Abstract:Pseudo-capacitive mechanisms can provide higher energy densities than electrical double-layer capacitors while being faster than bulk storage mechanisms. Usually, they suffer from low intrinsic electronic and ion conductivities of the active materials. Here, taking advantage of the combination of TiS2 decoration, sulfur doping, and a nanometer-sized structure, as-spun TiO2/C nanofiber composites are developed that enable rapid transport of sodium ions and electrons, and exhibit enhanced pseudo-capacitively dom… Show more
“…Since the CV analysis and power‐law plots (Figure 7) implied that storage process is mainly governed by the pseudocapacitive process with some degree of the diffusion‐controlled Faradaic mechanism, CV profiles were thoroughly analyzed to demonstrate the quantitative contribution ratio between the two mechanisms, as shown in Figure 10 [63–66] . The results revealed that the pseudocapacitive ratio of CON‐G‐10 gradually increased from 46.0 to 72.7 % with varying the scan rate from 0.1 to 0.8 mV s −1 .…”
To investigate the effect of electrical conductivity on the energy‐storage characteristics of anode materials in sodium‐ion batteries, covalent organic nanosheets (CONs) are hybridized with highly conductive graphene nanosheets (GNs) via two different optimized synthesis routes, that is, reflux and solvothermal methods. The reflux‐synthesized hybrid shows a well‐overlapped 2D structure, whereas the solvothermally prepared hybrid forms a segregated phase in which the contact area between the CONs and GNs is reduced. These two hybrids synthesized by facile methods are fully characterized, and the results reveal that their energy‐storage properties can be significantly improved by enhancing the electrical conductivity via the formation of a well‐overlapped structure between CONs and GNs. The discharge capacity and rate capability of the reflux‐synthesized hybrid was considerably larger than that of the bare CONs, highlighting that the improvement in the charge‐carrier transport properties can improve the accessibility of Na ions to the surface of the hybrids. This synthetic methodology can be extended to the fabrication of high‐performance anodes for Na‐ion batteries.
“…Since the CV analysis and power‐law plots (Figure 7) implied that storage process is mainly governed by the pseudocapacitive process with some degree of the diffusion‐controlled Faradaic mechanism, CV profiles were thoroughly analyzed to demonstrate the quantitative contribution ratio between the two mechanisms, as shown in Figure 10 [63–66] . The results revealed that the pseudocapacitive ratio of CON‐G‐10 gradually increased from 46.0 to 72.7 % with varying the scan rate from 0.1 to 0.8 mV s −1 .…”
To investigate the effect of electrical conductivity on the energy‐storage characteristics of anode materials in sodium‐ion batteries, covalent organic nanosheets (CONs) are hybridized with highly conductive graphene nanosheets (GNs) via two different optimized synthesis routes, that is, reflux and solvothermal methods. The reflux‐synthesized hybrid shows a well‐overlapped 2D structure, whereas the solvothermally prepared hybrid forms a segregated phase in which the contact area between the CONs and GNs is reduced. These two hybrids synthesized by facile methods are fully characterized, and the results reveal that their energy‐storage properties can be significantly improved by enhancing the electrical conductivity via the formation of a well‐overlapped structure between CONs and GNs. The discharge capacity and rate capability of the reflux‐synthesized hybrid was considerably larger than that of the bare CONs, highlighting that the improvement in the charge‐carrier transport properties can improve the accessibility of Na ions to the surface of the hybrids. This synthetic methodology can be extended to the fabrication of high‐performance anodes for Na‐ion batteries.
“…As a result, compared with 1.53 for MNC, a higher slope value (2.04) for GCNT@ST-MNC implies more efficient Li + diffusion, agreeing with excellent rate capability. In addition, Li + intercalation kinetics can be analyzed by plotting log I p vs. log v (obeying the relationship with I p = a · v b ), where b = 0.5 or 1.0, implying a semi-infinite diffusion or capacitive process, respectively [ 55 ]. For GCNT@ST-MNC, b is found to be 0.91 (close to 1) and higher than 0.82 of MNC, suggesting a faster Li + insertion process with a typical capacitive behavior, (Fig.…”
Section: Resultsmentioning
confidence: 99%
“…5 f). These results indicate that the dominant capacitive storage mechanism endows GCNT@ST-MNC cathode with outstanding reaction kinetics [ 55 ]. Fig.…”
Lithium- and manganese-rich (LMR) layered cathode materials hold the great promise in designing the next-generation high energy density lithium ion batteries. However, due to the severe surface phase transformation and structure collapse, stabilizing LMR to suppress capacity fade has been a critical challenge. Here, a bifunctional strategy that integrates the advantages of surface modification and structural design is proposed to address the above issues. A model compound Li1.2Mn0.54Ni0.13Co0.13O2 (MNC) with semi-hollow microsphere structure is synthesized, of which the surface is modified by surface-treated layer and graphene/carbon nanotube dual layers. The unique structure design enabled high tap density (2.1 g cm−3) and bidirectional ion diffusion pathways. The dual surface coatings covalent bonded with MNC via C-O-M linkage greatly improves charge transfer efficiency and mitigates electrode degradation. Owing to the synergistic effect, the obtained MNC cathode is highly conformal with durable structure integrity, exhibiting high volumetric energy density (2234 Wh L−1) and predominant capacitive behavior. The assembled full cell, with nanographite as the anode, reveals an energy density of 526.5 Wh kg−1, good rate performance (70.3% retention at 20 C) and long cycle life (1000 cycles). The strategy presented in this work may shed light on designing other high-performance energy devices.
“…The relationship of the scan rates and current responses is described by the followed formulas: , In formula , a b -value of 1 indicates the reaction is a totally surface-dominated, referring to the surface faradaic pseudocapacitive and nonfaradaic double-layer reactions (capacitive behavior). A b -value of 0.5 shows a reaction controlled by semi-infinite diffusion, referring to the faradaic redox reaction from Li + intercalation/deintercalation (diffusion behavior) . In most instances, the b -value is between 0.5 and 1, which indicates the current responses are both controlled by diffusion and capacitive behavior .…”
With the battery-type anode and capacitor-type cathode, lithium-ion capacitors (LICs) are expected to exhibit both high energy and high power density but suffer from the mismatch of the electrode reaction kinetics and capacity. Herein, to alleviate the mismatch between the two electrodes and synergistically enhance the energy/power density, we design a method of microwave irradiation reduction to prepare graphene-based electrode material (MRPG/CNT) with fast ion/electron pathway. The threedimensional structure of CNT intercalation to graphene inhibits the restacking of graphene sheets and improves the conductivity of the electrode material, resulting a rapid ion and electron diffusion channel. Due to its specific properties, MRPG/CNT materials can be used as both anode and cathode electrodes of LICs at the same time. As anode, MRPG/CNT shows a high capacity of 1200 mAh g −1 as well as high rate performance. As cathode, MRPG/CNT displays a high capacity of 108 mAh g −1 and the capacity retention of 100% after 8000 cycles. Coupling the prelithiated MRPG/CNT anode with MRPG/CNT cathode gives a full-graphene-based symmetric LIC, which achieves a high energy density of 232.6 Wh kg −1 at 226.0 W kg −1 , 111.2 Wh kg −1 at the ultrahigh power density of 45.2 kW kg −1 , and superior capacity retention of 86% after 5000 cycles. The structure design of this electrode provides a new strategy for alleviating the mismatch of LIC electrodes and constructing high-performance symmetrical LICs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
