Nanoscale Polymer Electrolytes:  Ultrathin Electrodeposited Poly(Phenylene Oxide) with Solid-State Ionic Conductivity

Abstract

Incorporating ions within electrodeposited polymer dielectric films creates ultrathin solid electrolytes on a length scale (<50 nm) that bridges molecular electronics and conventional electrochemical devices. Electrooxidation of phenol in basic acetonitrile generates electrodeposited nanoscale (21 ± 2 nm), pinhole-free poly(phenylene oxide), PPO, films on indium−tin-oxide substrates. Solid-state electrical measurements using top electrode contacts (vapor-deposited Au, liquid Hg, or liquid Ga−In eutectic) confirm that these PPO films are electronically insulating (7 ± 2 × 10-12 S cm-1) with a high dielectric strength (1.7 ± 0.1 × 106 V cm-1). The insulating film is converted to an ultrathin solid polymer electrolyte by soaking in a solution of LiClO4−propylene carbonate and then heating under vacuum to remove solvent. Atomic force microscopy establishes that the salt-impregnated film is thicker (43 ± 10 nm) than the as-prepared PPO film. The X-ray photoelectron spectroscopic measurements suggest minimal retention of solvent in the film. Electrochemical impedance measurements demonstrate that the incorporated ions are mobile in the solid state with an ionic conductivity of 7 ± 4 × 10-10 S cm-1. Such ultrathin solid polymer electrolytes should enable progress toward nanoscopic solid-state ionic devices and power sources.

High Energy Density All‐Solid‐State Batteries: A Challenging Concept Towards 3D Integration

“…3579 mAh g À1 and 8303 mAh cm À3 , respectively, assuming complete conversion into Li 15 Si 4 . [25][26][27] However, when lithium is electrochemically intercalated in silicon, the volume expansion of the host material can be as high as 300%.…”

“…During reduction (negative currents), the red curve reveals two broad peaks ((a) and (b)) that correspond to transitions of elemental silicon into amorphous lithium silicides. Close to 0 V an additional peak (c) appears that can be ascribed to the crystallization of the material into the Li 15 Si 4 cubic phase. [25] When extracting lithium during oxidation essentially one sharp peak is visible (f).…”

“…[11] Ultra-thin nm-sized polymer separators acting as electrolyte were electro-deposited onto a highly structured, ambi-gel cathode material, such as manganese oxide. [15,16] The structure was then soaked into a liquid electrolyte in order to incorporate the required Li-salt into the polymer, providing ionic conductivity. To complete the battery, the structure has to be filled with an interpenetrating anode, a step that was proposed to consist of cryogenic deposition of the active anode material.…”

“…This interesting work is in progress and its viability has not been proven yet. [15,16] An alternative approach has recently been proposed by the present authors. [17,18] The concept of 3D-integrated allsolid-state batteries is based on mature etching methods to enlarge the surface area and step-conformal deposition technologies, such as Low Pressure Chemical Vapor Deposition (LPCVD) and Atomic Layer Deposition (ALD).…”

Self-organized templates provide backbone for all integrated Li-ion batteries

“…5 From a fundamental scientific viewpoint, it is worth noting that the work reaches extremely interesting electrochemical dimensions where classic intercalation (battery) and classic surface charging (supercapacitors) begin to unify.…”