Xiaomi Smart Band 7 Manual Del Usuario página 20

The lithium polymer battery in this band cannot be removed.
To avoid damage to the battery or the band, do not replace the
battery by yourself. There is a risk of explosion if the wrong type
of battery is used. Do not dispose of used batteries with household
waste. Dispose of this band and used batteries as per local laws
and regulations.
Do not disassemble, strike, crush or throw the battery into fire.
Stop using the battery immediately if there is any swelling or fluid
leakage. Do not expose it to sunlight, fire, or environments where
the ambient temperature is extreme heat.
When planning not to use the band for a long time, turn it off and
then put it away. To avoid damage caused by the over-discharge
of the battery, fully charge the band every 6 months.