Can LiMnO2 Battery Be Charged?

As a manufacturer of LiMnO₂ batteries, we will provide an overview of LiMnO₂ batteries and discuss their charging capabilities.

What is a Li-MnO2 Battery?

A Li-Mn battery generally refers to a lithium dioxide manganese battery. It is a type of battery in which lithium is used as the negative electrode and manganese dioxide is used as the positive electrode. The low and medium rate discharge performance of the lithium dioxide manganese battery is good, the price is cheap, and the safety performance is good. It is competitive with conventional batteries, and therefore was the first type of lithium battery to be commercialized.

LiMnO₂ batteries utilize manganese dioxide treated through a special process as the positive electrode material, while high-energy lithium metal serves as the negative electrode material. The electrolyte used is an organic solution known for its excellent conductivity. LiMnO₂ batteries are available in two structural forms: fully sealed and semi-sealed.

There are two types of LiMnO2 Battery: rechargeable and non-rechargeable. The rechargeable LiMnO2 Battery is also called lithium manganese oxide battery. In addition, rechargeable LiMnO2 Battery also has nickel-cobalt-manganese ternary batteries. The nominal voltage of the non-rechargeable manganese dioxide battery is 3.0V, the annual self-discharge is less than 2%, and it can be stored for 10 years at room temperature.

Manufacturing Process of Li-Mn Batteries

Using a fully sealed cylindrical winding Li-Mn battery as an example, here is a detailed overview of the basic manufacturing process and flow:

1. Preparation of the Manganese Dioxide Positive Electrode

- Mixing: Combine heat-treated electrolytic manganese dioxide powder with acetylene black, polytetrafluoroethylene emulsion, and isopropyl alcohol in precise proportions to create a paste.

- Coating and Heat Treatment: Coat the paste evenly onto a metal collector grid, then heat-treat and roll it to form the electrode. Alternatively, the paste can be applied to both sides of the metal collector using a rolling machine to produce the electrode. The finished electrode should be stored in a humidity-controlled environment with less than 2% relative humidity.

2. Preparation of the Lithium Metal Negative Electrode

- Cutting and Welding: Select lithium strips of the appropriate thickness and width, cut them to the required length, and cold weld electrode tabs onto the strips. This process must also occur in a controlled environment with less than 2% relative humidity.

3. Preparation of the Separator

- Processing: Use dry polypropylene separators of the required thickness and width, ensuring they are stored in an environment with less than 2% relative humidity. Typically, a composite separator that can seal at 130-160°C is chosen.

4. Assembly of the Li-Mn Battery Core

- Wrapping and Winding: Wrap two layers of separators, slightly wider than the electrodes, around the manganese dioxide positive electrode to isolate it from the lithium negative electrode. Wind this assembly into a core using a winder and place it into the battery case. The winding structure of the Li-Mn battery core is shown in the diagram.

5. Preparation of the Electrolyte Solution

- Mixing: The electrolyte solution's formulation varies by supplier. Generally, it involves mixing dehydrated lithium perchlorate with purified propylene carbonate, ethylene glycol dimethyl ether, and other components in specific proportions. This mixing should be conducted in a dry air environment with less than 2% relative humidity.

6. Injection and Sealing of the Electrolyte Solution

- Assembly and Injection: Weld the upper cover, equipped with glass insulators, to the battery shell containing the electrode core. Inject the specified amount of electrolyte solution into the battery through an injection hole using an injection machine. Seal the hole with a steel ball by welding.

This process ensures the efficient production of Li-Mn batteries with high performance and reliability.

Reasons Why LiMnO₂ Batteries Should Not Be Charged:

1. Charging Characteristics of LiMnO₂ Batteries

Charging a disposable LiMnO₂ battery can lead to a reverse reaction of the discharge process, regenerating lithium (Li) and manganese dioxide (MnO₂) inside the battery. As charging progresses, the battery voltage will gradually increase, potentially reaching up to 3.5V. After a period of standing, the open circuit voltage can stabilize back to the normal 3.2V (with a load, the rated voltage is 3V).

However, the microstructure of the MnO₂ and Li created during this process is not identical to the original materials, resulting in significantly reduced activity. Consequently, the capacity of the battery upon discharge is considerably lower compared to a new battery.

2. Dangers of Charging LiMnO₂ Batteries

LiMnO₂ batteries are typically labeled with "charging prohibited" to indicate that they are not designed for recharging. The reasons include:

- Flammable Organic Solvents: LiMnO₂ batteries are produced with low-boiling organic solvents, such as ethylene glycol dimethyl ether, which has a low flash point. If the battery expands due to heat or is not properly sealed during charging, the solvent can vaporize. This poses a risk of combustion or explosion if the vapors come into contact with sparks or flames.

- Risk of Combustion and Explosion: During charging, internal reactions can generate lithium, which is highly reactive. This increases the risk of dangerous incidents, such as combustion or explosion, making it crucial not to charge these batteries.