I would assume you could do a chemical solution to this, where the explosive slowly oxidizes instead of quickly. But that would slowly degrade the effectiveness of the explosive, while likely increasing manufacturing cost exponentially.

They already have this. It has been around for about 20+ years now and is actually the preferred solution in the west for a very long time. Most of the land mine treaties require it too. On that note, the US and Russia are not signed onto most of those treaties. The US didn’t want to sign due to certain requirements that seemed militarily poor, too much mandatory reporting that seemed like a security risk for leaks, and too restricted, but was fine with the self disabling mines (because who do you think makes most of them?). Russia disagreed because they don’t have the money to switch to new manufacturing and didn’t care if they don’t disable over time.

The most common design is a UV degrading plastic that will break down over some determined amount of time. Or another method is an internal degrading plastic that degrades over time. Either way the trigger mechanism becomes inert after a while. This has then led to issues with locals harvesting old inactivated mines for their still usable explosives and using it in other things (IEDs)

There are also some designs with self detonating ones, to mitigate the above problem, but have been met with questionable results. It does stop the issue of explosive harvesting, but now you have a field that randomly explodes and can’t really promise that they all exploded, so there might be some that are still live out there after the locals are told it should be safe.

There has also been attempts to make remote controlled mines. Mines that can be remotely disabled for friendly troops, then reenabled for defense, then remotely detonated when done with. But there are obvious electronic warfare issues. The concept is basically reattempted then quickly reabandoned about every decade.