2 separate things here: low battery life and lag. The battery life decreases with age and cannot be helped, you just have to get a new battery. It depends on usage.
The lag is a separate thing. What software did you install recently? Some older software has compatibility problems with new editions of Windows. Some programs have components that always run in the background, causing general slow down. Some antivirus programs have development cycles that do not catch up with new versions of Windows 10 and cause problems.
The lag is a separate thing. What software did you install recently? Some older software has compatibility problems with new editions of Windows. Some programs have components that always run in the background, causing general slow down. Some antivirus programs have development cycles that do not catch up with new versions of Windows 10 and cause problems.