With the advancement of technology and the improvement of living standards, batteries have become essential energy storage devices, widely used in mobile electronic equipment, electric vehicles, and renewable energy storage battery systems. However, due to their limited service life, the large-scale generation of spent batteries poses a serious threat to the environment. Waste batteries contain heavy metals and hazardous chemical substances, which, if improperly treated, can cause long-term ecological pollution, endanger human health, and result in the loss of valuable metal resources such as lithium, cobalt, and nickel. Therefore, from the perspectives of environmental protection and resource utilization, the efficient treatment and recycling of spent batteries are of great importance for achieving resource circularity and sustainable development.
Battery Applications and Market Growth
Over the past approximately 200 years, batteries have served as an essential energy storage device, widely applied in portable electronics, electric vehicles, and numerous other fields due to their low cost, safety and stability, high conversion efficiency, and good environmental adaptability [1]. However, with the rapid pace of consumption upgrades and the continuously growing demand for electric vehicles, it is estimated that in the period from January to June 2024, domestic and international markets will respectively sell 318.1 GWh, 84.5 GWh, and 23 GWh. The production and sales of new energy vehicles reached 4.929 million units, representing a year-on-year growth of 30.1% and 32.0%, respectively, while Chinese electric vehicle exports totaled 1.0849 million units, a 36.9% increase compared with the same period last year.
Battery Lifespan and Waste Generation
In addition, data shows that lead-acid batteries generally have a lifespan of 2–3 years, nickel-metal hydride batteries 3–5 years, and lithium-ion batteries 2–6 years. This short lifespan has resulted in the generation of a large number of spent batteries. According to predictions from the China Business Industry Research Institute, the quantity of retired power lithium ion batteries in China will reach 1.04 million tons by 2025 and increase to 3.5 million tons by 2030. It is further estimated that the market size for power battery recycling in China will reach approximately RMB 140 billion by 2030, about nine times larger than in 2022.
Challenges in Recycling and Market Regulation
However, due to outdated standards, a limited number of qualified enterprises, and weak supervision, a large portion of spent batteries ends up in small workshops, posing significant safety risks and seriously hindering the standardized development of China’s battery recycling market. By 2023, the standardized recycling rate for new energy vehicle power batteries in China was less than 25%, with over 70% of spent batteries entering illegal recycling channels. In 2018, the total amount of retired power batteries in China reached 74,000 tons, of which only 5,472 tons were properly recycled, accounting for just 7.4% of the total retired batteries, far below the forecasted values.
Environmental and Health Risks
Improper treatment of electrode materials and electrolytes in spent batteries can lead to severe environmental pollution due to the release of metal ions such as nickel, cobalt, and manganese, as well as other organic compounds, which may also pose risks to human health. At the same time, these materials possess significant economic value. Without proper recycling, not only would valuable resources be wasted, but China’s dependence on iron ore would also increase, potentially affecting national energy security.
Resource Value and Strategic Significance
For instance, the content of cobalt, lithium, and nickel in cathode materials is significantly higher than their concentrations in natural ores, reaching approximately 5%–20%, 5%–7%, and 5%–10%, respectively, and also containing trace elements such as copper, aluminum, and iron. Lithium resources exhibit clear geopolitical distribution patterns, and recycling can reduce dependence on foreign supply while enhancing national resource security. Efficient recovery of valuable metals from spent lithium-ion batteries not only generates considerable economic benefits but also holds important geopolitical significance.
This review summarizes battery types, electrochemical systems, and their operating principles. It provides a comparative analysis of early 19th-century battery designs, such as zinc–carbon and lead–acid batteries, and modern battery technologies, including nickel–metal hydride (NiMH) and valve-regulated lead–acid (VRLA) batteries, focusing on their reaction mechanisms, advantages and disadvantages, and applicable fields, as detailed in Table 1. The review emphasizes that future battery technologies will continue to be optimized toward longer lifespans, lower costs, and improved environmental performance to meet the diverse demands of residential, industrial, and aerospace applications.
The basic structure of the vast majority of batteries typically includes a cathode, an anode, an electrolyte, a separator, and a casing. Taking lithium-ion batteries as an example in terms of composition: the cathode material usually contains high-valence metals, while the anode material primarily consists of carbon-based materials such as graphite, metallic materials, or silicon materials, with carbon-based materials being the most common. For example, in alkaline batteries and zinc-carbon batteries, the anode is mainly composed of metallic zinc, whereas manganese dioxide serves as the cathode.
Currently, the electrolytes in use are primarily liquid electrolytes (e.g., lithium hexafluorophosphate) and solid electrolytes (e.g., oxides, sulfides, polymers, etc.). The former offers higher ionic conductivity, while the latter provides superior safety performance. Battery separators, typically made from polyethylene (PE) or polypropylene (PP), can be classified as single-layer PE or PP membranes, or as three-layer PP/PE membranes. The casing materials are generally composed of metals or composite materials.
Hazards of Spent Batteries
Unrecycled spent batteries pose significant environmental and health risks. Heavy metals and toxic substances in the battery leachate can contaminate soil and waterways, disrupting the natural ecosystem. These pollutants can gradually accumulate in the land and crops, eventually entering the human body and posing potential health threats. Emerging contaminants in batteries—such as metallic nanostructures, carbon-based materials, and ionic liquids—have also been extensively studied. While these materials can enhance battery performance, they may also cause severe environmental hazards. For example, metallic nanostructures can improve storage capacity and energy efficiency, but they tend to aggregate, leading to performance degradation. Carbon-based materials, such as graphene and carbon nanotubes, may exert toxic effects on aquatic ecosystems. Ionic liquids can accumulate in soil and water, producing cytotoxic effects on microorganisms.
Furthermore, due to insufficient ecotoxicological research, limited recycling technologies, and regulatory gaps, the environmental risks associated with new battery materials require greater attention.
The discovery of graphene-based materials (GFMs) has raised concerns regarding their ecological impact, particularly their toxic effects on aquatic organisms. Studies have shown that GFMs exhibit toxicity to bacteria, algae, invertebrates, and fish, adversely affecting their survival, growth, and reproduction. For instance, graphene oxide (GO) can inhibit algal growth and induce oxidative stress, leading to cellular damage. The stability and mobility of GFMs in aquatic environments are influenced by both their intrinsic physicochemical properties and the physicochemical parameters of the water. Their behaviors in water, such as adsorption and aggregation, can alter their distribution and ultimate fate in aquatic systems.
Currently, environmental safety guidelines for GFMs are incomplete, and standardized testing methods are lacking. Therefore, further research is needed to determine their actual environmental concentrations and long-term effects, in order to establish scientifically sound safety guidelines and management strategies.
Waste Battery Management Solutions
The main disposal methods for spent batteries include incineration, landfill, and recycling [16]. Susana Xará et al. evaluated the entire lifecycle of batteries, from consumer disposal to final treatment or incorporation into the environment, using the Life Cycle Assessment (LCA) method. The study found that landfilling has the greatest impact in terms of land occupation and long-term groundwater contamination, while incineration primarily affects air emissions and resource utilization. In contrast, recycling offers significant advantages for environmental protection and resource recovery. Recycling processes generally involve pretreatment, metal leaching and extraction, and product preparation [17] (see Figure 2). Pretreatment includes discharging, manual disassembly or mechanical separation, and separating cathode materials from aluminum foil. Common methods include solvent dissolution, ultrasonic-assisted separation, thermal treatment, and mechanical separation.
Currently, metal leaching and extraction processes mainly involve traditional pyrometallurgy and hydrometallurgy, as well as emerging bio-metallurgy techniques (specific differences are summarized in Table. Pyrometallurgy involves high-temperature treatment of spent batteries to enrich and precipitate metal elements. The process begins with dismantling and crushing the batteries to remove non-metallic components and obtain electrode materials. Subsequently, the electrode materials undergo roasting, including reduction and oxidation steps, to transform them into more manageable forms. High-temperature treatment is then combined with fluxes and reducing agents to produce alloys or metallic elements, which are finally recovered through physical and chemical separation methods.
Although pyrometallurgy is highly effective for complex spent batteries, such as lead-acid, nickel-cadmium, and zinc-manganese batteries, it is energy-intensive and environmentally polluting. Components like lead, cadmium, zinc, and mercury can volatilize or precipitate at 300–400°C, necessitating careful handling. Consequently, pyrometallurgy remains the primary method for recovering these metals.
Hydrometallurgy employs chemical solvents to dissolve metal elements from spent batteries, followed by separation and extraction using chemical and physical techniques. The process begins with battery dismantling and crushing to obtain electrode materials, which are then leached using acidic or alkaline solutions to dissolve metal elements. The resulting solutions are purified through ion exchange, solvent extraction, or other methods to remove impurities. Finally, heavy metals are recovered from wastewater through precipitation and electrolysis. Hydrometallurgy is particularly suitable for high-purity metal recovery from spent nickel-metal hydride and lithium-ion batteries, especially for valuable metals such as cobalt and nickel. However, this method generates salt-containing wastewater that requires treatment and may cause secondary pollution.
Bio-metallurgy involves using microorganisms and their metabolic products to extract metal elements from spent batteries efficiently. The process includes dismantling damaged batteries to obtain electrode materials, followed by bioleaching under suitable conditions using specialized microbial media to dissolve the metals effectively. Subsequent purification steps employ ion exchange and solvent extraction, and the metals are finally recovered through precipitation and electrolysis. Bio-metallurgy is particularly valuable for the recovery of high-value metals such as nickel and cobalt.
