Crystallization behavior of the Li2S\u2013P2S5 glass electrolyte in the LiNi1/3Mn1/3Co1/3O2 positive electrode layer

Hirofumi Tsukasaki,Takahisa Ohno,Shigeo Mori,Yota Mori,Misae Otoyama,Takamasa Asano,So Yubuchi,Masahiro Tatsumisago,Akitoshi Hayashi,Yoshinori Tanaka

doi:10.1038/s41598-018-24524-7

Hirofumi Tsukasaki, Takahisa Ohno + Show 8 more

Open Access

https://doi.org/10.1038/s41598-018-24524-7

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Abstract

Sulfide-based all-solid-state lithium batteries are a next-generation power source composed of the inorganic solid electrolytes which are incombustible and have high ionic conductivity. Positive electrode composites comprising LiNi1/3Mn1/3Co1/3O2 (NMC) and 75Li2S·25P2S5 (LPS) glass electrolytes exhibit excellent charge–discharge cycle performance and are promising candidates for realizing all-solid-state batteries. The thermal stabilities of NMC–LPS composites have been investigated by transmission electron microscopy (TEM), which indicated that an exothermal reaction could be attributed to the crystallization of the LPS glass. To further understand the origin of the exothermic reaction, in this study, the precipitated crystalline phase of LPS glass in the NMC–LPS composite was examined. In situ TEM observations revealed that the β-Li3PS4 precipitated at approximately 200 °C, and then Li4P2S6 and Li2S precipitated at approximately 400 °C. Because the Li4P2S6 and Li2S crystalline phases do not precipitate in the single LPS glass, the interfacial contact between LPS and NMC has a significant influence on both the LPS crystallization behavior and the exothermal reaction in the NMC–LPS composites.

Highlights

All-solid-state lithium batteries have recently attracted much attention owing to the use of nonflammable electrolytes[1]
The present results showed that the LiNi1/3Mn1/3Co1/3O2 (NMC) and 75Li2S·25P2S5 (LPS) crystallization process differed depending on the presence of an interfacial contact with NMC
The LPS crystallization behavior differed depending on the presence of an interfacial contact between LPS and NMC

Summary

Introduction

All-solid-state lithium batteries have recently attracted much attention owing to the use of nonflammable electrolytes[1]. The crystallization of Li2S–P2S5 glasses involves an exothermic reaction, which affects the thermal stability of the all-solid-state cells when they are operated at a high temperature[12]. The glass transition of the LPS glass in the NMC–LPS composites was accompanied by the morphological shrinkage of the sample These properties implied that the interfacial contact between NMC and LPS influence the LPS crystallization behavior and the corresponding exothermal reaction[13]. To further understand the origin of the exothermic reaction present in the NMC–LPS composites, the precipitated crystalline phase in the LPS glass was examined using a computer program called “ProcessDiffraction.” In ProcessDiffraction, the electron diffraction (ED) patterns of polycrystalline and amorphous samples can be analyzed[14,15,16,17]. On the basis of the in situ TEM observations and first-principles calculation for the chemical reaction, the influence of the interfacial contact between NMC and LPS on the LPS crystallization behavior and origin of the exothermal reaction are discussed

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