Initial Discharge Specific Capacity Research Articles

Synergistic physical and chemical effects of MOF-derived porous Fe3C–NC to boost the performance of Li–S batteries

Lithium–sulfur (Li–S) batteries are one of the key objects of next-generation energy storage systems due to their high energy density and low-cost characteristics. However, the slow reaction kinetics and serious shuttle effect of lithium polysulfides (LiPSs) have hindered their practical application. In this work, metal-organic framework-derived Fe3C decorated nitrogen-doped carbon matrix (Fe3C–NC) composites were prepared to modify the separator to promote the reaction kinetics of Li–S batteries. The porous and conductive NC facilitates the trapping of LiPSs, rapid transfer of charge, and alleviated volume expansion, while the Fe3C–NC with optimum Fe3C content can significantly reduce the energy barrier of the electrochemical conversion reaction, accelerate the transport of lithium ions, and enhance the reaction kinetics of LiPSs, which are conducive to inhibit the shuttle effect through synergistic physical and chemical interactions. The Li–S battery with Fe3C–NC separator exhibits excellent cycle stability with an initial discharge specific capacity of 1099.19 mAh g−1 at 1 C and a low-capacity decay of 0.068% per cycle over 500 cycles. Even at a high S loading of 5.93 mg cm−2, it still delivers reliable cyclic stability with an initial discharge specific capacity of 903.65 mAh g−1 at 0.1 C. This work provides a convenient and effective method for the application of metallic materials combined with nitrogen-doped carbon matrix in high-performance Li–S batteries.

Nanocellulose-reinforced nanofiber composite poly(aryl ether ketone) polymer electrolyte for advanced lithium batteries.

Solid polymer batteries (SPEs) are highly desirable for energy storage because of the urgent need for higher energy density and safer lithium ion batteries (LIBs). In this work, the single-ion lithium salt PAEK50-LiCPSI was synthesized by grafting 3-chloropropanesulfonyl trifluoromethanesulimide lithium (LiCPSI) onto poly(aryl ether ketone)50 (PAEK50). Nanocellulose (NCC), PAEK50-LiCPSI, and poly(vinylidene fluoride) (PVDF-HFP) were compounded to obtain NCC reinforced high-performance nanofiber composite polymer electrolytes (NCC/PAEK/PVDF) through electrospinning, which presented tensile strength of 15.35MPa, ionic conductivity of 1.13×10-4Scm-1, and Li+ transfer number as high as 0.80 at 25°C. The assembled LIBs with NCC/PAEK/PVDF illustrated an initial discharge specific capacity of 155.2 mAh g-1 at 0.2C, and the capacity retention rate was close to 93% after cycling 700cycles at 25°C. Furthermore, its initial specific discharge capacity at -20°C was 103.4 mAh g-1, and can cycle over 300cycles. The NCC with sulfonic acid group reinforced the mechanical performance, promoted the dissociation of Li+, and synergized with PAEK50-LiCPSI and PVDF-HFP to form a 3D nanofiber ionic bridge network through hydrogen bond, which promoted the more stable and faster Li+ transportation. This work suggested that the NCC/PAEK/PVDF can be a good choice of solid polymer electrolytes (SPE) for the next generation of LIBs, even working at low-temperatures.

Preparation and electrochemical performance of a novel bimetallic antimony-based chalcogenide compound CuSbSe2 as anode material for quasi-solid-state batteries

A novel bimetallic antimony-based selenide anode material, CuSbSe2, was developed through the vacuum solid-state sintering technique. Subsequent studies concentrated on modifying its carbon coating. The active materials were characterized in terms of composition using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their morphology was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of the electrochemical analysis revealed that under half-cell conditions, the carbon-coated CuSbSe2@C active material demonstrated initial discharge specific capacities of 608.57 mAh·g-1 at a current density of 0.1C (0.047A/g) and 390.29 mAh·g-1 at 1C (0.47A/g). After 200 cycles, the capacity retention rates were measured at 65.48% and 70.29%, respectively. The application of galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy revealed that the carbon coating significantly enhanced the charge transport properties of the CuSbSe2@C material. This improvement contributed to superior rate performance, specific capacity, and various other electrochemical characteristics of the active material. Additionally, the CuSbSe2@C/Li1.5Al0.5Ge1.5(PO4)3/LiFePO4 quasi-solid-state cell exhibited a discharge specific capacity of 339.72 mAh·g-1 at a current density of 0.2C, with a capacity retention of 60.37% after 100 cycles. These experimental findings suggest that CuSbSe2@C has considerable potential as an anode material for both conventional lithium batteries and solid-state cells.

An ultrathin conformal layer of dry-coated Li+-conductive glass–ceramic for single-crystalline nickel-rich cathode towards all-solid-state lithium batteries

All-solid-state lithium batteries pairing nickel-rich oxide cathodes with nonflammable solid electrolytes deliver greatly combined safety and high-energy–density merits. However, the oxide cathodes possess high oxidability and easily oxidize solid electrolytes, such as sulfides and polymers, leading to great interfacial resistance and rapid performance degradation. Herein, by employing single-crystalline LiNi0.83Co0.11Mn0.06O2 (SCNCM) as typical oxide cathode, we propose a Li+-conductive glass–ceramic phosphate (GCP) as an ultrathin conformal layer using a cost-effective dry processing strategy. The GCP conformal layer possesses triple appealing advantages: (i) GCP melts at a relatively low temperature (∼790 °C) and spreads out to improve the coating coverage, effectively blocking the interfacial oxidation of solid electrolyte by high-oxidative cathode. (ii) The melted GCP adheres tightly to the cathode surface, alleviating the delamination of coating layer on the cathode during long-term cycling. (iii) GCP possesses excellent Li+ conductivity of 0.29 mS cm−1, facilitating the charge transfer and Li+ diffusion processes. These functions contribute to diminishing interfacial resistance increases across cycling, improving longterm cycling stability of SCNCM cathodes. Consequently, the SCNCM@GCP shows excellent interfacial stability with sulfide solid electrolyte, possessing an outstanding capacity retention of 86.1 % after 100 cycles with a high initial specific discharge capacity of 161.9mAh/g at 0.2C (72.4 % and 130.2mAh/g for SCNCM).

Fluorine-doped carbon coating of LiFe0.5Mn0.5PO4 enabling high-rate and long-lifespan cathode for lithium-ion batteries

The limited electron and ionic conductivity, along with the sluggish kinetics caused by the Jahn-Teller effect of Mn3+, impose constraints on the electrochemical performance of LiFexMn1-xPO4. Herein, the surface of LiFe0.5Mn0.5PO4 (LFMP) is modified with a F-doped carbon using the solvothermal and calcination methods. The incorporation of F-doped carbon coating, along with the formation of interfacial F-Li, F-Fe and F-Mn bonds between the carbon layer and LFMP nanoparticles, significantly mitigates charge transfer resistance, facilitates rapid electron transfer, as well as enhances Li+ diffusion kinetics. The LFMP@C-F2 cathode prepared in this study exhibits an unexceptionable capacity retention of 90.5 % after 300 cycles at a low rate of 0.2C and a capacity retention of 78.8 % over 1000 cycles at a high rate of 1C. When incorporated into the solid battery configuration (Li/PEO-LATP CSE/LFMP@C-F2), it exhibits an initial discharge specific capacity of 148 mAh g−1 and maintains a capacity retention of 85.8 % after 60 cycles at 0.1C, thereby offering an innovative approach to enhance the performance of LFMP in terms of cycling stability and rate capacity in lithium-ion batteries, as well as to apply LFMP into solid-state lithium batteries.

In–situ construction of LixFeyOz coatings on cobalt–free lithium–rich cathode materials for enhanced structural stability and electrochemical performance

Environmentally benign and cost–effective cobalt–free lithium–rich cathode materials have garnered significant interest. Nevertheless, the irreversible loss of lattice oxygen compromises their structural integrity, leading to capacity fade, voltage decay, and sluggish kinetics, which collectively impede their commercial viability. To address these challenges, this study introduces an in–situ formation of LixFeyOz coatings on the surface of cobalt–free lithium–rich materials by utilizing residual lithium compounds. At elevated temperatures, the residual lithium compounds on the surface of Li1.2Mn0.6Ni0.2O2 (LMNO) react with FeO to generate a LixFeyOz protective layer. This coating not only shields the bulk material from direct exposure to the electrolyte but also effectively consumes residual lithium compounds to suppress interfacial side reactions, thereby enhancing structural stability. The LixFeyOz layer acts as a lithium–ion conductor, facilitating the migration of lithium ions and markedly boosting the material's electrochemical performance. Experimental results indicate that at a current density of 1C, the initial discharge specific capacity of LMNO@Fe is 235.24 mAh g−1 with a capacity retention of 91.33 % after 100 cycles, compared to 211.62 mAh g−1and 77.95 % for LMNO, respectively. Even at a higher current density of 5C, the LMNO@Fe maintains a discharge specific capacity of 148.30 mAh g−1. This research demonstrates that the LixFeyOz coating on cobalt–free lithium–rich cathode materials offers a promising strategy for achieving high–performance lithium–ion batteries.

Favorable Moderate Adsorption of Polysulfide on FeNi3 Intermetallic Compound Accelerating Conversion Kinetics for Advanced Lithium-Sulfur Batteries.

Sluggish conversion kinetics of polysulfides during discharge and the severe shuttle effect significantly hinder the practical application of lithium-sulfur (Li-S) batteries. In this work, the lattice engineering strategy of Fe hybridization is employed to manipulate the bulk phase spacing of FeNi3 (space group Pm3m) intermetallic compounds to adjust the 3d electronic structure, optimizing the adsorption of polysulfides, thereby accelerating the catalytic conversion. As a result, FeNi2.25@OC achieves favorable moderate adsorption toward polysulfides. Due to the larger number of electrons occupying the lowest occupied molecular orbital of Li2S4, the S-S bonds are weakened and broken. Temperature-dependent experiments confirm that FeNi2.25@OC exhibits the lowest activation energy and can effectively accelerate the catalytic conversion of polysulfides. The Li-S cell assembled with FeNi2.25@OC modified PP separator delivers a high initial discharge specific capacity of 1219.5 mAh g-1 at 0.2 C. Even at a high sulfur loading of 6.06mg cm-2 and lean electrolyte conditions (6 µL mg-1), it can cycle stably for 60 cycles.

Multiple hydrogen bonding induced by semi-interpenetrating polymer network binder to enhance the electrochemical performance of sodium-ion batteries electrodes

Molybdenum disulfide (MoS2) serves as an ideal anode for sodium-ion batteries (SIBs), boasting a high theoretical specific capacity and large interlayer spacing. However, the substantial volume change and low conductivity present significant challenges in maintaining the electrochemical stability of the electrode. Herein, a novel semi-interpenetrating polymer network (SIPN) binder (sodium alginate-g-poly (acrylamide-co-2-hydroxyethyl acrylate)-boric acid, SA-PAHB) is synthesized by free radical copolymerization grafting and the multiple hydrogen bonding crosslinking (bond energies spanning from − 33.89 to − 45.49 kcal/mol by theoretical calculations), which can effectively mitigate stress in Na+ deintercalation in MoS2 anodes under the synergy of the unique structure of the SIPN, maintaining electrode stability. Simultaneously, the variable hydrogen bonding crosslinking and abundant –NH2 groups greatly facilitate Na+ diffusion and enhance kinetic performance. Leveraging the advantages of SA-PAHB, the electrochemical performance is significantly enhanced compared to traditional SA and grafted SA-based binders. Specifically, MoS2 anodes using SA-PAHB binder exhibit an initial discharge specific capacity of 772.1 mAh/g at 0.1 A/g and retain 511.2 mAh/g at 0.5 A/g after 200 cycles, with no capacity loss. Additionally, an outstanding rate performance is achieved, delivering 378.5 mAh/g at 10 A/g. For sodium-ion coin full-cells, a discharge specific capacity of 125.2 mAh/g is maintained at 0.5 A/g after 50 cycles.

One-stone-for-two-birds strategy to construct robust 2D conjugated metal-organic framework-based quasi-solid-state lithium-organic batteries

Quasi-solid-state lithium batteries (QSSLBs) are emerging as attractive candidates for overcoming the disadvantages of liquid and solid batteries. However, they face challenges in terms of enhancing the poor interfacial stability and promoting selective Li+ conduction. Herein, one-stone-for-two-birds strategy is proposed that involves using a two-directional conjugated metal organic framework (2D-cMOF, Fe-TABQ) as both the cathode material and a polymer–electrolyte filler to construct high-performance quasi-solid-state lithium–organic batteries (QSSLOBs). Additionally, Fe-TABQ promotes the cleavage of C–F bonds, thus facilitating the formation of a LiF-rich solid electrolyte interface (SEI). Therefore, the composite polymer electrolyte presents a high Li+ transference number of 0.93 and a high ionic conductivity of 6.22 × 10−3 mS cm−1. Meanwhile, Li/Li symmetric cells deliver stable cyclability for 1,500 h at 25 ℃ and a current density of 0.05 mA cm−2. Even the assembled QSSLOBs exhibit a high initial discharge specific capacity of 248.39 mAh/g at 25 ℃, and 50 mA g−1 and long cycle stability with 70 % capacity retention after 200 cycles at 25 ℃ and 1,000 mA g−1. The present findings reveal the multiple functional potentials of 2D-cMOFs in constructing robust QSSLOBs.

Synergistic Regulation of Bidirectional Conversion of LiPSs and Li2S Using Anthraquinone as a Redox Mediator.

Lithium-sulfur (Li-S) batteries are strong contenders as energy storage options in the next-generation, primarily because of their potential for delivering high energy densities. Nonetheless, their widespread commercialization faces several obstacles, including sluggish sulfur redox kinetics, the insulating properties of the Li2S discharge product, and significant reaction energy barriers. In this work, anthraquinone (AQ) was introduced as a redox mediator and incorporated onto Co-doped carbon materials through π-π interactions. The results showed that synergistic effect between AQ and Co atoms facilitated the bidirectional conversion of lithium polysulfides (LiPSs) and Li2S. During charging, AQ lowered the reaction energy barrier for Li2S oxidation and thereby enhanced the reversibility of sulfur redox reactions. Density functional theory (DFT) calculations showed that AQ-Li2Sx exhibits a lower energy for the lowest unoccupied molecular orbital (LUMO) and a higher energy for the highest occupied molecular orbital (HOMO). Experimental results demonstrated that an impressive initial discharge specific capacity of 1290 mAh g-1 was achieved by the fabricated S@AQ/Co-N-C electrode at 0.1 C. After 600 cycles at 1 C, it retained 64% of this capacity and exhibited a minimal 0.06% capacity decay rate per cycle.

Preparation and Carbon Nanotube Modification of High Voltage LiNi0.5Mn1.5O4 Cathode Materials

In this study, the nickel-manganese binary cathode material was synthesized using a high-temperature solid-state roasting method. The effects of roasting temperature and roasting time on the electrochemical performance of the cathode material was investigated. The research demonstrated that under conditions of 850 °C for 12 h, the synthesized LNMO exhibited an Fd-3 m space group structure characterized. The initial discharge-specific capacity reached 135 mAh·g⁻¹ at a rate of 0.2C, while the capacity retention rate was 91.8 % after 100 cycles. Following the modification with carbon nanotubes, exhibited an initial discharge capacity of 140 mAh·g⁻¹ at a rate of 0.2 C, maintaining a capacity retention rate of 92.9 % after 100 cycles. Carbon nanotube modification was implemented to address the poor conductivity and unstable electrochemical performance of LNMO when utilizing acetylene black as a conductive agent. This finding suggests that the unique three-dimensional conductive network formed by carbon nanotube offers superior modification effects compared to acetylene black, while the reduced quantity of conductive agent used also contributes to cost savings.

Multifunctional cu-Cu3P heterojunction embedded in hierarchically porous carbon nanofibers to strengthen adsorption and catalytic effects based on built-in electric field for li[sbnd]S cell

Lithium sulfur batteries (LSBs) are considered a highly promising next-generation battery system. However, severe shuttle effect and slow redox kinetics of lithium polysulfides (LiPSs) in LSBs are still the main obstacles hindering their rapid developments. In this study, the multifunctional Cu-Cu3P heterojunction nanoparticles embedded in hierarchically porous carbon nanofibers (PCNFs) are designed and prepared for modifying separator of LSBs. The highly conductive metal Cu and PCNFs can synergistically enhance the conductivity of electrons and ions, and physically suppress “shuttle effect” of lithium LiPSs. Meanwhile, based on the spontaneous built-in electric field at the formed heterogeneous interfaces of Cu-Cu3P, the heterojunction also can chemically adsorb LiPSs and greatly catalyze conversion of LiPSs, thus further suppressing the “shuttle effect” and excellent reaction kinetics of LiPSs. Based on these merits, the assembled LSBs using the heterojunction Cu-Cu3P@PCNFs modified separator show outstanding initial specific discharge capacities up to 1009.2 mAh g−1 at 1C and 998.5 mAh g−1 at 2C, and stable cycling with an average capacity decay rate of 0.067 % and 0.084 % at 1C during 800 cycles and at 2C during 580 cycles, respectively. Even at a high sulfur loading of 2.5 mg cm−2, an excellent specific discharge capacity of 784.6 mAh g−1 after 180 cycles 0.5C still can be realized. The work provides a novel perspective on understanding adsorption and catalytic design in energy storage equipment based on heterojunction engineering and built-in electric field.

Utilization of Y-MOF-derived Y2O3/YS@C heterojunction for Li-S battery separators

Due to its exceptional energy density and specific capacity, the lithium-sulfur battery is considered one of the most promising energy storage devices. However, the practical use of Li-S batteries is significantly hindered by both the shuttle effect and slow conversion of polysulfides. In order to address the shuttle effect of polysulfides, we utilized a Y-MOF derivative Y2O3/YS@C composite material as a modifier layer for Li-S battery separators. Initially, we synthesized Y-MOF by reacting tetra-hydroxyacetate yttrium and isophthalic acid in a solution. Subsequently, we sulfurized the Y-MOF precursor with thioacetamide and heat-treated it at high temperature to obtain Y2O3/YS@C composite material. The strong affinity of metal sulfides for sulfur provides chemical anchoring ability for polysulfide, while the heterogeneous structure can couple non-homogeneous regions together to produce synergistic effects and better catalyze polysulfides. By using Y2O3/YS@C as a separator modifier, we effectively suppressed the shuttle effect of polysulfides and improved electrochemical performance. At 3 mg cm−2 sulfur loading, the initial discharge specific capacity of the Y2O3/YS@C separator at 0.5 C was 966.1 mAh g−1; after 400 cycles, it still maintained a discharge specific capacity of 530.5 mAh g−1 with a capacity retention rate of 54.9 %. When increasing sulfur loading to 5 mg cm−2, the first-cycle discharge specific capacity at 0.l C was 831.4 mAh g−1; after 100 cycles, it was still 738.7 mAh g−1, with a capacity retention rate of 88.8 %.

Breaking boundaries in O3-type NaNi1/3Fe1/3Mn1/3O2 cathode materials for sodium-ion batteries: An industrially scalable reheating strategy for superior electrochemical performance

To address the challenges of air stability and slurry processability in layered transition metal oxide O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM) for sodium-ion batteries (SIBs), we have designed an innovative 500 °C reheating strategy. This method improves the surface properties of NFM without the need for additional coating layers, making it more efficient and suitable for large-scale applications. Pristine NFM (NFM-P) was first synthesized through a high-temperature solid-state method and then modified using this reheating approach (NFM-HT). This strategy significantly enhances air stability and electrochemical performance, yielding an initial discharge specific capacity of 151.46 mAh/g at 0.1C, with a remarkable capacity retention of 95.04% after 100 cycles at 0.5C. Additionally, a 1.7 Ah NFM||HC (hard carbon) pouch cell demonstrates excellent long-term cycling stability (94.64% retention after 500 cycles at 1C), superior rate capability (86.48% retention at 9C), and strong low-temperature performance (77% retention at − 25 °C, continuing power supply at − 40 °C). Notably, even when overcharged to 8.29 V, the pouch cell remained safe without combustion or explosion. This reheating strategy, which eliminates the need for a coating layer, offers a simpler, more scalable solution for industrial production while maintaining outstanding electrochemical performance. These results pave the way for broader commercial adoption of NFM materials.

Separator functionalization realizing stable zinc anode through microporous metal-organic framework with special functional group

Aqueous zinc ion batteries (AZIBs) have been regarded as one of the most promising energy storage systems because of their security, high specific capacity and abundant zinc resources, etc. Despite the promising prospects of AZIBs, their practical application is still plagued by dendrite and side reactions on zinc surface. In this paper, glass fiber separators were modified by in-situ loading metal-organic framework MIL-125 (M-125) and its -NH2-functionalized material (NM-125). The designed separator pore structure was successfully adjusted and endowed with -NH2 functional groups, which can ultimately dramatically enhance the electrochemical performance of AZIBs under practical operation conditions. The functionalized NM-125 with smaller pore size and particle size enables NM-125-GF to prevent the transport of macromolecular anions in the electrolyte, guiding and promoting zinc ions to undergo an orderly migration. In addition, -NH2 of NM-125 can adsorb Zn2+ and detach them from the solvated structure, inhibiting the generation of anode-side reactions and optimizing battery performance. Notably, Zn||MnO2 full cell assembled with -NH2 functionalized separator also shows a high initial discharge specific capacity (160.2 mAh g-1) with a high capacity retention of ∼99.8% even after 700 cycles. The rational design of the functionalized separator provides a useful guideline for optimizing high-performance AZIBs.

Facilitating the oxygen redox chemistry in O3-type layered oxide cathode material for sodium-ion batteries by Fe substitution

Facilitating anion redox chemistry is an effective strategy to increase the capacity of layered oxides for sodium-ion batteries. Nevertheless, there remains a paucity of literature pertaining to the oxygen redox chemistry of O3-type layered oxide cathode materials. This work systematically investigates the effect of Fe doping on the anionic oxygen redox chemistry and electrochemical reactions in O3-NaNi0.4Cu0.1Mn0.4Ti0.1O2. The results of the density functional theory (DFT) calculations indicate that the electrons of the O 2p occupy a higher energy level. In the ex-situ X-ray photoelectron spectrometer (XPS) of O 1s, the addition of Fe facilitates the lattice oxygen (On−) to exhibit enhanced activity at 4.45 V. The in-situ X-ray diffraction (XRD) demonstrates that the doping of Fe effectively suppresses the Y phase transition at high voltages. Furthermore, the Galvanostatic Intermittent Titration Technique (GITT) data indicate that Fe doping significantly increases the Na+ migration rate at high voltages. Consequently, the substitution of Fe can elevate the cut-off voltage to 4.45 V, thereby facilitating electron migration from O2−. The redox of O2−/On− (n < 2) contributes to the overall capacity. O3-Na(Ni0.4Cu0.1Mn0.4Ti0.1)0.92Fe0.08O2 provides an initial discharge specific capacity of 180.55 mA h g−1 and 71.6% capacity retention at 0.5 C (1 C = 240 mA g−1). This work not only demonstrates the beneficial impact of Fe substitution for promoting the redox activity and reversibility of O2− in O3-type layered oxides, but also guarantees the structural integrity of the cathode materials at high voltages (>4.2 V). It offers a novel avenue for investigating the anionic redox reaction in O3-type layered oxides to design advanced cathode materials.

Application of Y-MOF-CNT-Derived Y2O3-C@CNT Composites in Lithium-Sulfur Battery Separators.

In order to mitigate the shuttle effect of lithium polysulfides in lithium-sulfur batteries, we propose a yttrium-metal-organic framework-carbon nanotube (Y-MOF-CNT)-derived Y2O3-C@CNT composite for modifying the separator in this study. The Y-MOFs, comprising yttrium (Y) rare earth metal and terephthalic acid, exemplify a prototypical category of metal-organic framework (MOF) materials. They manifest the advantageous attributes associated with MOFs while concurrently possessing distinctive catalytic traits ascribed to rare earth elements. In this study, Y-MOF nanoparticles were synthesized on carbon nanotube (CNT) substrates via a facile aqueous solution method, succeeded by high-temperature carbonization to yield Y2O3-C@CNT composite materials. These composites were subsequently employed as coatings on one side of polyethylene (PE) separators. The resultant Y2O3-C@CNT composite inherits the particle-like morphology and porosity from its precursor Y-MOF, alongside the inherent conductivity in carbon-based materials. This amalgamation is conducive to polysulfide capture and catalytic conversion processes within lithium-sulfur batteries. The application of the Y2O3-C@CNT-coated PE separator effectively mitigated polysulfide shuttle effects and significantly enhanced the battery electrochemical performance. At a sulfur loading level of 3 mg cm-2 under a 0.5 C rate, an initial discharge specific capacity of 900 mAh g-1 was achieved. After 400 cycles, the discharge specific capacity remained at 483.85 mAh g-1 with a capacity retention rate of 53.7%. Upon increasing sulfur loading to 5 mg cm-2, the discharge specific capacity at a lower rate (0.1 C) reached 817.8 mAh g-1; even after 100 cycles, it maintained a value of 700 mAh g-1 with a capacity retention rate of 85.6%. Notably, our modified Y2O3-C@CNT separator demonstrated exceptional cycling stability, even under conditions involving high sulfur loading.

Mg(Al, Fe, Mn, REE)2O4 Spinel Prepared from Pelagic REE-Rich Clays and Application as Magnesium-Ion-Battery Cathodes.

The oxidation and lattice distortion of spinel oxides used for magnesium-ion battery (MIB) cathodes lead to poor stability and cycling performance. Herein, the highly inverted spinel oxide Mg(Al, Fe, Mn, REE)2O4 of i = 0.62 with incorporated rare-earth elements (REE) and decent specific surface area was prepared by utilizing leachate of the pelagic rare-earth-rich clays via a foamed sol-gel/calcination method. Measurements of specific capacity, cycling performance, and multiplicity performance showed that the foamed spinel exhibited distinguished electrochemical performance of MIB. At the current density of 100 mA h-1, the initial discharge and charge specific capacity were 125.7 mAh g-1 and 139.7 mAh g-1, and the reversible discharge and charge specific capacities were maintained as 96.7 mAh g-1 and 102.4 mAh g-1 after 200 cycles of charging-discharging. The Mg-ion diffusion rate for MAFMRO was 1.08 × 10-5 cm2 s-1, which was significantly improved, compared to traditional magnesium spinel anodes. This work highlights an approach for modification of spinel-type cathode materials and the high-value utilization of pelagic clay resources.

Core-shell structure and high rate performance of Ce-doped Li4Ti5O12 for lithium-ion battery anode materials

Lithium titanate (LTO) can be a very promising anode material for lithium-ion batteries (LSBs) due to its inherent ability to inhibit the growth of lithium dendrites as well as its unique “zero-strain” properties. Unfortunately, the low electronic conductivity of LTO leads to serious shortcomings in higher electrochemical demands. In this work, the Ce3+-doped C@Li4Ti5-xCexO12 (x = 0, 0.1, 0.15 and 0.2) anode materials synthesized by the hydrothermal method using carbon spheres as templates showed more significant improvement in both structural and electrochemical properties. The results demonstrate that electronic conductivity, lithium-ion diffusion rate, discharge specific capacity, discharge rate capability, and significant improvement stability of C@Li4Ti5-xCexO12 (x = 0.1, 0.15 and 0.2) electrodes. Among them, C@Li4Ti4.85Ce0.15O12 electrode exhibits the highest initial discharge specific capacity (250.86 mAh/g) at 0.1C, which is 1.28-fold that of C@ Li4Ti5O12 (195.94 mAh/g), and initial discharge capacity from 205.96 mAh/g to 170.39 mAh/g after 500 cycles, corresponding to 82.7 % of the initial stable discharge capacity. The outstanding performance of C@Li4Ti4.85Ce0.15O12 can be attributed to the lower interfacial impedance, higher electronic conductivity, high oxygen vacancy concentration, and moderate amount of Ce3+ doping can enhance the electrochemical activity. In addition, carbon sphere surface defects shown to be effective in improving lithium-ion storage. This work demonstrates that Ce3+ doping is an effective method to improve the electrochemical performance of LTOs and provides a more effective guide for designing and optimizing anode electrode materials for lithium-ion batteries.

Roles of fast-ion conductor NaAlO2 modifying P2-Na0.67Ni0.3Mn0.6Co0.1O2 cathode material for sodium-ion batteries

P2-type layered oxides are promising candidates for sodium-ion batteries. However, structural instability and sluggish Na⁺ diffusion kinetics hinder their further commercialization. In this study, NaAlO2, which possesses a similar α-NaFeO2 layer structure, is coated onto the surface of P2-Na0.67Ni0.3Mn0.6Co0.1O2 (NNMC) to enhance its electrochemical performance as a novel cathode for sodium-ion batteries. A variety of experimental results and characterizations reveal that the thin NaAlO2 coating layer significantly reduces side reactions and facilitates the diffusion of Na⁺ at the interface between the cathode and the electrolyte. Moreover, the introduction of partial Al ions into the transition-metal layers enlarge the interlayer spacing, and decrease the content of Mn3+. As a result, the NNMC cathode material, modified with 3 wt% NaAlO2, demonstrated remarkable electrochemical performance. The initial specific discharge capacity was recorded at 137.7 mA h g−1 at 0.2 C, and an impressive discharge capacity of 38.2 mA h g−1 was attained at 20 C. Following 100 cycles at a rate of 0.5 C, the capacity retention rate was determined to be 99.6 %.