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Co shows excellent performance in the high voltage range for layered oxide cathode materials for sodium ion batteries (SIBs). However, its high cost and toxicity are significant disadvantages.Co‐free cathodes with high performance are urgently needed for development. Herein, cheap Mg and Ti elements are preferred to replace Co elements. A P2‐Na0.67Mn0.53Ni0.30Mg0.085Ti0.085O2 (Ni30MgTi) cathode shows a high reversible specific capacity of 118 mA h g−1 at a current density of 50 mA g−1 in 2.0–4.25 V, which is even higher than that in the base sample with Co. Moreover, Mg and Ti raise the median discharge voltage from 3.21 to 3.59 V, which raises the energy density from 325 to 410 Wh kg−1. On the other hand, ex situ XPS and in situ differential electrochemical mass spectrometry tests indicate that Ni30MgTi has a stable anionic redox reaction with reversible capacity in the high voltage range. The concept of bimetallic co‐substitution offers a simple and effective Co‐free strategy to reduce the cost and increase the energy density of layered oxide cathode materials simultaneously for SIBs. [ABSTRACT FROM AUTHOR]

As concerns about the safety of lithium‐ions batteries (LIBs) increases, aqueous zinc‐ion batteries (ZIBs) with a lower cost, higher safety, and higher co‐efficiency have attracted more and more interest. However, finding suitable cathode materials is still an urgent problem in ZIBs. In recent years, a lot of significant works have been reported, including manganese‐based cathodes, vanadium‐based cathodes, Prussian blue analog‐based materials, and sustainable quinone cathodes. In this review, some typical cathode materials are introduced. The detailed storage mechanisms and methods for improving the reaction kinetics of the zinc ions are summarized. Finally, the issues, challenges, and the research directions are provided. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) are the most promising candidates as alternatives to lithium‐ion batteries (LIBs), owing to the natural abundance of sodium salt and the low cost. However, the commercial application of SIBs is principally hampered by the absence of suitable cathode materials. Herein, a novel Na2FeP2O7@carbon/expanded graphite (NFPO@C/EG) composite with a unique microstructure was developed through a scalable sol‐gel process followed by a ball‐milling procedure with expanded graphite. Benefiting from the multiscale carbon‐modified structure, the NFPO@C/EG effectively improves the electronic conductivity and, at the same time, shortens the path of sodium ion transmission. As a consequence, the NFPO@C/EG cathode presents a much higher specific capacity and more stable cycling stability than NFPO@C and NFPO. The unique design of NFPO@C/EG endows a high ratio of pseudocapacitance contribution and a large Na+ diffusion coefficient. As a consequence, the NFPO@C/EG cathode displays stable cycle performance (82 mAh g−1 over 400 cycles at 232 mA g−1) and superior rate capability (60 mAh g−1 at a high charge/discharge density of 2320 mA g−1). This multiscale carbon‐modified design concept builds an avenue for the practical application of polyanionic cathode materials and promotes the development of low‐cost SIBs. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) have attracted much attention due to their abundance, easy accessibility, and low cost. All of these advantages make them potential candidates for large‐scale energy storage. The P2‐type layered transition‐metal oxides (NaxTMO2; TM=Mn, Co, Ni, Ti, Fe, V, Cr, and a mixture of multiple elements) exhibit good Na+ ion conductivity and structural stability, which make them an excellent choice for the cathode materials of SIBs. Herein, the structural evolution, anionic redox reaction, some challenges, and recent progress of NaxTMO2 cathodes for SIBs are reviewed and summarized. Moreover, a detailed understanding of the relationship of chemical components, structures, phase compositions, and electrochemical performance is presented. This Review aims to provide a reference for the development of P2‐type layered transition‐metal oxide cathode materials for SIBs. [ABSTRACT FROM AUTHOR]

Keywords: aqueous batteries; cathode materials; manganese; quinone cathodes; storage mechanisms; vanadium; Zn-ion batteries EN aqueous batteries cathode materials manganese quinone cathodes storage mechanisms vanadium Zn-ion batteries 1 1 1 01/18/21 20210113 NES 210113 B Aqueous zinc ion batteries (ZIBs) b are the most promising rechargeable batteries for the grid energy storage and industrial energy storage for its lower cost and higher safety. The cathode materials consist of Mn-based materials, V-based materials, Prussian blue analogous (PBAs), Quinone and the others materials. Aqueous batteries, cathode materials, manganese, quinone cathodes, storage mechanisms, vanadium, Zn-ion batteries. [Extracted from the article]

Frontispiece: Recent Progress of P2-Type Layered Transition-Metal Oxide Cathodes for Sodium-Ion Batteries Keywords: electrochemistry; layered compounds; redox chemistry; sodium; transition metals EN electrochemistry layered compounds redox chemistry sodium transition metals 1 1 1 06/25/20 20200623 NES 200623 B In P2-type layered transition-metal oxides b , high capacity requires more Na ions to join in the transition as the capacity is generated by their transition. Electrochemistry, layered compounds, redox chemistry, sodium, transition metals. [Extracted from the article]

N-doped carbon-encapsulated ZnSe@C with uniform core-shell nanorod structure has been successfully fabricated via a self-sacrificial template route. Due to the special porous nanorods structure, this ZnSe@C anode effectively moderates the volume expansion, improves the electron conductivity, and thus delivers a superior rate capability and stable cycling performance for KIBs. • Uniform core-shell ZnSe@C was synthesized via a facile self-sacrificial route. • Such ZnSe@C anode shows superior rate capability and cycling performance. • 1D carbon-encapsulated porous structure enhances the electrochemical performance. Potassium-ion batteries (KIBs) have now stimulated considerable attention due to the widely distributed potassium salt and low cost, which become the competitive candidate for Na-/Li-ion batteries and suitable application for large-scale energy systems. Here, we have reasonably designed N-doped carbon encapsulated yolk-shell ZnSe@C anode with carbon-coated Zn 2 GeO 4 @C nanorods as the self-sacrificial template. Uniform ZnSe@C nanorods were facilely prepared by the selenidation of carbon-coated Zn 2 GeO 4 @C nanorods, which were synthesized via a simple annealing of ploydopamine-coated Zn 2 GeO 4 nanorods. Such N-doped carbon encapsulated ZnSe@C core-shell nanorods could substantially enhance the electronic conductivity, moderate the volume expansion and provide more pathways for K+ diffusion. In detail, these ZnSe@C nanorods achieve stable galvanostatic discharge/charge performance (deliver 360 mA h g−1 at 0.2 A g−1 after 60 cycles and 204 mA h g−1 at 2.0 A g−1 over 100 repeated cycles) and superior rate capability (achieve a capacities of 389.4, 379.8, 352.2, 285.6, 226.1, and 167.5 mA h g−1 at 0.1, 0.2, 0.5, 1.0, 2.0, and 4.0 A g−1, respectively). The charge-discharge mechanism of ZnSe@C was further investigated by in-situ , ex-situ X-ray diffraction XRD and transmission electron microscopy (TEM) measurements. [ABSTRACT FROM AUTHOR]

A scalable and facile polymer-blowing and galvanic replacement route for 3D porous carbon framework embedded with uniform Sb nanoparticles have been synthesized Such designed electrode architecture provides porous structure, high structure stabilities, high electronic conductivity and robust buffer layers, which could solve the issue of poor ionic and electronic transport in electrode materials and accommodate the large volume expansion. • 3D porous Sb ⊂ 3DPC was synthesized via a scalable and facile polymer-blowing and galvanic replacement route. • 3D porous Sb ⊂ 3DPC anode show superior rate capability and cycling performance. • Such 3D porous interconnected carbon-encapsulated structure enhances the electrochemical performance. The development of high-performance Na-ion batteries in order to meet the increasing demand of the industrial applications of energy storage requires low cost and large-scale preparation methods for battery electrodes with outstanding performance. In this work, we have designed a novel anode of three-dimensional porous interconnected carbon matrix embedded with Sb nanoparticles (Sb ⊂ 3DPC) via a scalable and facile polymer-blowing and galvanic replacement route. This designed electrode architecture provides large surface areas, large pore volumes and interconnected pore frameworks, supplying enlarged interface of the electrolyte and electrode, reducing the diffusion pathway and inhibiting the volume expansion of Sb during cyclic movement. The as-prepared Sb ⊂ 3DPC anode shows high Na-storage performance, such as an outstanding cycle stability (461 mA h g−1 at 100 mA g−1 over 200 cycles) and exceptional high rate capability (349 mA h g−1 at 5000 mA g−1). As for the application in the full Na-ion batteries, the assembled Sb ⊂ 3DPC//Na 3 V 2 (PO 4) 3 full cell also shows remarkable rate capability. Such polymer-blowing-based approach provides a low cost, uncomplicated and large scale preparation method for porous and stable electrode materials and opens up a wide horizon in other electrochemical applications. [ABSTRACT FROM AUTHOR]