摘要
Sodium-ion batteries have been deemed as a sustainable alternative to lithium-ion systems due to the abundance and affordability of sodium sources.Nevertheless,developing high-energy-density P2-type layered oxide cathodes with long-term cycling stability poses challenges,stemming from irreversible phase transitions,structural degradation,and lattice oxygen instability during electrochemical cycling.Here,we propose a one-step NbB_(2)modification strategy that enhances both bulk and surface properties of Na_(0.8)Li_(0.12)Ni_(0.22)Mn_(0.66)O_(2)cathodes.By exploiting different techniques,we disclose that bulk Nb and B doping combined with a Nb-Transition Metal-BO_(3)surface layer reconstruction enable a reversible P2-OP4 phase transition and,meanwhile,improve anionic redox reversibility.In addition,Li^(+)migrates into alkali-metal layers and underpins the layered structure through the“pillar effect”,thereby facilitating the Na^(+)diffusion in Na_(0.8)Li_(0.12)Ni_(0.22)Mn_(0.66)O_(2)cathodes and retaining their structural integrity at high voltage.As a result,the modified cathodes achieve 93.6%capacity retention after 500 cycles at 1C and deliver specific capacities above 114 m A h g^(-1)at 10C within 2.0-4.3 V.Contrary to the previous studies reporting that OP4 phase are detrimental to the structural stability of layered cathodes,we experimentally validate that a well-regulated P2-OP4 phase transition is beneficial for structural and electrochemical stabilities.
基金
financially supported by the National Key R&D Program of China(2020YFA0406203)
National Natural Science Foundation of China(92472115,52371225 and 52072008)
Guangdong Basic and Applied Basic Research Foundation(2022B1515120070,2022A1515110816 and 2022A1515110596)
the Large Scientific Facility Open Subject of Songshan Lake,Dongguan,Guangdong(KFKT2022A04)
Jialin Xie Fund(E4546IU2)
the open research fund of Songshan Lake Materials Laboratory(2023SLABFN02)
The Major Science and Technology Infrastructure Project of Material Genome Big-science Facilities Platform supported by the Municipal Development and Reform Commission of Shenzhen also contributed to this research
the allocation of beamtime at BL15U and BL02B02 beamlines at SSRF。
