Voltage Regulation via Covalent Bond Strength to Increase Energy Density for Safe Fast‐Charging Lithium‐Ion Batteries

Abstract Safe fast‐charging anodes with high operating voltage, such as Li 4 Ti 5 O 12 (≈1.55 V) and TiNb 2 O 7 (≈1.65 V), compromise the full‐cell output voltage (2.3 V) to ensure safety, limiting the energy density. Lowering anode potential can effectively enhance energy density while maintaining safety; however, the mechanisms behind require further exploration. Here, methods are proposed to lower voltage by enhancing the M–L covalent bonding, achieved by reducing coordination number, electron‐donating inductive effects, or utilizing pseudo‐Jahn–Teller effect distortion. Using LiLaTiO 4 as a model anode, the pseudo‐Jahn–Teller effect distortion of TiO 6 octahedra is explored to show how it adds covalency to Ti–O bonds, lowing the potential (≈0.3 V). Moreover, bulk LiLaTiO 4 exhibits excellent rate performance (181 mAh g −1 at 1 A g −1 , 122 mAh g −1 at 10 A g −1 ) and good cycling stability (retention rate of 73% after 6000 cycles at 5 A g −1 ). NCM811//LiLaTiO 4 full cell demonstrates exceptionally high‐power performance (118.4 mAh g −1 at 10 C and 95.6 mAh g −1 at 20 C), achieving a voltage of 3.6 V, 57% higher than the 2.3 V, enhancing energy density to levels of graphite‐LiFePO 4 systems. These improvements are attributed to lithium storage sites with low hopping energy barriers and the structure stability of Ruddlesden–Popper perovskite, offering new insights for safe fast‐charging anodes.