All excellent tips above.
I do a similar distance (slightly shorter, more country lanes) year round.
Lights: A good hub dynamo setup is expensive but soon pays for itself with that kind of distance. Battery lights are very good these days, but I still like the convenience of not worrying about charging. You also need a backup. Two rear lights (eg. one constant, one flashing) is good because you might not notice a failure. Carry a head torch, not only will it get you home in the event of a light failure, mending a puncture by the light from your phone is a pain in the arse.
Hi-Vis: Can be useful, but a Sam Brown belt or gilet can be an irritation. Consider some on the bike, eg 3M tape round a third of the rims is amazingly effective, it is in direct line of dipped headlights and produces a flashing line from many angles. Some people put a line of tape on the cranks for a similar effect.
Helmet: much the same arguments as in daylight, but you will find you get more space from drivers in the dark. If sliding on ice is your worry here, you're more likely to hit the ground with your hips or ribs than your head.
Tyres: rubber gets hard (= slippery) at low temperatures. Tyres with soft rubber designed for the cold will keep you upright. I rate the Michelin power all season (previously known as Pro Grip). A lot of tyres with "4 season" in their names are definitely not suitable for cold roads. If you're really hard core, then studded tyres will grip on sheet ice but you only need them a few days of the winter and are not much fun to ride when it's not icy.
Clothing: Wot Karla said. A long sleeve merino base under a winter jersey is fine down to about 5C, any lower then a windproof jersey with the same merino base. Carry a light waterproof in case it rains, which is a lot less often than most people imagine. And good gloves. A wool hat and buff are great as they are easy to take off when you get too hot.
Overall: with the right gear, riding in the dark mornings and evenings is fantastic.