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Polyanionic cathode materials are increasingly used in research because of their good cycling performance, high theoretical capacity, and high operating voltage. However, it exhibits poor performance due to its structure, which prevents it from reaching its full theoretical capacity. In this study, carbon‐coated Li6V3(PO4)5@C cathode materials are constructed under Li3V2(PO4)3 research conditions using the sol–gel process and anhydrous citric acid as the carbon source. Several boron doping concentrations are investigated to create Li6V3(PO4)5@BC cathode materials. The electrochemical measurements demonstrate that during the first cycle, at a current density of 0.5 C and a B doping quantity of 2 wt%, the specific discharge capacity of Li6V3(PO4)5@BC reaches 167.43 mAh g−1. The steady discharge specific capacity following 80 cycles of constant‐current charging and discharging is 136.84 mAh g−1. Li6V3(PO4)5@BC‐2 has a specific discharge capacity of 131.1 mAh g−1 at 2 C. The material's electrochemical performance greatly improves following the right quantity of B doping, which is primarily attributed to the increase in carbon layer defects brought on by B's entrance. This can increase the rate of lithium‐ion migration and hold more lithium ions. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) work similarly to lithium‐ion batteries, but they cost less and are safer. However, the battery has some shortcomings, such as low energy density and poor stability, which hinder its development and application. The development of electrode materials with low cost and high‐performance characteristics is a hot and difficult point in the research of SIBs. In this paper, the existing sodium ion cathode and anode materials are systematically reviewed. Firstly, the electrochemical structures and properties of various cathode and anode materials were introduced, and the limitations of cathode and anode materials of SIBs were analyzed. Based this, the current modification methods were summarized, such as surface coating of materials, doping of heteroatoms and metal elements to improve the electrochemical performance. In this paper, the research progress and modification measures of SIBs are summarized and prospected. It is helpful to further improve its comprehensive performance and lay a foundation for the future application of cathode and anode materials for SIBs. [ABSTRACT FROM AUTHOR]

A facile and highly efficient method was proposed for the separation and regeneration of LiFePO4 (LFP) cathode materials from spent lithium‐ion batteries (LIBs). The optimal separation conditions involved immersing the spent LFP materials in NaOH (0.5 mol/L) solutions at a temperature of 90 °C, with a solid‐liquid ratio of 30 g/L under stirring of 500 rpm. The high separation effect can be attributed to the synergistic action of several factors at the interface. Furthermore, the structure, composition, morphology, and electrochemical performance of the regenerated LFP (D‐LFP) materials at different temperatures were systematically investigated. Notably, the D‐LFP material generated through calcination at 650 °C for 10 h exhibited a initial discharge capacity of 154.4 mAh g−1 at 0.5 C and the capacity retention rate of 97.3 % after 100 cycles. Moreover, a detailed investigation of the kinetics of the separation and regeneration processes was carried out, along with an exploration of the underlying electrochemical mechanism. This idea not only mitigates the harmful impact of waste on both human health and the environment but also realizes the transformation of waste into valuable resource treasure, promoting a greener and more sustainable development of society. [ABSTRACT FROM AUTHOR]

Heterostructure NaMnO2–Li0.5Mn2O4 cathode materials were prepared by adjusting the molar ratio of sodium in the materials by a solid phase method. X-ray diffraction (XRD) analysis showed that the prepared samples were a layered-spinel heterostructure NaMnO2–Li0.5Mn2O4. The lattice fingerprint region of NaMnO2–Li0.5Mn2O4 was studied by electron microscopy, and the results showed the (111) plane of Li0.5Mn2O4 and the (001) plane of NaMnO2. The heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 exhibits superior high-rate capability and excellent cycling performance. The proposed heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 cathode is investigated by in situ XRD and impedance analysis. The rate of discharge of heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 was 108.8 mA h g−1 at 500 mA g−1. The initial discharge of 0.5NaMnO2–0.5Li0.5Mn2O4 was 61.69 mA h g−1, and after 1000 cycles the discharge capacity remained 51.13 mA h g−1 at a current of 2 A g−1. The heterogeneous structure combines the advantages of high capacity of the layered structure NaMnO2 and the structural stability of the spinel Li0.5Mn2O4, which exert a synergistic effect and improve the electrochemical performance of the lithium-free layered NaMnO2 cathode material. [ABSTRACT FROM AUTHOR]

In this investigation, a lithium-free cathode material, Na0.7MnO2.05–Na0.91MnO2, was synthesized by the solid phase method. The intercalation mechanism and partial phase transformation mechanism of NMO600 were clarified by in situ X-ray diffraction and impedance. The design of the heterostructure is favourable for improving the lithium ion storage of NMO600, which can deliver a discharge capacity of 83.12 mA h g−1 at 1 A g−1 and keep 61.71 mA h g−1 after 700 cycles. [ABSTRACT FROM AUTHOR]

Herein, a facile method with high efficiency is proposed for the separation and regeneration of LiMn2O4 (LMO) cathode material for spent lithium‐ion batteries through a simple heat treatment method. At first, the aluminum foil is separated at 450 °C in air, with a separation efficiency as high as 97.95%. Then, separation LMO is regenerated with high crystallinity at 650 °C with an optimum calcination time of 6 h. Importantly, this method allows D‐LMO to exhibit high reversible capacity (133 mAh g−1 at 0.1C), high rate performance (101 mAh g−1 at 5C), and long lifespan (0.5C, 92.1% capacity retention ratio after 100 cycles). A positive effect of the pyrolysis of polyvinylidene fluoride on D‐LMO is also suggested by the results. Moreover, a detailed investigation of the kinetics of the separation and regeneration is done, and the electrochemical mechanism is explored. Furthermore, this method requires much less energy input and chemical consumption, which would be helpful for environmental protection and green recycling. [ABSTRACT FROM AUTHOR]

In this study, polyacrylonitrile and boric acid are used as the nitrogen source and boron source, respectively. The Na3V2(PO4)2F3 cathode material with a carbon layer coated by nitrogen and boron was successfully synthesized by using a mechanical ball milling assisted sol–gel method (represented as NVPF@NBC). Simultaneously, Na3V2(PO4)2F3 materials with single-atom-doped carbon have been successfully prepared in this study by using the same method. Among the above materials, NVPF@NBC exhibits appreciable electrochemical performance because of the synergistic effect of diatoms in carbon. NVPF@NBC shows an outstanding specific discharge capacity of 127.2 mA h g−1 at 0.2C, and the capacity retention after 100 cycles is 97.6%. In particular, NVPF@NBC exhibits a discharge specific capacity of 106.3 mA h g−1 at 5C, and the capacity retention after 500 cycles is 90.59%. The X-ray diffraction analysis of the synthesized materials shows that the NVPF@NBC material has good crystallinity, indicating that the diatoms of N and B do not change the crystal structure of the material. TEM shows that the NVPF@NBC material exhibits uniform distribution of particles and a uniform carbon coating of about 4 nm. Nitrogen–boron co-doping does not influence the valence state of V3+ in the material. The results indicate that the co-doping of nitrogen and boron reinforces the crystallinity of the material and strengthens the sodium storage performance of the material, thereby greatly ameliorating the electrochemical performance of the material. [ABSTRACT FROM AUTHOR]

The cathode material Na 3 V 2 (PO 4) 2 F 3 of sodium-ion battery is well-known for its large number of ion migration channels and high working voltage. However, the electrochemical performance of Na 3 V 2 (PO 4) 2 F 3 is not very outstanding. Thus, in the present study, Na 3 V 2 (PO 4) 2 F 3 cathode materials were successfully synthesized by using the sol-gel method and mechanical milling method to enhance the electrochemical performance. The physicochemical properties of synthesized Na 3 V 2 (PO 4) 2 F 3 were investigated by using X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transition electron microscopy. X-ray diffraction spectroscopy indicates that the doping of nitrogen and sulfur did not alter the crystal form of Na 3 V 2 (PO 4) 2 F 3. Transition electron microscopy image shows that Na 3 V 2 (PO 4) 2 F 3 has a thin carbon layer, and x-ray photoelectron spectroscopy illustrates the successful doping of nitrogen and sulfur into the carbon layer. The cyclic voltammetry curves show that the nitrogen and sulfur co-doped Na 3 V 2 (PO 4) 2 F 3 samples have good reversibility and low polarization. Materials with 15% thiourea has a high discharge specific capacity (126.9 mA h g−1 at 0.2 C) at the first cycle and excellent cycle stability (126.3 mA h g−1 after 100 cycles, a capacity retention of 99.5%) among the synthesized cathode materials. In the present study, the electrochemical performance of the Na 3 V 2 (PO 4) 2 F 3 cathode material was enhanced by regulation of co-doping of nitrogen and sulfur atoms. [ABSTRACT FROM AUTHOR]

The heterostructures, xNa0.7MnO2–yLi4Mn5O12(0 < x < 1, 0 < y ≤ 1), were synthesized by a solid-phase method. X-Ray diffraction (XRD) analyses revealed that the as-prepared samples were heterostructures Na0.7MnO2 and Li4Mn5O12. Electron microscopy was used to study the lattice fingerprint area of 0.6Na0.7MnO2–0.4Li4Mn5O12 that showed (111) crystal surface of Li4Mn5O12 and (002) crystal surface of Na0.7MnO2. With different molar ratios of lithium and sodium, Li4Mn5O12 and Na0.7MnO2 in the formed heterostructure will change accordingly, during the synthesis process. The XPS data also showed that Mn3+/Mn4+ in the materials presented different ratios. The heterostructure, 0.6Na0.7MnO2–0.4Li4Mn5O12, exhibits superior high-rate capability and excellent cycle performance. The rate discharge capacity of 0.6Na0.7MnO2–0.4Li4Mn5O12 was maintained at 163.25 mA h g−1 at 500 mA g−1. When cycled at 100 mA g−1, the discharge capacity was maintained at 189.80 mA h g−1 after 50 cycles. The construction of heterostructure can take the advantage of the high capacity of the layered structure of Na0.7MnO2 and the stable spinel structure of Li4Mn5O12, which can form a synergistic effect and improve the electrochemical performance of cathode materials. [ABSTRACT FROM AUTHOR]

• Na 3 V 2 O 2 (PO 4) 2 F/C materials doped with Mg2+ were prepared successfully. • Mg2+ doping can boost cycling stability and rate performance of Na 3 V 2 O 2 (PO 4) 2 F/C. • The diffusion coefficients of Na+ in composites were enhanced by Mg2+ doping. Na 3 V 2 O 2 (PO 4) 2 F, a significant member of the polyanionic sodium superionic conductor family, exhibits high theoretical specific capacity and operating voltage. However, its application potential is hindered by its limited intrinsic conductivity. In this study, a series of Na 3 V 2–x Mg x O 2 (PO 4) 2 F/C cathode materials (x = 0, 0.05, 0.1, and 0.15) were synthesized using sol–gel and high-temperature solid-state methods. The impact of Mg2+ doping on the structural and electrochemical properties of Na 3 V 2 O 2 (PO 4) 2 F was examined. Na 3 V 1.9 Mg 0.1 O 2 (PO 4) 2 F/C demonstrated remarkable electrochemical performance, with a first cycle discharge specific capacity of 114.2 mAh/g and a capacity retention of 96.2 % after 500 cycles at 5C. The Na+ diffusion coefficient was 3.4 × 10–13 cm2 s−1. The full cell assembled with hard carbon as the counter electrode has a first cycle discharge specific capacity of 111.16 mAh/g at 0.1C and a capacity retention of 91.89 % after 50 cycles. This superior performance is attributed to the Mg2+ doping, which enhances the structural stability and accelerates sodium-ion diffusion. [ABSTRACT FROM AUTHOR]

Summary: Herein, a series of lithium‐sodium hybrid ion Na3−xLixV2(PO4)3/C (x = 2.5, 2.0, 1.5, 1.0, 0.5) as cathode materials are prepared by sol‐gel method. The lithium storage properties of Na3−xLixV2(PO4)3/C reveal that the lithium sodium ratio has a strong influence on material structure and the electrochemical properties. The multiple voltage platforms are observed at charge and discharge curve for the Na0.5Li2.5V2(PO4)3 material, as it contains rhombohedral and monoclinic Li3V2(PO4)3 phases, whereas a single voltage platform can be observed when x is less than 2, which are mixtures of Na3V2(PO4)3 with rhombohedral structure and Li3V2(PO4)3 with rhombohedral structure. Notably, NaLi2V2(PO4)3/C prepared by the calcination at 700°C for 8 hours contains a single rhombohedral phase. And when the charging and discharging voltage at the range 2.5 to 4.5 V and current density at 0.5C, NaLi2V2(PO4)3/C and Na2.5Li0.5V2(PO4)3/C are prepared by the pre‐calcination at 400°C for 4 hours and subsequent calcination at 750°C for 8 hours exhibit high first‐cycle specific discharge capacities of 124.8 and 130.0 mAh·g−1. The capacities are 118.4 and 115.1 mAh·g−1 after 50 cycles, indicating excellent capacity retention. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) present the advantages of long cycle life, high voltage, and energy density and are widely made in the field of energy storage. LiVOPO 4 (LVOP), a cathode material used in LIBs, has a high conceptual capacity of 159 mAh g−1 and high operating voltage of 3.9 V. However, its low electrical conductivity and cycle performance limit its commercial applications. According to the X-ray diffraction results, orthogonal crystal LVOP and monoclinic crystal Li 3 V 2 (PO 4) 3 (LVP) coexisted in the synthesised composite material. The transmission electron microscopy results also indicated that the LVOP and LVP phases coexist, which were coated by carbon layer of about 2.5 nm. The discharge of LVOP–LVP composite material initially was 143.2 mAh g−1, and that after 120 cycles was 132.2 mAh g−1 (at 0.1 C and 3–4.5 V). Thus, the electronic conductivity and first discharge specific capacity of the material enhanced due to the introduction of fast ion conductor LVP into LVOP. Electrochemical performance improved because the introduction of LVP led to an increase in Li+ pervasion channels in the original material and the acceleration of the Li+ transmission speed. [ABSTRACT FROM AUTHOR]

Triclinic α-LiVOPO 4 with excellent electrochemical properties is prepared, using δ-VOPO 4 , LiNO 3, and a highly conductive carbon material (acetylene black) as raw materials, by a two-step method, for the first time. Transmission electron microscopy reveals that the synthesized nanoscale α-LiVOPO 4 is approximately 50–100 nm in size, and its surface is covered by 1.68 nm thick acetylene black, which not only improves the ionic conductivity of the material, but prevents material-size growth at high temperature, and particle agglomeration. In addition, the initial discharge capacity of α-LiVOPO 4 sintered at 600 °C over 10 h is the highest, reaching 111.7 mAh g −1 at 0.05 °C. The capacity retention rate is 95.1%, which is 106.3 mAh g −1 after 50 cycles. [ABSTRACT FROM AUTHOR]

• LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 was successfully synthesized by a two-step method. • The LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 has a heterogeneous structure. • The lithium superior conductor improves electrochemical performance of the LiVOPO 4. The heterostructure LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 (LVOP-LTP) was synthesized using a hydrothermal process combined with a high-temperature solid-phase method. The electron microscopic analysis demonstrates that the sample has a heterojunction. The electrochemical performance tests reveal that the heterostructure LVOP-LTP has initial discharge-specific capacity of 88.4 mAh/g at 100 mA g−1, which is superior to the single-phase LiVOPO 4 (LVOP, 25.1 mAh/g) and Li 2.72 Ti 2 (PO 4) 3 (LTP, 37.1 mAh/g). The improved electrochemical performance of heterostructure LVOP-LTP can be ascribed to the introduction of lithium superionic conductor (LISICON) and the formation of a heterojunction, which increases the lithium-ion pervasion channels and accelerates the lithium-ion transmission speed. [ABSTRACT FROM AUTHOR]