they now do direct replacements for regular 12v Lead Acid Batteries in the Lithium Ion format, aimed at the leisure market, apart from being a lot longer lasting and having more energy density, they are also a fraction of the weight.
I was recently watching a youtube vid, by a guy who has a narrow-boat, and he made out that replacing his three 12v Lead Acid batteries with the Lithium Ion equivalents was worth while, if not cost effective.
Of course the downside is cost, but could be worth paying for some.
Leisure batteries tend to be be lead acid but use gel instead of water making them safe should they leak or spill.
Lithium ion batteries don't like the cold, over wintering them outside may damage them.
Yep Bramston, the guy with the narrow boat did mention the importance of keeping Lithium ion batteries above a certain temperature, and he did find a solution, using insulation and other factors.