The USPS requires specific labeling for lithium-ion and lithium-metal batteries to ensure safe transport. Lithium-ion batteries (over 100Wh) need a Class 9 hazard label, UN3481 marking, and proper packaging. Lithium-metal batteries (over 0.3g lithium) require… What Are the USPS Lithium Battery Label Requirements for Lithium-Ion vs. Lithium-Metal?