Cobalt- and nickel-free cathode materials are desirable for developing low-cost sodium-ion batteries (SIBs). Compared to the single P-type and O-type structures, biphasic P/O structures become a topic of interest thanks to improved performance. However, the added complexity complicates the understanding of the storage mechanism and the phase behavior is still unclear, especially over consecutive cycling. Here, the properties of biphasic P2(34%)/O3(60%) Na0.8Li0.2Fe0.2Mn0.6O2 and its behavior at different states of charge/discharge are reported on. The material is composed of single phase O3 and P2/O3 biphasic particles. Sodium occupies the alkali layers, whereas lithium predominantly (95%) is located in the transition metal layer. An initial reversible capacity of 174 mAh g-1 is delivered with a retention of 82% dominated by Fe3+/Fe4+ along with contributions from oxygen and partial Mn3+/4+ redox. Cycling leads to complex phase transitions and ion migration. The biphasic nature is nevertheless preserved, with lithium acting as the structure stabilizer.
|Journal||Advanced Functional Materials|
|Publication status||Published - 2020 Oct 1|
Bibliographical noteFunding Information:
P.A. and T.R. thank for support within the LIBRA project funded over the EIG Concert Japan program financed by BMBF (01DR18003), MINECO (PCI2018‐093068), and JST. L.Y. thanks the China Scholarship Council for funding. The authors acknowledge Ms. S. Stumpf for the SEM images from the SEM facilities of the Jena Center for Soft Matter (JCSM) established with a grant from the German Research Council (DFG) and the European Funds for Regional Development (EFRE). The support by R. Wagner and M. Schürmann for XPS from Chair of material science is also gratefully acknowledged. Z.S., S.‐M.B., and X.‐Q.Y. at Brookhaven National Laboratory were supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies through Advanced Battery Material Research (BMR) program under Contract No. DE‐SC0012704. This research used resources at beamlines 7‐BM (QAS) and 23‐ID‐2 (IOS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE‐SC0012704.
© 2020 The Authors. Published by Wiley-VCH GmbH
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics