Transition metal carbonate hydroxide (CH) has been widely explored as a promising battery-type electrode for high-rate energy storage. However, its genuine active sites under realistic operating conditions remains elusive. Here, by virtue of the cutting-edge operando X-ray absorption spectroscopy, we unfold the dynamic evolution of the local electronic and geometric structures for the CH electrode upon cycling. Our results reveal that the irreversible redox of Co cations at the early stage of cyclic voltammetry (CV) cycling induces a phase transition in the NiCo CH nanowires forming oxygen vacancies-enriched NiCo layered double hydroxide (LDH) nanosheets with superior high-rate energy storage ability. Theoretical modeling demonstrates that the unsaturated 5-coordinated Co sites exhibit optimal redox reaction energy barrier and immensely promote the performance. These findings not only elucidate the electrochemical susceptibility of the Co-based carbonate hydroxide under operando conditions, but also highlight an electrochemical coordination-engineering strategy for the rational design of high-performance electrode.

过渡金属碳酸盐氢氧化物（CH）已被广泛探索为一种用于高倍率能量存储的有前途的电池型电极。但是，在实际操作条件下其真正的活动场所仍然难以捉摸。在这里，凭借先进的操作X射线吸收光谱，我们展示了循环时CH电极的局部电子和几何结构的动态演变。我们的结果表明，在循环伏安法（CV）循环的早期，不可逆的Co阳离子氧化还原在NiCo CH纳米线中引起相变，从而形成富氧空缺的NiCo层状双氢氧化物（LDH）纳米片，具有出色的高速率储能能力。理论建模表明，不饱和的5位配位的Co位点表现出最佳的氧化还原反应能垒，并极大地提高了性能。这些发现不仅阐明了钴基碳酸氢盐在操作过程中的电化学敏感性。 的条件下，也突出了用于合理设计高性能电极的电化学配位工程策略。