Modified structural characteristics and enhanced electrochemical properties of oxygen-deficient Li2MnO3-δ obtained from pristine Li2MnO3
Abstract
Lithium-rich manganese(IV) oxide Li2MnO3 has hardly any activity as the cathode active substance of lithium-ion batteries (LIBs) but its reversible capacity can be greatly improved by introducing oxygen deficiencies. After the solid-state heat treatment of nanocrystalline Li2MnO3 by sodium borohydride (NaBH4), the resulting Li2MnO3-δ crystallites comparatively acquire distinguishable appearances in color and shape and slight differences in surface composition and lattice structure. As a LIB cathode within the potential range of 2.5-4.7 V, at 20 mA g-1 pristine Li2MnO3 gives the specific discharge capacities of 3.3, 5.0 and 7.4 mAh·g-1 in the 1st, 10th and 100th cycles, while the derivative Li2MnO3-δ delivers the relatively high values of 64.8, 103.8 and 140.2 mAh·g-1 in the 1st, 10th and 120th cycles, respectively. Aside from the similar phenomenon of gradual electrochemical activation, substituting Li2MnO3-δ for Li2MnO3 means the great enhancements of charge-transfer ability and electrochemical performances. Especially, the cationic-anionic redox mechanisms of Li2MnO3 and Li2MnO3-δ are similar to each other, suggesting a possible solution to prepare high-performance xLi2MnO3-δ·(1-x)LiMO2 solid solutions for application purposes.
- Publication:
-
Journal of Power Sources
- Pub Date:
- January 2018
- DOI:
- 10.1016/j.jpowsour.2017.11.004
- Bibcode:
- 2018JPS...374..134T
- Keywords:
-
- Lithium-rich manganese(IV) oxide Li<SUB>2</SUB>MnO<SUB>3</SUB>;
- Oxygen-deficient Li<SUB>2</SUB>MnO<SUB>3-δ</SUB>;
- Sodium borohydride NaBH<SUB>4</SUB>;
- Electrochemical activation;
- Lithium-ion batteries