I am looking for a device which cuts off the connection between batteries and the system just like a circuit breaker when my 12V battery goes below 9V(for example) for preventing it from dying completely. I can use a comparator circuit and a power relay however wondering if something off the shelf can do the job.
You did not indicate the current load, so here are a couple of alternatives.
The first possibility is an actual battery-protection IC, or you can coax a high-side driver or power sequencing switch to do the job. But you would still need to add some circuitry around any of them to make them work.
A second possibility is just a circuit with an adequate PMOS. There is quite a bit threshold variability and you would want something steeper than a gradual current reduction. Just adding a Zener might be enough. Here are a couple of ideas that should be refined somewhat before being put in practice.
But you might want to add some hysteresis, so that the removal of consumption from your circuit does not turn the pass switch back on and you end up with a power oscillation.
And of course, you could put together a similar circuit with a relay instead.