Selectively Coordinating Solid Polymer Electrolytes Enable Nonmodified 4.6 V-LiCoO 2 for High-Capacity and Long-Cycling Lithium Batteries

LiCoO2 (LCO) is often modified through surface coating, bulk doping, or a combination of both to inhibit its irreversible phase transitions over 4.6 V. However, modified LCO may have exacerbated interfacial impedance and/or reduced electrochemical activity, leading to a decreased discharge capacity in cells. Here, we develop a solid polymer electrolyte (SPE) with selective ion coordination to enable nonmodified 4.6 V-LCO for high-capacity and long-cycling lithium batteries. The tight coordination of copolymerized methylacrylonitrile to Co3+ stabilizes nonmodified 4.6 V-LCO, whereas its unwanted binding to Li+ is weakened by competition from substantial dissociated anions. As a result, the nonmodified 4.6 V-LCO|SPE|Li cell at 25 °C delivers not only a high initial discharge capacity of 199.32 mAh g–1 at 0.5 C and a capacity retention of 88% after 200 cycles but also decent rate performance. Our work establishes a promising selective coordination strategy for enabling high-voltage cathodes without the need of any modifications.