Novel insights into higher capacity from the Li-ion battery cathode material Li₂FeSiO₄

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• 作者：Anti Liivat^a ; ^{anti.liivat@kemi.uu.se} ; Josh Thomas^a ; Jianghuai Guo^b ; Yong Yang^b
• 关键词：Lithium-ion batteries ; positive electrode ; Li2FeSiO4 ; in situ Mö ; ssbauer spectroscopy ; Fe4+
• 刊名：Electrochimica Acta
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：223
• 期：Complete
• 页码：109-114
• 全文大小：1468 K
• 卷排序：223

文摘

A highly reactive composite cathode material incorporating nano-particles of the popular Li-ion battery cathode material Li2FeSiO4 (LFS) is here studied to probe the activation of the controversial Fe3+/Fe4+ redox couple in exploiting the second Li-ion in the formula unit – for use in rechargeable Li-ion batteries. A novel form of in situ Mössbauer spectroscopy is used to monitor the oxidation state of the Fe-ions in symmetric LFS || LFS cells. This is based on mapping the poorly resolvable Mössbauer spectra from the expected Fe3+/Fe4+ redox couple in the working electrode onto the highly resolvable Fe2+/Fe3+ spectra from the counter electrode. Comparison of such data from half-delithiated Li(1)Fe3+SiO4 || Li(1)Fe3+SiO4 and almost lithium-free “Li(0)Fe4+SiO4 || Li(0)Fe4+SiO4” symmetric cells is demonstrated – to distinguish the electrode reactions from the those involving the electrolyte. Lithium is shown to cycle reversibly in the symmetric cells. However, a large proportion of the cycled lithium (∼70%) does not derive from the bulk of the electrodes, but is rather a result of high-V electrolyte degradation, where charge balance is maintained by leaching lithium from the electrolyte and inserting it into the electrodes.