Why do lithium batteries need to undergo aging tests?

The lithium battery manufacturing process is complex and may involve hidden issues such as electrode burrs, micro-short circuits, insufficient electrolyte, and encapsulation leakage. These problems are difficult to detect initially; however, aging tests—simulating charge-discharge cycles—can quickly reveal defects. For example, batteries with micro-short circuits will overheat and experience a sharp capacity decline during cycling, enabling early rejection and preventing substandard products from reaching the market.

In new batteries, an unstable solid electrolyte interface (SEI) film forms at the electrode-electrolyte interface. During aging tests, the charge-discharge process promotes the development of a uniform, dense, and stable SEI film structure. This stabilization reduces unexplained capacity decay during subsequent use and ensures that battery parameters, such as capacity and voltage, remain within acceptable ranges, thereby guaranteeing product consistency.

By simulating real-world usage scenarios—such as varying temperatures and charge-discharge rates—during aging cycles, the rate of battery capacity degradation and the increase in internal resistance can be monitored. This enables the estimation of both cycle life and storage life, providing performance data for end-use applications (such as energy storage systems) and ensuring that batteries meet usage requirements throughout their designed lifespan.

Batteries with potential safety hazards, such as internal impurities or structural defects, may exhibit issues like abnormal temperature increases, gas expansion, and voltage fluctuations during aging tests. Early identification of these risks can prevent safety incidents, including thermal runaway and fires, thereby ensuring user safety.