Atomic-Scale Cryo-TEM Studies of the Thermal Runaway Mechanism of Li_1.3Al_0.3Ti_1.7P₃O₁₂ Solid Electrolyte

Abstract

Understanding the thermal runaway mechanism of solid-state electrolytes is critical for the development of all-solid-state Li-metal batteries (ASLMBs). Herein we employ multiscale methods including in situ optical microscopy and cryo-transmission electron microscopy combining with density functional theory to reveal the failure mechanism of Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 (LATP). Li reacts with LATP to form an amorphous phase at elevated temperatures, which then crystallizes into Li 3 PO 4 and LiP with additional Li 3 P and Li 0.5 TiO 2 at even higher temperatures. The instability of the corner-sharing PO 4 tetrahedra and TiO 6 octahedra against Li at high temperature is the root cause of thermal runaway for LATP. Li diffusion into LATP causes the collapse of the PO 4 tetrahedra and TiO 6 octahedra, forming Li−O, Li−P−O, and Li−Ti−O species which release a large amount of heat, triggering thermal runaway of LATP. This work provides atomic-scale understanding of the thermal runaway of LATP, which offers an important clue to mitigate failure of ASLMBs.

Role of Interfacial Defects on Electro–Chemo–Mechanical Failure of Solid‐State Electrolyte

“…iii) Partial parameters used in our model are from other literatures since they are missing in the work of X‐ray computed tomography on LAGP pellet, [ 11 ] potentially introducing deviation into the calculation process. iv) The interface conditions in real cell, including the high reactivity between LAGP and Li, varied properties of LAGP after lithiation, [ 50,51 ] are more complicated and their impact on the electro–chemo–mechanical failure process of LAGP pellet is not negligible. Therefore, the correctness of model will be significantly improved if close coordination between modeling and experimental works is built in future.…”

The electrochemical failure mechanism investigation of Li1+xAlxTi2−x(PO4)3 solid-state electrolytes

“…No other peaks corresponding to the reported degradation product were found, such as Li 3 P, Li 5 AlO 4 , Li 4 TiO 4 , and so forth. 18,19 The decomposed product was further investigated by TOF-SIMS, as shown in Fig. 5 and S6.…”

“…No other peaks corresponding to the reported degradation product were found, such as Li 3 P, Li 5 AlO 4 , Li 4 TiO 4 , and so forth. 18,19…”

“…The thermal degradation investigations clarified that the degradation of LATP contained multiple steps. 19 In other words, different degradation processes of NASICON-type electrolytes can be observed under different situations. Therefore, understanding the failure mechanisms in operating solid-state lithium batteries is imperative and significant for the application of LATP.…”

“…The distribution of Al + , Ti + , and P − signals showed no difference. The signal of the other element would be changed if Li 2 O was the degradation product 14,19. Therefore, we believed that some Li metal would attach to the surface of the degradation region when disassembling the batteries, and the attached Li metal oxidized during testing.…”