Mixed structures as a new strategy to develop outstanding oxides-based cathode materials for sodium ion batteries: A review

Abstract Sodium ion batteries (SIBs) are an exciting alternative for post-lithium energy storage. They can be regarded as a promising and cost-efficient solution for grid applications as they exhibit similar ‘rocking chair’ mechanism as lithium ion batteries, in addition to the abundance and low cost of sodium resources. Indeed, electrode materials, electrolytes, separators and smart design strategies are under spot and researchers are competing to come up with the ideal battery. Layered oxides with mixed structures are regarded as new concept that can offer a set of desired structural and energetic properties and are an attractive choice for next generation sodium ion batteries. However, unlocking this system chemistry, kinetics and reliable understanding of the intercalation/deintercalation mechanism upon electrochemical cycling is quite challenging. This review, through the examination of literature, gives a brief summary of the research progress and recent advances in the investigation of electrode materials based on layered oxides with mixed structures for sodium ion batteries. This new strategy leads in fact to positive electrodes with enhanced energetic performance as they consist of a combination of the energetic or/and structural properties of the existing structures.