Accurate Control Multiple Active Sites of Carbonaceous Anode for High Performance Sodium Storage: Insights into Capacitive Contribution Mechanism

Abstract

Heteroatom doping is widely recognized as an appealing strategy to break the capacitance limitation of carbonaceous materials toward sodium storage. However, the concrete effects, especially for heteroatomic phase transformation, during the sodium storage reaction remain a confusing topic. Here, a novel hypercrosslinked polymerization approach is demonstrated to fabricate pyrrole/thiophene hypercrosslinked microporous copolymer and further give porous carbonaceous materials with accurately regulated N/S dual doping corresponding to starting feeding ratios. Significantly, the N doping contributes to the conductivity and surface wettability, while the S doping is bridged to build stable active sites, which can be electrochemically converted into mercaptan anions via faraday reaction and further enhancing reversible capacities. Meanwhile, the abundant S doping can also conduce to the expanded interlayer spacing to shorten the ions diffusion distance, thus optimizing the reaction kinetic. As a result, the N0.2S0.8‐micro‐dominant porous carbon delivers the highest reversible capacity of 521 mAh g−1 at 100 mA g−1 and excellent cyclic stability over 2000 cycles at 2000 mA g−1 with a capacity decay of 0.0145 mAh g−1 per cycle. This work is anticipated to provide an in‐depth understanding of capacitance contribution and illuminate the heteroatomic phase transformation during sodium storage reactions for doping carbonaceous anodes.

Increasing Accessible Subsurface to Improving Rate Capability and Cycling Stability of Sodium‐Ion Batteries

“…Various researches demonstrate that pseudocapacitive capacity depends on surface area and active sites on surface. [14,17,18] As we all know, anode material with high surface area could form much more solid-electrolyte interphase film in first cycle, resulting in a lower initial columbic efficiency (ICE). [8] Thus, to procure larger pseudocapacitive contribution, one should create as many active sites as possible without dramatically increasing surface area.…”

“…The two peaks located at 161.6 and 162.9 eV correspond to Na 2 S and Na 2 S 2 , respectively. [18,44] Moreover, the peaks above 165 eV contribute from sodium thiosulfate/sulfate complex formed by the disproportionation reaction in the organic electrolyte solution. [35] When recharge to 3.0 V, the major peaks of S 2p positively shift to 162.9 and 164.2 eV (Figure 7d), demonstrating the reconstruction of CS and SS covalent bonds.…”

“…[35] When recharge to 3.0 V, the major peaks of S 2p positively shift to 162.9 and 164.2 eV (Figure 7d), demonstrating the reconstruction of CS and SS covalent bonds. [18] It is worthy of stressing that the reconstruction of CS and SS plays a key role in ultralong cycling stability because the active sides on edge of carbon and expanded interlayer spacing are all induced by CSSC bonds.…”

From Micropores to Ultra-micropores inside Hard Carbon: Toward Enhanced Capacity in Room-/Low-Temperature Sodium-Ion Storage

“…These porous carbon materials deliver improved diffusion kinetics and a satisfying rate capability in SIBs, originating from the existence of the well-developed porosity [41][42][43]. However, their discharge/charge profiles are dominated by sloping curves, due to the capacitive ion adsorption/desorption on the surface sites of the micropores, where the bare Na + and solvated Na + co-exist [44,45]. It is found that the existing electrolyte has a significant influence on the ionic interaction inside the pore [46].…”

Multiple Active Sites Carbonaceous Anodes for Na+ Storage: Synthesis, Electrochemical Properties and Reaction Mechanism Analysis

“…[ 87,88 ] Additionally, the incorporation of S into carbon layers can also build stable active sites such as short/long chain sulfur (‐S X ‐), which can be easily oxidized into mercaptan anions and supply extrinsic Faradic pseudo‐capacitance. [ 89–91 ] Thus, S doping has drawn great attentions to achieve high performance Na storage. [ 92 ] For S dopant atoms in carbonaceous materials, three major configurations consist of C‐S X ‐C, C‐SO X ‐C ( X ≤ 4) and C‐SH.…”