Smaoke alarms for flats

Maintenance

I have 4 flats all have there own external access. I want to update the smoke alarms, and am thinking of fitting 10 year battery alarms, one by the staircase or hall and one in the kitchen, is this ok? My electrician says they should be mains linked alarms which will be difficult and expensive to fit, it seems according to a number of websites that a 10 year battery alarm is adequate. Perhaps you could help. At present the flats have working single normal battery life alarms in the hallway or stairs. Kind regards, Roger Plant.
PS the flats were purpose built in 1954.