第一性原理研究硼掺杂氧化石墨烯对过氧化锂氧化反应的催化机理

First-principles study of catalytic mechanism of boron-doped graphene oxide on oxygen evolution reaction of lithium peroxide

锂-氧电池由于高能量密度在后锂离子电池中脱颖而出,而放电产物过氧化锂缓慢的氧化反应降低了电池的循环性能.因此,提高过氧化锂氧化反应动能、降低充电过电位对于实现高能量密度的可逆锂-氧电池具有重要意义.本文通过第一性原理计算,对比研究了氧化石墨烯(GO)和硼掺杂氧化石墨烯(BGO)对过氧化锂小团簇(Li_(2)O_(2))_(2)氧化反应的催化机理.结果表明,从(Li_(2)O_(2))_(2)团簇转移到GO和BGO上的电荷分别为0.59 e和0.96 e,B掺杂提高了电荷转移.4电子反应过程表明,(Li_(2)O_(2))_(2)团簇倾向于Li-O_(2)-Li分解路径,在GO和BGO上反应的速率决定步均是第三步去锂.在平衡电位下,GO和BGO的充电过电位分别是0.76 V和0.23 V,B掺杂大大降低了锂-氧电池充电过电位.机理分析表明B与O对(Li_(2)O_(2))_(2)团簇起到了协同催化的作用.

Lithium-oxygen batteries stand out among post-lithium-ion batteries due to their theoretically high energy density,while the sluggish reaction kinetics of lithium peroxide reduces the rate performance of the batteries.Therefore,improving the reaction kinetics of the lithium peroxide and then lowering the charge overpotential are of great importance for realizing reversible lithium-oxygen batteries with high energy density.In this work,the catalytic mechanism of graphene oxide(GO)and boron-doped graphene oxide(BGO)on the oxygen evolution reaction of(Li_(2)O_(2))_(2) cluster is investigated by first-principles calculations.The results show that the charge transfer from(Li_(2)O_(2))_(2) cluster to GO and from(Li_(2)O_(2))_(2) cluster to BGO are 0.59 e and 0.96 e,respectively,suggests that B doping improves the charge transfer from the discharged product to the cathode material.The Gibbs free energy of the 4-electron decomposition process shows that the(Li_(2)O_(2))_(2) cluster favors the Li-O_(2)-Li decomposition pathway,and the rate-determining step for the reaction on both GO and BGO is the third step,that is,the removal of the third lithium.At the equilibrium potential,the charge overpotential of GO and BGO are 0.76 V and 0.23 V,respectively,showing that B doping greatly reduces the charging overpotential of lithium-oxygen batteries.Moreover,mechanistic analysis shows that B doping enhances the electronic conductance of GO and forms an electron-deficient active center,which facilitates charge transport in cathode and charge transfer from lithium peroxide to cathode materials,thereby reducing the charging overpotential of the lithium-oxygen batteries and improving its cycling performance.The B and O play a synergistic role in catalyzing the oxygen evolution reaction of(Li_(2)O_(2))_(2) clusters.