Lithium-rich Manganese-based Cathode Research Articles

Improving the electrochemical performance of lithium-rich manganese-based cathode materials by Na₂S₂O₈ surface treatment

Lithium-rich manganese-based cathode materials are well-regarded for their high specific capacity and notable voltage thresholds, making them attractive for advanced energy storage applications. However, their widespread commercialization is hindered by challenges in cycle performance, including suboptimal initial Coulombic efficiency, inadequate cycle stability, and constrained rate capability. To address these issues, this paper introduces a novel modification strategy using Na₂S₂O₈ to chemically delithiate the surface of the materials. This modification strategy dramatically enhances the initial Coulombic efficiency. The results demonstrate that the initial Coulombic efficiency of the two pre-activated samples improved to 84.6 % and 102.2 %, respectively. At the same time, the Na₂S₂O₈-treated samples exhibit a higher maximum discharge capacity at a 0.2 C rate, reaching 211.1 mAh g⁻¹ and 201.3 mAh g⁻¹, which notably surpasses the untreated sample's capacity of 188.7 mAh g⁻¹. Additionally, the treated samples exhibit improved cycling and rate performance, with capacity retention of 81.2 % and 63.5 %, respectively. After 60 cycles, these figures continue to be superior to those of the untreated material, which stands at 57.3 %. The results demonstrate that Na₂S₂O₈ treatment leads to the in situ formation of spinel phases on the material surface, thereby enhances the cycling stability and rate capability of the cathode material. Compared to traditional surface treatment methods, Na₂S₂O₈ solution treatment can induce more profound structural evolution without necessitating high-temperature calcination, thus reducing the demands on process conditions and equipment and offering greater process controllability. Moreover, this surface modification strategy paves the way for applying spinel coatings on other substrates with similar structures.

Effect of sites of doped Mg on the stability of lattice oxygen in lithium-rich manganese-based cathode materials

Elemental doping is considered as an effective method for altering the localized electronic structure of lattice oxygen in lithium-rich manganese-based oxides (LRMO) and enhancing their structural stability. However, the effect of doping heteroatoms at different sites on the oxygen redox is not clear. In this work, Mg is introduced into transition metals (TM) and lithium (Li) sites of LRMO at co-precipitation stage and lithiation stage to prepare LRMO-TM and LRMO-Li, respectively. The experimental results and density-functional theory calculations demonstrate that the oxygen release is reduced from 4.1653 nmol mg−1 of pristine to 3.3886 nmol mg−1 of LRMO-Li, and 2.7688 nmol mg−1 of LRMO-TM. The reduction of oxygen release of LRMO-Li is related to the formation of strong Mg-O interactions. Different from that, the lower oxygen release of LRMO-TM is mainly due to the reduction of electron holes in the O 2p state caused by the weaker Mn-O covalency, which effectively restricts the over-oxidization of oxygen. The capacity retention of LRMO-TM is 85.18 % at 0.2C after 200 cycles, which is higher than that of LRMO (78.63 %) and LRMO-Li (82.28 %). This work reveals the mechanism of enhancing lattice oxygen stability caused by Mg doping at different sites.

Achieving the dual regulation of microstructure and microdefects in lithium rich materials by electrospinning technology

Lithium-rich manganese-based cathode materials (LNCM) have garnered tremendous attention for the superior reversible capacity. However, the inherently unstable structure and low diffusion kinetics of Li+ hamper their commercialization process. Recent studies have shown that void defects within grains are the main cause of oxygen release and voltage drop during cycling. Therefore, highly crystallinity small particles are the ideal structure for high power density and cycling stability of LNCM. However, improving the crystallinity of materials often means increasing the sintering temperature, which can easily cause material aggregation and grain growth. In this paper, by adopting the electrostatic spinning technology, nanowire shaped precursor are constructed, which facilitates the direct contact between the hot gas flow and the precursor during sintering, thus promoting ion diffusion and material crystallinity. Besides, the electronic and chemical environment in the modified LNCM sample have regulated simultaneously, accompanying with a significant increase in O vacancies, Mn4+ and Ni3+ ions. Adjustments from morphology to molecular structure increased the contact area between the material and electrolyte, improved the diffusion ability of Li+, and enhanced structural stability of the material, resulting in improved rate performance and cycling stability. This study expands our understanding of adopting electrospinning technology to prepare high-performance materials.

A universal strategy towards high-rate and ultralong-life of Li‐rich Mn‐based cathode materials

Lithium-rich manganese-based cathode materials (LRMs) have shown promise for the next-generation lithium battery cathodes due to their high discharge specific capacity (∼250 mAh g−1) and wide operating voltage range (2.0–4.8 V). However, these materials face limitations such as low initial Coulombic efficiency (ICE), poor cycle stability, and inadequate rate capability. To address these challenges, we employed a simple citric acid treatment (CA-treatment) method to fabricate the Li-rich spinel coating layer on LRMs. This in situ formed spinel Li4Mn5O12 layer successfully suppresses the oxygen release, provides three-dimensional (3D) lithium-ion diffusion channels and enriches Li embedding sites, resulting in a substantial improvement in the rate capability and high-rate cycling performance. The modified LRM delivers a high specific capacity of 193.7 mAh g−1 at 2.0 C and 154.8 mAh g−1 at 5.0 C, after 1000 cycles at 10.0 C, 77.4 % capacity retention with 102.5 mAh g−1 is realized. This facile CA-treatment benefits the electrochemical properties of LRMs comparable to those of altering the microscopic morphology. This work offers a new avenue for exploring outstanding LRMs with high-rate and ultralong cycling life.

Multifunctional surface modification to enhance the electrochemical performance of lithium-rich manganese-based cathode materials

The preparation of high-performance lithium-rich manganese-based cathode materials (LLOs) require attention to the redox of anions and the migration of transition metals (TM) during the cycling process. In this study, Ce ion-doped Li-rich cathode coated with La0.2Ce0.8O2, which has abundant oxygen vacancies on its surface, was prepared. The presence of the oxygen storage material La0.2Ce0.8O2 can effectively absorb the irreversible oxygen generated during cycling, preventing it from reacting with the electrolyte to form thick cathode electrolyte interface (CEI) coatings. These coatings hinder the relative activity of lattice oxygen in the bulk phase, reducing the specific capacity of the material. Additionally, the 5d metal ion Ce carries a large nuclear charge, causing a 'pinning effect' when it integrates into the LLOs structure. This effect reduces thermal oscillation in the lattice, impedes TM migration during battery charging and discharging, and effectively prevents voltage decay. Results indicate that after 100 cycles at 1C and 25 °C, the surface-coated materials maintain a discharge-specific capacity of 194 mAh/g, compared to 158 mAh/g for uncoated material. Voltage decay decreased from 4.4 mV/cycle to 1.8 mV/cycle, with an ICE of 91.5 % versus the original material's 82.8 %. The modified material also exhibits improved rate performance, retaining a specific capacity of 162 mAh/g at 3C, in contrast to the original material's 123 mAh/g.

Jointly Improving Anionic-Cationic Redox Reversibility of Lithium-Rich Manganese-Based Cathode Materials by N Surface Doping.

The lithium-rich manganese-based layer oxide (LRMO) with high specific capacity (∼300 mAh g-1) and economic feasibility is accepted as the cathode material for high energy density rechargeable batteries. Accompanied by the additional anionic redox reactions during the initial charging process, LRMO presents oxygen release, sluggish Li+ diffusion, and irreversible transition metal ion (TM) migration, which is responsible for its severe structural deterioration and rapid capacity/voltage decay. Here, the N doping strategy is proposed via feasible treatment of oxygen-vacancy-containing Li1.16Ni0.21Mn0.63O2-δ (LNMO) particles. The as obtained LNMO-N samples demonstrate doping N, partially reduced Mn/Ni cations, and oxygen vacancies on the surface. The DFT calculations and experimental results demonstrate that N replacing the crystal oxygen sites on the surface reduces the energy barrier for diffusion, thereby enhancing the kinetics of Li+ diffusion and improving the reversibility of transition metal migration. Furthermore, N doping induces stacking faults and a more flexible structure. Therefore, LNMO-N exhibits a significantly improved anionic-cationic redox reaction reversibility with a high discharge specific capacity of 296.6 mAh g-1 at 20 mA g-1 within the range of 2.0 to 4.8 V and an impressive initial Coulombic efficiency of 85.9%. Moreover, the rate capability is obviously improved with a remarkable capacity of 215.1 mAh g-1 at 200 mA g-1 in 200 cycles with a capacity retention of 72.52% and exceptional performance of 141.4 mAh g-1 even at a higher current density of 1000 mA g-1.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity of materials by decreasing the surface work function and increasing the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5 % capacity retention; even in 2.0–5 V, 93.9 % after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

Cut-off voltage influencing the voltage decay of single crystal lithium-rich manganese-based cathode materials in lithium-ion batteries

The voltage decay of Li-rich layered oxide cathode materials results in the deterioration of cycling performance and continuous energy loss, which seriously hinders their application in the high-energy–density lithium-ion battery (LIB) market. However, the origin of the voltage decay mechanism remains controversial due to the complex influences of transition metal (TM) migration, oxygen release, indistinguishable surface/bulk reactions and the easy intra/inter-crystalline cracking during cycling. We investigated the direct cause of voltage decay in micrometer-scale single-crystal Li1.2Mn0.54Ni0.13Co0.13O2 (SC-LNCM) cathode materials by regulating the cut-off voltage. The redox of TM and O2− ions can be precisely controlled by setting different voltage windows, while the cracking can be restrained, and surface/bulk structural evaluation can be monitored because of the large single crystal size. The results show that the voltage decay of SC-LNCM is related to the combined effect of cation rearrangement and oxygen release. Maintaining the discharge cutoff voltage at 3 V or the charging cutoff voltage at 4.5 V effectively mitigates the voltage decay, which provides a solution for suppressing the voltage decay of Li-rich and Mn-based layered oxide cathode materials. Our work provides significant insights into the origin of the voltage decay mechanism and an easily achievable strategy to restrain the voltage decay for Li-rich and Mn-based cathode materials.

Cation doping for enhanced layer spacing and electrochemical performance in Li-rich Mn-based lithium-ion cathode materials

Lithium-rich manganese-based cathode materials offer promising research avenues owing to their high capacity. This study delved into the impact of cation doping on Li1.2Ni0.13Co0.13Mn0.54O2(LNCMO). A range of layered Li1.2BXNi0.13Co0.13Mn0.54O2 (LNCMOxB, B = Ca, Na, Al) cathode materials were produced utilizing calcium, sodium, and aluminum chloride as dopants. Combining these elements with the lithium-rich materials improves the capacity retention of the positive electrode and mitigates voltage decay. X-ray diffraction analysis, Rietveld structural refinement, SEM, and XPS verified the inclusion of Ca, Na, and Al in the synthesized samples. Electrochemical analysis revealed that the LNCMO-0.01Na sample, possessing the largest dopant radius, exhibited favorable cyclic stability at 0.2C. Conversely, the LNCMO-0.01Al sample, featuring the smallest doped cation radius, demonstrated superior rate performance. Specifically, after 30 cycles at varying rates, the capacity reached 170 mAh·g−1 at 0.2C. The LNCMO-0.007Ca sample exhibited the highest residual capacity, maintaining 151.4 mAh·g−1 after 100 cycles at 0.2C. Doping Li sites in Li1.2Ni0.13Co0.13Mn0.54O2 materials with appropriately sized divalent cations significantly enhances their overall electrochemical performance. This enhancement is attributed to ion doping within the Li and TM layers, expediting the diffusion kinetics of Li ions, and augmenting ion and electronic conductivity. Investigating the doping modification of lithium-rich manganese-based oxide microspheres is instrumental in advancing positive electrode materials for lithium-ion batteries, aiming for increased specific capacity and more stable material structures.

Enhancing electrochemical performance of lithium-rich manganese-based cathode materials through lithium sulfate coating

Enhancing electrochemical performance of lithium-rich manganese-based cathode materials through lithium sulfate coating

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Construction of rod-like micro/nano structure and its effects on the electrochemical energy storage performance of lithium-rich manganese-based cathode material

Performance improvement of Li-rich Mn-based materials with the submicron-sized single-crystal morphology and cationic doping

Lithium-rich manganese-based cathode materials (LRMCs) can be regarded as one of the most potential cathode materials for the next-generation high-energy Li-ion batteries due to the extra oxygen redox, which can greatly increase the actual output energy density of LRMCs. Nevertheless, the structure degradation and inevitable loss of oxygen will be triggered by the irreversible oxygen redox, which will cause a significant decline in cyclic performance and limited initial Coulombic efficiency, thus restricting their industrial applicability. Herein, the LRMCs with the submicron-sized single-crystal morphology and sodium doping are prepared by molten salt treatment with NaCl. On one hand, the submicron-sized single-crystal cathode effectively reduces the diffusion path for Li+ due to the smaller particle dimensions. On the other hand, Na+ doping expands the Li slab spacing, promoting the transport of Li+. The results show that the as-prepared material can purposefully alleviate oxygen release, improve structure stability, and increase the Li+ diffusion rate for the pristine LRMCs. Moreover, the as-prepared material in this study exhibits a higher reversible capacity of 282.8 mAh g−1 at 0.1 C and displays good cyclic performance, retaining a capacity rate of 80.9% after 200 cycles at 1 C. Therefore, this study offers a potential exploration for designing LRMCs with high energy density and excellent cyclic performance, which are achieved through building submicron-sized single-crystal morphology and introducing cationic doping.

Modification of lithium-rich manganese-based cathode materials by continuous coating formed by surface treatment of sodium dodecyl sulfate to improve electrochemical performance

With the development of new energy devices, the demand for electrode materials with high energy density (> 400 Wh/kg) is increasing day by day. Lithium-rich manganese-based cathode materials (LRMC) which meet the requirements are considered one of the most promising materials for the next generation of lithium-ion batteries, and have attracted wide attention. However, LRMC still faces some key scientific problems that need to be addressed, such as interface side reactions, poor rate performance, rapid voltage and capacity attenuation, and low first coulomb efficiency. The continuous Na2SO4-coated lithium-rich manganese-based cathode material Li1.2Ni0.13Co0.13Mn0.54O2 (S-LRMC) was synthesized using sodium dodecyl sulfate (SDS). SDS is composed of hydrophobic aliphatic hydrocarbon groups and hydrophilic sulfate carboxyl groups, so it can form a micelle-like coating on the surface of LRMC materials in aqueous solution. The uniform Na2SO4 coating formed after calcination can effectively inhibit the side reaction between electrode material and electrolyte and reduce the dissolution of transition metal ions. As a result, capacity retention, rate performance and discharge specific capacity are improved. After 100 cycles at 1 C, the specific discharge capacity of 4% S-LRMC is 187.8 mAh g−1 (LRMC is 138.3 mAh g−1), and the capacity retention is 87.35%. Even at a high current density of 5 C, the material still has a specific discharge capacity of 143.6 mAh g−1, which proves that the electrochemical performance of the material is excellent. Therefore, this study provides a new solution for improving the structural stability and electrochemical performance of lithium ion batteries.

PO43--doped layer @ spinel @ rGO sandwich-structured lithium-rich manganese-based cathode material with enhancing rate capability and cycle stability for Li-ion battery

The Li-rich Mn-based cathode (LRM) material faces challenges like low initial coulombic efficiency (ICE) and reduced capacity retention, which limit their commercial viability in high energy density lithium-ion batteries (LIBs). These challenges primarily arise from the irreversible migration of transition metal ions (TMn+) and the escape of lattice oxygen. Herein, this study proposes a novel approach to enhance Li-rich cathodes by implementing a PO43--doped layer @ spinel @ rGO sandwich structure, which effectively addresses the aforementioned challenges. Through the synergistic effects of PO43- doping and rGO surface modification, the modified samples demonstrate remarkable electrochemical properties. These include an impressive initial coulombic efficiency (ICE) of 87.54%, and a superior capacity of 187.12 mAhg−1 and 149.44 mAhg−1 at 25°C and 45°C, respectively, following 200 cycles at 1 C. Additionally, they exhibit an outstanding rate capability of 82.3 mAhg−1 at 10 C and a minimal voltage decrease of 0.504 V after 200 cycles. The synergetic strategy presented in this work serves as an inspiring source for the exploration of high energy density and long-cycle cathode materials.

Low-temperature tolerant lithium-rich manganese-based cathode enabled by facile SnO2 decoration

SnO2-decorated Li[Li0.144Ni0.136Co0.136Mn0.544]O2 (S-LLOs) demonstrates a high capacity and excellent cycle life at low temperatures, which is attributed to the low activation energy of Li+ diffusion in the CEI layer and charge transfer.

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

Realizing primary/secondary particle co-coating with CoxB for lithium-rich cathodes in high-performance lithium-ion batteries

The construction of a surface protection layer is an important way to improve the cycling stability of lithium-rich manganese-based cathode materials. However, the protection for the primary particles inside is usually neglected compared with the secondary particles, which increases the corrosion risk of the electrolytes. In view of this, amorphous CoxB coated Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) was rationally designed and prepared. Nano CoxB not only completely coated the surface of the secondary particles but also penetrated between the grain boundaries of the primary particles to achieve the protection of the primary particles. Thus, the cycling stability of the LMNCO is improved significantly. After 200 cycles at 1C and 25°C, the capacity loss rate of CoxB-LMNCO is 8.9%. Even at 2C and 40°C, the value is only 13.4%. As a result, this work provides a new idea to improve the electrochemical performances of the LMNCO cathode materials in high-performance lithium-ion batteries.

Lithium-Ion Conductor Li2ZrO3-Coated Primary Particles To Optimize the Performance of Li-Rich Mn-Based Cathode Materials.

A lithium-rich manganese-based cathode material (LRMC) is currently considered as one of the most promising next-generation materials for lithium-ion batteries, which has received much attention, but the LRMC still faces some key scientific issues to break through, such as poor rate capacity, rapid voltage, capacity decay, and low first coulomb efficiency. In this work, homogeneous Li2ZrO3 (LZO) was successfully coated on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 (LRO) by molten salt-assisted sintering technology. Li2ZrO3 has good chemical and electrochemical stability, which can effectively inhibit the side reaction between electrode materials and electrolytes and reduce the dissolution of transition metal ions. Thus, the as-prepared LRO@LZO composites are expected to improve the cycling performance. It can be found that the discharge specific capacity of LRO is 271 mAh g-1 at 0.1 C, and the capacity retention rate is still 93.7% after 100 cycles at 1 C. In addition, Li2ZrO3 is an excellent lithium-ion conductor, which is prone to increasing the lithium-ion transfer rate and improving the rate capacity of LRO. Therefore, this study provides a new solution to improve the structure stability and electrochemical performance of LRMCs.

Durable lithium-ion insertion/extraction and migration behavior of LiF-encapsulated cobalt-free lithium-rich manganese-based layered oxide cathode

Lithium-rich manganese-based cathode has made a subject of intense scrutiny for scientists and application researchers due to their exceptional thermal stability, high specific capacity, high operating voltage, and cost-effectiveness. However, the inclusion of cobalt, as a crucial component in lithium-rich manganese-based cathode materials, has become a cause for concern due to its limited availability and non-renewable nature, which eventually limits the growth of the battery industry and increase costs. Considering the poor stability of cobalt-free cathode, this work proposes a coating strategy of LiF through a simple high-temperature melting method. Directly coating LiF on Li1.2Ni0.2Mn0.6O2 surface is found to be an effective way to protect the cathode material, decrease metal solubility, and inhibit irreversible phase transition processes, thus leading to an improved electrochemical performance. As a result, the battery employing LiF coated Li1.2Ni0.2Mn0.6O2 cathode can be stabilized over 280 cycles and maintain a capacity of 110 mAh g−1 at 1C. What’s more, the mechanisms of ion insertion/extraction behavior and ion migration process are also studied systematically. This study will open the avenue to develop a high-energy battery system with cobalt-free cathode.

Computational Understandings of Cation Configuration-Dependent Redox Activity and Oxygen Dimerization in Lithium-Rich Manganese-Based Layered Cathodes

Lithium-rich manganese-based layered oxides have emerged as a fresh paradigm for developing advanced cathode materials with high energy density for next-generation lithium-ion batteries. Understanding lattice oxygen dimerization is quite essential for the optimal design of lithium-rich manganese-based cathode materials. Herein, based on density functional theory (DFT) calculations, a local Ni-honeycomb Li–Ni–Mn cation configuration for the Li1.22Ni0.22Mn0.56O2 cathode was carefully examined, which may coexist with the well-known local Li-honeycomb structure in experimentally synthesized Li1.2Ni0.2Mn0.6O2 samples. The local Li–Ni–Mn cation configurations have significant impacts on oxygen redox activity, transition metal atom migration, and oxygen dimerization in the charging process of LixNi0.22Mn0.56O2. It is found that there is no correlation between high lattice oxygen redox activity and easy oxygen dimerization, such as Li-honeycomb structures simultaneously exhibiting higher oxygen redox activities and higher activation energy barriers for prohibiting oxygen dimerization than Ni-honeycomb structures. The structural regulations of the local Li–Ni–Mn cation configuration by avoiding the local Ni-honeycomb structures to inhibit Mn migration and ease lattice oxygen dimerization and by making full use of the local Li-honeycomb structures would maximize performance of Li-rich Mn-based layered oxides. Such fresh insights provide us a fresh strategy to optimally design the local honeycomb structure for high-performance Li-rich Mn-based cathode materials.