lithium ion battery

A lithium ion battery is a rechargeable electrochemical cell that moves lithium ions between two terminals, called the anode and cathode, through an organic electrolyte. Unlike older alkaline batteries, these cells reverse their chemical reaction when charged, making them suitable for repeated use over hundreds or thousands of cycles. The anode is typically graphite, the cathode is a lithium metal oxide (such as lithium cobalt oxide or lithium iron phosphate), and the electrolyte is a lithium salt dissolved in organic solvents. This combination produces nominal voltages between 3.2 and 3.7 volts per cell, depending on chemistry.

Industrial and commercial use of lithium ion batteries spans electric vehicles, grid energy storage, uninterruptible power supplies, and portable tools. A single automotive battery pack may contain hundreds of individual cells connected in series and parallel to achieve the required voltage and capacity. The energy density of lithium ion cells is significantly higher than lead acid or nickel metal hydride batteries, meaning lighter weight for the same stored energy. This advantage made them the standard for electric vehicles, where weight directly affects range and performance.

Chemistry variants and trade-offs

Lithium cobalt oxide cells, common in consumer electronics, offer high energy density but are expensive and less thermally stable. Lithium iron phosphate cells, often used in industrial and stationary applications, are slower to charge and store less energy per kilogram, but tolerate deeper discharge and wider temperature ranges. Nickel manganese cobalt and nickel cobalt aluminum blends represent middle grounds, trading off cost, stability, lifespan, and performance. Each chemistry requires different charging protocols and thermal management strategies.

Failure modes in lithium ion batteries include thermal runaway (uncontrolled temperature rise that can cause fire), degradation of the solid electrolyte interface layer, dendrite growth that pierces the separator and causes internal short circuits, and swelling from gas generation. Manufacturing defects such as internal contaminants or damage to the separator can trigger these failures months or years after the battery leaves the factory. Proper thermal management, charge limiting, and monitoring of voltage and internal resistance are essential for safe operation in industrial settings.

The name reflects the chemistry rather than the physical form. Despite the name, these batteries contain no metallic lithium; the lithium exists as ions and lithium compounds bound in the electrode materials. This distinction matters because elemental lithium is pyrophoric and incompatible with water, whereas lithium ion cells are considerably safer and can be manufactured at industrial scale. The term gained common use in the 1990s as these cells entered consumer markets and displaced nickel cadmium and nickel metal hydride designs.