Atomic-Level Structure and Dynamic Evolutions in Cobalt-Free High-Performance Sodium-Ion Battery Cathode

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Sodium-ion batteries (SIBs) have the potential to emerge as a cost-effective and more sustainable alternative to conventional lithium-ion batteries (LIBs). While SIBs still suffer from lower performances and long-term cyclability because their limitation has not received much attention in comparison to their Li-ion counterparts. Like LIBs, the performance of SIBs relies heavily on the cathode materials; however, performance improvements have been primarily driven so far by trial-and-error efforts because of the lack of understanding of their atomic-level microscopic structure, ion dynamics as well as degradation mechanisms. To address these identified challenges associated with SIB cathodes, the proposed research will use a multi-scale and complementary material characterization approach, including state-of-the-art solid-state nuclear magnetic resonance (SSNMR) spectroscopic techniques, to undertake a thorough investigation of biphasic NaxTMO2 (x = 0 to 1, and TM = transition metal ion) cathodes, which, as reported in recent literature, exhibit better stability and electrochemical performance. Here, ex-situ and operando SSNMR spectroscopy will be utilized extensively toquantitatively deconvolute the atomic-level microscopic structure and ion dynamics mechanism of biphasic NaxTMO2 cathodes; the information gained will ultimately be correlated with the macroscopic electrochemical performance of the SIB battery devices. SSNMR spectroscopy will assist to unravel the presence or absence either of phase-segregation, nanodomains, or intergrowth formation taking place between two phases of biphasic NaxTMO2 and how they affect the battery performance. In summary, this proposed research will provide an exclusive understanding of the macroscopic electrochemical properties that directly correlate with the real-time microscopic atomic-level structural and ion dynamic changes of these newly identified biphasic NaxTMO2 cathodes for emerging SIB technology.