The rapid development of new energy vehicles has led to a large-scale retirement of power batteries. It is predicted that by 2025, China's retired power batteries will reach 600,000 tons, with a market size exceeding 10 billion yuan. Improper disposal of these used batteries will cause serious environmental pollution. So, how should used batteries be handled? Recycling or becoming a source of pollution?
Power batteries are the "heart" of new energy vehicles, and their performance and lifespan determine the vehicle's performance and safety. Generally, when the battery capacity drops below 80%, it can no longer meet the vehicle's power requirements and needs to be replaced or scrapped. These retired batteries contain large amounts of non-ferrous metals and toxic substances, such as cobalt, nickel, lithium, and fluorine. If they are carelessly discarded or landfilled, they will cause serious pollution to the soil, water sources, and air. Therefore, proper recycling of power batteries is of great significance for protecting the ecological environment, improving resource utilization efficiency, and ensuring the sustainable development of the new energy vehicle industry.
Currently, the recycling of power batteries mainly involves two methods: cascade utilization and regeneration.
Second-hand utilization refers to the process of reusing retired power batteries after testing, sorting, and repair, for applications in other fields such as energy storage, communication base stations, and solar energy. This method can extend battery life, reduce environmental impact, and also bring certain economic benefits. However, second-hand utilization also faces some challenges, such as inconsistent standards, immature technology, and an unregulated market. Currently, second-hand utilization in my country is still in the exploratory stage, mainly focusing on demonstration projects, and a complete business model has not yet been formed.
Recycling refers to the process of dismantling, separating, and purifying retired power batteries to recover valuable metal elements, and then reusing these materials in new batteries or other products. This method maximizes resource utilization, reduces dependence on external sources, and lowers the cost of new energy vehicles. Currently, recycling is the mainstream recycling method in the industry. According to the "Industry Standard Conditions for Comprehensive Utilization of Waste Power Batteries for New Energy Vehicles (2019 Edition)" issued by the Ministry of Industry and Information Technology, comprehensive utilization enterprises should possess corresponding qualifications and conditions, and implement a dynamic adjustment mechanism of "entry and exit".
There are three main technical routes for recycling: physical recycling, wet recycling, and pyrometallurgical recycling.
Physical recycling separates various components from the battery through crushing, sieving, and magnetic separation, and then repairs the materials. This method can achieve fully automated, pollution-free dismantling of all components, but it is labor-intensive and makes the recovery of other valuable metals difficult.
Wet recycling involves dissolving metal elements from batteries using acid or alkaline solutions and then extracting them through chemical precipitation, solvent extraction, or other methods. While this method offers high-efficiency metal recovery, it is a lengthy process involving corrosive solvents and poses risks such as wastewater pollution.
Pyrometallurgical recycling involves reducing metal oxides in batteries to metals through high-temperature pyrolysis, followed by further processing. This method is simple and can recover more heavy metals, but it has a low yield, high energy consumption, and generates some waste pollution.
Comparing current recycling technologies in my country, wet recycling boasts high metal recovery rates and produces high-purity reprocessed products, making it the mainstream technology in the industry. The cost of wet recycling primarily consists of chemical reagents and energy expenses. Therefore, improving the efficiency of chemical reagent use and reducing energy costs in the recycling process will be key areas for power battery recycling companies to build cost advantages. The main types of wet recycling processes include inorganic acid leaching, organic acid leaching, alkaline leaching, reducing leaching, and enhanced leaching. In recent years, organic acid and alkaline leaching processes have been widely explored due to their good biodegradability and low secondary pollution. Furthermore, some reducing agents and enhancement methods have been added to the leaching system to improve leaching rates and metal recovery rates.
Electric vehicle batteries include lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lithium-ion batteries, polymer lithium batteries, zinc-air batteries, and fuel cells. Among these, lead-acid batteries are further categorized into valve-regulated lead-acid maintenance-free batteries, gel lead-acid batteries, nickel-metal hydride batteries, and lithium-ion batteries.
Currently, the main types of batteries used are lead-acid batteries and lithium batteries. Lead-acid batteries are bulky but inexpensive, have stable performance, and are technologically mature; lithium batteries are more expensive but have a longer lifespan and are more portable. I bought a Tianneng lead-acid battery from Daoyixing Mall two years ago in April, and it's still working well for me. Batteries still need proper maintenance.
The battery is the power source for electric vehicles. Most electric vehicles today use lead-acid batteries, which are inexpensive and cost-effective. Because these batteries are rechargeable and can be used repeatedly, they are called lead-acid batteries.
In 1860, the Frenchman Planté invented a battery using lead electrodes, which was the precursor to the lead-acid battery.
The following four types of power batteries can be used in electric bicycles: valve-regulated lead-acid maintenance-free batteries, gel lead-acid batteries, nickel-metal hydride batteries, and lithium-ion batteries.
lead-acid batteries
Lead-acid batteries are widely used and extensively studied by various electric vehicles in various countries due to their low price, abundant material sources, high specific power, mature technology and manufacturing process, and high resource recycling rate. Electric bicycles, as a labor-saving, convenient, fast, comfortable, inexpensive, and zero-emission personal transportation tool, have been widely accepted by people and have received attention from relevant national departments. The research group on the development strategy of the light electric vehicle industry, which was participated in by the Development Research Center of the State Council, the National Development and Reform Commission, the Ministry of Construction, the Ministry of Science and Technology, and other ministries, put forward a research report on the development strategy of the light electric vehicle industry. The national ownership of electric bicycles has reached more than 30 million. More than 95% of electric bicycles use valve-regulated lead-acid batteries. [1]
The vast majority of commercially available electric bicycles use sealed lead-acid batteries, which do not require frequent water replenishment and are maintenance-free. The main chemical reaction is: PbO2 + 2H2SO4 + Pb ← Charging/Discharging → 2PbSO4 + 2H2O
During charging, lead-acid batteries release the sulfuric acid from the spongy lead at the anode and cathode into the electrolyte, transforming into spongy lead and lead oxide, respectively, thus increasing the sulfuric acid concentration in the electrolyte. Conversely, during discharge, the lead oxide at the anode and the spongy lead at the cathode react with the sulfuric acid in the electrolyte to form lead sulfate, while the sulfuric acid concentration in the electrolyte decreases. When a lead-acid battery is undercharged, the lead sulfate at the anode and cathode cannot be completely converted into spongy lead and lead oxide. If undercharging is prolonged, lead sulfate crystallizes, causing sulfation of the plates and deteriorating battery quality. Conversely, if the battery is overcharged, the amount of oxygen produced at the anode exceeds the adsorption capacity of the cathode, increasing the internal pressure of the battery, leading to gas leakage, reduced electrolyte, and potentially softening or shedding of active materials, significantly shortening battery life.
Overall performance has been greatly improved.
Over the past decade, the overall performance of valve-regulated lead-acid batteries for electric bicycles has greatly improved. Take the 6-DZM-10 battery as an example. In 1997, this type of battery suffered from several problems: insufficient capacity (discharge capacity at 2h rate (5A) did not reach 10Ah); low specific energy (specific energy at 2h rate was less than 30Wh/kg); short lifespan (cycle life at 100% depth of discharge was only 50-60 cycles (before capacity dropped to 8Ah; the same applies below), and a service life of only 3-5 months.
By 2003, the 2-hour rate (5A) discharge capacity reached 11-13 Ah; the 2-hour rate specific energy reached 33-36 Wh/kg; the cycle life at 100% depth of discharge reached 250-300 cycles, and the service life could reach more than 12 months. The problems of valve-regulated lead-acid batteries for electric bicycles were basically solved.
The deep cycle life performance of this type of battery has made new and breakthrough progress. The main performance is as follows: the initial discharge capacity at 2h rate (5A) reaches 14Ah; the specific energy at 2h rate reaches 38Wh/kg; the cycle life at 100% discharge depth exceeds 400 times, the total discharge capacity is 4500Ah, and the corresponding cumulative driving mileage is about 18000km (based on 4km/Ah, the same below). The highest deep cycle life exceeds 600 times, the total discharge capacity is 6151Ah, and the corresponding cumulative driving mileage is about 24600km. If the capacity is less than 7Ah as the end of life, the deep cycle life is 943 cycles, the total discharge capacity is 8710Ah, and the corresponding cumulative driving mileage is about 34800km. If the battery pack with a deep cycle life of 250 cycles or a total discharge capacity of 2250Ah and a corresponding cumulative driving mileage of 9000km can be guaranteed to be used for 1 year. [1]
Pay attention to compatibility with the charger.
Over the years of practical use, electric bicycle manufacturers and battery manufacturers have gradually come to realize the importance of matching batteries with related equipment in electric drive systems, especially with chargers. Manufacturing quality is a prerequisite for battery quality, but only when used with a matching charger can a high-quality battery achieve its superior performance; otherwise, a high-quality battery cannot fully realize its potential superior performance. [1]
Due to differences in formulation, structure, acid concentration, etc., the appropriate charging parameters of batteries from different manufacturers are different. For example, in our study, we found that the charging parameters of batteries from different manufacturers in the constant voltage stage can differ by 1.5~2.0V (for 36V battery packs). The basic requirements for appropriate charging parameters are: to ensure that the battery can be fully charged and that the battery capacity will not be abnormally reduced due to undercharging; and to ensure that the battery will not suffer serious water loss and thermal runaway due to overcharging during its entire lifespan. [1]
Lead-acid batteries for pure electric vehicles
The open-type lead-acid batteries used in early pure electric vehicles adopted the research results during the Eighth Five-Year Plan period and have achieved successful experience of being usable for 19 months (120,000 kilometers). The key is to accumulate a set of system matching experience and careful maintenance experience in controlling the charging method, discharge depth, timely water replenishment, etc. In recent years, four-wheeled micro electric vehicles (including sightseeing vehicles, patrol vehicles, golf carts, short-distance road vehicles, etc.) have developed rapidly, and most of them use open-type lead-acid batteries. The corresponding models of batteries are favored by battery manufacturers. [1]
The electric vehicle uses a new valve-regulated sealed lead-acid battery, with the following performance characteristics: 55Ah capacity at 3h rate; specific energy of 33Wh/kg and 84Wh/L at 3h rate; and a cycle life of over 400 cycles at 75% depth of discharge. It is believed that the successful experience of valve-regulated lead-acid batteries used in electric bicycles can be extended to valve-regulated lead-acid batteries used in pure electric vehicles, and the performance will be further improved. [1]
Lead-acid batteries for hybrid electric vehicles
Hybrid electric vehicles are now basically divided into three categories: mild hybrid (i.e., the electric system is mainly used for starting and recovering braking energy, and the 42V electric system that will be promoted in all cars belongs to this type), medium hybrid (i.e., the electric system is used for starting, recovering braking energy and driving for medium and short distances), and heavy hybrid (i.e., the electric system is used for starting, recovering braking energy and driving for longer distances, also known as plug-in). [1]
It has been clearly stated in domestic and foreign literature that valve-regulated lead-acid batteries have advantages in mild hybrid electric vehicles, mainly because of their low cost, mature technology, and reliable performance. For valve-regulated lead-acid batteries used in moderate hybrid electric vehicles, ALABC (Advanced Lead-Acid Battery Consortium) is organizing research and development to compete with MH-Ni batteries for the market of moderate hybrid electric vehicles. The wound bipolar battery and TMF (metal film) battery have been launched and tested on vehicles. In the field of severe hybrid electric vehicles, lead-acid batteries have low specific energy and cannot meet the requirements of electric systems for long-distance driving. [1]
Gel batteries
It is an improvement over ordinary lead-acid batteries with liquid electrolytes. It uses a gel-like electrolyte, with no free liquid inside. It has a large electrolyte capacity and heat capacity for the same volume, and strong heat dissipation ability, which can avoid the thermal runaway phenomenon that is common in ordinary batteries. The electrolyte concentration is low, which has weak corrosion to the plates. The concentration is uniform and there is no acid stratification.
Currently, the recycling and utilization of retired power batteries from new energy vehicles has attracted widespread attention and has become a pressing problem that needs to be solved in the development of my country's new energy vehicle industry.
In my opinion, to effectively address this issue, relevant government departments need to take timely action, and industry enterprises need to work together to accelerate the improvement of the management system for the recycling of new energy vehicle power batteries. This will create a resource-efficient utilization system with full-cycle management and recycling across the entire industry chain, guiding all relevant parties to play their active roles and jointly promote the healthy development of the power battery recycling market.
The surge in the number of used power batteries being recycled, the chaotic recycling channels, the increased environmental risks, and the growing safety hazards have seriously hindered the improvement of the efficiency of recycling resource utilization.
According to independent research, in 2021, my country's new energy vehicle sales exceeded 3.5 million units, with a total installed capacity of 154.5 gigawatt-hours, representing a year-on-year increase of 142.8%. This indicates that the power battery industry has entered a period of rapid growth. At the same time, the number of retired power batteries is also gradually increasing. Based on the lifespan of pure electric vehicle power batteries, approximately 1.3 million pure electric vehicles sold before 2018 will gradually reach the end of their service life. Data shows that the cumulative amount of retired new energy vehicle power batteries in my country has exceeded 200,000 tons, and is expected to reach 780,000 tons by 2025.
Currently, the battery recycling market in some parts of my country is quite chaotic. Some large, legitimate companies engaged in the recycling and utilization of used power batteries from new energy vehicles report that only one-quarter of the power batteries recycled through formal channels account for the entire industry, while more than half end up in informal, small workshops. These companies face difficulties such as insufficient battery recycling quantities, inadequate supply, and being squeezed out of their survival space by unregulated individuals and small workshops.
The large influx of used power batteries into small workshops, where dismantling is done manually in rudimentary and remote locations, poses a serious risk of environmental pollution. Even more worrying is that after the purchased power batteries are manually dismantled by workers, they are sorted and assembled into other batteries of different specifications. These batteries are not only widely used in low-speed electric bicycles, electric tricycles, and home energy storage and backup power supplies, creating safety hazards, but also disrupt market order and impose unfair and significant cost burdens on compliant manufacturers.
