Hello, your project is not very clear, do you need some one to design (make 3D model & detail) of your project, or to manufacture your project, or to plan & make schematics (electrical / electronic layout) for the project, or manufacture a lithium battery, because you have not provided enough specification, just that there is 15.6 inch screen.
I have 10 years of experience in product design and if you are just looking for battery design & manufacturer, you can have many Chinese people providing cheap solution