Mg-Ion Battery Electrode: An Organic Solid's Herringbone Structure Squeezed upon Mg-Ion Insertion

Area of Science:

• Materials Science
• Electrochemistry
• Organic Electronics

Background:

• Organic solids offer potential for energy storage applications.
• Divalent metal ions present challenges for intercalation into electrode materials.

Purpose of the Study:

• To investigate the storage of divalent metal ions (Mg²⁺, Ca²⁺) in crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA).
• To understand the structural and electrochemical behavior of PTCDA during ion hosting.

Main Methods:

• Experimental techniques: ex situ X-ray diffraction (XRD) and transmission electron microscopy (TEM).
• Theoretical investigations: first-principles calculations.
• Electrochemical testing: cyclic voltammetry, galvanostatic charge-discharge cycling.

Main Results:

• PTCDA effectively hosts Mg²⁺ and Ca²⁺ in aqueous electrolytes.
• Mg²⁺ intercalation induces unique anisotropic squeezing deformation in the PTCDA structure.
• PTCDA Mg-ion electrode exhibits a reversible capacity of 125 mA h g^-1, good rate capability, and stable cycling.
• Ca²⁺ storage in PTCDA yields a reversible capacity exceeding 80 mA h g^-1.

Conclusions:

• The van der Waals structure of PTCDA is well-suited for hosting charge-dense divalent ions.
• Understanding the ion-induced structural changes is crucial for designing high-performance organic electrodes.
• PTCDA demonstrates promise as a cathode material for aqueous divalent ion batteries.