Anti-gravity battery

Is anyone using a lithium starting battery like the American anti-gravity offering , other makes are available. I'm quite taken with the removal of 8kg ish of permanent weight by going away from lead acid. The packaging is also way smaller for more CCA 460 over 330 even if they overall capacity is less at 16Ah instead of 40Ah but I don't really need that as I don't tend to run the stereo without the engine and I'm not leaving the car unattended for more than 10 hours a day for it to drain down. I appreciate the relatively extortionate price difference but less permanent weight is less permanent weight. Unless I'm missing something?

Generally Lithium packs tend to be less tolerant of high temperatures, so whichever product you pick I would check the Jimny under bonnet temperature is within the product operating spec. I am assuming you want to fit it in place of the current lead acid?
Just something to consider 

Admittedly I am looking at a bike battery from anti-gravity because their 054 replacement is like 1200 CCA and 30Ah but that's excessive for a Jimny and it's also only about half the weight. I'll have a look at the recommended operation temperature and possibly run a thermocouple next to the existing battery and compare.

Lithium batteries don't like cold temperatures. It's really bad for them to charge below 0 degrees C, which could be a problem if you leave the car outside in the winter.

In my opinion lithium starter batteries are over priced. For a motorsport or aircraft application the weight saving could be worth it. For normal use there are cheaper ways of saving 8kg.

Interesting stuff, had a look at Anti-gravity batteries web site, never heard of them before.
I've used Lithium Ion / Poly batteries many years ago (power packs for model aircraft). They had an amazing weight to energy density which made them ldeal, but I do remember they took a lot of looking after to prevent fires or failure.
This may be why I have a lot of questions about retro fitting to a vehicle not designed for them.

Temperature is one already highlighted.
I assume these batteries have all the required BMS circuit inbuilt, it's essential for keeping them balanced in use and provide protection.
What about the Jimny alternator regulator, I notice Anti-gravity sell lithium compatible ones for bikes. Can the BMS cope with this or is it an issue / going to reduce pack life?

Charging method is critical on Lithium packs, so struggling to see how you can just shove 14v on them without some form of charge balancing and monitoring.

​​​​​​​Not trying to put you off, just some of the questions for which I would be seeking answers.
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I have been using a LiFePo4 as a starter battery for the Jimny now for 3 years. I got it directly from China so it as not so expensive. And I think it is very important: LiFePo4 and not LiPoly (even lighter but quite dangerous!)

So far everything works fine. I did not have any issues in cold weather, although in the last 3 years it was not colder than -10°C (just switch the light on for 20 sec and wait for 30 sec). And I did not have any issues in hot weather - there was plenty. It was not so easy to find a battery that has a BMS that allows more the 50-100 amps for discharging.

Because I use a refrigerator, I got a 40Ah battery which is more than required for starting.

Im motorbikes I have been using LiFePo4s for 5 years and they work great. I do not load them in the spring, do not disconnect them (I have older bikes without anti theft etc. so there is no constant power drain) and the bikes start perfectly. The only problem with the bikes is the fuel quality so last year I started to drain the fuel before the winter. Before installing a LiFePo4 I would check that the maximum voltage during charging is less than 14.8V at any time.

If external charging is required, make sure the charger does not have a program for desulfurization on, trickle charge, battery regeneration etc. because everything above 15V will kill the battery. The old, heavy, chargers are fine and of course any charger for LiFePo4. But I did not need to charge my LiFePo4s so far.

I got the LiFePo4 for the Jimny, because I had good experiences with motorbike battery and I needed a new battery and the price was „only“ double the price of the lead acid battery.