Influence of the Structure on the Electrochemical Performance of Lithium Transition Metal Phosphates as Cathodic Materials in Rechargeable Lithium Batteries:  A New High-Pressure Form of LiMPO₄ (M = Fe and Ni)

Abstract

Materials built from MO6 octahedra linked to XO4 tetrahedra are good candidates for studying the different factors that determine the electrode potential. Among them, olivine-like LiMPO4 (M = transition metal) phosphates are especially interesting. When pressure is applied to LiMPO4 (M = Ni and Fe), a phase transition is induced. However, instead of the well-known olivine ⇔ spinel transformation, a transition to a new phase is observed (β‘). The arrangements of the metal ions (including phosphorus) in the two structures are very similar; thus, the main difference between them is due to the oxygen arrangement in a similar matrix. Raman spectroscopy has confirmed the structural model proposed for the high-pressure phase, in particular the modification in the lithium coordination from 6- to 4-fold upon synthesis under pressure. Among the olivines LiMPO4 (M = Mn, Ni, and Fe), the iron-containing one is only active up to 5.1 V. On the other hand, none of the high-pressure materials is electrochemically active; this can be explained by the change in the electrostatic field at the transition metal position.

A first-principles study on Si24 as an anode material for rechargeable batteries

“…Moreover, high-pressure induced phase transformations of several electrode materials, e.g., Li x MPO 4 (M ¼ Fe and Co), 8,9 16 In addition to these high-pressure polymorphs of current electrode materials, many novel alkali compounds with an open-channel structure have been derived at high pressure. 12,[17][18][19] It has been proven that these channels likely provide a diffusion path for the alkali ions and lead to high ionic conductivities.…”

Effect of the high pressure on the structure and intercalation properties of lithium–nickel–manganese oxides

“…High-pressure synthesis has been used for the preparation of new structural modifications of lithium transition metal oxides [23][24][25][26][27][28]. For allows stabilization of a new form of LiMPO 4 (M ¼ Fe and Ni), where the main crystal difference comes from the oxygen arrangement [23].…”

“…For allows stabilization of a new form of LiMPO 4 (M ¼ Fe and Ni), where the main crystal difference comes from the oxygen arrangement [23]. Substitution of Ga for Ni and Co in layered LiNi/CoO 2 can be realized under a high-pressure only [24][25][26].…”

“…Charge compensation is achieved by the appearance of Ni 4+ ions. The compounds prepared under high-pressure display different electrochemical properties as compared to the oxides prepared under atmospheric pressure [23][24][25][26][27][28].…”

Compositional Tuning of Structural Stability of Lithiated Cubic Titania via a Vacancy-Filling Mechanism under High Pressure

“…High-pressure methods have been widely utilized to synthesize new electrode materials not achievable under ambient conditions. Several commercially utilized battery materials have been synthesized under high pressure and were optimized for battery applications [4][5][6][7][8][9][10]. However, there are only a few studies on the mechanical properties of electrodes under high pressure [11].…”