It is waterproof to a certain extent.
According to the query on Baidu Youdriving, lithium batteries have certain waterproof properties if only exposed to rain for a short time, there will be almost no problem , just dry them. . However, if the lithium battery swells, it means that water has entered inside and it is not suitable to continue using it at this time.
Lithium battery is a type of battery that uses lithium metal or lithium alloy as positive/negative electrode materials and uses non-aqueous electrolyte solution. Lithium metal batteries were first proposed and studied by Gilbert N. Lewis in 1912. In the 1970s, M. S. Whittingham proposed and began studying lithium-ion batteries.