State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences , Shanghai 200050 China.
University of Chinese Academy of Sciences , Beijing 100039 China.
ACS Nano. 2017 Apr 25;11(4):3705-3715. doi: 10.1021/acsnano.6b08223. Epub 2017 Mar 24.
In search of new electrode materials for lithium-ion batteries, metal phosphides that exhibit desirable properties such as high theoretical capacity, moderate discharge plateau, and relatively low polarization recently have attracted a great deal of attention as anode materials. However, the large volume changes and thus resulting collapse of electrode structure during long-term cycling are still challenges for metal-phosphide-based anodes. Here we report an electrode design strategy to solve these problems. The key to this strategy is to confine the electroactive nanoparticles into flexible conductive hosts (like carbon materials) and meanwhile maintain a monodispersed nature of the electroactive particles within the hosts. Monodispersed carbon-coated cubic NiP nanoparticles anchored on carbon nanotubes (NiP@C-CNTs) as a proof-of-concept were designed and synthesized. Excellent cyclability (more than 1000 cycles) and capacity retention (high capacities of 816 mAh g after 1200 cycles at 1300 mA g and 654.5 mAh g after 1500 cycles at 5000 mA g) are characterized, which is among the best performance of the NiP anodes and even most of the phosphide-based anodes reported so far. The impressive performance is attributed to the superior structure stability and the enhanced reaction kinetics incurred by our design. Furthermore, a full cell consisting of a NiP@C-CNTs anode and a LiFePO cathode is investigated. It delivers an average discharge capacity of 827 mAh g based on the mass of the NiP anode and exhibits a capacity retention of 80.7% over 200 cycles, with an average output of ∼2.32 V. As a proof-of-concept, these results demonstrate the effectiveness of our strategy on improving the electrode performance. We believe that this strategy for construction of high-performance anodes can be extended to other phase-transformation-type materials, which suffer a large volume change upon lithium insertion/extraction.
在寻找锂离子电池的新型电极材料时，具有高理论容量、适中的放电平台和相对较低的极化等理想特性的金属磷化物作为阳极材料引起了极大的关注。然而，在长期循环过程中，电极结构的巨大体积变化和由此导致的坍塌仍然是基于金属磷化物的阳极面临的挑战。在这里，我们报告了一种解决这些问题的电极设计策略。该策略的关键是将活性纳米颗粒限制在柔性导电主体（如碳材料）中，并同时保持活性颗粒在主体中的单分散性。作为概念验证，设计并合成了单分散碳包覆立方 NiP 纳米颗粒锚定在碳纳米管上（NiP@C-CNTs）。优异的循环稳定性（超过 1000 次循环）和容量保持率（在 1300 mA g 下 1200 次循环后高达 816 mAh g，在 5000 mA g 下 1500 次循环后高达 654.5 mAh g），这是迄今为止 NiP 阳极甚至大多数磷化物基阳极的最佳性能之一。令人印象深刻的性能归因于我们设计的卓越结构稳定性和增强的反应动力学。此外，还研究了由 NiP@C-CNTs 阳极和 LiFePO 阴极组成的全电池。基于 NiP 阳极的质量，它提供了 827 mAh g 的平均放电容量，并在 200 次循环中具有 80.7%的容量保持率，平均输出约为 2.32 V。作为概念验证，这些结果证明了我们提高电极性能的策略的有效性。我们相信，这种构建高性能阳极的策略可以扩展到其他在锂插入/提取过程中经历大体积变化的相变型材料。
