High-volumetric-energy-density lithium-ion batteries require anode material with a suitable redox potential, a small surface area, and facile kinetics at both single-particle and electrode level. Here a family of coarse-grained molybdenum substituted titanium niobium oxides Mo_xTi_1−xNb₂O_7+y (single crystals with 1~2 μm size) underwent hydrogen reduction treatment to improve electronic conduction was synthesized, which is able to stably deliver a capacity of 158.5 mAh g⁻¹ at 6,000 mA g⁻¹ (65.2 % retention with respect to its capacity at 100 mA g⁻¹) and 175 mAh g⁻¹ (73 % capacity retention over 500 cycles) at 2,000 mA g⁻¹, respectively. Via careful in situ electrochemical characterizations, we identified the kinetic bottleneck that limits their high-rate applications to be mainly ohmic loss at the electrode level (which mostly concerns electron transport in the composite electrodes) rather than non-ohmic loss (which mostly concerns Li⁺ lattice diffusion within individual particles). Such a kinetic problem was efficiently relieved by simple treatments of Mo substitution and gas-phase reduction, which enable full cells with high electrode density, and high volumetric energy/power densities. Our work highlights the importance of diagnosis, so that modifications could be made specifically to improve full-cell performance.

高体积能量密度的锂离子电池需要负极材料具有合适的氧化还原电势，较小的表面积以及在单粒子和电极水平上都容易实现的动力学。在此合成了粗晶的钼取代钛铌氧化物Mo _x Ti _{1- x} Nb ₂ O _{7+ y}（尺寸为_1〜2μm的单晶）家族，并进行了氢还原处理以改善电子传导，能够稳定地进行在6,000 mA g ^-1时提供158.5 mAh g ^-1的容量（相对于100 mA g ^-1时的容量保留65.2％）和175 mAh g ^-1（在500个循环中73％的容量保持率）分别为2,000 mA g ^-1。通过仔细的原位电化学表征，我们确定了限制其高速率应用的动力学瓶颈，主要是电极级的欧姆损耗（主要涉及复合电极中的电子传输），而不是非欧姆损耗（主要涉及锂的损耗）。⁺单个粒子内的晶格扩散）。通过简单的Mo取代和气相还原处理，可以有效地缓解这种动力学问题，这使得全电池具有高电极密度和高体积能量/功率密度。我们的工作凸显了诊断的重要性，因此可以专门进行修改以提高全细胞性能。