1. Specific uses of lithium in batteries
   (1) As an active material
   Lithium participates in the charge and discharge reactions of batteries in the form of lithium ions:
   During the charging process, lithium ions are deintercalated from the positive electrode, migrate through the electrolyte to the negative electrode and embed into it.
   During the discharge process, lithium ions are deintercalated from the negative electrode and return to the positive electrode, releasing the stored energy.
   This reversible migration mechanism of lithium ions constitutes the core working principle of lithium-ion batteries.
   (2) Improving energy density
   Lithium metal or lithium compounds (such as LiCoO₂, LiFePO₄) are widely used in positive and negative electrode materials, significantly improving the energy density of batteries and meeting the needs of portable devices and electric vehicles for high-performance power sources.
   (3) Optimizing cycle life
   By rationally designing the structural stability of lithium-based materials, lithium-ion batteries can achieve long cycle life and reduce capacity decay caused by charging and discharging.
2. Characteristics and advantages of lithium
   Lithium is a light alkali metal with the following unique properties:
   Low atomic weight: Lithium is the lightest metal in nature and can provide higher energy density per unit mass.
   High electrochemical activity: The standard electrode potential of lithium is -3.04V (relative to the standard hydrogen electrode), making it an ideal negative electrode material.

Excellent conductivity: Lithium ions can migrate quickly between electrode materials, ensuring efficient charge and discharge performance.

These characteristics make lithium an ideal choice for modern high-energy batteries.

3. Summary
   The use of lithium in batteries is mainly reflected in its participation in electrochemical reactions as an active substance, while greatly improving the energy density and performance of batteries with its low weight and high electrochemical activity. It is precisely because of the unique properties of lithium that lithium-ion batteries have become the mainstream technology in the field of contemporary energy storage.