Zheng Zhiming, Wu Hong-Hui, Liu Haodong, Zhang Qiaobao, He Xin, Yu Sicen, Petrova Victoria, Feng Jun, Kostecki Robert, Liu Ping, Peng Dong-Liang, Liu Meilin, Wang Ming-Sheng
Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen, Fujian 361005, China.
Beijing Advanced Innovation Center for Materials Genome Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China.
ACS Nano. 2020 Aug 25;14(8):9545-9561. doi: 10.1021/acsnano.9b08575. Epub 2020 Jul 23.
Conversion-type transition-metal phosphide anode materials with high theoretical capacity usually suffer from low-rate capability and severe capacity decay, which are mainly caused by their inferior electronic conductivities and large volumetric variations together with the poor reversibility of discharge product (LiP), impeding their practical applications. Herein, guided by density functional theory calculations, these obstacles are simultaneously mitigated by confining amorphous FeP nanoparticles into ultrathin 3D interconnected P-doped porous carbon nanosheets (denoted as FeP@CNs) a facile approach, forming an intriguing 3D flake-CNs-like configuration. As an anode for lithium-ion batteries (LIBs), the resulting FeP@CNs electrode not only reaches a high reversible capacity (837 mA h g after 300 cycles at 0.2 A g) and an exceptional rate capability (403 mA h g at 16 A g) but also exhibits extraordinary durability (2500 cycles, 563 mA h g at 4 A g, 98% capacity retention). By combining DFT calculations, transmission electron microscopy, and a suite of microscopic and spectroscopic techniques, we show that the superior performances of FeP@CNs anode originate from its prominent structural and compositional merits, which render fast electron/ion-transport kinetics and abundant active sites (amorphous FeP nanoparticles and structural defects in P-doped CNs) for charge storage, promote the reversibility of conversion reactions, and buffer the volume variations while preventing pulverization/aggregation of FeP during cycling, thus enabling a high rate and highly durable lithium storage. Furthermore, a full cell composed of the prelithiated FeP@CNs anode and commercial LiFePO cathode exhibits impressive rate performance while maintaining superior cycling stability. This work fundamentally and experimentally presents a facile and effective structural engineering strategy for markedly improving the performance of conversion-type anodes for advanced LIBs.
具有高理论容量的转换型过渡金属磷化物负极材料通常存在倍率性能低和严重的容量衰减问题，这主要是由于其较差的电子导电性、较大的体积变化以及放电产物（LiP）的可逆性差所致，阻碍了它们的实际应用。在此，在密度泛函理论计算的指导下，通过一种简便的方法将非晶态FeP纳米颗粒限制在超薄的三维互连P掺杂多孔碳纳米片中（表示为FeP@CNs），同时缓解了这些障碍，形成了一种有趣的三维片状-CNs状结构。作为锂离子电池（LIBs）的负极，所得的FeP@CNs电极不仅在0.2 A g下循环300次后达到了高可逆容量（837 mA h g）和优异的倍率性能（在16 A g下为403 mA h g），而且还表现出非凡的耐久性（2500次循环，在4 A g下为563 mA h g，容量保持率为98%）。通过结合DFT计算、透射电子显微镜以及一系列微观和光谱技术，我们表明FeP@CNs负极的优异性能源于其突出的结构和组成优点，这些优点使得电子/离子传输动力学快速且具有丰富的电荷存储活性位点（非晶态FeP纳米颗粒和P掺杂CNs中的结构缺陷），促进了转换反应的可逆性，并在循环过程中缓冲了体积变化，同时防止了FeP的粉化/团聚，从而实现了高倍率和高耐久性的锂存储。此外，由预锂化的FeP@CNs负极和商用LiFePO正极组成的全电池在保持优异循环稳定性的同时表现出令人印象深刻的倍率性能。这项工作从根本上并通过实验提出了一种简便有效的结构工程策略，用于显著提高先进LIBs转换型负极的性能。
