Cation and polyanion co-doping synergy to improve electrochemical performances of Li-rich manganese-based cathode materials

The redox of anions can be realized by the Li-rich manganese-based (LRM) cathode materials at high voltage, which provides a high specific capacity application prospect for lithium-ion batteries. However, the anion redox reaction brings problems such as poor cycling performance and serious voltage decay, which can be improved by the doping method. Herein, Al3+ cation and (BO3)3-/(BO4)5- polyanion are introduced into the LRM cathode materials to achieve double site occupation and charge regulation of the structure. It results in excellent electrochemical properties, especially in terms of cycling stability. The doped sample shows a discharged capacity of 239 mAh g−1 at 0.01 C after 100 cycles and a capacity retention rate of 92.0 % (higher than 77.9 % of the pristine sample). Through the brand newly-developed in-situ electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy analysis, the joint regulation of Al3+ and (BO3)3-/(BO4)5- inhibits the attack of singlet oxygen on the electrolyte and makes the cathode electrolyte interphases (CEI) film more uniform. First-principles calculations show that the introduction of electron holes and the reduction of the covalency between transition metal and O are key factors in the improvement of electrochemical property and structural stability of the modified materials.