Below quoted from ICAO site
CAA guidance to film crews – Spare lithium batteries forbidden in checked baggage
Following a recent incident on an aircraft the CAA are reminding film crews to be aware of the rules relating to lithium batteries carried in baggage. During flight it became apparent that a cameraman had spare lithium-ion batteries in his checked (hold) baggage. Because lithium-ion (and lithium metal) batteries can cause fires if not handled appropriately, international rules require them to be carried in the cabin in carry-on baggage. Consequently the Captain decided to return the aircraft to the departure airport, resulting in great disruption to both passengers and the airline. An in–flight return is hugely expensive and some airlines have, in the past, pursued passengers for the associated costs.
To underline the importance of carrying spare batteries correctly, the CAA is offering the following guidance to anyone travelling with them:
1. Spare lithium batteries must be carried in carry on baggage, and the terminals protected from short circuit (e.g. by packing each battery in its own protective case or resealable plastic bag, such as a sturdy freezer or sandwich bag.).
2. Generally, lithium-ion batteries carried on aircraft must not exceed 100Wh. However, batteries up to 160Wh may be carried with the approval of the airline.
Other rules apply to batteries and many other items which can and can’t be carried on aircraft, there is more information here: