Short Circuit - Battery Design

By short circuit we mean an electrical short circuit, a very low resistance path between the positive and negative sides of the cell or cells. A short circuit can be inside a battery cell or external to a battery cell.

Internal Short Circuit

There are a number of things that can cause an internal short circuit within a battery cell. The primary focus has to be on manufacturing and the processes deployed to mitigate or reduce these risks.

Metallic foreign body in the raw materials
Introduction of a metallic particle during cell production
Damage to electrodes
Particles or damage during tab welding
Particles from cell case welding
Dendrite growth during cell use

External Short Circuit

External short circuit tests are applied at Cell, Module and Pack level.

A number of methods are normally deployed to reduce the effect of external short circuits, including:

fuse in main electrical circuit
Current Interrupt Device inside the cell
current measurement by BMS and control of contactors to connect/disconnect external circuit

Influences as listed by Zhang et al [1]:

Pouch cells, tested with capacities from 0.017 Ah to 15 Ah, showed electrode damage and minimal impact of aging on external short circuit behaviour.
Cylindrical cells, including 18650 formats, with capacities between 1.1 Ah and 25 Ah, exhibited hysteresis in thermal behaviour and increased charge transfer resistance with repeated external short circuits.
Tests conducted at temperatures ranging from −20 °C to 80 °C indicated that extreme temperatures significantly affect battery performance, with observations of electrolyte leakage and membrane closure.
SOC levels from 10 % to 100 % were studied, highlighting that higher SOCs lead to more severe short-circuit reactions.