Recycling of Lithium Batteries and GHG Emissions

Lithium-ion batteries (LIBs) are now used in cell phones, laptops, and electric vehicles (EVs) because of their high energy per unit mass relative to other electrical energy storage systems. They also have a high power-to-weight ratio, energy efficiency, high-temperature performance, and low self-discharge. Most of today’s all-electric vehicles and plug-in hybrid electric vehicles (PHEVs) use lithium-ion batteries. The exact chemistry of these batteries often varies from those used for consumer electronics. Current challenges facing this industry revolve around reducing their relatively high cost (due to limited supply), extending their lifetime, and addressing safety concerns about overheating leading to explosions. Hence new solutions are needed for recycling and reuse of materials used in LIBs. Most components of LIBs can be recycled, but the cost of material recovery remains a challenge for the industry. Therefore, new solutions are needed. 

LIB applications are often labeled as “zero emissions.” However, this ignores the supply chain emissions generated in the procurement and production stages. LIBs are one of the main contributors to emitting greenhouse gasses (GHG) during EV manufacturing. In this case, recycling LIBs is recommended to reduce energy consumption, mitigate GHG emissions, and result in considerable waste savings. Additionally, the accelerating production of LIBs in the line of clean-energy technologies has led to a strong demand for minerals such as lithium (Li), cobalt (Co), and manganese (Mn). The spent LIBs could be considered the secondary source of these minerals. Finding an environmentally sustainable way of recovering these minerals from waste is critical. The increasing popularity of EVs has led to a surge in demand for lithium-ion batteries used to power these vehicles. In the US, EVs are expected to increase from 5% to 25% of all cars sold by 2030. As the number of EVs on the road continues to grow, so does the need for efficient and effective recycling of their batteries. 

Recycling LIBs can help reduce GHG emissions by reducing the energy needed to produce new batteries and preventing hazardous materials from entering the environment. This article will discuss how recycling batteries can help reduce GHG emissions and what steps can be taken to ensure that these batteries are recycled properly.

The production of LIBs requires a significant amount of energy, typically generated from burning fossil fuels such as coal or natural gas. This process releases large amounts of GHGs into the atmosphere, contributing to climate change. By recycling batteries instead of producing new ones, we can reduce the energy needed for production and thus reduce GHG emissions. Recycling LIBs helps prevent hazardous materials such as lead and cadmium from entering the environment. These materials can be toxic if released into water or soil systems, so they must be recycled properly. Several steps can be taken to recycle EV batteries properly and efficiently. First, manufacturers should design their products with recyclability in mind using materials that are easy to separate and recycle. This will make it easier for recyclers to process the materials without using additional energy or resources. Additionally, manufacturers should provide clear instructions on how consumers should dispose of their used EV batteries so they can be appropriately recycled. 

There are 3 recycling methods of LIBs: pyrometallurgy, hydrometallurgy, and direct physical recycling methods of EV batteries. The carbon emissions of pyrometallurgy, hydrometallurgy, and direct physical recycling methods are calculated in several studies.

Pyrometallurgical recycling process:

1. The carbon emission of the pyrometallurgical recycling process is 5.11 kg CO₂-eq/kWh.
2. The process involves high-temperature smelting batteries with a temperature of more than 1000 °C.
3. GHG emission results from the fossil fuel energy consumed in the metallurgical process.
4. The graphite in the anode cannot be recycled by pyrometallurgy, and the pyrolysis of graphite in a high-temperature environment will produce GHG emissions. 
5. High economic value, but poor ecological value. 

Hydrometallurgy recycling process: 

1. GHG emission of hydrometallurgy is 2.68 kg CO₂-eq/kWh, which is 47.6% lower than that of pyrometallurgy. 
2. Hydrometallurgy carries out 10 major steps of chemical treatment under low-temperature conditions, without high energy consumption and high carbon emission processes.
3. However, the process does generate a considerable number of toxic gases and waste solutions. 

Direct physical recycling

• The carbon emission of the direct physical recycling method is 3.65 kg CO₂-eq/kWh.
• Since the products of direct physical recycling are materials that can be directly used in battery production, the complicated material reproduction steps and secondary pollution are reduced. 
• The nickel-rich material used in the repair process, such as Ni_0.83Mn_0.09Co_0.08(OH)₂, Ni(OH)₂, or lithium compounds such as LiOH–Li₂SO₄ used in the heat treatment process, and energy consumption are the main sources of carbon emission.

Comparison in GHG emission reduction compared with non-cycled batteries

Although the recycling process of LIBs will produce carbon emissions, the recycled materials can be directly used to manufacture batteries, avoiding the carbon emissions caused by the mining and refining of raw materials. Hence engineers estimate the amount of GHG emissions reduction of LIBs versus virgin batteries.

GHG emission of remanufacturing batteries with recycled materials by

• Pyrometallurgy is 86.86 kg CO₂-eq/kWh, which is 4.8% lower than that of batteries produced with raw materials. 
• Hydrometallurgical is 60.77 kg CO₂-eq/kWh, which is 33.47% lower than that of batteries produced using raw materials. 
• Direct physical recycling is 43.92 kg CO₂-eq/kWh, which is 51.8% lower than that using raw materials. However, the physical recycling method is not mature in technology and is still in the stage of small-scale experiments. Developing efficient and mature physical recycling methods for large-scale applications is critical to reducing carbon emissions.