Intraphase electronic coupling in Ni₃Sn₂S₂@nitrogen-doped carbon for high-rate and durable potassium-ion batteries

Bimetallic sulfide, with its high theoretical capacity, is one of the preferred anodes for high-energy-density potassium ion batteries (PIBs). However, its low conductivity, high volume expansion, and slow electrode reaction kinetics have limited its practical application. This study developed a freeze-drying-calcination coupled strategy to fabricate a porous nitrogen-doped carbon matrix embedded with Ni₃Sn₂S₂ bimetallic sulfide nanoparticles (Ni₃Sn₂S₂@NC). The enhanced electrochemical kinetics are primarily attributed to the strong electronic interactions between Ni and Sn atoms within the hexagonal crystalline framework. The reduced adsorption energy of potassium ions (K⁺) and the significantly enhanced diffusion coefficient (∼2.88 × 10^-10 cm²/s) are attributed to the electronic coupling effect within the bimetallic sulfide phase. The electronic interaction effectively promotes both K⁺ transport and electron transfer during charge/discharge cycles, thereby delivering the Ni₃Sn₂S₂@NC composite with good specific capacity (∼667.7 mAh/g at 0.1 A/g) and ultralong cycling stability at high rates (∼170.6 mAh/g under 2.0 A/g after 2000 cycles). When assembled with perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as the cathode in PTCDA||KFSI-DME||Ni₃Sn₂S₂@NC, the device achieves a high energy density of ∼226 Wh/kg with stable cycling performance. This work introduces a valuable perspective for the kinetic engineering of high-rate electrodes through intrinsic electronic structure modulation.