Although K
is readily inserted into graphite, the volume expansion of graphite of up to 60% upon the formation of KC
, together with its slow diffusion kinetics, prevent graphite from being used as ...an anode for potassium-ion batteries (PIBs). Soft carbon with low crystallinity and an incompact carbon structure can overcome these shortcomings of graphite. Here, ultra-thin two-dimensional (2D) wrinkled soft carbon sheets (USCs) are demonstrated to have high specific capacity, excellent rate capability, and outstanding reversibility. The wrinkles themselves prevent the dense stacking of micron-sized sheets and provide sufficient space to accommodate the volume change of USCs during the insertion/extraction of K
. The ultra-thin property reduces strain during the formation of K-C compounds, and further maintains structural stability. The wrinkles and heteroatoms also introduce abundant edge defects that can provide more active sites and shorten the K
migration distance, improving reaction kinetics. The optimized USC
electrode exhibits a reversible capacity of 151 mAh g
even at 6400 mA g
, and excellent cyclic stability up to 2500 cycles at 1000 mA g
. Such comprehensive electrochemical performance will accelerate the adoption of PIBs in electrical energy applications.
Numerous studies have reported that the enhancement of rate capability of carbonaceous anode by heteroatom doping is due to the increased diffusion‐controlled capacity induced by expanding interlayer ...spacing. However, percentage of diffusion‐controlled capacity is less than 30% as scan rate is larger than 1 mV s−1, suggesting there is inaccuracy in recognizing principle of improving rate capability of carbonaceous anode. In this paper, it is found that the heteroatom doping has little impact on interlayer spacing of carbon in bulk phase, meaning that diffusion‐controlled capacity is hard to be enhanced by doping. After synergizing with tensile stress, however, the interlayer spacing in subsurface region is obviously expanded to 0.40 nm, which will increase the thickness of accessible subsurface region at high current density. So SRNDC‐700 electrodes display a high specific capacity of 160.6 and 69.5 mAh g−1 at 20 and 50 A g−1, respectively. Additionally, the high reversibility of carbon structure insures ultralong cycling stability and hence attenuation of SRNDC‐700 is only 0.0025% per cycle even at 10 A g−1 for 6000 cycles. This report sheds new insight into mechanism of improving electrochemical performance of carbonaceous anode by doping and provides a novel design concept for doping carbon.
Heteroatom doping affects the interlayer spacing of the subsurface region much more than the bulk for carbonaceous nanoparticles. The increased accessible subsurface boosts the pseudocapacitive capacity and endows SRNDC‐700 with excellent rate performance up to 50 A g−1. This varies from diffusion‐controlled capacity determinism and provides a novel design concept for doping carbonaceous material.
Poly{tris4-(2-thienyl)phenylamine} (PTPATTh) and polytris(4-carbazoyl-9-yl phenyl)amine (PTPATCz) are thiophene-based and carbazole-based conjugated microporous polymers with triphenylamine as cores. ...Here we present detailed evidence of highly efficient and iodine capture in both CMPs. Thanks to the propeller-like structure, high porosity, extended π-conjugation and electron-rich characteristics, the both CMPs display efficient, adsorption of I2 in vapor (up to 3.13 and 2.56 g g−1) and in solution. Two ways to release the adsorbed iodine were explored: either slow release into ethanol or quick release upon heating (with a high degree of control). In addition, the both CMPs could be recycled while maintaining 70% iodine uptake capacity (up to 85%). Thus making the resulting CMPs ideal absorbent materials for iodine capture to address environmental issues.
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•We investigated the iodine adsorption performance of PTPATTh and PTPATCz.•The PTPATTh shows lower specific surface area (SBET = 594 m2 g−1) than PTPATCz (SBET = 894 m2 g−1) does.•The PTPATTh (3.13 g g−1) shows higher adsorptivity than PTPATCz (2.56 g g−1).•The phenyl ring, N and S heteroatoms and charge-transfer interactions are the effective sorption sites to iodine.
Synergistic effect of soft carbon and hard carbon has been proven to be useful for obtaining excellent anode materials for potassium ion battery, which is determined by the mixing degree of ...precursors. Inspired by the formation of proteins in biology, peptide bonds are used to connect the precursors of the two sort of carbon to prepare soft–hard hybrid carbons with stronger synergistic effects. The hard carbon domain with nanometer size is so highly distributed in the soft carbon that the synergistic effect between two sorts of carbon is significantly enhanced. After the optimization, the diffusion coefficient of as-prepared hybrid carbon (CSHC3–6-1200) is 10 times larger than that of corresponding carbon synthesized by physical method. Consequently, CSHC3–6-1200 can maintain a specific capacity of 71.6 mAh g–1 at a high current density of 1600 mA g–1. It is believed that this new preparation route may bring a new perspective to the development of soft and hard composite carbon material anodes with high power density and ultralong service life.
Synergistic effects between hard carbons and soft carbons are proven to be helpful for improving the electrochemical performance of carbonaceous anode for potassium-ion batteries (PIBs). However, the ...phase separation of precursors limits the synergistic effects and improvement of electrochemical performance. Here, inspired by the esterification reaction, the precursors of two sorts of carbon are connected at the molecular level, which boosts the synergistic effects in hybrid carbon, resulting in excellent electrochemical kinetics and low charge/discharge voltage. Consequently, the hybrid carbon anode exhibited a high specific capacity of 121 mAh·g
−1
at 3.2 A·g
−1
, a high-rate capability, and stable cycling performance. After 500 cycles at 1 A·g
−1
, the average capacity fading is only 0.078% per cycle.
Micro/nano lab‐on‐chip power systems with poor energy storage/conversion ability are one of the major obstacles that circumvent the further practical applications of the micro/nano smart devices. In ...this work, the multilayer Si/TiN/Sb nanorod (NR) arrays composites anodes are successfully fabricated and impressively display improved electrochemical properties in 3D Si‐based lithium/sodium ion microbatteries (L/SIMBs). Both the 3D Si configuration and the efficient TiN interlayer are together responsible for the obtained enhanced cyclability of the Sb nanoelectrode. Moreover, the Li/Na ion storage behaviors are also experimentally investigated from the postmorphology characterizations and further evidences the structure stability of the whole Si/TiN/Sb NRs anodes during the repeated Li/Na ions inserting/de‐inserting process. These multilayer Si/Ti/Sb NR arrays composites should be a promising anode for the 3D Si‐based L/SIMBs.
Multilayer Si/TiN/Sb nanorod arrays composites anodes are successfully fabricated using the semiconductor micromachining technology. The introduction of the efficient TiN interlayer combined with the patterned Si substrate and the Sb active material impressively display superior electrochemical performance when applied in 3D Si‐based lithium/sodium ion microbatteries.
Graphite anode for potassium-ion batteries suffers poor rate capability because of the sluggish diffusion kinetics of K+. According to the rate law of chemical reactions, enrichment of K+ on the ...outer layer of graphite anode is expected to improve the rate capability. However, the surface of graphite is too smooth to adsorb adequate K+ to enhance rate capability. Herein, MoS2 is coated on exfoliated graphite to enrich the concentration of K+ on the surface of EG by forming K2S in high-voltage region, leading to an extremely high diffusion coefficient of up to 1000 times than that of bare graphite at the bottleneck stage, which accelerates the reaction rate of electrochemical intercalation process. Consequently, the EG/MoS2 electrode exhibits superior rate performances (125 mAh/g at 3.2 A/g), which is 11 times higher than that of EG. Moreover, the specific capacity of EG/MoS2 is 169 mAh/g at 1.6 A/g below 0.36 V, which is almost 25 times higher than that of bare EG (7 mAh/g). Our study provides new fundamental insights to boost power density of the anodes for PIBs without trading off energy density.
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•Concentration of K+ on the surface of EG/MoS2 is increased by 14 times compared by EG.•K+ Diffusion coefficient is enhanced up to 3 orders of magnitude at the bottleneck stage.•The design of EG/MoS2 anodes with both high energy density and power density.
Three dimensional (3D) multilayer Si/TiN/Sb nanorod (NR) arrays composites anodes are successfully fabricated by the semiconductor process technology, and impressively display improved ...electrochemical performance both in Si based lithium‐ion and sodium‐ion microbatteries. More details can be found in article number 2001043 by Chuang Yue, Fang Hu, and co‐workers.
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