Someone I know designed a wood-splitting axe where the central part of the blade has a high center-of-mass and freely pivots in order to kick apart the pieces once the axe hits the wood. It’s an ingenious design based on simple physics, and works quite well. There’s no purchasing info at the link below; it’s a small company whose main focus is on machines for metal roofing, so I suppose it requires a phone call or email to them to find out more.

https://www.esemachines.com/hand-tools Search for “super splitter”

The patent description is more informative: https://patents.justia.com/patent/5020225