The full CHF 100'000 in capital, required as the minimum capital for an AG, must be paid in to the existing GmbH before the change from a GmbH to an AG can occur. A partial payment of the capital in not possible according to the commercial register practice and this link:
You can use the capital from your business partner for sure. But you need to have 100'000 CHF. You can also declare different stuff (company car, furnitures, etc.) to the start capital. You do not need to have this money in cash.
You have to check with your accountant, what are all the stuff what you can declare to your business, than check it, how much you need to have 100'000 CHF.
Ask your accountant and lawyer for exact information, but as I know you can do it as I wrote it before.