How to win a dominating game?

I currently am stuck in a TERRIBLE winrate (20+ more losses than wins) and all I get in my team are raging players who seem to be braindead. Last game I was playing Zed, and after 20 minutes I got two turrets down in mid lane. All though I was winning my lane, my team gave a free quadra kill to enemy Jax twice, which turned the game around. While the enemy team started split pushing, our Braum decided to all go mid. Jax got another triple kill by that. Lee sin started flaming, our adc went Afk and the game was simply lost by that moment. I really want to climb in at least normals, to face some opponents where I can actually learn something. I know I can't change my teammates, but what can I do myself? Playing with friends is not an option, cs and warding is something that i'm working on. What else is the key to winning with braindead players? (I don't want to blame anyone but myself for having this winrate, since I used to be really, and then I mean REALLY bad too, but I learned and this ruins the whole LOL experience)
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