Photopatterning and Electrochemical Energy Storage Properties of an On-Chip Organic Radical Microbattery

Abstract

One potential way to fabricate battery-on-chip is photopatterning electrochemical energy storage materials directly on electronics through lithography, but applicable materials are primarily limited to transparent photocurable resins. The transparency of the photoresist would be sacrificed after extra addition of insoluble inorganic battery materials and conductors. Given the importance of radical polymers for their appropriate solubility, optical transparency, and radical robustness, they may have potential application in on-chip energy storage, transport, and conversion devices. Herein, an anodic photoresist is proposed by modifying the MicroChem SU8 resist with a radical polymer poly(2,2,6,6-tetramethyl-4-piperidinyl-N-oxyl methacrylate) and an ionic conductor lithium perchlorate. It can be photopatterned on silicon wafer with 10 μm scale resolution, and it exhibits charge/discharge potentials at ca. 0.68 V versus silver chloride electrode; the coulomb efficiency is regarded as nearly equaling 100%. Although the specific capacity of the photopatterned film electrode is found to be modest, 1 × 10 −5 mA h•cm −2 , it presents 1/8 of its theoretical electron storage ability. All-solid-state half-cells with circular features 30 μm in diameter are prepared by means of overlay exposure using the as-prepared photoresist and lithium perchlorate-modified SU8 as the anodic electrode and solid electrolyte, respectively. These results suggest a promising way of using radical polymers for the integration of electrochemical energy in microelectronics.

Recent Advances in High‐Performance Microbatteries: Construction, Application, and Perspective

“…As the core material, photoresist could not only serve as the etching medium for patterning, but also be transformed into battery components. [ 32,42,43 ]…”

“…Considering its appropriate solubility, the potential value about the function of the electrode or solid electrolyte has not been fully explored. Recently, Cao and co‐workers [ 32 ] reported a promising way of utilizing photoresist as a solid electrolyte for the on‐chip battery. By modifying SU‐8 photoresist with a portion of radical polymer and ionic conductor LiClO 4 , the prepared Li + ‐ e SU8 served for both reversible redox performance and ionic transport, thus meeting the basic demand of electrolyte ( Figure a).…”

“…a,b) Reproduced with permission. [ 32 ] Copyright 2019, American Chemical Society. c) Schematic illustrations of Zn//MnO 2 MBs via the writing laser.…”

“…Along with the continuous progress in advanced equipment, the development of the etching technique is promoted which allows diverse options. Among the plentiful varieties, some kinds of etching techniques such as photolithography, [31][32][33] laser scribing, [23,[34][35][36] and plasma etching, [37][38][39] are of high anisotropy and controllability, to a certain extent exhibiting giant potential in micromachining. Therefore, we recommend three broad categories for their wide applications in fabricating MBs and introduce their advantages and inherent defects.…”

“…As the core material, photoresist could not only serve as the etching medium for patterning, but also be transformed into battery components. [32,42,43] In traditional photolithography for the miniaturization process, the photoresist is selectively removed. In the subsequent electrode construction, researchers usually take advantage of various membrane formation techniques for the whole surface covering, such as physical vapor deposition (PVD) and magnetron sputtering to deposit metal current collector, and electrochemical deposition, chemical vapor deposition (CVD) or atomic layer deposition (ALD) to grow active materials.…”