Lithium batteries are Class 9 dangerous goods and must be declared for both sea transport (IMDG Code) and air transport (IATA DGR), whether shipped alone or packed inside products. Lithium-ion batteries shipped alone are UN 3480; when packed inside equipment or together with equipment are UN 3481. Lithium metal batteries are UN 3090 and UN 3091. Shipments require UN 38.3 test summary and Safety Data Sheet (SDS), and the packing list and commercial invoice must state the details clearly—if documents are not clear, freight forwarders cannot book space.
Full explanation and HS code list: https://patisco.com/zh/eu-check/lithium-battery-shipping Use HS codes to check which EU regulations apply to you: https://patisco.com/zh/eu-check