Possible causes are:
1. Charger failure: There may be a problem with the power adapter or charging cable, it is recommended to replace or overhaul.
2. Charging cable damage: The charging cable may be damaged, resulting in slow charging speed, you can try to replace a new charging cable.
3. Mobile phone software problem: There may be an anomaly in the mobile phone system, resulting in slow charging speed. It is recommended to update the system or clean it with one click.
4. Aging of the battery: The use of the mobile phone battery for a long time may cause aging phenomenon, resulting in slow charging speed, it is recommended to replace the mobile phone battery. You are advised to locate the problem and take appropriate measures based on the above possible causes.