Excellent rate performance of Li_4+xTi₅O₁₂ (0 < x < 3, LTO) electrodes results from mixed Li site occupancy and facile Li ion exchange at 8a and 16c sites. In this paper, we reveal that inter-particle connectivity within LTO electrodes affects 8a and 16c site occupancies upon discharge and impacts Li ion diffusion. LTO electrodes of the same primary crystal structure but of different grain boundary structures were prepared and they showed significantly different electrochemical performance. LTO electrodes with a percolated 3D structural network and bridged grain boundaries offered balanced 8a-16c occupancy, Li ion exchange at 8a and 16c sites upon discharge, high ionic conductivities, and good rate performance. While LTO electrodes with isolated clusters of particles showed strong rate dependence of 8a-16c occupancy, a lack of Li ion exchange at 8a and 16c sites, large over-potential, and substantial capacity decay upon fast charging. Bridged grain boundaries in LTO secondary particles facilitate apparent solid-solution process during electrochemical cycling by maintaining Li site exchange and thus enhance the rate performance of LTO electrodes.

中文翻译：

---

具有桥接晶界的Li4Ti5O12阳极的倍率性能增强

Li _{4 + x} Ti ₅ O _12的优异倍率性能（0 ＜x ＜3，LTO）电极是由于混合的Li位点占据和在8a和16c位点处容易的Li离子交换而产生的。在本文中，我们揭示了LTO电极内的粒子间连通性会在放电时影响8a和16c的位置占用，并影响Li离子扩散。制备具有相同初级晶体结构但具有不同晶界结构的LTO电极，它们显示出明显不同的电化学性能。具有渗透性3D结构网络和桥接晶界的LTO电极可提供平衡的8a-16c占有率，放电后在8a和16c位置的锂离子交换，高离子电导率和良好的倍率性能。虽然LTO电极具有孤立的颗粒簇，但对8a-16c的占有率具有很强的速率依赖性，但在8a和16c的位置缺乏锂离子交换，快速充电时，大的过电位和相当大的容量会衰减。LTO二次粒子中的桥接晶界通过维持Li位点交换，促进了电化学循环过程中的表观固溶过程，从而增强了LTO电极的倍率性能。