Apple India — IPad Air 2016 battery problem

Hey There
The problem in my iPad Air 2016 not only my iPad but all other apple devices are having some and some issue like battery problem as in my case then slowing the older devices and opened screen and more. Tell me what the hell battery you all are putting I know the device performs slower when it gets older but what if a battery doesn't charge I cant waste my precious money on that ### battery from your company and the accessories are more expensive apple is ### shall I approach the court and tell them. Please don't tell that ### that have you used it properly the battery is fake or not. Its real bought from the company