The electrolyte in an industrial button battery, as the core medium for ion transport, directly affects the battery's energy density, cycle life, safety performance, and environmental adaptability. Electrolytes typically consist of three parts: solvent, lithium salt, and additives. These components work synergistically to optimize the battery's overall performance.
The solvent is the basic carrier of the electrolyte and must possess characteristics such as high chemical stability, a wide liquid temperature range, and low viscosity. Carbonate solvents commonly used in industrial button batteries (such as ethylene carbonate and dimethyl carbonate) are mixed in a specific ratio to provide sufficient dielectric constant to dissolve the lithium salt while maintaining low viscosity to promote lithium-ion migration. This solvent system must be highly compatible with the electrode materials to avoid reduction decomposition on the negative electrode surface or oxidation reactions with the positive electrode material. For example, in lithium-manganese button batteries, the solvent must withstand the oxidizing environment of the high-voltage positive electrode while forming a stable solid electrolyte interphase (SEI) film at the negative electrode to prevent continuous electrolyte consumption.
The lithium salt, as the ion source, directly determines the ionic conductivity and electrochemical stability of the electrolyte. Lithium hexafluorophosphate (LiPF₆) has become the mainstream lithium salt for industrial button batteries due to its high solubility, high ion transport number, and excellent oxidation stability. In the solvent, lithium ions and anions (such as PF₆⁻) dissociated from this lithium salt achieve charge transport through directional migration. The concentration of this lithium salt needs to be precisely controlled to balance ionic conductivity and electrolyte viscosity. If the lithium salt concentration is too high, the increased electrolyte viscosity will hinder lithium ion transport; if the concentration is too low, insufficient ion quantity will lead to increased internal resistance. Furthermore, the decomposition products of the lithium salt need to form a dense SEI film on the negative electrode surface. This film must be electronically insulating but allow lithium ions to pass freely, thereby preventing side reactions caused by direct contact between the electrolyte and the electrode.
Additives significantly improve electrolyte performance through micro-control, with effects encompassing film formation optimization, safety enhancement, and lifespan extension. Negative electrode film-forming additives (such as vinylene carbonate and fluoroethylene carbonate) preferentially decompose on the negative electrode surface to form a dense SEI film, reducing capacity decay caused by solvent molecule co-intercalation. Positive electrode protection additives (such as nitrile compounds) form a passivation layer by coordinating with metal ions on the positive electrode surface to inhibit electrolyte oxidation and decomposition, as well as the dissolution of transition metal ions. Overcharge protection additives, through redox shuttle mechanisms or electropolymerization reactions, block current when the voltage exceeds a safe threshold, preventing battery thermal runaway. For example, in lithium manganese button batteries, adding a specific proportion of overcharge protection additives can automatically terminate the charging process under overcharge conditions, significantly improving safety.
The electrolyte composition has a decisive impact on the operating temperature range of an industrial button battery. At low temperatures, increased electrolyte viscosity leads to a decrease in lithium-ion migration rate and an increase in battery internal resistance; at high temperatures, side reactions between the electrolyte and electrode materials intensify, reducing SEI film stability. By optimizing the solvent ratio (e.g., introducing low-viscosity solvents) or adding low-temperature conductive additives, the electrolyte's liquid temperature range can be widened, allowing the battery to operate stably in extreme environments ranging from -40°C to +85°C. For example, some industrial-grade button batteries, by adjusting the electrolyte composition, achieve normal charge and discharge at temperatures as low as -50°C, meeting the needs of special applications such as aerospace.
The electrolyte composition also directly affects the cycle life of an industrial button battery. A stable SEI film reduces continuous electrolyte consumption during charge and discharge, while the inhibitory effect of additives on side reactions slows down battery capacity decay. For example, in silicon-based negative electrode button batteries, the stability of the SEI film is significantly improved by adding film-forming additives, and the battery can still maintain a capacity retention rate of over 80% after hundreds of cycles. Furthermore, optimizing the compatibility of the electrolyte with electrode materials (such as suppressing the structural collapse of the positive electrode material) is also a key factor in extending cycle life.
Safety is one of the core indicators of an industrial button battery, and the electrolyte composition ensures battery safety through multiple mechanisms. Flame-retardant additives (such as phosphate esters) can inhibit electrolyte combustion, overcharge prevention additives can prevent battery thermal runaway, and high-purity lithium salts can reduce the formation of corrosive substances such as HF. For example, some industrial button batteries, by using high-purity lithium hexafluorophosphate and adding flame-retardant components, prevent explosions or fires under abuse conditions such as puncture and crushing, meeting stringent safety standards.
From an environmental adaptability perspective, electrolyte composition must balance performance and environmental requirements. The application of mercury-free, lead-free, and other environmentally friendly lithium salts, as well as biodegradable solvents, allows industrial button batteries to meet high-performance requirements while reducing potential harm to the ecological environment. For instance, aqueous electrolyte button batteries, by using inorganic lithium salts and aqueous solvents, achieve zero organic solvent emissions and are widely used in fields with extremely high environmental requirements, such as medical equipment.
