Keywords

1 Introduction

Lithium-ion batteries-driven electric vehicles are been incorporated mainly to reduce gaseous emissions from petrol/diesel-driven IC engine vehicles. The introduction of Chevrolet’s Bolt and Tesla’s Model 3 marked a new era for the automotive industry. Due to its most advantageous properties such as long cycle life, higher energy density, low self-discharge rate, and high-efficiency lithium-ion battery (LIB) packs are most popularly employed for such electric vehicle (EV) applications. However, as mentioned in [1–4], health and performance of the batteries are correlated strongly on working conditions as well as its temperatures. The most important component in an EV is a power train [5] especially, battery modules. A damage tolerant battery pack as a multifunctional system [6] is developed by Kukreja et al. by the combination of energetic materials and mechanically sacrificing elements to overcome the damages caused by mechanical stresses and to dissipate energy. Zhu [7] carried out various experiments on 18,650 cells by Normalized Critical Displacement (NCD) to short circuit method with and without protection using a hemispherical punch, lateral compression, cylindrical punch, and 3-point bending to verify the mechanical abusing factors leading explosions and damages. Yann leost and Matthias boljen carried out mechanical abuse testing by creating a scenario of “crash,” performing knife tests and penetration tests on Li-ion-pouched cells used for Toyota’s first-generation electric vehicle model “Yaris.” Various abuse causing factors [8] are represented pictorially in Fig. 1a.

Fig. 1
figure 1

Lithium-ion battery failure during accidents a abuses, b mechanical failure during accident/crash [6], c internal short circuiting owing to battery damages

Full size image

Design, fabrication, and performance of a Li-ion battery as a multifunctional energy storage composite structure (MECS) as the load-bearing energy storage unit have been determined in [9]. A model was proposed by Moyer et al. [10] stating the production of high-performance structural battery by direct integration of pouched Li-ion battery materials into a carbon fiber-containing composite matrix using traditional composite layup process. The proposed concept of structural batteries relates the materials’ ability to store energy and carry mechanical loads. The potential of storing energy into a carbon fiber-reinforced plastic is analogous to lithium-ion batteries (LIBs) depending on their material compositions and structural design [11].

Vibrational properties of the lithium batteries are determined numerically and experimentally [12, 13] to determine their natural frequencies. Even failure of a single battery can lead to disaster and the public’s positive view towards electric mobility may turn down affecting the manufacturer of the product and economy of the industry. An overcharged battery, too-high discharge rates, or a short circuit (internal or external) can cause thermal runaway, these events particularly depend on the chemistry of a Li-ion cell, therefore, it is the responsibility of battery management system to ensure that the cells of a battery operate within their rated specifications. Temperature uniformity for any battery pack is an essential need for long-term usage; therefore, its maintenance can lead to a healthier battery pack [14–16]. Battery cooling models by active, passive, or integration of active and passive models are proposed stating their own advantages and disadvantages in [17,18,19,20].

Consequently, in this paper, a generalized review is carried out to entertain the events affecting the structure of an electric vehicle, heating/cooling models, placement, and protection of battery packs.

2 Materials Composition

A 24 kWh battery pack with each cell having a voltage of 3.85 V 32 ah capacity consisting of 192 lithium-ion batteries is used to configure a battery pack [21]. Kukreja et al. proposed a granule-based assembly (GBA) configuration [6] with dimensions of 9.53 mm tube diameter, tube wall thickness of 1.0 mm and 18,650 cells were used, four configurations were examined in their study (a) batteries only (EV1), (b) batteries with Gba with reduced storage capacity (EV2), (c) batteries protected using external foam (EV3), (d) batteries having the same configuration as EV1 with GBA (EV4). In another study made by Bouvy et al., a 18,650 cell with geometrically varying small battery cells was selected; these cells in a certain specified configuration are combined as mechanical units to determine the factors affecting mechanical properties of the battery pack [22]. The material composition by Ladpli et al. [12] is a battery core with required geometrical specifications constructed by stacking Li-ion cells with cathode and anode layers arranged alternatively and separated by “polyolefin separator layers.”

Wei and Agelin-Chaab [18] used an Efest made IMR 26,650 5200 mAh battery cells arranged in eight rows each having a nominal voltage of 3.7 V and weighing 92 g in combination with cooling devices such as air cooling fiber strips, water coolant reservoir, and a fan for analysis of a hybrid cooling concepts for a battery pack. Different configurations of design such as inlet plenums, jet inlets, and multiple delta winglet vortex generators were used as cooling models in [23]. Whereas in [14], a simple battery pack with a total of 32 cells was developed by 18,650 commercial Li-ion cells made of Samsung model no. INR18650-25R, as mentioned, was used in the study for determining heat flow and non-uniform temperature distribution. S. Al Hallaj and J. R. Selman first proposed a passive cooling model in the year 2000 by using “phase change materials,” and different design was proposed as cooling models using PCM’s considering Hallaj’s model as a base [17, 18 and 24].

3 Experimental, Simulations, and Their Outcomes

3.1 Impact Tests

The electric vehicle concept is generalized by the removal of the internal combustion (IC) components from the vehicle model to obtain a basic vehicle frame. Four different EV configurations were investigated by J. Kukreja et al.; the secondary safe zone and the frontal section of a vehicle are utilized for placing battery packs, away from interior space adjacent to a firewall shown in Fig. 2a. Performance of battery packs located at secondary safe zone of a conceptual EV undergoing a frontal crash test has proven to be more efficient than located at primary safe zone considering a “damage tolerant battery pack,” and granular based assembly (GBA) battery pack is multifunctional and more effective in alleviating battery failure in a crash. Similarly, in [25], an efficient layout for electric vehicles with certain corrections was developed similar to an IC engine vehicle for determination of cabin deformations during a frontal crash placing a battery pack outside the passenger’s compartment is shown in (b). However, the definition of vehicle structure remains unchanged and defines battery pack placement at safe zones in the above cases. The characteristics relating deformation of a vehicle depend strongly on the parts that are stiffer. Deformation matrixes, cell frequency, and deformation zones are expressed as the interpolation of a maximum number of linear points on a vehicle.

Fig. 2
figure 2

Battery placement zones a GBA configuration, b Cabin deformation [23]

Full size image

Computer-aided design (CAD) tools are used to obtain the construction data of any model; Claude Bouvy et.al proposed a holistic and model-based design approach which resulted in an excellent design for the protection of batteries due to increasing energy absorption structures [8]. A one-dimensional energetic simulation platform is used to integrate the overall system to influence the functionality and efficiency of the model. The mechanical, electrochemical properties, and chemistry of a chosen battery for the structural composite panels are examined at various points throughout the tensile test by the use of galvanostatic measurements [10]. Carbon fibers are important for the development of a structural battery by considering it as an electrode member to obtain dimensional stability during charging and discharging and also it is capable withstanding higher mechanical loads [26]. By the use of interlocking rivets for joining the two split composite plates or beams with batteries between their layers was able to carry the transverse shear load. Hence by [6, 10], it has resulted that deformation of multifunctional energy storage composites requires higher quasi-static forces due to their increase in bending resistance.

The crash simulations [6] are performed using the Ls Dyna tool. The “New Car Assessment Program” (NCAP) was used to validate the model with the stated Frontal Impact Test number 7520 (35 mph, 56 km/h). Specific absorption energy during a crash is always an idealized principle for any mechanically designed battery pack [8]. Front pole impact, undercarriage impact, moving side pole barrier, and car-to-car crash tests [20] were performed by “Ever safe” to determine the deformations due to loading and ability to withstand abuses where all the above models proposed resulted in safety features of any battery pack due to increase in their capabilities to withstand higher loads during crash also can be investigated by computing the values of the maximum principal compressive stress (σcomp). The allowable stress level (σallow) is determined using Eq. 1 and elements failed in a battery pack is given by Eq. 2 where σallow is the Allowable stress; σf = Failure stress and Fs = Factor of safety also.

$$ \sigma_{{{\text{allow}}}} = \, \sigma_{{\text{f}}} /F_{{\text{s}}} $$
(1)
$$ \sigma_{{{\text{comp}}}} \ge \, \sigma_{{{\text{allow}}}} $$
(2)

If maximum principal stress is greater than or equal to allowable stress, the elements will failed.

4 Heat Flow, Cooling Models for Battery Pack

The heat produced while discharging a battery in electric vehicles creating a nuisance led to the development of thermal storage systems. The cooling and heating concept for the proposed geometrical designs are simulated by computational fluid dynamics (CFD) [8, 14, 15, 16]. In [10], a state of charge (SOC)-controlled range extender without the heat pump, thermally controlled range extender with heat pump are used as an experimental setup for determination of heat accumulated, depicting the European winter scenario. Seonggi Park et al. proposed an improvised cooling system with the combination of refrigerant-cooling and forced air-cooling [17] also in [16], it has been proved that temperature of the battery can be maintained by optimal arrangement of battery cells and controlled coolant flow rate. The problem relating non-uniform cooling of cylindrical cells is addressed by Shahid and Agelin-Chaab [14] for a simple battery pack configurations they proposed a passive approach model to improve uniformity in temperature, as a solution an inlet plenums (This plenum acts as a nozzle to accelerates air flow rate and changing the flow direction and eliminating the dead heat accumulation zones inside a pack) with three different configurations are added to the battery pack whereas Wei and Agelin-Chaab [15] proposed a model (hybrid) using a series of “hydrophilic fiber channels” which acts as a simple air cooling duct placed between the spaces of each cells and a water coolant placed beneath the battery and fiber channels is driven purely by capillary forces and extraction of heat (latent) by evaporation of water from the battery. A new conjugated cooling model using liquid cooling technique and phase change material as an arrangement of the cold plate at the bottom and PCM filled between the Li-ion cell gaps was detailed in [24].

5 Discussion and Challenges

Globally developing automotive companies are looking forward to develop their own passenger cars for electric mobility (Table 1); the graphical representation for different models of car is shown in Fig. 3a and its trend in future (Fig. 3b) depicts how far a car can propel when it is 100% charged. Figure 4a, b shows various parameters related.

Fig. 3
figure 3

a Electric cars range per full charge, b trend of electric vehicles in period

Full size image
Fig. 4
figure 4

Graphical representations. a Specific energy and energy density, b electric vehicle storage opportunities (GW) till 2022 and the anticipated growth

Full size image

Battery and vehicle safety of a developed multifunctional models [9–11] have been explored very little. More research work is yet to be carried out in this area. Manufacturing methods, validation, and refinement of the battery packs for cooling and electrical connection are yet to be explored for higher energy absorption during accidents/crash, penetration by sharp objects, or by any other forms of mechanical failure. Parameters’ affecting the vibrational properties of an EV have been less explored, and also cooling of Li-ion cells by passive cooling models [27] has been less explored.

Another challenge is the disposal of batteries as it is a main energy storage device that contains certain hazardous chemicals such as lead, lithium, cobalt, nickel, which lead to the environmental issues and can affect the health of an individual.

The electric vehicles initiative (EVI) is a multi-government policy forum for the introduction and adoption of electric vehicles thereby thirteen countries such as Canada, France, Japan, Norway, Chile, Germany, Netherlands, Sweden, China, India, New-Zealand, United Kingdom, and USA being the members. The development of EV’s in India is largely supported and driven by the country’s government and policies. In 2015, an initiative named “FAME” (Faster Adoption and Manufacture of Electric vehicles), a part of the National Electric Mobility Mission Plan, has been undertaken for production and promotion of eco-friendly vehicles including hybrid and electric vehicles. Global Environment Facility project on EV is elaborated by United Nations Environment Programme (UNEP) and International Energy Agency (IEA) to widen the EVI by reaching Latin America, South-East Asia, Central, and Eastern Europe.

6 Conclusions

To summarize, this paper has reviewed the development of electric vehicles powered by lithium-ion cells. The materials and components of a battery, design, and crashworthiness of the proposed models have been well studied. Designing a fully protective battery pack is solemnly a critical process, poor design leads to mechanical, electrical, and thermal abusing conditions, and this can be improved by the use of various origami structures that can resist the higher impacts. Also, various battery cooling models using the active cooling methods have been studied which is agreeable with the proposed design but has the number of working parts, the use of efficiently designed passive cooling models by paraffin wax as a medium can improve the performance of the module.

Table 1 Some electric vehicles, price, power, toque, range
Full size table