My iPad Air 2 has black screen and won’t charge

The symptoms that you describe may indeed suggest a failing/failed battery. 

Connect your iPad to its Power Adapter and allow the battery to charge undisturbed for at least an hour. Then, while still connected to the Power Adapter, attempt a forced-restart:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

Are you able to use the iPad while remaining connected to your Power Adapter - without recurrence of shut-down or a crash? If yes, while monitoring the indicated battery state, disconnect the Power Adapter; if the indicated battery state suddenly falls, or the iPad shuts-off, this test demonstrates the iPad battery having reached the end of its usable life:

iPad Repair & Service - Apple Support

Otherwise, these support pages should help with troubleshooting battery and charging issues:

Charge and monitor the iPad battery - Apple Support

If your iPad won't charge – Apple Support

Troubleshooting generally requires substitution of the Power Adapter and cable for another known-good item. Most models of iPad require a Power Adapter rated at 12W or greater to reliably charge. 5W Power Adapters intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow.

Be aware that many computer USB ports cannot source sufficient power to charge an iPad. Unless explicitly designed for charging connected devices, computer USB ports are typically limited to 0.5-1A @5V (i.e., 2.5-5.0W).

If you continue to experience difficulties when using an appropriate Power Adapter of 12W or greater, you might be best advised to seek assistance directly from from Apple Support - and request a remote diagnostic test. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/gb/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Power Adapter and cable(s):

Genius Bar Reservation and Apple Support Options - Apple

Battery replacement - if required - can be arranged via the Genius Bar. This avenue provides opportunity to have your iPad properly tested before committing to the cost of a battery replacement.

Alternatively, you can use Apple’s mail-in repair service - for which you can find details and costs here:

iPad Repair & Service - Apple Support

Dying at 88 percent sounds like the battery is done. When the battery went south on our iPad 5, it would go from fully charged to shutdown in 13 minutes. Holding butoms won't help if the battery has failed, which I believe yours has.

Start here:

iPad Repair & Service - Apple Support

There is a cost estimator on that page. I highly recommend the ship-in/mail-in service. We used that for the battery service for our iPad 5. I dropped off the dead iPad at a local UPS Store on a Friday morning and had the replacement iPad on Wednesday.

Apple does not put a new battery in your iPad. You get a refurbished iPad of the same model and specs but with a new other shell and battery, and a warranty. The one I got was perfect in every way and continues to give excellent service.

See: Learn more about each refurbished iPad.

You’re very welcome.