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Nanostructured LiMnO2 with Li3PO4 Integrated at the Atomic Scale for High-Energy Electrode Materials with Reversible Anionic Redox
ACS Central Science ( IF 12.7 ) Pub Date : 2020-12-15 , DOI: 10.1021/acscentsci.0c01200
Miho Sawamura 1 , Sho Kobayakawa 1 , Jun Kikkawa 2 , Neeraj Sharma 3 , Damian Goonetilleke 3 , Aditya Rawal 4 , Nanaka Shimada 5 , Kentaro Yamamoto 6 , Rina Yamamoto 6 , Yingying Zhou 6 , Yoshiharu Uchimoto 6 , Koji Nakanishi 7 , Kei Mitsuhara 7 , Koji Ohara 8 , Jiwon Park 9 , Hye Ryung Byon 9 , Hiroaki Koga 10, 11 , Masaki Okoshi 10, 11 , Toshiaki Ohta 7 , Naoaki Yabuuchi 5, 11, 12
Affiliation  

Nanostructured LiMnO2 integrated with Li3PO4 was successfully synthesized by the mechanical milling route and examined as a new series of positive electrode materials for rechargeable lithium batteries. Although uniform mixing at the atomic scale between LiMnO2 and Li3PO4 was not anticipated because of the noncompatibility of crystal structures for both phases, our study reveals that phosphorus ions with excess lithium ions dissolve into nanosize crystalline LiMnO2 as first evidenced by elemental mapping using STEM-EELS combined with total X-ray scattering, solid-state NMR spectroscopy, and a theoretical ab initio study. The integrated phase features a low-crystallinity metastable phase with a unique nanostructure; the phosphorus ion located at the tetrahedral site shares faces with adjacent lithium ions at slightly distorted octahedral sites. This phase delivers a large reversible capacity of ∼320 mA h g–1 as a high-energy positive electrode material in Li cells. The large reversible capacity originated from the contribution from the anionic redox of oxygen coupled with the cationic redox of Mn ions, as evidenced by operando soft XAS spectroscopy, and the superior reversibility of the anionic redox and the suppression of oxygen loss were also found by online electrochemical mass spectroscopy. The improved reversibility of the anionic redox originates from the presence of phosphorus ions associated with the suppression of oxygen dimerization, as supported by a theoretical study. From these results, the mechanistic foundations of nanostructured high-capacity positive electrode materials were established, and further chemical and physical optimization may lead to the development of next-generation electrochemical devices.

中文翻译:

原子尺度集成有Li 3 PO 4的纳米结构LiMnO 2用于可逆阴离子氧化还原的高能电极材料

通过机械铣削工艺成功合成了集成有Li 3 PO 4的纳米结构LiMnO 2,并将其作为可充电锂电池的新系列正极材料进行了研究。尽管由于两相晶体结构的不相容性,无法预期LiMnO 2和Li 3 PO 4在原子尺度上均匀混合,但我们的研究表明,具有过量锂离子的磷离子可溶解成纳米级晶体LiMnO 2,首先由元素证实使用STEM-EELS结合总X射线散射,固态NMR光谱和理论上的从头算图研究。集成相具有低结晶性亚稳态相,具​​有独特的纳米结构。位于四面体位置的磷离子与八面体稍微变形的相邻锂离子共享面。该相作为锂电池中的高能正极材料,可逆容量约为320 mA hg –1。大的可逆容量源自氧气的阴离子氧化还原与Mn离子的阳离子氧化还原的作用,如操作所证明的那样在线电化学质谱也发现了软XAS光谱,以及阴离子氧化还原的优异可逆性和氧损失的抑制作用。阴离子氧化还原的改善的可逆性源自理论研究支持的磷离子的存在与氧二聚化的抑制有关。从这些结果,建立了纳米结构高容量正极材料的机械基础,并且进一步的化学和物理优化可能导致下一代电化学装置的发展。
更新日期:2020-12-23
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