Lithium Ion Diffusion Coefficient Research Articles

Electrochemical in-situ lithiated Li2SiO3 layer promote high performance silicon anode for lithium-ion batteries

Si anode is considered to be one of the most promising candidates for the next-generation lithium-ion batteries (LIBs). However, the severe volume variation of Si (> 300%) during the lithiation/delithiation process results in unstable interface and thus contributes to poor cycling stability. Moreover, the relatively low conductivity derived from the semiconductor nature of Si leads to inferior rate performance. Herein, Li2SiO3 layer with fast lithium-ions transport capability and high mechanical property was formed on Si surface in an in-situ electrochemical method. The relationships between the valence of SiOx and LixSiOy constituents were readily studied. Fortunately, the as-prepared Si@ES-LSO showed great potential to mitigate the expansion and high lithium-ions diffusion coefficient. When employed as anode materials for LIBs, the modified Si anode delivered a specific capacity of 2074.8 mAh g−1 at 1000 mA g−1 with a retention ratio of 98.9% after 100 cycles, demonstrating superior electrochemical performance. This work provides a facial and efficient strategy for the roadmap of Si anode application.

N-doped LiNi0.65Co0.15Mn0.2O2 ternary cathode materials for improved electrochemical performance

LiNi0.65Co0.15Mn0.2O2 (NCM) has some advantages of high specific capacity, low cost, and environmental friendliness, but its high nickel content leads to serious cationic mixing and poor cycling and rate performance. The N doping LiNi0.65Co0.15Mn0.2O2 (NCM-x%N) is prepared by co-precipitation method. It is indicated by various representational means that N doping can reduce the particle size, effectively inhibit the cationic mixing degree, and increase lattice spacing. The means can improve the diffusion rate of lithium ions, among which N doping LiNi0.65Co0.15Mn0.2O2 (NCM-3%N) of x = 3 has the best electrochemical performance. After 100 cycles at 0.1C, the specific discharge capacity was 137.8 mA·h·g−1 (85.80 % capacity retention rate), which is 15.87 % higher than other NCM. The magnification performance is tested at 0.1C, 0.2C, 0.5C, 1C, and 2C. After 25 cycles, the capacity retention rate of NCM-3%N was 92.1 %, 11.11 % higher than that of NCM. Reaction kinetics showed that NCM-3%N has a lithium-ion diffusion coefficient that is higher than NCM.

Study on Two Inorganic Consumables in PMMA Electrochromic Devices Based on Work Function Differences

In electrochromic devices, the dielectric layer is not only an electrode dielectric, but also can provide compensating ions for electrochromism. In this paper, three composite porous materials, PMMA/SiO2, PMMA/TiO2, and PMMA/SiO2/TiO2, were prepared and assembled using polymethyl cellulose (PMMA) as the polymer matrix, impurity medium (SiO2) and titanium dioxide (TiO2) inorganic polymers, and the effect of doping two inorganic porous materials on the electrochromic performance was studied. The optical recovery and cycle stability of electrochromic wear of the PMMA/SiO2/TiO2 composite structure are significantly improved compared with the loss of other ceramic structures. Cyclic voltammetry analysis shows that the lithium ion diffusion coefficient of the electrochromic device using the PMMA/SiO2/TiO2 composite ceramic structure is the largest, which is 2.5 × 10−14 cm2​ s−1 . The improvement of electrochromic performance is mainly due to the difference in work function between SiO2 and TiO2 on the figure of merit diagram, which leads to the directional movement of the resonator, accelerates the transmission rate of Li+ and further optimizes the electrochemical properties of the composite ceramic. This study provides an effective method to improve the performance of electrochromic devices.

Si/Graphite@C Composite Fabricated by Electrostatic Self-Assembly and Following Thermal Treatment as an Anode Material for Lithium-Ion Battery.

Commercial graphite anode has advantages such as low potential platform, high electronic conductivity, and abundant reserves. However, its theoretical capacity is only 372 mA h g-1. High-energy lithium-ion batteries have been a research hotspot. The Si anode has an extremely high specific capacity, but its application is hindered by defects such as large volume changes, poor electronic conductivity, and a small lithium-ion diffusion coefficient. Here, the Si/thermally reduced graphite oxide@carbon (Si/RGtO@C) composite was fabricated by electrostatic self-assembly followed by thermal treatment. The RGtO synergistic carbon coating layer can effectively compensate for the low electronic conductivity and buffer the volume expansion effect of the Si nanoparticles during charge/discharge cycles. The Si/RGtO@C anode demonstrated a significantly increased capacity compared to the RGtO. After 300 cycles, Si/RGtO@C kept a discharged capacity of 367.6 mA h g-1 at a high current density of 1.0 A g-1. The Si/RGtO@C anode shows an application potential for commercial high-energy lithium-ion batteries.

Chelated Metal-Organic Frameworks for Improved the Performance of High-Nickel Cathodes in Lithium-Ion Batteries.

Lithium-ion batteries have gained widespread use in various applications, including portable devices, electric vehicles, and energy storage systems. High Ni cathode, LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1), have garnered significant attention owing to their high energy density. However, the limited lithium-ion transfer rate and transition metal cross-talk to anode pose obstacles to further improvement of electrochemical performance. To tackle these challenges, metal-organic frameworks (MOFs) with chelating agents are employed as additive materials for electrode. MOFs with chelating agents offer three key attributes: (1) Effective mitigation of transition metal cross-talk to the anode, (2) Partial desolvation of Li+ ions through MOF pores, and (3) Immobilization of anions via metal sites in the MOF. Leveraging these advantages, the chelating MOF-modified NCM cathode demonstrates reduced charge transfer resistance, both in their pristine and cycled states. In addition, they exhibit significantly improved lithium-ion diffusion coefficients after 100 cycles. These findings underscore the potential of MOFs with chelating agents as promising additive materials for enhancing the performance of LIBs.

PVP-assisted synthesis of NiSnO3 firmly anchored on graphene as a high-performance lithium battery: A combination of theoretical and experimental study.

Tiny NiSnO3 nanoparticles with the assistance of polyvinylpyrrolidone (PVP) are prepared to uniformly and stably "bond" on the surface of graphene to form a stable NiSnO3/RGO-PVP structure. At the same time, the excellent performance of lithium-ion batteries (LIBs) with the use of NiSnO3/RGO-PVP structure is verified through a dual combination of experiment and theory. The resulting NiSnO3/RGO-PVP structure enhanced the performance of LIBs with high cycling stability and better rate capability; even after undergoing rate performance tests at different high current densities, the NiSnO3/RGO-PVP electrode can still reach a capacity of 624 mA h g-1 at 200 mA g-1 after 400 cycles. The superior electrochemical performance of NiSnO3/RGO-PVP nanocomposites can be attributed to the synergistic effects between tiny NiSnO3 nanoparticles synthesized with the assistance of PVP and RGO, which can be verified through first-principles calculations based on DFT. The charge transfer between NiSnO3 and RGO through an electron density difference indicates a strong interaction between the two. Meanwhile, the low adsorption energies (-3.914, -0.77, and -0.65eV), low diffusion barriers (0.025, 0.49, and 0.141eV), and high diffusion coefficients (1.79 × 10-3, 5.38 × 10-11, and 2.97 × 10-5cm2s-1) of lithium ions at three different positions indicate the excellent rate performance of the NiSnO3/RGO-PVP heterostructure, which is consistent with experimental results. This work analyzes the excellent electrochemical performance of NiSnO3/RGO-PVP from the experimental results and supports the reliability of the experimental results through theoretical calculations.

Utilizing porous carbon composites based on biomass for lithium battery negative electrodes

This work used high-temperature calcination techniques along with basic chemical processing to produce a range of porous carbon compounds from biomass. After that, these substances were employed as anodes in lithium-ion batteries. The first hard carbon was produced via the dehydration reaction of strong sulfuric acid with sucrose (R-HC), then annealing in an NH3Ar environment was used to obtain the nitrogen-doped porous hard carbon (N-HC). Because N-HC has a high interlayer spacing (ca. 0.39 nm) and an abundant ultra-microporous structure (pore size < 0.75 nm), the lithium-ion diffusion coefficient in N-HC can reach up to 9.0 × 10−8 cm2.s−1. The obtained porous carbon compounds contain a rich pore structure, many functional groups, and a high specific surface area, according to the results. Following their application to the anode of lithium-ion batteries, they demonstrate favorable cycle stability and electrochemical performance. Furthermore, a detailed investigation into the kinetic characteristics of the lithium-ion diffusion behavior in the electrodes revealed that the porous carbon materials’ electrodes exhibited greater surface diffusion behavior for Li+.

Synthesis and Characterizations of Novel Copolymers with Zwitterionic Moiety-Based Solid Polymer Electrolytes for Solid-State Lithium Metal Battery

Electric vehicles (EVs) have become the dominant choice in the automotive industry, displacing internal combustion engine vehicles (ICEVs) to some extent. The development of high-efficiency batteries is essential to meet these market demands. Conventional lithium-ion batteries (LIBs), which consist of a cathode, anode, separator, and liquid electrolyte (such as 1M LiPF6 in carbonate solvents), have been widely utilized in portable electronic devices, hybrid electric vehicles (HEVs), and EVs. This popularity is attributed to their relatively high energy density and extended cycle life [1]. However, LIBs with energy density exceeding 240 Wh kg-1 face challenges in terms of thermal stability, potentially leading to fire and explosions by overcharging or accidental cell penetration. This drawback significantly hinders their application in automotive settings [2, 3]. In response to these safety concerns, there is a shift towards incorporating solid-state electrolytes (SSEs) as a replacement for liquid electrolytes. SSEs include solid polymer electrolyte (SPE), inorganic solid electrolyte (ISE), and composite polymer electrolyte (CPE).Solid-state lithium metal batteries (SSLMBs) incorporating SPE hold significant promise for advancing energy storage technologies due to their high energy density and improved safety features. However, the low ionic conductivity and ionic transference number of SPEs present challenges in their application for solid-state batteries. This work focuses on designing novel copolymers with polar soft unit and zwitterionic unit to address these challenges.In this study, poly(ethylene glycol) methyl ether acrylate (PEGMEA) and sulfobetaine methacrylate (SBMA) were selected as the polar soft segment and zwitterionic unit, respectively. Various ratios of PEGMEA/SBMA in copolymers were synthesized and characterized, and the resultant SPEs consisting of resultant copolymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared. Subsequently, their electrochemical, thermal, mechanical, and morphological properties were systematically investigated. The copolymers-based SPEs exhibited improved electrochemical properties. The optimized SPE comprising the copolymer with the molar ratio of PEGMEA/SBMA = 1/3 and 50 wt% LiTFSI exhibited the ionic conductivity of approx. 2×10–4 S cm–1, lithium-ion transference number of approx. 0.3, Li+ diffusion coefficient of 15×10-12 cm² s-1, and oxidation stability of 5.2 V (vs. Li/Li+) at 25 oC. Additionally, the mechanical properties of such SPEs were assessed, showing improved tensile strength (up to approx. 6 MPa) and Young’s modulus (up to approx. 83 MPa) with increasing SBMA content. The selected SPE with the best electrochemical properties was sandwiched between a Li metal electrode and a LiFePO4 electrode to assemble a SSLMB. As a result, the discharge capacity (DC) at 0.1 C-rate and room temperature was approx. 170 mA h g–1. Furthermore, the DC at a 0.5 C-rate was approx. 146 mA h g–1, and the capacity retention of 70% obtained after 470 cycles. In summary, this work demonstrates the potential of tailored copolymers with zwitterionic moiety-based SPEs for SSLMB. The comprehensive characterization and performance assessments provide valuable insights into the design and optimization of polymer electrolytes for next-generation energy storage systems.The copolymers and corresponding SPEs underwent characterization through various techniques such as DSC, SEM, XRD, and FTIR. The Ionic conductivity of the SPEs was determined by analyzing the results obtained from EIS measurement. The lithium-ion diffusion coefficient (DLi+) for SPE in a symmetric SSLMB cell, Li/SPE/Li, was also calculated based on the EIS results [4]. The oxidation stability window of the SPE was measured using the linear sweep voltammetry technique, and the ion transfer number was determined using the Evans-Vincent-Bruce method [5].

Extracting Thermodynamic, Kinetic, and Transport Properties from Batteries Using a Simple Analytical Pulsing Protocol

Gaining insights into the fundamental properties of lithium-ion batteries through scalable and non-destructive methods is challenging for commercial cell formats. In this work, a simple analytical pulsing protocol (APP) is performed on a commercial cell to understand its thermodynamic, kinetic, and mass transport properties. While testing procedures that rely on electrochemical pulses are well documented, the APP is novel in the level of fundamental insight that can be gained. For thermodynamics, a static-differential capacity analysis can be performed that removes the effects of kinetic and transport overpotentials and allows for the calculation of Gibbs free energy. For kinetics, the exchange current density of the cell can be calculated according to the Butler-Volmer model. For transport, a whole-cell lithium-ion diffusion coefficient can be calculated from a derivation of Fick’s second law and the generalized flux equation. Comparing the results from these properties gives an unparalleled level of mechanistic insight into battery performance from a single non-destructive technique. This APP requires no additional equipment and provides properties that can be easily correlated to materials or processing parameters. Therefore, the APP is valuable for research and development, manufacturing, quality assurance, and second-life applications, among others.

Introducing Ionic Transport Islands in Graphite Anode towards Fast-Charging Lithium-Ion Batteries

The development of lithium-ion batteries (LIBs) possessing excellent fast charging performance is particularly important for expanding the worldwide application market of LIBs. However, the grievous growth of lithium dendrites during high rate charging and discharging process occurring on the surface of the anode material still restricts the development of commercial fast charging LIBs, which raises capacity deterioration and even enormous safety risks. Herein, we developed simple physical mixing of active carbon (AC) powder into graphite negative slurry to generate the hybrid fast charging anode (called AS anode), which can realize unprecedented fast charging capability whether at room temperature or low temperature, along with greatly improved capacity retention cycling at high 2 C rate. Importantly, the density functional theory calculation and combined characterizations including in situ electrochemical confocal system spectroscopy and lithium ion (Li+) diffusion coefficient analysis can decipher that AC particles with rapid Li+ diffusion and adsorption can act as ion transport islands in graphite electrode to accelerate the transport process of lithium ion inside the whole negative electrode, leading to the faster charging performance. This work not only promotes the development of anode construction with fast charging capability for LIBs, but also deciphers the ion transport mechanism inside the electrode.

Optimization of LiNiCoMnO2 Cathode Material Synthesis Using Polyvinyl Alcohol Solution Method for Improved Lithium-Ion Batteries.

The growing need for lithium-ion batteries, fueled by the widespread use of electric vehicles (EVs) and portable electronic devices, requires high energy density and safety. The cathode material Li1-x(NiyCozMn1-y-z)O2 (NCM) shows promise, but attaining high efficiency necessitates optimization of both composition and manufacturing methods. Polycrystalline LiNiCoMnO2 powders were synthesized and assessed in this investigation using a polyvinyl alcohol (PVA) solution method. The study examined different synthesis conditions, such as the PVA to metal ions ratio and the molecular weight of PVA, to assess their influence on powder characteristics. Electrochemical analysis indicated that cathode materials synthesized with a relatively high quantity of PVA with a molecular weight of 98,000 exhibited the highest discharge capacity of 170.34 mAh/g and a high lithium-ion diffusion coefficient of 1.19 × 10-9 cm2/s. Moreover, decreasing the PVA content, irrespective of its molecular weight, led to the production of powders with reduced surface areas and increased pore sizes. The adjustments of PVA during synthesis resulted in pre-sintering observed during the synthesis process, which had an impact on the long-term stability of batteries. The electrodes produced from the synthesized powders had a positive impact on the insertion and extraction of Li+ ions, thereby improving the electrochemical performance of the batteries. This study reveals that cathode materials synthesized with a high quantity of PVA with a molecular weight of 98,000 exhibited the highest discharge capacity of 170.34 mAh/g and a high lithium-ion diffusion coefficient of 1.19 × 10-9 cm2/s. The findings underscore the significance of optimizing methods for synthesizing PVA-based materials to enhance the electrochemical properties of NCM cathode materials, contributing to the advancement of lithium-ion battery technology. The findings underscore the significance of optimizing methods for synthesizing PVA-based materials and their influence on the electrochemical properties of NCM cathode materials. This contributes to the continuous progress in lithium-ion battery technology.

Improving lithium deposition in porous electrodes: Phase field simulation

The development of structured lithium metal anodes is a key area of focus in the field of lithium battery research, which can significantly improve the energy density, cycle life and safety of lithium metal batteries. In this study, an electrochemical phase field model is used to construct the total free energy of the electrochemical system in conjunction with the effect of the porous electrode scaffold. It investigates the anisotropy of the diffusion coefficient of lithium ions in the electrolyte and the effect of the gradient size of the porous electrode scaffolds on the lithium deposition within the pores. Our numerical results show that increasing the diffusion coefficient of lithium ions in the x-direction cannot improve the lithium deposition within the pores. Instead, it leads to the appearance of lithium dendrites in the top layer of the porous electrode. Appropriately increasing the diffusion coefficient of lithium ions in the y-direction can significantly increase the lithium deposition capacity within the pores. However, excessive increases can lead to a reversal of the lithium deposition capacity within the pores. In addition, adopting the gradient size of the porous electrode scaffold in the y-direction can effectively alleviate the phenomenon that lithium metal is preferentially deposited at the top of the scaffold. These findings provide new ideas for the future design of structured lithium metal anode batteries.

Enhanced electrochemical performance of a LiFePO4 cathode with an environmentally friendly pectin/polyethylene glycol binder

The advancement of lithium-ion battery technology relies on the development of materials that not only improve performance but also align with environmental sustainability. This work presents a novel water-based pectin-PEG binder for LiFePO4 cathodes that combines eco-friendliness with electrochemical innovation. The binder material is made by mixing pectin, a flexible natural substance, with polyethylene glycol through a radical copolymerization process. This combination gives the binder both flexibility and a boost in electrical performance. Our experimental results demonstrate that LFP cathodes with this binder have an intriguing self-healing ability in comparison with the conventional PVDF binder, enhanced charge-discharge capacities, improved cycling stability, and higher ionic conductivity. Specifically, electrodes utilizing the pectin-PEG binder exhibit an impressive retention of discharge capacity. They maintain roughly 150 mAh g−1 after 500 cycles at 1C with 99% retention, and about 141 mAh g−1 with 97% retention at 3C. Cyclic voltammetry (CV) confirms that the PP binder maintains its ionic diffusion properties at high sweep rates, whereas galvanostatic intermittent titration technique reveals a much higher lithium ion diffusion coefficient (DLi+) within the operational voltage range of the LFP-PP250 electrodes. These findings establish an attractive direction for the development of electrodes for high-energy density, sustainable lithium-ion batteries.

Boosting Li-ion storage kinetics via constructing layered TiO2 anode

Due to the typical intercalation-deintercalation mechanism, TiO2 holds great promise as a sustainable anode for next-generation lithium-ion batteries (LIBs). However, commercial TiO2 (C–TiO2) is granular and shows slow ionic conductivity, which greatly hinders its development due to sluggish kinetics, leading to low reversible capacity and inferior rate capability. In this study, a two-dimensional layered TiO2 (L-TiO2) anode is prepared via a one-step calcination process, which can effectively shorten the lithium ions diffusion path and improve its lithium ions conductivity. We elucidated the enhanced electrochemical performance of L-TiO2 as an anode in LIBs through pseudocapacitive acceleration of lithium ions intercalation and deintercalation using various characterization techniques, including different scan rate cyclic voltammetry tests, in situ electrochemical impedance spectroscopy, in situ Raman spectroscopy, and in situ X-ray diffraction. In comparison to C–TiO2 material, L-TiO2 material showcases remarkable electrochemical performance, achieving a capacity of 166 mAh/g after 100 cycles at 0.1 C. Additionally, the lithium-ion diffusion coefficient calculated for the L-TiO2 is two orders of magnitude greater, underscoring its potential as a negative electrode material for LIBs.

Synergistic effect of hydrogen bond and carbon coating to suppress the capacity and voltage fading in Li-Rich cathode

The voltage and capacity degradation of high-capacity Li-rich Mn-based (LRM) batteries during cycling have been a formidable barrier to their commercial application. In this study, a modified material coated with 15 nm-thick hydroxy-rich carbon layer (C-LRM) is synthesized by hydrothermal method, and C-LRM-PAA electrode is assembled by combining C-LRM with LiPAA binder. The strong hydrogen bond formed by the rich carboxyl group in LiPAA and the hydroxyl group in C-LRM makes the components of the C-LRM-PAA electrode closely connected to avoid electrode cracking, and the coating of the carbon layer avoids the cracking of the cathode particles. Consequently, this unique combination successfully inhibits transition metal dissolution, diminishes charge transfer impedance, and augments the lithium-ion diffusion coefficient, all of which contribute to suppressing the capacity and voltage attenuation. The electrochemical performance shows that after 200 cycles at 1C, the capacity retention rate increases from 40.8 % to 75.5 %, and the voltage decay rate decreases from 2.925 mV per cycle to 2.135 mV per cycle. This provides a new perspective for the electrode design of high energy density LRM batteries.

Improved electrochemical performance of Cu-Sn/nano-SiO2 composite anode materials for lithium-ion batteries fabricated by controlled electrodeposition

Cu-Sn/nano-SiO2 composite materials are fabricated through electrodeposition process coupled with precise thermal treatment, which employs hexadecyl trimethyl ammonium bromide to guarantee the even distribution of nano-SiO2 particles within the Cu-Sn alloy framework. The characterization results indicate that integrating nano-SiO2 into the Cu-Sn matrix effectively prevents active particles from detaching from the copper foil current collector. By adjusting the current density, the electrochemical performance of the Cu-Sn/nano-SiO2 composite electrode is significantly enhanced. Specifically, the initial charge and discharge specific capacities of the composite electrolyte are approximately 746.6 and 1470.8 mAh/g at 100 mA/g, respectively. Moreover, the cell can still maintain a discharge specific capacity of 358.6 mAh/g after 100 cycles. Furthermore, the cell demonstrates an improved lithium-ion diffusion coefficient of approximately 9.639 × 10–15 cm²/s and a lower transfer resistance of 54.65 Ω. Therefore, a direct approach of fabricating the Cu-Sn/nano-SiO2 composite electrode with enhanced electrochemical properties may provide valuable guidance for alloy anodes in the energy storage field.

Mo-doping modulated cationic vacancy in Zn3V2O8 with enhanced electrochemical performance for lithium-ion batteries

Given diverse redox reactions and abundant raw materials, Zn3V2O8 with high specific capacity is considered as a potential anode material for lithium-ion batteries. Same as other transition metal oxides, Zn3V2O8 suffers from infertile conductivity, sluggish ion diffusion and fast capacity loss derived from volume expansion during discharge/charge process, further hindering its application. In this work, a novel Mo doped Zn3V2O8 (Zn3V2-xMo5x/6O8) anode material with cationic vacancy (V vacancy) has been designed through a facile sol-gel method. It is found that a small Mo-doping amount has nearly no influence on the crystal structure, morphology and element valence states of Zn3V2O8. Mo doped Zn3V2O8 samples possess smaller charge transfer resistance and higher lithium ion diffusion coefficient. The results of electrochemical performance illustrate that Mo doped Zn3V2O8 can deliver higher reversible specific capacities and better rate capability compared with Zn3V2O8, which can be ascribed to the introduction of V vacancy. In particular, when Mo-doping amount is set as 0.03, the obtained Zn3V1.97Mo0.025O8 exhibits a reversible capacity of 481.1 mAh g−1 after 600 cycles at 1 A g−1. It is believed that this work could provide an effective and feasible strategy to construct high performance transition metal vanadate anode materials for lithium-ion batteries.

Effects of Ti4+ doping on electrochemical properties of LiNi0.815Co0.15Al0.035O2 cathode materials

The high nickel ternary cathode materials LiNi0.815Co0.15Al0.035O2 (NCA) have been widely used in Li-ion batteries due to their high energy density, low cost, and little environmental pollution. However, it suffers from rapid capacity degradation and poor charging rate. In this work, Ti4+ doping NCA cathode materials are prepared by the high-temperature solid-state method. The results show that 0.5%Ti-NCA has a lower cationic mixing degree and better cycling performance. The capacity retention rate of 100 cycles is 98.91% and 96.59% at current densities of 0.5 C and 1.0 C, respectively. The CV and EIS test results show that 0.5%Ti-NCA has lower polarization and higher lithium ion diffusion coefficient DLi+(8.43×10−14 cm2/S) after 100 cycles, while Pure-NCA only has 6.92×10−15 cm2/S, which effectively enhances the electrochemical properties of NCA cathode materials.

Comprehensive Study of Ti and Ta Co-Doping in Ni-Rich Cathode Material LiNi0.8Mn0.1Co0.1O2 Towards Improving the Electrochemical Performance.

Layered Ni-rich oxides (LiNi1-x-yCoxMnyO2) cathode materials are of current interest in high-energy-demanding applications, such as electric vehicles because of high discharge capacity and high intercalation potential. Here, the effect of co-doping a small amount of Ti and Ta on the crystal structure, morphology, and electrochemical properties of high Ni-rich cathode material LiNi0.8Mn0.1Co0.1-x-yTixTayO2 (0.0≤x+y≤0.2) was systematically investigated. This work demonstrates that an optimum level of Ti and Ta doping is beneficial towards enhancing electrochemical performance. The optimal Ti4+ and Ta5+ co-doped cathode LiNi0.8Mn0.1Co0.09Ti0.005Ta0.005O2 exhibits a superior initial discharge capacity of 161.1 mAh g-1 at 1 C, and excellent capacity retention of 87.1 % after 250 cycles, compared to the pristine sample that exhibits only 59.8 % capacity retention. Moreover, the lithium-ion diffusion coefficients for the co-doped cathode after the 3rd and 50th cycles are 9.9×10-10 cm2 s-1 and 9.3×10-10 cm2 s-1 respectively, which is higher than that of the pristine cathode (3.3×10-10 cm2 s-1 and 2.5×10-10 cm2 s-1 respectively). Based on these studies, we conclude that Ti and Ta co-doping enhances structural stability by mitigating irreversible phase transformation, improving Li-ion kinetics by expanding interlayer spacing, and nanosizing primary particles, thereby stabilizing high-nickel cathode materials and significantly enhancing cyclability.

Thermal Studies of Lithium-Ion Cells: Ensuring Safe and Efficient Energy Storage

This work investigated the impact of temperature on the diffusion of lithium ions within cells. To achieve this, electrochemical impedance spectroscopy (EIS) analysis was conducted at various temperatures across three distinct cells. These cells utilized an electrode composed of corn starch meringue and were paired with three different electrolytes. Notably, one electrolyte included an additional 5% of starch. The objective of this study extends beyond merely determining resistance from graphical representations; it also entails performing a kinetic analysis of specific systems, with a particular emphasis on elucidating the significance of the lithium-ion diffusion coefficient as a critical parameter. The cell with 1 M LiPF6 in the EC/DMC/DEC electrolyte and corn starch-based electrode exhibited the most horizontally oriented Warburg curve, representing the smallest angle.