变废为宝:富缺陷镍掺杂磷酸铁锂用于高效电催化析氧反应

Waste to wealth:Defect-rich Ni-incorporated spent LiFePO_(4)for efficient oxygen evolution reaction

在电池废弃物可持续管理中,锂离子电池(LIB)电极材料的高效回收是一个重要而又具有挑战性的工作.本文报道了一种简单且经济有效的方法,将废旧电池正极材料磷酸铁锂(LiFePO_(4))转化为高性能的镍铁氧/氢氧化物(NiFeOxHy)催化剂用于析氧反应(oxygen evolution reaction,OER).采用湿法浸渍合成的Ni-LiFePO_(4)在电化学氧化过程中进一步转变成了富缺陷的NiFeOxHy纳米片.镍促进剂的引入和前驱物形貌的原位转化增强了金属位点之间的电子相互作用,同时产生了大量的缺陷.电化学测试结果表明,转化后的Ni-LiFePO_(4)在10 mA cm^(-2)电流密度下的过电位仅为285 mV,Tafel斜率为45 mV dec^(-1),优于前驱物LiFePO_(4),甚至优于基准贵金属催化剂RuO_(2).密度泛函理论(density functional theory,DFT)计算表明,Ni的引入优化了*OOH中间体的自由能,从而有效激活了Fe位点;而丰富的氧缺陷促进了氧解吸步骤,二者协同提高了LiFePO_(4)的催化析氧反应性能.作为一种绿色和通用的方法,该研究为基于废旧电池材料规模化制备优良电催化剂提供了新的机遇.

The development of efficient strategies to recycle lithium-ion battery(LIB)electrode materials is an important yet challenging goal for the sustainable management of battery waste.This work reports a facile and economically efficient method to convert spent cathode material,LiFePO_(4),into a high-performance NiFe oxy/hydroxide catalyst for the oxygen evolution reaction(OER).Herein,Ni-LiFePO_(4)is synthesized via the wetness impregnation method and further evolves into defect-rich NiFe oxy/hydroxide nanosheets during the OER.The introduction of the Ni promoter together with in situ evolution strengthens the electronic interactions among the metal sites and creates an abundance of defects.Experimentally,the evolved Ni-LiFePO_(4)delivers a low overpotential of 285 mV at 10 mA cm-^(2)and a small Tafel slope of 45 mV dec^(-1),outperforming pristine LiFePO_(4)and is even superior to the benchmark catalyst RuO_(2).Density functional theory(DFT)calculations reveal that the introduction of Ni effectively activates Fe sites by optimizing the free energy of the*OOH intermediate and that the abundance of oxygen defects facilitates the oxygen desorption step,synergistically enhancing the OER performance of LiFePO_(4).As a green and versatile method,this is a new opportunity for the scalable fabrication of excellent electrocatalysts based on spent cathode materials.