Cascading Boost Effect on the Capacity of Nitrogen-Doped Graphene Sheets for Li- and Na-Ion Batteries

Abstract

Specific capacity and cyclic performance are critically important for the electrode materials of rechargeable batteries. Herein, a capacity boost effect of Li- and Na-ion batteries was presented and clarified by nitrogen-doped graphene sheets. The reversible capacities progressively increased from 637.4 to 1050.4 mAh g (164.8% increase) in Li-ion cell tests from 20 to 185 cycles, and from 187.3 to 247.5 mAh g (132.1% increase) in Na-ion cell tests from 50 to 500 cycles. The mechanism of the capacity boost is proposed as an electrochemical induced cascading evolution of graphitic N to pyridinic and/or pyrrolic N, during which only these graphitic N adjacent pyridinic or pyrrolic structures can be taken precedence. The original and new generated pyridinic and pyrrolic N have strengthened binding energies to Li/Na atoms, thus increased the Li/Na coverage and delivered a progressive capacity boost with cycles until the entire favorable graphitic N transform into pyridinic and pyrrolic N.

Construction of robust coupling interface between MoS2 and nitrogen doped graphene for high performance sodium ion batteries

“…After 140 cycles, the MoS 2 @NG composite still remains a discharge capacity of 630 mA h g −1 , the corresponding Coulombic efficiency is ~97.0%. As amounts of defect sites and vacancies in N-doped graphene can facilitate the insertion/extraction of Na + during the cycles [49] . Whereas, the discharge capacities for MoS 2 @G, MoS 2 and pure graphene electrodes are 490, 76 and 82 mA h g −1 after 140 cycles, respectively.…”

Tailoring Highly N‐Doped Carbon Materials from Hexamine‐Based MOFs: Superior Performance and New Insight into the Roles of N Configurations in Na‐Ion Storage

“…Due the lower N‐5 content, it is very difficult to distinguish its sodiation process, but it can be deduced that sodiation of N‐5 is similar to that of N‐6 because of their close adsorption energies ( E ad ) for Na ions . At 0.01 V, sodiation of all of the N configurations was complete, and the binding energies ( E b ) of N‐6, N‐5, N‐Q, and N‐O negatively shifted from the original values of 398.8, 400.3, 401.3, and 403.5 eV to 398.3, 399.4, 400.3, and 402.7 eV, respectively, implying that charge was transferred from Na to the N‐dopants to form Na‐protonated N structures in the carbon matrix . Therefore, sodiation of the N configurations is a gradual process, and the voltage required to complete sodiation of each N configuration decreased in the order N‐6 ≈ N‐5 > N‐Q > N‐O, which is also consistent with the order of their E b values.…”

Synthesis of Hierarchically Porous Nitrogen‐Doped Carbon for Sodium‐Ion Batteries

“…Binary and ternary heteroatoms co‐doped carbon materials have also been synthesized through the thermolysis of carbon precursors . To date, nitrogen doping is the most widely investigated in carbonaceous materials since nitrogen, acting as an electron donor, can increase the electronegativity and accelerate the charge transfer …”