Ionic Intercalation in Two-Dimensional van der Waals Materials: In Situ Characterization and Electrochemical Control of the Anisotropic Thermal Conductivity of Black Phosphorus

Abstract

Two-dimensional van der Waals materials have shown novel fundamental properties and promise for wide applications. Here, we report for the first time an experimental demonstration of the in situ characterization and highly reversible control of the anisotropic thermal conductivity of black phosphorus. We develop a novel platform based on lithium ion batteries that integrates ultrafast optical spectroscopy and electrochemical control to investigate the interactions between lithium ions and the lattices of the black phosphorus electrode. We discover a strong dependence of the thermal conductivity on battery charge states (lithium concentrations) during the discharge/charge process. The thermal conductivity of black phosphorus is reversibly tunable over a wide range of 2.45-3.86, 62.67-85.80, and 21.66-27.58 W·m·K in the cross-plan, zigzag, and armchair directions, respectively. The modulation in thermal conductivity is attributed to phonon scattering introduced by the ionic intercalation in between the interspacing layers and shows anisotropic phonon scattering mechanism based on semiclassical model. At the fully discharged state (x ∼ 3 in LiP), a dramatic reduction of thermal conductivity by up to 6 times from that of the pristine crystal has been observed. This study provides a unique approach to explore the fundamental energy transport involving lattices and ions in the layered structures and may open up new opportunities in controlling energy transport based on novel operation mechanisms and the rational design of nanostructures.

Applications of Phosphorene and Black Phosphorus in Energy Conversion and Storage Devices

“…Fundamentals of phosphorene: a) crystal structure, b) electronic band structure, c) AFM image, HR‐TEM of d) side view and g) top view, e) EELS, f) side view and top view of atomic structure, h) SAED, i) optical micrograph, and j) Raman spectra. (a) Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…Copyright 2014, American Chemical Society. (e) Reproduced with permission . Copyright 2017, American Chemical Society.…”

Exploring the Formation of Black Phosphorus Intercalation Compounds with Alkali Metals

“…Several works appeared proposing the availability of creating different BPICs, and anticipated superconductivity in lithium intercalated samples25, 26, 27 and an excellent performance in Li‐ and Na‐ion batteries 21, 22, 28, 29. Very recently, experimental evidences of the intercalation were obtained by in situ TEM 28, 30, 31. Moreover, Grigorieva and co‐workers reported the intercalation of BP with several alkali metals (Li, K, Rb, and Cs) and alkali‐earth Ca, all of which exhibited a universal superconductivity with a critical temperature of ca.…”

“…[21,22,28,29] Very recently,e xperimental evidences of the intercalation were obtained by in situ TEM. [28,30,31] Moreover,Grigorieva and coworkers reported the intercalation of BP with several alkali metals (Li, K, Rb,a nd Cs) and alkali-earth Ca, all of which exhibited auniversal superconductivity with ac ritical temperature of ca. 3.8 K. [32] However,t he intercalation phases were mainly superficial (ca.…”

The Heat Conduction Renaissance

“…Research in this area has seen a surge over the past ten years, concurrent with improvements in nano-thermal metrology techniques including in situ characterization capabilities. Broadly classified, these approaches have utilized temperature-induced phase-change [72], [73], electric-field induced modulations of domain-walls in ferroelectrics [74], magnetic-field induced re-orientation in liquid crystals, and electrochemical intercalation-induced modifications of material microstructure [75]- [77], to achieve reversible tuning of thermal conductivity. Typical "on/off" thermal conductance ratios are <2x, while switching speeds may vary depending on the method used (<100 ms for ferroelectric domain modulation, to hours for ion intercalation in a bulk crystal).…”