Realization High-Voltage Stabilization of O3-Type Layered Oxide Cathodes for Sodium-Ion Batteries by Sn Simultaneously Dual Modification

Abstract

The total global production of lithium-ion batteries (LIBs) used in electric vehicles and stationary energy storage devices has increased sharply to reach the targeted Net Zero by 2050. This leads to concerns about the future and long-term availability and cost of critical raw materials (cobalt, nickel, lithium and copper) employed in LIBs. Therefore, alternative new-generation batteries with comparable performance but using less critical raw materials are needed.Sodium-ion Batteries (NIBs) offer a wealth of possibilities for inexpensive and sustainable energy storage devices. To maximize their potential, new cathode materials with high energy densities and stable structures are required. Cobalt-free sodium transition metal oxides of O3 type are a predominant cathode for NIBs due to their appreciable specific capacity, reduction in the use of critical elements, and the potential to rival LiFePO4 in terms of energy density. However, rapid capacity fading caused by serious structural and interfacial degradation hamper this process.Herein, we provide a novel Sn-modified O3-type NaNi1/3Fe1/3Mn1/3O2 cathode with improved high-voltage stability by bulk Sn doping and surface coating simultaneously. The bulk substitution of Sn4+ stabilizes the crystal structure by alleviating the irreversible high voltage phase transition and lattice structure degradation. In the meantime, the spontaneously formed tin rich surface layer effectively inhibits surface parasitic reactions and improves interfacial stability during cycling. As a result, the Sn-modified NaNi1/3Fe1/3Mn1/3O2 cathode exhibited excellent cycling performance by an almost doubled capacity retention increase after 200 cycles within 2.0-4.1V. The influence of Sn modification on the crystal structure and electrochemical properties has been investigated for the first time, and the mechanism was studied through an extensive analysis by in situ XRD, HRTEM, FIB-SEM, XPS and Mössbauer spectroscopy.This work offers an industrially feasible strategy to simultaneously stabilize the bulk structure and interface for O3-type layered cathodes for SIBs and raises the possibility of similar effective strategies to be employed for other energy storage materials Figure 1