NO idea, depends what's making it slippy - moss? algae? lichen? ice?:grease? If its a Victorian tiled path, they just are slippery in the wet.

If your concrete paving stones are slippery when wet, then you can either clean them with a water pressure hose, or scrub them ...

... wet them first with water and then use a wire brush. This summer I scrubbed over 150 pavings in my back garden using this method, and they are now clean and won't be slippery during the wet, cold winter weather...
... I hope this answers your question.

We have victorian flags which get very slippy in the autumn. I either power wash them which blasts off all the green slime or scrub them with a stiff yard brush and watered down Jeyes Fluid or bleach.

try patio cleaner

I use a product called Algon which is available from garden centres. Just dilute it as per instructions on container and apply to your path with either a watering can or sprayer. If you cant find it in your area go the Algon website and they will supply you direct or advise you where to buy it locally.
It takes a few days to take effect and keeps on working over months and months, it is an organic cleaner and is totally harmless to animals and plants. It also has a cleaning effect that restores your path to its former glory. I cannot recommend it highly enough and it is not expensive.