Thick cathodes can overcome the low capacity issues, which mostly hamper the performance of the conventional active cathode materials, used in rechargeable Li batteries. However, the typical slurry-based method induces cracking and flaking during the fabrication of thick electrodes. In addition, a significant increase in the charge-transfer resistance and local current overload results in poor rate capabilities and cycling stabilities, thereby limiting electrode thickening. In this study, a synergistic dual-network combination strategy based on a conductive nanofibrillar network (CNN) and a nano-bridging amorphous polyhydroxyalkanoate (aPHA) binder is used to demonstrate the feasibility of constructing a high-performance thick cathode. The CNN and aPHA dual network facilitates the fabrication of a thick cathode (≥ 250 μm thickness and ≥ 90 wt% active cathode material) by a mass-producible slurry method. The thick cathode exhibited a high rate capability and excellent cycling stability. In addition, the thick cathode and thin Li metal anode pair (Li//t-NCM) exhibited an optimal energy performance, affording high-performance Li metal batteries with a high areal energy of ~ 25.3 mW h cm-2, a high volumetric power density of ~ 1720 W L-1, and an outstanding specific energy of ~ 470 W h kg-1 at only 6 mA h cm-2. TOC figure: Synergistic combination of a conductive nano-fibrillar network (CNN) and nano-bridging amorphous polyhydroxyalkanoate (aPHA) binder that affords the high-performance cathode with ≥ 250 μm thickness and ≥ 90 wt% active cathode material. Li-metal batteries (Li//t-NCM) based on thick cathodes and thin Li exhibit outstanding energy storage performance.