High Temperature Secondary Lithium-ion Batteries Operating Between 25 ⁰C and 150 ⁰C

Abstract

Development of lithium-ion batteries suitable for high temperature applications requires a holistic approach to battery design because degradation of some of the battery components can produce a serious deterioration of the other components, and the products of degradation are often more reactive than the starting materials. Therefore, a careful selection and systematic characterisation of the components of lithium ion batteries is required in order to identify a number of materials and protocols for battery assembly that give promising performance at high temperatures.
This project investigates the high temperature operation of secondary lithium-ion batteries, giving an understanding of the temperature limitation of binders, electrolytes, positive electrode materials, negative electrode materials and current collectors. This thesis has successfully demonstrated the high temperature operation of lithium ion batteries up to a temperature of 150 ⁰C. Results have shown that the main factors which are responsible for capacity fade are the electrolyte, electrode binder and the current collector. It has been effectively demonstrated that lithium iron phosphate cells can be operated up to a temperature of 150 ⁰C by replacing LiPFR6R, with an alternative electrolyte LiODFB (Chapter 4). However, capacity fade was rapid at this temperature due to failure of the binder, causing first cycle irreversible capacity and long-term capacity loss (Chapter 5). It was also demonstrated in Chapter 6 that aluminium current collector corrosion was occurring during high temperature operation, as described in chapter 6.
Suggestions for further work are made in the following areas:
1. Electrolyte: the investigation of electrolytes suitable for high temperature operation could be expanded to electrolyte additives in order to allow effective stabilisation of the SEI at higher temperatures. It should also include alternative electrolyte systems such as polymers and solid-state electrolytes since it is likely that the limit of what can be achieved in liquid carbonate systems has been reached.
2. Binder: Further work should look at optimising the electrode binders, further evaluating the use of PAI as a binder for use at high temperatures, evaluating in a full Li-ion cell configuration.
3. Current Collector: alternative current collectors should be investigated for use at high temperatures that don’t corrode when operated at 150 ⁰C. The protection of the current collector could also be investigated using either coatings for the aluminium current collector or by electrolyte additives that allow effective passivation of the surface which do not fail at high temperatures.

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Identifiers

ORCID for Nuria Garcia-Araez: orcid.org/0000-0001-9095-2379

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