Ionics最新文献

Lithium iron phosphate (LiFePO₄) is emerging as a key cathode material for the next generation of high-performance lithium-ion batteries, owing to its unparalleled combination of affordability, stability, and extended cycle life. However, its low lithium-ion diffusion and electronic conductivity, which are critical for charging speed and low-temperature performance, have become the primary constraints on its broader application. This study addresses these challenges by investigating the impact of Mn, Ti, and V doping on the low-temperature discharge characteristics of LiFePO₄. The article presents the synthesis of LiFe_0.95V_0.05PO₄, LiFe_0.95Ti_0.05PO₄, and LiFe_0.95Mn_0.05PO₄, which have demonstrated impressive discharge capacities of 88%, 80%, and 76% at − 20 °C compared to their performance at 25 °C. The vanadium doping strategy has been found to encourage the spherical growth of lithium iron phosphate material, resulting in nano-spherical particles with a balanced transverse and longitudinal growth rate. This growth pattern is attributed to the interplay between the “Mosaic models” and “Radial models” of lithium ion diffusion. The electronic and ionic transport properties have been analyzed using density functional theory, revealing that it possesses low formation energy at the Fe site. This characteristic allows for stable doping at the Fe site, leading to the formation of Mn–O, Ti–O, and V–O chemical bonds. The doping with vanadium significantly lowers the migration energy barrier and activation energy for lithium ions, thereby enhancing their transmission rate. These findings indicate that vanadium doping is an effective strategy to improve the low-temperature discharge performance of LiFePO₄ cathode materials.

Hybrid supercapacitors (HSCs) integrate battery-type materials and capacitive materials into the same electrode by means of internal parallel, which greatly improve the energy density while maintaining the power density and meet the needs of more applications. However, different material systems have varying effects on the electrical performance and safety characteristics of HSCs. This paper conducted theoretical research on the electrical and thermal properties of key materials for HSCs to achieve performance improvement. The cathode was composed of lithium nickel cobalt manganate oxide (LiNi_0.6Co_0.2Mn_0.2O₂, NCM622) and activated carbon (AC). It was found that adding an appropriate amount of AC can reduce the internal resistance. However, an excessively high proportion of AC leaded to a decrease in compact density and a decline in electrochemical performance. The optimal NCM/AC ratio was determined to be 9:1. Moreover, a comparative study of different separator materials revealed that the use of polyethylene terephthalate (PET)/ceramic composite separators significantly improves the safety of HSCs, reducing the maximum temperature during thermal runaway by 30 °C, and exhibiting a high self-discharge retention rate of 90% after 350 days at 55 °C. Furthermore, the investigation of different carbon materials for the anode found that hard carbon (HC) possesses larger interlayer spacing, more structural defects, and irregular edge spaces, resulting in superior rate capability, cycling performance, and high/low-temperature characteristics. Through material optimization, the constructed HSCs achieved an energy density of 122.8 Wh kg⁻¹, with 97.2% energy at 10 °C compared to 1 °C, a 99% energy retention rate after 5000 cycles, 76.24% energy at − 25 °C compared to 25 °C, and demonstrating exceptional safety properties.

Lithium-rich nickel manganese cobalt oxide (LR-NMC) cathode materials have been considered in next-generation Li-ion batteries for electric vehicles due to their high energy density and cost-effectiveness. However, LR-NMC cathode materials suffer from poor rate capability and cyclic stability. In addition, the reliance on environmentally harmful and expensive cobalt resources presents an additional challenge for cobalt-containing cathode materials. To overcome these challenges, two cobalt-free lithium-rich cathode material compositions, Li_1.2Ni_0.2Mn_0.56Al_0.04O₂ (LR-NMA-1) and Li_1.2Ni_0.18Mn_0.57Al_0.05O₂ (LR-NMA-2), are designed and synthesized via co-precipitation method. The structural stability, which has been negatively affected by the absence of cobalt in the materials synthesized, is compensated by the addition of Al, and this objective is clearly achieved, particularly for the LR-NMA-2 material. The initial specific discharge capacity of LR-NMA-2 at 0.1C is 224.1 mAh/g, and the capacity retention after 100 cycles at 0.5C is 78%. Furthermore, the poor rate capability performance typically found in lithium-rich cathode materials is significantly improved in the LR-NMA-2 material due to its high c-axis lattice parameter, which is obtained by the presence of an appropriate amount of Al in the layered structure. The capacity of 120.6 mAh/g at a current density of 5C further demonstrates the superior rate capability performance of the Li_1.2Ni_0.18Mn_0.57Al_0.05O₂ material.

High-entropy oxides (HEOs), composed of five or more distinct metal ions within a unified crystalline lattice, exhibit exceptional electrochemical capacity and catalytic properties. These characteristics make them highly valued materials for lithium-ion batteries (LIBs). However, their inherent low conductivities pose a significant challenge to further advancements in HEO development. Herein, a new kind of HEO, (Y_0.2La_0.2Ce_0.2Ca_0.2Mg_0.2)₂(Sn_1-xAl_x)₂O₇ is synthesized via a facile co-precipitation reaction, with various aluminum (Al) content doping (x = 0, 0.05, 0.1, 0.15). The optimized sample (x = 0.1) exhibits a superior initial discharge specific capacity of 1209.9 mAh g⁻¹ at 0.1 mA g⁻¹. This study provides clear evidence that incorporating metal doping into the structure of HEOs is an exceptionally effective strategy for enhancing its electrochemical performance as anode materials in LIBs.

The global energy demand requires high energy conversion and storage devices. To increase the utility of these devices, highly efficient, stable, and cost-effective electrode materials are needed. In the present study, MoS₂ nanomaterials were synthesized using a hydrothermal process using ammonium heptamolybdate tetrahydrate as a molybdenum source and thiourea as the sulfur source. The prepared sample structure and morphology were characterized by using XRD, UV, FTIR, SEM, and EDAX. The electrochemical behavior was studied by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge–discharge analysis (GCD), and stability. The crystalline size of the prepared sample was calculated as 9.6 nm. The bands at 588 cm⁻¹ and 646 cm⁻¹ correspond to Mo-S vibrations and 898 cm⁻¹ correspond to S–S vibrations. The direct energy band gap was calculated as 2.85 eV. The EDLC supercapacitor showed a high specific capacitance of 1168.23 Fg⁻¹ for the current density 1 Ag⁻¹.

In lithium-sulfur (Li–S) batteries, the shortened cycle life often arises from the migration of dissolved polysulfides to the anode. To address this issue, a sulfur host composite material was developed, featuring heteroatom-doped porous carbon combined with carbon nanotubes (PC/CNTs). The penetration of CNTs into the porous carbon imparts a cohesive high-conductivity network structure, thereby substantially augmenting the utilization of the active sulfur. Moreover, the copious pore architecture facilitates the diffusion of lithium ions and serves as sites for the physical adsorption of polysulfides. Furthermore, heteroatom doping can enhance the polarity of carbon materials, effectively quelling the “shuttle effect” by amplifying the chemical attraction and catalytic conversion of polysulfides. Drawing upon these findings, the S-PC/CNT electrode reveals stellar electrochemical performance.

This comprehensive review explores the remarkable progress and prospects of diatomaceous earth (DE) as a bio-template material for synthesizing electrode materials tailored explicitly for supercapacitor and battery applications. The unique structures within DE, including its mesoporous nature and high surface area, have positioned it as a pivotal material in energy storage. The mesoporous framework of DE, often defined by pores with diameters between 2 and 50 nm, provides a substantial surface area, a fundamental element for charge storage, and transfer in electrochemical energy conversion and storage. Its bio-templating capabilities have ushered in the creation of highly efficient electrode materials. Moreover, the role of DE in enhancing ion accessibility has made it an excellent choice for high-power applications. As we gaze toward the future, the prospects of DE as a bio-template material for supercapacitor and battery electrode material appear exceptionally promising. Customized material synthesis, scalability challenges, multidisciplinary collaborations, and sustainable initiatives are emerging as key areas of interest. The natural abundance and eco-friendly attributes of DE align with the growing emphasis on sustainability in energy solutions, and its contribution to electrode material synthesis for supercapacitors and batteries presents an exciting avenue to evolve energy storage technologies. Its intricate structures and bio-templating capabilities offer a compelling path for advancing sustainable, high-performance energy storage solutions, marking a significant step toward a greener and more efficient future.

Graphical Abstract

To increase storage capacity of supercapacitor nanomaterials plays an important role. By using different surfactants, it is possible to synthesize nanomaterials. Surfactants have power overgrowth and agglomeration of particles, which control the dimension of the materials. Doping of vanadium contributes to improvement the electric conductivity of nickel hydroxide. Compared with those of cetyltrimethylammonium bromide (CTAB) and ammonium fluoride (NH₄F), the restricted specific capacitance of these materials increases due to the use of the sodium lauryl sulphate (SDS) surfactant. The maximum specific capacitance was from a GCD of 2150 F g⁻¹ (1825 mF cm⁻²) at 3 mA cm⁻² and from a CV of 1844 F g⁻¹ at a 10 mV s⁻¹ scan rate. After 1000 charge‒discharge cycles, the electrode shows better stability at almost 95.5% at a scan rate of 100 mV s⁻¹. The diffusion and capacitive-controlled specific capacitance calculated with respect to different surfactants is a key aspect of this work.

The present work focuses on the structural, electrical, dielectric properties, transport properties, and ion dynamics of a polymer-salt-ceramic composite within a range of “ceramic-in-polymer” to “polymer-in-ceramic.” The polymer-salt-ceramic composite has been prepared using a solution cast method with PEO, LiCF₃SO₃, and different wt% of a cubic-LLZO ceramic. The lower 2θ shifts of PEO, X-ray diffraction peaks and prominent changes in CH₂ and C-O-C bond profile in the FT-IR spectra verify the Lewis acid-base interaction between ceramic filler and a polymer salt complex. Anion and ion pair peak profiles indicate an enhanced ion dissociation effect at 20 wt% ceramic loading in the polymer-salt-ceramic composite. Further, the highest room temperature DC conductivity of ~5.25 × 10⁻⁵ S/cm has been achieved for the same optimized composite sample. The relaxation and diffusion parameters indicate a faster ion migration facilitated by high ion dissociation at this optimum ceramic loading. Furthermore, the voltage and thermal stability of the polymer-salt-ceramic composites are significantly improved w.r.t. pristine polymer and polymer salt complex systems. The current study examines how C-LLZO can enhance ion migration and salt dissociation, as well as how these two processes together can affect DC conductivity measurements and other stability characteristics.

Among various energy storage devices, lithium-sulfur batteries are the most promising candidate due to their high energy density and low cost. Polysulfide migration is a severe problem to inhibit the wide application of lithium-sulfur batteries. The efficient polysulfide inhibition is a determining factor for the high electrochemical performance of lithium-sulfur batteries. Therefore, the development of suitable host materials can inhibit that polysulfide inhibition has become a hot topic of research. Herein, we propose that the C/MoS₂ composites can be used as sulfur host to catalyze the polysulfide conversion to improve the cycle stability of lithium-sulfur batteries. Thanks to the presence of the C/MoS₂ host, the as-prepared C/MoS₂@S cathode exhibits high capacity even at high rate of 5 C. This work provides direct evidence for the catalytic effect of C/MoS₂ for accelerating polysulfide conversion kinetics.