Primary Lithium Batteries

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1. Basic Definition

Primary lithium batteries, also referred to as lithium primary cells, are a key branch of lithium batteries. Together with rechargeable secondary lithium batteries, they form the lithium battery system. Their core feature is the use of metallic lithium or lithium alloys as the negative electrode, combined with solid active materials such as manganese dioxide and thionyl chloride as the positive electrode, and the realization of electrochemical reactions relying on non-aqueous electrolyte solutions. After discharge, the chemical system cannot reverse the response through an external current, so it can only be used once. After the power is exhausted, it needs to be discarded or recycled, and cannot be recharged cyclically like secondary lithium batteries. Primary lithium batteries are mostly in small packages, such as button-type and small cylindrical types. Their casings are mainly made of metal materials, with a simple structure and non-detachable.

The key difference between the two major branches of lithium batteries lies in that: primary lithium batteries generate electrical energy through the dissolution and deposition of metallic lithium, such as CR2032 button batteries and 3V special-purpose batteries for cameras; secondary lithium batteries, represented by lithium-ion batteries, realize charge-discharge cycles through the intercalation and deintercalation of lithium ions between the positive and negative electrodes, and are widely used in consumer electronics and new energy vehicle fields.

(1) Core Composition

Each battery cell consists of five key components, each with a distinct and indispensable function:

• Positive and Negative Electrodes: These act as storage spaces for lithium ions. Common materials used for the positive electrode include lithium cobalt oxide, nickel-cobalt-manganese, and lithium iron phosphate, while graphite is widely adopted for the negative electrode.

• Electrolyte: It functions as a “channel” for the movement of lithium ions between the positive and negative electrodes, ensuring the smooth progress of electrochemical reactions.

• Separator: It has both “isolation” and “conduction” functions. It can prevent direct contact between the positive and negative electrodes, which would otherwise cause a short circuit, and at the same time, allow lithium ions to pass through.

• Shell: It provides physical protection and sealing for the internal components. The shell materials of different types of battery cells vary greatly. For example, cylindrical batteries use metal shells, and pouch batteries use aluminum-plastic films.

2. Core Characteristics

• Non-rechargeability: The chemical reaction after discharge is irreversible, and it cannot be reused through charging. This is the most essential difference from secondary lithium batteries.

• High energy density: Due to the active chemical properties of lithium, it can store more energy per unit volume or weight. The specific energy can be as high as 650Wh/kg, which is much higher than that of traditional alkaline batteries (about 150Wh/kg) and lead-acid batteries (about 40Wh/kg).

• Long service life and low self-discharge: The annual self-discharge rate is usually only 1%-2%. Some types, such as lithium-thionyl chloride batteries, can be stored for a long time at a room temperature of 20°C, with an overall storage life of 10-20 years, making them suitable for long-term backup scenarios.

• Stable and high voltage: The open-circuit voltage is mostly between 3.0-3.6V. For example, lithium-manganese dioxide batteries have a nominal voltage of 3V, and lithium-thionyl chloride batteries have a nominal voltage of 3.6V, which is much higher than the 1.5V of traditional alkaline batteries. Moreover, the voltage output is stable during the discharge process.

• Wide operating temperature range: Conventional models can work in an environment of -40°C to +85°C. Some special models, after design, can withstand a low temperature of -60°C and a high temperature of 150°C, and can adapt to extreme environments.

• High safety (attention required for some systems): Most systems have passed safety certifications such as UN38.3 and UL1642, with a reliable structure. However, systems such as lithium-thionyl chloride batteries may have potential safety hazards at high temperatures.

3. Common Chemical Systems and Performance Parameters

Chemical System	Cathode Material	Anode Material	Chemical Reaction Formula	Nominal Voltage (V)	Cut-off Voltage (V)	Specific Energy (Wh/kg)	Core Features	Typical Applications
Lithium-Manganese Dioxide Battery (Li-MnO₂)	Manganese Dioxide (MnO₂)	Metallic Lithium (Li)	Li + MnO₂ → LiMnO₂	3.0	2.0	280-300	Low cost, good safety, medium capacity	Watches, calculators, medical devices, computer motherboard CMOS
Lithium-Thionyl Chloride Battery (Li-SOCl₂)	Thionyl Chloride (SOCl₂)	Metallic Lithium (Li)	4Li + 2SOCl₂ → 4LiCl + S + SO₂	3.6	3.3	420-650	Highest energy density, obvious passivation effect, potential safety hazards at high temperatures	Smart electricity meters, water meters, gas meters, military equipment
Lithium-Carbon Fluoride Battery (Li-CFₓ)	Carbon Fluoride (CFₓ)	Metallic Lithium (Li)	Li + CFₓ → LiF + xC	3.0	–	450-500	Stable discharge, high energy density, excellent stability	Implantable medical devices such as pacemakers, aerospace equipment
Lithium-Sulfur Dioxide Battery (Li-SO₂)	Sulfur Dioxide (SO₂)	Metallic Lithium (Li)	–	2.8	–	260-320	Good power performance, excellent low-temperature adaptability, requires pressure design	Military radios, cardiac defibrillators
Lithium-Iodine Battery (Li-I₂)	Iodine-Polypyrrole	Metallic Lithium (Li)	–	2.8	–	200-250	Solid electrolyte, extremely high safety, storage life over 20 years	Pacemakers, backup power for memory
Lithium-Iron Disulfide Battery (Li-FeS₂)	Iron Disulfide (FeS₂)	Metallic Lithium (Li)	–	1.5	–	300	Same voltage as alkaline batteries, good low-temperature performance, anti-leakage, 15-year shelf life	Digital cameras, portable players (replacing AA/AAA alkaline batteries)

4. Advantages and Disadvantages

(1) Advantages

• Convenient use: No maintenance is required; it can be used immediately after installation. There is no need to be equipped with a charger or a battery management system, which reduces the complexity of the equipment.

• Lightweight design: With high energy density, under the same power supply demand, its volume and weight are much smaller than those of traditional batteries, making it suitable for portable devices and small instruments.

• Stable discharge performance: No memory effect, and the discharge curve is gentle. It can provide continuous and stable voltage for the equipment, avoiding the impact of voltage fluctuations on the operation of the equipment.

• Strong environmental adaptability: The wide operating temperature range enables it to work normally in extreme environments such as cold and high temperatures, and it is suitable for special scenarios such as industry, military, and aerospace.

(2) Disadvantages

• High cost: Especially for special models (such as lithium-carbon fluoride batteries and lithium-iodine batteries), the materials and manufacturing processes are complex, and the unit price is much higher than that of ordinary alkaline batteries and conventional lithium-ion batteries.

• Safety risks (for some systems): Systems such as lithium-thionyl chloride batteries may experience increased internal pressure and explosion at high temperatures. Some batteries may leak after long-term use, damaging the equipment.

• Environmental protection and recycling challenges: They contain harmful substances such as metallic lithium. If they are not properly disposed of after being discarded, they will pollute the environment. Moreover, the recycling process is complex, and the current recycling rate is low.

• Limited application scenarios: They are only suitable for low-power equipment and cannot meet the needs of scenarios that require high power and frequent discharge, such as electric vehicles and power tools.

5. Classic Application Scenarios

• Consumer electronics field: Watches, calculators, electronic keys, remote controls, digital cameras, etc., mostly use lithium-manganese dioxide batteries (such as CR2032 button batteries and CR123A). Taking advantage of their small size and long service life, the frequency of replacement is reduced; the CMOS power supply of computer motherboards relies on button-type lithium primary batteries to ensure that data is not lost after a power failure.

• Industrial and infrastructure field: Smart electricity meters, water meters, gas meters, etc., use lithium-thionyl chloride batteries (such as ER14250 and ER18505). The service life of more than 10 years can reduce the number of instrument maintenance; remote environmental sensors and pipeline monitoring equipment use their low self-discharge and wide temperature characteristics to conduct long-term stable monitoring in harsh outdoor environments.

• Medical equipment field: Pacemakers, implantable blood glucose monitors, etc., use lithium-carbon fluoride batteries or lithium-iodine batteries. These batteries have high energy density, stable discharge, and extremely high safety, which are suitable for the human implantation environment, with a service life of 5-10 years; in vitro equipment such as electrocardiographs and infusion pumps rely on the stability of lithium primary batteries to ensure uninterrupted power supply during diagnosis and treatment.

• Military and aerospace field: Military radios, navigation equipment, mine fuzes, etc., use lithium-thionyl chloride batteries or lithium-sulfur dioxide batteries. The high energy density and wide temperature performance are suitable for the complex battlefield environment; satellite backup power supplies and spacecraft sensors use lithium-carbon fluoride batteries, which can work stably in the extreme temperature and vacuum environment of space.

• Automotive and Internet of Things (IoT) field: Tire Pressure Monitoring Systems (TPMS) and car keys use small lithium primary batteries. The small size and low power consumption characteristics meet the power supply needs of the equipment; IoT devices such as electronic price tags, smart door locks, and wireless sensor terminals use the long service life of lithium primary batteries to reduce maintenance costs and promote the large-scale application of IoT scenarios.

6. Selection Guide

• Matching voltage and power consumption: Select a battery with a corresponding nominal voltage according to the rated voltage of the equipment. For low-power equipment (such as meters and sensors), lithium-thionyl chloride batteries are preferred; for low-to-medium power civil equipment (such as watches and remote controls), lithium-manganese dioxide batteries are selected; if the equipment originally uses 1.5V alkaline batteries, it can be replaced with lithium-iron disulfide batteries to improve performance.

• Adapting to the use environment: For extreme low-temperature (such as -60°C) or high-temperature (such as 150°C) environments, lithium-thionyl chloride batteries and lithium-carbon fluoride batteries are preferred; for humid environments or human contact scenarios (such as medical implantable equipment), lithium-carbon fluoride batteries and lithium-iodine batteries with good sealing performance and no leakage risk should be selected.

• Evaluating the service life requirement: For equipment that requires long-term backup and is difficult to replace (such as smart meters and military equipment), select lithium-thionyl chloride batteries and lithium-carbon fluoride batteries with a storage life of more than 10 years; for civil equipment that is used for a short time and replaced frequently (such as remote controls), lithium-manganese dioxide batteries with lower cost can be selected.

• Referring to the adaptation scenarios of mainstream models: For water meters and gas meters, select ER14250; for AMI meters, select ER18505; for cameras and security equipment, select CR123A; for large industrial sensors, select ER26500C; for military low-temperature equipment, select TL-5930. You can quickly match through the “selection mnemonic”: “For water meters and gas meters, choose thionyl chloride; for cameras and toys, use manganese dioxide; for low-temperature military use, add sulfur dioxide; for in vivo implantation, lithium-iodine is cool; CFₓ has the highest energy, and it is only affordable for aerospace and deep space”.

7. Mainstream Commercial Models

Primary lithium batteries come in various sizes to adapt to different application scenarios. The sizes of mainstream commercial models are as follows:

ER14250: Cylindrical, with a diameter of 14.5mm, a height of 25.0mm, and a mass of 10g. It is the “standard core” size commonly used in civil meters such as water meters.

ER18505: Cylindrical, with a diameter of 18.5mm, a height of 50.5mm, and a mass of 28g. It is suitable for equipment that requires long-term power supply such as AMI meters.

CR123A: Cylindrical, with a diameter of 17.0mm, a height of 34.5mm, and a mass of 17g. It is commonly used in cameras and security equipment.

ER26500C: Cylindrical, with a diameter of 26.2mm, a height of 50.5mm, and a mass of 52g. It is a high-capacity model with a pin design, suitable for large industrial sensors.

TL-5930: Cylindrical, with a diameter of 26.0mm, a height of 50.0mm, and a mass of 70g. It is a military-grade model, suitable for equipment in extreme low-temperature environments.

In addition, there are button-type sizes (such as CR2032, commonly used in watches and computer motherboards) and rectangular sizes (for some special industrial meters), to meet the installation space requirements of different equipment.

8. Recycling and Environmental Requirements

(1) Current Recycling Methods

At present, the main treatment method for lithium primary batteries is “solidification and landfilling”, and the specific process is as follows:

• Pretreatment discharge: Discharge the waste batteries to 0V in a dry room to avoid electric shock or chemical reactions in the subsequent treatment and ensure the safety of the treatment.

• Passivation treatment: Soak the discharged batteries in a mixed solution of 5% isopropyl alcohol and 95% inert oil for 24 hours to slowly passivate the metallic lithium, preventing it from reacting with water or air to generate hydrogen and lithium hydroxide, and reducing safety risks.

• Disassembly and separation: Disassemble the batteries manually or mechanically, and separate components such as steel casings, lithium residues, and electrolytes to avoid secondary reactions caused by the mixing of different substances.

• Final disposal: Send the steel casings to smelters for recycling and reuse; treat the lithium residues and electrolytes through cement kiln co-processing to achieve the harmless treatment of harmful substances; some recyclable lithium salts are purified and used in other industrial productions to improve resource utilization.

(2) Environmental Regulations and Future Trends

The EU’s “Battery Regulation” (2023/1542) clearly requires that the lithium recovery rate of lithium primary batteries must reach more than 65% from 2025, promoting the industry’s transformation from traditional solidification and landfilling to efficient “hydrometallurgical” recovery technology. The hydrometallurgical technology dissolves the lithium element in the battery through a chemical solution, and further purifies it to prepare products such as lithium chloride and lithium carbonate, realizing the cyclic utilization of lithium resources, reducing the dependence on primary lithium resources, and reducing environmental pollution. It will become the mainstream technical direction for the recycling of lithium primary batteries in the future.