Seher Julia, Fröba Michael
Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.
Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, 12205 Berlin, Germany.
ACS Omega. 2021 Sep 9;6(37):24062-24069. doi: 10.1021/acsomega.1c03432. eCollection 2021 Sep 21.
For the successful use of lithium-ion batteries in automotive applications, reliable availability of high storage capacity and very short recharging times are essential. In order to develop the perfect battery for a certain application, structure-property relationships of each active material must be fully understood. LiFePO is of great interest due to its fast-charging capability and high stability regarding its thermal resistance and chemical reactivity. The anisotropic lithium-ion diffusion through the LiFePO crystal structure indicates a strong dependence of the electrochemical performance of a nanostructured active material on particle morphology. In this paper, the relationship of the particle morphology and fast-charging capability of LiFePO/C core/shell nanoparticles in half-cells was studied. For this purpose, a new multistep synthesis strategy was developed. It involves the combination of a solvothermal synthesis followed by an polymer coating and thermal calcination step. Monodisperse rodlike LiFePO nanoparticles with comparable elongation along the -axis (30-50 nm) and a varying aspect ratio / (2.4-6.9) were obtained. A strong correlation of the fast-charging capability with the aspect ratio / was observed. When using LiFePO nanoparticles with the smallest aspect ratio /, the best electrochemical performance was received regarding the specific capacity at high C-rates and the cycling stability. A reduction of the aspect ratio / by 30% (3.6 to 2.4) was found to enhance the charge capacity at 10 C up to an order of magnitude (7.4-73 mA h·g).
为了使锂离子电池成功应用于汽车领域，高存储容量的可靠可用性和极短的充电时间至关重要。为了开发适用于特定应用的完美电池，必须充分了解每种活性材料的结构-性能关系。LiFePO因其快速充电能力以及在热阻和化学反应性方面的高稳定性而备受关注。锂离子通过LiFePO晶体结构的各向异性扩散表明，纳米结构活性材料的电化学性能强烈依赖于颗粒形态。本文研究了半电池中LiFePO/C核壳纳米颗粒的颗粒形态与快速充电能力之间的关系。为此，开发了一种新的多步合成策略。它包括溶剂热合成、聚合物涂层和热煅烧步骤的组合。获得了沿z轴具有可比伸长率（30-50 nm）且纵横比x/y变化范围为（2.4-6.9）的单分散棒状LiFePO纳米颗粒。观察到快速充电能力与纵横比x/y之间存在很强的相关性。当使用纵横比x/y最小的LiFePO纳米颗粒时，在高C倍率下的比容量和循环稳定性方面获得了最佳的电化学性能。发现纵横比x/y降低30%（从3.6降至2.4）可将10 C下的充电容量提高一个数量级（从7.4-73 mA h·g）。
