Lithium-ion batteries power the lives of millions of people each day. From laptops and cell phones to hybrids and electric cars, this technology is growing in popularity due to its light weight, high energy density, and ability to recharge.
So how does it work?
THE BASICS
A battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative). The anode and cathode store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.
CHARGE/DISCHARGE
While the battery is discharging and providing an electric current, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When plugging in the device, the opposite happens: Lithium ions are released by the cathode and received by the anode.
ENERGY DENSITY VS. POWER DENSITY
The two most common concepts associated with batteries are energy density and power density. Energy density is measured in watt-hours per kilogram (Wh/kg) and is the amount of energy the battery can store with respect to its mass. Power density is measured in watts per kilogram (W/kg) and is the amount of power that can be generated by the battery with respect to its mass. To draw a clearer picture, think of draining a pool. Energy density is similar to the size of the pool, while power density is comparable to draining the pool as quickly as possible.
Advantages of Lithium-ion Battery
Now a days Lithium-ion batteries are popular because they have a number of important advantages over competing technologies:
- Generally, they are much lighter than other types of rechargeable batteries of the same size. They hold their charge.
- They hold their charge. A lithium-ion battery pack loses only about 5 percent of its charge per month.
- High specific energy and high load capabilities with Power Cells.
- Long cycle and extend shelf-life; maintenance-free. They can handle hundreds of charge/discharge cycles.
- High capacity, low internal resistance, good coulombic efficiency.
- Simple charge algorithm and reasonably short charge times.
- Low self-discharge (less than half that of NiCd and NiMH).
Limitations of Lithium-ion Battery
- Requires protection circuit to prevent thermal runaway if stressed
- Degrades at high temperature and when stored at high voltage
- No rapid charge possible at freezing temperatures (<0°C, <32°F).
- Transportation regulations required when shipping in larger quantities.
- They are extremely sensitive to high temperatures. Heat causes lithium-ion battery packs to degrade much faster than they normally would..