PP1866 PATEL

Hi, I have a child over 18 who has been unable to work due to on-going illness for the past few years and for whom, I am looking at opening and contributing to SIPP. I am aware that the maximum net amount that I can pay into the SIPP and receive a basic rate tax rebate on is £2,880. But, is it possible to contribute more the £2,880 with no tax relief rebate? If so, what is the maximum gross amount that I am able to contribute each year? Thank you.