Monodispersed Ru Nanoparticles Functionalized Graphene Nanosheets as Efficient Cathode Catalysts for O₂-Assisted Li–CO₂ Battery

Abstract

In Li–CO 2 battery, due to the highly insulating nature of the discharge product of Li 2 CO 3 , the battery needs to be charged at a high charge overpotential, leading to severe cathode and electrolyte instability and hence poor battery cycle performance. Developing efficient cathode catalysts to effectively reduce the charge overpotential represents one of key challenges to realize practical Li–CO 2 batteries. Here, we report the use of monodispersed Ru nanoparticles functionalized graphene nanosheets as cathode catalysts in Li–CO 2 battery to significantly lower the charge overpotential for the electrochemical decomposition of Li 2 CO 3 . In our battery, a low charge voltage of 4.02 V, a high Coulomb efficiency of 89.2%, and a good cycle stability (67 cycles at a 500 mA h/g limited capacity) are achieved. It is also found that O 2 plays an essential role in the discharge process of the rechargeable Li–CO 2 battery. Under the pure CO 2 environment, Li–CO 2 battery exhibits negligible discharge capacity; however, after introducing 2% O 2 (volume ratio) into CO 2 , the O 2 -assisted Li–CO 2 battery can deliver a high capacity of 4742 mA h/g. Through an in situ quantitative differential electrochemical mass spectrometry investigation, the final discharge product Li 2 CO 3 is proposed to form via the reaction 4Li + + 2CO 2 + O 2 + 4e – → 2Li 2 CO 3 . Our results validate the essential role of O 2 and can help deepen the understanding of the discharge and charge reaction mechanisms of the Li–CO 2 battery.

High‐Performance, Long‐Life, Rechargeable Li–CO2 Batteries based on a 3D Holey Graphene Cathode Implanted with Single Iron Atoms

“…The sluggish CO 2 reduction and evolution reactions that take place at the air cathode often impede the kinetics of Li–CO 2 batteries, leading to a high voltage (>4.5 V vs Li/Li + ) for decomposing the discharge product (Li 2 CO 3 ). [ 5–7 ] Under such a high anodic potential, the electrolyte oxidation limits the energy efficiency and cycling life of the Li–CO 2 batteries. [ 5–7 ] Therefore, efficient and robust cathode catalysts are required to promote their energy efficiency and cycle life by facilitating the reversible formation and decomposition of Li 2 CO 3 during the discharge/charge processes in Li–CO 2 batteries.…”

“…[ 5–7 ] Under such a high anodic potential, the electrolyte oxidation limits the energy efficiency and cycling life of the Li–CO 2 batteries. [ 5–7 ] Therefore, efficient and robust cathode catalysts are required to promote their energy efficiency and cycle life by facilitating the reversible formation and decomposition of Li 2 CO 3 during the discharge/charge processes in Li–CO 2 batteries. [ 6,8 ]…”

Progress and Future Perspectives on Li(Na)–CO2 Batteries

“…Chen et al also reported a low charge potential of 4.02 V and a good cycle stability (67 cycles with a fixed capacity of 500 mAh g −1 ) in the O 2 -assisted Li−CO 2 battery with the Ru/graphene nanosheets cathode. [62] That is to say, the presence of Ru helps to reduce the charge potential, which can avoid electrolyte decomposition in the operating potential range, and the Li-CO 2 cells can achieve excellent reversibility. Recently, Zhang et al indicated that the highly dispersed Ni nanoparticles on N-doped graphene (Ni-NG) could be used as an efficient cathode for Li-CO 2 batteries, with a discharge capacity of 17 625 mAh g −1 , and a cycle life of 100 cycles with a cutoff capacity of 1000 mAh g −1 at 100 mA g −1 .…”

Defect Chemistry in Discharge Products of Li–O2 Batteries

“…The Li–O 2 /CO 2 batteries with high capacity provided a possibility to operate with Li 2 CO 3 as the main energy carrier, first proposed by Albertus et al Upon discharging, the total reaction is 4Li + + 4e − + 2CO 2 + O 2 → 2Li 2 CO 3 , where the number of electrons consumed per mole of gas is confirmed by DEMS . Yin et al investigated the discharge processes of Li–O 2 /CO 2 batteries (70%/30%), with Li 2 CO 3 as the final discharge product, in two solvents DMSO (DN = 29.8) and DME (DN = 24) .…”