Role of Oxygen Vacancies on the Performance of Li[Ni0.5鈥?i>xMn1.5+x]O4 (x = 0, 0.05, and 0.08) Spinel Cathodes for Lithium-Ion Batteries

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• 作者：Jie Song ; Dong Wook Shin ; Yuhao Lu ; Charles D. Amos ; Arumugam Manthiram ; John B. Goodenough
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：August 14, 2012
• 年：2012
• 卷：24
• 期：15
• 页码：3101-3109
• 全文大小：690K
• 年卷期：v.24,no.15(August 14, 2012)
• ISSN：1520-5002

文摘

Investigation of the high-voltage Li[Ni_0.5鈥?i>xMn_1.5+x]O₄ (x = 0, 0.05, 0.08) spinels prepared at temperatures of T 鈮?900 掳C and given different thermal treatments has shown that the solubility limit for oxygen vacancies in the disordered spinel phase is small at 600 掳C. With x = 0, long-range ordering of Ni²⁺ and Mn⁴⁺ and elimination of all oxygen vacancies occurs after an anneal at 700 掳C. Above 700 掳C, a reversible transition from spinel to rock-salt is initiated, to accommodate oxygen loss. A sample quenched from 900 掳C into liquid nitrogen traps some rock-salt second phase; the volume fraction of rock-salt phase decreases with oxygen uptake to 600 掳C. However, upon slow cooling (1 掳C min^鈥?) from 900 掳C, the particles have time to eliminate most of the rock-salt phase by 700 掳C; upon further cooling below 700 掳C, the spinel phase and the oxygen gain are retained. However, the spinel phase retains oxygen vacancies and attendant Mn³⁺ with only short-range order of Ni and Mn. The rock-salt phase lowers sharply the electrochemical capacity of the quenched sample; but retention of Mn³⁺ in the slow-cooled sample improves the electrochemical performance relative to that of an oxygen-stoichiometric spinel formed by annealing at 700 掳C. The Mn-rich Li[Ni_0.45Mn_1.55]O₄ sample annealed at 700 掳C exhibits a segregation of a long-range-ordered spinel phase and a Ni-deficient spinel phase having a larger fraction near the particle surface. Removal of the Ni⁴⁺/Ni²⁺ redox reactions from the surface stabilizes the electrochemical performance at 55 掳C, but the problem of Mn²⁺ dissolution resulting from surface disproportionation of Mn³⁺ to Mn²⁺ and Mn⁴⁺ remains.

Keywords:

Li-ion battery; spinel to rock-salt transition; high-voltage cathode; der%E2%88%92disorder&qsSearchArea=searchText">order鈭抎isorder