Capture Lithium in αMnO₂: Insights from First Principles

Abstract

Here we report the study of Li and Li oxides insertion in αMnO 2 with firstprinciples density functional theory calculations. For Li insertion, the redox reaction is characterized with a particular order of the reduction of Mn ions. It induces asymmetric changes of lattice parameters through Jahn−Teller distortion of MnO 6 units. At composition of LiMn 2 O 4 , the ratio between lattice parameter a and b extends to the highest value, 1.19. The severe structural deformation is concluded to be the major cause of the irreversible capacity when αMnO 2 is used as Li-ion battery cathodes. On the other hand, the structure of αMnO 2 is stable to reversibly insert and remove Li oxides. Li oxides inserted αMnO 2 is half metallic instead of insulating. On the basis of our results, a mechanism is proposed to explain the role of αMnO 2 in the catalyzed decomposition of Li 2 O 2 . The key step in this mechanism is the insertion of Li oxides in αMnO 2 . The insertion transfers electrons from Li oxides to MnO 2 and partially oxidized Li oxides, making the subsequent release of O 2 easier.

Electrochemistry of Hollandite α-MnO2: Li-Ion and Na-Ion Insertion and Li2O Incorporation

“…This position is nearest to an 8h Wyckoff position in agreement with the results of Ling and Mizuno. 47 It is important also to note that intercalation at the 8h′ sites lies only 24 meV higher and therefore a mixed occupation, particularly at finite temperature, may occur. Table 2 also shows the site energies for insertion of sodium ions.…”

“…Ling and Mizuno 47 have calculated the formation energy of the series α-Li x MnO 2 for x = 0 to x = 1 assuming insertion at the 8h site. The 8h site was chosen based upon calculation of the favorable insertion sites at small lithium compositions x = 0 to x = 0.125.…”

Manganese Dioxide As Rechargeable Magnesium Battery Cathode

“…However, it was revealed that the cycling of α-MnO2 in LIB is not stable due to asymmetric distortion of lattice, resulting in poor capacity retention (Thackeray, 1997;Ling and Mizuno, 2012;Yuan et al, 2015).…”

Sponge-Like Porous Manganese(II,III) Oxide as a Highly Efficient Cathode Material for Rechargeable Magnesium Ion Batteries

“…[29][30][31] Among them, MnO2 is perhaps the most extensively studied electrode material in many kinds of batteries. [32][33][34] Several polymorphs of MnO2 have also been investigated as possible MIB cathodes, [35][36][37][38][39] especially α-MnO2. It showed a high specific capacity of ~280 mAh g -1 in the initial discharge, but poor cyclic performance (retained ∼50 mAh g -1 after just five cycles).…”