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PhD defence by Ana-Irina Stroe on Analysis of Performance and Degradation for Lithium Titanate Oxide Batteries

Time

16.04.2018 kl. 13.00 - 16.04.2018 kl. 16.00

Description

Ana-Irina Stroe, Department of Energy Technology, will defend the thesis "Analysis of Performance and Degradation for Lithium Titanate Oxide Batteries"

TITLE

Analysis of Performance and Degradation for Lithium Titanate Oxide Batteries

PHD DEFENDANT

Ana-Irina Stroe

SUPERVISOR

Professor Remus Teodorescu

MODERATOR

Associate Professor Tamas Kerekes

OPPONENTS

Associate Professor Erik Schaltz, Dept. of Energy Technology, Aalborg University (Chairman)
Igor Villarreal Sarria, IKERLAN, Centro de Investigaciones Tecnológicas, Mondragon, Spain
Professor Torbjörn Valdemar Thiringer, Chalmers Tekniska Högskola, Gothenburg, Sweden

ABSTRACT

Energy storage (ES) has become a key enabling technology for a wide range of applications, which includes among others electrical vehicles (EVs) and smart grids. Various ES technologies are available and they greatly differ in their operation principle, maturity level, performance behavior, and lifetime characteristics. However, Lithium-ion (Li-ion) batteries have detached as one of the very few ES technologies, which meet the requirements of different applications such as consumer electronics, EVs, grid support, and enhancing renewable’s grid integration. The Li-ion batteries have continuously developed in the past years either by improving the already existing chemistries or by looking into new chemistries; this is also the case of the Lithium Titanate Oxide (further referred as LTO) based batteries, which use LTO as anode active material instead of the traditional graphite. LTO-based batteries are characterized by high power capability during both charging and discharging (e.g., up to 10 C-rate), high thermal stability, increased safety, and long lifetime (e.g., up to 15.000 full cycles) at the expense of a low energy density, which is mainly caused by the low operating voltage (i.e., 2.3V). As LTO is a quite new Li-ion battery chemistry, its behavior and characteristics are still not totally understood yet. Therefore, the purpose of this dissertation has been to push forward the state-of-art knowledge regarding LTO-based Li-ion batteries.

An extensive experimental laboratory characterization testing procedure was developed and applied to several 13 Ah LTO-based Li-ion batteries. Thus, the batteries’ capacity, open circuit voltage, internal resistance, power capability, and small signal AC impedance were measured over a wide temperature range (i.e., 5_C to 45_C) and for various load currents (i.e., from C/10-rate to 9C). Based on these performance results, models able to predict the dynamic behavior of the LTO-based battery cells were developed and experimentally validated. These electrical battery models were built using results from both electrochemical impedance technique and DC pulse technique performed under various operating conditions.

The electrical model based on DC pulse technique is able to simulate the dynamic voltage response of the studied LTO-based Li-ion battery cell and was further used to develop a state-of-charge (SOC) estimation algorithm based on Kalman filters. Nonlinear filters, extended Kalman filter and unscented Kalman filter were used for estimating the SOC of LTO-based Li-ion battery cell upon the voltage response of the battery cell and the model.

The last part of the dissertation was dedicated to the analysis of the degradation behavior of the studied LTO-based battery cells. For this purpose, accelerated calendar and cycle lifetime tests were performed over a period of three years. The obtained results for the cycle lifetime tests, show an initial very slow degradation rate, which is interrupted by a sudden decrease in the battery performance (both capacity and internal resistance). In the case of the calendar lifetime tests, no degradation of the battery capacity was observed even after 2.5 years of aging at temperatures higher than 35_C. The influence of different stress factors such as temperature, SOC, and load current on the degradation of the performance parameters was studied and assessed individually.

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PhD defence by Ana-Irina Stroe on Analysis of Performance and Degradation for Lithium Titanate Oxide Batteries

ALL ARE WELCOME. THE DEFENCE WILL BE IN ENGLISH.

AFTER THE DEFENCE THERE WILL BE AN INFORMAL RECEPTION AT PONTOPPIDANSTRAEDE 111 IN ThE COFFEE ROOM.

 

 

Host

Department of Energy Technology

Address

Pontoppidanstræde 111, auditorium 1.177

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