Nitrogen-Doped Porous Ag–C@Co₃O₄ Nanocomposite for Boosting Lithium Ion Batteries

Abstract

In this work, nitrogen-doped Ag-based metal–organic gels (Ag-MOGs) are introduced for the first time in the field of lithium ion batteries (LIBs) with good electrochemical performances. As a novel approach of the nitrogen-doping method for LIBs, Ag–carbon (Ag–C) as the precursor is formed from Ag-MOGs and Co3O4 nanoparticles are prepared by different pyrolysis processes and maintain different particle sizes as the primary active materials. Co3O4 nanoparticles with smaller sizes (10–15 nm) covering the surface of Ag–C show good electrochemical performance because of the good conductivity of silver particles and the nitrogen doping of Ag–C. In particular, the composite shows a high rate capability of 516.4 mAh g–1 (5 A g–1) and strong cycling stability of 1275.78 mAh g–1 at the current density of 100 mA g–1 even after 100 cycles.

Designing Ag@NiO as Air Electrode Catalysts with Synergistic Interface and Doping Engineering Strategies for High-Performance Lithium–Oxygen Batteries

“…41,42 This is attributed to the introduction of Ag nanoparticles on the surface of NiO, which facilitates the generation of an enormous surface area and a great ratio of surface/volume; hence, the synergistic interface and doped Ag of the 10%Ag@NiO catalyst can supply more active sites and shorten lithium-ion diffusion distances, leading to low-concentration polarization during the mass transfer procedure. 43 Therefore, the above results further confirm that 10%Ag@NiO shows a better electrocatalytic activity and the introduction of Ag + ions causes charge regulation in order to produce highly active sites, which is conducive to the fast carrier transfer for the OER and ORR to facilitate the formation and decomposition of Li 2 O 2 . 29 In addition, to further evaluate the electrochemical performances of Ag@NiO as a cathode catalyst, we carry out the constant current charge and discharge examination in Li−O 2 batteries with the cutoff voltage range of 2.0−4.5 V. As displayed in Figure 5a, the primary discharge capacity of the air electrode is tested in Li−O 2 batteries at a current density of 0.1 mA/cm 2 until the deadline voltage of 2.0 V. Obviously, the 10%Ag@NiO air electrode shows smallest charged and discharged overvoltage compared with others.…”

“…Besides these, the influence of concentration polarization on the whole electrode reaction kinetics is evaluated by means of the following formula: Z normalf = R normalc normalt + σ ′ ω − 1 / 2 ( 1 − j ) Z f , R ct , σ′, and ω, respectively, represent Faradaic impedance, charge transfer resistance, Warburg coefficient values, and frequency. It shows that the turning-point frequency of 10% Ag@NiO is the largest (3.79 Hz), indicating that the mass transfer process has a lower impact on electrode kinetics and the concentration polarization is the lowest. , This is attributed to the introduction of Ag nanoparticles on the surface of NiO, which facilitates the generation of an enormous surface area and a great ratio of surface/volume; hence, the synergistic interface and doped Ag of the 10%Ag@NiO catalyst can supply more active sites and shorten lithium-ion diffusion distances, leading to low-concentration polarization during the mass transfer procedure . Therefore, the above results further confirm that 10%Ag@NiO shows a better electrocatalytic activity and the introduction of Ag + ions causes charge regulation in order to produce highly active sites, which is conducive to the fast carrier transfer for the OER and ORR to facilitate the formation and decomposition of Li 2 O 2 …”

Graphene Oxide-Wrapped Porous Hollow Co3O4 Microspheres with Enhanced Lithium Storage Performance

“…Figure a displays the CV curves of the first cycle, the second cycle, and the third cycle of PHCo 3 O 4 /GO microspheres at 0.5 mV s –1 between 0.0 and 3.0 V. The peaks around 0.56 and 1.12 V correspond to the multistep electrochemical reduction reaction between Co 3 O 4 and Co and the formation of amorphous Li 2 O and SEI film during the first cathodic scan process . The peak around 2.20 V could be ascribed to the oxidation reaction between Co and Co 3 O 4 and the decomposition of amorphous Li 2 O during the first anodic scan process. − The CV curve of the second cycle almost coincided with that of the third cycle, exhibiting the high electrochemical reversibility and long cycling stability of PHCo 3 O 4 /GO microspheres. Figure b presents the CV curves of PHCo 3 O 4 /GO microspheres at different sweep rates.…”

Synthesis of Co3O4/VG/CNT Composite Microspheres with Excellent Lithium Storage Performance

“…The rate capability curves of porous Co 3 O 4 microspheres, Co 3 O 4 /VG/CNT composite microspheres, and dense Co 3 O 4 microspheres are shown in Figure c. Due to electrode polarization, the charge/discharge specific capacity decreased with the increase of current density. − Co 3 O 4 /VG/CNT composite microspheres showed the highest charge/discharge specific capacity at different current densities among the prepared three microspheres; the capacity difference increased with the increase of current density, and the reversible specific capacity difference between Co 3 O 4 /VG/CNT and dense Co 3 O 4 microspheres was as high as 365 mA h g –1 at 1000 mA g –1 . The average reversible specific capacities of Co 3 O 4 /VG/CNT composite microspheres were 1170, 972, 766, and 526 mA h g –1 at 100, 300, 500, and 1000 mA g –1 , respectively, and the high reversible specific capacity of 1103 mA h g –1 was achieved when the current density was recovered to 100 mA g –1 .…”