Hendriks Ron, Cunha Daniel Monteiro, Singh Deepak Pratap, Huijben Mark
MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, Enschede, Netherlands.
ACS Appl Energy Mater. 2018 Dec 24;1(12):7046-7051. doi: 10.1021/acsaem.8b01477. Epub 2018 Nov 19.
A promising cathode material for rechargeable batteries is LiMnO, which exhibits higher operating voltage, reduced toxicity and lower costs as compared to commonly used LiCoO cathodes. However, LiMnO suffers from limited cycle life, as excessive capacity fading occurs during battery cycling due to dissolution of Mn into the acidic electrolyte. Here, we show that by structural engineering of stable, epitaxial LiMnO thin films the electrochemical properties can be enhanced as compared to polycrystalline samples. Control of the specific crystal orientation of the LiMnO thin films resulted in dramatic differences in surface morphology with pyramidal, rooftop or flat features for respectively (100), (110), and (111) orientations. All three types of LiMnO films expose predominantly ⟨111⟩ crystal facets, which is the lowest energy state surface for this spinel structure. The (100)-oriented LiMnO films exhibited the highest capacities and (dis)charging rates up to 33C, and good cyclability over a thousand cycles, demonstrating enhanced cycle life without excessive capacity fading as compared to previous polycrystalline studies.
一种很有前景的可充电电池阴极材料是LiMnO，与常用的LiCoO阴极相比，它具有更高的工作电压、更低的毒性和成本。然而，LiMnO的循环寿命有限，因为在电池循环过程中，由于Mn溶解到酸性电解质中，会出现过度的容量衰减。在此，我们表明，通过对稳定的外延LiMnO薄膜进行结构工程，与多晶样品相比，其电化学性能可以得到增强。对LiMnO薄膜特定晶体取向的控制导致表面形态出现显著差异，分别对应(100)、(110)和(111)取向的薄膜具有金字塔形、屋顶形或平坦特征。所有这三种类型的LiMnO薄膜主要暴露⟨111⟩晶面，这是这种尖晶石结构的最低能量状态表面。(100)取向的LiMnO薄膜表现出最高的容量和高达33C的充放电速率，并且在超过一千次循环中具有良好的循环性能，与之前的多晶研究相比，显示出更长的循环寿命且没有过度的容量衰减。
