The Lenovo 5B10T04980 rechargeable battery pack, model L18D3PG2, is the Capela SD/C variant listed for Chromebook use.
It uses lithium-ion chemistry; the distributor specifies lithium-polymer chemistry. The rated energy is 57 Wh, with a voltage of 11.52 V and a listed charge capacity of 4830 mAh. Its size is identified as proprietary.
Compatibility is listed for Lenovo 14e Chromebook models 81MH000BUS, S345-14AST and 81MH0024US. These model numbers help identify whether the pack is specified for your computer.