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Lithium Ion Batteries are rechargeable batteries, Lithium Metal Batteries are single use batteries (Primary Batteries).
Lithium Metal Batteries are known to be more hazardous than Lithium Ion batteries.

Different entries are there in UN Model Regulations for Lithium Metal and Lithium Ion batteries , the reason is to facilitate the transport of these batteries for specific modes of transport and to enable the application of different emergency response actions. Lithium Metal and Lithium Ion Batteries are known to be involved in many incidents on air transport including loss of total flights and lives on board.

Special provision 188 of IMDG Code exempt lithium batteries from other provisions of the Code, however, shipment must meet following provisions of SP 188

1. Lithium Content / Watt hour rating for cells
2. Aggregate lithium content / Watt hour rating for batteries
3. Manufacturing and Testing
4. Package
5. When Installed in Equipment
6. Package Marking
7. Drop test of package
8. Gross Mass of Packages

Click on below link to download presentation to understand SP 188 in an easy way.

SP 188 Lithium Batteries (IMDG Code 38-16)