Thermal Behavior of Delithiated Li_1−xMnPO₄ (0 ≤ x <1) Structure for Lithium‐Ion Batteries

Abstract

High-voltage and high-capacity cathode-active materials are required to increase the energy density of rechargeable lithium-ion batteries for hybrid vehicles. The olivine-type LiMnPO 4 is considered as a good candidate for the next-generation lithium-ion battery due to its high voltage (4.1 V vs Li + /Li), low cost, and lower toxicity compared with the currently used layered materials. However, recent research has demonstrated that the thermal stability of delithiated phase of Li 1Àx MnPO 4 (0 ≤ x <1) was less than that of Li 1Àx FePO 4 . These reports verified that the delithiated MnPO 4 decomposed and changed into Mn 2 P 2 O 7 with O 2 release at high temperature. In this study, we focused on the particle and crystal changes in LiMnP O 4 /MnPO 4 at high temperature on a nanoscale. As a result, we have succeeded to observe directly the particle and crystal changes using transmission electron microscope (TEM) with heating. It revealed that MnPO 4 was a thermally unstable phase because dendrites of Mn 2 P 2 O 7 began to generate around 200°C.

Comparative Study of the Thermal Stability of Electrode Materials for Li-Ion and Na-Ion Batteries

“…The temperature of the decomposition is in good agreement with literature data; the enthalpy is within the range of the published values. , Another Li-ion cathode, LFP, demonstrated a much weaker exothermic signal at ∼370 °C (the onset is at 342 °C) with an energy release of only 50 J g –1 (Figure a). These data are also consistent with the literature; the relatively high thermal stability is explained by the rigid FePO 4 framework due to the presence of covalent bonds between phosphorus and oxygen in its structure. , However, the olivine-type phase is not preserved after heating to 450 °C and is transformed into a mixture of iron pyrophosphates (Figure and Table ).…”

“…These features, which are extremely useful from the point of view of the operability of portable devices, raise the question of the safety of using such an energy density. A lot of effort of researchers and engineers is directed toward increasing the thermal stability of LIB’s electrode materials, electrolytes, assembly issues, etc. , During the last decades, numerous studies have been devoted to the thermal behavior of different types of oxide, phosphate, pyrophosphate, and other cathode materials as well as carbon-based anode materials. − …”

“…These data are also consistent with the literature; the relatively high thermal stability is explained by the rigid FePO 4 framework due to the presence of covalent bonds between phosphorus and oxygen in its structure. 5,27 However, the olivine-type phase is not preserved after heating to 450 °C and is transformed into a mixture of iron pyrophosphates (Figure 3 and Table 1).…”

Oxygen evolution from olivine Mn1−xMxPO4 Snydacker1, Wolverton2 2017Phys. Rev. B6020View full textAdd to dashboardCite

“…46 The free energy of oxygen gas was fit to reproduce the experimentally observed 200°C (473 K) initial temperature for oxygen evolution from MnPO 4 . [9][10][11] In these experiments, no partial pressure for oxygen gas is reported. We assumed an oxygen partial pressure of 1.0 bar.…”

Ultra-Microtome for the Preparation of TEM Specimens from Battery Cathodes

“…Particulate materials ranging from nanometers to hundreds of micrometers are widely used in many fields of the industry such as energy storage (Yoshida et al, 2013; Siu et al, 2018; Zhang et al, 2018), catalysis (He et al, 2017; Stamenkovic et al, 2017), and structural composites (Flom & Arsenault, 1989; Kumlutaş et al, 2003; Yang et al, 2003). Accordingly, there is an increasing requirement to characterize their microstructures and properties with TEM techniques.…”