Freestanding film made by necklace-like N-doped hollow carbon with hierarchical pores for high-performance potassium-ion storage

Author(s): Wenxiu Yang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Jinhui Zhou ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Shuo Wang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Weiyu Zhang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Zichen Wang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Fan Lv ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Kai Wang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Qiang Sun ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Shaojun Guo ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵

Publication date (Electronic): 2019

Journal: Energy & Environmental Science

Publisher: Royal Society of Chemistry (RSC)

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Abstract

Necklace-like N-doped hollow carbon with hierarchical pores was utilized as a free-standing high-performance potassium-ion storage anode.

Abstract

Potassium-ion batteries (PIBs) have drawn much attention as a replacement for lithium-ion batteries (LIBs) owing to their low cost and high safety. However, it is still an open challenge to design stable and high-capacity nanocarbon for efficient intercalation/deintercalation of large K ions. Herein, we report a class of ultra-high pyrrolic/pyridinic-N-doped necklace-like hollow carbon (NHC) material as a novel free-standing anode for enhancing PIBs in terms of their capacity, rate ability and durability. The as-made NHC film features abundant hierarchical micro/meso/macro-pores, a necklace-like hollow structure, ultra-high pyrrolic/pyridinic-N doping and a high specific surface area, which could finally promote the intercalation/deintercalation of K ions, reduce the volume expansion and improve the stability of PIBs. These new characteristics allow the NHC to deliver a high reversible specific capacity of 293.5 mA h g ⁻¹ at 100 mA g ⁻¹, outstanding rate property (204.8 mA h g ⁻¹ at 2000 mA g ⁻¹) and cycling performance (161.3 mA h g ⁻¹ at 1000 mA g ⁻¹ after 1600 cycles), which represent the best performance for carbon-based non-metal materials for PIB anode. Density functional theory (DFT) calculations demonstrate that pyrrolic and pyridinic-N doping can efficiently change the charge density distribution of carbon and promote the adsorption of K ⁺ on the NHC electrode, which promotes K ion storage.

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High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance.

Veronica Augustyn, Jeremy Come, Michael A. Lowe … (2013)

Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2·xH2O in an acidic electrolyte. However, we recently demonstrated that a pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1,2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 μm thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices.