What factors are related to battery capacity？

In the cold winter, when we play with our mobile phones outdoors, we find that the battery power is used up faster than in the summer; fast-charging batteries are used up faster than slow-charging batteries. So what factors are related to our battery capacity?

1. Temperature

Temperature has a significant impact on battery capacity. As the temperature rises, the capacity of the battery increases. First, rising temperature promotes chemical reactions inside the battery, and lithium ions move faster, so the available capacity increases.

Secondly, under low temperature conditions, the electrolyte becomes viscous, the conductivity of lithium ions decreases, and ohmic polarization, concentration polarization, and electrochemical polarization are all aggravated, which hinders the embedding of lithium ions.

Moreover, the lattice of the positive and negative electrode materials shrinks at low temperatures, and the channels for lithium ion embedding and extraction become narrower, requiring more energy to complete the reaction, resulting in electrochemical polarization. Low temperatures slow down the charge transfer rate on the electrode surface, just like wheels slipping on icy roads, and ions accumulate at the interface to form concentration polarization.

2. Discharge rate

As the battery discharge rate decreases, the battery capacity also increases.

At low discharge rates (such as 0.2C), lithium ions have more time to deintercalate from the positive and negative electrode materials, reducing polarization losses. However, at high discharge rates (such as 1C), lithium ions migrate too quickly, preventing some active substances from reacting quickly, resulting in reduced capacity utilization.

A low discharge rate is like squeezing toothpaste hard until it's almost empty, but if you squeeze more slowly, you can still use it for a while.

3. Charging rate

Charging at a low rate reduces the polarization effect within the battery. The lower the charging current, the more fully lithium ions diffuse through the electrode material, minimizing energy loss. Simply put, slow charging allows the battery to be fully charged, allowing it to deliver more power.