Publication
Increase the accuracy of carbon footprint for Li-ion battery
mai 2023
Industrie
Publication
Increase the accuracy of carbon footprint for Li-ion battery
A mandatory step to structure a low-carbon supply chain in Europe (and elsewhere)
Transportation is one of the most carbon-intensive sectors, and in the EU, road transport is responsible for 15% of greenhouse gas (GHG) emissions[1].
To comply with the Paris Agreement, signatory countries must set reduction targets and implement action plans for this sector.In the EU, the "Fit for 55" package mandates that all new cars introduced to the market should be "zero-emission" vehicles by 2035, with a ban on the sale of new petrol and diesel cars, and that they should comprise 50% of the total fleet by 2050. Hence, car manufacturers are increasingly active in manufacturing and launching new Battery Electric Vehicles (BEVs).
However, the transition to a fleet of electric cars comes with many technical, geopolitical and ethical challenges. For example, there is the issue of the electricity network's ability to handle the increased demand, the reliance on specific materials for battery manufacturing, and the working conditions in the mines where those materials are extracted (For more information on the deployment of electric cars, Carbone 4 has published an article on the subject)
Beyond these issues, the transition requires us to question our mobility habits. For instance, the weight of cars has increased by 30% on average in France in the last 30 years. This trend is increasing the GHG emission linked to the fuel consumption of the mobility. When it comes to Battery Electric Vehicles (BEV), another key ecological criterium is the manufacturing of the vehicle. In this regard, an electric SUV (Sport Utility Vehicle) may not be a “low-carbon” option as the carbon footprint of manufacturing, already the largest emissions category for a BEV, increases even further due to the increased material needs and the larger battery to meet its energy needs.
Electric vehicles are only part of the solution, and developing active modes of transport (walking, cycling) and public transport are also crucial. The cornerstone of the transition is also restraint in transport: reducing the distances traveled and the frequency of travel.
The topic of BEVs is complex and sensitive, and much has been said and written on the subject. Our aim at Carbone 4 is to provide technical insights to support the legitimate questions that can be raised. In this publication, we focus on the carbon footprint of Li-ion batteries throughout their lifecycle[2] with three main objectives:
This publication is divided into three parts. First, we review the upcoming regulatory requirements in Europe regarding batteries for mobility. Then, we present our methodological approach and how it meets this new regulatory framework. Finally, we will present two contrasted case studies: one battery manufactured in China versus one manufactured in France.
The European metallurgical industry, particularly in battery metals, is heavily dependent on imports due to a lack of competitiveness compared to foreign leaders, especially the Chinese industry. This disadvantage is fueled by more lenient environmental regulations overseas. However, the recently introduced European Critical Raw Materials Act[3] aims to reverse this trend and promote greater self-sufficiency.
Creating a European battery sovereignty is more important than ever as it would help control greenhouse gas emissions from battery manufacturing and support the EU's transition to electric mobility. The European Commission’s metallurgical roadmap outlines key priorities to compete with American and Asian players[4]:
In the field of Li-ion batteries, many initiatives are already emerging across the value chain. For example:
On December 9th, 2022, the Council and the European Parliament reached a preliminary agreement on a proposal for a regulation about batteries and waste batteries. The goal of this regulation is to ensure the sustainability and competitiveness of EU battery value chains[11].
Specifically for electric vehicle batteries, the regulation establishes rules for:
Additionally, the regulation addresses technical issues such as end-of-life collection and battery design optimization. For more information please refer to this document.
One of the main objectives of this regulation is to introduce a battery passport for all batteries, which will provide information to the public about the batteries' sustainability requirements. It will also give remanufacturers, second-life operators, and recyclers up-to-date information about the batteries. A QR code on the battery will provide access to information about :
The ultimate aim of the battery passport is to ensure that batteries introduced on the European market do not exceed a certain manufacturing emission threshold, emphasizing the importance of accurately calculating battery emissions.
Li-ion batteries are rechargeable batteries that use lithium ions to store energy. Battery packs found in electric vehicles are an assembly of modules that are made up of cells connected to each other, all supervised by a dedicated electrical circuit. The number of cells, the size of each cell and the way they are arranged determine both the voltage delivered by the battery and its capacity, i.e. the amount of electricity it is able to store (in kWh).
A battery cell consists of 4 parts : a cathode (positive electrode) and an anode (negative electrode) immersed in an electrolyte (an ionic conductive liquid) and separated by a separator (see diagram below). During the operating phase, the potential difference between the anode and the cathode causes ions to circulate inside the electrolyte and creates an electric current. Conversely, during the recharging phase, the energy transmitted by the charger causes electrons to flow back from the positive to the negative electrode, and the lithium ions flow to the negative electrode to balance the electrical charges.
The assembly process for Li-ion batteries involves several steps
The assembly process is very energy-intensive. Almost 50% of its energy consumption is due to drying and solvent recovery processes during the electrode manufacturing process. In addition, the entire assembly process takes place in a dry room (humidity less than 5%) which ensures a controlled-contamination environment. This dry room generates an energy consumption that depends on the climate (humidity level) and is around 20% to 30% of the total energy consumption for the assembly.
The GHG emissions from assembly are therefore largely dependent on the energy source used for drying: natural gas or electricity. If the electrodes are dried with electricity, the emissions are driven by the carbon intensity of the grid. Since most batteries are assembled in China (more than 75%), the process is far more emissive than in Europe as the electricity mix uses large quantities of highly carbon-intensive coal.
The assembly however is only one part of the global carbon footprint of the battery. One of the main questions to be answered lies in the metals of interest: the active materials which react chemically to produce electrical energy when the cell discharges. In all current Li-ion chemistries, the active material for the anode is graphite, which can be enriched with silicon. However, for the cathode, the active materials differ based on the specific chemistry, but they always contain lithium. How are these materials extracted and transformed into battery grade metals ? This article will focus on examining the following materials: lithium, nickel, manganese, cobalt, and graphite.
▶️ Lithium : There are two main production pathways for battery-grade lithium.
- Solid pathway - From spodumene ore (LiAlSi2O): Australia is the world's largest producer of lithium through this production pathway[15]. The first step involved in the manufacturing of battery-grade lithium from spodumene ore is underground mining. The crushed rock is mixed with a concentrated acid solution and heated in a rotary kiln to a high temperature of 950°C. This process converts the lithium-containing minerals into a water-soluble form. The resulting mixture is then cooled and treated with water to dissolve the lithium salts. The lithium solution is then purified using a series of chemical reactions that eliminate impurities such as iron and aluminum. The purified solution is treated with soda ash (sodium carbonate) to form lithium carbonate which can be transformed into lithium hydroxide if required (the type of lithium used - carbonate or hydroxide - depends on the battery chemistry). The grinding and heating steps are the most energy-consuming, with the grinding step using 15 to 17 kWh/ton of material processed.
- Liquid pathway - From brine: This brine is typically found in salt lakes, also known as salars, which are located primarily in the Andean plateau of the Chile-Argentina-Bolivia triangle. It can also be found in the Qaidam basin in China and the Clayton Valley in the USA. Within these lakes, lithium is present in a dissolved state and is typically in the form of LiCl.
The process of producing battery-grade lithium from brine is five times less emission-intensive than from spodumene. However, brine reserves are more limited. To meet the demand for battery-grade lithium, experts estimate that all existing sources of lithium will have to be exploited. Although other production methods exist such as using lepidolite, mica, jadarite, hectorite ores, lithium clay, and geothermal brines, the quantities produced from these sources remain small.
▶️ Battery-grade nickel is produced from nickel sulphate. Nickel sulphate can be produced by hydrometallurgy alone, by a High Pressure Acid Leaching and Base Metal Refinery (HPAL + BMR) process or by pyrometallurgy followed by hydrometallurgy (”pig iron” pathway).
- The process of hydrometallurgical production of NiSO4 (HPAL + BMR) involves several steps that use acid solvents and electrolysis to concentrate and purify the ore. This method has the potential to produce valuable co-products such as copper, cobalt, or iron. However, this process is not yet fully mature as it has only been around for about 30 years and opening a hydrometallurgical plant can still be a complex undertaking.
- The primary method for nickel production today is through the production of nickel pig iron. Originally, it was used as a cheaper alternative to pure nickel for the production of stainless steel. Nickel pig iron is made from low-grade nickel ore, coking coal, and a mixture of gravel and sand as an aggregate. The mixture is then heated in blast or electric furnaces, and impurities are removed through smelting. This process results in high greenhouse gas emissions. To produce NiSO4, the obtained ingots are further processed using solvent-intensive hydrometallurgical processes. Most nickel pig iron is produced in Indonesia and refined either on site or in China. Only countries with low costs and lax environmental policies can afford this highly energy and solvent-intensive process. In Europe, this method is simply not viable due to energy prices.
▶️ Manganese : the battery-grade manganese is in the form of MnSO4.
- Manganese sulfate (MnSO4) can be produced from either carbonate ore or pyrolusite ore. In the case of carbonate ore, the process involves milling, solvent extraction, and drying of the ore, followed by the addition of sulfuric acid, purification, and crystallization. In the case of pyrolusite ore, the process involves milling, reduction in a calciner, heating, drying, addition of sulfuric acid, purification, and crystallization.
▶️ Cobalt : The Copperbelt region in the Democratic Republic of the Congo and Zambia is responsible for producing most of the world's cobalt. Cobalt is obtained as a byproduct of the extraction of copper, nickel, and even lead ores. We did not delve into the production processes of cobalt in detail due to a lack of information on its carbon footprint. Therefore, we had to rely on existing literature such as GREET and EcoInvent to obtain the necessary information.
▶️ Graphite refers to a specific arrangement of carbon atoms in a crystalline form. This arrangement consists of a stack of planes, each made up of hexagons in a honeycomb pattern. There are two primary kinds of graphite - natural graphite, which is made from ores containing 5 to 30% carbon, and synthetic graphite, which is produced from petroleum coke. Synthetic graphite offers superior performance in terms of energy density and lifespan. China is the primary country for refining graphite and produces between 60% and 80% of the world's graphite.
- The most commonly used method of production involves several steps. Firstly, a process called flotation is used to separate minerals based on their hyprophilic/hydrophobic properties. Then, the ore is thermally purified at a temperature of 1000°C to obtain a material containing 98% carbon. Next, a chemical extraction process is used to further refine the material. Finally, the material is ground using a jet mill, which utilizes a high-speed jet of compressed air or inert gas to cause particles to impact each other.
- Another commonly used production method is the Acheson process. This process involves the same initial step of flotation, followed by heating the ore in graphite crucibles to a temperature of 3000°C, and then grinding the resulting material using a jet mill. However, the Acheson process is known for having low energy efficiency and also generates greenhouse gas emissions due to the consumption of the graphite crucibles during the process. Both of these production methods are used in China.
- There is another production process that is less carbon-intensive than the previous ones mentioned - the lengthwise graphitization (LWG) process. This method involves several steps, including flotation, forming, and baking. During the LWG process itself, the material to be graphitized is heated using the Joule effect instead of through conduction as in the Acheson process. This results in lower energy losses and produces graphite with a higher energy density.
Through calculating the carbon footprint at the manufacturing process level, we have been able to achieve a higher level of detail and identify significant differences from the average values found in existing literature. For example, GREET (Greenhouse gases, Regulated Emissions, and Energy use in Technologies)[16] results, which are sponsored by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy and assess the energy and emission impacts of battery electric vehicles (BEVs) from the initial production to disposal, are considered authoritative but still lack certain crucial information. Our primary findings are discussed below and highlight the fact that the current level of detail provided in literature is insufficient and needs to be increased and standardized in order to better assess the actual differences in carbon footprint between different types of batteries.
- In recent years, a production method for nickel sulphate from nickel pig iron has become increasingly popular in China. This method, which was not considered in the GREET model, has a carbon footprint that is approximately 4 times higher than that of nickel sulphate produced using the high pressure acid leaching process.
Our method of calculation enables us to identify the primary differences in carbon footprint between production processes, but there are some distinctions that are challenging to capture, such as the specific energy source used, the quantity of solvent required based on the mineral's purity level, the source of the solvents, and so on.
Over a period of 10 months, we collaborated with 10 stakeholders from the battery industry in Europe, including ERAMET, Verkor, Infinity Lithium, Tokai Cobex, EDF, Forsee Power, MTB, and Plastic Omnium. The primary objectives of our study were to:
Precisely quantify the carbon footprint of Li-ion batteries, particularly in the upstream part of the value chain.
Analyze the differences in carbon footprint among various production processes of batteries.
Facilitate the development of a sustainable and low-carbon European battery industry by contributing to the creation of efficient and ambitious regulations on batteries.
Through extensive discussions with the partners and their process experts, we gained valuable insights into the battery production routes and also accessed primary industry data. Additionally, we reached out to the PEF for reference. We developed a tool to calculate the carbon footprint of Li-ion batteries across their entire life cycle, allowing for further refinement by production process, country of assembly, and country of use.
By modeling two contrasting case studies, we aimed to understand the potential difference in GHG emissions between low-emission batteries and carbon-intensive ones.
The assumptions made for each case are :
The study shows that the largest part of the carbon footprint of Li-ion batteries (about 80%) is due to the upstream materials, rather than the assembly or usage.
The gap in carbon footprint over the lifetime between the battery with carbon-intensive materials and the one with less carbon-intensive materials is 60%. This is mainly due to the upstream materials (+70%) and the assembly (+70%) (see chart below). Within upstream materials, the largest differences in carbon intensity are observed for graphite (x30) and nickel (x3), which is consistent with the improvements to the model explained in Part III.
In conclusion, after refining the calculations for some materials, the carbon footprint falls between 77 and 221 kgCO2e/kWh, compared to the range of 53 to 68 kgCO2e/kWh calculated by the GREET laboratory for the same chemistry[17]. This highlights the need to continue improving the current calculations and establish an ambitious maximum threshold for the carbon footprint of batteries that are sold in the European market.
With the the carbon footprint values obtained, we demonstrate that the environmental benefits of an electric vehicle (EV) over an internal combustion engine (ICE) can be achieved three times faster if the battery contains materials with lower carbon intensity than those with higher carbon intensity.
Indeed, according to the “Fondation pour la Nature et l'Homme”[18], the carbon footprint of manufacturing a combustion engine city car ICV is 5.9 tCO2e, whereas that of a similar electric vehicle (excluding the battery) is 6.4 tCO2e - the difference being explained in particular by the higher quantity of ferrous materials for the electric car. So, according to our calculations of a battery’s carbon footprint, the manufacturing an electric vehicle (assembly + battery included) then emits between 10.4 and 17.9 tCO2e, i.e. more than a combustion engine car. The ecological advantage of an electric vehicle lies in its use, which is less carbon-intensive compared to burning fossil fuel. There is a specific point, known as the "kilometer tipping point," beyond which the excess carbon footprint of manufacturing the EV battery is offset by its use. This means that beyond this point, the EV becomes less carbon-intensive than a combustion engine car. Based on the average yearly distance travelled by car, which is 12,000 km[19], the car with the battery made of less carbon-intensive materials manufactured in France reaches the kilometer tipping point in approximately two and a half years after its introduction, while with the battery made of carbon-intensive materials manufactured in China, it takes six years of use before reaching the kilometer tipping point.
The carbon footprint of a Li-ion battery with the same chemistry and capacity can vary by up to three times depending on the production process used. Therefore, it's essential to consider the details of the materials and assembly process when manufacturing these batteries.Electric vehicles equipped with batteries manufactured in France using low-carbon materials have a lower carbon footprint (including both manufacturing and use) than ICE vehicles, approximately two and a half years after their start of use. However, with batteries made from carbon-intensive materials manufactured in China, it takes six years of use for the vehicle to reach the "kilometer tipping point.”
We believe that EU carbon footprinting standards should consider the origin and manufacturing process of the materials used. Additionally, the EU should set ambitious carbon performance thresholds for batteries in order to help build a European low-carbon battery industry, and avoid importing batteries from China or produced on European soil by Asian industries with a high carbon value chain.
Although there have been significant improvements in calculating the carbon footprint of Li-ion batteries, such as specifying the carbon footprint by production process for lithium, graphite, and nickel and assembly emissions by country of production, there still are areas of improvement.
Season 2 of this work on batteries could focus on:
1/ refining the model:
2/ being prescriptive on the carbon performance thresholds of batteries and the data to be reported by battery producers.
2.
At this stage, the closed loop recycling of batteries in Europe, enabling the reuse of recovered materials into new batteries, is still at the project stage so the lack of information did not enable us to include it in the calculations.
12.
European Commission, Suggestions for updating the Product Environmental Footprint (PEF) method
13.
European Commission, Environmental Footprint methods
14.
Proposal for a Regulation of the European Parliament and of the Council concerning batteries and waste batteries, repealing Directive 2006/66/EC and amending Regulation (EU) No 2019/1020, Council of European Union, January 2023
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