Mechanisms of capacity degradation in reduced graphene oxide/α-MnO₂nanorod composite cathodes of Li–air batteries

Abstract

The electrochemical performance of rechargeable Li-air batteries containing a reduced graphene oxide (rGO)/a-MnO 2 composite and neat a-MnO 2 electrode is studied. The rGO/a-MnO 2 composite exhibits a specific capacity as high as 558.4 mA h g À1 at a current density of 100 mA g À1 , indicating its potential to make a good cathode material. The composite electrode also presents a relatively moderate degradation of capacities with increasing cycles, compared to the neat a-MnO 2 electrode. rGO functions as the conducting medium to connect the a-MnO 2 nanorods, thus improving the Li ion transfer. The mechanisms responsible for the capacity degradation in the composite electrodes are studied after a series of interrupted charge/discharge cycles, detecting Li 2 O 2 and LiF as the main reaction products formed on the electrode surface. In particular, the LiF layer is identified to be an important component of reaction products, which serves as a barrier to reactions between the Li ions and electrons with the electrode, giving rise to detrimental effects on the cyclic and capacity performance of Li-air batteries.

Silver decorated alpha-manganese oxide nanostructured electrocatalyst for rechargeable lithium–oxygen battery

“…Besides that, the Mn 2p XPS spectrum exhibits two major peaks with BE values at 642.2 eV and 653.8 eV in Fig. 2b and a spin-energy separation of 11.6 eV, which are in good agreement with the reported data of Mn 2p 3/2 and 2p 1/2 for MnO 2 [18]. XPS results show that the composite consists of MnO 2 and Ag.…”

Direct Growth of Flower‐Like δ‐MnO2 on Three‐Dimensional Graphene for High‐Performance Rechargeable Li‐O2 Batteries

“…It suggests that the presence of Li 2 CO 3 deactivates the oxygen electrode and retards the decomposition of Li 2 O 2 , leading to the increase in electrode polarization and performance degradation with cycles. [ 26,[42][43][44] To illustrate the unique design and excellent catalytic activity of our 3D-G-MnO 2 air electrode, the electrochemical performance of the Li-O 2 batteries with 3D-G-MnO 2 is compared with those of the batteries with other manganese-based catalysts as summarized in Table 1 . These reference data represent the best results on manganese-based electrocatalysts reported to date.…”

“…In the previous work by other groups, MnO 2 was also investigated as the oxygen cathode catalysts. [26][27][28][29] Morphology and structural changes of discharge-charge products with cycles were also studied to investigate the electrochemical reaction mechanism of Li-O 2 batteries, indicating that MnO 2 is a potential good catalyst. However, the Li-O 2 batteries developed so far unavoidably face capacity degradation after a few discharge-charge cycles.…”

Recent Progress on Stability Enhancement for Cathode in Rechargeable Non‐Aqueous Lithium‐Oxygen Battery

“…By virtue of the large surface area and good electronic conductivity that is comparable to other carbonaceous materials such as CNTs, [105][106][107] the graphene has also been widely used in Li-O 2 batteries, together with polymer binders. [108][109][110] However, the challenges from binder deterioration can retard the electrochemical performances of these cathodes. For this consideration, the nanotechnologies of cathode fabrication have opened up a new avenue in constructing a graphene cathode without any binder.…”