We are at the dawn of a new era for passenger transportation, where Internal Combustion Engine (ICE) powered cars are bound to be replaced by Full or Hybrid Electric Vehicles (FEV/HEVs), herein referred to as Electric Vehicles (EVs). Latest awakening by different governments worldwide regarding global warming has encouraged the development and adoption of novel solutions to reduce CO2 emissions. In particular, the British government has set the end of the sale of conventional ICE cars and vans by 2040, as part of the UK Air Quality Plan [1]. However, although progress has been made in recent years, EVs still represent less than 1% of the global fleet for passenger cars [2]. The most prominent barriers preventing the customers to purchase an EV are, in order of importance: limited all-electric range (confirmed by the range anxiety phenomenon); elevated cost; limited number of charging infrastructure; prohibitive charging time [3]. At the moment, research on novel battery technology is still at early stages, hence the performance of Li-ion batteries needs to be improved. A critical factor influencing the performance, operation and safety of this type of battery is temperature. Due to limitation in the Li-ion intercalation process at low temperatures, and the dissolving of the Solid Electrolyte Interphase at high temperature, a critical decrease in capacity, number of cycles and power output have been observed. In fact, at -20°C the available energy is 60% of the room-temperature value [4], whereas capacity losses of 36% were reported at 45 °C [5]. Moreover, a potentially destructive situation may arise when the heat internally generated by the battery is greater than the heat removed by the cooling system, known as thermal runaway. The thermal runaway can be the response to different fault scenarios, such as mechanical abuse (tearing of the separator), electrical abuse (overcharging) or thermal abuse (insufficient cooling), leading to a self-sustained reaction that can escalate into smoke, fire and eventually into an explosion. As a consequence, there is a need to thoroughly asses EV thermal management and to push it towards a solution that is: efficient, light as well as one that consumes the least parasitic power possible (increasing the range of the vehicle); cheap, durable and simple (reducing the cost of the vehicle); able to work at high charging rates (allowing for shorter charging time). The thermal management of the battery needs to work on two levels, namely at cell level and module/pack level. The cell temperature must to be maintained between 25°C-40°C for best operative life and performance; and at module/pack level the temperature difference between cells must be maintained below 5°C, as otherwise it creates an imbalance, deteriorating the performance of the whole pack.
[1]
Benjamin K. Sovacool,et al.
Fear and loathing of electric vehicles: The reactionary rhetoric of range anxiety
,
2019,
Energy Research & Social Science.
[2]
Leonard L. Vasiliev,et al.
Heat pipes in modern heat exchangers
,
2005
.
[3]
Li Jia,et al.
Experimental investigation on lithium-ion battery thermal management based on flow boiling in mini-channel
,
2017
.
[4]
J. Whitacre,et al.
Lithium Ion Batteries for Space Applications
,
2007,
2007 IEEE Aerospace Conference.
[5]
Ralph E. White,et al.
Capacity fade of Sony 18650 cells cycled at elevated temperatures. Part II. Capacity fade analysis
,
2002
.
[6]
Pascal Henry Biwole,et al.
Electric vehicles batteries thermal management systems employing phase change materials
,
2018
.
[7]
Ajay Kapoor,et al.
A novel thermal management system for improving discharge/charge performance of Li-ion battery packs under abuse
,
2018
.
[8]
Lei Cao,et al.
A review on battery thermal management in electric vehicle application
,
2017
.