Practical Sodium-ion Batteries Research Articles

Low-Surface-Area Nitrogen-Doped Carbon Submicrospheres as High-Coulombic-Efficiency and High-Capacity Anodes for Practical Sodium-Ion Batteries.

Nitrogen-doped carbon submicrospheres (NCSMs) are synthesized via an efficient and environmentally friendly one-pot polymerization reaction at room temperature, in which dopamine hydrochloride serves as the source for both carbon and nitrogen. Through leverage of its distinctive structure characterized by minimal surface area, fewer oxygen-containing functional groups, and a heightened presence of active nitrogen-doping sites, the synthesized NCSM showcases a noteworthy initial Coulombic efficiency (ICE) of 84.8%, a remarkable sodium storage capacity of 384 mAh g-1, an impressive rate capability of 215 mAh g-1 at 10 A g-1, and a superior cyclic performance, maintaining 83.0% of its capacity after 2000 cycles. The submicron spherical structure, with its limited surface area and scarce oxygen-containing moieties, effectively curtails the irreversible sodium-ion loss in solid-electrolyte interphase film formation, resulting in heightened ICE. The abundant nitrogen doping can expand carbon-layer spacing as well as improve the electron/ion-transport dynamics, guaranteeing a high sodium storage capacity and a strong rate capability. Crucially, the synthesis method presented here is straightforward, effective, and amenable to scaling, offering a novel avenue for the commercialization of sodium-ion batteries.

Achieving rapid sodiation/desodiation kinetics in NASICON-structured Na3MnTi(PO4)3 via Cr doping

Na3MnTi(PO4)3 is one of the most promising cathode candidates for sodium-ion batteries owing to its low cost, high operating voltage, and large reversible capacity. However, its electrochemical performance is significantly impeded by its deteriorative structure and sluggish Na+ diffusion kinetics. Herein, Cr-doping is introduced to tailor the structure of Na3MnTi(PO4)3, which helps to lengthen the Na2-O bond and expand the Na ion diffusion channels. X-ray diffraction, cyclic voltammetry, galvanostatic intermittent titration technique, and first principle calculations confirm the broadened diffusion channel for Na+ and facilitated Na+ diffusion rate after Cr-doping. As a result, the Na3.1MnTi0.9Cr0.1(PO4)3 electrode exhibits superior electrochemical performance with high discharge capacity (167.5 mAh g–1 at 0.1 C), outstanding rate capability (127.5 mAh g–1 at 10 C), and remarkable cyclability (70.56 % retention after 1400 cycles at 5 C). We believe that the results are useful for the design of high-performance NASICON-structured cathode materials for practical sodium-ion batteries.

Highly Stable ZnS Anodes for Sodium-Ion Batteries Enabled by Structure and Electrolyte Engineering.

Zinc sulfide is a promising high-capacity anode for practical sodium-ion batteries, considering its high capacity and the low cost of zinc and sulfur sources. However, the pulverization of particulate zinc sulfide causes active mass collapse and penetration-induced short circuits of batteries. Herein, a zinc sulfide encapsulated in a nitrogen-doped carbon shell (ZnS@NC) was developed for high-performance anodes. The confinement effect of nitrogen-doped carbon stabilizes the active mass structure during cycling thanks to the robust chemically and electronically bonded connections between nitrogen-doped carbon and zinc sulfide nanoparticles. Furthermore, the cycling stability of the ZnS@NC anode is boosted by the robust inorganic-rich solid electrolyte interphase (SEI) formed in cyclic and linear ether-based electrolytes. The ZnS@NC anode displayed a reversible specific capacity of 584 mAh g-1, an excellent rate capability of 327 mAh g-1 at 70 A g-1, and a highly stable cycling performance over 10000 cycles. This work provides a practical and promising approach to designing stable conversion anodes for high-performance sodium-ion batteries.

Exploration of PVP-Combustion Synthesis and Electrochemical Performance of O3-type NaxNi0.33Fe0.33Mn0.33O2 Layered Material for Sodium-Ion Batteries

The performance of sodium-ion batteries critically depends on the cathode materials used, making it essential to explore and optimize suitable candidates. Among them, O3-structured NaNi0.33Fe0.33Mn0.33O2 has emerged as one of the most promising cathode materials due to its outstanding electrochemical properties. However, there still exists a knowledge gap regarding the detailed synthesis conditions and the comprehensive performance of the full cell using this material. In this study, we investigated the influence of synthesis temperature, time, and sodium content on the electrochemical performance and charge-discharge kinetics of O3-structured NaNi0.33Fe0.33Mn0.33O2, prepared via the PVP-gel combustion method. Through systematic analysis, we elucidated the impact of these synthesis parameters on the material’s properties and battery performance. The results revealed that the optimized conditions led to a cathode material with superior electrochemical performance, exhibiting enhanced capacity with 139 mAh g−1 at 0.1 C and 96 mAh g−1 at 10 C. Additionally, a full cell using the optimized cathode material was studied, showing promising performance. This research sheds light on the significance of synthesis parameters in tailoring the electrochemical properties of O3-structured NaNi0.33Fe0.33Mn0.33O2 for sodium-ion batteries. The insights gained from this study hold valuable implications for the further development of practical sodium-ion battery cathode materials.

Engineering Routes Towards Practical Sodium-Ion Batteries: Case Studies from Oxides to Polyanion Compounds

Benefiting from the substantial knowledge accumulated on lithium-ion batteries, tremendous progress rapidly occurred with focus on solving the fundamental issues encountered at the component, system and cost levels in sodium-ion batteries. Of particular interest, P2-type layered oxide, Na2/3Fe1/2Mn1/2O2, has been researched as a potential cathode in SIBs based on its high theoretical capacity of 260 mA h/g and use of noncritical materials. Firstly, we reported a novel synthesis route using low-temperature eutectic reaction to produce highly homogeneous, crystalline, and impurity-free P2-type Na2/3Fe1/2Mn1/2O2 materials. We further synthesized Na x NiyMn1-yO2 cathodes with the same eutectic method and investigated the gassing properties of pouch cells when being charged to higher voltages. Even with gained knowledge of how to engineer layered oxide cathodes, the compromised electrochemical performances and associated safety risks at high voltage still hinder their high-energy applications. In contrast, polyanion cathode stands out as a great candidate due to its high nominal voltage and stability in ambient environment. However, pristine Na3V2(PO4)3 often exhibits reversible capacities of around 100 mAh/g for long term cycling, which is still 20% below the theoretical values. To tackle this issue, transition metal (Fe, Mn, Ni) and fluorine ion were introduced as doping elements to improve the specific capacity and cycling stability of polyanion cathodes. Advanced characterization results provided insights in the charge compensation mechanism of these cathodes. Stable electrochemical performances were demonstrated in multiple cell configurations. It is thus believed that these polyanion cathodes are promising for the next generation practical sodium-ion batteries.

(Invited) Heterostructure Engineering in Electrode Materials for Sodium Ion Batteries

Sodium-ion batteries (SIBs) have stepped into the spotlight as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage systems. However, the stability and performance of sodium ion battery electrode materials are lacking compared to their lithium counterparts as a consequence of the larger size of the Na+ ion compared to Li+. Heterostructure engineering is a promising strategy to overcome these intrinsic limitations toward practical SIBs. In this talk, we review the recent progress in heterostructure engineering of electrode materials and the origin of the phase interface’s influence on the Na+ storage and transport properties. Efficient strategies for the design and fabrication of heterostructures are discussed, with focus on the mechanism of heterostructure formation. The heterostructure’s influence on Na+ storage and transport properties is primarily generated from local distortions of the structure and chemomechanical coupling at the phase interface, which may accelerate ion/electron diffusion, create additional active sites, and bolster the structural stability. Finally, we will discuss the existing challenges, knowledge gaps, and opportunities toward the advancement of heterostructure engineering as a means to develop practical, high-performance sodium ion batteries.

High-voltage stability of O3-type sodium layered cathode enabled by preferred occupation of Na in the OP2 phase

Cobalt-free O3-type layered sodium nickel manganese oxide, Na[Ni0.5Mn0.5]O2, is one of the most attractive candidates as a cathode material for low-cost and practical sodium-ion batteries (SIBs). However, stable cycling with high reversible capacity in SIBs using Na[Ni0.5Mn0.5]O2 as a cathode is still hampered by an irreversible phase transition at voltages above 4.0 V (vs. Na/Na+). In this study, to suppress the detrimental phase transition, Mg substitution into Ni sites is proposed, and a series of Na[Ni0.5-xMgxMn0.5]O2 (x = 0, 0.05, 0.1 and 0.15) materials are synthesized and characterized. The substitution of Mg over 10 mol% into Ni site regulates sodium occupancy into P-type stacking, resulting in the OP2 phase upon high-voltage operation. This enables the material to tolerate strains in the crystal structure by alleviating the irreversible O3′−O3″ phase transition, which was evidenced by the results of operando X-ray diffraction and density functional theory calculation. Compared to its corresponding members, the optimized Na[Ni0.4Mg0.1Mn0.5]O2 cathode delivers a high reversible capacity of 177 mAh g−1 as well as improved cycling stability and rate capability in the wide voltage range of 2.0 − 4.3 V. Moreover, the Mg substitution strategy enhances the thermal and chemical stability against moisture, indicating its excellent practical applicability.

Diatomite-Templated Synthesis of Single-Atom Cobalt-Doped MoS2 /Carbon Composites to Boost Sodium Storage.

2D transition metal dichalcogenides (TMDCs) and single-atom catalysts (SACs) are promising electrodes for energy conversion/storage because of the layered structure and maximum atom utilization efficiency. However, the integration of such two type materials and the relevant sodium storage applications remain daunting challenges. Here, an ingenious diatomite-templated synthetic strategy is designed to fabricate single-atom cobalt-doped MoS2 /carbon (SA Co-MoS2 /C) composites toward the high-performance sodium storage. Benefiting from the unique hierarchical structure, high electron/sodium-ion conductivity, and abundant active sites, the obtained SA Co-MoS2 /C reveals remarkable specific capacity (≈604.0 mAh g-1 at 0.1 A g-1 ), high rate performance, and outstanding long cyclic stability. Particularly, the sodium-ion full cell composed of SA Co-MoS2 /C anode and Na3 V2 (PO4 )3 cathode demonstrates unexpected stability with the cycle number exceeded 1200. The internal sodium storage mechanism is clarified with the aid of density functional theory calculations and in situ experimental characterizations. This work not only represents a substantial leap in terms of synthesizing SACs on 2D TMDCs but also provides a crucial step toward the practical sodium-ion battery applications.

Regulating electron distribution of P2-type layered oxide cathodes for practical sodium-ion batteries

For transition metal oxide materials, high Ni content is an effective method to obtain a high specific capacity. However, the theoretical capacity is determined due to the certain amount of variable charges of transition metal ions. The increased capacity in specific voltage window may attribute to the easier transport of alkali ions, instead of more active elements. Borrowing the theory of Ni-rich materials in LIB, excess Ni elements were added into P2-type layered oxide material to form the Jahn-Teller active Ni3+ ions. About 25%-61% Ni3+ ions can effectively promote de-/intercalation of Na+ ions due to the decreased diffusion energy barrier and increased adsorption energy of Na+. The preferred “Ni-rich” material Na0.67Mn0.45Ni0.22Co0.33O2 (Ni-R1) shows a reversible specific capacity of 114 mA h g−1 in the voltage range of 2.0–4.25 V. In addition, it shows an excellent cycle stability, the capacity retention ration is 80% after 1000 cycles at a current density of 1 A g−1. The in-depth study proves that, Jahn-Teller active Ni3+ ions can effectively regulate the valence electron distribution of surrounding ions in synthesis stage. However, it will promote Jahn-Teller distortion when the Ni3+ content is increased to 74%, which makes the rate performance deteriorate dramatically. The present work provides a simple and efficient way to increase the capacity in suitable voltage range for application.

Structure and Interface Engineering of Ultrahigh-Rate 3D Bismuth Anodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have attracted tremendous attention as promising low-cost energy storage devices in future grid-scale energy management applications. Bismuth is a promising anode for SIBs due to its high theoretical capacity (386mAhg-1 ). Nevertheless, the huge volume variation of Bi anode during (de)sodiation processes can cause the pulverization of Bi particulates and rupture of solid electrolyte interphase (SEI), resulting in quick capacity decay. It is demonstrated that rigid carbon framework and robust SEI are two essentials for stable Bi anodes. A lignin-derived carbonlayer wrapped tightly around the bismuth nanospheres provides a stable conductive pathway, while the delicate selection of linear and cyclic ether-based electrolytes enable robust and stable SEI films. These two merits enable the long-term cycling process of the LC-Bi anode. The LC-Bi composite delivers outstanding sodium-ion storage performance with an ultra-long cycle life of 10 000 cycles at a high current density of 5Ag-1 and an excellent rate capability of 94% capacity retention at an ultrahigh current density of 100Ag-1 . Herein, the underlying origins of performance improvement of Bi anode are elucidated, which provides a rational design strategy for Bi anodes in practical SIBs.

Electrolyte Engineering on Performance Enhancement of NiCo2 S4 Anode for Sodium Storage.

NiCo2 S4 is an attractive anode for sodium-ion batteries (SIBs) due to its high capacity and excellent redox reversibility. Practical deployment of NiCo2 S4 electrode in SIBs, however, is still hindered by the inferior capacity and unsatisfactory cycling performance, which result from the mismatch between the electrolyte chemistry and electrode. Herein, a functional electrolyte containing 1.0m NaCF3 SO3 in diethylene glycol dimethyl ether (DEGDME) (1.0m NaCF3 SO3 -DEGDME) is developed, which can be readily used for NiCo2 S4 anode with high initial coulomb efficiency (96.2%), enhanced cycling performance, and boosted capacities (341.7mA h g-1 after 250 continuous cycles at the current density of 200mA g-1 ). The electrochemical tests and related phase characterization combined with density functional theory (DFT) calculation indicate the ether-based electrolyte is more suitable for the NiCo2 S4 anode in SIBs due to the formation of a stable electrode-electrolyte interface. Additionally, the importance of the voltage window is also demonstrated to further optimize the electrochemical performance of the NiCo2 S4 electrode. The formation of sulfide intermediates during charging and discharging is predicted by combining DFT and verified by in situ XRD and HRTEM. The findings indicate that electrolyte engineering would be an effective way of performance enhancement for sulfides in practical SIBs.

A new high voltage alluaudite sodium battery insertion material

Large-scale stationary storage forms a key sector that can be economically served by sodium-ion batteries. In realizing practical sodium-ion batteries, discovery and development of novel cathodes is essential. In this spirit, alluaudite-type Na2Fe2(SO4)3 was reported in 2014 to have the highest Fe3+/Fe2+ redox potential (∼3.8 V vs. Na). This finding led to reports on various PO43− and SO42− based alluaudite compounds exhibiting high energy densities. In 2017, MoO42− based alluaudite, Na2.67Mn1.67(MoO4)3, was found as a 3.45 V cathode material. Exploring molybdenum chemistry further, this work reports alluaudite type Na3.36Co1.32(MoO4)3 (NCMo) as a novel versatile electroactive cathode for Li-ion and Na-ion batteries. It was synthesized by a wet solution-combustion route with a restricted annealing duration of 1 min at 600 °C. Calorimetric study revealed the formation enthalpy from component oxides (ΔH°f,ox = −575.49 ± 7.75 kJ/mol) to be highly exothermic. Unlike the sulfate class of alluaudites, this material is highly stable in air and moisture (ΔHds = 537.42 ± 0.78 kJ/mol). Having an ionic conductivity of 6.065 × 10−8 S/cm (at 50 °C), it offers a pseudo two-dimensional Na+ migration pathway. Without any material optimization, NCMo was found to work as a high-voltage insertion cathode (ca. 4.0 V vs. Na/Na+ and 4.1 V vs. Li/Li+) in sync with theoretically predicted potential of 3.98 V (vs. Na/Na+). Ex-situ X-ray diffraction and photoelectron spectroscopy studies revealed the occurrence of solid-solution redox mechanism solely involving Co3+/Co2+ redox centre. It benchmarks Na3.36Co1.32(MoO4)3 as a novel electrochemically active Mo-based alluaudite-type polyanionic cathode insertion material.

Electrode/electrolyte additives for practical sodium-ion batteries: a mini review

Problems of practical sodium-ion batteries.

Comprehensive study on improving the sodium storage performance of low-defect biomass-derived carbon through S or N doping

As a promising alternative to graphite, biomass hard carbon has attracted widespread attention in sodium-ion batteries (SIBs). Heteroatom doping can overcome the inherent shortcomings of hard carbon materials, such as low reversible capacity and poor rate performance. Herein, in this paper, a simple and efficient one-step synthesis method is adopted to pyrolyze the mixture of jute fiber carbon with urea (JFCN) or sulfur powder (JFCS) from high to low carbonization temperatures, and determines that high-performance doping is only suitable for relatively low temperatures. Benefiting from the low-defect and ordered structure doped by proper S or N under these temperatures, initial Coulombic efficiency and electrochemical stability of hard carbon materials have been significantly improved. Meanwhile, S doping is a more effective way than N doping, the former shows an ultrahigh reversible capacity exceeding 410 mAh g−1 after 100 cycles at 0.1 A g−1 and a remarkable rate performance of 234.3 mAh g−1 at 2.0 A g−1. Impressively, JFCN exhibits greater rate performance in ether electrolytes, while JFCS shows better stability in ester electrolytes. This work provides a broad application prospect for hard carbon materials to achieve low cost and high capacity as practical SIBs.

Artificial Organo-Fluoro-Rich Anode Electrolyte Interface and Partially Sodiated Hard Carbon Anode for Improved Cycle Life and Practical Sodium-Ion Batteries.

In this work, a strategy is introduced wherein without keeping any excess cathode, a practical full-cell sodium-ion battery has been demonstrated by utilizing a hard carbon (HC) anode and sodium vanadium fluorophosphate and carbon nanotube composite (NVPF@C@CNT) cathode. A thin, robust, and durable solid electrolyte interface (SEI) is created on the surface of HC through its incubation wetted with a fluoroethylene carbonate (FEC)-rich warm electrolyte in direct contact with Na metal. During the incubation, the HC anode is partially sodiated and passivated with a thin SEI layer. The sodium-ion full cell fabricated while maintaining N/P ∼1.1 showed the first cycle Coulombic efficiency of ∼97% and delivered a stable areal capacity of 1.4 mAh cm-2 at a current rate of 0.1 mA cm-2 realized for the first time to the best of our knowledge. The full cell also showed a good rate capability, retaining 1.18 mAh cm-2 of its initial capacity even at a high current rate of 0.5 mA cm-2, and excellent cycling stability, giving a capacity of ∼1.0 mAh cm-2 after 500 cycles. The current strategy presents a practical way to make a sodium-ion full cell, utilizing no excess cathode material, significantly saving cost and time.

Activating Oxygen Redox in Layered NaxMnO2 to Suppress Intrinsic Deficient Behavior and Enable Phase‐Transition‐Free Sodium Ion Cathode

AbstractP2‐type layered NaxMnO2 cathode shows great potential in practical sodium ion batteries, especially for grid‐level applications due to its eco‐friendly and cost‐effective sodium and manganese resources, and high theoretical specific capacity. However, several obstacles including severe phase transitions of P2‐O2 and P2‐P2′, low redox potential of Mn3+/Mn4+, disproportionation reaction and Jahn‐Teller distortion of Mn3+, and deficient behavior have already hindered its practical applications. Herein, a Li, Cu co‐doping strategy to tackle the mentioned obstacles by activating the oxygen redox is presented. The Li, Cu co‐doped material exhibits solid solution reaction without any phase transitions as proved by in situ X‐ray diffraction measurement and reduces the dissolution of active manganese element. With this modification treatment, it can dramatically raise the cycling stability from 30.4% to 80.1% after 150 cycles and simultaneously improves the deficient behavior due to the capacity contribution of oxygen redox at high voltage. More importantly, the coin‐cell type sodium ion full cell assembled with this cathode and commercial hard carbon anode delivers a promising energy density of 225.1 Wh kg–1.

Acid-Assisted Ball Mill Synthesis of Carboxyl-Functional-Group-Modified Prussian Blue as Sodium-Ion Battery Cathode.

Prussian blue attracts the attention of many researchers as a promising candidate for use in sodium-ion battery cathodes due to its open frameworks and high working potential. However, the interstitial water in its crystal structure and its poor electronic conductivity limits its performance in practical sodium-ion batteries. Here, acid-assisted ball milling synthesis was employed as a versatile method for the production of surface-modified Prussian blue. With (CH3COO)2Fe being used as the raw material, the Prussian blue produced using ball milling synthesis was modified by the carboxyl functional group on its surface, which resulted in lower interstitial water content and enhanced electrochemical cycling performance. In addition, ball milling synthesis provided the as-prepared Prussian blue with a large surface area, improving its electrochemical rate performance. When used as the cathode of sodium-ion batteries, as-prepared Prussian blue delivered a specific capacity of 145.3 mAh g−1 at 0.2 C and 113.7 mAh g−1 at 1 C, maintaining 54.5% of the initial capacity after 1000 cycles at 1 C (1 C = 170 mA g−1). Furthermore, a solid-state sodium-ion battery was mounted, with as-prepared Prussian blue being employed as the cathode and Na metal as the anode, which delivered a high specific capacity of 128.7 mAh g−1 at 0.2 C. The present study put forward an effective solution to overcome the limitations of Prussian blue for its commercial application.

Prussian Blue Analogues for Sodium-Ion Batteries: Past, Present, and Future.

Prussian blue analogues (PBAs) have attracted wide attention for their application in the energy storage and conversion field due to their low cost, facile synthesis, and appreciable electrochemical performance. At the present stage, most research on PBAs is focused on their material-level optimization, whereas their properties in practical battery systems are seldom considered. This review aims to first provide an overview of the history and parameters of PBA materials and analyze the fundamental principles toward rational design of PBAs, and then evaluate the prospects and challenges for PBAs for practical sodium-ion batteries, hoping to bridge the gap between laboratory research and commercial reality.

Exploration of a Na3V2(PO4)3/C –Pb full cell Na-ion prototype

Recent research focusses typically on sodium-ion half cells, and the progress of high performance and cost-effective full cells remains a critical obstacle to commercialize sodium-ion batteries. Here, we rationally design a full sodium-ion battery based on carbon coated Na3V2(PO4)3 (NVP-C) cathode and Pb anode materials. Carbon coated NVP is prepared via easy and one-step solid-state method. With 8 wt% carbon content, the obtained NVP-C core-shell structure provides an excellent reversible capacity of 104 mAh/g at C/10 rate, approaching towards its theoretical capacity. The NVP-C electrode even at a high 5 C rate delivers a primary reversible capacity of 87 mAh/g with 99.9% capacity retention almost after 3500 cycles. As an anode, Pb delivers an initial reversible capacity of 477 mAh/g at a fixed current density of 13 mA/g with a good cyclability and capacity retention of 98.5% over 50 cycles. The full cell constructed from the as-prepared materials exhibits a preliminary reversible capacity of 233 mAh/g at C/10 rate. In addition, the good rate capability including discharge energy density in the range of 170–180 Wh/kg makes the full cell a potential candidate in practical sodium-ion battery application. The excellent electrochemical behavior with simple, low-cost properties of fabricated full cell mark it as attractive option for high-energy energy storage applications.

Ice-Assisted Synthesis of Highly Crystallized Prussian Blue Analogues for All-Climate and Long-Calendar-Life Sodium Ion Batteries.

For practical sodium-ion batteries, both high electrochemical performance and cost efficiency of the electrode materials are considered as two key parameters. Prussian blue analogues (PBAs) are broadly recognized as promising cathode materials due to their low cost, high theoretical capacity, and cycling stability, although they suffer from low-crystallinity-induced performance deterioration. Herein, a facile "ice-assisted" strategy is presented to prepare highly crystallized PBAs without any additives. By suppressing structure defects, the cathode exhibits a high capacity of 123 mAh g-1 with initial Coulombic efficiency of 87.2%, a long cycling lifespan of 3000 cycles, and significantly enhanced high/low temperature performance and calendar life. Remarkably, the low structure distortion and high sodium diffusion coefficient have been identified via in situ synchrotron powder diffraction and first-principles calculations, while its thermal stability has been analyzed by in situ heated X-ray powder diffraction. We believe the results could pave the way to the low-cost and large-scale application of PBAs in all-climate sodium-ion batteries.