Hi @anwar0 ,

After 2 years of non charging the battery has most probably become depleted beyond recovery and would need to be replaced.

According to the ifixit Apple Pencil Teardown guide, the pencil is very difficult to repair.

It may also be that it will be difficult to source a suitable replacement battery if you did decide to try and open it without damaging it too much and causing more problems.

Repairing the pencil may not be an option