Maha has one that uses 8 cells and puts out 9.6v as well.
As bcwang cited, there are Maha 9.6v 230mah NiMH batteries as available from T-D that serve my fire and smoke and CO2 detectors quite nicely. Are these batteries identified as "low self-discharge"? no, but the quality of this specific battery is high enough that I don't really care about the difference. I have almost a dozen in use in various smoke/ionization/CO2 detectors or several wireless mikes at church. no problems except that these 9.6v batteries are a shade larger than normal 9V batteries. The pastors have to pay attention to how the batteries are inserted into the wireless mikes. I lost 3 of the batteries to bent and finally broken-off terminals before the pastors understood what to do. On the other hand, the services are not bothered any more by the nearby state police tower breaking up the wireless mike transmission during a sermon ....! the advantage is due to the higher output voltage of the 9.6 battery and therefore higher transmission power from the wireless mike.
FWIW, I consider a smoke detector application to be low power such that the self discharge characteristic of the battery will be the primary driver as to length of use before recharging/replacement. With the maha 9.6v batteries in a various detectors, the run time is somewhere between 6 and 12 months before the "replace battery" beeper kicks in - all depending on the specific detector. The combo ionization/smoke detectors or CO2 detectors draw more current than just ionization detectors. Will those 9.6v batteries still supply sufficient current to signal a _loud_ warning buzzer or beeping close to the end of their useful charge? There was a CPF thread a while back that discussed that aspect at some length. I tested a few of these specific Maha 9.6v batteries under something I thought was close to end of charge - I had to plug my ears to let the detectors sound off long enough to be believable. no problem.
An example of an actual usage mistake is related to one of my 3 CO2 detectors which normally run on AC power and use the 9.6V battery as a backup. I charged the Maha 9.6v battery in the summer, put it back into service and forgot about it. A handyman was working at our house during the day a couple days ago and pulled the wall-wart from the mains outlet - and left it that way. Somewhere about "oh-dark-thirty" (middle of the night for the non-military-ops people) the low voltage signal woke us up. Battery mission accomplished!
Ergo, While a 9V battery with the label of "low discharge" does not appear to be available, in my experience the Maha 9.6v battery possesses sufficiently adequate electrical/chemical characteristics to come close enough to a "low self-discharge" battery for my usage.
BTW, you really need to purchase the Maha MH-C490F charger that charges four 9.6v or 9V cells intelligently in a few hours, not all night as is usual with 9V charging stations. and then leave the cells on trickle charge after charge termination for longer than an hour. I credit that charger for saving 4 existing older 9v batteries from the recycling bin. It took a few charging cycles but the old 9V batteries were sufficiently rejuvenated to become useful again.
