With the unprecedentedly increasing demand for renewable and clean energy sources, the sodium-ion battery (SIB) is emerging as an alternative or complementary energy storage candidate to the present commercial lithium-ion battery due to the abundance and low cost of sodium resources. Layered transition metal oxides and Prussian blue analogs are reviewed in terms of their commercial potential as cathode materials for SIBs. The recent progress in research on their half cells and full cells for the ultimate application in SIBs are summarized. In addition, their electrochemical performance, suitability for scaling up, cost, and environmental concerns are compared in detail with a brief outlook on future prospects. It is anticipated that this review will inspire further development of layered transition metal oxides and Prussian blue analogs for SIBs, especially for their emerging commercialization.

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The Cathode Choice for Commercialization of Sodium-Ion Batteries: Layered Transition Metal Oxides versus Prussian Blue Analogs

Conversion-type transition-metal phosphide anode materials with high theoretical capacity usually suffer from low-rate capability and severe capacity decay, which are mainly caused by their inferior electronic conductivities and large volumetric variations together with the poor reversibility of discharge product (Li3P), impeding their practical applications. Herein, guided by density functional theory calculations, these obstacles are simultaneously mitigated by confining amorphous FeP nanoparticles into ultrathin 3D interconnected P-doped porous carbon nanosheets (denoted as FeP@CNs) via a facile approach, forming an intriguing 3D flake-CNs-like configuration. As an anode for lithium-ion batteries (LIBs), the resulting FeP@CNs electrode not only reaches a high reversible capacity (837 mA h g-1 after 300 cycles at 0.2 A g-1) and an exceptional rate capability (403 mA h g-1 at 16 A g-1) but also exhibits extraordinary durability (2500 cycles, 563 mA h g-1 at 4 A g-1, 98% capacity retention). By combining DFT calculations, in situ transmission electron microscopy, and a suite of ex situ microscopic and spectroscopic techniques, we show that the superior performances of FeP@CNs anode originate from its prominent structural and compositional merits, which render fast electron/ion-transport kinetics and abundant active sites (amorphous FeP nanoparticles and structural defects in P-doped CNs) for charge storage, promote the reversibility of conversion reactions, and buffer the volume variations while preventing pulverization/aggregation of FeP during cycling, thus enabling a high rate and highly durable lithium storage. Furthermore, a full cell composed of the prelithiated FeP@CNs anode and commercial LiFePO4 cathode exhibits impressive rate performance while maintaining superior cycling stability. This work fundamentally and experimentally presents a facile and effective structural engineering strategy for markedly improving the performance of conversion-type anodes for advanced LIBs.

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Achieving Fast and Durable Lithium Storage through Amorphous FeP Nanoparticles Encapsulated in Ultrathin 3D P-Doped Porous Carbon Nanosheets.

With the ever-increasing adaption of large-scale energy storage systems and electric devices, the energy storage capability of batteries and supercapacitors has faced increased demand and challenges. The electrodes of these devices have experienced radical change with the introduction of nano-scale materials. As new generation materials, heterostructure materials have attracted increasing attention due to their unique interfaces, robust architectures, and synergistic effects, and thus, the ability to enhance the energy/power outputs as well as the lifespan of batteries. In this review, the recent progress in heterostructure from energy storage fields is summarized. Specifically, the fundamental natures of heterostructures, including charge redistribution, built-in electric field, and associated energy storage mechanisms, are summarized and discussed in detail. Furthermore, various synthesis routes for heterostructures in energy storage fields are roundly reviewed, and their advantages and drawbacks are analyzed. The superiorities and current achievements of heterostructure materials in lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), lithium-sulfur batteries (Li-S batteries), supercapacitors, and other energy storage devices are discussed. Finally, the authors conclude with the current challenges and perspectives of the heterostructure materials for the fields of energy storage.

Emerging of Heterostructure Materials in Energy Storage: A Review.

Supercapacitors or ultracapacitors are considered as one of the potential candidates in the domain of energy storage devices for the forthcoming generations. These devices have earned their significance in numerous applications, viz., to power hybrid electric/electric vehicles and other power and electronic systems which require electrical energy for their operation. Supercapacitors are the most versatile devices which are most widely used for delivery of electrical energy in short time and in arenas which demand long shelf life. Therefore, the development of supercapacitors has huge market requirements, and long-term progress is needed for their successful advancement and commercialization. Meanwhile, supercapacitors are also facing challenges such as technical problems, establishing electrical parameter models, consistency testing, and establishing industrial standards. In this paper, the above challenges and the future development opportunities of supercapacitors are introduced in detail. This perspective will provide corresponding guidance and new directions for the development of supercapacitors.

Challenges and opportunities for supercapacitors

Recent Progress in Advanced Organic Electrode Materials for Sodium‐Ion Batteries: Synthesis, Mechanisms, Challenges and Perspectives

A covalent heterostructure of monodisperse Ni2P immobilized on N, P-co-doped carbon nanosheets for high performance sodium/lithium storage

Interface-rich core-shell ammonium nickel cobalt phosphate for high-performance aqueous hybrid energy storage device without a depressed power density

In this work, we report a novel design of mixed P2 + T phase NaxCo0.1Mn0.9O2 (0.44 ≤ x ≤ 0.7) with interface rich characteristics for high performance sodium storage, whereby the tunneled T phase offers fast Na ion diffusivity and excellent structural stability, the layered P2 phase contributes to high specific capacity, and the P2 + T phase interface offers additional channels and active sites for charge transfer and excess charge storage. Consequently, the as-prepared NaxCo0.1Mn0.9O2 (0.44 ≤ x ≤ 0.7) demonstrates an excellent discharge capacity of 219 mA h g−1 at a current rate of 0.1C (1C = 176 mA g−1), and retains 117 mA h g−1 even at a high rate of 5C. This outstanding performance is significantly superior to that of pure T-type Na0.44Co0.1Mn0.9O2 and P2-type Na0.7Co0.1Mn0.9O2, and also outperforms state-of-the-art manganese-based cathodes. The kinetic analysis indicates the drastically improved Na+ diffusion coefficient of the P2 + T phase, which is 6 and 200 times that of the pure T and P phases, respectively. The good reversibility and structural stability is evidenced through an ex situ XRD study.

Interface-rich mixed P2 + T phase NaxCo0.1Mn0.9O2 (0.44 ≤ x ≤ 0.7) toward fast and high capacity sodium storage

The invention provides a transitional metal phosphide-carbon composite material, which belongs to the field of electrochemical energy materials. A carbon precursor is used as a carbon source and a nitrogen source, the transitional metal ions are uniformly dispersed on a carbon precursor substrate by virtue of a complexing effect of the transitional metal ions and the carbon precursor, and the single-dispersed transitional metal phosphide nano particles are in-situ synthesized by virtue of the phosphorization process. The single-dispersed transitional metal phosphide nano particles are embeddedinto the carbon material substrate, so that the volume expansion of the phosphide particles in the charging-discharging process can be alleviated, the cycling stability of the material can be improved, the electric conductivity of the composite material can also be increased, the reaction dynamics process of an electrode is accelerated, the heteroatom-doped carbon is combined with the transitional metal phosphide by virtue of a covalent bond, so that the interaction of the heteroatom-doped carbon and the transitional metal phosphide is improved, the clustering problem of the phosphide particles in the charging and discharging process can be solved, and the synergistic effect between the carbon and phosphide improves the specific capacity and rate capability of the composite material.

Shanshan Shi

Papers

A covalent heterostructure of monodisperse Ni2P immobilized on N, P-co-doped carbon nanosheets for high performance sodium/lithium storage

Interface-rich core-shell ammonium nickel cobalt phosphate for high-performance aqueous hybrid energy storage device without a depressed power density

Interface-rich mixed P2 + T phase NaxCo0.1Mn0.9O2 (0.44 ≤ x ≤ 0.7) toward fast and high capacity sodium storage

Transitional metal phosphide-carbon composite material as well as preparation method and application thereof