"We are determined to improve the squad even further to ensure our continued progression," Sullivan has said.
"We recognise that the club would not exist without its supporter base and would like to thank all our fans for their ongoing magnificent loyal support."
Blues' turnover increased by 7.85% to £24.4m, while match receipts increased by 22% to £10.9m.
However, media income fell by 7.3% to £9.1m because of reduced television rates.