Performance Sodium-ion Batteries Research Articles

Construction of Three-Dimensional Hierarchical CoSe2 Microflowers Assembled by Thin Nanosheets for High-Performance Sodium-Ion Batteries

Transition metal selenides are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, they suffer from large volume change, serious polyselenide dissolution and sluggish reaction kinetics during charge/discharge process, resulting in poor cycling stability and low rate performance for SIBs, which further restrict their widespread application. Here, we developed carbon-free three-dimensional (3D) hierarchical microflower-shaped CoSe2 with a diameter size of approximately 2[Formula: see text][Formula: see text]m, composed of nanosheets through a one-step solvothermal method. The thin nanosheets are conducive to shortening the Na[Formula: see text] diffusion channels and relieving the volume expansion, and the 3D hierarchical microflower architecture could effectively prevent the agglomeration of nanosheets; accordingly, the resulting CoSe2 microflowers deliver a high specific capacity of 451.94[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] even at 0.5[Formula: see text]A[Formula: see text]g[Formula: see text] after 100 cycles, compared with CoSe2 nanoparticles. This work offers an approach for designing metal selenides with high capacities and rate capability for SIBs.

Influence of Formation Temperature on Cycling Stability of Sodium-Ion Cells: A Case Study of Na3V2(PO4)2F3|HC Cells

Sodium-ion batteries are cheaper and attractive alternatives to lithium-ion batteries, particularly for low-energy and high-power applications. In this regard, a targeted cell design is essential to achieve optimal cycling performances and reduced cell impedance. While optimized electrode and electrolyte formulations are important, the formation protocol -initial cycles that establish the electrode-electrolyte interphase- significantly impacts cell impedance and interphase stability. In this study, we investigate the influence of formation temperature on the nature of interphases formed in Na3V2(PO4)2F3 (NVPF)|hard carbon (HC) cells. Our findings reveal that the interphase’s nature and chemical composition evolve with the formation temperature. Moreover, cell temperature affects interphase dissolution and reformation, suggesting the potential benefits of employing mixed high and low temperatures during formation cycles to achieve desired interphase properties. A formation protocol coupling cycling stages at different temperatures (55 °C–25 °C–0 °C) exhibits an edge over with respect to low impedance, slightly higher reversible capacity and long cycling stability compared to the cells formed solely at 55 °C. The results presented underscore the necessity of exploring formation protocols including not only high temperatures but also colder temperatures, like 0 °C and below. This approach is pivotal for advancing the understanding of interphase dynamics and optimizing sodium-ion battery performance.

NiS2/CoS2@NC@C nanocubes derived from prussian blue analogues as an advanced anode with extraordinary long-cycle performance for sodium ion batteries

Transition metal sulfides (TMSs) are regarded as one of the ideal anodes for sodium ion batteries (SIBs) owing to their high theoretical capacity and strong electrochemical activity; nonetheless, it still faces challenges such as large volume variation and low conductivity during chemical reactions for applications. Herein, the nanocubes of carbon-encapsulated NiS2/CoS2 embedded porous nitrogen-doped carbon matrixes (NiS2/CoS2@NC@C) are synthesized as a high-performance anode by in-situ carbonizing and subsequently sulphurating the resorcinol-formaldehyde (RF)-coated Ni-Co-based Prussian blue analogues (PBAs). The RF-derived carbon shell acts as a rigid skeleton to effectively relieve the bulk stress during charging and discharging for ensuring the structure integrity, while the porous nitrogen-doped carbon matrix improves the electronic conductivity, presents rich channels for ion/electron transfer and inhibits the agglomeration of active material during chemical reaction. In addition, the lattice distortion at the heterogeneous interface of the NiS2/CoS2 allows the redistribution of electrons, promoting the chemical reaction kinetics. Consequently, the NiS2/CoS2@NC@C nanocubes exhibit excellent electrochemical properties: a high discharge capacity of 489.9 mA h g−1 after 170 cycles at 1.0 A g−1 (920.6/807.9 mA h g−1 for the initial discharge/charge capacity with the initial coulomb efficiency of 87.7%) and a discharge capacity of 349.7 mA h g−1 with the CE close to 100.0% at 5.0 A g−1 even after 2000 cycles. This study proposes a viable approach for the effective construction of advanced anodes with unique micromorphology and chemical composition based on bimetallic PBAs for SIBs.

Double-substituted Na3SbS4 Glass–Ceramic electrolyte with excellent performance for sodium-ion batteries

Here, we report the SiS2–NaBr double-doped sulfide superionic conductor Na3.02Si0.1Sb0.9S3.92Br0.08. The dual-doping effect of SiS2 and NaBr in the Na3SbS4 electrolyte was investigated by mechanical ball milling and high-temperature heat treatment. The improved glass–ceramic Na3.02Si0.1Sb0.9S3.92Br0.08 solid electrolyte obtained a high ionic conductivity of 2.26 × 10−3 S/cm and a low activation energy of 0.077 eV (0.25 eV for Na3SbS4) at room temperature. Moreover, the electrochemical property test was characterized by a higher critical current density of 1.228 mA/cm2 (0.585 mA/cm2 for Na3SbS4) and stable cycling at 0.1 mA cm−2 current densities exceeding 120 h (50.33 h for Na3SbS4). Some Si atoms occupying the Sb position greatly contributed to the formation of the Na3SbS4 high-ionic conductive phase. The introduction of an appropriate amount of halogen improved the compactness of the sample and nearly suppressed the majority of H2S release from the original electrolyte. The substitution effect and the ion conduction structure were analyzed in detail.

Influence of Hard Carbon Materials Structure on the Performance of Sodium-Ion Batteries

Influence of Hard Carbon Materials Structure on the Performance of Sodium-Ion Batteries

Suppressing the P2‐O2 phase transition and Na+/vacancy ordering in Na0.67Ni0.33Mn0.67O2 by a delicate multicomponent modulation strategy

AbstractP2‐type Na0.67Ni0.33Mn0.67O2 is a promising cathode for sodium‐ion batteries with features of high specific capacity and air resistance, whereas its cycling stability and rate performance are dissatisfactory suffering from the disastrous P2‐O2 phase transition and Na+/vacancy ordering during sodium‐ion de/intercalation, which makes it an obstruction for future practical applications. Herein, a delicate multicomponent modulation strategy is proposed to tackle these two issues simultaneously, in which Li+ and Ti4+ are introduced to replace the Ni2+ and Mn4+, respectively, whereas the Na+ content is also designed according to the principle of charge balance. Consequently, the designed cathode (Na0.72Ni0.28Li0.05Mn0.57Ti0.10O2) can deliver an enchanting cycling stability of 80% at 1 C after 200 cycles along with a considerable rate performance of 82.7 mAh g−1 at 5 C. In situ X‐ray diffraction measurement demonstrates the destructive P2‐O2 phase transition is suppressed and converted into a P2‐Z phase transition with superior reversibility as well as smooth charge/discharge curves with better Na+/vacancy disordering. In addition, the full cell matched with hard carbon anode delivers an excellent energy density of 263.4 Wh kg−1 at 37.3 W kg−1, exhibiting great practicality. Our work presents a mean to rationally design the component of layered oxide cathode and achieve fabulous performance for sodium ion batteries.

Design and Synthesis Strategy of MXenes-Based Anode Materials for Sodium-Ion Batteries and Progress of First-Principles Research.

MXenes-based materials are considered to be one of the most promising electrode materials in the field of sodium-ion batteries due to their excellent flexibility, high conductivity and tuneable surface functional groups. However, MXenes often have severe self-agglomeration, low capacity and unsatisfactory durability, which affects their practical value. The design and synthesis of advanced heterostructures with advanced chemical structures and excellent electrochemical performance for sodium-ion batteries have been widely studied and developed in the field of energy storage devices. In this review, the design and synthesis strategies of MXenes-based sodium-ion battery anode materials and the influence of various synthesis strategies on the structure and properties of MXenes-based materials are comprehensively summarized. Then, the first-principles research progress of MXenes-based sodium-ion battery anode materials is summarized, and the relationship between the storage mechanism and structure of sodium-ion batteries and the electrochemical performance is revealed. Finally, the key challenges and future research directions of the current design and synthesis strategies and first principles of these MXenes-based sodium-ion battery anode materials are introduced.

Flash Pyrolyzed Coal Char for Sodium Ion Battery Anodes

Present day lithium ion batteries face challenges regarding the sustainability, cost, and natural resource availability of their components. Sodium has been shown to be a complementary energy storage material, providing usable volumetric energy density. In designing sodium ion batteries (SIBs), hard carbon is used at the anode in place of graphite, due to the necessary micro domain structure needed to store sodium ions. Coal char is a low cost material and viable source of hard carbon. The use of coal char in SIBs also provides a high value, secondary use pathway for the abundant char component of coal.In this work, flash pyrolyzation is explored as a novel approach for coal char synthesis for SIB anodes using a Utah local bituminous coal. During flash pyrolyzation, char is heated in a drop-tube furnace at 1000 oC/s vs. the traditional slow pyrolyzation approach where char is heated at 20 oC/min. Flash pyrolyzed (FP) char has a surface structure that is vastly different in comparison to the slow pyrolyzed (SP) char (Figure 1.), larger d-spacing (FP d-spacing = 0.379 nm, SP d-spacing = 0.364 nm) and a smaller closed micropore diameter (FP micropore = 1.52 nm, SP micropore = 1.91 nm), as concluded from X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) analysis, respectively.The SIB performance of FP char vs. SP char is tested and compared in ether-based and ester-based electrolytes. FP char performs better as a SIB anode than SP char in both electrolytes. Additionally, both char anodes achieve higher reversible capacity and better initial coulombic efficiencies (ICE) in an ether-based vs. ester-based electrolyte. When FP char is combined with an ether-based electrolyte, a 10th cycle reversible capacity of 109.4 mAh/g is achieved, whereas a SP char with an ester-based electrolyte cell has a 10th cycle reversible capacity of 72.5 mAh/g, when both cells are cycled at 50 mA/g (sodium metal half-cells). FP ether cells also perform with an initial coulombic efficiency (ICE) of 64%, but SP ester cells only show an ICE value of 52%. The enhanced electrochemical performance of the FP cells is attributed to differences in surface/bulk structure due to the high heating rate. The improvement in char anode performance in ether-based cells is likely due to the formation of a thinner solid-electrolyte interphase and/or improved sodiation due to an ether-based electrolyte. Figure 1

A multiphase coupling strategy to structurally stable manganese-based oxides cathode for high electrochemical performance sodium ion batteries

Manganese (Mn) based oxides attract extensive attention as cathode materials for sodium (Na) ion batteries (SIBs) due to their high theoretical capacity and low cost. However, the Jahn-Teller distortion caused by the Mn (III) center and the phase transition of P2-O2 at high voltage (>4.0 V) limits its practical applications. In this work, a multiphase coupling scheme involving Na0.7MnO2.05 (P2), Na0.44MnO2 (T), and Na0.91MnO2 (Z) is presented to develop improved and available Mn based oxides cathode for superior electrochemical performance SIBs via solid state method. It is found that the optimal coupling at the molecular and atomic levels can be achieved by adjusting the regulation of morphology and grain size of the multiphase, which possesses larger interlayer spacing and fewer Mn3+ ions to suppress the Jahn-Teller lattice distortion of Mn3+ as well as the phase transition of P2-O2 at high voltage (>4.0 V). As a result, the as-prepared cathode delivers a high discharge specific capacity of 183.28 mA h g−1 at a rate of 0.5 C with a high-capacity retention of 77.2% after 100 cycles. Moreover, it also shows the fastest Na+ diffusion ability and kinetics properties, which is revealed by refined analysis of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves. This study presents a straightforward and scalable approach for developing novel cathode materials based on Mn oxides with excellent performance in sodium-ion batteries (SIBs).

K-doped P2-Na0.67−xKxNi0.33−yMn0.67CuyO2 cathode material with enhanced cycle performance for sodium-ion batteries

As one of the typical compositions for Ni/Mn-based layered oxides, P2-Na0.67Ni0.33Mn0.67O2 is widely studied due to its high capacity and wide voltage. However, its electrochemical performance requires further improvement for practical application as a cathode material of sodium-ion batteries. In this study, we successfully synthesized a series of K-doped P2-Na0.67−xKxNi0.33−yMn0.67CuyO2 (x = 0, 0.01, 0.06, 0.10, 0 < y < 0.16) cathode materials using a convenient sol-gel method. During the initial discharge, the NKNMC0.06 electrode delivers a high capacity of 120.3 mAh g−1 at 100 mA g−1 when charged and discharged from 1.5 to 4.2 V. And the electrode retains a specific capacity of 101.6 mAh g−1, with a good capacity retention rate of 84.5 % after 100 cycles. The enhanced cycle performance can be attributed to the appropriate amount of K+ ions occupying the Na+ sites and providing support between the transition metal layers, which stabilizes the crystal structure and improves cycle stability of the electrode. Moreover, larger-sized K+ ions expand the Na+ diffusion channel, facilitating Na+ diffusion. Furthermore, the pouch cell of NKNMC0.06 delivers a capacity of 0.28 Ah during the first discharge and maintains a capacity retention rate of 78.2 % after 100 cycles.

The Emeraldine salt PANI/SnO2 nanocomposite anode materials for sodium-ion batteries with enhanced initial coulombic efficiency

Tin oxide is promising candidate as an anode material for sodium-ion batteries. High volume change and the low electrical conductivity of SnO2 material during sodiation and de-sodiation affect negatively the electrochemical performance of sodium-ion batteries. Instead of their traditional carbon composites, the Emeraldine salt PANI/SnO2 nanocomposite to alleviate the high volume change (pulverization) and improve conductivity of SnO2 material is synthesized with an emulsion polymerization method by in situ polymerization of aniline on the SnO2 surface. The the Emeraldine salt PANI not only exhibits high flexibility to alleviate the high volume change of SnO2 nanoparticles, but also enhances the conductivity of electrons and sodium ions. Furthermore, the Emeraldine salt PANI coating enhanced the coulombic efficiency of SnO2 electrode. Therefore, Emeraldine salt Polyaniline coating is a promising buffer material for relieving a high volume change and enhancing coulombic efficiency, especially in the first cycle, and anode durability with the high electrochemical performance for sodium-ion batteries.

In-situ Transmission Electron Microscopy for Sodium-ion Batteries.

Sodium-ion batteries have attracted tremendous attentions in recent years due to the abundance and wide distribution of Na resource on the earth. However, SIBs still face the critical issues of low energy density and unsatisfactory cyclic stability at present. The enhancement of electrochemical performance of SIBs depends on comprehensive and precise understandings on the underlying sodium storage mechanism. Although extensive transmission electron microscopy investigations have been performed to reveal the sodium storage property and mechanism of SIBs, a dedicated review on the in-situ TEM investigations of SIBs has not been reported. In this review, recent progress in the in-situ TEM investigations on the morphological, structural and chemical evolutions of cathode materials, anode materials and solid-electrolyte interface during the sodium storage of SIBs have been comprehensively summarized. The detailed relationship between structure/composition of electrode materials and electrochemical performance of SIBs have been clarified. This review aims to provide insights into the effective selection and rational design of advanced electrode materials for high-performance SIBs. This article is protected by copyright. All rights reserved.

Tunnel/Layer Composite Na0.44MnO2 Cathode Material with Enhanced Structural Stability via Cobalt Doping for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are the most promising alternative to lithium-ion batteries (LIBs) due to their low cost and environmental friendliness; therefore, enhancing the performance of SIBs' components is crucial. Although most of the studies have focused on single-phase cathode electrodes, these materials have difficulty in meeting the requirements in practice. At this point, composite materials show superior performance due to balancing different structures and are offered as an alternative to single-phase cathodes. In this study, we synthesized a Na0.44MnO2/Na0.7MnO2.05 composite material in a single step with cobalt substitution. Changes in the crystal structure and the physical and electrochemical properties of the composite and bare structures were studied. We report that even if the initial capacity is slightly lower, the rate and cyclic performance of the 1% Co-substituted composite sample (CO10) are superior to the undoped Na0.44MnO2 (NMO) and 5% Co-substituted (CO50) samples after 100 cycles. The results show that with the composite cathode phase transformations are suppressed, structural degradation is prevented, and better battery performance is achieved.

Enhancing the Initial Coulombic Efficiency of Sodium-Ion Batteries via Highly Active Na2 S as Presodiation Additive.

Recently, sodium-ion batteries (SIBs) have received considerable attention for large-scale energy storage applications. However, the low initial Coulombic efficiency of traditional SIBs severely impedes their further development. Here, a highly active Na2 S-based composite is employed as a self-sacrificial additive for sodium compensation in SIBs. The in situ synthesized Na2 S is wrapped in a carbon matrix with nanoscale particle size and good electrical conductivity, which helps it to achieve a significantly enhanced electrochemical activity as compare to commercial Na2 S. As a highly efficient presodiation additive, the proposed Na2 S/C composite can reach an initial charge capacity of 407mAhg-1 . When 10wt.% Na2 S/C additive is dispersed in the Na3 V2 (PO4 )3 cathode, and combined with a hard carbon anode, the full cell achieves 24.3% higher first discharge capacity, which corresponds to a 18.3% increase in the energy density from 117.2 to 138.6Whkg-1 . Meanwhile, it is found that the Na2 S additive does not generate additional gas during the initial charging process, and under an appropriate content, its reaction product has no adverse impact on the cycling stability and rate performance of SIBs. Overall, this work establishes Na2 S as a highly effective additive for the construction of advanced high-energy-density SIBs.

Optimizing Electrochemical Performance in Sodium-Ion Batteries using O3-type Na0.90Cu0.22Fe0.30Mn0.48O2 and Hard Carbon

Sodium-ion batteries (SIBs) are being viewed as a prime alternative to lithium-ion batteries (LIBs) due to their resource availability, cost-effectiveness, safety, and superior power performance. Layered transition metal oxide cathode materials, in particular, have garnered interest for their high theoretical capacity and extended cycle life. This study focuses on the O3-type Na0.90Cu0.22Fe0.30Mn0.48O2(NCFMO), synthesized using the polyvinylpyrrolidone combustion method, showcasing notable specific capacity and capacity retention of over 80% after 200 cycles at 1C. Hard carbon has been identified as a potential candidate for commercialization among various anode materials, due to its high reversible capacity and stable structure. We assembled and evaluated a coin SIB full cell comprised of an NCFMO cathode and hard carbon anode (HC), which demonstrated optimal electrochemical performance at a positive-to-negative capacity ratio of 0.9. The study also explored the influence of the electrolyte on electrochemical performance, with NaClO4 (0.1 M NaClO4 in PC = 100 Vol% with 2.0%FEC) found to deliver the best results. Further, we assessed the heat generation characteristics of the NCFMO/HC full cell, revealing higher total heat generation during charging compared to discharging. This comprehensive study contributes significantly to the ongoing efforts towards commercialization of SIBs.

Effect of Ti doping on the structural and electrochemical performance of O3-type Na(Ni0.3Fe0.2Mn0.5)1−xTixO2 cathode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have shown great potential as energy storage devices due to their low price and abundant sodium content. In terms of current research, cathode materials remain the bottleneck for improving the performance of SIBs. Ti-doped O3-type Na(Ni0.3Fe0.2Mn0.5)1−xTixO2 (x = 0, 0.05, 0.1, 0.15) are investigated as the cathode material for sodium-ion batteries, and the results show that Ti doping can widen the layer spacing and suppress the ordering of Na+/vacancy and O3-P3 phase transition. The structurally stable Na(Ni0.3Fe0.2Mn0.5)0.9Ti0.1O2 cathode material, in particular, demonstrates enhanced rate capacity (93 mAh g−1, 2.0–4.0 V vs Na+/Na, 10 C, and 115 mAh g−1, 2.0–4.2 V vs Na+/Na, 10 C) and excellent cycling stability (87.5% capacity retention, 2.0–4.0 V vs Na+/Na, after 300 cycles, 1 C, and 82.1% capacity retention, 2.0–4.2 V vs Na+/Na, after 100 cycles, 1 C). In addition, Ti doping can effectively suppress the O3-P3 phase transition of the cathode materials and reduce the formation of the P3 phase at high voltage, which effectively suppresses the capacity decay during the charge/discharge process and reduces the irreversible capacity. As a result, the Ti doping strategy provides a simple and effective method for designing and developing high-performance layered oxide cathode materials for sodium-ion batteries.

A High‐Performance Alloy‐Based Anode Enabled by Surface and Interface Engineering for Wide‐Temperature Sodium‐Ion Batteries

AbstractAlloy‐based anodes have shown great potential to be applied in sodium‐ion batteries (SIBs) due to their high theoretical capacities, suitable working potential, and abundant earth reserves. However, their practical applications are severely impeded by large volume expansion, unstable solid‐electrolyte interfaces (SEI), and sluggish reaction kinetics during cycling. Herein, a surface engineering of tin nanorods via N‐doped carbon layers (Sn@NC) and an interface engineering strategy to improve the electrochemical performance in SIBs are reported. In particular, the authors demonstrate that uniform surface modification can effectively facilitate electron and sodium transport kinetics, confine alloy pulverization, and simultaneously synergize interactions with the ether‐based electrolyte to form a robust organic‐inorganic SEI. Moreover, it is discovered that the diethylene glycol dimethyl ether electrolyte with strong stability and an optimized Na+ solvation structure can co‐embed the carbon layer to achieve fast reaction kinetics. Consequently, Sn@NC anodes deliver extra‐long cycling stability of more than 10 000 cycles. The full cell of Na3V2(PO4)3║Sn@NC exhibits high energy density (215 Wh kg−1), excellent high‐rate capability (reaches 80% capacity in 2 min), and long cycle life over a wide temperature range of −20 to 50 °C.

Sodium Storage Properties of Carbonaceous Flowers.

As a promising energy storage system, sodium-ion batteries face challenges related to the stability and high-rate capability of their electrode materials, especially carbon, which is the most studied anode. Previous studies have demonstrated that three-dimensional architectures composed of porous carbon materials with high electrical conductivity have the potential to enhance the storage performance of sodium-ion batteries. Here, high-level N/O heteroatoms-doped carbonaceous flowers with hierarchical pore architecture are synthesized through the direct pyrolysis of homemade bipyridine-coordinated polymers. The carbonaceous flowers could provide effective transport pathways for electrons/ions, thus allowing for extraordinary storage properties in sodium-ion batteries. As a consequence, sodium-ion battery anodes made of carbonaceous flowers exhibit outstanding electrochemical features, such as high reversible capacity (329 mAh g-1 at 30 mA g-1), superior rate capability (94 mAh g-1 at 5000 mA g-1), and ultralong cycle lifetimes (capacity retention rate of 89.4% after 1300 cycles at 200 mA g-1). To better investigate the sodium insertion/extraction-related electrochemical processes, the cycled anodes are experimentally analyzed with scanning electron microscopy and transmission electron microscopy. The feasibility of the carbonaceous flowers as anode materials was further investigated using a commercial Na3V2(PO4)3 cathode for sodium-ion full batteries. All these findings indicate that carbonaceous flowers may possess great potential as advanced materials for next-generation energy storage applications.

Flexible and free-supporting Prussian blue analogs /MXene film for high-performance sodium-ion batteries

Sodium-ion batteries are the most promising alternative to lithium-ion batteries because of their low cost and environmental friendliness. Prussian blue analogs (PBAs) have attracted the attention of researchers because of their open skeleton structure and abundant redox active sites. However, the interstitial water in its crystal structure and poor electron conductivity limit its performance in sodium-ion batteries. A flexible self-supporting electrode is prepared by anhydrous preparation in a ball mill and simple filtration method. The high surface area nanoparticles and the high flexibility MXene layer in the electrode adapt to the rapid Na+ dynamics, alleviating the electrode expansion. The formation of a NaF-rich cathode-electrolyte interface (CEI) layer on the electrode surface inhibits the erosion of active substances by electrolyte, reduces the capacity attenuation of the electrode, and enhances the cyclic stability of the electrode. Electrode without a conductive agent and binder shows excellent electrochemical performance. The discharge capacity of the electrode is 58.3 mAh g−1at 1000 mA g−1 current density, and the capacity retention rate is 59.7% after 1000 cycles. This work has implications for the design of the next generation of low-cost, flexible, and fast charge and discharge energy storage devices.

Unveiling Atom Migration Abilities Affected Anode Performance of Sodium-Ion Batteries.

In sodium-ion batteries (SIBs), the low initial coulombic efficiency (ICE) is commonly induced by irreversible phase conversion and difficult desodiation, especially on transition metal compounds (TMCs). Yet the underlying physicochemical mechanism of poor reaction reversibility is still a controversial issue. Herein, by using in situ transmission electron microscopy and in situ X-ray diffraction, we demonstrate the irreversible conversion of NiCoP@C is caused by the rapid migration of P in carbon layer and preferential formation of isolated Na3 P during discharge. By modifying the carbon coating layer, the migration of Ni/Co/P atoms is inhibited, thus the improvement of ICE and cycle stability is realized. The inhibiting of fast atom migration which induces component separation and rapid performance degradation might be applied to a wide range of electrode materials, and guides the development of advanced SIBs.