A MEMS-enabled 3D zinc–air microbattery with improved discharge characteristics based on a multilayer metallic substructure

Abstract

This paper reports the design, fabrication and testing of a three-dimensional zinc-air microbattery with improved areal energy density and areal capacity, particularly at high discharge rates. The device is based on a multilayer, micron-scale, low-resistance metallic skeleton with an improved surface area. This skeleton consists of alternating Cu and Ni layers supporting Zn as electrodeposited anode electrode, and provides a high surface area, low-resistance path for electron transfer. A proof-of-concept zinc-air microbattery based on this technology was developed, characterized and compared with its two-dimensional thin-film counterparts fabricated on the same footprint area with equal amount of the Zn anode electrode. Using this approach, we were able to improve a single-layer initial structure with a surface area of 1.3 mm 2 to a scaffold structure with ten layers having a surface area of 15 mm 2. Discharging through load resistances ranging from 100 to 3000 , the areal energy density and areal capacity of the microbattery were measured as 2.5-3 mWh cm −2 and ∼2.5 mAh cm −2 , respectively.

A MEMS lamination technology based on sequential multilayer electrodeposition

“…Permalloy is a well-known soft magnetic metallic alloy exhibiting relatively high permeability (µ r ∼ 1000) and high saturation flux density (∼1.2 T) [10]. Copper is chosen as the sacrificial material, since (1) it is selectively etched away in an ammoniacal solution [8,9] without damaging various nickel alloys including permalloy; and (2) it is able to be electroplated on the permalloy without any unwanted displacement reactions. Both dual-bath electroplating and single-bath electroplating have been reported for the fabrication of permalloy/copper multilayer composites [11,12].…”

“…Dual-bath plating is accomplished using an automated sequential electroplating system [8,9,13]. The system is comprised of two plating baths dedicated to permalloy and copper electrodeposition, respectively; two rinse baths filled with deionized (DI) water; and a robot arm capable of transferring a sample wafer from bath to bath.…”

“…The sequential electrodeposition of multilayer structures is performed on a sputtered titanium/copper/titanium seed layer, through a mold defined by photolithography [9]. A Watts type bath [15] is selected for the permalloy deposition.…”

“…After anchoring, a selective removal of sacrificial copper layers from the permalloy/copper multilayer structures is performed. The multilayer structures are immersed into a selective copper etchant [8,9]. The copper is etched beginning from the sidewalls of the multilayers which do not possess the polymeric anchors, as well as from the periphery of the multilayer structures.…”

Biofluid Activated Microbattery for Disposable Microsystems

“…A variety of microbattery architectures have been proposed ranging from complex 3-dimensional structures to ink jet printed batteries [14]- [19], but many obstacles are still impeding their implementation into microsystems. The proposed microbatteries employ intricate microfabrication schemes that involve the injection and encapsulation of the electrolyte, which hinders the possibility of mass producing them at a low cost [11], [20], [21]. In addition to the small energy content, batteries using corrosive electrolyte suffer from a high self-discharge rate that translates into a short battery shelf life.…”