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

钠离子电池（SIB）有可能成为传统锂离子电池（LIB）的成本效益和更可持续的替代品。虽然SIB仍然遭受较低的性能和长期可循环性，因为与它们的锂离子对应物相比，它们的限制没有得到太多的关注。与LIB一样，SIB的性能在很大程度上依赖于阴极材料;然而，由于缺乏对其原子级微观结构、离子动力学以及降解机制的理解，到目前为止，性能改进主要是由试错法驱动的。为了解决这些与SIB阴极相关的挑战，拟议的研究将使用多尺度和互补的材料表征方法，包括最先进的固态核磁共振（SSNMR）光谱技术，对双相NaxTMO 2进行彻底的研究。（x = 0至1，且TM =过渡金属离子）阴极，如最近的文献中所报道的，其表现出更好的稳定性和电化学性能。在这里，非原位和操作SSNMR光谱将被广泛用于定量解卷积双相NaxTMO 2阴极的原子级微观结构和离子动力学机制;所获得的信息最终将与SIB电池装置的宏观电化学性能相关。SSNMR光谱将有助于揭示两相NaxTMO 2之间是否存在相分离、纳米畴或共生形成，以及它们如何影响电池性能。总之，这项拟议的研究将提供对宏观电化学性质的独家理解，这些宏观电化学性质与新兴SIB技术的这些新发现的双相NaxTMO 2阴极的实时微观原子级结构和离子动力学变化直接相关。

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.