A warning has been issued from Sony to all who own a PSP that they should not use third-party batteries for ther PSP. Sony have said to use the official batteries manufactured by Sony to prevent the danger of ignition and explosion etc.

Fake Sony batteries can be just as harmful as third-party ones which the company are not responsible for.
So if you’re thinking of buying some cheap third-party batteries then get some Sony ones instead.
(Via
Playstation Japan)