Lithium-rich Cathode Research Articles

Integrating a Ferroelectric Interface with a Well-Tuned Electronic Structure in Lithium-Rich Layered Oxide Cathodes for Enhanced Lithium Storage

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi0.5Na0.5TiO3 (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li+ and hinder the migration of On- but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li+/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g-1 and 78.57% after 500 cycles at 2.0-4.65 V and 231.7 mAh g-1 and 85.76% after 200 cycles at 2.0-4.9 V at 1C, respectively.

In Situ Surface Coating and Oxygen Vacancy Dual Strategy Endowing a Li-Rich Li1.2Mn0.55Ni0.11Co0.14O2 Cathode with Superior Lithium Storage Performance

Lithium-rich Mn-based cathode materials are widely regarded as the next-generation cathode materials for high-energy-density lithium-ion batteries owing to their low cost and high specific capacity. Nonetheless, their commercial application is seriously hindered by low initial Coulombic efficiency, capacity loss, and voltage drop during long-term cycling. Herein, surface phosphorus doping and a mixture protective layer with oxygen vacancies (OVs) which consists of Li3PO4 and LiMnPO4 as a surface-coating layer on the Li1.2Mn0.55Ni0.11Co0.14O2 cathode material through a facile solid–gas reaction treatment, which can simultaneously optimize the surface chemical structure and deplete lithium impurity, is proposed. What is more, the dual strategy of surface engineering and OVs can improve electronic conductivity and regulate the ion diffusion rate. The dual-modified sample expresses a discharge capacity of 180.9 mA h g–1 with a capacity retention of 89.2% at 0.5 C after 250 cycles, which is better than that of the pristine sample (63.7%). This work provides a facile and effective method for surface coating design to improve other Li-rich manganese-based cathodes for rechargeable batteries.

Oxygen redox chemistry in lithium-rich cathode materials for Li-ion batteries: Understanding from atomic structure to nano-engineering

Lithium-rich oxide compounds have been recognized as promising cathode materials for high performance Li-ion batteries, owing to their high specific capacity. However, it remains a great challenge to achieve the fully reversible anionic redox reactions to realize high capacity, high stability, and low voltage hysteresis for lithium-rich cathode materials. Therefore, it is critically important to comprehensively understand and control the anionic redox chemistry of lithium-rich cathode materials, including atomic structure design, and nano-scale materials engineering technologies. Herein, we summarize the recent research progress of lithium-rich cathode materials with a focus on redox chemistry. Particularly, we highlight the oxygen-based redox reactions in lithium-rich metal oxides, with critical views of designing next generation oxygen redox lithium cathode materials. Furthermore, we purposed the most promising strategies for improving the performances of lithium-rich cathode materials with a technology-spectrum from the atomic scale to nano-scale.

Enhancing cyclic performance of lithium-rich manganese-based cathode via in-situ co-doping of magnesium and fluorine

Lithium-rich manganese-based materials (LRM) are regarded as promising next-generation commercial cathodes due to their exceptionally high capacities and working voltages. However, lithium-rich manganese-based materials are plagued with inferior cyclic stability and voltage fading, which greatly stifled their commercial transitions. In this work, the dopant F and Mg uniformly distributed lithium-rich manganese-based cathode material is firstly prepared via an in-situ co-precipitation and high-temperature calcination method. The F and Mg co-doped sample can demonstrate excellent cyclic stability (88.56%, after 100 cycles at 1 C), and higher initial discharge and coulombic efficiency by reducing the transition metal (TM) loss and structure stabilization. Thus, this work presents crucial findings in the development of lithium-rich manganese-based materials, which provides a novel doping route and a vital method of cation-anion co-doping to prepare high-performing cathodes.

Stabilizing structure and voltage decay of lithium-rich cathode materials

A major challenge in the discovery of high-energy lithium-ion batteries (LIBs) is to control the voltage stability and Li+ kinetics in lithium-rich layered oxide (LrLO) cathode materials. Although these materials can provide a higher specific capacity compared to the current industrially used cathodes, the substantial voltage decay and low Li+ diffusion during long term cycling is a serious reason for hindering their practical applications. In order to suppress the voltage decay in lithium-rich cathode materials, herein we introduce the Ti doping into Li1.2Mn0.56Ni0.17Co0.07O2 cathodes. Also, the influence of Ti doping on the crystalline internal structure, surface chemistry, cycling retention, and Li+ kinetics of Li1.2Mn0.56Ni0.17Co0.07O2 cathodes have been focused in this work. The Ti doping effectively enhances the structural/interfacial stability of the cathode and accelerates the Li+ kinetics by expanding the lattice, thereby significantly realizing its voltage/cycling stability and high-rate capability. Experimental results show that Ti-doped LrLO (1% Ti) has achieved high electrochemical kinetics as the discharge cycle retention increased from 61.58% (pristine) to 80.0% after 180 cycles at 1 C, with 150.3 mAh g−1 showing superior high-rate performance at 5C. Ex-situ XRD results confirmed the better structural stability of Ti-doped LrLO after high-rate electrochemical cycling. Our findings provide a suitable element doping strategy for regulating the voltage decay and cycle retention of LrLO, thus promoting their real-world application in future batteries.

Construction of Lithium-Rich Manganese-Based Cathodes Based on Activated Manganese Dioxide for Enhanced Energy Storage Performances

Herein, highly active manganese dioxide is prepared by roasting-disproportionation treatment to fabricate a lithium-rich manganese-based cathode (Li1.6Mn0.6Ni0.3Co0.1O2.6) for enhanced charge/discharge capacity performance. The findings display that the roasting temperature and subsequent disproportionation degree significantly affect crystalline structure of manganese dioxide, thereby apparently improving the electrochemical performances of lithium-rich manganese-based cathodes. When the roasting temperature is 600 °C, the content of α-MnO2 reaches to 69.3% in lithium-rich manganese-based cathode, resulting in the best electrochemical activity. The prepared lithium-rich cathode material displays a discharge capacity of 243 mAh/g after 100 cycles at 0.2 C, and 155 mAh/g at 3 C, which shows good multiplicative performance.

Effect of compaction pressure on electrochemical performance of layered lithium-rich oxide

Lithium-rich oxide cathode material focuses the attention of many researchers due to its excellent electrochemical performance for lithium–ion batteries. Further improvement on the performance with a strong operability approach can be beneficial to its industrialization and commercialization. In this work, the effect of powder compaction pressure in sintering process on the electrochemical performance of Li[Formula: see text]Mn[Formula: see text]Ni[Formula: see text]Co[Formula: see text]O2 cathode material is investigated. Four cathode materials under different powder compaction pressure are synthesized by sol–gel method. The XRD analysis results reveal their consistency on the crystal structure. But there is a slight difference on particle size and microstructure found by SEM analysis. Electrochemical tests show that a cathode material under medium compaction pressure exhibits the best performance with a discharge capacity of 170.3 mAh⋅g[Formula: see text] at the rate of 200 mA⋅g[Formula: see text] with 89.35% retention after 100 cycles. This work reveals that the powder compaction pressure does have influence on the cycle and rate performance and this relation is not proportional and linear.

Influence of Tin and Titanium on the Electrochemical Performance of Lithium-Rich Cathode Materials

Influence of Tin and Titanium on the Electrochemical Performance of Lithium-Rich Cathode Materials

Stabilizing Li-Rich Layered Cathode Materials Using a LiCoMnO4 Spinel Nanolayer for Li-Ion Batteries.

Lithium–rich cathodes have excess lithium in the transition metal layer and exhibit an extremely high specific capacity and good energy density. However, they still have some disadvantages. Here, we propose LiCoMnO4, a new nanolayer coating material with a spinel structure, to modify the surface of lithium cathode oxide (Li7/6Mn1/2Ni1/6Co1/6O2) with a layered structure. The designed cathode with nanolayer spinel coating delivers an excellent reversible capacity, outstanding rate capability, and superior cycling ability whilst exhibiting discharge capacities of 300, 275, 220, and 166 mAh g−1 at rates of 0.1 C at 2.0−4.8 V formation and 0.1, 1, and 5 C, respectively, between 2.0 and 4.6 V. The cycling ability and voltage fading at a high operational voltage of 4.9 V were also investigated, with results showing that the nanolayer spinel coating can depress the surface of the lithium cathode oxide layer, leading to phase transformation that enhances the electrochemical performance.

Enabling stable 4.6 V LiCoO2 cathode through oxygen charge regulation strategy

LiCoO2 is the preferred cathode material for consumer electronic products due to its high volumetric energy density. However, the unfavorable phase transition and surface oxygen release limits the practical application of LiCoO2 at a high-voltage of 4.6 V to achieve a higher energy density demanded by the market. Herein, both bulk and surface structures of LiCoO2 are stabilized at 4.6 V through oxygen charge regulation by Gd-gradient doping. The enrichment of highly electropositive Gd on LiCoO2 surface will increase the effective charge on oxygen and improve the oxygen framework stability against oxygen loss. On the other hand, Gd ions occupy theCo-sites and suppress the unfavorable phase transition and micro-crack. The modified LiCoO2 exhibits superior cycling stability with capacity retention of 90.1% over 200 cycles at 4.6 V, and also obtains a high capacity of 145.7 mAh/g at 5 C. This work shows great promise for developing high-voltage LiCoO2 at 4.6 V and the strategy could also contribute to optimizing other cathode materials with high voltage and large capacity, such as cobalt-free high-nickel and lithium-rich manganese-based cathode materials.

Aluminum doping and lithium tungstate surface coating double effect to improve the cycle stability of lithium-rich manganese-based cathode materials

Al doped lithium-rich manganese-based Li1.2Mn0.54−xAlxNi0.13Co0.13O2 (x = 0, 0.03) cathode materials for lithium-ion batteries were synthesized with sol-gel method, and then Li2WO4 coating was prepared by one-step liquid phase method. The effects of Al doping and Li2WO4 coating on the electrochemical properties of lithium-rich manganese-based cathode materials were systematically studied. The results show that Al doping significantly improves the cycle stability of lithium-rich manganese-based cathode material, and the coating Li2WO4 significantly improves its magnification performance and the voltage attenuation of discharge plateau. The coating amount of Li2WO4 is 5%, and the specific capacity of Li1.2Mn0.51Al0.03Ni0.13Co0.13O2 cathode material is still up to about 110 mAh·g−1 in the charge and discharge voltage range of 2.0-4.8 V and the current density of 1,000 mA·g−1. At the same time, the capacity retention rate of 300 cycles at the current density of 100 mA·g−1 is 78%, and the voltage attenuation of the discharge plateau during the cycle is also significantly reduced. This work provides a new idea for solving the cycle stability and platform voltage attenuation of lithium-ion battery lithium-rich manganese-based cathode materials.

Surface engineering for high stable lithium-rich manganese-based cathode materials

Lithium-rich manganese-based material shows great potential as the high specific cathode materials due to its low cost, environmental friendliness, high operating voltage and simple preparation process. However, the poor capacity retention and cycling performance caused by its unstable structure during cycling restrict the commercialization. In this work, Li1.2Ni0.16Mn0.56Co0.08O2 was synthesized utilizing a Co-precipitation method and different amount of La(PO3)3 (La(PO3)3 = 2 wt%, 4 wt% and 6 wt%) was selected as the coating layer to resolve the above issues. During the calcination process, La(PO3)3 reacts with impurities such as LiOH and Li2CO3 on the lithium-rich surface to reduce the residual lithium on the surface, thus improving the interfacial stability, slowing down the corrosion of the electrolyte, and finally enhancing its electrochemical performance. The cathode materials coated with 4% of La(PO3)3 showed the best electrochemical performance in terms of capacity retention and cycling performance compared to the pristine NCM. The high initial discharge capacity of 214.21 mAh/g and capacity retention of 94.2% after 100 cycles at 0.1 C can be obtained. This work provides an effective strategy to protect the cathode from corrosion and will promote its further practical applications in high specific Li-ion batteries.

Temperature-controlled direct dry synthesis of Co-Ni free cathode materials 0.7Li2MnO3·0.3LiFeO2 for lithium-ion batteries

Cobalt-nickel (Co-Ni) free Lithium-rich cathode material (1 − x)Li2MnO3·xLiFeO2 is more environmental friendly and cheaper than other traditional cathode materials. However, the complex synthesis method limits its large-scale practical application. This work explores a simple dry synthesis route to directly obtain 0.7Li2MnO3·0.3LiFeO2 with good electrochemical performance. Calcination temperature is a key factor controlling the phase growth. With the calcination temperature increasing, the crystallization and ordered layered structure are improved, but the LiFe5O8 spinel phase appears in X-ray diffraction (XRD) patterns from 600 ℃. The results of selected area electron diffraction (SAED), element mapping (EDS) and vibrating sample magnetometer (VSM) demonstrate convincingly the growth progress of LiFe5O8 as the temperature rises. The spinel phase deteriorates the electrochemical performance. Furthermore, it is proved that the crystallization and activity of Li2MnO3 precursor are effective to retard the formation of LiFe5O8 and enhance the electrochemical performance. The sample calcined at 600 ℃ exhibits a high initial capacity above 200 mAh g−1, but capacity fades quickly to 120 mAh g−1 after 50 cycles at 0.2 C. The sample calcined at 650 ℃ with a little LiFe5O8 delivers a low initial capacity about 160 mAh g−1, but stabilizes at 160 mAh g−1 after 50 cycles. Therefore, how to control the formation of thermally stable phase LiFe5O8 is an important issue, and it needs further investigation to achieve Co-Ni free Li-rich cathode materials with excellent performance. Significantly, the simple synthesis and acceptable electrochemical properties make the practical application of Fe-Mn based Li-rich material possible.

Suppression and Mechanism of Voltage Decay in Sb-Doped Lithium-Rich Layered Oxide Cathode Materials.

Voltage decay during cycling is the major problem for lithium-rich layered oxide cathodes. Here, we designed Sb-doped lithium-rich layered oxides prepared by a coprecipitation-solvent thermal method, aiming to alleviate the voltage decay of lithium-rich layered oxides. The midpoint discharge voltage and specific capacity of Li1.20Ni0.133Co0.133Mn0.633Sb0.01O2 (LLMO-Sb1) demonstrate almost no decaying after 100 cycles at 1 C. Moreover, it exhibits a large rate capacity (215 mAh g-1 at 5 C). The suppressed voltage decay and enhanced cycle performance of Sb-doped material are attributed to the high Sb-O bond energy, which can enhance the stability of the layered structure and suppress the layered-to-spinel phase transition. Moreover, Sb doping improves the rate capacity by reducing the energy barrier of lithium ion diffusion. This work opens a gate to prevent the oxidation of superoxo and peroxo, stabilizing the layered structure by selecting an element with a suitable radius and electronegativity.

Mg2+ doping into Li sites to improve anionic redox reversibility and thermal stability of lithium-rich manganese-based oxides cathode

As a low cost and low atomic mass dopant, Mg2+ doping is often used to improve the electrochemical performance of lithium-rich manganese-based layered oxides (LRMO) cathode materials. However, the Mg2+ doping site is still controversial and its mechanism is not clear. In this work, Mg-doped LRMO was synthesized by a spray-drying method. It was proved that the Mg2+ is doped into the Li sites of the Li layers substituting partial ‘Li–O–Li’ with a stronger ‘Li–O–Mg’ configuration. The Mg-doped LRMO possesses a stable lattice structure and high reversibility of anionic redox reaction, which shows a high initial Coulombic efficiency of 89.0%, enhanced specific capacity (305.3 mAh/g at 0.1 C), cycling performance, and thermal stability in comparison with the pristine sample. The first-principle calculations reveal that the top of the O2p band of Mg-doped LRMO is lower about 0.81 eV, which implies a more stable lattice oxygen structure.

Unravelling the Influence of Synthetic Paths on the Cation Arrangement in Lithium-rich Layered Oxide Cathode Materials

• The strategy for adjusting the cation arrangement of the Li-rich cathode materials was proposed by simply adjusting the mixing order of cations in the sol-gel synthesis. • The results further prove that improving the order arrangement of cations can effectively ameliorate the stability and electrochemical performance of the Li-rich materials. • The optimized Li-rich materials exhibit a good cycle performance with a capacity retention of 71.7% after 150 cycles, much better than that of the pristine sample with a retention of only 45.5%. Lithium-rich layered oxides (LLOs) have garnered substantial attention due to their superior reversible capacity. However, oxygen release and transition metal migration are likely to occur during the charging and discharging process because of the inherently unstable structure of LLOs, which hampers their commercialization process. Present studies suggest that the local structure and atomic arrangement have a considerable impact on the stability of LLOs. Hence, researchers have been trying to determine how to implement the control of atomic ordering. Herein, we propose a new strategy to modify the cation arrangement of LLOs by adjusting the mixing order of cations through the sol-gel method. As a result, the optimized S-LLO sample presents a more ordered cation arrangement than that of the pristine M-LLO sample. The S-LLO cathode, meanwhile, provides a high discharging capacity of 249.5 mAh·g −1 accompanied by a coulombic efficiency of 73.7% at 0.1 C and can still maintain a capacity of 91.8 mAh·g −1 at 10 C. More importantly, a high-capacity retention of 71.7% can be obtained after 150 cycles at 1 C for the optimized LLO cathode, whereas the pristine M-LLO sample retains a retention of only 45.5%. A new strategy to modify the cation arrangements of LLOs by adjusting the mixing order of cations through the sol-gel method.

Tuning the Electronic, Ion Transport, and Stability Properties of Li-rich Manganese-based Oxide Materials with Oxide Perovskite Coatings: A First-Principles Computational Study.

Lithium-rich manganese-based oxides (LRMO) are regarded as promising cathode materials for powering electric applications due to their high capacity (250 mAh g–1) and energy density (∼900 Wh kg–1). However, poor cycle stability and capacity fading have impeded the commercialization of this family of materials as battery components. Surface modification based on coating has proven successful in mitigating some of these problems, but a microscopic understanding of how such improvements are attained is still lacking, thus impeding systematic and rational design of LRMO-based cathodes. In this work, first-principles density functional theory (DFT) calculations are carried out to fill out such a knowledge gap and to propose a promising LRMO-coating material. It is found that SrTiO3 (STO), an archetypal and highly stable oxide perovskite, represents an excellent coating material for Li1.2Ni0.2Mn0.6O2 (LNMO), a prototypical member of the LRMO family. An accomplished atomistic model is constructed to theoretically estimate the structural, electronic, oxygen vacancy formation energy, and lithium-transport properties of the LNMO/STO interface system, thus providing insightful comparisons with the two integrating bulk materials. It is found that (i) electronic transport in the LNMO cathode is enhanced due to partial closure of the LNMO band gap (∼0.4 eV) and (ii) the lithium ions can easily diffuse near the LNMO/STO interface and within STO due to the small size of the involved ion-hopping energy barriers. Furthermore, the formation energy of oxygen vacancies notably increases close to the LNMO/STO interface, thus indicating a reduction in oxygen loss at the cathode surface and a potential inhibition of undesirable structural phase transitions. This theoretical work therefore opens up new routes for the practical improvement of cost-affordable lithium-rich cathode materials based on highly stable oxide perovskite coatings.

Effect of co-precipitation and solid-state reaction synthesis methods on lithium-rich cathodes Li1.2Ni0.2Mn0.6O2

Effect of co-precipitation and solid-state reaction synthesis methods on lithium-rich cathodes Li1.2Ni0.2Mn0.6O2

Pre-annealing treatment effects on the electrochemical performances of lithium-rich layered oxide cathodes for Li-ion battery

Pre-annealing treatment effects on the electrochemical performances of lithium-rich layered oxide cathodes for Li-ion battery

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