A High-Rate, Durable Cathode for Sodium-Ion Batteries: Sb-Doped O3-Type Ni/Mn-Based Layered Oxides

Abstract

O3-Type layered oxides are widely studied as cathodes for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, their rate capability and durability are limited by tortuous Na+ diffusion channels and complicated phase evolution during Na+ extraction/insertion. Here we report our findings in unravelling the mechanism for dramatically enhancing the stability and rate capability of O3-NaNi0.5Mn0.5–x Sb x O2 (NaNMS) by substitutional Sb doping, which can alter the coordination environment and chemical bonds of the transition metal (TM) ions in the structure, resulting in a more stable structure with wider Na+ transport channels. Furthermore, NaNMS nanoparticles are obtained by surface energy regulation during grain growth. The synergistic effect of Sb doping and nanostructuring greatly reduces the ionic migration energy barrier while increasing the reversibility of the structural evolution during repeated Na+ extraction/insertion. An optimized NaNMS-1 electrode delivers a reversible capacity of 212.3 mAh g–1 at 0.2 C and 74.5 mAh g–1 at 50 C with minimal capacity loss after 100 cycles at a low temperature of −20 °C. Such electrochemical performance is superior to most of the reported layered oxide cathodes used in rechargeable SIBs.

A Universal Strategy Based on Bridging Microstructure Engineering and Local Electronic Structure Manipulation for High-Performance Sodium Layered Oxide Cathodes

“…In situ charge and discharge XRD studies were conducted to further understand the crystal structure evolution of the NaNMS-0.05 electrode during cycling . The 3D counter graphs and related intensity contour maps (bird’s eye view) could show the phase change process (Figures a,b, Figures S16, S17).…”

Recent Progress in the Emerging Modification Strategies for Layered Oxide Cathodes toward Practicable Sodium Ion Batteries

“…Recently, Nb and Sb ions have also been used as dopant to improve the electrochemical performance of layered oxide. [64,65] Shi et al [64] prepared Nb ion doped P2-type Na 0.78 Ni 0.31 Mn 0.67 Nb 0.02 O 2 . They found that Nb ion mostly doped at the particle surface, which could serve as a coating layer and protect the particle from electrolyte attack.…”

“…Recently, Nb and Sb ions have also been used as dopant to improve the electrochemical performance of layered oxide. [ 64,65 ] Shi et al. [ 64 ] prepared Nb ion doped P2‐type Na 0.78 Ni 0.31 Mn 0.67 Nb 0.02 O 2 .…”

Surface Lattice‐Matched Engineering Based on In Situ Spinel Interfacial Reconstruction for Stable Heterostructured Sodium Layered Oxide Cathodes

“…[20][21][22] The O-type Na x TMO 2 usually delivers a great capacity (≈160 to 220 mAh g −1 ) because of the high Na contents stacking sequence, however, it suffers from the sluggish Na + transport kinetics and fast capacity decay caused by unfavorable Na + diffusion pathway and complicated phase translation when going through the process of embedding and extracting Na + . [23][24][25][26] Compared with O-type, the P-type Na x TMO 2 is able to achieve a better rate and cycling performance because of the open prismatic structure which is a benefit to Na + mobility. [27][28][29] Whereas volume expansion occurring through irreversible P2-O2 phase translation at high voltage would result in the capacity decrease, which would hinder the achievement of high-energy density SIBs.…”