TITLE:
Improved Safety for Automotive Lithium Batteries: An Innovative Approach to include an Emergency Cooling Element
AUTHORS:
Peter Kritzer, Harry Döring, Brita Emermacher
KEYWORDS:
Lithium Batteries, Safety, Electric Vehicle (EV), Hybrid Electric Vehicle (HEV), Cooling System, Air Conditioning System, Safety, Thermal Runaway
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.4 No.2,
April
15,
2014
ABSTRACT: This paper describes a concept for an independent and redundant safety
concept for Lithium batteries in Electric and Hybrid Electric Vehicles. This
concept includes an emergency cooling system based on pressurized carbon
dioxide (CO2). Since carbon dioxide (CO2) is a possible
medium of future mobile air conditioning (MAC) systems, the MAC system can be
utilized for the one-time emergency cooling described in this paper. In the
first part of the paper, some major safety aspects of automotive Li batteries
are highlighted. In the second section, the paper describes a technical
approach, how these batteries can be made safer. Pressurized CO2,
which is a promising candidate for cooling liquids used in future mobile air
conditioning (MAC) systems, is used to effectively cool down an overheating or
up-heating battery in a critical state. The safety system thereby is not based
on an electrical effect, but on a direct and fast-reacting thermal conduction,
avoiding a thermal runaway of individual cells. The application of the proposed
system is to act preventively just before the thermal runaway gets
uncontrollable. In this case, the limited amount of CO2, which is
available in the MAC system, fulfils the emergency cooling requirements. The
combination of standard car components for the concept leads to an only moderate
increase of the total weight and the additional system costs. Therefore, the
described system might be of interest for car, battery and air conditioning
system producers. This paper explains that the synergetic combination of CO2-based
MAC systems and Li-based batteries is an innovative approach to improve
environmental compatibility in future vehicles. The concept is proven
experimentally on a lab scale with battery cells and battery packs consisting
of four serially connected cells, respectively.