Front Edge Technolgy, Inc.

This study demonstrates the construction of a multifunctional composite structure capable of energy storage in addition to load bearing. These structures were assembled and integrated within the confines of a multifunctional structural composite in order to save weight and space. Carbon fiber reinforced plastic (CFRP) composites were laminated with energy storage all-solid-state thin-film lithium cells. The processes of physically embedding all-solid-state thin-film lithium energy cells into carbon fiber reinforced plastics (CFRPs) and the approaches used are reviewed. The effects of uniaxial tensile loading on the embedded structure are investigated. The mechanical, electrical, and physical aspects of energy harvesting and storage devices incorporated into composite structures are discussed. Embedding all-solid-state thin-film lithium energy cells into CFRPs did not significantly alter the CFRP mechanical properties (yield strength and Young's modulus). The CFRP embedded energy cells performed at baseline charge/discharge levels up to a loading of about 50% of the ultimate CFRP uniaxial tensile rupture loading.

The microstructural stability of nanocrystalline LiCoO2 cathodes in rechargeable thin-film batteries after high-voltage cycling was investigated by transmission electron microscopy. It was found that besides the trigonal-LiCoO2 phase, there are two other phases of LixCoO2, spinel and H1–3, that form inside the nanocrystalline cathode after electrochemical cycling (charge cutoff voltages ≧4.5V). The formation of the aforementioned secondary phases in the cathode material is irreversible and leads to capacity loss in lithium thin-film batteries.

A method is introduced to study the effects of flexural deformation on the elec. performance of thin-film lithium-ion batteries.Flexural deformation of thin films is of interest to engineers for applications that can be effective in conformal spaces in conjunction with multi-functional composite laminates in structural members under mech. deflections such as thin airfoils used in unmanned aerial vehicles (UAVs).A test fixture was designed and built using rapid prototyping techniques.A baseline reference charge/discharge cycle was initially obtained with the device in its un-flexed state, in order to later contrast the performance of the thin-film battery when subjected to deflections.Progressively larger deflections were introduced to the device starting with its un-deformed state.The cord flexure was applied in increments of 1.3% flex ratio, up to a maximum of 7.9%.At each successive increment, a complete charge/discharge cycle was performed.Up to a flex ratio of 1.3%, no effects of mech. flexure on battery performance were observed, and the device performed reliably and predictably.Failure occurred at deflections above 1.3% flex ratio.