JD.com (京东商城 [Jīngdōng Shāngchéng]) is THE big competitor of Tmall. The platform has everything you want and is specialized in high tech and AI products. It claims to be the world biggest delivery platform for drones.
You can also do your grocery shopping on JD and pretty much anything else.
Unfortunately, even after their partnership with Wal-Mart, the website as well as the app are only available in Chinese, just like Tmall and Taobao.