Plug-in electric vehicles’ charger is preferred to cover an ultrawide battery voltage range with the vehicle-to-grid capability. Conventional bidirectional resonant dc–dc converters suffer from the contradiction among wide voltage gain range, squeezed dc-link voltage span, and narrow switching frequency band. To solve the issue, this article proposes a novel H5-bridge-based bidirectional CLLC converter. By configuring the switch pattern, the H5-bridge can form the modes of single half-bridge, dual half-bridge, half full-bridge, and dual full-bridge, respectively. Correspondingly, six gain curves can be derived. Combined with the variable dc-link framework, the converter constrains the switching frequency in the vicinity of the resonant frequency with optimal efficiency. The converter achieves an ultrawide battery voltage range with a squeezed dc-link span. A bidirectionally synchronous rectification method is proposed to improve the efficiency further. To verify the proposed concept, a 1-kW rated prototype with a 320–420 V dc link is built and tested. It validates the battery voltage 55–420 V for charging and 230–420 V for discharging. Zero-voltage turn- on and zero-current turn- off are achieved in the rectifying mosfet s. The prototype exhibits 98.04% peak efficiency and good overall efficiency performance.