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

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 Mossbauer 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 Mossbauer 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 parallel to Li(1)Fe3+SiO4 and almost lithium-free "Li(0)Fe4+SiO4 parallel to 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 (similar to 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.

Thomas, JoshUppsala universitet,Strukturkemi(Swepub:uu)joshthom (författare)
Guo, JianghuaiXiamen Univ, Dept Chem, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China. (författare)
Yang, YongXiamen Univ, Dept Chem, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China. (författare)
Uppsala universitetStrukturkemi (creator_code:org_t)

Av författaren/redakt...: Liivat, Anti; Thomas, Josh; Guo, Jianghuai; Yang, Yong

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