Sodium Storage Research Articles

Cu2-xSe@MXene (Ti3C2Tx) 2D layered heterostructure as an anode for high-performance sodium-ion batteries

With a notable focus on developing efficient sodium storage electrode materials, sodium-ion batteries (SIBs) have been identified as a promising contender in the pursuit of high-performing substitutes for lithium-ion batteries. Among varying sodium storage anode materials for SIBs, nonstoichiometric Cu2-xSe exhibits significant promise. This material stands out due to its ultrahigh electrical conductivity and theoretical sodium storage capacity. However, the practical implementation of Cu2-xSe-based anodes in SIBs is significantly impeded by their sluggish electrochemical reaction kinetics and severe pulverization during the repeated charge–discharge cycles. In the current research, we introduce a novel and straightforward methodology for the synthesis of a heterostructured SIBs anode material (Cu2-xSe@Ti3C2Tx), by coupling Cu2-xSe nanoparticles with two-dimensional (2D) layered MXene (Ti3C2Tx). The 2D layered Ti3C2Tx can provide abundant fast Na+ transport pathways, which effectively promote the ion transport kinetics in the composite anode. Moreover, the pulverization of Cu2-xSe can be effectively mitigated due to the interlamellar spatial confinement of the 2D layered MXene matrix. Consequently, the electrochemical performances of the Cu2-xSe-based anode are significantly improved. Concretely, the Cu2-xSe@Ti3C2Tx anodes demonstrate remarkable rate performance (248mAh g−1 at 10.0 A/g), along with commendable cycling stability, exhibiting a capacity retention of 92 % at 5.0 A/g after 750 cycles. A comprehensive assessment of the Cu2-xSe@Ti3C2Tx anode has been conducted by assembling a full SIB alongside a Na3V2(PO4)3 cathode. This comprehensive study underscores the significant potential of Cu2-xSe-based composite materials, positioning it as a promising candidate for future advancements in SIB technology.

Inhomogeneous Coordination in High‐entropy O3‐type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage

Inhomogeneous Coordination in High‐entropy O3‐type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage

Inhomogeneous Coordination in High-entropy O3-type Cathodes Enables Suppressed Slab Gliding and Durable Sodium Storage.

O3-type layered oxides are highly promising cathodes for sodium-ion batteries (SIBs), however they undergo complex phase transitions and exhibit high sensibility to air, leading to subpar cycling performance and commercial viability. In this work, we report a layered cathode material (NaNi0.29Cu0.1Mg0.05Li0.05Mn0.2Ti0.2Sn0.11O2) with a sate-of-the-art high-entropy compositional design. We unveil that such a configuration featuring inhomogeneous coordination environment of transition metal (TM) elements, can enable enhanced gliding energy (-0.38 vs -0.58 eV) of TMO2 slabs upon desodiation both theoretically and experimentally, which underlies the fundamental origin of the outstanding structural stability of HEO materials. As a consequence, the complex phase transitions (O3-O'3-P3-P'3-P3'-O3') of conventional O3-type cathode have been eliminated, and the as-obtained material demonstrates exceptional structural robustness and integrity with an ultra-long cycle life in a quasi-solid-state cell (maintaining 73.2% capacity after 1000 cycles at 2 C). Moreover, the material presents satisfactory air stability, with minimal structural and electrochemical degradation when directly exposed to the air. An Ah-scale pouch cell based on the cathode material is constructed, demonstrating a capacity retention of 83.6% after 500 cycles, signaling substantial promise for commercial applications.

Dual-Driven Ion/Electron Migration and Sodium Storage by In Situ Introduction of Copper Ions and a Carbon-Conductive Framework in a Tin-Based Sulfide Anode.

Tin sulfide (SnS) has emerged as a promising anode material for sodium ion batteries (SIBs) due to its high theoretical capacity and large interlayer spacing. However, several challenges, such as severe insufficient electrochemical reactivity, rapid capacity degradation, and poor rate performance, still hinder its application in SIBs. In this study, in situ introduction of copper ions and a carbon conductive framework to form SnS nanocrystals embedded in a Cu2SnS3 lamellar structure heterojunction composite (SnS/Cu2SnS3/RGO) with graphene as the supporting material is proposed to achieve dual-driven sodium ion/electron migration during the continuous electrochemical process. The designed structure facilitates the preferential electrochemical reduction of copper ions into copper nanocrystals during the discharge process and functions as a catalytically active center to promote multivalence tin sodiation reaction. Furthermore, during the charging process, the presence of copper nanocrystals also facilitates efficient desodiation of NaxSn and further activates to form higher valence state sulfides. As a result, the SnS/Cu2SnS3/RGO composite demonstrates high cycling stability with a high reversible capacity of 395 mAh g-1 at 5A g-1 after 500 cycles with a capacity retention of 85.6%. In addition, the assembled Na3V2(PO4)3∥SnS/Cu2SnS3/RGO sodium ion full cell achieves 93.7% capacity retention after 80 cycles at 0.5 A g-1.

Surface coating engineering of titanate anodes based on tannic acid-formaldehyde polymer chelating bismuth ions for advanced sodium-ion capacitors

As a battery-type anode material for sodium ion capacitors (SICs), titanate (H2Ti2O5·H2O, HTO) exhibits good rate capability due to its layered structure, easy to insert Na+ ions and low potential during sodium-ion storage. However, the structure is unstable due to the lattice distortion resulting from the irreversible embedment of Na+ in the process of sodium storage. So there is a significant mismatch between the dynamic reaction of the HTO anode and the capacitive cathode. Surface coating engineering is a useful strategy for stabilizing the HTO structure, which is critical for improving the kinetic response. In this work, a surface coating technique is designed to enhance the surface of HTO nanoarrays on titanium foil by using the oligomers of tannic acid formaldehyde polymer (TAF) chelated Bi3+ ions (Bi-TAF). As a binder-free anode, HTO coated with Bi-TAF (HTO@Bi-TAF) exhibits more excellent capacity (335.2 mA h g−1, 0.1 A g−1), rate capability (212.3 mA h g−1, 2.0 A g−1), and cycle stability (97 % capacity maintenance following 2000 cycles at 1.0 A g−1) than HTO and HTO coated with TAF (HTO@TAF). At the sweep rate of 1.0 mV s−1, the kinetic investigation reveals that the capacitance contribution of HTO@Bi-TAF is 86 %. The SICs exhibit a significant energy/power density (89.4 Wh kg−1/250 W kg−1). This work shows that the Bi-TAF polymer coating has a dual effect of rate capability improvement and structural protection on the prepared HTO. This results in a reasonable and effective surface coating strategy that provides outstanding rate capability and extended cycle performance of titanium-based anode materials for SICs.

Three-Dimensional Flexible SnO2@Hard Carbon@MoS2@Soft Carbon Fiber Film Anode toward Ultrafast and Stable Sodium Storage.

Developing flexible electrodes for the application in sodium-ion batteries (SIBs) has received great attention and has been still challenging due to their merits of additive-free, lightweight, and high energy density. In this work, a free-standing 3D flexible SIB anode with the composition of SnO2@hard carbon@MoS2@soft carbon is designed and successfully synthesized. This electrode combines the energy storage advantages and hybrid sodium storage mechanisms of each material, manifested in the enhanced flexibility, specific capacity, conductivity, rate, cycling performances, etc. Based on the synergistic effects, it exhibits much higher specific capacity than SnO2 carbon nanofibers, as well as more excellent cycling performance (250 mA h g-1 after 500 cycles at 1 A g-1) than MoS2 nanospheres (32 mA h g-1). In addition, relevant kinetic mechanisms are also expounded with the aid of theoretical calculation. This work provides a feasible and advantageous strategy for constructing high-performance and flexible energy storage electrodes based on hybrid mechanisms and synergistic effects.

Vertically Aligned MoS2 Nanosheets with Increased Interlayer Spacing on Hollow Polypyrrole Nanotubes for Enhanced Lithium and Sodium Storage Performance

Vertically Aligned MoS₂ Nanosheets with Increased Interlayer Spacing on Hollow Polypyrrole Nanotubes for Enhanced Lithium and Sodium Storage Performance

Unveiling the Microscopic Origin of Ultrahigh Initial Coulombic Efficiency of High-Entropy Metal-Organic Frameworks for Sodium Storage.

The initial irreversible capacity loss during the first charging process largely reduces the affordable energy and power density of sodium storage devices, and developing advanced materials is the efficient way to solve this problem, which is fraught with challenges. Herein, inspired by theoretical calculations and the high-entropy concept, a series of fewer layers of high-entropy metal-organic frameworks (FLHE-MOFs) are successfully fabricated, delivering an ultrahigh initial Coulombic efficiency (ICE) of 86.1% and excellent cycling performance, which is far more than that of the other electrode materials (generally <70%). Greatly, the storage behavior of high-, medium-, and low-entropy MOFs is clarified by theoretical calculations and in-/ex-situ characterization, revealing that Co and Fe species can provide substantial sodium storage sites and largely enhance the charge transfer rate, whereas high-entropy effect can enable structural reversibility. Sodium ion capacitors constructed with FLHE-MOFs as the anode can provide an ultrahigh energy density of 121.8 W h kg-1 (200 W kg-1) and an extremely long-term cycle lifespan. This work not only breaks the limitation of MOF materials with poor performance for sodium storage but also provides an effective strategy for the fabrication and application of high-performance MOF-based anode materials with high ICE, in which this idea may also be applied in other fields.

The Ether’s Chain Length Effect in Electrolyte for Hard carbon towards Efficient Sodium Storage at Low Temperature

The synergy between ether-based electrolytes (EBEs) and hard carbon (HC) in sodium-ion batteries (SIBs) enhances Coulombic efficiency, durability, and rate capability. Despite these advantages, the intricate relationship of how the molecular structure of ether solvents modifies electrolyte properties and, subsequently, sodium storage performance remains inadequately explored, especially for low-temperature applications, limiting the advancement of EBEs. Our study investigates ethylene glycol ether-based electrolytes with varying chain lengths to understand their influence on reaction kinetics and sodium storage. Notably, HC electrodes paired with NaPF6/ethylene glycol dimethyl ether exhibit superior performance, achieving 247.5 mAh g-1 after 2000 cycles at 1.0Ag-1. Even at -20 °C, these cells exhibit impressive endurance, retaining capacities of 257.5 mAh g-1 in half cells and 75.5 mAh g-1 in full cells at 0.1Ag-1 after 100 cycles, considering the entire mass of active material. Our thorough analysis indicates that the ether solvent with shorter chain length, distinguished by its low solvation-free energy and accelerated ionic kinetics, promotes rapid de-solvation and the formation of an inorganic-rich interface. Through this study, we illuminate the pivotal influence of solvent chain length on sodium storage in hard carbon, contributing to foundational insights towards the design of sophisticated electrolytes for SIBs.

Synergistic engineering of heteroatomic N-doping and PPy modification in flower-like vanadium sulfide anode enables stable sodium storage

Vanadium sulfide, an appealing anode candidate for sodium ion batteries (SIBs), still encounters considerable volume fluctuation and sluggish Na+ diffusion kinetics, which inevitably gives rise to unsatisfactory rate capability and severe capacity decay. Herein, we successfully designed and constructed an outstanding sodium-storage feature and exceedingly stable anode for SIBs in the form of three-dimensional flower-like architecture composing of phosphorus doped VS2 wrapped by conductive elastic polypyrrole (PPy) layer (i.e., P-VS2@PPy). Through leveraging the multifunctional synergistic effect of composition and structure, involving enhanced electronic conductivity, reduced volumetric fluctuation, accelerated charge/ion transfer efficiency, and remarkable surface-capacitive behaviors can guarantee significantly enhanced electrochemical sodium-storage ability of P-VS2@PPy composites. As a consequence,such P-VS2@PPy is endowed with desirable rate characteristic accompanied with long-period cyclic lifespan (436.7 mAh/g at 20.0 A/g after 2600 cycles), which far outperform contrastive P-VS2 and pure VS2 samples. Meticulous kinetic analysis combined with theoretical simulations conclude that phosphorus doping and PPy coating have substantial effects on strengthening ionic and electron diffusion kinetics. Thorough examination and analysis of the insertion and conversion mechanisms of P-VS2@PPy was conducted through ex situ tests, revealing superior reversible phase transformation between original VS2, intermediate NaVS2, and final Na2S/V. Additionally, a practical application test demonstrates that sodium ion full-cell and hybrid capacitor based on P-VS2@PPy anode showcase significant capacity contribution and outstanding specific energy output, capable of effortlessly lighting up a LED screen.

Effective stress dissipation by multi-dimensional architecture engineering for ultrafast and ultralong sodium storage

Stress accumulation is a key factor leading to sodium storage performance deterioration for NiSe2-based anodes. Therefore, inhibiting the concentrated local stress during the sodiataion/desodiation process is crucial for acquiring stable NiSe2-based materials for sodium-ion batteries (SIBs). Herein, a stress dissipation strategy driven by architecture engineering is proposed, which can achieve ultrafast and ultralong sodium storage properties. Different from the conventional sphere-like or rod-like architecture, the three-dimensional (3D) flower-like NiSe2@C composite is delicately designed and assembled with one-dimensional nanorods and carbon framework. More importantly, the fundamental mechanism of improved structure stability is unveiled by simulations and experimental results simultaneously. It demonstrates that this designed multidimensional flower-like architecture with dispersed nanorods can balance the structural mismatch, avoid concentrated local strain, and relax the internal stress, mainly induced by the unavoidable volume variation during the repeated conversion processes. Moreover, it can provide more Na+-storage sites and multi-directional migration pathways, leading to a fast Na+-migration channel with boosted reaction kinetic. As expected, it delivers superior rate performance (441 mA h g−1 at 5.0 A g−1) and long cycling stability (563 mA h g−1 at 1.0 A g−1 over 1000 cycles) for SIBs. This work provides useful insights for designing high-performance conversion-based anode materials for SIBs.

Coal-based graphene derived from different coal ranks: exceptional sodium storage performance in sodium-ion batteries.

Coal is a premium carbon material precursor as anode materials for sodium-ion batteries (SIBs). Additionally, developing anode materials with large capacity and rapid charging performance is essential for the advancement of SIBs. Consequently, in this work, coal-based reduced graphene oxide (CrGO) was prepared as an anode materials for SIBs by a modified Hummers-high temperature thermal reduction method with different ranks of coal (coal-based graphite, CG) as a precursor. The CG prepared from higher-rank coal exhibits a higher degree of graphitization, and its graphene layers are easier to exfoliate. The unique microstructure of CrGO provides stability during the sodium storage process and exhibits fast ion capacitive adsorption behavior, enhancing reaction kinetics. CrGO, with an initial reversible capacity of up to 331 mA h g-1 at a current density of 0.03 A g-1, achieves a specific capacity of 75 mA h g-1, even at a high current density of 10 A g-1. Notably, CrGO also maintains a good specific capacity of 123 mA h g-1 after 1000 cycles at a current density of 1 A g-1, with a capacity retention rate of 91.8%. This study highlights the potential for using coal-derived materials in the development of high-performance anode materials for SIBs, promoting the green and high-value utilization of coal.

Hollow porous Co0.85Se/MoSe2@MXene heterostructured anode for sodium-ion hybrid capacitors

Metal selenides have garnered significant attention as promising anode materials for sodium-ion hybrid capacitors (SIHCs), yet its sluggish reaction kinetics as the battery-type anodes pose a challenge for developing high power SIHCs when coupled with capacitor-type cathodes. To overcome this limitation, constructing heterostructured metal selenides anodes has emerged as a promising strategy to balance the reaction kinetics between two different types of electrodes. Herein, the hollow porous TA-Co0.85Se/MoSe2@MXene anode with multiple heterostructures for sodium storage has been engineered via facile double-etching and self-assembly approach. The well-tailored void space and abundant heterointerfaces may effectively mitigate volumetric changes and enhance structural stability. Density functional theory (DFT) calculations further reveal that the local multilevel built-in electric fields induced by the heterointerfaces can effectively accelerate charge transfer and reduce the migration energy barrier of Na+, thus boosting the reaction kinetics. The fabricated anode demonstrates superior long-term cycling performance with a reversible capacity of 414 mA h/g after 1000 cycles at 1 A/g and remarkable rate capability of 425 mA h/g at 5 A/g. Benefiting from the ingenious structure and excellent sodium storage performance, the as-built SIHCs achieves an impressive energy density of 193 W h kg−1 and high power output of 18 kW kg−1 with outstanding capacitance retention of 90 % at 2 A/g after 10,000 cycles. This study provides valuable insights into the rational design of multiple heterostructured anode materials with multilevel built-in electric fields for high-performance SIHCs.

High temperature induced abundant closed nanopores for hard carbon as high-performance sodium-ion batteries anodes

Hard carbon (HC) stands out as the preeminent anode material for sodium-ion batteries (SIBs) which are deployed in expansive energy storage infrastructures. Herein, the large enough graphene nanosheets interlayer and abundant nanopores with a diameter of ∼2.1 nm induced by adjusting the pyrolysis temperature in the thermosetting phenolic resin-derived hard carbon matrix to augment the performance of the sodium ion storage. The presence of sufficiently large carbon interlayers has been proven to provide active sites for reversible adsorption, enabling effective storage of sodium ions in the high-voltage slope region, while also promoting rapid Na+ transport. Meanwhile, forming abundant closed nanopores with larger sizes helps sodium ion storage in the low-voltage plateau region. In the optimized samples, the formation of sufficient long graphene nanosheets with a perfect crystal lattice, which further shrinks to form enclosed nanopores, effectively reduces defective sites and specific surface area. Additionally, the appropriate content of C-O and C=O functional groups contributes to an exceptional initial Coulombic efficiency (ICE) of up to 93%. Simultaneously, the optimized sample HC-1500 contributes to a remarkable plateau capacity of 294 mAh g-1 during the charging process (high reversible capacity of 403 mAh g-1 at 0.1 C). Moreover, based on the microstructure evolution and Na storage behavior of hard carbon, an “adsorption (27%) – filling (73%)” sodium storage mechanism that the sodium storage as a quasi-metallic sodium state is demonstrated. Consequently, this study will offer valuable insights for the development of hard carbon anodes tailored for high-energy practical SIBs, while also advancing the understanding of sodium storage mechanisms.

N/P/O co-doped porous carbon derived from agroindustry waste of peanut shell for sodium-ion storage

Porous bio‑carbon from agroindustry waste behaves one of the most promising anode materials for sodium-ion batteries (SIBs) because of its high sodium storage capacity, low cost, sustainability, and low charge/discharge voltage platform. Herein, we have developed a new N/P/O co-doped porous hard carbon derived from peanut shell (PSCNP) synthesized via KOH activation, hydrothermal doping combined with carbonization method, using chitosan as nitrogen source, phytic acid as phosphorus source, and peanut shell as carbon and oxygen source. Through seriously regulating the calcination temperature, the optimal PSCNP-800 carbonization at 800 °C can well combine the advantages of the natural rich porous microstructure of peanut shells, large graphite interlayer spacing (0.379 nm), and short diffusion distance for sodium-ion. As an advanced anode for SIBs, the PSCNP-800 delivered a reversible capacity of 248.8 mAh g−1 after 100 cycles at 25 mA g−1. This work could provide a possible idea for the preparation of N/P/O co-doped porous hard carbon from low-cost agroindustry waste as anodes for SIBs.

Ultralong K0.5Mn0.75PS3 Nanowires Tailored by K-Ion Scissors for Extraordinary Sodium-Ion Storage.

1Dlayered nanowires (NWs) are expected to be excellent electrode materials due to their efficient electron/ion transport and strain/stress relaxation. However, it is a great challenge to synthesize layered NWs by a top-down synthetic route. Herein, ultralong 1D layered K0.5Mn0.75PS3 NWs (length: >100µm; diameter: ≈300nm) are synthesized for the first time using "K-ion chemical scissors", whose excellent sodium storage performance originates from the bifunctional structural unit, ingeniously combining the alloying energy storage functional unit (P-P dimer) with the quasi-intercalated functional unit ([MnS3]4- framework). Stress-driven K-ion scissors achieve the rapid transformation of MnPS3 bulk to K0.5Mn0.75PS3 NWs with directed tailoring. Compared to MnPS3, the NWs exhibit enlarged interlayer spacing (9.32 Å), enhanced electronic conductivity (8.17×10-5 S m-1 vs 4.47×10-10 S m-1), and high ionic conductivity (2.14 mS cm-1). As expected, the NWs demonstrate high capacity (709 mAh g-1 at 0.5 A g-1) and excellent cycling performance (≈100% capacity retention after 2500 cycles at 10 A g-1), ranking among metal thiophosphates. A quasi-topological intercalation mechanism of the NWs is revealed through further characterizations. This work expands the top-down synthesis approach and offers innovative insights for the cost-effective and large-scale fabrication of NWs with outstanding electrochemical performance.

Innovative Synthesis and Sodium Storage Enhancement of Closed-Pore Hard Carbon for Sodium-Ion Batteries

Innovative Synthesis and Sodium Storage Enhancement of Closed-Pore Hard Carbon for Sodium-Ion Batteries

Spatial confinement strategy modulated by kinetic diameters of gaseous molecules for sodium storage

Constructing closed pore structures is essential for improving the plateau capacity of high-capacity hard carbon (HC) anodes for sodium-ion batteries. However, the absence of a straightforward and efficient strategy for constructing closed pores has hindered the advancement of high-capacity HC anodes. Here, we have developed a spatial confinement strategy for constructing closed pore structures using pyrolytic carbon (PC) as substrate and pyrolysis gas as the carbon source for chemical vapor deposition. The deposition of pyrolysis gas effectively tightens the pore entrance, thereby preventing electrolyte infiltration and transforming the open pores in the PC into highly efficient sites for sodium storage. The obtained optimal anodes demonstrate a remarkable specific capacity of 324.6 mAh g-1. More importantly, we calculate the kinetic diameters of the carbon source molecules from their iso-electron density surfaces and correlate them with the mechanism of closed pore formation, which will effectively guide the fabrication of closed pores for sodium storage.

Controllable preparation of bismuth nanosheets as anode for ultrafast sodium storage

Controllable preparation of bismuth nanosheets as anode for ultrafast sodium storage

Binder-free Cu-Sb-Sn-Zn-P alloys as high-efficiency anodes for sodium-ion batteries via double-pulse electrodeposition

Alloy anodes are widely recognized for their high theoretical specific capacity and have garnered significant attention among the anode materials studied for sodium-ion batteries. In this study, we synthesize Cu68.6Sb23.0Sn3.2Zn0.3P4.9 anodes using a double-pulse electrodeposition method. This binder-free alloy anode, comprising five high-capacity elements, significantly enhances specific capacity and improves cycling stability, while also demonstrating excellent sodium storage capability. Specifically, the Cu68.6Sb23.0Sn3.2Zn0.3P4.9 anode achieves an initial charge capacity of 368.8 mAh∙g−1 and remains highly stable over 100 cycles, with a capacity decay of only 0.1 %. In addition, the anode delivers 290.3 mAh∙g−1 even at a current density of 3200 mA∙g−1. The outstanding electrochemical performance can be attributed to improved electronic transfer efficiency due to the introduction of Cu into Cu68.6Sb23.0Sn3.2Zn0.3P4.9 alloy via reverse potential, as well as the porous structure that facilitates electrolyte penetration and sodium ion transport. The galvanostatic intermittent titration technique reveals a high sodium ion diffusion coefficient, further highlighting the potential of this alloy anode in advancing sodium-ion batteries.