Cathode Material Li1 Research Articles

F-doping effects on microstructure and electrochemical performance of cathode material Li1.2Mn0.54Ni0.13Co0.13O2

Lithium-rich manganese-based (Li-rich Mn-based) cathode materials possess high specific capacity, low self-discharge rate and steady working voltage, but cycle performance and rate performance need to be further improved. In this study, cathode materials Li1.2Mn0.54Ni0.13Co0.13O2-xFx (x = 0, 0.02, 0.05, 0.08) are synthesized by the co-precipitation method with the two-step calcination process. And the F-doping effects on the microstructure and the electrochemical performance are investigated in the cathode materials Li1.2Mn0.54Ni0.13Co0.13O2. The results indicate that among all the F-doped cathode materials, the crystal lattice parameters are increased, order degree and stability of the layered structure are improved. As for x = 0.05, cathode material Li1.2Mn0.54Ni0.13Co0.13O1.95F0.05 (LMO-F0.05) shows the best cycle performance and rate performance with its capacity retention rate 87.7% after 100 cycles at 0.2 C and discharge capacity 117 mAh g−1 at 5 C high power. It can be seen that F doping is a simple and crucial strategy to promote the Li ion diffusion and develop high performance layered cathode materials.

Enhanced electrochemical properties of Li1.2Mn0.54Co0.13Ni0.13O2 by modulation of surface oxygen vacancies

The lithium-rich cathode material Li1.2Mn0.54Co0.13Ni0.13O2 (LMR) has attracted significant interest due to its high specific capacity and energy density, which stem from its unique anionic redox chemistry. Oxygen vacancies significantly impact the crystal structure and electrochemical performance of Li-rich manganese-based cathode materials. This study thoroughly examined how sintering temperature affects the crystallinity, morphology, crystal structure, and oxygen vacancy content of the materials, as well as the impact of oxygen vacancies on their structural and electrochemical properties. XPS and EPR analyses are conducted to investigate the relationship between sintering temperature and oxygen vacancies. Additionally, the spinel phase, altered by oxygen vacancies on the material's surface, is identified using Raman, TEM and EELS. Furthermore, first-principles calculations and data from the constant-current intermittent titration technique indicate that oxygen vacancies significantly enhance the material's ion transport rate.

Enhancing lithium-rich manganese cathodes: Structural optimization and defect engineering via innovative thermal treatment for improved electrochemical durability and efficiency

Lattice oxygen release, which results in progressive structural disintegration and inevitable capacity fading, poses a significant challenge to the commercialization of Li-rich Mn-based cathode materials. To mitigate voltage capacity degradation and offer a feasible manufacturing process for commercial-scale production, this study developed a cost-effective thermal processing method for a Li-rich Mn-based cathode material Li1.2Ni0.13Co0.13Mn0.54O2 based on water-spray quenching. This method refines the physical phase structure, increases the specific capacity of the material, and creates a defect-tolerant dislocation substructure in the surface lattice. Furthermore, refining the nanoparticle size suppresses the occurrence of redox side reactions and mitigates electrolyte corrosion, resulting in a material with a specific capacity of 196.7 mAh g−1 after 200 cycles at a rate of 1C. This performance markedly exceeds that achieved with the untreated material, which exhibited a capacity of 104.2 mAh g−1 under the same conditions. In contrast to the conventional surface engineering and elemental modulation techniques, this study presents a practical solution for industrial applications, facilitating cost reductions and large-scale production.

Vibrationally-resolved RIXS reveals OH-group formation in oxygen redox active Li-ion battery cathodes.

Vibrationally-resolved resonant inelastic X-ray scattering (VR-RIXS) at the O K-edge is emerging as a powerful tool for identifying embedded molecules in lithium-ion battery cathodes. Here, we investigate two known oxygen redox-active cathode materials: the commercial LixNi0.90Co0.05Al0.05O2 (NCA) used in electric vehicles and the high-capacity cathode material Li1.2Ni0.13Co0.13Mn0.54O2 (LRNMC) for next-generation Li-ion batteries. We report the detection of a novel vibrational RIXS signature for Li-ion battery cathodes appearing in the O K pre-peak above 533 eV that we attribute to OH-groups. We discuss likely locations and pathways for OH-group formation and accumulation throughout the active cathode material. Initial-cycle behaviour for LRNMC shows that OH-signal strength correlates with the cathodes state of charge, though reversibility is incomplete. The OH-group RIXS signal strength in long-term cycled NCA is retained. Thus, VR-RIXS offers a path for gaining new insights to oxygen reactions in battery materials.

Novel Low-Strain Layered/Rocksalt Intergrown Cathode for High-Energy Li-Ion Batteries.

Both layered- and rocksalt-type Li-rich cathode materials are drawing great attention due to their enormous capacity, while the individual phases have their own drawbacks, such as great volume change for the layered phase and low electronic and ionic conductivities for the rocksalt phase. Previously, we have reported the layered/rocksalt intergrown cathodes with nearly zero-strain operation, while the use of precious elements hinders their industrial applications. Herein, low-cost 3d Mn4+ ions are utilized to partially replace the expensive Ru5+ ions, to develop novel ternary Li-rich cathode material Li1+x[RuMnNi]1-xO2. The as-designed Li1.15Ru0.25Mn0.2Ni0.4O2 is revealed to have a layered/rock salt intergrown structure by neutron diffraction and transmission electron microscopy. The as-designed cathode exhibits ultrahigh lithium-ion reversibility, with 0.86 (231.1 mAh g-1) out of a total Li+ inventory of 1.15 (309.1 mAh g-1). The X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectra further demonstrate that the high Li+ storage of the intergrown cathode is enabled by leveraging cationic and anionic redox activities in charge compensation. Surprisingly, in situ X-ray diffraction shows that the intergrown cathode undergoes extremely low-strain structural evolution during the charge-discharge process. Finally, the Mn content in the intergrown cathodes is found to be tunable, providing new insights into the design of advanced cathode materials for high-energy Li-ion batteries.

Electrochemical properties of Li-rich ternary cathode material Li1.20Mn0.44Ni0.32Co0.04O2 and its oxygen-deficient phase

As the cathode material of lithium-ion batteries, Li-rich ternary layered oxides usually suffer from high first cycle irreversible capacity, low rate capability, and structural instability during charge–discharge. Recent studies show that Ni-rich Li1.20Mn0.44Ni0.32Co0.04O2 material has good structural stability. In this paper, the electrochemical performance of Li1.20Mn0.44Ni0.32Co0.04O2 and its oxygen-deficient phase Li1.20Mn0.44Ni0.32Co0.04O1.83 are studied by the first-principles calculations. The results show that, for the pristine phase Li1.20Mn0.44Ni0.32Co0.04O2, the theoretical delithiation capacity is 380 mAh/g and the highest charging voltage platform is 4.99 V. The O ions are found to participate in the charge compensation significantly. Ni ions can only contribute 118 mAh/g of the delithiation capacity, and the remaining charging capacity is contributed by O ions. For the oxygen-deficient phase Li1.20Mn0.44Ni0.32Co0.04O1.83, the highest voltage platform is reduced by 0.21 V, O ions are also found to participate in the charge compensation obviously. Compared to the pristine phase, transition metal (TM) ions in the oxygen-deficient phase exhibit higher chemical activity, while the contribution of O ions to charge compensation is relatively reduced. The oxygen-deficient phase has a slightly higher theoretical capacity (392 mAh/g) than the pristine phase.

Theoretical insight into oxygen vacancy formation in Li1.25Ni0.5Mn0.25O2 cathode material

Here, we have studied the thermodynamic stability of lattice oxygen in Li-rich Co-free cathode material Li1.25Ni0.5Mn0.25O2 using first-principles calculations. It is found that the oxygen at O2 coordination is more likely to be released in Li-rich cathode Li1.25Ni0.5Mn0.25O2, and the stability of oxygen is closely related to temperature and oxygen partial pressure. The Li1.25Ni0.5Mn0.25O2 cathode will spontaneously form O-vacancies above 842 K. When the oxygen partial pressure increases to 22 atm, the lattice oxygen is stable even at 1000 K. The presence of O-vacancy will cause more localized charges, and Ni-ions will also undergo a reduction reaction in the electrode. This theoretical study gives new insight about the thermodynamic stability of lattice oxygen and will help to suppress the formation of O-vacancy in Li-rich cathode materials, paving the way for developing Li-rich cathode materials for next-generation Li-ion batteries.

All dry in one step (ADIOS to water) synthesis of W-coated Li1+x(Ni0·7Mn0.3)1-xO2

Surface coatings have been used to improve the chemistry at the electrode-electrolyte interface of cathodes in lithium-ion batteries by forming a passivation film that can reduce side reactions with the electrolyte and can potentially offer enhanced electrochemical performance as well. Previous work in our group has shown that W-coated LiNiO2 electrode particles are more mechanically robust, which is reflected in the significantly improved cycling performance as microcracking is minimized. The application of these coatings, however, usually requires a separate processing step before or after lithiation of hydroxide precursors. Here, we propose combining a facile dry coating technique with the solid-state synthesis of cobalt-free cathode material Li1+x (Ni0·7Mn0.3)1-xO2 (Ni70Mn30), where W coated single crystal Ni70Mn30 is made in a one-step dry process from constituent compounds and a lithium source without any solvents. In this work, hydroxide precursors were bypassed completely and various precursor choices for the synthesis of cobalt-free materials were investigated. Cycling data shows that the W-coated single crystal Ni70Mn30 offers increased capacity without impacting lifetime and possesses excellent electrochemical performance. By adopting this direct synthesis approach, we believe that large amounts of wastewater and solid waste products can be eliminated while simplifying the cathode production process greatly.

The Synthesis and Electrochemical Property of Spinel Cathode Material Li1.05[(Mn1.99Gd0.01)0.91(Mn1.8Co0.2)0.09]O4 for Lithium-Ion Batteries

The Synthesis and Electrochemical Property of Spinel Cathode Material Li1.05[(Mn1.99Gd0.01)0.91(Mn1.8Co0.2)0.09]O4 for Lithium-Ion Batteries

Surface-Stabilized High-Entropy Layered Oxyfluoride Cathode for Lithium-Ion Batteries.

High-entropy materials have been demonstrated to improve the structural stability and electrochemical performance of layered cathode materials for lithium-ion batteries (LIBs). However, structural stability at the surface and electrochemical performance of these materials are less than ideal. In this study, we show that fluorine substitution can improve both issues. Here, we report a new high-entropy layered cathode material Li1.2Ni0.15Co0.15Al0.1Fe0.15Mn0.25O1.7F0.3 (HEOF1) based on the partial substitution of oxygen with fluorine in previously reported high-entropy layered oxide LiNi0.2Co0.2Al0.2Fe0.2Mn0.2O2. This new compound delivers a discharge capacity of 85.4 mAh g-1 and a capacity retention of 71.5% after 100 cycles, showing significant improvement from LiNi0.2Co0.2Al0.2Fe0.2Mn0.2O2 (first 57 mAh g-1 and 9.8% after 50 cycles). This improved electrochemical performance is due to suppression of the surface M3O4 phase formation. Although still an early stage study, our results show an approach to stabilize the surface structure and improve the electrochemical performance of high-entropy layered cathode materials.

AlPO4-Li3PO4 dual shell for enhancing interfacial stability of Co-free Li-rich Mn-based cathode

Li-rich Mn-based cathode materials (LRM) have attracted extensive attention as key cathode material for achieving high energy density in lithium ion batteries. However, the irreversible oxygen precipitation and structural transformation during its cycling process, resulting in capacity and voltage degradation have heavily hindered practical applications. The Co-free Li-rich Mn-based cathode material Li1.2Ni0.185Mn0.585Fe0.03O2 by the modified Pechini method, the AlPO4-Li3PO4 double shell was formed in situ on its surface. The AlPO4 protective layer formed by the highly electronegative (PO4)3- with not only effectively inhibits the precipitation of surface oxygen, but also suppresses the interfacial side reactions and transition metal dissolution, thus raising the cycling performances. The formation of the outer Li3PO4 helps to remove the residual Li+ on the surface, accelerates the diffusion and charge transfer process of Li+ at the electrode/electrolyte interface. The synergistic modification of the AlPO4-Li3PO4 dual shell can significantly improve the cycling stability and rate performance. In particular, the 3% modified sample with a capacity retention of 74.8% after 200 cycles at 0.2 C. The first discharge specific capacity is 260.73 mAh g-1 at 0.1 C, and the initial coulombic efficiency reaches 84.96%. The lithium-ion full cell employing 3% and graphite exhibit a specific energy density of 440 Wh kg-1 at 0.1 C, and shows the best cycling stability with 78.3% capacity retention over 100 cycles at 1 C.

Modulating the local electronic structure via Al substitution to enhance the electrochemical performance of Li-rich Mn-based cathode materials

The performance degradation caused by irreversible O2 release and structural collapse has seriously hindered the commercialization of Li-rich Mn-based oxide cathode materials (LMOs). Herein, a Li-rich Mn-based cathode material Li1.2Ni0.2Mn0.6−xAlxO2 (x = 0.02, 0.04, 0.06) via the substitution of Mn by Al was designed. By introducing additional strong Al-O bonds into the local atomic coordination around O and transition metal (TM) to modulate the local electronic structure, the TM 3d-O 2p and non-bonding O-2p band are transferred to lower energy, thus increasing the redox reaction potential. The substitution of Al also enhances the interaction with oxygen and increases the oxygen vacancy formation energy, which stabilizes the lattice oxygen framework and ultimately further inhibits the structural transition (layered → spinel phase) caused by the reduction of TM ions during the cycling process and improves the stability of the layered structure. The results show that the voltage decay of the Al-doped sample is only 0.349 V after 300 cycles, which is much lower than the 0.578 V of the pristine sample. Assembled as a full cell using LMNA2 as the cathode and commercial graphite as the anode, it exhibited a specific energy density of 454.3 Wh kg−1 at 0.1 C, with a capacity retention rate of over 86% after 100 cycles. This research provides a novel idea for the future development of LMOs for high voltage and energy density applications.

Enhanced Cycling and Structure Stability of an Electron Transfer-Accelerating Polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)-Covered Mn-Based Layered Cathode with Ga3+ Doping for a Li-Ion Battery.

Mn-based cathode material Li1.20Mn0.52Ni0.20Co0.08O2 was proposed and ameliorated by surface-coating poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and doping Ga3+. X-ray diffraction and high-resolution transmission electron microscopy studies revealed that part of Ga3+ replacing the Ni site could reduce the Li+/Ni2+ mixing by forming a well-ordered layered structure and a homogeneous coating layer of PEDOT:PSS is covered on the surface of Li1.20Mn0.52Ni0.19Co0.08Ga0.01O2. The results of the electrochemical studies demonstrated the higher initial charging-discharging Coulombic efficiency, and outstanding rate capabilities and cyclic performance were obtained for the PEDOT:PSS-covered and Ga3+-doped samples. Especially, 2 wt % PEDOT:PSS-coated Li1.20Mn0.52Ni0.19Co0.08Ga0.01O2 delivered 38.3 mAh g-1, which is larger than the pristine cathode at a 5C high rate. Meanwhile, it could retain 189.6 mAh g-1 (90.3% of its initial discharge capacity at 45 °C) after 300 cycles with a 1C rate, while the pristine cathode only delivered 149.7 mAh g-1 with 80.7% cycling retention left. The results strongly suggested that such PEDOT:PSS-coated and Ga3+-doped Mn-based layered structure materials demonstrated high potential as a cathode candidate especially for high-energy applications.

Stoichiometry matters: correlation between antisite defects, microstructure and magnetic behavior in the cathode material Li1−zNi1+zO2

Using synchrotron X-ray and neutron diffraction, NMR and magnetometry techniques, this study reveals how point defects evolve and critically affect particle growth and magnetic properties in the cathode material Li1−zNi1+zO2 (−0.05 ≤ z ≤ 0.35).

Cadmium Modification of the Lithium-Rich Cathode Material Li1.2Ni0.133Mn0.534Co0.133O2

Cadmium Modification of the Lithium-Rich Cathode Material Li1.2Ni0.133Mn0.534Co0.133O2

Effect of ZIF-67 derivative Co3O4 on Li-rich Mn-based cathode material Li1.2Mn0.54Ni0.13Co0.13O2

The zeolitic imidazolate frameworks 67 (ZIF-67) derivative Co3O4 composite lithium-rich manganese-based layered oxide was successfully synthesized by a simple solid-phase sintering method and systematically studied. The introduction of the derivatives does not excessively induce changes in the transition metal layered oxide structure as tested by XRD, SEM, TEM, and XPS. The electrochemical test and analysis show that the high surface area and porous structure of the ZIF-67 derivative Co3O4 can promote the contact efficiency of the electrode and the electrolyte, thereby delaying the structural phase change which caused by the long cycle process and suppressing the voltage attenuation. In particular, a composite ratio of 10:1 samples can most effectively improve the first coulomb efficiency, cycling stability, and structural stability of lithium-rich materials. The discharge specific capacity at 0.1 C is 258.9 mAh/g, and the first coulomb efficiency is 74.93%. Especially, the discharge specific capacity at 0.5 C is 234.1 mAh/g, and the capacity retention rate is 86.28% after 100 cycles.

Effect of Different Calcination Temperatures on the Structure and Properties of Zirconium-Based Coating Layer Modified Cathode Material Li1.2Mn0.54Ni0.13Co0.13O2

Effect of Different Calcination Temperatures on the Structure and Properties of Zirconium-Based Coating Layer Modified Cathode Material Li1.2Mn0.54Ni0.13Co0.13O2

Structural and Chemical Compatibilities of Li1- x Ni0.5 Co0.2 Mn0.3 O2 Cathode Material with Garnet-Type Solid Electrolyte for All-Solid-State Batteries.

All-solid-state batteries (ASSBs) based on ceramic materials are considered a key technology for automobiles and energy storage systems owing to their high safety and stability. However, contact issues between the electrode and solid-electrolyte materials and undesired chemical reaction occurring at interfaces have hindered their development. Herein, the chemical compatibility and structural stability of composite mixtures of the layered cathode materials Li1- x Ni0.5 Co0.2 Mn0.3 O2 (NCM523) with the garnet-type solid electrolyte Li6.25 Ga0.25 La3 Zr2 O12 (LLZO-Ga) during high-temperature co-sintering under various gas flowing conditions are investigated. In situ high-temperature X-ray diffraction analysis of the composite materials reveals that Li diffusion from LLZO-Ga to NCM523 occurs at high temperature under synthetic air atmosphere, resulting in the decomposition of LLZO-Ga into La2 Zr2 O7 and the recovery of charged NCM523 to the as-prepared state. The structural stability of the composite mixture at high temperature is further investigated under N2 atmosphere, revealing that Li diffuses toward the opposite direction and involves the phase transition of LLZO-Ga from a cubic to tetragonal structure and the reduction of the NCM523 cathode to Ni metal. These findings provide insight into the structural stability of layered cathode and garnet-type solid-electrolyte composite materials and the design of stable interfaces between them via co-sintering for ASSBs.

Identifying the effect of fluorination on cation and anion redox activity in Mn based cation-disordered cathode

Li-rich disordered rock-salt cathode (DRX) materials with advantage of low cost, long cycle life, nature abundant resource and high power and energy density attracted a great deal of scholarly attention. However, the poor cycle stability and the unclear realization of cation and anion redox activity in low-cost element system have severely hindered the construction of high-performance DRX. Herein, a promising class of Ti-Mn based cathode materials Li1.25Mn0.25Nb0.25Ti0.25O2 and Li1.25Mn0.25Ti0.5O1.75F0.25 were designed and successfully synthesized to construct high energy density DRX and investigate the effect of fluorination on cation and anion redox activity. The results show that both fluoridized and unfluoridized DRX possess a similar structure (Fm-3 m), but distinctly different charge/discharge profiles. The fluoridized cathode shows high initial charge/discharge capacity of 317.3/283.9 mAh g−1, specific energy density of 1370.4/735.5 Wh kg−1 and stable capacity retention with a discharge capacity of 202.6 mAh g−1 after 20 cycles at 20 mA g−1. Combining relevant spectroscopic results and HRTEM images, we revealed that the excellent cyclability of Li1.25Mn0.25Ti0.5O1.75F0.25 is rooted in the weakened adverse effects of moderated oxygen redox and the reduced Jahn–Teller distortion effect resulting from Mn3+, endowing the fluoridized DRX with better structural stability and larger Mn2+/Mn4+ reservoir. The strategy of constructing low cost oxyfluoride and the understanding of the mechanism of fluorination induced cation and anion redox activity would provide reference for the development of high-performance DRX materials.

Quantitative analysis of diffuse electron scattering in the lithium ion battery cathode material Li1.2Ni0.13Mn0.54Co0.13O2

Quantitative analysis of diffuse electron scattering in the lithium ion battery cathode material Li_1.2Ni_0.13Mn_0.54Co_0.13O₂