There are a few ways to address grip strength issues while deadlifting:
- Switching to a mixed/over-under grip
- Switching to a hook grip
- Using chalk / liquid chalk
- Using straps
Directly strengthening your grip is also a good solution. /r/griptraining is an excellent resource for this pursuit.
Keep some perspective, however. Although your grip strength may be the limiting factor in your deadlift right now, remember the deadlift is not a grip exercise. You should never let your grip strength determine how much weight you train your deadlift with. The strongest men and women in the world use straps for their max deadlifts – there’s no shame in it at all, despite what internet trolls will try to tell you.
If, instead, your grip issue is that you are tearing callouses or pinching your skin, you should watch this video, as it is likely that you are not correctly gripping the bar.