My iPhone SE (1st Generation) keeps turning off even with a full charge

Hi there, my iPhone SE first generation is causing some issues. The phone powers off when it shows a 10% battery charge in the top right corner. The odd thing is that the phone shows a 100% charge when I power it back on. The phone has been charging all night so it should be charged, yet as soon as I take it out of charge, it will flash from 100% to 10% and then power itself off. I know that in the past, Apple admitted to weakening the batteries of their devices, is that what is causing this problem?

In the settings tab, under battery, the battery is still at 79% capability. What is the problem here? Is it the battery that needs replacing?