Computational and experimental understanding of Al-doped Na3V2-xAlx(PO4)3 cathode material for sodium ion batteries: Electronic structure, ion dynamics and electrochemical properties

Guo

et al. 2020

Small

development of cathode materials with fast Na + -transport kinetics is of great significance. [2] In comparison to other cathodes including layered transition-metal oxides [3] and Prussian blue analogues, [4] polyanion-type phosphates are one superior candidate owing to the Na-super-ionic conductor (NASICON) structure composed of stable and 3D open framework connected by MO 6 octahedra (M: transition metals) and PO 4 tetrahedra. [5] Among the NASICON materials, Na 3 V 2 (PO 4 ) 3 (NVP) is one promising star cathode that exhibits high application prospects and has been studied extensively, due to the ultrafast 3D Na + transport tunnels and high lattice stability during the successive Na + -intercalation/extraction with a theoretical specific capacity of 117 mAh g −1 and working voltage of 3.3-3.4 V versus Na + /Na. [6] Nevertheless, the intrinsically poor electronic conductivity of lattice retards its application especially for highrate working, which is one of the main challenges for NVP cathode.In order to improve the electrochemical properties (especially the rate performance) of NVP cathode, the strategies proposed in recent reports mainly include: i) the nanosizing of particles and/or morphology optimization, [7] ii) coating or mixing with highly conductive carbonaceous materials, [6a,8] and iii) foreign ion doping or substitution at different lattice sites. [9] While nanometer and morphology controls are realized usually in the high-cost processes, carbon mixing at high content and ionic doping at the active sites of V [9a,10] and Na [9b] are at the expense of reducing the theoretical capacity, although the capacity decrease is relatively low at low carbon content coating. By comparison, substitution at the inactive anion (PO 4 3− ) sites can regulate and improve the electrochemical properties of phosphate cathode without the reduction and even with the increase of theoretical capacity. For example, F-substituted V-based NASICON cathodes, Na 3 V 2 (PO 4 ) 2 O 2−2x F 1+2x (0 ≤ x ≤ 1), deliver higher specific capacity and better rate performance than the maternal material of NVP. [11] In comparison to the monoatomic anion (F − ) substitution, the polyatomic anions (multivalent anions) substitution should be more effective and easier to achieve the precisely regulated preparation due to the more similar anionic structure. For example, Cui and Polyanion-type phosphate materials are highly promising cathode candidates for next-generation batteries due to their excellent structural stability during cycling; however, their poor conductivity has impeded their development. Isostructural and multivalent anion substitution combined with carbon coating is proposed to greatly improve the electrochemical properties of phosphate cathode in sodium-ion batteries (SIBs). Specifically, multivalent tetrahedral SiO 4 4− substitute for PO 4 3− in Na 3 V 2 (PO 4 ) 3 (NVP) lattice, preparing the optimal Na 3.1 V 2 (PO 4 ) 2.9 (SiO 4 ) 0.1 with high-rate capability (delivering a high capacity of 82.5 mAh g −1 even at 20 C) an...

Section: Resultsmentioning

confidence: 99%

“…Figure S9, Supporting Information shows the relationship of wavelength and absorption coefficient. According to Kubelka–Munk Equation (), [ 22 ]

{(α h ν)}^{1 / n} = B (h ν - E_{g})

Section: Resultsmentioning

confidence: 99%

Isostructural and Multivalent Anion Substitution toward Improved Phosphate Cathode Materials for Sodium‐Ion Batteries

Guo

et al. 2020

Small

“…In other way, modification approaches including element doping (Aragón et al, 2015a,b;Fang et al, 2015;Shen et al, 2015b;Xu and Sun, 2016;Zheng Q. et al, 2017;Xiao H. et al, 2018;Zhao et al, 2018;Zhu et al, 2018;Fang J. Q. et al, 2019), and nanostructures (Huang et al, 2002;Li et al, 2015c;Chu and Yue, 2016;Chen S. Q. et al, 2017;Wei et al, 2017;Zhang C. Z. et al, 2017) can also deeply influence the cycling life and rate performance of NVP.…”

Section: Modification Approaches Of Na 3 V 2 (Po 4 )mentioning

confidence: 99%

Research Progress on Na3V2(PO4)3 Cathode Material of Sodium Ion Battery

et al. 2020

Sodium ion batteries (SIBs) are one of the most potential alternative rechargeable batteries because of their low cost, high energy density, high thermal stability, and good structure stability. The cathode materials play a crucial role in the cycling life and safety of SIBs. Among reported cathode candidates, Na 3 V 2 (PO 4) 3 (NVP), a representative electrode material for sodium super ion conductor, has good application prospects due to its good structural stability, high ion conductivity and high platform voltage (∼3.4 V). However, its practical applications are still restricted by comparatively low electronic conductivity. In this review, recent progresses of Na 3 V 2 (PO 4) 3 are well summarized and discussed, including preparation and modification methods, electrochemical properties. Meanwhile, the future research and further development of Na 3 V 2 (PO 4) 3 cathode are also discussed.

Section: Influencing Factorsmentioning

confidence: 99%

“…Furthermore, Al-doping is suggested to decrease the band gap due to the low electron affinity of Al atom ( Figure 1). [19] In PBAs, the presence of Fe(CN) 6 vacancies may destroy electronic conduction along FeÀ C�NÀ M frame-work structure, thus significantly limiting the rate performance. [2,20] Based on the above reasons, both coating by materials with high electronic conductivity and defect chemistry are widely used to mitigate the limitation, which will be discussed in the following sections in detail.…”

Section: Electronic Conductivitymentioning

confidence: 99%

Strategies to Build High‐Rate Cathode Materials for Na‐Ion Batteries

Huang

Yin

et al. 2019

ChemNanoMat

The development of cathode materials for Na‐ion batteries (NIBs) has benefitted greatly from previous research on Li‐ion batteries (LIBs) due to the similar physicochemical properties between Na and Li. However, the exploitation of high‐rate NIB cathodes has faced greater difficulty compared to the Li counterparts because of the larger ionic radius of Na. Numerous attempts to optimize the composition and structure have been made to address this issue, and great progress has been achieved in recent years. Herein, a systemic review on the latest research in high‐rate cathode materials for NIBs is presented. In addition, a comprehensive analysis on specific reasons hindering the kinetic performance is also discussed, which is expected to deepen the understanding of the mechanisms behind rate performance and provides a new avenue for the design of high‐performance NIBs.