Hallo Abhishek,

it would be better than nothing. But I think that diode does not switch-off sharply enough. So, when having battery all the time connected to charger there would still flow too much current into battery. On the other hand you could design circuit that charging voltage never goes beyond maximum voltage of about 14V. But then you will have to live with not fully charged battery.
There is another disadvantage of your diode methode. For working correctly charging voltage must be stabilized with some regulation circuit, like LM317 or so. But then again you 'suffer' from heat dissipation.
Nevertheless, if some timer is used for protecting against overcharging, your diode methode can be helpful.

Bye,
Kai