多活性、高分散复合金属氧化物储锂机制、性能调控及放大化制备研究

Transition metal oxides (MO) with 3d electrons have been of genius interest in anode materials for lithium-ion batteries, due to their relatively high capacity. MO as potential anode materials, however, suffer from the problems of poor cycle stability and rate capability. One feature avenue of hybridizing MO/oxides structures has been demonstrated to be effective to improve the electrochemical performances. The possibilities of the resulting enhancements are, however, not yet clear, simply ascribed to the synergy of the bi-component structures. In our recent study, we have demonstrated that well-dispersed, bi-component-active CoO/CoFe2O4 nanocomposites, derived from scalably prepared single-resource CoFe-layered double hydroxide (CoFe-LDH) precursors, exhibit remarkably enhanced cycle performances and rate capabilities in comparison with the pristine individuals. We speculate that the homogenous dispersion and heterojunction structure of bi-component-active CoO and CoFe2O4 phases may underpin the enhancements. To confirm the hypothesis, we herein intend to utilize quasi-in situ XRD, atomic force/magnetic force microscopy, SEM/EDX, in combination with ex situ HRTEM/EDX and magnetic measurement, to clarify the conversion reaction mechanism in lithium ion batteries for CoO/CoFe2O4 nanocomposites, and then further tune the cycle performances and rate capabilities of the nanocomposites that are fairly readily derived from the MFe-LDH (M=Co, Ni, Cu) single-resource precursors. Our results will be able to elucidate unambiguously the conversion reaction mechanism in lithium ion batteries of bi-component active phases from a new perspective, and also provide a new approach to steer cycle performances and rate capabilities.

3d过渡金属氧化物（MO）作为潜在的高容量锂离子电池用负极材料备受关注，但在充放电前后其结构会发生较大变化，造成循环稳定性能差。与其他MO复合构筑纳米复合体系(M1O/M2O)是解决该问题的有效途径之一。但目前研究对于M1O/M2O体系储锂性能提高的具体原因尚不明晰。在前期工作中，我们以水滑石（LDHs）为单源前驱体，制备出双活性、高分散的CoO/CoFe2O4纳米复合体，发现其循环性能和倍率性能均优于单组分。我们推测性能提高的原因在于：双活性组分的高度均匀分散和二者之间形成的异质结结构。为了证实这一推测，在本申请项目中我们拟采用准原位XRD、原子力/磁力显微镜，非原位HRTEM等，研究该纳米复合体的储锂机制；并基于LDHs结构可调的特点，构筑高性能多活性的纳米复合体系；进一步与碳材料复合提高其倍率性能。本课题将从新的角度阐明纳米复合氧化物体系的储锂机制，并为其储锂性能的调控提供新途径。

本项目在发表论文、专利申报、人才培养等方面取得了一些成果，较全面地完成了研究内容。针对过渡金属氧化物作为锂离子电池用高容量电极材料存在循环稳定性差这一共性科学问题，本项目主要研究以层状水滑石（LDHs）为前体、以葡萄糖/插层表面活性剂为分子碳源，分别制备出比容量与循环性能显著提高的C-Ni@NiO/Al2O3、C@Ni3S2/Ni/Al2O3活性/非活性纳米复合物。所得到这两类活性/非活性纳米复合物，有利于储锂性能显著提高的结构与化学组成特点在于：i)焙烧过程中碳源和无定型Al2O3的限域作用，可改善NiAl-LDH前体及焙烧产物的纳米尺寸及均一分布；并可有效防止充放电过程中活性物质纳米颗粒的团聚，起到很好缓冲充放电过程中的体积膨胀；ii)导电性良好的镍和碳层的存在均能促进电子在活性物质纳米颗粒和电解质中的快速传递。本项目研究结果可望为锂离子电池用、负极材料–过渡金属化合物/碳复合材料–的设计和制备提供有益的借鉴，并为拓展LDHs基功能材料的应用提供一种新思路。