Oxygen evolution from olivine Mn1−xMxPO4

Abstract

Olivine LiMnPO 4 is a promising cathode material for Li-ion batteries. One drawback of this material is the propensity of its delithiated phase, MnPO 4 , to evolve oxygen gas above approximately 200 °C. During thermal runaway of cells, this oxygen gas can burn the electrolyte and other cell components and thereby jeopardize safety. Partial substitution of Mn with M' = Fe, Ni, Al, or Mg has been used to improve the lithium intercalation kinetics of Li x MnPO 4 ; however, the effect of these substitutions on oxygen evolution is not fully documented. In this paper, we calculate phase diagrams and oxygen evolution diagrams for these Mn 1-x M' x PO 4 delithiated cathode materials. To generate the phase diagrams, we use sub-regular solid solution models and fit the energetic parameters of these models to density functional theory calculations of special quasi-random structures. The resulting thermodynamic models describe the effect of mixing on the initial temperature of oxygen evolution and on the cumulative amount of oxygen evolution at elevated temperatures. We find that addition of Fe increases the initial temperature and decreases the cumulative amount of oxygen evolution. Mn 0.5 Fe 0.5 PO 4 exhibits an initial temperature 50 °C higher than MnPO 4 and releases 70% less oxygen gas at 300 °C. Al is insoluble in MnPO 4 , so addition of Al has no affect on the initial temperature. However, Al addition does slightly decrease the amount of oxygen evolution due to an inactive AlPO 4 component. Mg and Ni both decrease the initial temperature of oxygen evolution, and therefore may worsen the safety of MnPO 4 .

Electrochemically Stable Coating Materials for Li, Na, and Mg Metal Anodes in Durable High Energy Batteries

“…[19][20][21][22][23][24][25][26][27] High-throughput materials databases have recently enabled density functional theory to be applied to large numbers of compounds to find attractive materials for a variety of applications. [25][26][27][28][29] Recent work by Ceder et al has examined the thermodynamic stability of known electrolyte materials including electrode-electrolyte reactivity.…”

First principles study of electrocatalytic behavior of olivine phosphates with mixed alkali and mixed transition metal atoms

“…6 There are many recent studies on mixed transition metal olivine systems (LiM 1Àx M 0 x PO 4 ; M and M 0 ¼ Fe, Ni, Co, Mn) by various group which have shown ability to overcome these issues. [7][8][9][10][11][12][13] Beyond this, the olivine phosphates are also known as good electrocatalyst for oxygen evolution reactions (OER). [14][15][16][17] Excellent OER electrocatalysts, such as ruthenium, iridium and their oxides exist, but these are costly, [18][19][20][21][22][23] and there is an ongoing search for non-noble metal catalysts for OER.…”