My son's few-years old iPad (who knows what model since Apple stopped actually naming them) turned into a lagfest after the iOS 11 update. UI operations are cho

My son's few-years old iPad (who knows what model since Apple stopped actually naming them) turned into a lagfest after the iOS 11 update. UI operations are choppy where they used to be smooth. Could it be the battery? Samsung, under intense criticism from their Note 7 battery scandal, didn't increase battery capacity with their S8. Instead, they opted to take steps to greatly improve battery life (total capacity loss over time). Whilst I still think retaining 95% after a year is wildly optimistic, I'm happy with this change of focus (yes, I bought one). PS. I noticed that Apple uses lifespan where I use life, and life where I use capacity. Verdict?