Push-Pull Interplay of Soft/Hard Magnetic Spin Junctions for High Performance Ammonium Ion Pseudo-Capacitors

Spin control for interfacial charge/mass transport plays a decisive role in achieving elevated energy density while retaining power density in a hybrid supercapacitor. Interfacial charge-transfer improvisations by push-pull spin control strategy among two magnetically distinctive materials offer a unique way to enhance the intrinsic characteristic of the electrode. Herein, we present a push-pull strategy at the intersection of soft/hard magnetic spin junction, where spin-ordering in soft magnetic (SM) Co(1,4-benzenedicarboxylate) (CBDC) layer is induced by hard magnetic (HM) MnFe₂O₄ (MFO) nanoparticle under the influence of an external magnetic field. Specific capacitance of CBDC-MFO@CSF electrode is increased from 612 to 1015 Fg^-1, capacitance retention from 30% to 50% across a 1.6 V operating range, from magnetically induced ferromagnetic ordering in CBDC layer activating more Co²⁺ sites and facilitating charge/mass transport for superior charge storage. When 0 and 18 mT activated electrodes are assembled into a hybrid device, the energy density of the magnetically activated electrode is increased to 146 Whkg^-1@ 800 Wkg^-1 compared to a non-magnetically activated electrode (81 Whkg^-1 @ 798.4 Wkg^-1) without compromising power output. Improvement in mass/charge transport for the magnetically activated electrode suggests a direct consequence of the induced spin ordering and pinning, which favors enhanced diffusion dynamic control at the electrode-electrolyte interface.