Induced by the hydrolysis of electrolytes, hydrofluoric acid (HF) can exacerbate the notorious transition metal dissolution, which seriously restricts the development of high-energy-density lithium batteries based on high-voltage cathodes. Irremovable water, not limited to trace water originally contained in electrolytes, can also be continuously produced upon battery fabrication and electrochemical cycling processes, which has been ignored for a long time. Herein, exempting cells from cumbersome and time-consuming industrial water-removal procedures, we simply introduced a metal–organic framework (MOF) into the inside of cells as an effective in-built water scavenger. As a result, pairing the in-built water scavengers with various high-voltage cathodes (LiNi0.5Mn1.5O4, LiNi0.8Co0.1Mn0.1O2, etc.), we demonstrated superior cycling stability (72% capacity retention after 400 cycles for LiNi0.8Co0.1Mn0.1O2, calculated from the 4th cycle after 3 cycles of activation) even under a harsh environment (200 ppm water containing electrolyte). Simply using a MOF as a water scavenger can simultaneously reduce the manufacturing costs of lithium-ion batteries while improving their lifespan and safety.
