Have you already tried the classics like THREE.js, j5.js, also ZDOG - a little newer one, is a good choice for some projects. It's quiet useful for learning and great for e.g. simplier but good working game animations, but also cool and easy to use with HTML5-implementation.

There are also Anime.js, Green Socket, Motion One and a lot more - it depends what exactly you want to animate and in which kind of environment in detail, but for mobile I'd suggest mostly THREE.js to work with at first, because it's relativly fast to learn, you have a good control over your actions and it's pretty versatile.

Have fun trying some out and chose what works best for you!