Had my inspiron 5547 for roughly 3 years. just noticed this happening after my last service with DELL. Initially I thought it was bloating but upon further inspection, its like the cells are actually built into blocks to buldge out and it pushes onto the frame and distorts the left side of the laptop.
From the images, you can see the slight buldge on the battery itself. I ordered a replacement for USD45+ but not too sure if the new battery will have the same issue.
Get rid of that battery - no it's not safe. Recycle and replace it.
already ordered a replacement battery. apparently it takes 7 to 14 working days.
For your safety and to avoid damaging other components, dispose of the battery immediately (the system will run just fine on AC power alone in the mean time).
If the battery is three years old it's had a good lifespan - normal is 18-24 months, so you've exceeded that by a significant percentage.