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Views: 0 Author: Site Editor Publish Time: 2026-05-15 Origin: Site
LR20 alkaline battery, commonly known as Size D or No.1 dry battery, is a widely used primary battery with stable performance, high capacity and reliable discharge. Its excellent electrical performance is closely related to its unique internal structure and chemical reaction principle. This article will comprehensively explain the internal structure, working mechanism and key electrical performance parameters of LR20 alkaline batteries, helping readers deeply understand the core characteristics of this type of battery.
The LR20 alkaline battery adopts a cylindrical structure, which is composed of six core components: positive electrode, negative electrode, electrolyte, separator, sealant and outer casing. Each component undertakes a unique function, and the coordination between them ensures the stable operation of the battery.
The positive electrode of LR20 alkaline battery is the core component that generates current. It is mainly made of manganese dioxide (MnO₂) as the active material, mixed with a small amount of conductive agent (such as acetylene black) and binder. The mixture is pressed into a cylindrical hollow structure, which is closely attached to the inner wall of the outer casing, maximizing the contact area with the electrolyte and improving the conductive efficiency.
Manganese dioxide acts as an oxidizing agent in the chemical reaction, accepting electrons released by the negative electrode during discharge, which is the key to the battery's ability to output current stably.
The negative electrode is located in the center of the battery, in the form of a zinc cylinder (or zinc powder pressed into a cylinder), which is the reducing agent in the chemical reaction. The zinc cylinder is wrapped around the current collector (usually a copper nail), which is used to guide the current generated by the reaction to the battery terminal, ensuring efficient current output.
Compared with carbon-zinc batteries, the zinc used in LR20 alkaline batteries has higher purity and better reactivity, which can effectively improve the battery's capacity and discharge performance.
The electrolyte of LR20 alkaline battery is an alkaline solution, usually a concentrated aqueous solution of potassium hydroxide (KOH) with a concentration of 30%-40%. It acts as a medium for ion transmission, enabling the migration of ions between the positive and negative electrodes, thereby completing the closed loop of the chemical reaction.
The alkaline electrolyte has high conductivity and stable chemical properties, which can effectively reduce the internal resistance of the battery and improve the high-current discharge capacity. At the same time, it can slow down the corrosion of the negative electrode zinc, extending the battery's service life.
The separator is a porous insulating material (usually non-woven fabric or porous plastic) placed between the positive and negative electrodes. Its main functions are: isolating the positive and negative electrodes to prevent short circuits caused by direct contact; allowing ions in the electrolyte to pass through freely, ensuring the smooth progress of the chemical reaction; and preventing the mixing of active materials between the two electrodes, avoiding the attenuation of battery performance.
The sealant is made of high-temperature resistant and corrosion-resistant materials (such as asphalt or epoxy resin), which is used to seal the top and bottom of the battery to prevent the leakage of electrolyte and the entry of air, ensuring the safety and stability of the battery during storage and use.
The outer casing is usually made of nickel-plated steel sheet, which has good mechanical strength and corrosion resistance. It not only protects the internal components from external impact and damage, but also serves as a positive current collector, guiding the current from the positive electrode to the positive terminal of the battery.
LR20 alkaline battery is a primary battery that converts chemical energy into electrical energy through irreversible redox reactions. The working process is essentially the process of electron transfer between the positive and negative electrodes through the electrolyte, and the specific reaction mechanism is as follows:
When the battery is connected to an external circuit, the negative electrode zinc (Zn) loses electrons and is oxidized into zincate ions (ZnO₂²⁻), which enter the electrolyte. The electrons released by the negative electrode flow to the positive electrode through the external circuit, forming a current. At the positive electrode, manganese dioxide (MnO₂) accepts electrons and is reduced to manganese trioxide (Mn₂O₃), and combines with hydroxide ions (OH⁻) in the electrolyte to complete the reaction.
The chemical reactions are as follows:
Negative electrode reaction: Zn + 4OH⁻ - 2e⁻ → ZnO₂²⁻ + 2H₂O
Positive electrode reaction: 2MnO₂ + H₂O + 2e⁻ → Mn₂O₃ + 2OH⁻
Overall reaction: Zn + 2MnO₂ + H₂O → ZnO₂²⁻ + Mn₂O₃ + 2OH⁻
The redox reaction of LR20 alkaline battery is stable and efficient. During the discharge process, the concentration of the electrolyte changes slowly, and the voltage remains relatively stable. Compared with carbon-zinc batteries, the reaction rate of alkaline batteries is faster, which can provide stable high-current output. In addition, the reaction process does not produce gas, which avoids the expansion and leakage of the battery, improving the safety and service life.
It should be noted that the reaction of LR20 alkaline battery is irreversible. Once the active materials (zinc and manganese dioxide) are consumed, the battery cannot be recharged and can only be discarded, which is the essential difference between primary batteries and secondary batteries (rechargeable batteries).
The electrical performance parameters of LR20 alkaline battery determine its application scope and use effect. The following are the core parameters, their definitions and typical values, helping readers accurately understand the performance of the battery.
Nominal voltage refers to the standard voltage value marked on the battery, which is the average voltage output during the normal discharge process of the battery. The nominal voltage of LR20 alkaline battery is 1.5V, which is consistent with most dry batteries (such as AA, AAA batteries), ensuring good compatibility with various household and industrial devices.
During actual discharge, the initial voltage of the battery is slightly higher than 1.5V (about 1.55-1.6V), and then gradually decreases to about 0.8V as the reaction proceeds. When the voltage drops below 0.8V, the battery is basically exhausted and cannot meet the power demand of the device.
Capacity refers to the total amount of electrical energy that the battery can release under specified discharge conditions, usually expressed in milliampere-hours (mAh) or ampere-hours (Ah). The capacity of LR20 alkaline battery is affected by discharge current, temperature and other factors, and its typical capacity is as follows:
Under low-current discharge (≤100mA): The capacity can reach 10000-12000mAh, suitable for low-power devices such as remote controls and small toys.
Under medium-current discharge (100-500mA): The capacity is about 8000-10000mAh, suitable for devices such as flashlights and doorbells.
Under high-current discharge (≥500mA): The capacity is about 5000-7000mAh, suitable for high-power devices such as gas stoves and water heaters.
Compared with carbon-zinc D-size batteries (capacity 3000-5000mAh), LR20 alkaline batteries have a much higher capacity, which is the key reason for their longer service life.
Internal resistance refers to the resistance of the battery itself, including the resistance of the electrode, electrolyte, separator and contact resistance between components. The internal resistance of LR20 alkaline battery is very low, typically 8-15mΩ (at 25℃).
Low internal resistance enables the battery to output high current stably, reduce energy loss during discharge, and avoid excessive temperature rise of the battery. This is particularly important for high-power devices that require instant high-current ignition (such as gas stoves).
The discharge characteristic of LR20 alkaline battery is mainly reflected in its discharge curve, which is the relationship between voltage and discharge capacity. The key characteristics are:
Flat discharge curve: During the main discharge period (accounting for 80% of the total capacity), the voltage remains stable at 1.2-1.4V, ensuring the stable operation of the device.
Good high-current discharge performance: It can stably discharge under high current (≥1A) without obvious voltage drop, and the discharge efficiency is higher than 85%.
Temperature adaptability: The discharge capacity is basically stable in the temperature range of -10℃ to 40℃. At -10℃, the discharge capacity can still reach 70% of the room temperature capacity, which is suitable for various indoor and outdoor environments.
Self-discharge rate refers to the rate at which the battery loses power spontaneously when not in use, usually expressed as a percentage per year. The self-discharge rate of LR20 alkaline battery is very low, ≤3% per year under room temperature (25℃, dry environment).
This means that the battery can be stored for 3-5 years while maintaining more than 80% of its capacity, which is very suitable for standby power supply of devices that are not used frequently (such as emergency lighting and backup power).
Service life refers to the time that the battery can maintain normal power output under specified use conditions. For LR20 alkaline battery, the service life varies according to the discharge current: under low-current use, it can be used for 1-2 years; under high-current use (such as gas stove ignition), it can be used for 6-12 months.
Storage life refers to the maximum time that the battery can maintain its performance under proper storage conditions (25℃, dry, away from direct sunlight). The storage life of LR20 alkaline battery is 5-7 years, which is much longer than that of carbon-zinc batteries (1-2 years).
Safety is an important indicator of LR20 alkaline battery. The key safety parameters are:
Leakage rate: ≤0.1% under normal storage and use conditions, ensuring no electrolyte leakage.
Short-circuit current: ≤5A, avoiding overheating or explosion caused by short circuit.
Operating temperature range: -20℃ to 60℃, no deformation, leakage or explosion within this range.
The excellent electrical performance of LR20 alkaline battery is rooted in its reasonable internal structure and efficient alkaline redox reaction. Its cylindrical structure, with positive electrode, negative electrode, electrolyte and separator closely matched, ensures stable current output and low internal resistance. The key electrical parameters such as 1.5V nominal voltage, high capacity, low self-discharge rate and good high-current discharge performance make it the preferred power source for high-power household and industrial devices.
Understanding the structure principle and electrical performance parameters of LR20 alkaline battery can help users better select and use the battery, maximize its service life, and ensure the stable operation of the powered devices.
