Dry powder fire extinguishers mainly extinguish flames through chemical inhibition and physical coverage. The powder they spray can isolate oxygen and interrupt the combustion chain reaction. For common solid, liquid, and gas fires, this dual mechanism is highly effective. However, lithium battery fires are of the re-ignition type caused by chemical energy release, and dry powder is difficult to continuously inhibit the internal reaction. 

Thermal runaway characteristics: When there is a short circuit, internal temperatures will continue to rise and flammable gases will be produced. 

Reignition risk: Even if the surface flame is extinguished, the electrolyte may still catch fire again. 

Chain reaction: A single cell catching fire can cause the entire battery pack to catch fire as well. 

In case of lithium battery fire: 

Use special fire extinguishing agents preferentially (e.g. aerosol or lithium blanket) 

Without professional equipment, water can be used extensively for cooling (be sure to prevent electric shock) 

Sand cover can be used as a temporary measure, but it must be completely airtight. 

Always maintain a safe distance and avoid inhaling toxic smoke.