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An ultrasonic irradiation method was applied to the sol–gel synthesis of silver vanadium oxides (SVO). Transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA) were conducted to research the ultrasonically accelerated reaction between V2O5 gel and Ag2O powder. Galvanostatic discharge experiments showed that the as prepared cathode active material of Ag2V4O11 and Ag1.2V3O8 have better electrochemical properties than those synthesized by conventional solid state method. [Copyright &y& Elsevier]

The development of high‐performance cathode materials for next‐generation lithium‐ion batteries (LIBs) is urgently needed. Among the potential cathode candidates, ternary layer oxide LiNi1/3Co1/3Mn1/3O2 (LNCM) has attracted considerable attention due to its high voltage discharge, large theoretical specific capacity, stable chemical structure and low cost. However, Li+/Ni2+ cation mixing and low conductivity have resulted in poor long‐term cyclability, voltage drop and capacity degradation during high‐rate charging. To address these issues, a sol‐gel technique together with an annealing treatment was used to prepare LNCM with well‐defined structure and good morphology. The material obtained by heating the LNCM precursor at 850 °C for 12 h (LNCM‐850/12) exhibited an initial discharge specific capacity of 217.9 mAh g−1 at 0.2 C and maintained a high reversible capacity of 116.1 mAh g−1 after 200 cycles. The LNCM‐850/12 electrode also demonstrated superior rate capacity and exceptional cycling stability due to its well‐defined structure, low Li+/Ni2+ cation mixing and good morphology. These characteristics improve the electrical/ionic conductivity, reduce the charge transfer resistance and shorten the Li+ diffusion distance, ultimately accelerating the Li+ insertion and extraction. Overall, the careful control of calcination time in LNCM synthesis provides valuable insights for the development of advanced cathodes for LIBs. [ABSTRACT FROM AUTHOR]

A new flexible aromatic polymer sulfonated polybenzothiazole (sPBT-SE) with sulphone and ether units is reported as an advanced cathode material for storing Na+, which delivers a high discharge capacity of 103 mA h g−1 after 350 cycles at 30 mA g−1. [ABSTRACT FROM AUTHOR]

• 1. For the first time, the Li 7 [V 15 O 36 (CO 3)] and γ -LiV 2 O 5 as host materials to store Zn2+. • 2. A larger voltage window (0.2–1.9 V) than most other aqueous zinc ion batteries. • 3. The energy density and power density of the Li 7 [V 15 O 36 (CO 3)] and the γ -LiV 2 O 5 is high. • 4. The Zn2+ storage mechanisms of the Li 7 [V 15 O 36 (CO 3)] and the γ -LiV 2 O 5 are proved. Recently, many reports have been published about polyoxovanadates (POVs) with multiple electrons redox activity for energy storage. However, they are easily transformed into solid-state oxides after calcination. We noted that although dehydrated Li 7 [V 15 O 36 (CO 3)] (Li 7 V 15) exhibited a high capacity for lithium-ion batteries (LIBs), it was reported that the electrochemical behavior of the dehydrated sample same as γ -LiV 2 O 5 (γ -LVO) which prepared by annealing the cluster and undehydrated Li 7 V 15 was not redox-active. Interestingly, we were surprised to find that undehydrated Li 7 V 15 and its derivative γ -LVO showed better electrochemical performance than LIBs when first proposed as the cathode to store Zn2+. Both Li 7 V 15 and γ -LVO electrodes provided excellent rate performance and satisfied cyclability (135.0 and 214.1 mAh g−1 at 3 A g−1 after 1000 cycles, respectively). The fast kinetics of Li 7 V 15 and γ -LVO were verified by pseudocapacitive analysis, GITT and EIS tests. Moreover, the Zn2+ storage mechanism and redox behavior of Li 7 V 15 and γ -LVO were examined by ex-situ measurements. First-principles calculations revealed that the Zn2+ was chemisorbed on the clusters and physisorbed between the clusters. This work enriches the POVs cathode chemistry in aqueous energy storage. [ABSTRACT FROM AUTHOR]

Recycling of spent lithium-ion batteries (LIBs) has emerged as an inevitable trend in promoting environmental sustainability and resource conservation. Lithium iron phosphate (LiFePO 4 or LFP) battery, renowned for its unique stability and favorable price, has been the predominant focus for lithium-ion battery manufacturers, consequently resulting in a surge in the number of spent LIBs. In view of the failure mechanism, the direct regeneration technology presents a potential strategy for the closed-loop recycling of LFP. The aim is to retain the high added value and revitalize optimal state of the spent cathode materials through a non-destructive process that maximizes efficiency and ensures desirable profits. Hence, the existing technical challenges and recent progress in the separation pretreatment are reviewed and summarized. Subsequently, the current direct regeneration methods and advanced upcycling techniques for spent LFP cathode are outlined, along with an appraisal of their respective advantages and disadvantage. Specifically, a comprehensive analysis of environmental and economic benefits derived from three presentative examples is highlighted compared to traditional metallurgy process. The review also aims to provide an overview on direct regeneration of spent LFP cathode, making it favorable for further industry adoption. • Potential strategy for low-value LFP via direct regeneration is presented. • Challenges and recent progress in separation pretreatment are discussed. • Recent advancements and advanced upcycling for spent LFP cathode are summarized. • The merits and drawbacks of each approach are assessed. • The comprehensive analysis of environmental and economic benefits is emphasized. [ABSTRACT FROM AUTHOR]

The rapid depletion of lithium resources and the increasing demand for electrical energy storage have stimulated the pursuit of emerging electrochemical energy storage. Aqueous zinc ion batteries (ZIBs) are highly sought after for their low cost, high safety, and increased environmental compatibility. However, the search for suitable cathode materials is still tricky for a wide range of researchers. Vanadium oxides (VxOy), with their abundant vanadium valence, easily deformable V−O polyhedrons, and tunable chemical compositions, are of significant advantage in developing emerging materials. This work provides a detailed review of different VxOy for the application in aqueous ZIBs. The current problems and optimization strategies of VxOy cathode materials are systematically discussed. Finally, the current challenges and possible directions for future research of VxOy cathode materials in aqueous ZIBs are presented. [ABSTRACT FROM AUTHOR]

• Five types of Na x MnO 2+ z are prepared by the rheological phase reaction method. • Na x MnO 2+ z materials with different sodium contents exhibit rod-shaped, rod-sheet mixed, and sheet-like morphology. • Na 0.44 MnO 2 exhibits excellent cyclic stability and high rate capability. • Na 0.44 MnO 2 exhibits a high contribution rate of pseudo capacitance. • In situ XRD testing showed the reversible phase transition of NMO-0.44 material during charge and discharge processes. Sodium-ion batteries (SIBs) experience a re-emerging academic interest due to their low cost and high abundance as compared with lithium-ion batteries (LIBs) which have considerably increased the worldwide cost due to high actual demand. At present, a representative amount of cathode/anode SIBs materials are developed; facilitating the Na+ insertion mechanism understanding and the respective influence on structure change, which in most cases it is directly related to sodium concentration. In this work, the rheological phase reaction method is used to synthesize five types of Na x MnO 2+ z materials with different sodium content and use them as the cathode materials for SIBs. The physical properties and electrochemical performances of Na x MnO 2+ z materials with different concentrations are investigated by physical characterization means, electrochemical tests, and a series of computational methods. Inductively coupled plasma optical emission spectrometer (ICP-OES) test results indicate that the right materials have been successfully synthesized, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements show how the changes in sodium concentration significantly impact the morphology of the formed particles. In the results of electrochemical investigations, NMO-0.67 material has a high initial specific discharge capacity, but NMO-0.44 material has a reasonable cycling stability, keeping its discharge specific capacity of 83.06 mAh/g after 1000 cycles at a high current density of 360 mA g−1. Galvanostatic intermittent titration technique (GITT) testing and pseudo-capacitance analyses are also used to disclose the dynamic properties of NMO-0.44 material. In conclusion, the rheological phase reaction approach may be used to successfully create Na x MnO 2+ z materials, and variations in sodium content have a big impact on their structure and electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • This work summarizes the application of vanadium oxides as aqueous ZIBs cathodes. • Electrochemical properties and energy storage behavior of different types of vanadium oxide cathodes. • Current challenges and expected development foregrounds of vanadium oxides cathodes in aqueous ZIBs are proposed. The rapid development of science and technology, as well as the trend toward intelligence, has resulted in a surge in the demand for excellent energy storage devices for smart devices. At present, the most widely used lithium ion batteries have limited further development because of their high cost and various disadvantages of electrolytes (flammable and toxic). In spite of the low costs and safety of aqueous zinc-ion batteries, the high radius of the zinc ions and strong electrostatic interactions make cathode materials without excellent performance difficult to find. Various oxidation states, structural diversity, excellent multiplicity performance and high capacity have attracted researchers to vanadium-based oxides in recent years. However, vanadium-based oxides have disadvantages such as poor structural stability and low electrical conductivity, so this paper summarizes the progress of research on vanadium oxide cathode materials such as V 2 O 5 , VO 2 , V 2 O 3 , etc., and provides an outlook on future development directions. [ABSTRACT FROM AUTHOR]

Summary: The carbon layer acting as a conductive medium is beneficial to overcoming the comparatively inferior electronic conductivity of Na3V2(PO4)3. Based on this, Na3V2(PO4)3/C composites with diverse ratios of citric acid are synthetized via rheological phase reaction way in this work. The consequences display that the Na3V2(PO4)3/C‐1.5 composite brings a higher initial discharge capacity of 113.2 mAh g−1 at a current rate of 1 C with coulombic efficiency above 99% during all cycles. The discharge capacity retains at 117.6 mAh g−1 at the 100th cycle. Even at the high current densities of 5 C and 10 C, the composite also shows superior cycling performance with negligible capacity fading. Its discharge capacities decline from 97 to 92.6 mAh g−1 at 5 C and from 85.3 to 83.7 mAh g−1 at 10 C. These remarkable outcomes arise from its preferable morphology with suitable carbon coating because both excess and skimpy carbon seriously affect the microstructure and electrochemical properties of Na3V2(PO4)3/C composites. [ABSTRACT FROM AUTHOR]

[Display omitted] Vanadate, as an advanced inorganic material, has been a major object of scientific research due to its flexible valence states and the multi-electron transfer mechanism of vanadium. This review concentrates on the application of vanadates in aqueous ZIBs, which facilitates researchers to understand the latest research progress on vanadate-based cathodes for ZIBs. Furthermore, the limitations of current vanadate-type cathodes are pointed out and the perspectives for their application in emerging energy storage areas are presented. • This work comprehensively summarizes the application of vanadates as aqueous ZIBs cathodes. • Electrochemical performance and energy storage behavior of vanadates cathodes are further discussed. • Current challenges and expected development foregrounds of vanadates cathodes in aqueous ZIBs are proposed. With the increasing pursuit of electronic products with high specific energy and outstanding environmental compatibility, developing advanced new power sources is urgent. As the representative of new energy, rechargeable aqueous zinc ion batteries (ZIBs) have gained much focus recently in the field of energy storage owing to their advantages of safety, cost-effectiveness, and environmental sustainability. Nevertheless, the progression of suitable Zn-storage cathode materials remains a huge challenge, limited by commercial requirements. Vanadate, as an advanced inorganic material, has been a major object of scientific research due to its flexible valence states and the multi-electron transfer mechanism of vanadium. Undeniably, understanding the electrochemical Zn-storage properties and mechanisms of this class of materials plays a crucial role in facilitating their development. However, there is a paucity of reviews on vanadates as cathodes for aqueous ZIBs. This review concentrates on the application of vanadates in aqueous ZIBs, which facilitates researchers to understand the latest research progress on vanadate-based cathodes for ZIBs. Finally, the limitations of current vanadate-type cathodes are pointed out and the perspectives for their application in emerging energy storage areas are presented. [ABSTRACT FROM AUTHOR]

Summary: Polyaniline‐derived N‐doped carbon‐composited Na3V2(PO4)3 (NVP@NC) are synthesized by a rheological phase reaction followed by calcination. The NVP@NC composite displays improved cycling and rate properties. Its discharge capacity remains 118.7 mAh g−1 at the 400th cycle at 0.3 C. It also obtains invertible capacities of 93.7 and 91.1 mAh g−1 at 5 and 10 C after 1000 cycles, with capacity retention rates of 92.7% and 98.4%, respectively. These enhanced results due to the N‐doped carbon layer (NC), which restrains the expansion and deformation of the crystal structure, reduce the transport length of sodium ion and electrons and improves the electroconductibility of NVP. [ABSTRACT FROM AUTHOR]

Ethylene glycol‐assisted sol‐gel method is employed for preparing LiNi1/3Co1/3Mn1/3O2 used as cathode material in lithium‐ion batteries. The prepared material has higher c/a value and lower cationic mixing degree of Li+/Ni2+, illuminating a more orderly structure, smaller particle size and more regular particle shape, which shorten the diffusion length for Li+ ions and allow the rapid kinetics of Li+ ions diffusion. Sure enough, the as‐prepared LiNi1/3Co1/3Mn1/3O2 material displays the first discharge capacity of 208 mAh g−1 and keeps 133 mAh g−1 after 200 cycles between 2.5 and 4.5 V at 0.2 C. In addition, it demonstrates excellent rate capacity of 143 mAh g−1 at 2 C. The results show that LiNi1/3Co1/3Mn1/3O2 prepared by this method has high discharge capacity, admirable rate capability and exceptional cycle stability, which provides significant insights into the synthesis of other layered oxides as cathode materials for lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Summary: Graphene‐wrapped poly 2,5‐dihydroxy‐1,4‐benzoquinone‐3,6‐methylene (PDBM) nanocomposites with three‐dimensional nanoflower structures have been successfully prepared through the ultrasonic exfoliation and reassembly process in methanol. Compact distribution of graphene into the nanocomposite has established a three‐dimensional conductive network, which contributes to improved properties on discharge capacity and cycle performance. Composite with 20 wt% graphene was proved the best ratio when used in sodium‐ion batteries. Its initial discharge capacity can achieve 210 at 30 mA g−1. After 100 cycles, the capacity is stable at 121 mAh g−1. The composite featuring highly conductive channels and multidimensional electron transport pathway is synthesized by an easy ultrasonic way, which may be applied in large scales for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

• NVO are prepared using Pluronic-F127 as structure-directing agent. • NVO show unique nanorod structures. • NVO calcined at 400 °C shows high capacity and high rate capability. • Kinetics analysis verifies the pseudocapacitive behavior of R-400. • Outstanding performance is attributed to low resistance and fast Na+ ions intercalation/deintercalation kinetics. In this study, NaV 3 O 8 nanorods are successfully prepared using nonionic surface-active agents Pluronic-F127 as structure-directing agent. The as-prepared NaV 3 O 8 nanorods calcinated at different temperatures are characterized by various techniques, including X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy. The NaV 3 O 8 calcinated at 400 °C for 20 h shows appropriate sizes and uniform morphologies of the nanorods, 4–7 μm in length and 0.2–0.5 μm in diameter. The NaV 3 O 8 nanorods as cathode materials for Na-ion batteries deliver high discharge capacity reaching up 110.4 mAh g−1 at current density of 120 mA g−1, as well as long lifespan by maintaining capacity of 162.1 mAh g−1 after 500 charge-discharge cycles. Also, a high reversible capacity of 83.9 mAh g−1 can be retained after 500 cycles at high rate of 2 A g−1. The obtained outstanding electrochemical performances are associated with the unique micro-nano structures, which does not only facilitate transport of Na+ ion, but also resist erosion from electrolytes. Overall, the results suggest the promise of NaV 3 O 8 nanorods as cathode materials for high capacity, high power and long lifespan Na-ion batteries. This work may open an innovative route to discover diverse electrode materials with nanostructure for energy storage system. [ABSTRACT FROM AUTHOR]

Abstract A series of LiNi 1/3 Co 1/3 Mn 1/3 O 2 /polytriphenylamine composites were successfully synthesized by ultrasound dispersion method. LiNi 1/3 Co 1/3 Mn 1/3 O 2 /polytriphenylamine (5.0 wt%) composite with small and homogeneous particle size exhibited excellent electrochemical performance, which delivered an initial discharge capacity of 223.7 mAh g−1 with a capacity retention of 84.39% after 100 cycles in the voltage range of 2.5–4.5 V and at a current density of 0.2C. Moreover, an excellent specific discharge capacity of 127.3 mAh g−1 at a current density 5C indicates a superior rate performance of the LiNi 1/3 Co 1/3 Mn 1/3 O 2 /polytriphenylamine (5.0 wt%) composite. The good electrochemical performances of the composite can be attributed to the introduction of polytriphenylamine, which increased electrical conductivity, decreased charge transfer resistance and increased Li+ ion diffusion ability. These noteworthy results demonstrated that LiNi 1/3 Co 1/3 Mn 1/3 O 2 /polytriphenylamine composites might be potential cathode materials for lithium ion batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

LiV 3 O 8 /10 wt% poly(1,5-diaminoanthraquinone) composite was prepared by a in situ chemical oxidative polymerization process and applied as cathode material for rechargeable lithium batteries. Due to the introduction of poly(1,5-diaminoanthraquinone) and electrochemical synergistic effect, the composite demonstrated better rate capabilities and cycling performances compared to the bare LiV 3 O 8 sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Na 2 THBQ were combined with CDs as cathode materials in SIBs for the first time. • o -Na 2 THBQ/CDs-2 performed good cycling stability and rate performance. • The mechanism of o -Na 2 THBQ/CDs-2 was explored by ex-situ tests. • The sodium ion diffusion coefficient of the materials was tested by GITT. Organic compounds are considered auspicious due to their widespread presence in nature, low cost, and sustainability. However, the inherent drawbacks of these organics' compounds, like low-conductivity and high-solubility, restrict their large-scale application. To solve these problems, we innovatively combined carbon quantum dots (CDs) with active substances (tetrahydroxybenzoquinone ortho -disodium salt (o -Na 2 THBQ)) at different mass ratios. The optimized o -Na 2 THBQ/CDs-2 (the mass ratio of o -Na 2 THBQ to CDs is 10:2) exhibited excellent electrochemical performance, the first-cycle discharge specific capacity was 410 mAh g−1 and maintained 182 mAh g−1 after 500 cycles, and the Coulombic efficiency was nearly 100 %. After 1300 cycles, the o -Na 2 THBQ/CDs-2 composite demonstrated a high specific capacity of 63 mAh g−1 at 500 mA g−1. This work provides a reference to design an optimal composite ratio of carbon dots (CDs) and organics to fabricate cathode materials for high-performance sodium-ion batteries. [ABSTRACT FROM AUTHOR]

For cost and safety reasons, aqueous batteries are suitable for large-scale energy storage. Among all aqueous batteries, the rechargeable aqueous zinc ion batteries (ZIBs) are promising choices owing to the low equilibrium potential and high volumetric capacity of zinc. However, its development is also severely hindered by the limited available cathode materials, which generally display poor cycling capabilities. As one of the most investigated POVs (polyvanadates) today, (V 10 O 28)6− has been demonstrated to be feasible in the energy storage rely on the well-defined structure and fascinating material activity. Herein, we propose a polyvanadate-Na 6 V 10 O 28 with (V 10 O 28)6− anion as a support structure and serve it for the first time as aqueous ZIBs cathode. The high stability of the (V 10 O 28)6− cluster permits the material to tolerate the reversible (de)insertion of Zn2+. As a result, the Na 6 V 10 O 28 cathode delivers a high capacity of 279.5 mAh g−1 and extraordinary lifespan over 2000 cycles. Furthermore, the pseudocapacitance analysis and GITT test reveal the pseudocapacitance behavior and high Zn2+ diffusion coefficient (10−10 cm2 s−1) of the Na 6 V 10 O 28 /Zn cell, respectively. Not only that, ex-situ XRD, XPS, and TEM are also employed to analyze the storage mechanism of Zn2+, indicating the synergistic Zn-storage capacity of Na 6 V 10 O 28 and irreversible products. Overall, this work presents new insights into the application of Na 6 V 10 O 28 in aqueous ZIBs and also demonstrates the competitive potential of POVs for energy storage. [Display omitted] • For the first time, the Na 6 V 10 O 28 cathode is applied for aqueous zinc ion batteries. • Na 6 V 10 O 28 delivers excellent cycling stability and the high specific discharge capacity. • The Zn2+ ion diffusion rate of Na 6 V 10 O 28 is as high as 10−10 cm2 s−1. • The high reversibility of Zn2+ insertion/extraction in Na 6 V 10 O 28 is demonstrated by ex-situ XRD. For cost and safety reasons, aqueous batteries are suitable for large-scale energy storage. Among all aqueous batteries, rechargeable aqueous zinc-ion batteries (ZIBs) are promising choices owing to the low equilibrium potential and high volumetric capacity of zinc. However, its development is also severely hindered by the limited available cathode materials, which generally display poor cycling capabilities. As one of the most investigated POVs (polyvanadates) today, (V 10 O 28)6− has been demonstrated to be feasible in energy storage rely on the well-defined structure and fascinating material activity. Herein, we propose a polyvanadate-Na 6 V 10 O 28 with (V 10 O 28)6− anion as a support structure and serve it for the first time as an aqueous ZIBs cathode. The high stability of the (V 10 O 28)6− cluster permits the material to tolerate the reversible (de)insertion of Zn2+. As a result, the Na 6 V 10 O 28 cathode delivers a high capacity of 279.5 mAh g−1 after activation and an extraordinary lifespan over 2000 cycles. Furthermore, the pseudocapacitance analysis and GITT test reveal the pseudocapacitance behavior and high Zn2+ diffusion coefficient (10−10 cm2 s−1) of the Na 6 V 10 O 28 /Zn cell, respectively. Not only that, ex-situ XRD, XPS, and TEM are also employed to analyze the storage mechanism of Zn2+, indicating the synergistic zinc-storage capacity of Na 6 V 10 O 28 and irreversible products. Overall, this work presents new insights into the application of Na 6 V 10 O 28 in aqueous ZIBs and also demonstrates the competitive potential of POVs for energy storage. [ABSTRACT FROM AUTHOR]

The aqueous zinc-ion batteries (ZIBs) field has witnessed a tremendous advancement in the exploration of materials that can combine high energy density and short charge times. Nevertheless, these materials are primarily focused on manganese-based or vanadium-based oxides, and there are fewer reports on new materials. Herein, we proposed a new ZIBs cathode material based on polyoxovanadates (POVs) type K 4 Na 2 V 10 O 28 (KNVO). It demonstrated the advantages of POVs, which could undergo multi-electron redox processes at each V center. The reversible capacity was maintained at 152.3 mAh g−1 after 100 cycles at 0.1 A g−1, and the capacity retention was close to 100% after 1000 cycles at 1 A g−1. Additionally, the kinetic properties of the KNVO/Zn cell were investigated by Trasatti research, pseudocapacitance analysis and GITT test, respectively, manifesting a strong capacitive behavior as well as a high Zn2+ diffusion coefficient (order of 10−10 cm2 s−1). Not only that, but we also analyzed the relevant characteristic parameters of EIS in-depth, aiming to systematically probe the changes in electrochemical behavior before and after cycling. The synthesis and investigation of KNVO cathode materials may provide directions for the development of electrode materials for a rising generation of aqueous ZIBs. [ABSTRACT FROM AUTHOR]

• NVO material doped by niobium ion (Nb5+) was successfully prepared by the rheological phase method. • Nb-doping lead to an expansion of the lattice volume and increase the intrinsic conductivity. • NaNb 0.018 V 2.982 O 8 demonstrates high-rate capability and long-term cyclability. • Pseudocapacitive behavior of Nb-doped NVO is confirmed by kinetics analysis. In this work, NaNb 0.018 V 2.982 O 8 (NVO-0.018Nb) composite was served as the cathode of sodium-ion batteries (SIBs) to deliver a superior Na-storage capacity of 187 mA h g−1 at the current density of 1 C and voltage range of 1.5–4.0 V, and favorable energy density (419.3 Wh kg−1). Electrochemical impedance spectroscopy (EIS) measurements displayed decreased charge transfer resistance in the NVO-0.018Nb composite. The detailed kinetic analysis revealed enhanced surface-controlled behaviors, leading to improved sodium-storage capability. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses demonstrated that NVO-0.018Nb composite exhibited unique structure with significantly enhanced structural stability during fast cycling. In sum, the proposed method looks promising for the design of future advanced electrode materials of SIBs. [ABSTRACT FROM AUTHOR]

The development of lithium-ion batteries is hindered by the lack of appropriate low-cost cathode materials with high performance. Here, the preparation of Cu-coated Li 3 V 2 (PO 4) 3 /C (x % Cu-LVPC) composites is reported via a chemical precipitation and self-reduction method. With an optimized Cu coating content of 2.0 wt%, the 2.0% Cu-LVPC composite displays the best electrochemical properties. The initial discharge capacity of 2.0% Cu-LVPC is 175 mA h g−1 at 0.15 C (30 mA g−1) in the voltage range from 3.0 to 4.8 V and the capacity retention is 86.3% after 50 cycles, whereas pristine LVPC has an initial capacity of 163 mA h g−1 and retains 82.2% of the capacity after 50 cycles. Moreover, the rate capacity of 2.0% Cu-LVPC is also increased under different current densities and 2.0% Cu-LVPC exhibits excellent long-term cycling performance of 89 mA h g−1 after 1000 cycles at 10 C. The enhanced electrochemical properties are attributed to the uniform coating of the metal conductor Cu on the LVPC surface, which is conducive to electron transfer and extraction/insertion of Li+ ions. • Cu-coated Li 3 V 2 (PO 4) 3 /C (LVPC) was prepared via a chemical precipitation and self-reduction method. • The 2.0% Cu-coated LVPC composite exhibits significantly improved electrochemical performance. • Cu coating can effectively increase the conductivity of LVPC. • Cu coating on the surface of LVPC can reduce the polarization. [ABSTRACT FROM AUTHOR]

The impacts of Cu substitution upon the cycling stability of Na x MO 2 (M = Fe, Mn) cathodes are systematically studied. Evidenced by CuO segregation and XPS analysis, the average valence of Mn can hardly reach +4, possibly owing to the production of Mn(II). It is proposed that, Cu substitution can efficiently enhance the cycling stability by reducing the content of Mn(III) and suppressing the electrochemical activities of Mn4+/3+ redox couple. • Cycling stability of Na x MO 2 (M = Cu, Fe, Mn) cathodes are systematically studied. • CuO segregation is evidenced to be associated with the limited valent state of Mn. • Adding Cu2+ actually lower Mn valence by decreasing Mn(III) and generating Mn(II). • Cu2+-substitution may enhance the cycling stability mainly by suppressing Mn(III). Adding Cu2+ has substantially boosted the practical potentiality of Fe/Mn-based layered cathodes for sodium ion batteries (SIBs) owing to the enhanced stabilities, which were previously ascribed to the raised valence of Mn. Herein, the roles of Cu2+ are verified by investigating Cu2+-substituted materials with the stoichiometry of Na 0.5+x Cu x Fe 0.5-x Mn(IV) 0.5 O 2. Surprisingly, it is found that Mn valence can hardly reach the expected value (IV) even by adjusting Cu2+ content. For the first time, the separation of CuO, which has been previously detected but rarely explained, is ascribed to the restrained chemical states of Mn. Detailed analyses show that, Mn(II) is generated while Mn(III) is decreased in pace of Cu2+ substitution, actually lowering down the oxidation states of Mn. Moreover, Mn4+/3+ redox can be efficiently restricted by importing Cu2+. Albeit the loss of capacity, the cycling stability is greatly enhanced, achieving a high capacity retention of 92.3% after 200 cycles within 4.2–2.5 V. Therefore, the suppression of Jahn-Teller Mn(III) should be intrinsically responsible for the superior cycling stability after Cu2+ substitution. These findings may present a new sight to probe the roles of Cu in layered Na x MO 2 system for the design of advanced cathodes for SIBs. [ABSTRACT FROM AUTHOR]

• LZO-LVPC composites were prepared by a simple mechanical ball-milling method. • 4.0 wt% LZO-LVPC exhibit a significant improved electrochemical performance. • LZO compensate for the transfer of Li+ between the cathode material and the electrolyte. • LZO protect the cathode material from side reactions with electrolyte. A simple and efficient synthetic route was developed to obtain composites by mechanically ball-milling Li 2 ZrO 3 (LZO) with Li 3 V 2 (PO 4) 3 /C (LVPC). LZO improves the ionic conductivity of LVPC, compensates for the transfer of Li+ between the LVPC and the electrolyte, reduces the impedance of LVPC, and protects LVPC from side reactions caused by direct contact with the electrolyte. The composite consisting of 4.0 wt% of LZO exhibited a considerable electrochemical performance. The 1st discharge capacity reached 192 mAh g−1 at 30 mA g−1 between 3.0 and 4.8 V, and remained at 153 mAh g−1 after 50 cycles. The EIS analysis showed that the charge transfer and diffusion of Li+ in the LZO-LVPC composites were more favorable than those of pristine LVPC. The synthetic method proposed in this work is simple and efficient, which is convenient for large-scale production. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have garnered significant academic and industrial focus because of their excellent merits, like high voltage, high energy density, excellent cyclic performance, no memory effect and environment-friendly nature. So far, the electrochemical properties of LIBs are restricted by the capacity of cathode materials and various novel compositions and designed architectures have been proposed to enhance the energy density and cyclic performance of LIBs cathodes. Recently, lithium nickel cobalt manganese oxides have attracted extensive research interest owing to the united advantages of LiCoO 2 , LiNiO 2 and LiMnO 2. Herein, we have reviewed the recent developments of LiNi 1/3 Co 1/3 Mn 1/3 O 2 from the viewpoint of synthesis processes and structural designs. The electrochemical properties of LiNi 1/3 Co 1/3 Mn 1/3 O 2 depend on particle size, morphology, ion doping and surface coating of the as-prepared cathode powder. The present article summarizes the recent developments and provides an insight into the future roadmap for the realization of high energy density LIBs. • Main synthesis methods of NCM cathodes are summarized and analyzed. • Partial ionic substitution enhances the structural stability and electronic conductivity. • Surface coating can prevent the side reactions, improved the electronic and ion migration rate. • Composite structure can increase the structure constancy and the electronic conductivity. [ABSTRACT FROM AUTHOR]

• Substitution ions can affect the lattice constants, grain size and morphology. • Doping sites include Li, V, O sites, cation and anion co-doping, interlayer doping. • Ions-doping improves the diffusion coefficient and the electronic conductivity. • Ions-doping is an important trend for the long-term development of Li 1+ x V 3 O 8. Compared with other materials, monoclinic Li 1+ x V 3 O 8 as the promising cathode includes many strong points, such as high theoretical capacity, abundant raw materials, safety characteristic and low environmental impact. However, the primary problems facing the development of Li 1+ x V 3 O 8 for energy storage devices are poor cycling performance, low rate capability and short service life. Recently, many researches have taken various measures to overcome these shortcomings. In this mini-review, we summarized the recent developments of Li 1+ x V 3 O 8 and focus on the improving of Li 1+ x V 3 O 8 by ions-doping, which is deemed to a significant manner to improve the electrochemical performances of Li 1+ x V 3 O 8. [ABSTRACT FROM AUTHOR]