Ultrahigh Specific Capacitance Research Articles

Construction of V2O5@MXene Cathodes toward a High Specific Capacity Aqueous Aluminum-Ion Battery.

Aqueous aluminum-ion batteries (AAIBs) are considered a strong candidate for the new generation of energy storage devices. The lack of suitable cathode materials has been a bottleneck factor hindering the future development of AAIBs. In this work, we design and construct a highly effective cathode with dual morphologies. Two-dimensional (2D) layered MXene materials possessed good conductivity and hydrophilicity, which are used as the substrates to deposit rod-shaped vanadium oxides (V2O5) to form a three-dimensional (3D) cathode. The cathode design provides a strong boost for the rapid electrochemical activities of rod-shaped V2O5 by embedding/extracting both protons (H+) and aluminum-ion (Al3+). As a result, the V2O5@MXene cathode based AAIB delivers an ultrahigh initial specific capacity of 626 mAh/g at 0.1 A/g with a stable cycle performance up to 100 cycles. This work is a breakthrough for the development of cathode materials for AAIBs.

Electrochemical Investigation of ZnS/NiO Nanocomposite based Symmetric Supercapattery

AbstractSupercapattery is an ideal energy storage device combining the features of supercapacitors and batteries, offers a high‐energy density as well as high‐power density with extended operational lifespan. In this work, zinc sulfide (ZnS) and zinc sulfide/nickel oxide (ZnS/NiO) nanocomposite was synthesized via chemical coprecipitation method and characterized using state‐of‐the‐art analytical tools. The ZnS/NiO electrode exhibited remarkable electrochemical performance as an electrode material than pure ZnS. The ZnS/NiO nanocomposite exhibited high crystallinity, and spherical nanoparticles with an average grain size of 20–40 nm having a homogeneous dispersion. The ZnS/NiO electrode exhibited an ultrahigh specific capacity of 1803.87 Cg−1 at a relatively low scan rate of 10 mVs−1 in a 1 M KOH solution from cyclic voltammetry and 393 Cg−1 at 16 Ag−1 from charge discharge measurements, and it showed exceptional cycling stability (98 % capacity retention after 1000 cycles). Furthermore, the ZnS/NiO symmetric supercapattery device exhibited 44.43 Fg−1 specific capacitance, 5.52 Wh kg−1 energy density, and 1600 Wkg−1 power density at current density of 0.8 Ag−1 in 1 M KOH solution from galvanostatic charge discharge. After 3000 cycles, the ZnS/NiO nanomaterial demonstrated promising cyclic stability of 95 %. The ZnS/NiO supercapattery nanocomposite might be considered as a potential hybrid electrode material for the future development of electrochemical energy storage devices.

Unraveling the multilayer solid-electrolyte interphase in lithium batteries through depth-sensitive plasmon-enhanced Raman spectroscopy: A theoretical and experimental study

The solid-electrolyte interphase (SEI) plays a crucial role in determining the lithium deposition/dissolution behaviors, thus influencing the reversible operation of Li metal batteries renowned for their ultrahigh specific capacity. Recently, we developed depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method enabling the in situ and nondestructive characterization of the nanostructure and chemistry of SEI through synergistic plasmonic structures. However, a lack of comprehensive elucidation of the enhancement mechanisms has impeded a detailed understanding of the depth-resolved signal contributions. In this study, we integrate theoretical computations with experimental methodologies to systematically unravel the working principles of the synergistic plasmonic structures, demonstrating that hot spots can effectively detect Raman signals at key locations across various stages of SEI layer evolution. Following Li deposition, the hot spots transfer from the Cu interfaces to the Li interfaces. With the thickening of the deposited Li, the localized surface plasmon resonance of Cu is gradually shielded, leading to the disappearance of hot spots originated from Li-Li coupling. Subsequently, we propose the utilization of Cu@Li-multilayer shell-isolated nanoparticles to compensate and introduce new hot spots, thereby enhancing the depth sensitivity. Our work provides theoretical insights essential for achieving precise depth-resolved PERS characterization.

Enabling stable high lithium storage of Si anode via synergistic effects of nanosized Fe3C and partially graphitized porous carbon

Si is considered as a promising anode for high-energy lithium-ion batteries (LIBs) because of its ultrahigh theoretical specific capacity and desired working potential. However, the main problems of Si as an anode are still faced with low conductivity and inevitable structure damage caused by large volume change during cycle. Although design of Si/C composites effectively mitigates the above problems, their preparation usually involves complex methods. This work demonstrates a very simple ball milling and subsequent carbonization approach for the preparation of high-performance Si NPs@Fe3C@PC anode, which integrates partially hollow Fe3C nanoparticles (Fe3C) and partially graphitized porous carbon (PC) into Si nanoparticles (Si NPs)-based composite. It is found that Fe3C with catalysis is favorable not only to formation of a graphitized porous carbon during material preparation but also to formation of a stable solid electrolyte interfaces (SEI) on electrode surface during cycle. With Fe3C, the Si NPs@Fe3C@PC shows smaller Li+ adsorption energy, lower activation energy, higher electric conductivity, larger Li+ diffusion coefficient and a thinner SEI film than Si NPs and Si NPs@PC counterparts. The findings verify that the synergistic effects of the Fe3C and PC provide fast kinetics, high capacitive contribution, improved structure stability and a stable LiF-rich SEI film for Si NPs@Fe3C@PC during cycle. Therefore, Si NPs@Fe3C@PC shows excellent electrochemical performance, gaining 1786, 1211.4 and 411.5 mAh/g after 210, 650 and 840 cycles at 100, 1000 and 5000 mA g−1, respectively. Finally, this contribution proposes a simple and effective strategy for improving Si NPs performance and hence obtaining a high-performance of Si-based anode for LIBs.

Constructing a Cr-Substituted Co-Free Li-Rich Ternary Cathode with a Spinel-Layered Biphase Interface.

Lithium-rich manganese-based layered oxides (LRMOs) have recently attracted enormous attention on account of their remarkably big capacity and high working voltage. However, some inevitable inherent drawbacks impede their wide-scale commercial application. Herein, a kind of Cr-containing Co-free LRMO with a topical spinel phase (Li1.2Mn0.54Ni0.13Cr0.13O2) has been put forward. It has been found that the high valence of Cr6+ can reduce the Li+ ion content and induce the formation of a local spinel phase by combining more Li+ ions, which is beneficial to eliminate the phase boundary between the spinel phase and the bulk phase of the LRMO material, thus dramatically avoiding phase separation during the cycling process. In addition, the introduction of Cr can also expand the layer spacing and construct a stronger Cr-O bond compared with Mn-O, which enables to combine the transition metal (TM) slab to prevent the migration of TM ions and the transformation of the bulk phase to the spinel phase. Simultaneously, the synergistic effect of the successfully constructed spinel-layered biphase interface and the strong Cr-O bond can effectively impede the escape of lattice oxygen during the initial activation process of Li2MnO3 and provide the fast diffusion path for Li+ ion transmission, thus further reinforcing the configurable stability. Besides, Cr-LRMO presents an ultrahigh first discharge specific capacity of 310 mAh g-1, an initial Coulombic efficiency of as high as 92.09%, a good cycling stability (a capacity retention of 94.70% after 100 cycles at 1C), and a small voltage decay (3.655 mV per cycle), as well as a good rate capacity (up to 165.88 mAh g-1 at 5C).

Rational design of copper phosphate based polyanionic framework for high performance supercapacitor

The key to high-performing supercapacitors is their abundance, low cost, and ability to deliver high capacitance in a wide electrochemical window. A new class of phosphate-based polyanion material has been developed to deliver high capacitance via the effective utilization of their oxidation states. Cu3(PO4)2 was synthesized by the facile hydrothermal technique and delivers an ultra high specific capacitance of about 814 F/g with multiple discharge plateaus at a current density of 1 A/g within a voltage window ranging from 0.4 v to -1.2 V. This intriguing behavior is mainly due to the multi functional Cu while interacts with the electrolytic ions and also the inductive effect of a phosphate group (PO4)2− contributes to a high discharge voltage of -1.2 V during charging and discharging process. It shows exceptional cyclic stability of 100 % over 10,000 cycles without sacrificing its coulombic efficiency and it is pertinent the structural stability of the system. The symmetric device was fabricated and delivered power density and energy density of 4.5 kW/kg and 31.5 Wh/kg, and also maintained excellent cyclic stability at 92 % with high reversibility of charged ions. This offers new insights into the high potential of using polyanion-type compounds as high-capacity materials for advanced energy storage systems.

Natural bio-waste-derived 3D N/O self-doped heteroatom honeycomb-like porous carbon with tuned huge surface area for high-performance supercapacitor

Supercapacitor electrodes (SCs) of carbon-based materials with flexible structures and morphologies have demonstrated excellent electrical conductivity and chemical stability. Herein, a clean and cost-effective method for producing a 3D self-doped honeycomb-like carbonaceous material with KOH activation from bio-waste oyster shells (BWOSs) is described. A remarkable performance was achieved by the excellent hierarchical structured carbon (HSC-750), which has a large surface area and a reasonably high packing density. The enhanced BWOSs-derived HSC-750 shows an ultrahigh specific capacitance of 525 F/g at 0.5 A g−1 in 3 M KOH electrolyte, as well as high specific surface area (2377 m2 g−1), pore volume (1.35 cm3 g−1), nitrogen (4.70%), and oxygen (10.58%) doping contents. The SCs also exhibit exceptional cyclic stability, maintaining 98.5% of their capacitance after 10,000 charge/discharge cycles. The two-electrode approach provides a super high energy density of 28 Wh kg−1 at a power density of 250 W kg−1 in an alkaline solution, with remarkable cyclability after 10,000 cycles. The study demonstrates the innovative HSC synthesis from BWOSs precursor and cost-effective fabrication of 3D N/O self-doped heteroatom HSC for flexible energy storage.

A difunctional electrolyte boosting the electrochemical performance of the primary Li/CFx batteries

Lithium/carbon fluorides (Li/CFx) batteries have received widespread attention because of the advantages of high energy density, low environmental pollution, and low self-discharge. However, less attention has been paid to electrolytes which also significantly affect the electrochemical performance of Li/CFx batteries. Herein, we develop a novel electrolyte for Li/CFx batteries, a mixture of lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluoro(oxalate) borate (LiODFB) with different ratios dissolving in propylene carbonate (PC)/methyl butyrate (MB). Interestingly, the LiODFB not only boosts the specific capacity exceeding the theoretical value (865 mAh−1) by introducing extra capacity via its ring opening reaction with Li+ during the discharge process, but also enhances the discharge voltage and rate capability at varying temperature. As expected, the Li/CFx batteries with electrolyte of 1 M LiODFB in PC/MB delivers an ultrahigh specific capacity of 1169.84 mAh g−1 and energy density of 2646.93 Wh kg−1 at 30 °C and 10 mA g−1, and 966.9 mAh g−1 and 2232.8 Wh kg−1 at 70 ℃ and 500 mA g−1, respectively. These findings provide new ideas on designing Li/CFx batteries with high capacity and high energy density.

Diminishing Self-Discharge of High-Loading Li-S Batteries with Oxygen-Rich Biomass Carbon Interlayers.

Lithium-sulfur batteries (Li-S) have possessed gratifying development in the past decade due to their high theoretical energy density. However, the severe polysulfide shuttling provokes undesirable self-discharge effect, leading to low energy efficiency in Li-S batteries. Herein, an interlayer composed of oxygen-rich carbon nanosheets (OCN) derived from bagasse is elaborated to suppress the shuttle effect and reduce the resultant self-discharge effect. The OCN interlayer is able to physically block the shuttling behavior of polysulfides and its oxygen-rich functional groups can strongly interact with polysulfides via O-S bonds to chemically immobilize mobile polysulfides. The self-discharge test for seven days further shows that the self-discahrge rate is diminished by impressive 93 %. As a result, Li-S batteries with the OCN interlayer achieve an ultrahigh discharge specific capacity of 710 mAh g-1 at a high mass loading of 7.18 mg. The work provides a facile method for designing functional interlayers and opens a new avenue for realizing Li-S batteries with high energy efficiency.

High-performance lithium metal anode enhanced by multifunctional film of PAN@AgNWs with antimicrobial activity

Lithium metal is expected to be the perfect anode material for the next generation of rechargeable batteries owing to its ultra-high theoretical specific capacity, low density and the lowest redox potential. However, the practical application of lithium metal batteries faces serious challenges, including uneven lithium deposition, negative electrode volume expansion, and short circuits brought by dendritic protrusions. Although the 3D structure of silver nanowires is effective in inhibiting lithium dendrite growth and lithium metal volume expansion, it still suffers from lithium inhomogeneity caused by uneven distribution of silver nanowires and complicated preparation. Therefore, PAN@AgNWs collector was prepared by a simple suction filtration method, and uniform dispersion of silver nanowires and uniform deposition of lithium were achieved. Lithium nucleation overpotential and lithium dendrite formation can be effectively reduced by PAN@AgNWs hosts due to the reduction of local current density by 3D collectors and the improved lithiophilicity of silver nanowires. With low voltage hysteresis, the symmetric battery constructed with its composite anode may cycle steadily for 4500 h at 1 mA cm−2 and 1 mAh cm−2. At the same time, the Li-PAN@AgNWs||LFP full cell still possesses a reversible of 144.18 mAh g−1 after 500 cycles at 1C. Moreover, due to large specific surface area and high surface energy of 3D silver nanowires, it exhibits excellent antimicrobial properties, with an inactivation efficiency of 96.3 % after contacting with E. coli for 2.5 h. This work shows the possibility of using PAN@AgNWs in a large scale for LMBs, and paves the way for development of high-performance antimicrobial materials.

Insights into pseudocapacitive mechanism of aqueous ammonium-ion supercapacitors with exceptional energy density and cyclability

Aqueous ammonium-ion (NH4+) supercapacitors (AASCs) have recently garnered increased concerns but are consistently facing the challenge of lower energy density. Herein, a high-performance electrode (CuCo2S4@CP) with pseudocapacitive property has been synthesized and primordially applied to AASCs. The CuCo2S4@CP electrode has an ultrahigh specific capacity of 1512 C g−1 at 1 A g−1 and a distinguished cyclic stability of 87.74 % after 10,000 cycles. When the CuCo2S4@CP electrode is combined with the activated carbon (AC) negative electrode, the CuCo2S4@CP//AC device exhibits a high specific capacity of 547 C g−1 at 1 A g−1, excellent cycle stability (83.28 % at 10 A g−1), high energy density of 74.17 Wh kg−1, and excellent device consistency. In addition, the charge transfer mechanism of CuCo2S4@CP electrode in NH4+electrolyte has been elucidated. The CuCo2S4 surface density functional theory (DFT) elucidates that NH4+ has a minimal contribution to the surface, implying an insertion behavior of NH4+ within the CuCo2S4 lattice. Subsequent ex-situ characterization further confirms the energy storage process, revealing charge transfer to Co atoms following NH4+ insertion into CuCo2S4. The analysis of charge distribution illustrates an energy storage mechanism wherein the hydrogen bond formed between NH4+ and CuCo2S4 serves as the transport channel for charge transfer, facilitating the process of electrons from NH4+ to Co atoms. Therefore, the pseudocapacitive mechanism of CuCo2S4 with NH4+ provides a blueprint for sustainable energy storage with high energy density in aqueous electrolyte.

Microwave construction of the 3D porous interconnected structure of NiCoCr medium-entropy alloy with ultra-high specific capacity for supercapacitors and electrocatalysis

The effective design of bifunctional electrodes with unique morphology and remarkable electrochemical properties for energy conversion and storage devices is a promising but challenging endeavor. Herein, self-supporting NiCoCr medium-entropy alloy (MEA) with a hierarchical porous network structure was in situ synthesized on nickel foam (NiCoCr/NF) by a simple and rapid microwave route. The optimal NiCoCr/NF presented an ultra-high specific capacity of 3011.8 C g−1 (1 A g−1) and outstanding charge/discharge sustainability (83.4% retention at 10 A g−1 over 50,000 cycles) due to its multi-component synergistic effect and hierarchical porous structure. Meanwhile, subtle lattice distortions and electron density redistribution in the NiCoCr MEA tuned electronic structures, resulting in a low overpotential and Tafel slope. Aqueous and solid-state asymmetric supercapacitors were fabricated by using NiCoCr/NF as a cathode and Bi/NF as an anode. The aqueous supercapacitor displayed an exceptional energy density of 314.4 Wh kg−1 at a power density of 800 W kg−1 with 81.8% retention at 10 A g−1 over 20,000 cycles. This study provides a new strategy for the efficient synthesis of electrode materials with interconnected network structures and paves the way for the broader application based on medium-entropy and high-entropy materials as promising candidates for future energy storage devices.

Solvent-Controlled Synthesis of Zn–Co–S@Ni12P5 Arrays with Ultra-High Specific Capacitance for Hybrid Supercapacitor

Solvent-Controlled Synthesis of Zn–Co–S@Ni₁₂P₅ Arrays with Ultra-High Specific Capacitance for Hybrid Supercapacitor

One-Step Construction of Closed Pores Enabling High Plateau Capacity Hard Carbon Anodes for Sodium-Ion Batteries: Closed-Pore Formation and Energy Storage Mechanisms.

Closed pores play a crucial role in improving the low-voltage (<0.1 V) plateau capacity of hard carbon anodes for sodium-ion batteries (SIBs). However, the lack of simple and effective closed-pore construction strategies, as well as the unclear closed-pore formation mechanism, has severely hindered the development of high plateau capacity hard carbon anodes. Herein, we present an effective closed-pore construction strategy by one-step pyrolysis of zinc gluconate (ZG) and elucidate the corresponding mechanism of closed-pore formation. The closed-pore formation mechanism during the pyrolysis of ZG mainly involves (i) the precipitation of ZnO nanoparticles and the ZnO etching on carbon under 1100 °C to generate open pores of 0.45-4 nm and (ii) the development of graphitic domains and the shrinkage of the partial open pores at 1100-1500 °C to convert the open pores to closed pores. Benefiting from the considerable closed-pore content and suitable microstructure, the optimized hard carbon achieves an ultrahigh reversible specific capacity of 481.5 mA h g-1 and an extraordinary plateau capacity of 389 mA h g-1 for use as the anode of SIBs. Additionally, some in situ and ex situ characterizations demonstrate that the high-voltage slope capacity and the low-voltage plateau capacity stem from the adsorption of Na+ at the defect sites and Na-cluster formation in closed pores, respectively.

Cation-driven self-assembly of core–shell covalent organic frameworks@Ti3CN MXene nanospheres for high-performance aqueous zinc-ion hybrid supercapacitors

Rechargeable aqueous Zn-ion hybrid supercapacitors (ZISCs) with the superiorities of high theoretical capacity, low redox potential and aqueous electrolytes with superior ionic conductivity (∼1 S cm−1) are promising energy storage systems. However, a primary concern persists due to the absence of cathode materials with both high energy densities and satisfactory cycling stability for robust ZISCs. In this study, we design a spherical core–shell covalent organic frameworks@Ti3CN MXene (CM-P) cathode via a cation-driven electrostatic self-assembly strategy. The CM-P with the constructed heterostructures shows both well-organized pore channels and excellent intrinsic conductivity, facilitating fast accessibility to intrinsic redox-active sites (such as C = O and N), and promoting effective ion diffusion characterized by low energy barriers. Consequently, the CM-P cathodes demonstrate excellent electrochemical performance, featuring an ultrahigh specific capacity of 260 mAh/g at 0.1 A, a high-rate capability with 68 % retention at 1 A/g, and long-term cycling stability. First-principle calculations elucidate that the enhanced charge-storage mechanism relies on the heterostructures of CM-P, accelerating ion adsorption/diffusion and electron transfer. Furthermore, the assembled CM-P//Zn ZISCs devices show a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. This work provides an innovative approach to design COFs-based heterostructures for advanced ZISCs.

Realization of high-capacity coulombic efficiency in sodium alginate/carbon nanotube double network coated Si-anode for lithium-ion batteries

Silicon (Si) is considered as one of the most promising anodes for the next-generation lithium-ion batteries (LIBs) owing to its ultra-high specific capacity, low redox potential and the second abundance of elements in the earth's crust. However, drastic volume change will directly cause electrode pulverization, thus leading to low initial coulombic efficiency (ICE) and terrible cycling stability. In this work, a sodium alginate (SA)‑carbon nanotube (CNT) derived double carbon-coated Si composite (SA-CNT@Si) was prepared through freeze-drying technique followed by high-temperature carbonization, where SA was utilized to encase Si nanospheres, with CNT serving as the conductive framework that interconnects Si spheres. These composites exhibit improved electrical conductivity and stability throughout the charge and discharge cycles when employed as the anodes in LIBs, demonstrating superior electrochemical properties. The SA-CNT@Si electrode with a mass ratio of Si: SA: CNT = 5: 1: 0.75, achieved a first discharge specific capacity of 2200.8 mAh g−1 at a current density of 500 mA g−1 (with the initial three cycles at 100 mA g−1), along with an ICE of 86.2%. Even after 500 cycles, it maintained a capacity of 607 mAh g−1. This study presents a novel approach to designing Si-based anode materials characterized by both high electrical conductivity and structural stability.

Analysis of Pressure Characteristics of Ultra-High Specific Energy Lithium Metal Battery for Flying Electric Vehicles

The lithium metal battery is likely to become the main power source for the future development of flying electric vehicles for its ultra-high theoretical specific capacity. In an attempt to study macroscopic battery performance and microscopic lithium deposition under different pressure conditions, we first conduct a pressure cycling test proving that amplifying the initial preload can delay the battery failure stage, and the scanning electron microscope (SEM) shows that the pressure is effective in improving the electrode’s surface structure. Secondly, we analyze how differing pressure conditions affect the topography of lithium deposits by coupling the nonlinear phase-field model with the force model. The results show that the gradual increase in the external pressure is accompanied by a drop in the length of the dendrite and the migration curvature in the diaphragm, and the deposition morphology is gradually geared towards smooth and thick development, which can significantly reduce the specific surface area of lithium dendrite. However, as cyclic charging and discharging continue, the decrease in the electrolyte diffusion coefficient results in higher internal stress inside the battery, and thus the external pressure must be increased so as to achieve marked inhibitory effects on the growth of the lithium dendrite.

Lithiophilic ZnCu alloy sites on copper current collector for high performance Li metal anode

Lithium (Li) metal has been widely regarded as the optimal anode material for the high-energy density rechargeable batteries, due to its ultrahigh theoretical specific capacity and lowest electrochemical potential. However, the formation of Li dendrites presents a significant safety concern, which limits its practical application. In this paper, to address this issue, an efficient and cost-effective strategy was proposed to prepare a zinc-copper composite collector (ZCC) with outstanding electrochemical performance, which can effectively suppress the formation of lithium dendrites. The lithophilic surface with ZnCu alloy nanoparticles was achieved through physical vapor deposition followed by annealing treatment. The ZCC collector enables dendrite-free deposition of Li due to its negligible nucleation overpotential. Even at high area capacity of 3 mAh cm−2 at 1 mA cm−2 in half-cells, the ZCC exhibits exceptional cycling performance and high coulomb efficiency. Preloaded with Li, the composite electrode (Li/ZCC) delivers an enhanced lifespan with low overpotential evidently. Matched with LiFePO4 (LFP) cathode, LFP||Li/ZCC full cells reveal a superior cycling stability with enhanced capacity retention of 85 % (after 1000 cycles at 1 C) and 87 % (after 800 cycles at 3 C) respectively.

Dual-active centers of porous triazine frameworks for efficient Li storage

Integrating n-type and p-type redox-active centers into porous frameworks is an efficient approach to simultaneously mitigate the intrinsic problems of poor utility, low output voltage, and sluggish kinetics of organic electrodes for lithium ion batteries (LIBs). However, it is challenging to achieve an optimal utilization of the well-defined ordered porous structure and the multiple active centers due to the stacking structure of conventional covalent organic frameworks. Herein, we develop a post-modification approach to synthesize a bipolar pyrene-4,5,9,10-tetraone based porous covalent triazine frameworks (CTFs) for efficient dual-ion storage. The post-modification method successfully protects the active carbonyl groups under harsh conditions and effectively exposes the redox centers. The amorphous phase dominated CTFs enables excellent Li+ diffusion and high utilization of active sites, leading to ultrahigh specific capacity of 351 mAh/g at 0.2 A/g and impressive stability for 3000 cycles at 5.0 A/g. Moreover, the efficient dual-ion storage mechanism was confirmed by the in-depth investigation with ex situ FT-IR, and XPS study. Theoretical calculations also unveil the unique energy storage pathway using both p-doped and n-doped states for the intercalation of anions and cations. This work highlights the significance of the integrating strategy which allows the combination of dual-active-center with conjugated porous structure, broadening the avenues of organic electrode materials towards high-performance LIBs.

Cobalt vacancy boosting Co3-xO4@C with superior pseudocapacitive lithium storage

The Co3O4 as anode for lithium ion batteries (LIBs) suffers the sluggish electrode kinetics and severe capacity fade during the cycles. The defective engineering of Co3O4 with oxygen/cobalt defects is an effective strategy to optimize Co3O4 with enhanced electrochemical properties. Herein, a series of 3D inter-connected Co3-xO4@C-y nanostructures with abundant Co defects are synthesized through a hydrothermal approach with subsequent heating-controlled process. Benefiting from its rich surface cobalt-defective sites and the 3D interconnected frameworks, as well as its high surface area and residual carbon layer, the Co3-xO4@C-y synthesized at y = 400 °C as anode for LIBs displays superior pseudocapacitive lithium storage properties with an ultra-high reversible specific capacity of 1900.7 mAh g−1 at 0.2 A g−1, excellent rate capability (e.g., 1415.1 mAh g−1 at 10 A g−1) and ultra-long cycling stability (e.g., 1160.5 mAh g−1 at 15 A g−1 after 2000 cycles).