Don’t know if this counts but Alolan Golem has 130 Base defense, and is supposed to be a very defensive Electric type Pokémon. I mean, it’s EV yield is 3 Defense and it’s made of rock.
Magnezone has good defense, and it’s steel typing is undoubtedly defense based. However while it is a defensive steel type, people usually invest in a special attack boosting nature.
Smogon suggests to run Zapdos with a defensive 240 Def/ 248 HP EVs. And a Bold nature. So Zapdos is good defensive electric type.
Zekrom has good defense and is usually ran as a tank.
Elektross is usually ran defensive or special defensive, due to it having no weaknesses.
Rotom Wash is usually ran as a tank but sometimes a sweeper.
Honestly electric types are a joke..