Freestanding Sodium Vanadate/Carbon Nanotube Composite Cathodes with Excellent Structural Stability and High Rate Capability for Sodium-Ion Batteries

Abstract

Sodium vanadate NaV6O15 (NVO) is one of the most promising cathode materials for sodium-ion batteries because of its low cost and high theoretical capacity. Nevertheless, NVO suffers from fast capacity fading and poor rate capability. Herein, a novel free-standing NVO/multiwalled carbon nanotube (MWCNT) composite film cathode was synthesized and designed by a simple hydrothermal method followed by a dispersion technique with high safety and low cost. The kinetics analysis based on cyclic voltammetry measurements reveals that the intimate integration of the MWCNT 3D porous conductive network with the 3D pillaring tunnel structure of NVO nanorods enhances the Na+ intercalation pseudocapacitive behavior, thus leading to exceptional rate capability and long lifespan. Furthermore, the NVO/MWCNT composite exhibits excellent structural stability during the charge/discharge process. With these benefits, the composite delivers a high discharge capacity of 217.2 mA h g–1 at 0.1 A g–1 in a potential region of 1.5–4.0 V. It demonstrates a superior rate capability of 123.7 mA h g–1 at 10 A g–1. More encouragingly, it displays long lifespan; impressively, 96% of the initial capacity is retained at 5 A g–1 for over 500 cycles. Our work presents a promising strategy for developing electrode materials with a high rate capability and a long cycle life.

Enhancement of Electrochemical Properties of SIBs by Generating a New Phase in Potassium-Doped NaV6O15 Film Electrodes

“…Sodium has similar chemical properties to lithium since they are in the same main group, especially with reference to the redox behavior associated with the insertion/disinsertion mechanism . Thus, SIBs are considered to be suitable materials for replacing LIBs …”

Simultaneous pre-intercalation of caesium and sodium ions into vanadium oxide bronze nanowires for high-performance aqueous zinc-ion batteries

“…The predominant doublets at 517.1 and 524.6 eV corresponded to V 5+ 2p 3/2 and V 5+ 2p 1/2 , indicating the oxidation state of pentavalent vanadium. 38,39 Besides, the other doublets at 515.8 and 523.2 eV were assigned to V 4+ 2p 3/2 and V 4+ 2p 1/2 in association with the characteristic of tetravalent vanadium, which originated from the suitable reduction of PEG-400 on vanadium pentoxide during the hydrothermal process. Compared with NVO (Fig.…”

Unfolding the structural features of NASICON materials for sodium‐ion full cells

“…However, practical applications are still limited because of the poor intrinsic electronic conductivity (10 −6 – 10 −8 S cm −1 ) 38,39 . Several methods have been used to improve the electronic conductivity of NASICON materials by combining with carbon‐based materials, 40–42 elemental doping, 43–47 and designing 3D porous architectures 48–51 …”

“…38,39 Several methods have been used to improve the electronic conductivity of NASICON materials by combining with carbon-based materials, [40][41][42] elemental doping, [43][44][45][46][47] and designing 3D porous architectures. [48][49][50][51] In this review, we focus on the recent progress and limitations of NASICON structured electrode materials, which include phosphates (Na x M 2 (PO 4 ) 3 ), fluorophosphate (Na x M 2 (PO 4 ) 2 F), binary transition-metal phosphates (Na x MMʹ(PO 4 ) 2 F), and mixed phosphates (Na x M 2 (PO 4 )(SO 4 ) 2 and Na x M 2 (PO 4 ) 2 P 2 O 7 ) for SIBs. As only an electrochemical analysis is not enough to understand the performance of electrode materials, there is an additional focus on the Na storage mechanism, morphology, and crystal structure, coupled with different strategies, to improve the electrochemical performance.…”