1. Introduction
The transport sector, mainly including passenger vehicles, is considered the main source of total greenhouse gas emissions internationally [
1]. Switching to electric vehicles is considered a key aspect of reducing greenhouse gases [
2]. Hence, the lithium-ion batteries (LIBs) used in electric vehicles have been key subjects of research in recent years. Although batteries for electric vehicles have many advantages, they still have a significant negative impact on the natural environment [
3]. A detailed understanding of the environmental impact of lithium-ion batteries at each phase of their life cycle is essential to achieving sustainability of not only the batteries, but also vehicles powered by them [
4]. Analysis of the main environmental loads of batteries and other accompanying products refers to the dynamics of enterprise development, for example, Industry 4.0 [
5,
6,
7,
8]. Additionally, it is necessary to improve these products to achieve the expected quality [
9,
10], while ensuring their environmentally friendly impact [
11].
The literature review shows that many studies have been conducted on the life-cycle assessment of various types of lithium-ion batteries used in the automotive industry. For example, lithium–iron phosphate batteries with different solvents used for cell production have been analyzed [
12]. Marques et al. [
3] compared the performance of lithium manganese oxide batteries with lithium iron phosphate batteries, including assessing their life cycle, considering global warming, acidification, and eutrophication. The research conducted by the authors of studies [
13,
14,
15,
16] addressed the environmental impact of lithium-ion batteries, e.g., lithium iron phosphate and lithium nickel cobalt, during their production, use, or recycling phases, showing a significant carbon footprint in these phases. Furthermore, Chen et al. [
16] investigated the potential to reduce carbon dioxide emissions in a life cycle assessment of lithium-ion batteries. Yang et al. [
17] conducted predictive analyses of the production of lithium-ion batteries until 2030, taking into account possible changes in their power, energy life, and charging efficiency. Nordelöf et al. [
18] modeled the end-of-life stage in the life cycle of lithium-ion batteries. In turn, Cerdas et al. [
19] studied various processes within the life cycle phases of lithium-ion batteries, considering the impact of aspects such as the quality of the recovered material and the consumption of energy and materials. Similarly, Yang et al. [
20] studied the environmental impact as part of battery recycling in view of economic viability and also provided an inventory of the battery life cycle. Chorida et al. [
21] analyzed the environmental burden resulting from increased use of steel in battery production in terms of the life cycle. In addition, Yoo et al. [
22] analyzed battery metal recycling with lithium recovery for used lithium-ion batteries, and greenhouse gas emissions during the battery life cycle were evaluated. Another type of analysis was carried out, for example, by Miranda et al. [
23] as part of the application of particle swarm optimization of a neural network to assess the state of charge of a battery. Then, Bhinge et al. [
24] evaluated the life cycle of a lithium-ion battery with a large amount of data in the event of product quality deterioration. In turn, Picatoste et al. [
25] assessed the environmental impact of batteries, focusing on a closed-loop system and the battery life cycle, analyzing industrial challenges and also beneficial design practices for lithium-ion batteries used in the automotive industry. It is important to mention that, according to recent results, China’s electric vehicle policy has been a notable success. As the number of electric vehicles in this country continues to grow, China is building more charging stations, improving the brand of the vehicles offered, and increasing their commercial sales [
26]. However, the increase in the use of battery vehicles also comes with potential pitfalls, and the main one is excessive battery waste. Statistics showed that more than 200,000 tons of waste from lithium-ion batteries were created in 2020, and their number is constantly growing. This waste has a particularly significant impact on the environment, which is why China and other countries have begun to pay attention to how this waste is managed. However, it remains a pressing issue [
27]. In addition, the depletion of lithium is a problem that significantly hampers efforts to reduce carbon dioxide emissions [
28].
Within the literature review, a small number of studies were observed that included comparative analyses of various lithium-ion batteries, considering the environmental burden on the ecological footprint [
26] arising during the extraction and processing of these battery materials during their lifetime. Therefore, the aim of this investigation was to perform an in-depth comparative analysis of electric vehicle batteries, which were analyzed in terms of environmental loads, including ecological footprint criteria from the extraction and processing of battery materials throughout their life cycle (LCA).
The originality of this research is based on the identification of the main environmental burdens regarding the ecological footprint (considering carbon dioxide emissions, land use, and nuclear emissions) in the first phase of LCA for popular lithium-ion, lithium iron phosphate, and lithium nickel cobalt-manganese batteries. The results of this analysis were supplemented with proposals for improvement actions to reduce the main environmental burdens, which may be useful to enterprises producing these types of batteries as part of their sustainable development.
2. Materials and Methods
This research included a comparative analysis of the environmental burdens arising from the extraction and processing of materials during the life cycle of batteries for electric passenger vehicles. Life cycle assessment (LCA) is one of the most common methodologies for assessing environmental impacts [
27], providing an assessment of inputs and outputs and interpretation of the results of the assessment of the environmental impact of a product or process throughout its life cycle [
28]. The basic life cycle approach is cradle to grave, which includes material extraction and processing, production, use, and end of life [
29]. The LCA methodology is based on the ISO 14040 standard [
30] according to which it proceeds according to four interactive stages: (i) defining the purpose and scope of the research, (ii) inventory, (iii) environmental impact assessment, and (iv) interpretation [
31]. The use of LCA can support making more pro-ecological decisions throughout the life cycle, and it can also be a source of knowledge for selected phases of the cycle, including adapting the type of analysis to the desired criteria of environmental burdens [
32,
33]. Therefore, the present research method included defining the research object, the functional unit, the system boundary, and the research scope, as detailed later in this paper.
The subjects of this research were batteries for electric passenger vehicles, which were selected in terms of their popularity due to the cathode material [
34]: lithium ion (Li-Ion) [
35,
36], lithium iron phosphate (LiFePO
4) [
37], and ternary lithium nickel cobalt manganese (NCM) [
38]. It is important to analyze the burdens associated with them, especially since their use is expected to increase in the coming years, even to a level of 65,000 tons on the global market by 2025 for, e.g., LiFePO
4 batteries [
39].
A feature that characterizes vehicle batteries is their chemical composition, which generates battery performance but also contributes to the demand and method of selecting materials [
40,
41]. Lithium-ion batteries occupy a significant share of battery technologies, mainly due to their high efficiency provided through the right combination of high energy and power density [
42]. The lithium used in them has the highest cell potential, which is due to having the lowest reduction potential among other elements [
43]. Additionally, lithium is one of the lighter elements and has one of the smallest ionic radii considering all individually charged ions. It has a high gravimetric capacity but also a high volumetric capacity and a high power density [
44]. The main limitation of these batteries is their relatively long charging time, caused by the diffusion in solid electrodes [
45]. A lithium-ion battery contains compounds of lithium manganese oxide and lithium cobalt oxide. These batteries come in different varieties, such as the next lithium iron phosphate battery selected for analysis (LiFePO
4, LFP), which contained much lighter iron compounds and was produced from lithium iron phosphate cathode materials [
37]. Compared with traditional lithium-ion batteries, they have higher charging and discharging efficiency, including a longer cyclic life and a more stable thermal and chemical structure [
46]. They have a high level of safety, good thermal and cyclic stability, and relatively low material cost [
39]. In turn, lithium nickel cobalt manganese (NCM) batteries are gaining popularity due to their large capacity, energy density, and good stability. They are lighter than previous batteries and efficient, considering the range of travel [
34]. The nickel content in NCM batteries contributes to a significant reduction in problems related to their sustainability and costs due to the lower cobalt content [
47].
The main elements of the selected batteries for passenger electric vehicles are the battery modules, which consist of battery cells. In turn, these cells contain, among other elements, an anode, cathode, separator, and electrode [
48]. Taking these elements as the main ones, material data concerning the analyzed batteries were developed. Data were prepared based on a literature review, e.g., [
35,
49,
50], the GREET v1.3.0.13991 model [
51], and data from the Ecoinvent 3.10 database of OpenLCA 2.0.0. [
52]. The materials selected for verification and the amount of their use per kilogram are presented in
Table 1,
Table 2 and
Table 3.
Subsequently, as part of the preparation of data for analysis, the functional unit and system boundaries were defined.
Due to limited lithium resources, many countries have started using other types of batteries. For example, a lithium–sulfur battery (Li-S) with a high theoretical specific capacity and specific energy density can increase efficiency five-fold compared with traditional lithium-ion batteries [
53]. Although lithium–sulfur batteries are of great interest and are considered one of the most promising new-generation batteries with high energy density, they are still far from satisfactory due to shortcomings in their practical application [
54]. Among other things, these batteries are characterized by a high rate of charging and discharging, including low cycle stability [
53].
There have also been studies with sodium ion batteries, which are considered cheaper alternatives and less susceptible to resource and supply risks [
55]. Sodium ion batteries are a promising, relatively inexpensive, and environmentally friendly solution in terms of energy storage for sustainable development [
56]. However, these batteries have low efficiency compared with the available electrode materials, so materials based on carbon, metals, and oxide alloys are still being sought [
57].
Another type of battery is the sodium–sulfur battery, which is considered one of the most effective energy storage systems [
58]. This type of battery is considered an effective replacement for lithium-ion batteries, mainly because it has a larger capacity, is more environmentally friendly, and is characterized by lower production costs [
59]. Currently, the sodium–sulfur battery is perceived as one of the strongest solutions to stabilize the grid, supporting the efficiency and usability of renewable energy technologies. Furthermore, from a practical point of view, it is characterized by a long discharge time and a service life that reaches up to 15 years [
60].
Although lithium-ion batteries are still considered the most desirable, and their satisfactory performance and low price in many cases means that the demand for these technologies will constantly increase and will reach even 2–3.5 TWh by 2030 [
61], so a sodium–sulfur battery seems to be advantageous and promising. Therefore, it is possible to say that lithium–ion batteries will continue to be popular, but the development of technology and research in this area may result in their replacement in many cases with more environmentally friendly and efficient types of batteries.
There are also hydrogen fuel cells that outperform lithium-ion batteries in terms of energy storage density and therefore have a longer range. Additionally, they are lighter, more compact, and have favourable potential for reducing emissions. Hence, these attributes may suggest that they are more favourable in environmental terms [
62]. However, unfortunately, they are characterized by high production costs, low hydrogen energy density, limited safety, and limited access to refuelling infrastructure, including the complexity of hydrogen storage and transport. However, technological development and political activities indicate that in the future they may become important from the point of view of sustainable transport development [
63].
A functional unit is a quantitative description of the functions of a product, and is the basis for carrying out calculations involving environmental loads. The use of a functional unit ensures quantitative measurement of environmental burdens and comparability of results [
64]. The functional unit can be freely adapted to the product. Based on other studies, for example [
35,
50], it was assumed that the functional unit for the analyzed batteries was 1 kg of material per 1000 kWh of energy stored in these batteries [
49]. Furthermore, following the authors of a previous study [
50], it was assumed that the average weight of batteries used in electric vehicles was approximately 300 kg. All data covering the materials of the tested batteries were converted according to this functional unit.
A system boundary is a set of criteria that define the unit processes, inputs, outputs, and environmental loads to be analyzed [
65]. The unit process consists of separate phases (stages) of the life cycle [
64]. In certain cases, the system boundaries in LCA may also refer to a specific geographical area, time range, or data related to the product or process [
66,
67]. The conducted research determined the boundaries of the system, including the analysis of environmental loads in the first phase of LCA, i.e., the extraction and acquisition of materials for batteries for passenger vehicles, that is, lithium-ion, lithium iron phosphate and three-component nickel–cobalt–manganese oxide, as presented in
Figure 1.
The scope of this research was reduced to the analysis of environmental burdens in relation to the ecological footprint, which is one of the key environmental burdens [
69]. Ecological footprint is used to measure the level of natural resources consumed and waste generated, among other things, as a result of human activity [
26]. It is the main indicator for assessing human impact on ecosystems and the biosphere [
69]; therefore, reducing it is a leading challenge, including improving the quality of the climate [
70]. The literature review presented in [
71] confirms that this is an important problem, and climate change has been the most common scope in studies conducted so far that cover the environmental impact of batteries for electric vehicles. The ecological footprint analysis included carbon dioxide (CO
2) emissions, land occupation (considered as land development and modernisation), and nuclear energy consumption [
26]. Due to the fact that the categories covered a large number of environmental burdens, the scope of this research was limited to the main burdens in each ecological footprint category. The main loads were considered to be those that had the highest emissions (environmental impact) among all those verified. As part of the analysis, a conversion unit was selected for the ecological footprint criteria, which was a square meter of impact per year of a given impact (m
2a).
4. Conclusions
Reducing the negative impact of electric vehicle batteries remains a challenge. As part of their sustainable development, it is important to find the sources of the main environmental burdens in the individual phases of the life cycles of these batteries. Therefore, the aim of this investigation was to perform an in-depth comparative analysis of electric vehicle batteries. The subjects of the research were popular batteries, i.e., lithium-ion, lithium iron phosphate, and lithium nickel cobalt manganese. They were analyzed in terms of environmental burdens, including ecological footprint criteria, i.e., carbon dioxide (CO2) emissions, land use, and nuclear energy emissions. The analyses were based on data from the GREET model and data from the Ecoinvent database in the OpenLCA program. During the analysis, the main environmental burdens were identified, i.e., hard coal, production of quicklime, cogeneration of heat and electricity (natural gas, conventional), road construction, hard coal mine operations, phosphate rock beneficiation (wet), phosphoric acid production, softwood forestry (spruce, pine), hardwood forestry (birch), and underground uranium mine exploitation. As a result, it was shown that in the adopted scope of this research, the most advantageous battery was the lithium iron phosphate. This battery was characterized by the smallest amount of environmental burden resulting from the ecological footprint in the phases of extracting and processing the materials used in it. However, the least advantageous was the lithium-ion battery. Additionally, to minimize the main environmental burdens, activities for improvement are proposed, resulting from a synthesized review of the literature.
A certain limitation of the conducted research is its focus on the first phases of the life cycle, i.e., the extraction and processing of materials. Additionally, the research results may have been different if the study had taken into account specific aspects, e.g., the location of material extraction. Within the adopted scope of this research, the results constitute a basic view of the basic activities and processes in the extraction and processing of lithium-ion materials and their variants.
Therefore, future research will aim to extend this research to subsequent phases of the life cycles of selected batteries, including other types. It is also planned to expand the analysis to include economic aspects, including qualitative ones, which will include customers’ and other interested parties’ satisfaction with the use of the batteries as well as vehicles powered by them.
The results obtained from the analysis can constitute the basis for taking actions aimed at reducing negative environmental impacts arising in the phases of extraction and processing of battery materials for electric vehicles. At the same time, they can be used by manufacturing companies and also by companies dealing with the extraction and processing of materials as part of their efforts to achieve sustainable development.