Tailoring stress-relieved structure for ternary cobalt Phosphoselenide@N/P codoped carbon towards high-performance potassium-ion hybrid capacitors and potassium-ion batteries

The sluggish redox kinetics and severe volume changes of potassium-ion hosts are the challenging issues for potassium ion hybrid capacitors (PIHCs) and potassium-ion batteries (PIBs). Herein, a novel ternary cobalt phosphoselenide (CoPSe)@N/P co-doped carbon (NPC) composite with stress-relieved structure is introduced as anodes for PIHCs and PIBs. The ultrafine CoPSe nanocrystallites are embedded in the N and P codoped carbon matrix to form the spherical units. Then the resultant nano-balls are encapsulated in the tyre-like hollow framework to construct the ball-in-tyre (BIT) structure. Both dual carbon decorations and ultrafine crystals of BIT structure favor the fast electron/ion transports and significantly depress the internal stress. Meanwhile, the strong interfacial interaction between the ternary CoPSe crystal and N/P codopant carbon matrix favor the fast kinetics and high stability of the composite. For the first time, the CoPSe@NPC BIT composite is constructed via a facile bio-cooperated approach, where the local bio-combustion, in-situ phosphorization and selenization syn-chronize. Density function theory (DFT) result reveals the improved intrinsic conductivity, enhanced potassium adsorption and diffusion capabilities of the CoPSe@NPC heterostructure. Finite element simulations (FEA) suggest the depressed stress with uniform distributions internal the BIT structure during ion insertion/dein-sertion processes. Electrochemical results demonstrate the superior high-rate capability and excellent cycling stability of CoPSe@NPC BIT composite in potassium-ion systems. Moreover, the PIHCs and PIBs full cell are fabricated based on the CoPSe@NPC BIT anodes. They exhibit the high energy density, high power density and high durability over long-term cycles. More impressively, both devices exhibit good abuse tolerance under diverse outside deformations or in a wide temperature range, which enable them promising power sources for diverse applications.

Automated summary

In this study, a novel ternary cobalt phosphoselenide (CoPSe)@N/P co-doped carbon (NPC) composite with stress-relieved structure is introduced as anodes for potassium-ion hybrid capacitors (PIHCs) and potassium-ion batteries (PIBs). The composite exhibits dual carbon decorations and ultrafine crystals in a ball-in-tyre (BIT) structure, enabling fast electron/ion transports and depressed internal stress. The strong interfacial interaction between CoPSe crystal and N/P codopant carbon matrix enhances the kinetics and stability of the composite. Moreover, the CoPSe@NPC BIT composite shows improved intrinsic conductivity, enhanced potassium adsorption and diffusion capabilities, and demonstrates superior high-rate capability and excellent cycling stability in potassium-ion systems.