Chai, K.; Zhang, J.; Li, Q.; Wong, D.; Zheng, L.; Schulz, C.; Bartkowiak, M.; Smirnov, D.; Liu, X.: Facilitating Reversible Cation Migration and Suppressing O2 Escape for High Performance Li-Rich Oxide Cathodes. Small 18 (2022), p. 2201014/1-10
10.1002/smll.202201014
Open Access Version
Abstract:
High-capacity Li-rich Mn-based oxide cathodes show a great potential in next generation Li-ion batteries but suffer from some critical issues, such as, lattice oxygen escape, irreversible transition metal (TM) cation migration, and voltage decay. Herein, a comprehensive structural modulation in the bulk and surface of Li-rich cathodes is proposed through simultaneously introducing oxygen vacancies and P doping to mitigate these issues, and the improvement mechanism is revealed. First, oxygen vacancies and P doping elongates OO distance, which lowers the energy barrier and enhances the reversible cation migration. Second, reversible cation migration elevates the discharge voltage, inhibits voltage decay and lattice oxygen escape by increasing the Li vacancy-TM antisite at charge, and decreasing the trapped cations at discharge. Third, oxygen vacancies vary the lattice arrangement on the surface from a layered lattice to a spinel phase, which deactivates oxygen redox and restrains oxygen gas (O2) escape. Fourth, P doping enhances the covalency between cations and anions and elevates lattice stability in bulk. The modulated Li-rich cathode exhibits a high-rate capability, a good cycling stability, a restrained voltage decay, and an elevated working voltage. This study presents insights into regulating oxygen redox by facilitating reversible cation migration and suppressing O2 escape.