Hi!
To open up a battery you should only need prying tools, just remove the plastic covers. The only things that you will find inside are the battery's cells that have a cable tied and soldered to them and a PCB where they all come together. You can find only the cells, but I am not sure if you can buy that link between them (and soldering it yourself is a no-go - the fire hazard is immense - battery cells + soldering iron can only end bad). That PCB also needs to be powered at all times, because if it looses power it won't be useable again (at least mine did that - I only found out after the fact).
Therefore the best solution is to get a new battery. I would also get the Duracell if I were you, I wouldn't want some cheap junk in my laptop.
Amazon Germany seems to have the original OEM part, but it's quite expensive at 90€: https://amzn.to/2AltdRv