Li-ion Diffusion Research Articles

Facile synthesis of N-doped porous CoO@C nanocubes as anode with superior lithium storage

N-doped porous CoO@C nanocubes were fabricated using a hydrothermal method and annealing process. The uniform wrapped carbon layer effectively mitigates the volume changes during electrochemical reactions. Moreover, the porous carbon layer enhances the electrical conductivity and promotes Li ion diffusion. Therefore, the as-prepared CoO@C nanocubes maintian a capacity of 565 mA h/g at 0.2 A/g after 100 cycles. This stabilization ability is attributed to the introduction of carbon layer and its porous structure, which buffers the volume expansion of cobalt oxide, and increases the surface area and active sites.

Effect of Mo6+ induced valence changes of transition metal ions in Mn-rich layered cathode materials on electrochemical performance

Layered cathode materials for lithium-ion batteries have been extensively investigated; however, comparatively scant attention has been paid to Mn-rich layered cathode materials. Herein, LiNi0.5Mn0.5O2 cathode materials are doped to investigate the effect of doping elements on the electrochemical properties of Mn-rich layered cathodes. XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), and SQUID (superconducting quantum interference device) results reveal that Mo doping affects the electrochemical properties of the cathode materials by changing the valence state of transition metal ions. Due to the Mo6+ ions doping, a large proportion of Mn3+ ions present in LiNi0.5Mn0.5O2 were converted to Mn4+ ions, which alleviated the Jahn-Teller effect and reduced the elongated Mn-O octahedra, thus increasing the Li layer spacing and facilitating Li+ diffusion. Therefore, 1 % Mo-doped cathode exhibits a significantly improved Li-ion diffusion coefficient and superior rate performance with a specific discharge capacity of 103 mAh·g−1 at 5C. Meanwhile, the cathode materials significantly improve cycling performance due to the reduction in the amount of Mn3+. The current study provides guidelines for the modification of Mn-rich layered cathodes in the future.

In-Plane Mesoporous 3D Flower-Like Mo2Ti2C3Clx MXene Anodes for Li-Ion Batteries: From Structure to Performance.

MXenes are known for their exceptional electrical conductivity and surface functionality, gaining interest as promising anode materials for Li-ion batteries. However, conventional 2D multilayered MXenes often exhibit limited electrochemical applicability due to slow ion transport kinetics and low structural stability. Addressing these challenges, this study develops a 3D flower-type double transition metal MXene, Mo2Ti2C3Clx, with precisely engineered in-plane mesoporosity using HF-free Lewis acid-assisted molten salt method, coupled with intercalation and freeze-drying. The molar ratio of Lewis acid to eutectic salts is meticulously controlled to create the mesoporosity, which is preserved through freeze-drying. Molecular dynamics (MD) simulations assess the impact of in-plane pore size on the structure and transport dynamics of electrolyte components. Density functional theory (DFT) shows that chlorine surface functional groups significantly reduce Li-ion diffusion barriers, thereby enhancing ion transport and battery performance. Electrochemical evaluations reveal that small-sized (2-5nm) mesoporous Mo2Ti2C3Clx achieves a specific capacity of 324 mAh g-1 at 0.2 A g-1 and maintains 97% capacity after 500 cycles at 0.5 A g-1, outperforming larger-pored (10nm) and non-porous variants. This research highlights a scalable strategy for designing mesoporous materials that optimize ion transport and structural stability, essential for advancing next-generation high-performance energy storage solutions.

LiF modified hard carbon from date seeds as an anode material for enhanced low-temperature lithium-ion batteries

The performance of traditional Li-ion batteries deteriorates when operating at sub-zero temperatures mainly due to the slow diffusion of Li-ions in commercial negative electrode materials. Various alternative anodes have been explored, but complex fabrication methods hinder practical implementation. This work proposes a cost-effective anode material, a porous structured nitrogen-doped hard carbon synthesized from date seeds with further LiF modification to achieve an artificial LiF-rich solid electrolyte interphase (SEI) layer. The resulting anode material showcases promising characteristics, achieving a specific capacity of 525 mAh g−1 after 50 cycles at room temperature. Furthermore, it maintains a substantial capacity of 280 mAh g−1 after 100 cycles at −20 °C. Notably, even when subjected to a high current of 2C at −20 °C, the electrode still provides a remarkable capacity of 72 mAh g−1 after 500 cycles. The outstanding charge storage performance at low temperatures is attributed to the predominance of capacitance-controlled charge storage mechanisms in the prepared anode. Post-mortem analysis confirms structural stability and formation of a uniform LiF-rich SEI layer. This novel approach presents a practical solution to the difficulties encountered by LIBs in cold environments, paving the way for improved battery performance and longevity.

Evolution of Lithium Metal Anode Along Cycling in Working Lithium–Sulfur Batteries

AbstractThe cycling lifespan of high‐energy‐density lithium–sulfur (Li–S) batteries is dominantly limited by the rapid failure of Li metal anodes. Herein, the evolution of Li metal anode along cycling is systematically investigated in Li–S batteries to clarify the Li plating and stripping behaviors, the generation and accumulation of inactive Li, and the failure mechanism of Li metal anodes. Concretely, plated Li strips preferentially than bulk Li to leave massive stripping Li shells during initial discharge, and the stripping Li shells are refilled by plated Li during the subsequent charge to generate thick Li dendrites. During the following cycles, inactive Li generates and accumulates on top of bulk Li due to solid electrolyte interphase formation and incomplete removal of plated Li. Eventually, the accumulation of inactive Li hinders the diffusion of Li ions through the inactive Li layer to induce cell polarization at the end of the second discharge plateau and rapid decay of discharge capacity. This work elucidates the detailed evolution mechanism of Li metal anode along cycling in working Li–S batteries and highlights the reactivation of inactive Li as an effective strategy to prolong the cycling lifespan of Li–S batteries.

Post-mortem study and long cycling stability of silica/carbon composite as anode in Li-ion cells

The present work emphases on the post-mortem study of silica/carbon composite as functional anode in Li-ion batteries (LIBs). Herein, the silica/carbon composite is synthesized by facile in-situ hydrothermal technique. The x-ray diffraction (XRD) pattern indicates the amorphous nature of silica/carbon composite. The stacked sheet-like morphology of silica/carbon composite is seen in the high-resolution transmission electron microscopy (HR-TEM) & scanning electron microscopy (SEM) images. In addition, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, energy dispersive x-ray analysis (EDAX), and x-ray photoelectron spectra (XPS) characterizations of silica/carbon composite has been studied in detail. The rate capability of silica/carbon composite anode in LIB indicates 99% capacity retention after applying current density ranging from 50 mA g−1 to 1000 mA g−1, successively. The composite anode delivers a stable specific capacity ∼300 mAh g−1 at a current density of 100 mA g−1 for 500 cycles. Electrochemical impedance spectroscopy (EIS) study analyzed the faster Li-ion diffusion and increment in the diffusion coefficient by a factor of 1000 after 500 cycles. To the best of our knowledge, this is the first work on the post-mortem study of silica/carbon composite as anode in LIB. Post-cycling characterizations including XRD, FTIR, and SEM reveal the absence of any impurity phases and negligible volumetric expansion after prolonged cycling. It further confirms that the carbon present in the silica/carbon composite helps to accommodate the volumetric expansion of silica and prevents cracking of the anode over 500 cycles.

Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes.

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

Dual-Function Alloying Nitrate Additives Stabilize Fast-Charging Lithium Metal Batteries.

Lithium metal is regarded as the "holy grail" of lithium-ion battery anodes due to its exceptionally high theoretical capacity (3800 mAh g-1) and lowest possible electrochemical potential (-3.04 V vs Li/Li+); however, lithium suffers from the dendritic formation that leads to parasitic reactions and cell failure. In this work, we stabilize fast-charging lithium metal plating/stripping with dual-function alloying M-nitrate additives (M: Ag, Bi, Ga, In, and Zn). First, lithium metal reduces M, forming lithiophilic alloys for dense Li nucleation. Additionally, nitrates form ionically conductive and mechanically stable Li3N and LiNxOy, enhancing Li-ion diffusion through the passivation layer. Notably, Zn-protected cells demonstrate electrochemically stable Li||Li cycling for 750+ cycles (2.0 mA cm-2) and 140 cycles (10.0 mA cm-2). Moreover, Zn-protected Li||Lithium Iron Phosphate full-cells achieve 134 mAh g-1 (89.2% capacity retention) after 400 cycles (C/2). This work investigates a promising solution to stabilize lithium metal plating/stripping for fast-charging lithium metal batteries.

Lithiophilic Multichannel Layer to Simultaneously Control the Li-Ion Flux and Li Nucleation for Stable Lithium Metal Batteries.

Although the Li metal has been gaining attention as a promising anode material for the next-generation high-energy-density rechargeable batteries owing to its high theoretical specific capacity (3860 mAh g-1), its practical use remains challenging owing to inherent issues related to Li nucleation and growth. This paper reports the fabrication of a lithiophilic multichannel layer (LML) that enables the simultaneous control of Li nucleation and growth in Li-metal batteries. The LML, composed of lithiophilic ceramic composite nanoparticles (Ag-plated Al2O3 particles), is fabricated using the electroless plating method. This LML provides numerous channels for a uniform Li-ion diffusion on a nonwoven separator. Furthermore, the lithiophilic Ag on the Li metal anode surface facing the LML induces a low overpotential during Li nucleation, resulting in a dense Li deposition. The LML enables the LiNi0.8Co0.1Mn0.1O2|| Li cells to maintain a capacity higher than 75% after 100 cycles, even at high charge/discharge rates of 5.0 C at a cutoff voltage of 4.4 V, and achieve an ultrahigh energy density of 1164 Wh kg-1. These results demonstrate that the LML is a promising solution enabling the application of Li metal as an anode material in the next-generation Li-ion batteries.

Enhancing electrochemical kinetics in electrophoretic-deposited lithium iron phosphate Li-metal batteries through additives

This study demonstrates that the introduction of additives into the Electrophoretic Deposition (EPD) process significantly enhances the electrochemical performance of Lithium Iron Phosphate (LFP) electrodes. Incorporating these additives resulted in achieving a battery capacity of around 100 mAh/g at a 2 C rate, demonstrating a significantly higher capacity compared to configurations without additives. The additives enhance the surface capacitive effect, thus improving the efficiency of energy storage. This performance boost is attributed to a carefully optimized mixture of binders and conductive agents, resulting in a denser electrode surface. Such a surface facilitates improved Li-ion diffusion and capacitive charge storage, leading to enhanced electrochemical kinetics. These developments highlight the efficacy of the EPD method in advancing LFP electrode technology, providing a significant improvement in performance by enabling pseudocapacitive behavior and better Li-ion transport. Our findings suggest promising avenues for the evolution of future battery technologies, marking a notable step forward in electrode fabrication methods.

Kinetically accelerated lithium storage in (LiFeCoNiMnCr)2O3 enabled by hollow multishelled structure, oxygen vacancies and high entropy engineering

High-entropy oxides (HEOs) are attractive for lithium-ion batteries (LIBs) owing to their extensive component scope and regulatable electrochemical performance. However, their own the sluggish kinetics hinder their large-scale application. The modification including adjusting the intrinsic activity and structural design is required to compensate for their inherent shortcomings. Here, oxygen vacancies with goal capability are brought in a special hollow multishelled (LiFeCoNiMnCr)2O3 spheres (Li-HEO-HoMS) through an in-situ formed carbonaceous microspheres as templates coupled with the kirkendall effect to expedite the ion/electron transportation and increase structure/electrochemistry stability. Theory combined with experiment reveal the feasible promotion of Li-ions storage, charge transfer, diffusion dynamics and long-term stability from hollow multishelled sphere structure, oxygen vacancies and entropy-stabilizing effect, which conclusively generates reinforced electrochemical performance. Benefit from these synergistic attributes, the Li-HEO-HoMS exhibits outstanding electrochemical property for LIBs with 767.7 mAh g−1 at 1 A g−1 after 500 cycles and still shows a specific capacity of 443.1 mAh g−1 at a high rate of 4 C. The strategy demonstrates the importance of the intrinsic activity and structural design of HEO in tailoring the electrochemical performance.

Inducing and Understanding Pseudocapacitive Behavior in an Electrophoretically Deposited Lithium Iron Phosphate Li-Metal Battery as an Electrochemical Test Platform.

Our study has effectively employed electrophoretic deposition (EPD) using AC voltage to develop a lithium iron phosphate (LFP) Li-ion battery featuring pseudocapacitive properties and improved high C-rate performance. This method has significantly improved the battery's specific capacity, achieving an impressive 100 mAhg-1 at a 5 C discharge rate, which showcases its superior high-rate capability. Additionally, the battery displayed excellent reversibility during its performance cycles. These results confirm the EPD method's efficacy in improving LFP electrode performance, yielding notable improvements in cycling stability and high-rate capability. The enhanced capacity and high-rate performance of the electrophoretic-deposited LFP electrodes are largely due to the fast kinetics facilitated by pseudocapacitive behavior-induced charge storage and a high Li-ion diffusion constant measured in our EPD-deposited LFP electrodes. This underscores the practicality of our approach and the development of a fundamental test platform to investigate the pseudocapacitive charge storage mechanism in electrodes with typical battery-like behavior.

Influence of Polypyrrole on Phosphorus- and TiO2-Based Anode Nanomaterials for Li-Ion Batteries.

Phosphorus (P) and TiO2 have been extensively studied as anode materials for lithium-ion batteries (LIBs) due to their high specific capacities. However, P is limited by low electrical conductivity and significant volume changes during charge and discharge cycles, while TiO2 is hindered by low electrical conductivity and slow Li-ion diffusion. To address these issues, we synthesized organic-inorganic hybrid anode materials of P-polypyrrole (PPy) and TiO2-PPy, through in situ polymerization of pyrrole monomer in the presence of the nanoscale inorganic materials. These hybrid anode materials showed higher cycling stability and capacity compared to pure P and TiO2. The enhancements are attributed to the electrical conductivity and flexibility of PPy polymers, which improve the conductivity of the anode materials and effectively buffer volume changes to sustain structural integrity during the charge and discharge processes. Additionally, PPy can undergo polymerization to form multi-component composites for anode materials. In this study, we successfully synthesized a ternary composite anode material, P-TiO2-PPy, achieving a capacity of up to 1763 mAh/g over 1000 cycles.

Can Electrochemical Impedance Spectroscopy be Replaced by Direct Current Techniques in Battery Diagnosis?

Electrochemical impedance spectroscopy (EIS), a conventional and alternating-current-(AC)-based technique for impedance measurement, is commonly used in battery diagnosis. However, it requires expensive equipment and demanding operating conditions and is complex and model-dependent in data analysis. Recently, novel direct current (DC) analytics have emerged as an alternative to EIS. They are simple yet powerful, being capable of revealing impedance information that traditionally could only be obtained through EIS and determining Li-ion diffusion coefficient. Besides, a complete EIS spectrum can be predicted based on constant current charging curves in the support of machine learning methods. This work highlights the similarities and discrepancies between DC techniques and EIS in the electrochemical analysis of Li-ion batteries. Looking ahead, DC techniques may be a promising substitute for EIS in future battery diagnosis, requiring simplified equipment while offering a deep understanding of battery impedance and its underlying electrochemical processes.

Improved cycle capability of Mn-doped Fe2TiO5 anode for lithium-ion batteries

Good cycling stability and high theoretical capacity are provided by Fe2TiO5 (iron titanate) as an electrode material due to its distinct crystal structure and numerous redox couples. The conventional ceramic method successfully and effectively synthesises the material. This study discloses the successful doping and replacement of Ti4+ with Mn4+ in the unit cell of Fe2TiO5 pseudobrookite, resulting in decreased band gap energy and a regular increase in unit cell volume with increased Mn-concentration. Doping improves the overall electrical conductivity due to a higher ratio of Ti3+ to Ti4+ which ultimately boosts the electrochemical performance as an anode in LIBs application. The Fe2Ti1-xMnxO5 (x = 0.2) achieves a high specific surface area of 338.6 m2 g−1 with an average pore size distribution of ∼10 nm, which is beneficial to reduce the Li-ion diffusion path and provides large contact areas between electrolyte and electrode surface. The Fe2Ti1-xMnxO5 (x = 0.2) stays ahead in its electrochemical performance compared to all counter partners delivering 765.6 mAh g−1 of initial discharge capacity and having a capacity retention of 392.3 mAh g−1 after 100 continuous charge discharge cycles at a current density of 100 mA g−1. Additionally, an excellent rate performance of 327.9 mAh g−1 is observed even at 5000 mA g−1. No further capacity fading is noted for another 45 cycles, demonstrating the structural stability of electrode material at variable current densities. The superior electrochemical results of Mn4+ doped Fe2TiO5 manifestly show the possibility of serving as an electrode material for high-performance battery applications.

Nano-silicon embedded in 3D honeycomb carbon frameworks as a high-performance lithium-ion-battery anode

The fabrication of three-dimensional (3D) honeycomb carbon frameworks, incorporating embedded silicon (Si) nanoparticles (NPs), is successfully achieved through a facile method involving mixing, carbonization, and acid pickling. The as-prepared Si@PVPC composites exhibit excellent electrochemical performances due to reasons as follows. (1) Honeycomb channels supply enough space to accommodate the expansion of Si NPs and so structural integrity of 3D honeycomb carbon frameworks are maintained during lithiation/delithiation processes. (2) Honeycomb channels offers fast transfer paths for Li-ion diffusion. (3) 3D carbon frameworks afford reliable and stable electric contact points. As a result, Si@PVPC electrodes show a capacity of 1294.3 mAh g−1 at 2 A g−1 after 1400 cycles with a capacity retention of 85.5 %. Even at an ultrahigh current of 16 A g−1, Si@PVPC electrodes still show a capacity of 619.6 mAh g−1.

Superior fast-charging Ni-rich cathode via promoted kinetic-mechanical performance

The sluggish Li-ion kinetics restrict the rapid charging capabilities and contribute to the structural deterioration of Ni-rich cathode materials. Notably, crack propagation during repeated charging cycles deteriorates the electrochemical stability, which hinders the further development of high-energy-density batteries for electric vehicles (EVs). In this paper, we proposed a simple yet effective method to enhance the Li-ion diffusion and mechanical properties of Ni-rich cathodes via straightforward Zr doping. In-situ high-rate XRD reveals that the detrimental uneven delithiation under the fast-charging process has been largely alleviated. Particularly, a robust structure with higher modulus and fracture strength is constructed owing to the higher Zr-O bond. By mitigating the kinetic hindrance and increasing the particle’s stiffness, the proposed Ni-rich cathode shows an impressive 97.6 % capacity retention under a 5 C rate current. This work provides a facile and efficient strategy for large-scale production of fast-charging Ni-rich cathode materials.

Nb2C and Nb2CO2 MXenes as Anodes in Li-Ion Batteries: A Comparative Study by First-Principles Calculations.

The new generation of Li-ion batteries is based on integrating 2D materials into the electrodes to increase the energy density while reducing the charging time and size. The two-dimensional transition metal carbide or nitride (MXene) materials offer ideal electronic properties, such as metallic behavior, low energy barriers for Li-ion diffusion, and structural stability. This study focuses on Nb2C and Nb2CO2 MXenes, which have shown promising Li-storage capacity, especially the oxidized phase. By using density functional theory (DFT) and thermodynamic criteria, we studied the Li intercalation process in both MXenes. The results show that the Li intercalation process in the oxidized phase is more stable. Also, the Li diffusion barriers are 35 and 250 meV for the bare and oxidized phase, due to the strong interaction between Li ions and O functional groups. Nb2C and Nb2CO2 MXenes deliver a maximum gravimetric theoretical capacity of 275 and 233.26 mA h/g, respectively, with a stable performance.

Effects of different Ti concentrations doping on Li2MnO3 cathode material for lithium-ion batteries via density functional theory

Li2MnO3 is extensively studied for a cathode material in lithium-ion batteries because of its high voltage and specific capacity. Nevertheless, it has the disadvantages due to low conductivity and Li-ion diffusion. To modify its performance, we determine the structure stability and electronic properties of Li2MnO3 cathodes doped with different Ti-ion concentrations using the spin-polarized density functional theory including the Hubbard term (DFT + U). For the calculations, cell parameters, formation energies, band gaps, total density of states, partial density of states and stability voltages are determined. The results highlight that the expansion of the cell volumes by Ti-ion impurities has a positive effect on the diffusion of Li ions in these cathodes. Because of the minor voltage changes, Li2MnO3 cathode doped with a Ti-ion concentration of 0.250 exhibits the highest voltage stability. Overall, these results are effective for the lithium-ion battery application based on Ti-doped Li2MnO3 cathodes.

Two-Dimensional Transition Metal Phosphides As Cathode Additive in Robust Lithium-Sulfur Batteries.

The development of advanced cathode materials able to promote the sluggish redox kinetics of polysulfides is crucial to bringing lithium-sulfur batteries to the market. Herein, two electrode materials: namely, Zr2PS2 and Zr2PTe2, are identified through screening several hundred thousand compositions in the Inorganic Crystal Structure Database. First-principles calculations are performed on these two materials. These structures are similar to that of the classical MXenes. Concurrently, calculations show that Zr2PS2 and Zr2PTe2 possess high electrical conductivity, promote Li ion diffusion, and have excellent electrocatalytic activity for the Li-S reaction and particularly for the Li2S decomposition. Besides, the mechanisms behind the excellent predicted performance of Zr2PS2 and Zr2PTe2 are elucidated through electron localization function, charge density difference, and localized orbital locator. This work not only identifies two candidate sulfur cathode additives but may also serve as a reference for the identification of additional electrode materials in new generations of batteries, particularly in sulfur cathodes.