This review elaborately summarizes the latest progress in all-pseudocapacitive asymmetric supercapacitors, including aqueous/nonaqueous faradaic electrode materials, the operating principles, system design/engineering, and rational optimization.

The development of advanced layered Ni-rich cathodes is essential for high-energy lithium-ion batteries (LIBs). However, the prevalent Ni-rich cathodes are still plagued by inherent issues of chemomechanical and thermal instabilities and limited cycle life. For this, here, we introduce an efficient approach combining single-crystalline (SC) design with in situ high-entropy (HE) doping to engineer an ultrahigh-Ni cobalt-free layered cathode of LiNi _0.88 Mn _0.03 Mg _0.02 Fe _0.02 Ti _0.02 Mo _0.02 Nb _0.01 O ₂ (denoted as HE-SC-N88). Thanks to the SC- and HE-doping merits, HE-SC-N88 is featured with a grain-boundary-free and stabilized structure with minimal lattice strain, preventing mechanical degradation, reducing surface parasitic reactions, and mitigating oxygen loss. Accordingly, our HE-SC-N88 cathode demonstrates exceptional electrochemical properties particularly with prolonged cycling stability under strenuous conditions in both half and full cells, and the delayed O loss–induced phase transitions upon heating. More meaningfully, our design of HE doping in redefining the ultrahigh-Ni Co-free SC cathodes will make a tremendous progress toward industrial application of next-generation LIBs.

Hollow mesoporous hetero-NiCo₂S₄/Co₉S₈ submicro-spindles were fabricated in high yield, and delivered excellent pseudocapacitance with high energy density and desirable cycling duration at high rates for advanced hybrid supercapacitors.

To obtain advanced carbon materials for next-generation electrochemical capacitors (ECs), it is critical to understand the synergetic effect of versatile carbon surface functionalities and the specific pore structure on their electrochemical performance. Herein, we developed a facile yet scalable fabrication of N- and O-enriched carbon with nanoscale to mesoscale porous structures from the disposable cashmere. The hierarchical cashmere-derived micro-/mesoporous carbon (CDMMC) was endowed with a desirable specific surface area (SSA, 1358 m² g⁻¹), hierarchical porosity with high microporosity of ∼45.5%, and high content of heteroatom functionalities (∼4 at% N and ∼15.5 at% O). Even better electrochemical capacitance of the resulting CDMMC was obtained in 1 M H₂SO₄, benefiting from the hierarchical micro-/mesoporosity, large effective SSA and remarkable heteroatom (N, O) doping effects, that is, the smart combination of double layer and Faradaic contributions, compared to that in KOH. Furthermore, larger energy density (∼17.9 Wh kg⁻¹) of the CDMMC-based symmetric device was obtained with organic electrolytes, compared to those with aqueous electrolytes.