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Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) is regarded as a promising cathode material for sodium-ion batteries due to its affordability, non-toxic nature, and excellent structural stability. However, its electrochemical performance is hampered by its poor electronic conductivity. Meanwhile, most of the previous studies utilized spray-drying and sol-gel methods to synthesize Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), and the large-scale synthesis of the cathode material is still challenging. This study presents a composite cathode material, Na 4 Fe 2.94 Al 0.04 (PO 4 ) 2 (P 2 O 7 )/C, prepared via a straightforward ball-milling technique. By substituting Al 3+ minimally into the Fe 2+ site of NFPP, Fe defects are introduced into the structure, hindering the formation of NaFePO 4 and thereby enhancing Na-ion diffusion kinetics and conductivity. Additionally, the average length of AlO bonds (2.18 Å) is slightly smaller than that of FeO bonds (2.19 Å), contributing to the superior structural stability. The smaller ionic radii of Al 3+ induce lattice contraction, further enhancing the structural stability. Moreover, the surface of material particles is coated with a thin layer of carbon, ensuring excellent electrical conductivity and outstanding structure stability. As a result, the Na 4 Fe 2.94 Al 0.04 (PO 4 ) 2 (P 2 O 7 )/C cathode exhibits excellent electrochemical performance, leading to high discharge capacity (128.1 mAh g -1 at 0.2 C), outstanding rate performance (98.1 mAh g -1 at 10 C), and long cycle stability (83.7 % capacity retention after 3000 cycles at 10 C). This study demonstrates a low-cost, ultra-stable, and high-rate cathode material prepared by simple mechanical activation for sodium-ion batteries which has application prospects for large-scale production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Olivine FePO 4 is widely regarded as an optimal cathode material for sodium-ion batteries due to its impressive theoretical capacity of 177.7 mAh g -1 . Nonetheless, the material's limited application stems from its intrinsic low electronic and ionic conductivities and ion diffusion rate. Previously, most modifications of olivine FePO 4 are conducted through electrochemical or ion exchange processes in organic solvents, which severely restricted its potential for large-scale applications. In this research, a novel water-based ion exchange method is proposed for the synthesis of Ni-doped, Mn-doped, and Ni, Mn co-doped FePO 4 @C, which is non-toxic, cost-effective, and demonstrating promising prospects for various applications. Fe 2.7 Mn 0.2 Ni 0.1 PO 4 @C (0.2Mn0.1Ni-FP@C) is synthesized by a straightforward ion exchange method in aqueous media. The material exhibits a discharge capacity of 154.4 mAh g -1 at 0.1C rate. After 300 cycles at 1C, the capacity retention rate remains at 70.7 %. Numerous tests and calculations conducted in this study demonstrate that 0.2Mn0.1Ni-FP@C, modified through Mn 3+ and Ni 3+ co-doping, exhibits superior electrochemical performance due to its enhanced electronic conductivity and ion diffusion rate., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

With the proposal of carbon peaking and carbon neutrality goals, clean energy storage is attracting more and more attentions. In view of the lack of lithium resource in our earth, sodium-ion batteries are considered as the emerging and promising next-generation energy storage devices. Appropriate high-performance anode materials play a vital role in the development of sodium-ion batteries. Here, a core-shell hollow Ni-Co-P nanopolyhedron interconnected by oxygen defect TiO 2 (Ni-Co-P@TiO 2- x ) is reported, which is synthesized by ion etching-hydrolysis and subsequent phosphatization/hydrogenation treatment using ZIF-67 as template and hybrid carbon source. The achieved Ni-Co-P@TiO 2- x material has several distinct advantages including hollow core-shell structure, flexible conductive carbon matrix, stable electroactive coating layer, and efficient pseudocapacitive behavior, resulting in high reversible capacities, remarkable rate capability and excellent cycle stability. The synergetic battery-capacitor characteristic of Ni-Co-P@TiO 2- x material makes it become a promising anode for sodium-ion batteries., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Rechargeable lithium-sulfur (Li-S) batteries with environmental friendliness, low price, high specific capacity and energy density could be promising alternatives to a larger scope of energy storage in the near future. However, the practical application is impeded by the intrinsic insulation of sulfur and the fatal shuttle effect during the (dis)charging process. Herein, we report a strategy to address the drawbacks of Li-S batteries by inserting an interwoven carbon nanotubes/cerium dioxide electrocatalyst interlayer material (CNTs@CeO 2 ) between the sulfur cathode and the separator. In the CNTs@CeO 2 composite, the conductive network interwoven by CNTs facilitates electron transportation, and the abundant active sites in CeO 2 cavities ensuring the adsorption-catalytic conversion of lithium polysulfides as well as the hollow structure of CeO 2 is conducive to rapid electrolyte penetration and lithium ion migration. Benefiting from such multifunction, the battery with a CNTs@CeO 2 interlayer exhibits superior rate performance, delivering a high discharge specific capacity of 1040.6 mAh g -1 at 0.2C and 652.5 mAh g -1 at 4C, respectively. Moreover, the battery shows excellent cycling stability with a capacity decay rate of 0.064% per cycle at 1C over 1000 cycles. These promising results demonstrate the potential application of CeO 2 -based electrocatalysts for high energy density Li-S batteries., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The inferior conductivity and infamous "shuttle effect" of lithium-sulfur (Li-S) batteries lead to low sulfur utilization and undesired cycle stability, which both seriously affect their practical application. Here, a multifunctional nanofiber material based on cerium dioxide spheres embedded inside nitrogen-doped carbon fibers (denoted as NCF@CeO 2 ) fabricated by electrospinning technology is used as an interlayer for high-performance Li-S batteries. The nitrogen-doped carbon fiber skeleton matrix provides a through-conducting grid to accelerate electron transfer at the interface of the nitrogen-doped carbon and the CeO 2 , and the large specific surface area guarantees a sufficient interfacial fast-redox reaction for sulfur species. CeO 2 with a hollow structure provides strong physicochemical adsorption of lithium polysulfides (LiPSs) to weaken the migration behavior, and abundant oxygen defects as catalytic active sites are conducive to lithium sulfide conversion. The "sphere in fiber" construction minimizes the direct contact between the catalyst and electrolyte, effectively avoiding side reactions. Based on the multiple functions of nitrogen-doped carbon fibers and CeO 2 , Li-S batteries with NCF@CeO 2 interlayers exhibit superior electrochemical performances, including a high discharge specific capacity of 1072.9 mAh g -1 at 0.2 C and a low capacity decay rate of only 0.063% per cycle after 1000 cycles. Moreover, the mechanisms of LiPSs adsorption-conversion and the quantification of the catalytic ability are elaborately clarified., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The rational design of an excellent architecture for active materials combined with carbon matrix is of particular importanceto obtain flexible electrode material with high electrochemical properties. Well-designed nanofibers possess unique 3D network structure, which can significantly improve the electron/ion transportation and supplies sufficient active sites for Li + /Na + insertion. Electrospinning-carbonization technology is a popular strategy to prepare nanofibers with active material embedded in carbon. It is found that the architecture of nanofibers tended to be wrecked and destroyed during the carbonization process without pre-oxidation treatment. In this study, we prepared Na 2 MnPO 4 F particles embedded in carbon nanofibers (Na 2 MnPO 4 F/C) using PVP as carbon source and investigated the strengthen mechanism of pre-oxidation on their architecture. The experiment and simulation results demonstrate that, without pre-oxidation, the main chain of PVP is severely ruptured during the carbonization procedure, consequently leads to fractured architecture of Na 2 MnPO 4 F/C nanofibers. In contrast, with pre-oxidation treatment, a long-chain and heat-resistance structured carbon matrix formed, and Na 2 MnPO 4 F/C nanofibers with stable architecture and improved electrochemical performance can be achieved. This study demonstrates a promising guide to construct carbon based nanofiber electrodes with stable architecture and high electrochemical performance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Lithium-sulfur batteries have attracted numerous attentions owing to their high theory discharge specific capacity and energy density. However, sulfur cathode usually suffers from poor cycle stability and slow reaction kinetics, caused by its poor conductivity, excessive volume changes during charge/discharge processes, complex sulfur species conversion reaction and the dissolution of polysulfide intermediates. Here, we present a free-standing framework of Mn 3 O 4 nanoparticles combine with polypyrrole (PPy) nanotubes as host materials for lithium-sulfur batteries to overcome these issues. In this construction, PPy nanotubes serve as the excellent container of sulfur and physical barrier for the excessive volume expansion of sulfur during electrochemical reaction processes, and the nanotubes also provide an efficient conductive network for the rapid transmission of electrons and ions, while Mn 3 O 4 nanoparticles facilitate trapping lithium polysulfides. The coordination of PPy nanotubes and Mn 3 O 4 effectively alleviate the shuttle effect as well as enhance the utilization of sulfur. The obtained PPy@Mn 3 O 4 -S sample shows high capacities of 1419.9 and 925.5 mAh g -1 at 0.1 C and 1 C rate, respectively, and exhibits a low capacity fading rate of 0.062% per cycle for 800 cycles at 1 C rate. This work provides a new and effective way for the design of lithium-sulfur batteries with both high rate performance and long cycle stability., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)