Enhanced Cycling Stability Research Articles

Unlocking the influence of pitch-based and acetylene-based carbon coating on the electrochemical performance of SiO anodes: bridging insights from half-cell to full-cell studies

Silicon monoxide (SiO) has garnered significant attention as a prominent candidate for high-energy-density lithium-ion batteries (LIBs) owing to its reduced volume expansion and enhanced cycling stability compared to pure silicon (Si). However, the effect of carbon layers derived from different carbon sources on the electrochemical performance of SiO in both half and full cells has not been comprehensively studied, and the industrial consensus regarding the selection of carbon sources for SiO remains elusive. Herein, a systematic comparative evaluation was conducted to analyze the physicochemical properties and electrochemical behaviors of SiO with two different carbon layers. Additionally, comprehensive assessments were carried out to investigate the electrochemical performance of SiO employing two distinct carbon coating methods in 6 Ah pouch full-cell configurations, where SiO coated acetylene-based carbon exhibits advantages in cycling stability and Li+ kinetic. In industrial SiO carbon coating processes, it is advisable to prioritize acetylene-derived carbon using chemical vapor deposition (CVD) characterized by a high degree of graphitization, enhanced electrical conductivity, and uniform surface coverage. The investigation rooted in electrochemical performance of different carbon layers on SiO in both half-cell and full-cell configurations, provides fundamental insights for the advancement of research in silicon-based anodes’ development.

Ultrafast Photoexcitation Induced Passivation for Quasi-2D Perovskite Photodetectors.

Quasi-2D perovskites exhibit great potential in photodetectors due to their exceptional optoelectronic responsivity and stability, compared to their 3D counterparts. However, the defects are detrimental to the responsivity, response speed, and stability of perovskite photodetectors. Herein, an ultrafast photoexcitation-induced passivation technique is proposed to synergistically reduce the dimensionality at the surface and induce oxygen doping in the bulk, via tuning the photoexcitation intensity. At the optimal photoexcitation level, the excited electrons and holes generate stretching force on the Pb─I bonds at the interlayered [PbI6]-, resulting in low dimensional perovskite formation, and the absorptive oxygen is combined with I vacancies at the same time. These two induced processes synergistically boost the carrier transport and interface contact performance. The most outstanding device exhibits a fast response speed with rise/decay time of 201/627ns, with a peak responsivity/detectivity of 163 mA W-1/4.52 × 1010 Jones at 325nm and the enhanced cycling stability. This work suggests the possibility of a new passivation technique for high performance 2D perovskite optoelectronics.

Development of a high-capacitance flexible supercapacitor with enhanced cycling stability based on nanotubular polyaniline-modified titanium sheet

Nanotubular polyaniline modified titanium (PANI/Ti) sheet was synthesized via one-step chemical polymerization of aniline on a Ti sheet. The structural and morphological investigations of the PANI/Ti sheet were performed using X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. These investigations revealed that a nanotubular PANI network with an average diameter of 37.5 nm was vertically aligned on the Ti sheet. Electrochemical properties of PANI/Ti were investigated via cyclic voltammetry, galvanostatic charging/discharging, and electrochemical impedance spectroscopy in a three-electrode system. The PANI/Ti sheet exhibited an exceptional specific capacitance (Csp) of 1174 mF/cm2 at 2 mA/cm2, which was significantly higher than that of the PANI/GC (199.53 mF/cm2) and the bare Ti sheet (0.87 mF/cm2). The prepared PANI/Ti sheet exhibited a power density of 21.99 mW/cm2 at an energy density of 3.05 mWh/cm2. Moreover, the electrode demonstrated outstanding cycle stability, maintaining 97.62% efficiency over 3000 cycles and exhibited impressive flexibility, with minimal performance degradation even when bent at angles up to 90°. Furthermore, PANI/Ti sheet significantly reduces the solution and charge transfer resistance compared to bare Ti sheet. So PANI-modified Ti sheet will be a good choice for the fabrication of new flexible energy storage as well as electronic devices in the future.

Quasi-Solid-State Electrolyte Induced by Metallic MoS2 for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are a promising high-energy-density technology for next-generation energy storage but suffer from an inadequate lifespan. The poor cycle life of Li-S batteries stems from their commonly adopted catholyte-mediated operating mechanism, where the shuttling of dissolved polysulfides results in active material loss on the sulfur cathode and surface corrosion on the lithium anode. Here, we report in situ formation of a quasi-solid-state electrolyte (QSSE) on the metallic 1T phase molybdenum disulfide (MoS2) host that extends the lifetime of Li-S batteries. We find that the metallic 1T phase MoS2 host is able to initiate the ring-opening polymerization of 1,3-dioxolane (DOL), forming an integrated QSSE inside batteries. Nuclear magnetic resonance analysis reveals that the QSSE consists of ∼13% liquid DOL in a solid polymer matrix. The QSSE efficiently mediates sulfur redox reactions through dissolution-conversion chemistry while simultaneously suppressing polysulfide shuttling. Therefore, while ensuring high sulfur utilization, it avoids degradation of both electrodes, as well as the concomitant electrolyte consumption, leading to enhanced cycling stability. Under a practical lean electrolyte condition (electrolyte-to-sulfur ratio = 2 μL mg-1), Li-S pouch cell batteries with the QSSE demonstrate a capacity retention of 80.7% after 200 cycles, much superior to conventional liquid electrolyte cells that fail within 70 cycles. The QSSE also enables Li-S pouch cell batteries to operate across a wider temperature range (5 to 45 °C), together with improved safety under mechanical damage.

Enhancing Cycle Stability via Discharge Voltage Regulation in Li–S Batteries: Impact of the Lower Cutoff Voltage on Electrochemical Stability

The lithium–sulfur (Li–S) battery emerges as a candidate for next-generation batteries owing to its superior energy density and cost-effectiveness. Despite these advantages, the longevity of Li–S batteries remains a complex challenge. The shuttle effect has been identified as a principal factor contributing to degradation, prompting extensive research aimed at mitigating its impact. Recent studies, however, have unveiled that the presence of Li2S exerts a significant influence on the kinetics and stability of the electrochemical reaction. Although lower cutoff voltage directly controls the formation of Li2S, its relationship between lower cut-off voltage and Li2S formation has not been investigated so far. In this study, we regulated the discharge voltage and revealed the relationship between lower cutoff voltage and electrochemical stability. A low lower cut-off voltage increased Li2S formation and the first discharge capacity but reduced Li2S transformation to sulfur, as confirmed by the high overpotential and low charge capacity. Furthermore, repeated cycles at a high discharge exhibited severe capacity loss and deteriorated Coulombic efficiency. By contrast, a high lower cut-off voltage cell exhibited enhanced capacity retention with a low overpotential owing to the inhibition of Li2S formation. Thus, this study provides insights into controlling Li2S formation, which is critical to stabilizing the electrochemical reaction and enhancing the cycle stability of Li–S batteries.

Stabilizing dual-cation liquid metal battery for large-scale energy storage: A comprehensive hybrid design approach

Liquid metal batteries (LMBs) hold immense promise for large-scale energy storage. However, normally LMBs are based on single type of cations (e.g., Ca2+, Li+, Na+), and as a result subject to inherent limitations associated with each type of single cation, such as the low energy density in Ca-based LMBs, the high energy cost in Li-based LMBs, and the short cycling lifespan in Na-based LMBs. Here we propose a dual-cation (Ca2+ and Li+) liquid metal battery, which allows access to, simultaneously, high energy density, prolonged cycling lifespan, reduced energy cost, and enhanced cycling stability. For this strategy to work, the main obstacle to overcome is the instability of the dual-cation system in electrochemical reactions. We have undertaken a hybrid design approach to resolve this issue, by integrating phase diagram design, first-principles calculations, and machine learning techniques. We discover that incorporating magnesium as an inert additive can effectively stabilize the cycling performance of dual-cation LMBs. Furthermore, our results reveal that specific ion ratios are required to release tailor dual-cation chemistry, to enable the designed multi-component alloy (Ca-Li-Mg in our case) electrode to function properly in LMBs. These findings are expected to have general implications for future developments of innovative LMBs with enhanced performance.

Regulating anionic redox reversibility in Li-rich layered cathodes via diffusion-induced entropy-assisted surface engineering

Cobalt-free lithium- and manganese-rich layered oxides (LMROs) are regarded as effective cathode materials for lithium storage due to their high capacity and cost-effectiveness. However, challenges with structural degradation, resulting in poor cyclability and rate performance, have hindered their widespread use. Essentially, rapid structural degradation arises from irreversible and complex redox reactions, triggering oxygen release, transition metal migration, and electrolyte decomposition. To tackle this issue, we propose an epitaxial entropy-assisted construction approach to develop a sturdy surface with adaptable composition, stabilising the surface crystal structure and preventing undesirable interface reactions. This distinct reconstructed surface comprises diverse heterogeneous elements and composite microstructures. The heteroatom-doped layer, with multi-doping sites like Li, O site, and tetrahedral positions, effectively manages the chemical environment and electronic structure of surface lattice oxygen. This epitaxial entropy stabilisation approach, stemming from multi-element synergy, effectively controls redox progress to limit oxygen release and curb transition metal migration, reducing structural decay. Additionally, the composite coated layer, containing oxygen defects and heterogeneous spinel phases, can hinder electrolyte corrosion and promote Li+ transport. Using these epitaxial entropy surface modifications, the LMRO cathode demonstrates regulated anionic redox reversibility and enhanced cycling stability across diverse operational conditions. This epitaxial entropy-assisted surface engineering offers a promising avenue for stabilising high-energy cathode materials.

Regulation of Zn2+ solvation shell by a novel N-methylacetamide based eutectic electrolyte toward high-performance zinc-ion batteries

Aqueous Zn-ion batteries (AZIBs) have been regarded as promising alternatives to Li-ion batteries due to their advantages, such as low cost, high safety, and environmental friendliness. However, AZIBs face significant challenges in limited stability and lifetime owing to zinc dendrite growth and serious side reactions caused by water molecules in the aqueous electrolyte during cycling. To address these issues, a new eutectic electrolyte based on Zn(ClO4)2·6H2O-N-methylacetamide (ZN) is proposed in this work. Compared with aqueous electrolyte, the ZN eutectic electrolyte containing organic N-methylacetamide could regulate the solvated structure of Zn2+, effectively suppressing zinc dendrite growth and side reactions. As a result, the Zn//NH4V4O10 full cell with the eutectic ZN-1-3 electrolyte demonstrates significantly enhanced cycling stability after 1000 cycles at 1 A g−1. Therefore, this study not only presents a new eutectic electrolyte for zinc-ion batteries but also provides a deep understanding of the influence of Zn2+ solvation structure on the cycle stability, contributing to the exploration of novel electrolytes for high-performance AZIBs.

Bark‐Inspired Functional‐Carbon/Potassium Composite Electrode with Fast Ion Transport Channels for Dendrite‐Free Potassium Metal Batteries

AbstractPotassium metal batteries (PMBs) are regarded as viable candidates for future electrochemical energy storage devices with potential high energy density and low cost. However, uncontrollable potassium dendrite growth and huge volume expansion severely inhibit the practical application of PMBs. Herein, inspired by the structure and functionalities of tree bark, an antimony (Sb) nano‐clusters decorated N‐doped interconnected carbon nanospheres/potassium composite electrode with biomimetic fast ionic channels is developed to realize the dendrite‐free potassium metal batteries. The composite electrode provides abundant nucleation sites and interconnected ion transport channels, facilitating rapid ion transport kinetics and highly reversible potassium plating/stripping behaviors. Consequently, the assembled symmetric cell exhibits an ultra‐long cycle life (1100 h at 1.0 mA cm−2/1.0 mAh cm−2) in carbonate electrolyte. Moreover, the K full cells demonstrate enhanced cycling stability (1500 cycles at 8 C) and rate capacity (117.27 mAh g−1 at 20 C). This novel biomimetic design of composite anode presents an effective and rational approach for achieving stable PMBs.

Surface encapsulation of layered oxide cathode material with NiTiO3 for enhanced cycling stability of Na-ion batteries

Abstract In Na-ion batteries, O3-type layered oxide cathode materials encounter challenges such as particle cracking, oxygen loss, electrolyte side reactions, and multi-phase transitions during the charge/discharge process. This study focuses on surface coating with NiTiO3 achieved via secondary heat treatment using a coating precursor and the surface material. Through in-situ x-ray diffraction (XRD) and differential electrochemical mass spectrometry (DEMS), along with crystal structure characterizations of post-cycling materials, it was determined that the NiTiO3 coating layer facilitates the formation of a stable lattice structure, effectively inhibiting lattice oxygen loss and reducing side reaction with the electrolyte. This enhancement in cycling stability was evidenced by a capacity retention of approximately 74% over 300 cycles at 1 C, marking a significant 30% improvement over the initial sample. Furthermore, notable advancements in rate performance were observed. Experimental results indicate that a stable and robust surface structure substantially enhances the overall stability of the bulk phase, presenting a novel approach for designing layered oxide cathodes with higher energy density.

Enhanced Cycling Stability of All-Solid-State Lithium-Sulfur Battery through Nonconductive Polar Hosts.

All-solid-state lithium-sulfur batteries (ASSLSBs) are promising next-generation battery technologies with a high energy density and excellent safety. Because of the insulating nature of sulfur/Li2S, conventional cathode designs focus on developing porous hosts with high electronic conductivities such as porous carbon. However, carbon hosts boost the decomposition of sulfide electrolytes and suffer from sulfur detachment due to their weak bonding with sulfur/Li2S, resulting in capacity decays. Herein, we propose a counterintuitive design concept of host materials in which nonconductive polar mesoporous hosts can enhance the cycling life of ASSLSBs through mitigating the decomposition of adjacent electrolytes and bonding sulfur/Li2S steadily to avoid detachment. By using a mesoporous SiO2 host filled with 70 wt % sulfur as the cathode, we demonstrate steady cycling in ASSLSBs with a capacity reversibility of 95.1% in the initial cycle and a discharge capacity of 1446 mAh/g after 500 cycles at C/5 based on the mass of sulfur.

Electrospun polyimide nanofiber‐based separators containing carboxyl groups for lithium‐ion batteries

AbstractA lithium‐ion battery separator facilitates lithium‐ion transportation and prevents direct contact between the cathode and anode. Polyimide separators exhibited superior thermal stability and electrolyte wettability. In this study, carboxylated polyimide separators were prepared by electrospinning carboxyl group‐containing monomers. Polyimide separators were prepared with different content of carboxyl group‐containing monomer. Moreover, the thermal property, mechanical property, and electrochemical performance of separators were studied. The carboxylated polyimide separators exhibited lower interfacial resistance and higher ionic conductivity compared with polyimide separators. Moreover, the LiFePO4/Li half‐cell assembled using the carboxylated polyimide exhibited enhanced cycling stability and rate capability. Therefore, carboxylated polyimide separators with superior electrochemical performances are promising candidates for lithium‐ion batteries.

Coupling 3D vertical graphene skeleton with lithophilic ZnO Interface to enable highly stable lithium metal anode

Lithium metal has been considered as the most promising anode material for high energy density batteries owing to its high theoretical capacity and low reduction potential. Unfortunately, the uncontrollable growth of lithium dendrites and unrestrained volume expansion seriously hinder its practical applications. Designing 3D skeletons with high electronic conductivity, and superior lithophilicity to control the lithium plating/stripping process has been proven to be an effective strategy to alleviate these two issues. In this study, ZnO-decorated 3D vertical graphene skeleton (ZnO@VG) was developed as the host material to regulate lithium nucleation and dendrite growth. Attributing to the unique cavity arrangement, enlarged specific surface area, and numerous lithiophilic sites of ZnO@VG, a remarkable coulombic efficiency of 99.12 % after 350 cycles is achieved. Furthermore, symmetric cells based on ZnO@VG/Li electrodes demonstrate lower voltage polarization and enhanced cycling stability (over 1800 h) at 0.5 mA cm−2 and 1 mA h cm−2. Notably, when coupled with a LiFePO4 cathode, the full cell exhibits a discharge specific capacity of 100.33 mA h cm−2 at 5 C and maintains a high capacity retention of 89.1 % after 740 cycles at 1 C.

Manipulating Local Chemistry and Coherent Structures for High-Rate and Long-Life Sodium-Ion Battery Cathodes.

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na+ transport kinetics, elucidated by density functional theory calculations. Elevated Jahn-Teller [Mn3+O6] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na+ diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g-1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

Poly(3,4-ethylenedioxythiophene) encapsulation/intercalation boosting stability and zinc ion storage properties of vanadyl phosphates

The electrochemical properties of vanadyl phosphates as cathode materials for Zn-ion batteries have been severely hindered by their inherent poor electronic conductivity, unavoidable dissolution in aqueous solutions, and sluggish reaction kinetics. In this study, poly(3,4-ethylenedioxythiophene) (PEDOT) is introduced in vanadyl phosphates (PEDOT-VOP) through the in situ polymerization as interlayer guest species and surface coating layer, along with the generation of oxygen vacancies. The intercalated PEDOT develops strong interaction with the host layer, which can maintain its structural integrity. In addition, the PEDOT coating shell can enhance electronic conductivity together with oxygen vacancies to promote efficient electron transfer and prevent dissolution of active materials to stabilize the vanadyl phosphate core. As a result, the PEDOT-VOP electrode demonstrates a high discharge capacity of 180 mA h g−1 at 0.1 A/g with good rate performance (128 mA h g−1 at 2 A/g) and enhanced cycling stability (a capacity retention of 88.6 % after 2000 cycles at 1 A/g). The reversible Zn2+ insertion/extraction mechanism is further validated by diverse ex situ tests.

Enhanced cycling stability in 4.6 V LiCoO2 for high energy density lithium-ion batteries through Al and Y co-doping

For the first time, this work investigates the synergetic impact of yttrium (Y) and aluminium (Al) co-doping on the electrochemical properties of 4.6 V LiCoO2 (LCO) cathode for high energy density lithium-ion batteries. The optimized LCO demonstrates an impressive initial discharge capacity of 208.6 mAh g−1 in the voltage range of 3–4.6 V, along with superior structural stability, retaining over 86 % of its initial capacity even after 125 cycles at the current of 100 mA g−1 that is far higher than the capacity retention of 40 % for the pristine LCO under the same condition. Thanks to the synergistic effect, Al in Co layers enhances the bonds of Al/Co-O to stabilize oxygen in the LCO crystal structure while Y serves “pillar” in Li layers, migrated from the initial Co layers during cycling process, effectively curtail the formation and expansion of interlayer cracking, which contributes to the long-term cycle stability of LCO under high voltage. Most importantly, Al/Y co-doping is a facile process compatible with the existing industrial infrastructure for LCO mass production, and thus it can be scaled up readily for commercial applications. Al/Y co-doped LCO is assembled into commercial-level pouch cells with graphite anode, achieves an extremely high energy density of 750 Wh/L, and exhibits a superior cycling stability and obtains a capacity retention of 88.2 % at 25 °C after 800 cycles with the high cutoff voltage of 4.55 V.

Modulating Valence Electrons and Na Occupancy in Layered Cathodes for High-Performance Na-Ion Batteries.

Na-ion batteries (NIBs) hold promise as a leading option for large-scale energy storage. However, their development faces challenges due to the lack of high-performance cathode materials. P2-type layered oxides are seen as potential cathode materials for NIBs due to higher structure stability, yet their commercialization is hindered by limited capacity and subpar phase transitions during Na extraction and insertion at high voltages. In this study, we introduce a new P2-type cathode material, Na0.76Ni0.23Li0.1Ti0.02Mn0.65O1.998F0.02 (NLTMOF), synthesized with ternary Li/Ti/F substitution. This modification of ternary Li/Ti/F substitution significantly tailors the electronic structures, increasing the number of valence electrons near the Fermi energy level. This facilitates the electronic conductivity and their involvement in charge compensation, thereby enhancing reversible capacity. Additionally, ternary doping synergistically adjusts the Na occupancy at the Na layer for favorable Na extraction without P2-O2 phase transitions even under a high voltage of 4.4 V, boosting cycling stability. As a result, NLTMOF demonstrates a reversible capacity of 110.0 and 132.2 mAh g-1 at 2-4.2 and 2-4.4 V, respectively, and maintains greatly enhanced cycling stability over long cycles. This study sheds light on the design of transition metal oxides for advanced cathode materials through the modulation of electronic structure and Na occupancy in cathode materials, thus promoting the development of NIBs.

Na3.8MnV0.8Zr0.2(PO4)3/C/rGO composite cathode for sodium-ion battery with enhanced cycling stability and rate capability

Na3.8MnV0.8Zr0.2(PO4)3/C/rGO composite cathode for sodium-ion battery with enhanced cycling stability and rate capability

Bifunctional effects of nitrogen-doped carbon quantum dots on CoS2/mesoporous carbon composites for high-performance lithium-ion batteries

Cobalt disulfide (CoS2) stands as a promising candidate for anode materials in lithium-ion batteries due to its high theoretical capacity, but it faces challenges associated with the shuttle effect of lithium polysulfide during cycling. To address these issues, zeolitic imidazolate framework (ZIF)-derived composites have been extensively explored because of distinct advantages such as the formation of nano-sized particles, heteroatom doping, and highly porous structures. However, ZIF-derived carbon supports primarily consist of ultra-micropores that can impede lithium-ion diffusion. Herein, we aimed to enhance cycling stability by introducing a nitrogen-doped carbon quantum dot (NCQD) solution derived from N-methyl-2-pyrrolidone into cobalt-based ZIF-67 to modify the porosity and dope heteroatoms of CoS2 nanoparticle-embedded heteroatom-doped carbon composites (CoS2/NSC). The mildly acidic NCQD solution resulted in the partial etching of the ZIF-67 structure, along with the deposition of NCQDs as a nitrogen source. Notably, the pore sizes could be adjusted by varying the concentration of the NCQD solution, while retaining the nitrogen functional groups during carbonization. The electrode using CoS2/NSC with the 2.8 mL NCQD pre-treatment exhibited enhanced C-rate capability with the capacity of 392 mAh/g at 2.0 A/g. Moreover, the cycling stability was improved, with a capacity retention of 77 % after 100 cycles.

Understanding improved cycling and thermal stability of compositionally graded Ni-rich layered LiNi0.6Mn0.2Co0.2O2 cathode materials

The concentration gradient is a strategic design, adjusting the distribution of Ni, typically with a higher Ni content in the core and a higher Mn content toward the surface. This design leverages the pivotal role of the Ni/Mn ratio, seeking to optimize cathode performance by balancing Ni's high capacity with Mn's stabilizing effects, particularly at the surface where degradation commonly occurs during cycling. Our study delves into the intricate structural and chemical transformations within concentration gradient cathode materials during electrochemical cycling. Utilizing advanced synchrotron X-ray techniques, including hard and soft X-ray absorption spectroscopy (hXAS, sXAS), and nanoscale X-ray imaging, we investigate buried changes in concentration gradient LiNi0.6Mn0.2Co0.2O2 (CG NMC622). Contrary to conventional assumptions, our findings challenge the notion that cycling stability relies solely on Mn stability. Unraveling the roles of Ni and Mn, we uncover how their individual and collective contributions impact the cathode's overall performance. This investigation transcends established paradigms, shedding light on the crucial mechanisms governing the enhanced cycling stability of Ni-rich layered cathode materials.