Lithium-ion Battery Structure: Button vs Prismatic vs Cylindrical Type​

Lithium-ion Battery Structure & Shape Types: A Complete Guide

Understanding the structure and different shape types of lithium-ion batteries is essential for choosing the right battery for your application. In this guide, we’ll cover the core components of lithium-ion batteries and the three most common shape categories.

### Core Structure of a Lithium-ion Battery

A standard lithium-ion battery consists of 5 key components:

1.  **Positive Electrode**: Made of a porous current collector (usually aluminum foil) coated with active material powder, conductive agents, and binders. The porous structure increases the effective reaction area and reduces electrochemical polarization.

2.  **Negative Electrode**: Made of a porous current collector (usually copper foil) coated with active material (typically graphite), conductive agents, and binders.

3.  **Separator**: A porous membrane that separates the positive and negative electrodes to prevent short circuits, while allowing Li⁺ ions to pass through.

4.  **Electrolyte**: A conductive medium that enables the movement of Li⁺ ions between the two electrodes.

5.  **Case**: The outer shell that protects the internal components, available in different materials (steel, aluminum, soft packaging) depending on the battery type.

### Classification by Shape

Lithium-ion batteries are commonly categorized by their external form into three main types:

#### 1. Button (Coin) Cells

Button cells are small, coin-shaped batteries. Their structure includes positive/negative plates, a separator, a stainless steel case, a cover, and a seal ring. The case and cover act as the positive and negative terminals. They are widely used in small devices like watches, hearing aids, and IoT sensors.

#### 2. Prismatic Batteries

Prismatic batteries have a rectangular shape. Their positive and negative electrodes use double-sided coated current collectors, assembled via stacking or winding processes, and sealed in aluminum, stainless steel, or aluminum-plastic composite film (soft pack) cases.

- **Model Naming**: Prismatic battery models are usually expressed as `Thickness + Width + Length`, e.g., model `485098` means 48mm thickness, 50mm width, 98mm length.

- **Applications**: Smartphones, laptops, electric vehicles, and energy storage systems.

#### 3. Cylindrical Batteries

Cylindrical batteries have a round shape. Their positive and negative electrodes are wound into a cylindrical core and sealed in a cylindrical metal case.

- **Model Naming**: Cylindrical battery models are usually expressed as `Diameter + Length + 0`, e.g., model `18650` means 18mm diameter, 65mm length, 0 indicates a cylindrical battery.

- **Applications**: Power tools, electric vehicles, home energy storage, and solar systems.

### Which Shape is Right for You?

- **Button cells**: For small, low-power devices.

- **Prismatic cells**: For high-energy-density applications like EVs and consumer electronics.

- **Cylindrical cells**: For high-power applications and large-scale energy storage.