As far as I know, not too much. It's got pretty bad energy density and nowadays it's very common to just skip it entirely. It's real claim to fame is safety- it's not any cheaper despite the materials (half the cost per kg * half the capacity per kg = the same cost), and I haven't heard much about improving the performance.

Meanwhile other chemistries have shown much greater improvements in safety, energy and power, and price is understood to be more about the scale than the chemistry.