Premium
Transformation of Spinel Zn 2 Mn 4 O 8 ·H 2 O to Layered δ‐MnO 2 ‐Based Composite Nanosheets with Enhanced Capacitance in Aqueous Electrolyte
Author(s) -
Wang Shuqing,
Chen Jianyu,
Elkholy Ayman E.,
Liu Xuehua,
Li Hongliang,
Lin Chunfu,
Guo Peizhi
Publication year - 2021
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.202000649
Subject(s) - spinel , calcination , electrolyte , materials science , aqueous solution , cyclic voltammetry , electrochemistry , phase (matter) , composite number , inorganic chemistry , chemical engineering , chemistry , electrode , metallurgy , composite material , catalysis , organic chemistry , engineering , biochemistry
Transition from the layered phase to spinel phase of active materials usually occurs in lithium secondary batteries with organic electrolytes, whereas the reverse conversion is rarely observed during electrochemical measurements. Herein, spinel Zn 2 Mn 4 O 8 ·H 2 O nanoparticles (NPs) are synthesized at room temperature and are transformed into large spinel ZnMn 2 O 4 particles after calcination at 800 °C. Cyclic voltammetry of the Zn 2 Mn 4 O 8 ·H 2 O NPs‐based electrodes leads to the formation of δ‐MnO 2 ‐based composite nanosheets at the potential window of 0−1.2 V, and the latter shows the capacitances of 187 and 327 F g −1 at 0.1 A g −1 in aqueous Na 2 SO 4 and MgSO 4 electrolytes, respectively. However, the spinel‐to‐layered phase transition is not observed for Zn 2 Mn 4 O 8 particles, which show a much lower capacitance even in MgSO 4 solution. The presence of crystal water in Zn 2 Mn 4 O 8 ·H 2 O NPs, combined with the existence of Na + or Mg 2+ , not Al 3+ ions in electrolytes, is helpful for both the release of Zn (II) ions and movement of Mn (III) ions during the spinel‐to‐layered phase transition driven by electrochemistry. The unique transition of Zn 2 Mn 4 O 8 ·H 2 O NPs to δ‐MnO 2 ‐based composite nanosheets and their structure–property relationship are discussed and analyzed based on the experimental results.