Solvophobic Binder Crystallinity-Tailored Advances in Solvent-Free Thick Cathodes for High-Energy Lithium Metal Batteries

Developing high-performance thick cathodes with optimized inactive-to-active material ratios is a promising approach to enhance the energy density of conventional lithium-ion batteries (LIBs). However, increasing electrode thickness introduces challenges, including elevated resistance and mechanical issues such as cracking and flaking, particularly in slurry-based wet processes. This highlights the necessity for solvent-free, low-resistance thick cathode fabrication methods. In this study, the impact of a solvent-free mechano–thermal fabrication process on the electrochemical performance of high-nickel ternary metal oxide-based thick cathodes is explored. A key challenge identified is the formation of solvophobic crystalline structures on the surface of the active cathode materials. To address this, a fast cooling strategy is implemented at the end of the solvent-free fabrication process, which successfully reduced the solvophobic crystallinity, ultimately surpassing the electrochemical performance of cathodes produced through wet processes. Furthermore, incorporating a PVDF/succinonitrile (SN) mixture binder via liquid-phase mixing further minimized crystallinity, resulting in significantly improved electrolyte wettability, ionic conductivity, and mechanical adhesion. As a result, the mixture binder system achieved a high areal capacity of ≈11 mA h cm⁻² and demonstrated stable cycling performance over 100 cycles. When paired with a lithium metal anode, the thick cathode attained an energy density of ≈418 W h kg⁻¹, translating to ≈335 W h kg⁻¹ with packaging—representing approximately 35% improvement over current LIB technologies.