Qualcomm and the Rezence wireless charging standard had tech that was able to charge through metal backs since 2015. The issue is it’s not compatible with Qi which already cornered the market so no one used it.
Or just do it like the Zephyr way. Shoot the tentacles and redistribute the damage. Though I’m not sure if that would be better or annoying since it may unintentionally block weapons fire if there are a lot of tentacles.