Design Of LaCoO₃-based Oxygen Electrocatalyst And Its Application In Zn-air Battery

Zinc-air batteries are considered to be one of the most promising sustainable energy storage and conversion devices in new mobile power sources and electronics,and has attracted much attention in the equipment application field,due to high energy density（theoretical specific energy density is as high as 1084 Wh/kg,which is 2-3 times that of current lithium-ion batteries）,economy and high safety.Oxygen evolution reaction（OER）and oxygen reduction reaction（ORR）are two important reactions that occur at the air cathode,but the multi-step electron transfer in the reaction process will cause the slow reaction kinetics,reduce its reaction efficiency,and seriously affect the battery performance.Although,noble metal-based catalysts can accelerate the oxygen electrocatalytic reaction rate and increase the energy conversion rate,but their scarce materials and unsatisfactory stability hinder its large-scale industrial production.Therefore,researching and developing low-cost,high-efficiency,high-stability non-noble metal dual-functional catalysts and revealing the catalytic reaction mechanism is the top priority of the current research on zinc-air batteries.Lanthanum cobaltate（La Co O₃）is considered to be one of the most potential materials to replace precious metal-based catalysts due to its unique and controllable electronic structure.In this paper,a series of La Co O₃-based perovskite oxide catalysts were prepared by the sol-gel method,using non-metal atom doping,constructing heterojunctions and other strategies.The mechanism of the oxygen electrocatalytic performance improvement of the material is explained and discussed,adopting ion spin states,oxygen defects,metal-oxygen hybridization and other theories,which also provides a new perspective for the application of other perovskite oxide materials to zinc-air batteries.The main research methods and conclusions of this paper are as follows:1.Doping with non-metallic elements（N,P,S）replaces part of the oxygen atoms of lanthanum cobaltate（La Co O₃）and forms oxygen defects,causing the Co O₆octahedron to undergo Jahn-Teller distortion,thereby making the Co³⁺ions of La Co O₃transform from the low spin state（LS）to the intermediate spin state（IS）,which optimized its oxygen electrocatalytic and Zn-air battery performance.The study found that N-doped La Co O₃ exhibits an OER overpotential of 1.69 V at a current density of50 m A/cm²,and its ORR limiting current density can reach 5.78 m A/cm².In addition,the S-doped La Co O₃ assembled liquide rechargeable zinc-air battery has high power density（92 m W/cm²）,excellent charge/discharge stability（100 h stable cycle）and large open circuit voltage（1.47 V）.2.Using the non-stoichiometric ratio of the precursors,the sol-gel method was used to prepare Co₃O₄@La Co O₃ catalysts with different phase ratios in one step.Compared with single-phase Co₃O₄ and La Co O₃,dual-phase Co₃O₄@La Co O₃ has better electrocatalysis and Zn-air battery performance.When the current density reaches 10 m A/cm²,Co₃O₄@La Co O₃ has better electrocatalysis and battery performance.Small overpotential（320 mv）and lower Tafel slope（135.4 m V/de）for OER.The results of first-principles calculations show that the improvement of material performance is due to the charge transfer of the interface and the regulation of the d electronic state of Co ion by interface effect.The liquid rechargeable Zn-air battery assembled based on the Co₃O₄@La Co O₃ electrode can provide a large open circuit voltage of 1.46 V,a high specific capacity of 785 m Ah/g _Zn,a power density of 140m W/cm² and excellent cycle stability for more than 555 cycles.