Probing the 3‐step Lithium Storage Mechanism in CH₃NH₃PbBr₃ Perovskite Electrode by Operando‐XRD Analysis

Abstract

Organic‐inorganic hybrid materials have gradually become one of the most actively studied research fields due to their fascinating properties. The reaction between lithium and organic‐inorganic halide perovskite has just recently been proposed. However, the exact mechanisms taking place in this electrode material have not been fully elucidated, yet. To shed light on these processes an operando‐X‐ray diffraction study has been performed and is reported herein. According to our results the lithiation of CH3NH3PbBr3 entails three reaction steps, distinguishable during the initial galvanostatic lithiation for different Li‐ion molar content x: (1) the initial Li+ insertion into the perovskite phase in which pure perovskite and lithiated phases coexist (0 <x<1), (2) the perovskite conversion reaction leading to the formation of metallic lead (1 <x<2), and finally, (3) the alloying of lithium with the metallic lead previously formed. In more detail, for x>0.3, the formation of a Lix:CH3NH3PbBr3 phase with distinctive X‐ray diffraction peaks is clearly detected, which coexists with the pristine material, till abruptly both phases disappear at x∼1 and CH3NH3Br and Pb metal are formed. It is shown that this conversion reaction is an irreversible process. The proposed mechanism for lithium storage gives a complete perspective of the complex structural environment involving the use of perovskite materials as electrodes for Li‐ion batteries.

Halide Perovskite Materials for Energy Storage Applications

“…Eventually, the Li-Pb alloy forms, which cannot be converted back to the initial states. [179] Figure 6. Lithium incorporation in halide perovskites is accompanied by both conversion and intercalation processes (left), with the conversion process suggested to dominate during lithium uptake.…”

Progress, highlights and perspectives on NiO in perovskite photovoltaics

“…Molecular or polymeric selective layers hardly prevent this interdiffusion. [28][29][30][31][32] In addition to that, dopants such as LiTFSI and tert-butyl pyridine can diffuse and react with the perovskite and layers, [33][34][35] further degrading the device performances. A uniform NiO layer ideally insulates the perovskite lm from the electrode, thus preserving the structural integrity of the device.…”

Two-Dimensional Hybrid Halide Perovskite as Electrode Materials for All-Solid-State Lithium Secondary Batteries Based on Sulfide Solid Electrolytes

“…It has been reported that batteries using CH3NH3PbBr3, which is 3D-HHP, show the discharge plateau at ~2.3 V vs. Li, corresponding to ~1.7 V vs. Li-In alloy, through the formation of the Li + -inserted CH3NH3PbBr3. 25 In case of the all-solid-state battery prepared with 2D-HHP, a similar discharge plateau was observed at ~1.5 V vs. Li-In alloy. In contrast, this discharge plateau was not observed in a lithium-ion battery using PbO, where only conversion and alloying−dealloying process has been reported.…”

“…16−18 Their potential as electrode materials has been recently explored, 19−24 and the lithium storage mechanism by insertion/extraction, conversion, and alloying−dealloying has been proposed. 25 Their characteristic structure allows an efficient ionic diffusion (Li + , Na + ). Actually, the coefficient of Li + diffusion is as high as ~10 −7 cm 2 s −1 , implying that Li + conductivity of lithiated HHP can reach ~10 −3 S cm −1 .…”