Iphone 6 battery

You can pay for a battery replacement service from Apple or an Apple Authorized Service Provider. The costs will depend on where you're located and if the service is directly from Apple or an AASP. There can be additional costs if the device is damaged. For example, if there's a damaged display assembly, they won't install a new battery without the screen being replaced.

Hello Doriiiiiiiii,

Thank you for using Apple Support Communities.

I understand that your iPhone needs a battery replacement and you want to purchase a replacement battery. The battery for the iPhone 6 is not a user replaceable component. You can use the information in the following support article to set up service for a battery replacement and the cost of that repair.

iPhone Battery & Power Repair - Apple Support

Best regards.