Polymeric redox mediator as a stable cathode catalyst for lithium-O2 batteries

Redox-Mediated Polymer Catalyst for Lithium-Air Batteries with High Round-Trip Efficiency

“…The mechanism of the decomposition of Li 2 O 2 based on iodide can be described by the following steps [26]: Even so, it is not that iodine does not contribute to the chemical reactions. Note that based on our previously reported result [21], it was revealed that during the cycle, the state of iodine can be changed into the iodide (I − ) state by the reduction reaction, contributing to the catalytic reaction.…”

“…In this regard, redox-mediated polymer catalysts (RPCs), in which the polymer and RMs are chemically bonded, have been recently proposed and received considerable attention [21]. Such the RPCs can be expected to enable bi-functional materials capable of simultaneously performing the role of catalyst and binder.…”

Stabilizing Li Anodes in I2 Steam to Tackle the Shuttling-Induced Depletion of an Iodide/Triiodide Redox Mediator in Li–O2 Batteries with Suppressed Li Dendrite Growth

“…Similarly, XPS data revealed that the LiI-protected Li after cycling consisted of LiI (at ∼55.4 eV) and LiF (at ∼56.2 eV) based on the observation of Li 1s spectra (Figure 3b). 58 A small quantity of LiF should be attributed to the decomposing TFSI − in the electrolyte, while the trace amount of I 2 is due to physical absorption. After five cycles, as seen in Figure 3c, the intensity ratio of LiI to I 2 peak for the LiI-protected Li anode (0.879) was higher than that for the pristine Li anode (0.467), suggesting that the LiI protective layer exhibits durable (electro)chemical stability and resistance to being dissolved by the electrolyte, which is consistent with previous observations (Figure S2).…”

“…For the Li anode after cycling, the peaks related to LiI at ∼55.4 eV and LiF at ∼56.5 eV were detected from Li 1s spectra, and the other two peaks located at 50.9 and 49.2 eV were attributed to I 4d 2/3 and I 4d 5/2 , respectively. , This result confirmed that the surface of the Li metal was easily corroded by the RM with the oxidation state (I 3 – ) to generate the LiI byproduct (Figure a). Similarly, XPS data revealed that the LiI-protected Li after cycling consisted of LiI (at ∼55.4 eV) and LiF (at ∼56.2 eV) based on the observation of Li 1s spectra (Figure b) . A small quantity of LiF should be attributed to the decomposing TFSI – in the electrolyte, while the trace amount of I 2 is due to physical absorption.…”

“…It is also beneficial to control the amount of the electrolyte used in Li–O 2 batteries, and a lower dosage would be better. In addition, for I 3d spectra, two doublets related to I – (630.8 and 619.2 eV) and I 2 (632.5 and 620.5 eV) were both observed for the pristine Li and LiI-protected Li anode (Figure d,e), proving the presence of LiI and I 2 on the surface of both Li anodes after cycling. , However, it is worth pointing out that the relative content of LiI for the pristine Li anode after five cycles (89.56%) was almost as high as that of the LiI-protected Li anode (94.44%), as shown in Figure f. This result suggested a significant corrosion of the Li metal, which further demonstrated that the shuttling of triiodide (I 3 – ) readily reacted with the bare Li metal to form the LiI byproduct, thus inducing a rapid depletion of the I – /I 3 – redox mediator in the electrolyte.…”