Synthesis, characterisation and electrochemical intercalation kinetics of nanostructured aluminium-doped Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode material for lithium ion battery

Enhancing the Cycling and Rate Performance of NaNi1/3Fe1/3Mn1/3O2 Cathodes by La/Al Codoping

O3-type layered oxides hold significant promise as the material for cathodes in sodium-ion batteries for their favorable electrochemical properties, while irreversible structural degradation and harmful phase transitions during cyclic operation limit the practical application of these materials. In this work, we proposed a La3+/Al3+ codoping strategy in O3-Na(Ni1/3Mn1/3Fe1/3)O2 cathode materials and found that batteries with the Na (Ni1/3Mn1/3Fe1/3)0.998La0.001Al0.001O2 (NFM-La/Al) cathodes exhibited not only promoted capacity from 135.80 to 170.42 mAh g-1 at 0.2 C but also significantly enhanced cycling stability, with a 10% improvement in capacity retention compared with NFM cathodes after 300 cycles. Particularly, their rate performance was significantly improved as well. XRD and XPS tests indicated that La could expand the c-axis of NFM due to its larger ionic radius and thus significantly increased Na+ ion diffusion efficiency, and in addition, Al doping could effectively increase the content of Ni2+ and Mn4+ and thus greatly alleviated the negative Jahn-Teller effect caused by Mn3+. Moreover, consistent with XRD analyses, DFT calculations further substantiated the effectiveness of the La/Al codoping strategy by demonstrating the detailed atom substitution mechanism in the NFM crystal lattice. The boosted structure stability and Na+ diffusion kinetics may enhance the potential for practical applications of O3-type oxide cathodes.

Electrolysis Process-Facilitated Engineering of Primary Particles of Cobalt-Free LiNiO2 for Improved Electrochemical Performance

The particle morphology of LiNiO2 (LNO), the final product of Co-free high-Ni layered oxide cathode materials, must be engineered to prevent the degradation of electrochemical performance caused by the H2-H3 phase transition. Introducing a small amount of dopant oxides (Nb2O5 as an example) during the electrolysis synthesis of the Ni(OH)2 precursor facilitates the engineering of the primary particles of LNO, which is quick, simple, and inexpensive. In addition to the low concentration of Nb that entered the lattice structure, a combination of advanced characterizations indicates that the obtained LNO cathode material contains a high concentration of Nb in the primary particle boundaries in the form of lithium niobium oxide. This electrolysis method facilitated LNO (EMF-LNO) engineering successfully, reducing primary particle size and increasing particle packing density. Therefore, the EMF-LNO cathode material with engineered morphology exhibited increased mechanical strength and electrical contact, blocked electrolyte penetration during cycling, and reduced the H2-H3 phase transition effects.

Impacts of Mg doping on the structural properties and degradation mechanisms of a Li and Mn rich layered oxide cathode for lithium-ion batteries

The Li- and Mn-rich layered oxide cathode material class is a promising cathode material type for high energy density lithium-ion batteries. However, this cathode material type suffers from layer to spinel structural transition during electrochemical cycling, resulting in energy density losses during repeated cycling. Thus, improving structural stability is an essential key for developing this cathode material family. Elemental doping is a useful strategy to improve the structural properties of cathode materials. This work examines the influences of Mg doping on the structural characteristics and degradation mechanisms of a Li_1.2Mn_0.4Co_0.4O₂ cathode material. The results reveal that the prepared cathode materials are a composite, exhibiting phase separation of the Li₂MnO₃ and LiCoO₂ components. Li₂MnO₃ and LiCoO₂ domain sizes decreased as Mg content increased, altering the electrochemical mechanisms of the cathode materials. Moreover, Mg doping can retard phase transition, resulting in reduced structural degradation. Li_1.2Mn_0.36Mg_0.04Co_0.4O₂ with optimal Mg doping demonstrated improved electrochemical performance. The current work provides deeper understanding about the roles of Mg doping on the structural characteristics and degradation mechanisms of Li-and Mn-rich layered oxide cathode materials, which is an insightful guideline for the future development of high energy density cathode materials for lithium-ion batteries.

Exploring the Effect of a MnO2 Coating on the Electrochemical Performance of a Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

The effect of electrochemically active MnO2 as a coating material on the electrochemical properties of a Li1.2Mn0.54Ni0.13Co0.13O2 (LTMO) cathode material is explored in this article. The structural analysis indicated that the layered structure of the LTMO was unchanged after the modification with MnO2. The morphology inspection demonstrated that the rod-like LTMO particles were encapsulated by a compact coating layer. The MnO2 layer was able to hinder the electrolyte solution from corroding the LTMO particles and optimized the formation of a solid electrolyte interface (SEI). Meanwhile, lithium ions were reversibly inserted into and extracted from MnO2, which afforded an additional capacity. Compared with the bare LTMO, the MnO2-coated sample exhibited enhanced electrochemical performance. After the MnO2 coating, the first discharge capacity rose from 224.2 to 239.1 mAh/g, and the initial irreversible capacity loss declined from 78.2 to 46.0 mAh/g. Meanwhile, the cyclic retention climbed up to 88.2% after 100 cycles at 0.5 C, which was more competitive than that of the bare LTMO with a value of 71.1%. When discharging at a high current density of 2 C, the capacity increased from 100.5 to 136.9 mAh/g after the modification. These investigations may be conducive to the practical application of LTMO in prospective automotive Li-ion batteries.

In Situ X-ray Diffraction and X-ray Absorption Spectroscopic Studies of a Lithium-Rich Layered Positive Electrode Material: Comparison of Composite and Core-Shell Structures

Lithium- and manganese-rich transition-metal oxide (LMR-NMC) electrodes have been designed either as heterostructures of the primary components ("composite") or as core-shell structures with improved electrochemistry reported for both configurations when compared with their primary components. A detailed electrochemical and structural investigation of the 0.5Li₂MnO₃-0.5LiNi_0.5Mn_0.3Co_0.2O₂ composite and core-shell structured positive electrode materials is reported. The core-shell material shows better overall electrochemical performance compared to its corresponding composite material. While both configurations gave the same initial charge capacity of ∼300 mAh/g when cycled at a rate of 10 mA/g at 25 °C, the core-shell sample gives a discharge capacity of 232 mAh/g compared to 208 mAh/g delivered by the composite sample. Also, the core-shell sample gave better rate capability and a smaller first-cycle irreversible capacity loss than the composite sample. The improved performance of the core-shell material is attributed to its lower surface reactivity and limited structural change since the more stable Li₂MnO₃ shell screens the more reactive Ni-rich core material from interacting with either air or electrolyte at high potentials, thereby preventing electrode surface modification. In situ X-ray diffraction correlated with electrochemical data revealed that the composite sample shows stronger volumetric changes in the lattice parameters during charging to 4.8 V. In addition, X-ray absorption spectroscopy showed an incomplete Ni reduction process after the first discharge for the composite sample. From these results, it was shown that this leads to a more severe degradation in the composite material that affects Li⁺ intercalation in the subsequent discharge, thereby resulting in its poorer performance. Furthermore, to confirm these results, another LMR-NMC material with a different composition (having a Ni-poor core)-0.5Li₂MnO₃-0.5LiNi_0.33Mn_0.33Co_0.33O₂-was investigated. The core-shell structured positive electrode material also gave an improved electrochemical performance compared to the corresponding composite positive electrode material. These results show that the core-shell configuration could effectively be used to improve the performance of the LMR-NMC materials to enable future high-energy applications.

The Role of Zr Doping in Stabilizing Li[Ni0.6 Co0.2 Mn0.2 ]O2 as a Cathode Material for Lithium-Ion Batteries

Ni-rich layered LiNi_1-x-y Co_x Mn_y O₂ systems are the most promising cathode materials for high energy density Li-ion batteries (LIBs). However, Ni-rich cathode materials inevitably suffer from rapid capacity fading and poor rate capability owing to structural instability and unstable surface side reactions. Zr doping has proven to be an effective method to enhance the cycle and rate performances by stabilizing the structure and increasing the Li⁺ diffusion rate. Herein, effects of Zr-doping on the structural stability and Li⁺ diffusion kinetics are thoroughly investigated in LiNi_0.6 Co_0.2 Mn_0.2 O₂ (LNCM) cathode material using atomic-resolution scanning transmission electron microscopy imaging, XRD Rietveld refinement, and density functional theory calculations. Zr doping mitigates the degree of cation mixing, decreases the structural transformation, and facilitates Li⁺ diffusion resulting in improved cyclic performance and rate capability. Based on the obtained results, an atomistic model is proposed to explain the effects of Zr doping on the structural stability and Li⁺ diffusion kinetics in LNCM cathode materials.

Improving the structural stability and electrochemical performance of Na2Li2Ti6O14 nanoparticles via MgF2 coating

To improve their electrochemical performance and structural stability, Na₂Li₂Ti₆O₁₄ (NLTO) nanoparticles were synthesized and then coated with a very thin MgF₂ layer. Microscopy confirmed that the MgF₂-NLTO particles are about 150–250 nm in size, and that the thickness of the MgF₂ layer for the MgF₂-NLTO-5 sample is ∼5 nm. Electrochemical measurements showed that the charge–discharge specific capacities of the five samples under a current density of 50 mA g⁻¹ after 100 cycles are 110.4/110.7, 150.7/151.3, 181.1/182.1, 205.7/206.9 and 238.9/239.2 mA h g⁻¹, showing that the performance of MgF₂-NLTO-5 is the best among all the samples. Thanks to the thin coating layer, the polarization of the anode was reduced significantly, and its reversibility and lithium diffusion dynamics were also improved obviously. The performance improvement can be attributed to the suppression of surface corrosion and the enhancement of structural stability.

Combination of nanocrystallization and surface coating techniques was improved to be helpful for improving the electrochemical performance of NLTO.

Synthesis and electrochemical characterization of Mg–Al co-doped Li-rich Mn-based cathode materials

A novel synergistic strategy to improve electrochemical performance of Li-rich cathode by co-doping of magnesium and aluminium.

Effect of Nb and F Co-doping on Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material for High-Performance Lithium-Ion Batteries

The Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x (x = 0, 0.01, 0.03, 0.05) is prepared by traditional solid-phase method, and the Nb and F ions are successfully doped into Mn and O sites of layered materials Li_1.2Mn_0.54Co_0.13Ni_0.13O₂, respectively. The incorporating Nb ion in Mn site can effectively restrain the migration of transition metal ions during long-term cycling, and keep the stability of the crystal structure. The Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O^2- by the strongly electronegative F^- is beneficial for suppressed the structure change of Li₂MnO₃ from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x gets improved, which is higher than that of pure Li_1.2Mn_0.54Co_0.13Ni_0.13O₂. In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.

Enhanced Electrochemical Properties of Zr4+-doped Li1.20[Mn0.52Ni0.20Co0.08]O2 Cathode Material for Lithium-ion Battery at Elevated Temperature

The typical co-precipitation method was adopted to synthesized the Li-excess Li_1.20[Mn_0.52-xZr _x Ni_0.20Co_0.08]O₂ (x = 0, 0.01, 0.02, 0.03) series cathode materials. The influences of Zr⁴⁺ doping modification on the microstructure and micromorphology of Li_1.20[Mn_0.52Ni_0.20Co_0.08]O₂ cathode materials were studied intensively by the combinations of XRD, SEM, LPS and XPS. Besides, after the doping modification with zirconium ions, Li_1.20[Mn_0.52Ni_0.20Co_0.08]O₂ cathode demonstrated the lower cation mixing, superior cycling performance and higher rate capacities. Among the four cathode materials, the Li_1.20[Mn_0.50Zr_0.02Ni_0.20Co_0.08]O₂ exhibited the prime electrochemical properties with a capacity retention of 88.7% (201.0 mAh g^-1) after 100 cycles at 45 °C and a discharge capacity of 114.7 mAh g^-1 at 2 C rate. The EIS results showed that the Zr⁴⁺ doping modification can relieve the thickening of SEI films on the surface of cathode and accelerate the Li⁺ diffusion rate during the charge and discharge process.

The impact of aluminum impurity on the regenerated lithium nickel cobalt manganese oxide cathode materials from spent LIBs

An effective recycling process from spent LIBs has been developed, and the tolerability of aluminum was studied in this work.

Improved Cycling Stability and Fast Charge-Discharge Performance of Cobalt-Free Lithium-Rich Oxides by Magnesium-Doping

Layered Li-rich, Co-free, and Mn-based cathode material, Li_1.17Ni_0.25-xMn_0.58Mg_xO₂ (0 ≤ x ≤ 0.05), was successfully synthesized by a coprecipitation method. All prepared samples have typical Li-rich layered structure, and Mg has been doped in the Li_1.17Ni_0.25Mn_0.58O₂ material successfully and homogeneously. The morphology and the grain size of all material are not changed by Mg doping. All materials have a estimated size of about 200 nm with a narrow particle size distribution. The electrochemical property results show that Li_1.17Ni_0.25-xMn_0.58Mg_xO₂ (x = 0.01 and 0.02) electrodes exhibit higher rate capability than that of the pristine one. Li_1.17Ni_0.25-xMn_0.58Mg_xO₂ (x = 0.02) indicates the largest reversible capacity of 148.3 mAh g^-1 and best cycling stability (capacity retention of 95.1%) after 100 cycles at 2C charge-discharge rate. Li_1.17Ni_0.25-xMn_0.58Mg_xO₂ (x = 0.02) also shows the largest discharge capacity of 149.2 mAh g^-1 discharged at 1C rate at elevated temperature (55 °C) after 50 cycles. The improved electrochemical performances may be attributed to the decreased polarization, reduced charge transfer resistance, enhanced the reversibility of Li⁺ ion insertion/extraction, and increased lithium ion diffusion coefficient. This promising result gives a new understanding for designing the structure and improving the electrochemical performance of Li-rich cathode materials for the next-generation lithium-ion battery with high rate cycling performance.

Nano-Crystalline Li1.2Mn0.6Ni0.2O₂ Prepared via Amorphous Complex Precursor and Its Electrochemical Performances as Cathode Material for Lithium-Ion Batteries

An amorphous complex precursor with uniform Mn/Ni cation distribution is attempted for preparing a nano-structured layered Li-rich oxide (Li_1.2Mn_0.6Ni_0.2O₂)cathode material, using diethylenetriaminepentaacetic acid (DTPA) as a chelating agent. The materials are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests. The crystal structure of Li-rich materials is found to be closely related to synthesis temperature. As-obtained nano materials sintered at 850 °C for 10 h show an average size of 200 nm with a single crystal phase and good crystallinity. At a current density of 20 mA·g⁻¹, the specific discharge capacity reaches 221 mAh·g⁻¹ for the first cycle and the capacity retention is 81% over 50 cycles. Even at a current density of 1000 mA·g⁻¹, the capacity is as high as 118 mAh·g⁻¹. The enhanced rate capability can be ascribed to the nano-sized morphology and good crystal structure.

Microwave-enhanced electrochemical cycling performance of the LiNi0.2Mn1.8O4 spinel cathode material at elevated temperature

Microwave irradiation exposed the {111} facets and increased the Mn⁴⁺ content of LiNi_0.2Mn_1.8O₄ spinel for improved cycling performance at 60 °C.

Enhanced high rate performance of Li[Li0.17Ni0.2Co0.05Mn0.58−xAlx]O2−0.5x cathode material for lithium-ion batteries

Pristine LNCM and LNCMA as Li-rich cathode materials for lithium ion batteries were synthesized via a sol–gel route. The Al-substituted LNCM sample exhibits an enhanced high rate performance and superior cyclability.

A time and energy conserving solution combustion synthesis of nano Li1.2Ni0.13Mn0.54Co0.13O2 cathode material and its performance in Li-ion batteries

Energy efficient solution combustion synthesis of lithium rich cathode material.

Hybrid annealing method synthesis of Li[Li0.2Ni0.2Mn0.6]O2 composites with enhanced electrochemical performance for lithium-ion batteries

A lithium rich composite cathode electrode material Li[Li_0.2Ni_0.2Mn_0.6]O₂ was synthesized using the hybrid annealing method.

Microwave-assisted synthesis of high-voltage nanostructured LiMn1.5Ni0.5O4 spinel: tuning the Mn3+ content and electrochemical performance

The LiMn1.5Ni0.5O4 spinel is an important lithium ion battery cathode material that has continued to receive major research attention because of its high operating voltage (∼4.8 V). This study interrogates the impact of microwave irradiation on the Mn(3+) concentration and electrochemistry of the LiMn1.5Ni0.5O4 spinel. It is shown that microwave is capable of tuning the Mn(3+) content of the spinel for enhanced electrochemical performance (high capacity, high capacity retention, excellent rate capability, and fast Li(+) insertion/extraction kinetics). This finding promises to revolutionize the application of microwave irradiation for improved performance of the LiMn1.5Ni0.5O4 spinel, especially in high rate applications.