Capacity Retention Rate Research Articles

Promoting Cathodic Kinetics and Anodic Stability in Practical Room-Temperature Sodium-Sulfur Batteries with Bifunctional Electrolytes.

The development of room-temperature (RT) sodium-sulfur (Na-S) batteries is severely hindered due to the slow kinetics of the S cathode and the instability of the Na-metal anode. To overcome this, we introduced a dual-functional electrolyte cosolvent, trifluoromethanesulfonamide (TFMSA). Short-chain Na2Sx (1 ≤ x ≤ 2) can be effectively dissolved due to the strong H-S bond interaction between TFMSA and sulfides, which changes the S conversion process, thereby effectively enhancing the conversion kinetics of the cathode. Meanwhile, TFMSA can generate a stable solid electrolyte interphase on the Na-metal surface to protect it from soluble polysulfide attack. Therefore, the RT Na-S batteries using the ether electrolyte show a high initial discharge capacity of 896.6 mAh g-1 and a capacity retention rate of 73% after 150 cycles at 0.2C, and the pouch cell also demonstrates its practical performance. This work proposes a dual-functional electrolyte cosolvent selection principle to inspire the practical application of high-performance RT Na-S batteries.

Flexible screen-printed supercapacitors with asymmetric PANI/CDC–AC electrodes and aqueous electrolyte

Abstract We report the fabrication and electrical performance of screen-printed flexible supercapacitors based on activated carbon (AC) and polyaniline (PANI)/carbide-derived carbon (CDC) composite electrodes, and neutral aqueous electrolytes. The devices are entirely constructed from safe, low-cost, and non-toxic materials, fabricated through a mass production capable screen printing process, and fully disposable with normal household waste. Symmetric and asymmetric cells with a thin planar face-to-face structure were fabricated on polyethylene terephthalate (PET) substrate, using eco-friendly chitosan binder based electrode inks, and printed graphite current collectors. The asymmetric cell configuration, with a PANI/CDC positive electrode and an AC negative electrode, demonstrated significantly improved electrochemical performance, through increased operating voltage, energy density and power density, improved cyclic stability and rate capability, and decreased equivalent series resistance (ESR) and leakage current, compared to previously reported symmetric PANI/CDC supercapacitors. The fabricated asymmetric devices had an average capacitance of 250–270 mF, ESR of 20–23 Ω, and leakage current of 140–150 µA, depending on the PANI/CDC variant used. Energy densities of 4.8 Wh kg-1 and 4.9 Wh kg-1, power densities of 1.6 kW kg-1 and 1.5 kW kg-1, and capacitance retention rates of 93 % and 97 % after 2,000 charge-discharge cycles, were achieved with PANI/CDC (10:1) and (30:1) variants, respectively.

Surface Reconstruction Enhanced Li-Rich Cathode Materials for Durable Lithium-Ion Batteries.

Regulating the distribution of surface elements in lithium-rich cathode materials can effectively change the electrochemical performance of cathode materials. Considering that the enrichment of Mn element on the surface is the main reason for the irreversible phase transition and dissolution of its surface structure, which in turn is the main reason for performance degradation. Based on the molten salt-assisted sintering method, a lithium rich cathode material with surface rich Ni and Co is designed and prepared. The surface enrichment of Ni and Co effectively reduces the dissolution of Mn, promotes the occurrence of irreversible collapse of surface structure from layered phase to rock salt phase on the material surface, improves the stability of surface crystal phase structure, and improves the cycling stability of positive electrode materials. Notably, after 500 cycles at 1 C current density, the discharge-specific capacity attained 189.8 mAh g -1, with a capacity retention rate of 88.9%, indicating a 42.1% improvement in capacity retention. Molten salt treatment is widely used in the modification of positive electrode materials. The research work will provide new ideas for improving the stability of lithium rich materials and promoting their commercial applications.

Interface reinforced by polymer binder for expandable carbon fiber structural lithium-ion battery composites

Carbon fiber (CF) composite structural battery (SB) is a novel energy storage device that integrates electrochemical energy storage with mechanical load-bearing capability. Carbon fiber's inherent conjugated carbon network possesses excellent electronic conductivity, thus serving as a current collector for electrode active materials. The bonding between active materials and carbon fibers relies on their manufacturing processes, requiring optimization of their electrochemical performance and addressing the challenges of large-scale production. In this work, a LiFePO4/PEO-LiTFSI/CF composite cathode was fabricated using the direct coating method. Polyethylene oxide (PEO) acted as a binder to form a stable LiFePO4 (LFP) coating on the carbon fiber woven fabric, while multi-walled carbon nanotube (MWCNT) were employed to construct a conductive network. This significantly enhanced both the charge-discharge performance and interface stability of the composite cathode. This composite cathode achieved a first-cycle discharge-specific capacity of 133.21 mAh·g−1 at 0.1 C rate and retained 93.7 % of its capacity after 200 cycles at 1 C rate. Based on this composite cathode, multiple active material coatings were integrated onto a carbon fiber woven fabric to manufacture an expandable multi-cell structural battery. Its advantage lies in the ability of multiple battery cells to disperse stress under load, thus achieving a higher capacity retention rate under bending loads. The structural battery possesses a high degree of customizability, allowing for adjustment of the area, position, and quantity of active material coatings to meet the demands of practical conditions.

Self-supported NiCo2O4@Ni1.18S core-shell nanocomposite with impressive electrochemical properties suitable for hybrid supercapacitors

Self-supported NiCo2O4@Ni1.18S core-shell nanocomposite were synthesized on nickel foams by uniform growth Ni1.18S nanosheets encircling NiCo2O4 nanoneedles. Characterization results demonstrate that NiCo2O4@Ni1.18S core-shell nanocomposite have significant advantages in one - and two-dimensional nanostructure coordination structure, with richer REDOX active sites and more energy storage paths. Density functional theory (DFT) calculations results indicate that the surficial adsorption energy with OH− ions is enhanced in NiCo2O4@ Ni1.18S nanocomposite, thereby facilitating the reversible redox reaction kinetics and the electrochemical activity. As a result, self-supported NiCo2O4@Ni1.18S core-shell nanocomposite exhibit excellent energy-storage properties, i.e.: the specific charge capacity of 3158 F g−1 at 1 A g−1, high rate performance of 52.3 % from 1 A g−1 to 5 A g−1, and the 81.25 % capacity retention rate after 5000 cycles. Especially, it should be pointed out that the hybrid supercapacitors assembled from self-supported NiCo2O4@Ni1.18S core-shell nanocomposite and activated carbon present the wide voltage window (0–1.6 V), high energy density of 100.3 Wh kg−1 at power density of 177 W kg−1 and prospective commercial consideration. These facts fully prove the practical feasibility of self-supported NiCo2O4@Ni1.18S core-shell nanocomposite in advanced energy-storage facilities.

Self-Templating Synthesis of Mesoporous Carbon Cathode Materials for High-Performance Lithium-Ion Capacitors.

Lithium-ion capacitors (LICs) have attracted considerable interest because of their excellent power and energy densities. However, the development of LICs is limited by the low capacity of the cathode and the kinetics mismatch between the cathode and anode. In this work, mesoporous carbon materials (MCs) with uniform pore sizes were prepared using magnesium citrate as the raw material through a self-templating method. During the carbonization process, MgO nanoparticles generated from magnesium citrate act as a template, resulting in a more orderly pore structure. The resultant MCs demonstrate a high specific surface area of 1673 m2 g-1 and an abundance of small mesopores, which significantly accelerated ion migration within the electrolyte and expedited the formation of electric double layers. Benefiting from these advantages, the MCs cathode demonstrates a high reversible specific capacity, excellent cycling stability, and rate performance. The assembled MCs-based LIC provides a high energy density of 152.2 Wh kg-1 and a high power density of 14.3 kW kg-1. After 5000 cycles, a capacity retention rate of 80% at the current density of 1 A g-1 is obtained. These results highlight the excellent potential of MCs as a cathode material for LICs.

Hierarchical porous self-supporting graphite carbon electrodes based on the biomimetic structure for supercapacitors

Regulating pore structure, improving conductivity, and reducing the influence of binders are considered important ways to improve the performance of carbon-based electrode materials for supercapacitors. This study successfully prepares a highly graphitized hierarchical porous self-supporting carbon electrode without the need for binders, conductive agents, and current collectors using low-cost and abundant pine wood as the precursor and K2FeO4 as the activator and catalyst. The self-supporting electrode inherits the biological structure of biomass and forms a large number of micro mesopores through activation, showing an excellent 3D interconnected pore structure, and achieves a high degree of graphitization with the ID/IG ratio of being only 0.47. The self-supporting electrode facilitates the effective transport of electrolyte ions and electrons, demonstrating excellent electrochemical performance. It achieves an area specific capacitance of 3.64 F cm−2 under a current density of 5 mA cm−2. Two identical self-supporting electrodes are employed to construct a symmetric supercapacitor. The supercapacitor exhibits an energy density of 148.61 μWh cm−2 at a power density of 1 mW cm−2, with a capacity retention rate of 89.26 % after 10,000 charge-discharge cycles.

WO2–N co-doped 2D Carbon nanosheets as multifunctional additives for enhancing the electrochemical hydrogen storage performance of Co2B

Co2B, with its high theoretical hydrogen storage capacity, is a potential solid-state hydrogen storage material. However, its poor cycling life limits its practical application. In this work, in order to improve the cycling stability and reversibility of hydrogen absorption and desorption of Co2B, we propose to use WO2–N–C nanosheets as dopants to mix with Co2B, thereby enhancing its practical performance. Two-dimensional tungsten oxide-nitrogen-carbon (WO2–N–C) nanosheets was syntheized via a liquid-phase approach, using a tungstenate-polydopamine precursor followed by thermal treatment. Subsequently, these WO2–N–C nanosheets were compounded with cobalt boride (Co2B) particles through ball milling at various ratios of 1%, 3%, and 5%, which were confirmed by XRD (X-ray diffraction) and SEM (Scanning Electron Microscope) methods. Employing a comprehensive suite of electrochemical analyses, including corrosion potential measurements, polarization curves, step voltammetry, and electrochemical impedance spectroscopy (EIS), we found that the incorporation of WO2–N–C significantly enhances the corrosion resistance and electrochemical activity of Co2B. Furthermore, cyclic life tests revealed that the WO2–N–C-doped Co2B composites exhibit superior discharge capacities and capacity retention rates compared to pristine Co2B. Notably, the 3% WO2–N–C-doped Co2B composite demonstrated the optimal electrochemical performance, achieving a maximum discharge specific capacity of 555 mAh g−1 and maintaining 82% of its initial capacity after 50 cycles. Our findings underscore the dual role of WO2–N–C in not only augmenting the surface electrochemical activity of Co2B but also providing a protective surface layer, thereby enhancing its overall electrochemical performance.

Modulating the lattice structure via Cr3+ doping in LiFe0.4Mn0.6PO4 cathode for improved rate behavior and promoted cyclic performance

Although LiFe0.4Mn0.6PO4 cathode shows high potential in battery industry, the cyclic performance and rate behavior are still the concerns to overcome. In this paper, Cr3+ doping in the cathode is confirmed very effective to improve both the performance via increased Li migration kinetics and suppressed lattice expansion during the redox process. It is found from the XRD refinement that Li − O bond length is increased upon Cr3+ intercalation, which in turn leads to the decrease in migration energy barrier (from 48.41 KJ·mol−1 to 19.57 KJ·mol−1) and the increase in Li diffusion coefficient. GITT investigation reveals a big promotion of DLi from 7.38 × 10−11 cm2·s−1 to 4.47 × 10−10 cm2·s−1, which is regarded as the reason for the excellent rate capacity of 126.62 mAh·g−1 (80.8 % of the value at 0.1C) at 5C current density. Further study with ex-situ XRD investigation reveals that the lattice expansion during redox process is suppressed after Cr3+ doping due to the smaller radius and stronger bond energy of the substituted cations. The suppressed volume change decreases both the internal resistance and the polarization of the electrode, which therefore leads to an improved capacity retention. The initial discharge specific capacity of LFMP-2%Cr cathode material reaches 156.8 mAh·g−1 at 0.1C, and the capacity retention rate of the material is maintained as 98.4 % after 100 cycles at 0.5C. The above results reveal the effectiveness of Cr3+ in promoting the electrochemical performance and further confirm the Cr- doped LFMP cathode high potential in future application.

Enhancing electric field intensity of interfacial electric double layer to improve properties of solid electrolyte interface for sodium-ion batteries

The electrical double layer (EDL) provides a critical area, where the specific adsorption on the electrode dominates the initial structure and chemical composition of the solid electrolyte interface (SEI) film. Therefore, the SEI can be optimized by adjusting the properties of the EDL. Here, we regulate the properties of EDL to optimize the composition and morphology of the SEI film on the hard carbon anode surface by adding NaF with small molecule structure. The preferential accumulation of NaF additives on the electrode surface enhances the electric field intensity and promotes electrolyte decomposition. That is, the formed SEI film rich in inorganic NaF and B-O components, can significantly improve the storage capacity of sodium ions in the hard carbon anode and accelerate the rapid transport of sodium ions. This strategy enables the cycling capacity to improve by 13.5 %, and maintain a stable capacity retention rate of 86.2 % at the rate of 1C after 500 cycles, thereby extending the lifespan and increasing the capacity of the rechargeable battery. The strategy that utilizing small molecule additives to enhance the electric field intensity of EDL provides a new approach to improve the performances of SEI film and battery performances.

Interface stabilization strategy realizing low-temperature sodium storage in Sb anode prepared by ball milling method

Antimony (Sb) is an attractive anode material for sodium-ion batteries (SIBs) owing to its low operating potential, low cost, and high theoretical capacity. However, the large volume expansion of Sb during the Na alloying/dealloying process, which greatly limits its application in SIBs. Simultaneously, as the temperature decreases, the formation of a poor coating on the anode surface significantly increase the difficulty of Na+ transmission. Herein, Sb-graphite-NaF (SCF) ternary composites were prepared by an easy to operate and low-cost ball milling method, which significantly improved the cycling stability and extended to the operation temperature of Sb-base SIBs. A small amount of NaF induces the formation of an inorganic-dominated NaF-rich stable solid electrolyte interphase (SEI) on the Sb anode surface, which can cooperate with graphite to inhibit volume expansion of the Sb particles during sodium storage, enhance conductivity and accelerate Na+ diffusion at room and low temperatures. As a result, the SCF electrode with propylene carbonate-base electrolyte delivered a discharge capacity of 458.4 mAh g−1 after 160 cycles at 500 mA g−1 at 20 °C. When matched with diethylcarbonate-based electrolyte at −20 °C, it had a specific capacity of 299.8 mAh g−1 after 120 cycles and a capacity retention rate of 86.2 %. This study shows that the interface stabilization strategy with a suitable electrolyte can improve the cycling stability of anode materials, provide a new idea for constructing NaF-rich SEI, and a new approach for applying Sb-based materials in low-temperature SIBs.

Recycling of Spent Graphite from Lithium-Ion Batteries for Aqueous Zn Dual-Ion Batteries.

As lithium-ion batteries (LIBs) become more widespread, the number of spent LIBs gradually increases. Until now, recycling of spent LIBs has mainly concentrated on high-value cathodes, but the anode graphite has not yet attracted wide attention. In this work, spent graphite from LIBs was oxidized to graphene oxide and then thermally reduced to reduced graphene oxide (RGO), which serves as the cathode of aqueous Zn dual-ion batteries (ZDIBs). The thermal reduction process enables RGO with a large layer spacing and porous structure, which increase the anion insertion sites and transfer kinetics. As a result, the corresponding battery exhibits a high specific capacity of 96.82 mAh g-1 at 1 A g-1, superior rate capability, and a high capacity retention rate of 80% after 2000 cycles. Moreover, RGO gradually transforms into a long-range disordered structure during the cycling process, which provides more transport routes and active sites for anion insertion and thus leads to the increase of capacity. This work combines the recycling of spent graphite with aqueous ZDIBs, realizing the high-value use of spent graphite.

A Novel 4-Fluorophenyl Isocyanate Additive Constructing Solid Cathodes-Electrolyte Interface for High-Performance Lithium-Ion Batteries.

Building a stable cathode-electrolyte interface (CEI) is crucial for achieving high-performance layered metal oxide cathode materials LiNixCoyMn1-x-yO2 (NCM). In this work, a novel 4-fluorobenzene isocyanate (4-FBC) electrolyte additive that contains isocyanate and benzene ring functional groups is proposed, which can form robust and homogeneous N-rich and benzene ring skeleton CEI film on the cathode surface, leading to significant improvement in the electrochemical performance of lithium-ion batteries. Taking LiNi0.5Co0.2Mn0.3O2 (NCM523) as an example, the NCM523/SiO@Graphite pouch full cells with electrolytes containing a mass fraction of 1% 4-FBC additives demonstrate improved capacity retention after 200 cycles, retaining capacity retention rates of 81.3%, which is much higher than that of 39.1% without additive. The improvement can be ascribed to the mitigation of electrolyte decomposition and inhibition of transition metal ions the dissolution from the cathode material due to the stable CEI film. Moreover, the electrochemical performance enhancement can also be achieved in high voltage and Ni-rich cathode materials, indicating the universality and effectiveness of this strategy for the practical applications of high energy density lithium-ion batteries.

Synergistic Enhancement of Biaxial Stretching and Multilayer Composites in All-Solid-State Polymer Electrolytes.

As an important component of lithium-ion batteries, all-solid-state electrolytes should possess high ionic conductivity, excellent flexibility, and relatively high mechanical strength. All-solid-state polymer electrolytes (ASSPEs) based on polymers seem to be able to meet these requirements. However, pure ASSPEs have relatively low ionic conductivity, and the addition of inorganic fillers such as lithium salts will reduce their flexibility and mechanical strength. To address the above issues, in this paper, the solvent-free method was used to prepare a poly(vinylidenefluoride-co-hexafluoropropylene)/lithium bis(trifluoromethanesulfonyl) imide/poly(ethylene oxide) all-solid-state polymer electrolyte, which was then subjected to 4 × 4 magnification synchronous bidirectional stretching. Subsequently, it was multilayered with PEO-based composite polymer electrolytes to obtain multilayered composite polymer electrolytes (MCPEs). Bidirectional stretching provides superior in-plane and out-of-plane mechanical properties to MCPEs by inducing molecular chain orientation, which suppresses the growth of lithium dendrites. Concurrently, it facilitates the formation of the β-crystal form of PVDF-HFP, thereby weakening the ion solvation effect and reducing the lithium-ion migration energy barrier. Multilayered compounding improves the interfacial contact between MCPEs and electrodes, thereby reducing the interfacial impedance. Experiments have demonstrated that the MCPEs prepared in this paper exhibit high ionic conductivity at room temperature (1.83 × 10-4 S cm-1), low interfacial resistance (547 Ω cm-2), excellent mechanical properties (26 MPa), and excellent cycling rate performance (a capacity retention rate of 90% after 110 cycles at 0.1 C), which can meet the performance requirements of lithium-ion batteries for ASSPEs.

Superior initiator reactivity and electrochemical properties of In(OTf)3 over Sn(OTf)2 for 1,3-dioxolane based solid polymer electrolyte

The in-situ polymerization of 1,3-dioxolane (PDOL) in battery cells has attracted extensive attention, however, the differences of Lewis acid initiators on the DOL monomer conversion (C%) and electrochemical properties has been ignored. Here, it is demonstrated that compare with Sn(OTf)2 Lewis acid initiator, the gelation of DOL is achieved at the lower addition of In(OTf)3. By optimizing their content in the gelation process, their C% are comparable which are 95.7 % and 93.5 % for In(OTf)3 and Sn(OTf)2, respectively. However, the higher ionic conductivity (7.1 × 10−4 S cm−1 at room temperature), electrochemical window (~4.5 V) and Li+ transference number (0.42) are obtained for DOL initiated with In(OTf)3, due to its lower molecular weight which is helpful to the intermolecular Li+ transport along PDOL main chain; In addition, the Li/Li symmetrical cell of In(OTf)3 can be stably cycled for >500 h at 3 mA cm−2, with an over-potential of 178mv. The storage and cycling impedances of half cells further proves the stable interface of In(OTf)3 initiated DOL toward to lithium metal in comparison with those of Sn(OTf)2. Scanning electron microscopy results show a denser and thinner interface in the DOL catalyzed by In(OTf)3. Finally, the assembled Li/LiFePO4 battery delivers specific discharge capacity and capacity retention rates of 115.5mAh g−1 and 85 %, respectively after 300 cycles at 1C. Through the initiator selection, the DOL synthesis and electrochemical properties can be tuned, which further broadens the design idea of PDOL based solid polymer electrolyte.

High capacity amorphous GeO2/C composite anodes for improved long cycle stability of lithium-ion batteries

Although GeO2 has a high theoretical capacity, its poor cyclic stability limits its application. In this work, amorphous GeO2/C composite anode materials were prepared by hydrothermal and sintering methods to improve the long-term cycle stability of Ge based anodes. The reversible specific capacity of the anode was 1300 mAh g−1 after 200 stable cycles at a current density of 0.2 A g−1, and it was 1002 mAh g−1 after 1000 long cycles at a high current density of 1 A g−1. The capacity retention rates of the amorphous GeO2/C-24 composite electrode were 84 % for the 2nd to the 200th discharge, being significantly higher than that of the commercial GeO2 electrode (10 %). C doping changed the structure of GeO2 atomic bonds and made C and O combine preferentially, resulting in Li+ intercalating to the GeO2/C interface and the increase in the number of lithiation reaction sites, Li+ diffusion coefficient, lithium-storage capacity and electrode capacity. The volume expansion rate of GeO2 was reduced from 12.84 % to 2.51 % by C doping, resulting in the high structure stability of the anode in long cycles for LIBs. The reason was the stress release effect of the amorphous C coating, and the formation of a stable and appropriate thickness of the SEI film.

Weakening the Space Charge Layer Effect Through Tethered Anion Electrolyte and Piezoelectric Effect Toward Ultra-Stable Zinc Anode.

The space charge layer (SCL) dilemma, caused by mobile anion concentration gradient and the rapid consumption of cations, is the fundamental reason for the generation of zinc dendrites, especially under high-rate discharge conditions. To address the issue, a physical (PbTiO3)/chemical (AMPS-Zn) barrier is designed to construct stable zinc ion flow and disrupt the gradient of anion concentration by coupling the ferroelectric effect with tethered anion electrolyte. The ferroelectric materials PbTiO3 with extreme-high piezoelectric constant can spontaneously generate an internal electric field to accelerate the movement of zinc ions, and the polyanionic polymer AMPS-Zn can repel mobile anions and disrupt the anions concentration gradient by tethering anions. Through numerical simulations and analyses, it is discovered that a high Zn2+ transference number can effectively weaken the SCL, thus suppressing the occurrence of zinc dendrites and parasitic side reactions. Consequently, an asymmetric cell using the PbTiO3@Zn demonstrates a reversible plating/stripping performance for 2900h, and an asymmetric cell reaches a state-of-the-art runtime of 3450h with a high average Coulombic efficiency of 99.98%. Furthermore, the PbTiO3@Zn/I2 battery demonstrated an impressive capacity retention rate of 84.0% over 65000 cycles by employing a slender Zn anode.

The enhanced properties of ZnCoNi-S electrode by magnetron sputtering of Au nanoparticles for high performance supercapacitors

In this work, the distinctive effect of Au nanoparticles on shape preservation and properties enhancement during the preparation of transition metal sulfides is explored for the first time. After zeolitic imidazolate framework-67 (ZIF-67) is uniformly covered on nickel foam (NF), ZnCo layered double hydroxides (ZnCo-LDH) are compounded with ZIF-67 via hydrothermal method. The surface of compound is then coated with Au by magnetron sputtering. The final electrode is produced through sulfidation reaction. Benefiting from the excellent inertness and electrical conductivity of Au, the flake structure remains stable during the following sulfidation, and transfer impedance of the obtained Au/ZnS@Co3S4@Ni3S2 (Au/ZCN-S) electrode decreases significantly. In contrast, magnetron sputtered Ag or Cu nanoparticles react to Ag2S or CuS2 and cannot protect the refined structure of electrode as Au does. The Au/ZCN-S electrode shows a low transfer impedance of 0.0785 Ω and enables a specific capacity of 302.6 mAh g−1. Furthermore, the asymmetric supercapacitor constructed by Au/ZCN-S and activated carbon (AC) achieves a remarkable energy density of 104.09 Wh kg−1 with a high capacitance retention rate of 91.184 % after 10000 cycles. This work provides a new approach to optimize the morphology and performance of transition metal sulfides electrode for supercapacitors.

Quantum-Sized Co Nanoparticles with Rich Vacancies Enabled the Uniform Deposition of Lithium Metal and Fast Polysulfide Conversion.

The notorious polysulfide shuttling and uncontrollable Li-dendrite growth are the main obstacles to the marketization of Li-S batteries. Herein, a dual-functional material consisting of vacancy-rich quantum-sized Co nanodots anchored on a mesoporous carbon layer (v-Co/meso-C) is proposed. This material exposes more active sites to improve its reaction performance and simultaneously realizes excellent lithiophilicity and sulfiphilicity characteristics in Li-S electrochemistry. As Li metal deposition hosts, v-Co/meso-C shows small nucleation overpotential, low polarization, and ultra-long cycling stability in both half and symmetric cells, as confirmed by experimental studies. On the S cathode side, experimental and theoretical calculations demonstrate that v-Co/meso-C enhances the adsorption of polysulfides and boosts their catalytic conversion rate. This, in turn, suppresses the shuttle effect of polysulfides and improves sulfur utilization efficiency. Finally, a shuttle-free and dendrite-free v-Co/meso-C@Li//v-Co/meso-C@S full cell is fabricated, exhibiting excellent rate performance (739 mAhg-1 at 5.0 C) and good cyclability (capacity decay rate is 0.033% and 0.035% per cycle at 2.0 and 5.0 C, respectively). Even a pouch cell with high sulfur loading (5.5mgcm-2) and lean electrolyte/sulfur (4.8µLmg-1) can still work 50 cycles with 80% capacity retention rate. This study shows far-reaching implications in the design of dendrite-free, shuttle-free Li-S batteries.

SrCoO3-based perovskites with enhanced electrochemical performance through structural tailoring induced by B-site substitution

The progression of supercapacitor technology hinges on the discovery of high-performance electrode materials to enhance energy storage. SrCoO3-δ perovskite holds considerable promise potential as an anion intercalation electrode material. To elucidate the structural and electrochemical performance modulation rules of SrCoO3-based perovskites, this study synthesized SrCo0.875M0.125O3-δ (M = Ti, Ta, Nb, Fe) perovskites with different B-site ion substitutions. The structural tailoring induced by B-site substitution were thoroughly investigated alongside their corresponding electrochemical performance. Notably, SrCo0.875Ti0.125O3-δ exhibited a simple cubic structure, while the other samples displayed a tetragonal structure. Additionally, SrCo0.875Fe0.125O3-δ displayed numerous oxygen vacancies and significant distortion in the [CoO6] octahedron, which is attributed to the lower valence state of Fe. At a current density of 1 A g−1, the specific capacities of SrCo0.875M0.125O3-δ (M = Nb, Ti, Fe, Ta) perovskites were 984.43, 853.33, 503.53, and 452.00C/g, respectively. SrCo0.875Nb0.125O3-δ demonstrated the highest specific capacity and capacity retention rate across various current density, owing to its relatively stable structure with appropriate oxygen vacancies and multivalent state changes of Nb. In contrast, SrCo0.875Fe0.125O3-δ, with excessive oxygen vacancies and severe structural distortions, exhibited restricted electrochemical performance, particularly at higher current densities. Integrating structural and performance analysis, this work proposes an optimization strategy for the electrochemical performance of SrCoO3-δ-based perovskite electrode materials, emphasizing the importance of tailoring multivalent B-site elements to achieve a stable perovskite structure with appropriate oxygen vacancies.