Lithium-ion batteries mainly rely on the embedding and escape of lithium ions in positive and negative electrode materials to transfer energy. Depending on the applicable equipment and location, lithium-ion batteries have cylindrical, long and square shapes, but all contain the following five parts: positive electrode, negative electrode, electrolyte, organic separator, and shell. Taking the common 1860 cylindrical lithium-ion battery as an example, the internal structure of the battery is that the positive electrode, organic separator, negative electrode and organic separator are arranged in sequence, and are wound and pressed around the central axis of the battery. The positive electrode generally uses aluminum foil as the matrix, and the positive electrode material is evenly coated on both sides of the aluminum foil, including a certain ratio of positive active material, conductive agent (such as acetylene black PP/PE, etc.) and binder (such as polyvinylidene disulfide (PVDF)). The positive active material generally uses lithium intercalation compounds, such as lithium cobalt oxide (LiCo02), lithium phosphate (LiFePO4), lithium nickel oxide (LINiO2) and lithium manganese oxide (LiMn204). The negative electrode is generally made of copper foil as the matrix, and the two sides of the copper foil are coated with negative electrode materials, including a certain ratio of negative electrode active materials (such as graphite, etc.) and binders (such as styrene-butadiene rubber (SBR), etc.). The positive and negative electrodes of the battery are made through processes such as mixing, coating, drying, and rolling of electrode materials. The electrolyte between the positive and negative electrodes in the battery usually uses an organic solution containing lithium compounds (such as lithium hexafluorophosphate (LiPF6), etc.). The positive electrode mostly uses PVDF as a binder, which has high viscosity and adhesion in N-methylpyrrolidone (NMP) solvent. The amount of organic agent used in the binder is large and the bonding method is relatively strong, making it difficult to recycle. The negative electrode uses a water-soluble binder such as butadiene rubber (SBR), which greatly reduces the difficulty of recycling.
Main chemical properties and potential environmental pollution of commonly used materials in waste lithium-ion batteries
Category Common materials Main chemical properties Potential environmental pollution
Cathode materials LiCoO2/LiMn2O4/LiNiO2 React strongly with water, acid, reducing agent and strong oxidant (hydrogen peroxide, chlorate, etc.) to produce harmful metal oxides Heavy metal cobalt pollution changes the environmental pH
Cathode materials Carbon materials/graphite Dust can explode when exposed to open flames or high temperatures Dust pollution
Electrolyte LiPF6/LiBF4/LiAsF6 is highly corrosive, can produce HF when exposed to water, and oxidizes to produce toxic substances such as P2O5 Fluorine pollution changes the environmental pH
Electrolyte solvents Ethylene carbonate/Propylene carbonate/Dimethyl carbonate Hydrolysis products produce aldehydes and acids, combustion can produce CO/CO2, etc. Organic pollution
Diaphragm pp/pe Combustion can produce CO, aldehydes, etc. Organic pollution
Adhesives PVDF, VDF, EPD It can react with fluorine, fuming sulfuric acid, strong alkali, and alkali metals, and decompose under heat to produce HF. Fluorine pollution
Waste lithium-ion batteries also have high resource recovery value. As shown in the figure below, they contain a large amount of valuable metals, with cobalt accounting for about
15%, and the potential value accounting for 82.40% of the entire battery. The content of copper and aluminum metals can reach 18.7%, and the potential value accounts for about 17.50% of the entire battery. In addition, the lithium element in waste lithium-ion batteries is a common alkali metal, which is also widely used and in great demand.
