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

钠离子电池（sib）有潜力成为传统锂离子电池（lib）的一种更具成本效益和可持续性的替代品。然而sib的性能和长期可循环性仍然较低，因为与锂离子电池相比，sib的局限性没有得到太多关注。与lib一样，sib的性能在很大程度上依赖于正极材料；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，迄今为止，性能的改进主要是由试错努力驱动的。为了解决与SIB阴极相关的这些确定的挑战，提议的研究将使用多尺度和互补材料表征方法，包括最先进的固态核磁共振（SSNMR）光谱技术，对双相NaxTMO2 （x = 0到1，TM =过渡金属离子）阴极进行彻底的研究，根据最近的文献报道，这种阴极具有更好的稳定性和电化学性能。本文将广泛地利用非原位和操作的SSNMR光谱来定量地解析双相NaxTMO2阴极的原子级微观结构和离子动力学机制；所获得的信息将最终与SIB电池器件的宏观电化学性能相关联。ssmr光谱将有助于揭示在双相NaxTMO2的两相之间存在或不存在相分离、纳米结构域或互生形成，以及它们如何影响电池性能。综上所述，本研究将为新兴SIB技术提供宏观电化学特性的独家理解，这些宏观电化学特性与这些新鉴定的双相NaxTMO2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.