough void space to mitigate volume stress and provide more diffusion channels for Na+/electrons transporting. Due to the unique structure, these Cu2-xSe@C nanobelts achieved ultra-stable cycling performance (170.7 mAh/g at 1.0 A/g after 1000 cycles) and superior rate capability (94.6 mAh/g at 8 A/g) for sodium-ion batteries. The kinetic analysis reveals that these Cu2-xSe@C nanobelts with considerable pesoudecapactive contribution benefit the rapid sodiation/desodiation. This rational design strategy broadens an avenue for the development of metal selenide materials for energy storage devices.

Dual Activation for Tuning N, S Co-Doping in Porous Carbon Sheets Toward Superior Sodium Ion Storage.

Porous carbon has been widely focused to solve the problems of low coulombic efficiency (ICE) and low multiplication capacity of Sodium-ion batteries (SIBs) anodes. The superior energy storage properties of two-dimensional(2D)carbon nanosheets can be realized by modulating the structure, but be limited by the carbon sources, making it challenging to obtain 2D structures with large surface area. In this work, a new method for forming carbon materials with high N/S doping content based on combustion activation using the dual activation effect of K2SO4/KNO3 is proposed. The synthesized carbon material as an anode for SIBs has a high reversible capacity of 344.44mAhg-1 at 0.05Ag-1. Even at the current density of 5Ag-1, the capacity remained at 143.08mAhg-1. And the ICE of sodium-ion in ether electrolytes is ≈2.5 times higher than that in ester electrolytes. The sodium storage mechanism of ether/ester-based electrolytes is further explored through ex-situ characterizations. The disparity in electrochemical performance can be ascribed to the discrepancy in kinetics, wherein ether-based electrolytes exhibit a higher rate of Na+ storage and shedding compared to ester-based electrolytes. This work suggests an effective way to develop doubly doped carbon anode materials for SIBs.

Room-temperature synthesis of nonstoichiometric copper sulfide (Cu2−xS) for sodium ion storage

Nonstoichiometric copper sulfide (Cu2−xS), which was surprisingly prepared by using excess sulfide ions to react with copper ions in aqueous solution, exhibited superior sodium ion storage performance to CuS.

Vacancy‐Ordered Superstructure‐Induced Delocalized States Enable Superior Sodium Ion Storage

AbstractTransition metal sulfides (TMSs) are perceived as competitive candidate anodes for sodium‐ion batteries (SIBs) on account of their high capacity and admirable reversibility. However, a majority of TMSs suffer from huge volume expansion and poor kinetics so they cannot achieve durable and fast Na+ storage. Herein, a cation vacancy‐ordered Cr2/3S is fabricated by extracting quantitative Cr atoms from nickel arsenide type CrS via sulfur “atomic pump,” that is, sulfur and particular sit Cr atoms are bonded to extend a new structure. The ordered vacancies not only construct a loosely‐packed crystal structure but also induce delocalized electron states of Cr atoms, hence effectively accelerating Na+ diffusion and releasing volume strain to enable high‐rate and longevous SIBs. The new Cr2/3S anode presents a high reversible capacity of 544 mAh g−1 after 100 cycles at 1 A g−1 and excellent high‐rate performance of ≈100% capacity retention after 7000 cycles at 20 A g−1. Subsequent in situ and ex situ characterizations reveal the Na+ storage mechanism of Cr2/3S. The proposed cation exaction strategy through an innovative sulfur “atomic pump” can be an efficient way to achieve loosely‐packed structure material for large‐capacity and fast‐kinetics anodes.

Hierarchical CoSe2/TiN/nitrogen-doped carbon nanofibers wrapped with carbon nanotubes: A binder-free anode for enhanced sodium-ion storage

Transition metal chalcogenide anodes have attracted significant attention for sodium-ion batteries (SIBs) owing to their relatively high theoretical capacity. However, the inherently poor electronic conductivity and rate performance hinder their practical application. In this study, hierarchically structured CoSe2/TiN/nitrogen-doped carbon nanofibers wrapped with in-situ grown carbon nanotubes (CNTs) on the surface (denoted as CoSe2@N-TCF/CNTs) are designed and fabricated as binder-free anodes for SIBs. The rational design can effectively avoid the agglomeration of CoSe2 nanoparticles, improve the conductivity of the composite materials, provide enough space for electrolyte penetration and volume expansion during the cycling process and shorten the transmission paths of electrons and Na+. With these structural and compositional advantages, the as-obtained hierarchical CoSe2@N-TCF/CNTs deliver a high reversible capacity of 401.2 mAh g−1 after 1000 cycles at 0.2 A g−1 and maintained at 353.7 mAh g−1 even at a high current density of 2 A g−1 when directly used as a binder-free anode for SIBs. The superior sodium-ion storage performance can be attributed to the decreased charge transfer resistance, improved Na+ diffusion rate and the pseudocapacitance behavior, as is evidenced by kinetics analysis.

Constructing heterointerface of Bi/Bi2S3 with built-in electric field realizes superior sodium-ion storage capability

Bismuth sulfide (Bi2S3) is a dominant anode material for sodium-ion batteries due to its high theoretical capacity. However, extreme volume fluctuations as well as low electrical conductivity and reaction kinetics still limit its practical applications. Herein, we construct an abundant heterointerface of Bi/Bi2S3 by engineering the structure of Bi nanoparticles embedded on Bi2S3 nanorods (denoted as Bi–Bi2S3 NRs) to effectively solve the abovementioned obstacles. Theoretical and systematic characterization results reveal that the constructed heterointerface of Bi/Bi2S3 has a built-in electric field, significantly boosts the electrical conductivity, enhances the Na+ diffusion kinetics, and buffers the volume variation. With this modification, it can deliver long cycling life, with an ultra-high capacity of 500 mAh g−1 over 500 cycles at 1 ​A ​g−1, and outstanding rate capability, with a capacity of 456 mAh g−1 even at 15 ​A ​g−1. Moreover, a full cell can achieve a high energy density of 180 ​Wh kg−1 at a power density of 40 ​W ​kg−1. Our research opens up a fresh path for improving the dynamics and structural stability of metal sulfide-based electrode materials for SIBs.

Growing curly graphene layer boosts hard carbon with superior sodium-ion storage

Growing curly graphene layer boosts hard carbon with superior sodium-ion storage

Phase separation-hydrogen etching-derived Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies boosting superior sodium-ion storage kinetics

Understanding the crystal phase evolution of bimetallic oxide anodes is the main concern to profoundly reveal the conversion reaction kinetics and sodium-ion storage mechanisms. Herein, an integrated self-supporting anode of the Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies (Ov-BMO-Cu) are in-situ generated by phase separation and hydrogen etching using nanoporous Cu-Mn alloy as self-sacrificial templates. On this basis, we have elucidated the relationship between the phase evolution, oxygen vacancies and sodium-ion storage mechanisms, further demonstrating the evolution of oxygen vacancies and the inhibition effect of manganese oxides as an “anchor” on grain aggregation of copper oxides. The kinetic analyses confirm that the expanded lattice space and increased oxygen vacancies of cycled Ov-BMO-Cu synergistically guarantee effective sodium-ion diffusion and storage mechanisms. Therefore, the Ov-BMO-Cu electrode exhibits higher reversible capacities of 4.04 mA h cm−2 at 0.2 mA cm−2 after 100 cycles and 2.20 mA h cm−2 at 1.0 mA cm−2 after 500 cycles. Besides, the pre-sodiated Ov-BMO-Cu anode delivers a considerable reversible capacity of 0.79 mA h cm−2 at 1.0 mA cm−2 after 60 cycles in full cells with Na3V2(PO4)3 cathode, confirming its outstanding practicality. Thus, this work is expected to provide enlightenment for designing high-capacity bimetallic oxide anodes.

Sub-nanometric amorphous V–O clusters without grain boundaries bonded in yolk-shell carbon nanospheres for superior sodium-ion storage

The energy density of sodium-ion batteries (SIBs) reported so far is still low, which weakens their competitiveness in practical applications. Cluster engineering and sub-nanometric design are effective strategies for rapid and efficient storage of alkaline ions. Herein, a durable yolk-shell architecture is developed via a facile self-polymerization and calcination process, in which the sub-nanometric amorphous vanadium-oxide (V–O) clusters are bonded in N-doped carbon nanospheres (A-VOxC/N–C). As a SIB anode, the composite delivers a large reversible capacity (491.6 mAh g−1 at 0.05 A g−1), high-rate capability and ultra-long cyclic stability (246.4 mAh g−1 with 96.6% capacity retention after 30000 cycles at 20.0 A g−1). In addition, the full cell also exhibits great potential for practical applications. The detailed structural characterizations and density functional theory (DFT) calculations suggest that the amorphous clusters without grain boundaries are crucial for the creation of abundant active sites and highly isotropic channels, as well as the reduction of Na-intercalation stress. The yolk-shell N–C has the structural advantages of flexible cavity, strong bonding force and large spatial constraint, which can effectively alleviate volume changes and strengthen structural stability. In view of these, this study can provide guidance for the design of sub-nanometric clusters and their potential applications in alkaline ion batteries.

CoSe2 nanoparticles anchored on dual 1D carbon nanotubes/N-doped carbon nanofibers as high-performance anodes for sodium-ion storage.

Transition metal chalcogenides (TMCs) have been widely explored and utilized in sodium-ion battery (SIB) anodes owing to their unique advantages, such as high theoretical specific capacity and low cost. However, their inherent defects, such as low electronic conductivity and severe volume expansion, seriously limit the further development of TMC-based anodes. Here, a novel composite material of CoSe2 nanoparticles (NPs) encapsulated in a dual one-dimensional (1D) carbon composite structure (CoSe2@CNTs/N-CNFs) was designed deliberately. Carbon nanotubes (CNTs) were grown in situ on the surface of carbon nanofibers (CNFs) with eco-friendly ethanol as the carbon source, while electrospun polyacrylonitrile (PAN) fibers were pyrolyzed to form nitrogen-doped nanofibers. It is noted that the wrapping with the composite carbon structure greatly improved the stability of CoSe2 NPs and solved its inherent defects as an anode material. When assembled into a half-cell, the CoSe2@CNTs/N-CNFs electrode exhibited outstanding sodium storage performance with a reversible specific capacity of 442 mA h g-1 after 100 cycles at 0.1 A g-1, as well as excellent rate performance, and the discharge specific capacity still reached 265 mA h g-1 even after 2000 cycles at a high current density of 5 A g-1. This study shows a new way to build a novel carbon substrate and TMC composite sodium storage material with low cost.

In situ Cu doping of ultralarge CoSe nanosheets with accelerated electronic migration for superior sodium-ion storage.

The progress of sodium-ion batteries is currently confronted with a noteworthy obstacle, specifically the paucity of electrode materials that can store large quantities of Na+ in a reversible fashion while maintaining competitiveness. Herein, ultrafast and long-life sodium storage of metal selenides is rationally demonstrated by employing micron-sized nanosheets (Cu-CoSe@NC) through electron accumulation engineering. The nanosheet structure proves to be effective in reducing the transport distance of sodium ions. Furthermore, the addition of Cu ions enhances the electron conductivity of CoSe and accelerates charge delocalization. As an anode for sodium-ion batteries, Cu-CoSe@NC exhibits a noticeably enhanced specific capacity of 527.2 mA h g-1 at 1.0 A g-1 after 100 cycles. Additionally, Cu-CoSe@NC maintains a capacity of 428.5 mA h g-1 at 5.0 A g-1 after 800 cycles. It is possible to create sodium-ion full batteries with a high energy density of 101.1 W h kg-1. The superior sodium storage performance of Cu-CoSe@NC is attributed to the high pseudo-capacitance and diffusion control mechanisms, as evidenced by theoretical calculations and ex situ measurements.

Phase transformation controlled Co1−xS-CoS2 heterostructures embedded in S-doped carbon nanofibers for superior Sodium-Ion storage

Cobalt-based sulfides are considered as a promising anode material for sodium-ion batteries (SIBs) due to its various chemical formulations and high theoretical capacity. However, slow kinetics and structural instability lead to unsatisfactory electrochemical performance. Herein, ultrafine particles with Co1−xS-CoS2 heterostructures precisely controlled by phase transformation has been integrated with the encapsulation with S-doped carbon nanofiber through the one-stone-two-birds strategy. Due to the abundant heterointerfaces, unique yolk-shell structure and increased carbon interlayer spacing in Co1−xS-CoS2/carbon nanofibers (Co1−xS-CoS2/CNF), the reaction kinetics and the diffusion rate of Na+ have been significantly improved. As expected, the as-prepared Co1−xS-CoS2/CNF anode exhibits extraordinary rate performance (495.3 mAh/g at 10 A/g) and cycling stability (380.1 mAh/g at 5 A/g after 5,000 cycles), outperforming most reported TMS materials. A sodium-ion full cell with a Co1−xS-CoS2/CNF anode and Na3V2(PO4)3 cathode also show excellent electrochemical performance. The electrochemical reaction mechanism of Co1−xS-CoS2/CNF is revealed by ex-situ XRD and ex-situ HRTEM. Hence, it is hoped that our work can provide constructive ideas for the design of electronic or morphological structures for building high-performance energy storage materials.

Pre-strain accommodation enabled multi-dimensionally and hierarchically elastomeric MoSe2/MXene and AC/MXene electrodes for stretchable sodium ion capacitors

Stretchable supercapacitors with simultaneously high energy/power densities and long life can enrich integrated power options for ever-increasing wearable electronics. However, supercapacitors with high electrochemical performances while maintaining high stretchability are still challenging. Herein, we report stretchable sodium ion capacitors (S-SICs) based on multi-dimensionally and hierarchically elastomeric composite electrodes, and stretchable high voltage gel polymer electrolyte (3.0 V). The elastomeric composite electrode is constructed by stretchable 3D electrospun polyurethane (PU) fibrous mat and conductive 1D Ag nanowire network. 2D MoSe2/MXene and 3D AC/MXene as anodic and cathodic materials are embedded in this conductive and stretchable mat. This hierarchical structure enables multi-dimensional conductive connections under tensile condition. The pre-strain treatment on PU fibrous mat further increases the relatively stretching distance before losing conductive connection among hierarchical components. The electrodes exhibit superior sodium ion storage performances (420 mAh g−1 at 5 A g−1), as well as good stretchability and stability (95% after 1000 cycles at 2 A g−1). Based on this, the S-SICs with high operating voltage demonstrate high energy/power densities (max. 5.44 mWh cm−3, 493.55 mW cm−3) and good stretchability. This prototypical exhibition of S-SICs indicates a promising design direction of stretchable supercapacitors with high electrochemical performances and tolerance of stretchability.

Regulation of surface oxygen functional groups and pore structure of bamboo-derived hard carbon for enhanced sodium storage performance

Hard carbon materials with long low-voltage plateau have been used as the anode materials for sodium ion batteries which are considered to be one of the most potential large-scale energy storage systems. Herein, carbonyl groups and closed micropores are introduced into bamboo-derived hard carbon materials simultaneously to enhance the sodium ion storage performance. The carbonyl groups are demonstrated to enhance the reversible Na adsorption in the sloping region and closed micropores are beneficial to sodium ion storage in the low-voltage plateau region. Moreover, the introducing carbonyl groups improve the reversible sloping capacity not at the expense of increasing specific surface area and deteriorating the initial Coulombic efficiency. The hard carbon carbonized at 1300 °C delivers a high reversible specific capacity of 348.5 mAh g−1 at a current density of 30 mA g−1 with a charge/discharge Coulombic efficiency of 84.1 %, and keeps a specific capacity of 295.9 mAh g−1 with a capacity retention of 91.6 % at a current density of 300 mA g−1 after 500 cycles. This work provides a novel strategy to precisely regulate the microstructure for biomass-derived hard carbon for superior sodium ion storage performance.

Highly stable Ti3C2Tx MXene-based sandwich-like structure via interfacial self-assembly of nitrogen-rich polymer network for superior sodium-ion storage performance

To improve sluggish reaction kinetics and solve the severe self-stacking of MXene-based anodes for sodium ion batteries (SIBs), a novel highly stable sandwich-like structure with tunable interspace supported by dense N-rich polymer hydrogen-bonding network is synthesized for improving the pseudo-capacitance of Ti3C2Tx MXene. The interconnected MXene-based sandwich structure can establish the stable conductive framework, abundant active sites and tunable interspace that provide channels for rapid Na+ storage. Besides, the dense polymer hydrogen-bonding network can effectively prevent interlayer restacking for ultra-stable Na+ storage. After modification, the N contents of Ti3C2Tx MXene are increased to 21.63 at %. N-rich polymer network not only provides extra active sites for pseudo-capacitance Na+ storage, but also accelerates Na+ transport and charge transfer. As the anode for half-cell of SIBs, it shows excellent cycling performance of 148.4 mAh g−1 after 3000 cycles at 500 mA g−1 with capacity retention of 102.4 % and 123.4 mAh g−1 after 5000 cycles at 1000 mA g−1. The performance of full-cell based on the optimized composite anode and Na3V2(PO4)3 (NVP) cathode is superior to other MXene-based full-cell of SIBs. The novel sandwich-like structure delivers a perspective for enhancing the stability and achieving fast Na+ diffusion of layer structure by polymer hydrogen-bonding network.

Embedding amorphous MoSx within hierarchical porous carbon by facile one-pot synthesis for superior sodium ion storage

The design of anode materials with a high specific capacity, high cyclic stability, and superior rate performance is required for the practical applications of sodium-ion batteries (SIBs). In this regard, we introduce in this work a facile, low-cost and scalable method for the synthesis of nanocomposites of amorphous molybdenum sulfide (a-MoSx) and hierarchical porous carbon and have systematically investigated their performance for sodium ion storage. In the synthesis, ammonium molybdate tetrahydrate and thioacetamide are used as molybdenum and sulfur sources, respectively, with abundant corn starch as the carbon source and KOH as an activation agent. A simple pyrolysis of their mixtures leads to the formation of nanocomposites with a-MoSx embedded within a hierarchical porous carbon (MoSx@HPC), which are featured with a high surface area of up to 518.4 m2 g−1 and hierarchical pores ranging from micropores to macropores. It has also been shown that the annealing of MoSx@HPC results in the formation of crystalline MoS2 nanosheets anchored in the hierarchical porous carbon matrix (MoS2@HPC). The as-prepared nanocomposite MoSx@HPC1 at an optimum carbon content of 32 wt% delivers a high specific sodium storage capacity of 599 mAh g−1 at 0.2 A g−1 and a high-rate performance with a retained capacity of 289 mAh g−1 at 5 A g−1. A comparison of the electrochemical performances of MoSx@HPC and MoS2@HPC demonstrates the superior specific capacity, rate performance, and charge transfer kinetics of the former, highlighting the unique advantageous role of amorphous MoSx relative to crystalline MoS2.

A facile Ball-Milling preparation strategy of Nitrogen-Doped carbon coated Na4Fe3(PO4)2P2O7 Nano-Flakes with superior sodium ion storage performance

Na4Fe3(PO4)2P2O7 (NFPP) is expected to be a promising cathode material for sodium ion batteries (SIBs) applied to large-scale energy storage systems owing to its abundant resource and low cost of the raw materials. However, the currently reported methods for preparing NFPP either cannot be applied to mass-production on a large scale because of their high energy consumption, or result in the production of NFPP materials that have poor electrochemical performance. Herein, we prepared a hierarchical nitrogen-carbon-coated NFPP nanoflake by a facile and easily scalable solid-phase ball milling method, in which oleic acid as the surfactant and carbon source. The formation mechanism of this hierarchical open structure constructed by uniform nano-flakes was investigated by a heating-rate controlled experiment, which indicated that heating rates play an important role in morphology and structure of the final products. When used as a cathode material, the present NFPP nano-flakes composites are able to operate in a wide temperature range (−20 ∼ 50 °C) and, can provide specific capacity of 129 mAh/g at 0.1C, with excellent cycling stability (81 % capacity retention at 10C after 1500 cycles) at 25 °C. Furthermore, the NFPP cathode is coupled with the MoS2 anode (MoS2/rGO) to assemble the sodium ion full battery, it exhibits outstanding rate/cycling performances. The present work provides a method of preparing NFPP electrode materials with good performance for s SIBs, which can be easily amplified production.