Material innovation on high‐performance Na‐ion cathodes and the corresponding understanding of structural chemistry still remain a challenge. Herein, we report a new concept of high‐entropy strategy ...to design layered oxide cathodes for Na‐ion batteries. An example of layered O3‐type NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2 has been demonstrated, which exhibits the longer cycling stability (ca. 83 % of capacity retention after 500 cycles) and the outstanding rate capability (ca. 80 % of capacity retention at the rate of 5.0 C). A highly reversible phase‐transition behavior between O3 and P3 structures occurs during the charge‐discharge process, and importantly, this behavior is delayed with more than 60 % of the total capacity being stored in O3‐type region. Possible mechanism can be attributed to the multiple transition‐metal components in this high‐entropy material which can accommodate the changes of local interactions during Na+ (de)intercalation. This strategy opens new insights into the development of advanced cathode materials.
My brave phase: A high entropy oxide (HEO) cathode, containing nine additional components, the layered O3‐phase NaNi0.12Cu0.12Mg0.12Fe0.15Co0.15Mn0.1Ti0.1Sn0.1Sb0.04O2, delivers long cycling stabilities and high rate capability. As more than 60 % of the capacity is stored in the O3‐type region, the entropy stabilization of the O3‐phase gives the cycling stability and better rate performance.
Disordered carbons have captured extensive interest as anode materials for Na‐ion batteries (NIBs) due to the abundant resources, competitive specific capacity, and low cost. Here, a facile strategy ...of pre‐oxidation is successfully adopted to tune the microstructure of carbon anode to facilitate sodium storage. Pitch is selected as the low‐cost and high carbon yield precursor. An easy pre‐oxidation treatment in air can enable pitch to realize an effective structural conversion from ordered to disordered at further carbonization processes. Compared with the carbonized pristine pitch, the carbonized pre‐oxidation pitch increases the carbon yield from 54 to 67%, the sodium storage capacity from 94.0 to 300.6 mAh g−1, and the initial Coulombic efficiency from 64.2 to 88.6%. Experiment results reveal that the introduction of oxygen based functional groups is the key to achieve the highly disordered structure, not only ensuring the cross‐linkage during low‐temperature pre‐oxidation process but also suppressing the carbon structure from melting and rearranging in the high‐temperature carbonization process. Most importantly, this facile pre‐oxidation strategy can also be extended to other carbon precursors to facilitate the low‐cost and high‐performance disordered carbon anodes for NIBs and beyond.
A disordered carbon anode for Na‐ion batteries with both low cost and high performance is achieved via a simple pre‐oxidation of pitch in air followed by high‐temperature carbonization, during which the electrochemical behavior is modulated from possessing only a sloping region to featuring both sloping and plateau regions and a threefold capacity improvement is attained through this microstructure tuning.
Rechargeable Na‐ion batteries (NIBs) are attractive large‐scale energy storage systems compared to Li‐ion batteries due to the substantial reserve and low cost of sodium resources. The recent rapid ...development of NIBs will no doubt accelerate the commercialization process. As one of the indispensable components in current battery systems, organic liquid electrolytes are widely used for their high ionic conductivity and good wettability, but the low thermal stability, especially the easy flammability and leakage make them at risk of safety issues. The booming solid‐state batteries with solid‐state electrolytes (SSEs) show promise as alternatives to organic liquid systems due to their improved safety and higher energy density. However, several challenges including low ionic conductivity, poor wettability, low stability/incompatibility between electrodes and electrolytes, etc., may degrade performance, hindering the development of practical applications. In this review, an overview of Na‐ion SSEs is first outlined according to the classification of solid polymer electrolytes, composite polymer electrolytes, inorganic solid electrolytes, etc. Furthermore, the current challenges and critical perspectives for the potential development of solid‐state sodium batteries are discussed in detail.
The booming solid‐state sodium batteries, based on solid‐state electrolytes (SSEs), have the promise to be potential alternatives to organic liquid systems due to their improved safety and higher energy density. Recent progress in SSEs, including solid polymer electrolytes, composite polymer electrolytes, inorganic solid electrolytes, etc. and their potential application in solid‐state batteries, are reviewed.
Hard carbon anode materials for sodium-ion batteries (SIB) have usually been tested in half-cells by cycling between 0–2V, and is believed to exhibit low rate capability. However, we find that the ...specific capacity, the rate performance, and the cycling performance may all be severely underestimated with the traditional half-cell cycling evaluation method, due to premature truncation of part II of the capacity (part I is “sloping”, part II is “plateauing”, while part III is Na metal deposition). Here we introduce a sodium-matched SIB full-cell architecture, with newly developed hard carbon derived from macadamia shell (MHC) as anode and NaCu1/9Ni2/9Fe1/3Mn1/3O2 (NCNFM) as the cathode material, with anode/cathode areal capacity ratio of 1.02–1.04. Our carefully balanced full-cells exhibit a cell-level theoretical specific energy of 215Whkg−1 at C/10 and 186Whkg−1 at 1C based on cathode-active and anode-active material weights, and an outstanding capacity retention of 70% after 1300 cycles (∼2000h). Traditional half-cell test (THT) of MHC using superabundant Na metal counter electrode shows only 51.7mAhg−1 capacity at 1C, and appears to die in no more than 100h due to low open-circuit voltage slope and large polarization. A revised half-cell test (RHT) which shows much better agreements with full-cell test results, delivers a specific capacity of 314mAhg−1, with an initial Coulombic efficiency of ∼91.4%, which is comparable to that of graphite anode in lithium-ion batteries.
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•A sodium-ion battery full-cell architecture with great stability and good rate performance is demonstrated.•A novel hard carbon with a high initial Coulombic efficiency of 91.4% is delivered.•The traditional half-cell test protocol is suggested to be revised.
Na-ion batteries (NIBs) have attracted significant attention owing to Na being an abundant resource that is uniformly distributed in the Earth’s crust. Several 3d transition metal (TM) ions have been ...thoroughly investigated as charge compensators in single or multiple composition systems to enhance the electrochemical performance of cathodes for the practical applications. In this review, the composition-structure-property relationship of Ni-based cathodes has been reviewed as a design perspective for NIB’s cathodes. The typical Ni-based cathode materials have been systematically summarized and comparatively analyzed, and it is demonstrated that Ni ions can be used to provide charge compensation. Moreover, Ni-based cathodes present high reversible capacity owing to the multi-electron redox reactions and suitable redox potential of Ni-ions redox. However, considering the abundance, cost, and hygroscopic properties of Ni element, the content of 0.15–0.35 per formula can be optimal for enhancing the performance of cathodes. Lastly, further perspectives on designing Ni-containing cathodes, including Ni-rich layered cathodes, have been discussed, which could promote the practical applications of NIBs for grid-scale energy storage in future.
Porous structure design is generally considered to be a reliable strategy to boost ion transport and provide active sites for disordered carbon anodes of Na‐ion batteries (NIBs). Herein, a type of ...waste cork‐derived hard carbon material (CC) is reported for efficient Na storage via tuning the pore species. Benefiting from the natural holey texture of this renewable precursor, CCs deliver a novel hierarchical porous structure. The effective skeletal density test combined with small angle X‐ray scattering analysis (SAXS) is used to obtain the closed pore information. Based on a detailed correlation analysis between pore information and the electrochemical performance of CCs, improving pyrolysis temperature to reduce open pores (related to initial capacity loss) and increase closed pores (related to plateau capacity) endows an optimal CC with a high specific capacity of ≈360 mAh g−1 in half‐cells and a high energy density of 230 Wh kg−1 in full‐cells with a capacity retention of 71% after 2000 cycles at 2C rate. The bioinspired high temperature pore‐closing strategy and the new insights about the pore structure–performance relationship provide a rational guide for designing porous carbon anode of NIBs with tailored pore species and high Na storage capacity.
A type of waste cork‐derived, hard carbon electrode, with hierarchical porous morphology delivers satisfactory electrochemical performance in Na‐ion batteries (both half‐cells and full‐cells) via tuning the pore species. Detailed pore analysis reveals a clear pore structure–performance relationship to guide the designing of advanced porous carbon anode and the related high temperature pore‐closing strategy can be extended to other pristine open‐pore‐rich carbon.
Novel reduced graphene oxide (RGO) nanosheet/PtPd nanowire hybrids were prepared by a mild wet chemical approach. Uniform Pt nanowire arrays are successfully supported on functionalized RGO ...nanosheets with Pd nanoparticles as growing seeds. The whole deposition process was achieved in aqueous solution at room temperature. TEM and HR-TEM analysis indicated the single-crystal feature of the Pt nanowires with a diameter of ca. 4nm in average and a length of 20–200nm. Electrochemical characterization demonstrated that the hybrid nanostructures have a higher catalytic activity and stability than commercial state-of-the-art platinum black catalysts (Hispec1000) toward the methanol oxidation reaction (MOR). An initial mass activity of 0.51Amg−1 and a degradation ratio of 17.2% after 1000 potential sweeping cycles were achieved for the hybrid nanostructures, compared with 0.44Amg−1 and 27.5% for Pt black, respectively, demonstrating a great potential of this RGO/PtPd hybrids for DMFC applications.
Hard carbon has long been considered the leading candidate for anode materials of Na‐ion batteries. Intensive research efforts have been carried out in the search of suitable carbon structure for an ...improved storage capability. Herein, an anode based on multishelled hollow carbon nanospheres, which are able to deliver an outstanding electrochemical performance with an extraordinary reversible capacity of 360 mAh g−1 at 30 mA g−1, is designed. An interesting dependence of the electrochemical properties on the multishelled structural features is identified: with an increase in the shell number of the model carbon materials, the sloping capacity in the charge/discharge curve remains almost unchanged while the plateau capacity continuously increases, suggesting an adsorption‐filling Na‐storage mechanism for the multishelled hollow hard carbon materials. The findings not only provide new perspective in the structural design of high‐performance anode materials, but also shed light on the complicated mechanism behind Na‐storage by hard carbon.
A high‐performance Na‐ion battery anode is developed via structural engineering of hard carbon into multishelled hollow carbon nanospheres (MS‐HCNs). The MS‐HCNs not only promise extraordinary capacities, but also provide an effective model for the mechanistic study of Na‐storage. The plateau capacities can be tuned independently by controlling the structure of the anodes, providing a directed proof for an adsorption‐filling Na‐storage mechanism.
Sodium‐ion batteries (NIBs) as an ideal candidate for large‐scale energy‐storage systems (ESSs) have been the subject of extensive attention worldwide as a result of the ever‐growing energy demands. ...Development of advanced NIB techniques with potentially higher performance is of great concern to meet the requirements of ESSs. Based on modern material characterization methods and technological optimizations, the systematic understanding of rechargeable batteries has been further developed. Novel methods for NIB materials could provide a rational guideline for the fundamental understanding and practical optimization of battery systems. Here, the focus is mainly on a discussion of novel or fresh experimental methods and characterization techniques for NIB materials from the relationships between properties and performances, which are roughly classified into four parts: structure‐related techniques, composition‐related techniques, size‐ and morphology‐related techniques, and surface‐ and interface‐related techniques. Respective detection mechanisms of each method will be discussed, and special attention is paid to examples of these characterization techniques for NIB devices. It is hoped that by the study of NIB‐related details, a certain reference to the development of advanced materials can be provided.
Novel methods for sodium‐ion battery (NIB) materials can provide rationality and guidelines for a more in‐depth understanding and practical optimization of battery systems, including redox reactions, the interaction of the electrodes with the electrolyte, and mechanisms for the function of each cell component.
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