Interfacial Stabilization of Li₂O-Based Cathodes by Malonic-Acid-Functionalized Fullerenes as a Superoxo-Radical Scavenger for Suppressing Parasitic Reactions

Abstract

The utilization of an anionic redox reaction as an innovative strategy for overcoming the limitations of cathode capacity in lithium-ion batteries has recently been the focus of intensive research. Li2O-based materials using the anionic (oxygen) redox reaction have the potential to deliver a much higher capacity than commercial cathodes using cationic redox reactions based on transition-metal ions. However, parasitic reactions attributed to the superoxo species (such as LiO2), derived from the Li2O active material of the cathode, deteriorate the stability of the interface between the cathode and electrolyte, which has limited the commercialization of Li2O-based cathodes. To address this issue, malonic-acid-functionalized fullerenes (MC60) were applied in the electrolyte as an additive for scavenging the superoxo radicals (O2 1– in LiO2) that trigger parasitic reactions. MC60 can efficiently capture superoxo radicals using the π-conjugated surface and the malonate functionality on the surface. As a result, MC60 considerably enhanced the available capacity and cycling performance of the Li2O-based cathodes, decreased the interfacial layer formed on the cathode surface, and hindered the generation of byproducts, such as Li2CO3, CO2, and C–F3, derived from parasitic reactions. In addition, the loss of Li2O from the cathode surface during cycling was also suppressed, validating the ability of MC60 to capture superoxo radicals. This result confirms that the introduction of MC60 can effectively alleviate the parasitic reactions at the cathode/electrolyte interface and improve the electrochemical performance of Li2O-based cathodes by scavenging the superoxo species.

C60 and Derivatives Boost Electrocatalysis and Photocatalysis: Electron Buffers to Heterojunctions

“…Functionalized fullerenes, therefore, have utility in a range of applications including, but not limited to, photocatalysis, electrocatalysis, polymer solar cells, photovoltaics, environmental remediation, and pharmaceuticals. [29][30][31][32][33][34] Fullerenes are generally functionalized via "bottom-up" and "topdown" methodologies, together with synthetic processes and anchoring of motifs. Manipulation of fullerenes via supramolecular self-assembly and functionalization, grafting, doping with metallic and non-metallic heteroatoms, polymer coatings, noncovalent modification of 2D materials and nano-attachment reportedly enables precise regulation of material surface and overall characteristics.…”

Improving Interfacial Stability for All-Solid-State Secondary Batteries with Precursor-Based Gradient Doping

“…In recent years, the adoption of Li-ion secondary batteries (LIBs) in electric vehicles and energy storage systems has rapidly increased in scale and prominence, − resulting in a significant increase in the concomitant safety concerns. Human casualties owing to battery explosions and fires have limited the widespread adoption of LIB-based electric vehicles.…”

Chemical compatibility of polymer binders with a reversible anionic redox reaction in lithia-based cathodes

“…Superoxol species cause undesirable side reactions that deteriorate the cycle performance of lithia-based cathodes. 17 The side reactions may occur during the preparation of the electrode with a polymeric binder, in addition to inside the assembled battery cell, because the lithia-based cathode itself contains reduced oxygen species (e.g., O 2− or O − ) that can attack polymers. 18 Therefore, to harness both the high energy density from oxygen vacancy enhancement and the facile production of electrodes by solution-based casting, it is essential to choose a suitable polymeric binder that is compatible with reversible anion redox in lithia-based cathodes.…”

“…Superoxol species cause undesirable side reactions that deteriorate the cycle performance of lithia-based cathodes. 17 The side reactions may occur during the preparation of the electrode with a polymeric binder, in addition to inside the assembled battery cell, because the lithia-based cathode itself contains reduced oxygen species ( e.g. , O 2− or O − ) that can attack polymers.…”