Capacity fading of Li₄Ti₅O₁₂ (LTO) is inevitable during cycling; hence it is of great significance to clarify the factors causing the capacity degradation so as to take some measures to prolong the lifespan of LTO. Despite the investigation on the capacity fading mechanism within finite charge/discharge cycles, the fading mechanism during long-term cycling is still absent. Here, LTO half-cells underwent more than 700 lithiation/delithiation cycles at a current rate of 0.5 A g⁻¹, and the changes in structure, composition, cyclic voltammogram and electrochemical impedance with cycling were probed systematically to comprehend the capacity decay. Except for the performance degradation that resulted from the electrolyte decomposition and gassing effect during cycling, the transition from spinel LTO to rock-salt Li₇Ti₅O₁₂ accompanied by structural and compositional variation also leads to a capacity fading of LTO, namely, the repetitive lithiation/delithiation gives rise to more and more residual Li⁺ and Ti³⁺ in the delithiated LTO, structure disordering, gradually depressed ionic and electronic conductivities, and escalated polarization, thus aggravating the performance decay.

中文翻译：

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Li4Ti5O12在长期循环过程中的成分和结构容量下降。

在循环过程中，Li ₄ Ti ₅ O ₁₂（LTO）不可避免地发生容量衰减；因此，弄清容量下降的原因，以期采取措施延长LTO的使用寿命具有重要意义。尽管对有限的充电/放电循环内的容量衰减机制进行了研究，但长期循环中的衰减机制仍然不存在。在此，LTO半电池以0.5 A g ^-1的电流速率经历了700多次锂化/脱锂循环，并系统地研究了结构，组成，循环伏安图和电化学阻抗随循环的变化，以了解容量衰减。除了由于循环过程中的电解质分解和放气作用而导致的性能下降外，从尖晶石LTO过渡到岩盐Li ₇ Ti ₅ O ₁₂并伴随结构和成分变化也导致LTO的容量衰减，即重复的锂化/去锂化会在去锂化的LTO中产生越来越多的残留Li ⁺和Ti ³⁺，结构紊乱，离子电导率和电子电导率逐渐降低，极化加剧，从而加剧性能衰减。