Tang, Y.; Zhang, Q.; Zuo, W.; Zhou, S.; Zeng, G.; Zhang, B.; Zhang, H.; Huang, Z.; Zheng, L.; Xu, J.; Yin, W.; Qiu, Y.; Xiao, Y.; Zhang, Q.; Zhao, T.; Liao, H.-G.; Hwang, I.; Sun, C.-J.; Amine, K.; Wang, Q.; Sun, Y.; Xu, G.-L.; Gu, L.; Qiao, Y.; Sun, S.-G.: Sustainable layered cathode with suppressed phase transition for long-life sodium-ion batteries. Nature Sustainability 7 (2024), p. 348–359
10.1038/s41893-024-01288-9
Abstract:
Sodium-ion batteries are among the most promising alternatives to lithium-based technologies for grid and other energy storage applications due to their cost benefits and sustainable resource supply. For the cathode—the component that largely determines the energy density of a sodium-ion battery cell—one major category of materials is P2-type layered oxides. Unfortunately, at high state-of-charge, such materials tend to undergo a phase transition with a very large volume change and consequent structural degradation during long-term cycling. Here we address this issue by introducing vacancies into the transition metal layer of P2-Na0.7Fe0.1Mn0.75□0.15O2 (‘□’ represents a vacancy). The transition metal vacancy serves to suppress migration of neighbouring Na ions and therefore maintain structural and thermal stability in Na-depleted states. Moreover, the specific Na−O−□ configuration triggers a reversible anionic redox reaction and boosts the energy density. As a result, the cathode design here enables pouch cells with energy densities of 170 Wh kg−1 and 120 Wh kg−1 that can operate for over 600 and 1,000 cycles, respectively. Our work not only suggests a feasible strategy for cathode design but also confirms the possibility of developing a battery chemistry that features a reduced need for critical raw materials.