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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]

• 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]

Nanoparticle Na3V2(PO4)3/C materials with different polyacrylonitrile contents can be successfully synthesized using precipitation method. As an energy storage material used in the production of lithium batteries which is also compared with pure of that, the Na3V2(PO4)3/C not only has a larger capacity, but also has a very high cycle stability. In particular, the initial discharge capacities of the Na3V2(PO4)3/C sample annealed at 750°C containing 10 wt% of polyacrylonitrile are 130.9 and 122.2 mAh g−1 at current densities of 0.5 and 1 C, respectively; the corresponding coulomb efficiencies are 97.3 and 99.5%. It is also worth noting that the capacity retention can reach as high as 92.7% for 500 cycles at 1 C. [ABSTRACT FROM AUTHOR]

A series of LiFe 1−x Mn x PO 4 /C composites (x=0, 0.1, 0.3, 0.5, 1) are synthesized via an ion exchange method, utilizing LiOH·H 2 O, FeSO 4 ·7H 2 O, MnSO 4 ·H 2 O, Na 3 PO 4 ·12H 2 O, and H 3 PO 4 as the raw materials, citric acid as the carbon source, and reductant, and H 2 O as the solvent. The composites containing Mn have larger lattice parameters compared to pure LiFeMnPO 4 /C, due to the larger ionic size of Mn 2+ compared to Fe 2+ . The composites also consist of spherical nanoparticles with a thicker carbon coating. LiFe 0.9 Mn 0.1 PO 4 /C exhibited the best electrochemical properties as the cathode in lithium-ion batteries, with a discharge capacity close to the theoretical value of LiFePO 4 , better capacity retention rate (98.5% vs. 94.5%) and excellent cycle stability. The improvements were attributed to the Mn-complex. Electrochemical impedance spectra demonstrate that the Mn-composites can improve electronic and ionic conductivity, indicating that introduction of Mn is a viable way to improve the conductivity in olivine-like LiFePO 4 cathode materials, and enhance the battery performance. [ABSTRACT FROM AUTHOR]