Engineering the Transformation Strain in LiMnyFe1–yPO4 Olivines for Ultrahigh Rate Battery Cathodes

详细信息    查看全文

• 作者：Dorthe B. Ravnsbæk ; Kai Xiang ; Wenting Xing ; Olaf J. Borkiewicz ; Kamila M. Wiaderek ; Paul Gionet ; Karena W. Chapman ; Peter J. Chupas ; Ming Tang ; Yet-Ming Chiang
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：April 13, 2016
• 年：2016
• 卷：16
• 期：4
• 页码：2375-2380
• 全文大小：598K
• 年卷期：0
• ISSN：1530-6992

文摘

Alkali ion intercalation compounds used as battery electrodes often exhibit first-order phase transitions during electrochemical cycling, accompanied by significant transformation strains. Despite ∼30 years of research into the behavior of such compounds, the relationship between transformation strain and electrode performance, especially the rate at which working ions (e.g., Li) can be intercalated and deintercalated, is still absent. In this work, we use the LiMn_yFe_1–yPO₄ system for a systematic study, and measure using operando synchrotron radiation powder X-ray diffraction (SR-PXD) the dynamic strain behavior as a function of the Mn content (y) in powders of ∼50 nm average diameter. The dynamically produced strain deviates significantly from what is expected from the equilibrium phase diagrams and demonstrates metastability but nonetheless spans a wide range from 0 to 8 vol % with y. For the first time, we show that the discharge capacity at high C-rates (20–50C rate) varies in inverse proportion to the transformation strain, implying that engineering electrode materials for reduced strain can be used to maximize the power capability of batteries.