Assembly of button batteries

1.About

Button cells, also known as coin cells or battery cells, are compactly designed batteries shaped like small buttons. They are widely used in various small electronic devices, such as car keys, TWS wireless earbuds, watches, calculators, hearing aids, and some medical devices and precision electronic instruments. Their characteristics include a small size and light weight, making them ideal for applications where space is limited.

Classification and Naming

Button cells are mainly divided into two categories: chemical cells and physical cells, with chemical cells being the most common. A chemical cell consists of a positive electrode, a negative electrode, and an electrolyte. The outer casing is typically made of stainless steel, which serves as both the positive electrode and the protective shell, while the negative electrode is located at the top of the battery. An insulating seal ring is placed between the electrodes to prevent electrolyte leakage. Depending on the materials used, button cells can be silver oxide batteries, lithium manganese batteries, alkaline manganese batteries, and so on.

In terms of model naming, the model numbers of button cells usually reflect their type, size, and voltage. For example, LR stands for alkaline battery, SR represents silver oxide battery, CR denotes a 3V lithium manganese battery, and LIR indicates a rechargeable lithium-ion battery. The numbers in the model indicate the size of the battery, such as CR2032, which means a diameter of 20mm and a thickness of 3.2mm.

2.Items Preparation

Inside the glove box: tablet press (preferably with digital display), 2 tweezers (at least one is plastic), 1 medicine spoon, electrolyte, lithium sheet, pipette gun, battery shell, paper towel dried in the oven;

Outside the glove box: spring sheet (or nickel foam), pole piece, diaphragm;

 

Note: Before putting the battery assembly parts into the glove box, they should be vacuum dried. The temperature should not be too high and can be set at 60-80℃. A glove box with a larger capacity can store these battery parts in advance, which is cleaner. After the raw materials enter the hatch, strictly follow the operating procedures to perform exhaust-intake operations at least three times. It is recommended to place a small operating table in the glove box to prevent the reagents from corroding the glove box. The electrolyte corrodes the gloves and the inner wall of the glove box seriously, and operational errors should be avoided as much as possible.

 

3.Determine the water content

Generally, glove boxes have digital display devices for water and oxygen content. The battery assembly process is carried out in a glove box that has been strictly exhaust-intake operated to strictly isolate any possible interference such as oxidation and moisture. If the water and oxygen content in the glove box is always high, you should check whether the gloves are damaged or regenerate the glove box.

 

4.Assembly Process

There are two main assembly orders for button batteries. I usually start from the positive shell, but you can also start from the negative shell. There is no right or wrong, it all depends on personal habit.

 

Positive electrode shell-pole sheet-electrolyte-diaphragm-electrolyte-lithium sheet-gasket-negative electrode shell

 

 

5.Frequently asked questions

After the battery is assembled, some problems may occur during testing. The following are possible problems and their causes:

 

Why is the open circuit voltage too low?

(1) The burrs on the electrode pierce the diaphragm, causing a short circuit in the battery;

(2) During the battery assembly process, the positive and negative electrodes shifted and contacted the side wall of the electrode shell, causing a short circuit;

(3) The battery pressing step is wrong, resulting in loose battery assembly, loose connection between the positive and negative battery shells and the positive and negative electrode sheets, causing a short circuit (the pressure should be controlled at around 50Mpa).

What is the reason for the large electrochemical impedance?

(1) Insufficient amount of conductive agent added;

(2) The porosity of the diaphragm is small, so that lithium ions in the electrolyte cannot pass smoothly;

(3) The electrolyte decomposes and the lithium salt in it decreases.

(4) The material is too humid and has not been dried in advance.

6.Canrd Brief Introduce

Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D. We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.

 

Email： contact@canrd.com    Phone/Wechat/WhatsApp： +86 19867737979

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