Hardware accident: Chinese LED lantern turned into a firework

Device brand / model: Yajia YJ-6812
Description: a Chinese lantern with 32 LEDs (quite bright really; 2 levels of brightness); rechargeable (no information on battery currently); without any external power adapters (plugged directly into AC socket by a simple 2-wire cable). Bought on a local Ukrainian (Vinnytsia city) market. The design somewhat reminds of a kind of grater.