Enhanced Cycling Stability and Rate Capability in a La-Doped Na₃V₂(PO₄)₃/C Cathode for High-Performance Sodium Ion Batteries

Abstract

In recent years, phosphate Na3V2(PO4)3 (NVP) has attracted considerable attention as a promising cathode for high-performance sodium ion batteries owing to its open 3D framework structure. However, low rate capacity of the material greatly hampers the practical application due to its poor conductivity. Herein, La-doped Na3V2–x La x (PO4)3/C materials were prepared by a combination process of sol–gel and carbon-thermal reduction methods. All materials possess NASICON-type structure with the R3̅C space group. No impurity can be detected, and a thin carbon layer is coated on the surface of the materials. The doping of La3+ significantly reduces internal resistance and enhances fast Na+ mobility. As a result, the material with the addition of 2% La3+ exhibits excellent cyclic performance and rate capability: a high initial reversible capacity of 105.4 mA h g–1 at 0.2 C, capacity retentions of 96.5% at 1 C after 200 cycles, and excellent rate performance of 92.6 mA h g–1 at 30 C. Under a high current density of 20 C for 3000 cycles, it can still deliver a superior reversible capacity of 73.5 mA h g–1 with a high capacity retention of 93.5%. Even at 50 C, the Na3V1.98La0.02(PO4)3/C electrode can release a satisfactory initial capacity of 79.9 mA h g–1 with an average Coulombic efficiency of 99.3% after 8000 cycles. Our work demonstrates that La3+-doped Na3V2(PO4)3/C may be a promising candidate of cathode for high-performance sodium ion batteries.

Construction and Operating Mechanism of High‐Rate Mo‐Doped Na3V2(PO4)3@C Nanowires toward Practicable Wide‐Temperature‐Tolerance Na‐Ion and Hybrid Li/Na‐Ion Batteries

“…[ 24 ] As illustrated in Figure 1c, the NVP shows a typical 3D framework of VO 6 octahedra units sharing all of its corners with PO 4 tetrahedra units. [ 27 ] There exist two different types of Na1 and Na2 ions in the interstitial sites of the framework, which occupy the M1 (sixfold coordination) and M2 (eightfold coordination) sites, respectively. [ 29 ] One particularly notes that only the Na2 can be reversibly extracted/inserted for charge storage due to the smaller bond populations of M2 sites resulting from the relatively weak limited environments.…”

“…[23][24][25] Typically, the inherent physical properties of NVP can be ultimately ameliorated by doping of metal ions, which can moderately tune the atomic configuration and lattice structure. [26,27] Furthermore, the Na + vacancies, facilitating electronic conductivity and enhancing ion diffusion kinetics of electrodes, will be engendered due to valance balance when doping cations with higher valence are introduced into the NVP, mainly due to the smaller migration barrier for Na + and electrochemical resistance. [24,25,28] In spite of these pioneering advances, each design always results in only a limited improvement in electrochemical behaviors of electrodes.…”

Polyanion Sodium Vanadium Phosphate for Next Generation of Sodium‐Ion Batteries—A Review

“…Table 1 lists ions used in the modification, including modification of V 3+ site at six‐coordination octahedron, of P 5+ site at four‐coordination of tetrahedron and of interstitial Na + site. Most popular studies focus on trivalent element substitutions, such as Al 3+ , [ 73,85–89 ] Cr 3+ , [ 89–92 ] Fe 3+ , [ 83,89,93,94 ] La 3+ , [ 96 ] Mo 3+ , [ 97,98 ] Mn 3+ , [ 99 ] and Ce 3+ . [ 100 ] Since V is a trivalent element in as synthesized N 3 VP, neutrality of the substitution of V by trivalent element can be easily reached through where M is a cation.…”

Multiple Active Sites Carbonaceous Anodes for Na+ Storage: Synthesis, Electrochemical Properties and Reaction Mechanism Analysis

“…Metal oxides/sulfides anodes show tremendous potentials for Na ions storage due to their high theoretical capacity and diversified crystal structures. [ 145,146 ] However, large volume expansion and low conductivity, accompany with structural topple down and unsatisfied electronic conductivity during sequential cycling process, always lead to rapid capacity fading. [ 147–149 ] Hence, the combination of metal oxides/sulfides and carbonaceous materials are considered as a promising strategy to cope with these issues.…”