A few big points here:
1.) You are lacking proper involvement in the hips through the whole lift. You really need to engage your glutes at the top when you lock out. You aren't completing a full rep in the video, you still need to fire those hips forward.
2.) You aren't getting into a good starting position, and you lift a lot with you lower back muscles. This ties in with the glute thing. It looks like you are leaning your shoulders over the weight, which is only helping facilitate your lumbar muscles in the lift and inhibiting your glutes and hamstrings in hip extension. You need to either have your shoulders above the bar, or better, slightly behind. Think of pulling the weight back towards you, not straight up.
3.) I think you lack flexibility in your posterior chain, probably in the calves, hamstrings and glutes. Stretching those muscles out will help you get into a better starting position.
4.) You bend your elbows in the top 1/3 of the lift, this does nothing but overload your elbow flexors, especially when you start lifting heavier weight. Bending the elbow does nothing for the lift, make sure your arms are locked out in the start of the lift, and stay that way through the entire movement.
So simple pointers here for improvement:
1.) Stretch out your glutes, hamstrings and calves before lifting so you can position your body efficiently in the lift.
2.) Get your shoulders slightly behind the bar with a "big chest" postured up, and an arch in your lower back.
3.) Really press your hips forward at the top of the lift to complete the full range of motion and encourage hip extension.]
4.) Keep arms straight.
5.) I can't see your feet, but make sure your feet stays flat on the ground, while pressing into your heels.
Slowly integrate those changes in with light weight and lots of sets with low reps, this way you won't fatigue your body, but you can retrain your movement pattern.
Doing some glute-bridges before your deadlifts can also help you incorporate better hip extension -
^ You can have your feet flat on the ground though, no need to post up on the heels like in this video.