Thin film batteries for integrated high energy density storage

Published : 12 March 2020

The sustained miniaturization of electronics has emphasized the need for highly integrated electrochemical

energy storage. Energy storage at the point of load can reduce energy dissipated from power loss and I/O

switching noise that can plague sensitive devices while enabling unique form factors. Thin film batteries

provide some of the highest energy densities of electrochemical energy storage devices, but the perfectible

cycle life has thus far hindered their integration in devices requiring high rechargeability levels.

In this work, we aim to develop and use novel materials and device architectures to improve the

overall cycling performance. The current thin film batteries developed at the LSME present an ultra-thick

sputtered LiCoO2 positive electrode allowing for high energy density, and simultaneously representing an

ambitious scientific and technological challenge. A first objective is the investigation of correlations between

the positive electrode electrochemical performance and its physico-chemical properties, including

ion/electron conductivities, microstructure, morphology and defects. Concomitantly, the current prevailing Lifree

configuration (where Li anode is formed in-situ during charging) will be thoroughly reassessed in order

to optimize the corresponding Li ions exchange. A second objective is the screening of different metallic

and/or semiconducting anode materials and selecting the configuration allowing for the best cycle life. A

comprehensive study will be carried out during this PhD work using electrochemical techniques and physical

characterization in order to identify the reaction mechanisms involved in the different capacity decay stages.

Furthermore, the successful candidate will build a reliability model based on the experimental data, and

define functional tests to implement during the electrical characterization phases. A third object is the

development of test protocols allowing for efficient and reliable electrical wafer sorting (EWS).

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