LiNi0.5Mn1.5O4 Research Articles

An electrolyte additive with boron-nitrogen-oxygen alkyl group enabled stable cycling for high voltage LiNi0.5Mn1.5O4 cathode in lithium-ion battery

An electrolyte additive with boron-nitrogen-oxygen groups for high voltage (5 V) LiNi0.5Mn1.5O4 (LNMO) electrode is investigated by electrochemical performance, material analysis and density function theory first principles calculation (DFT). The 1 wt% Methylboronic acid MIDA ester (ADM) additive in ethylene carbonate and dimethyl carbonate (EC/DMC) electrolyte for LNMO cathode shows a paramount discharge capacity retention of 96% (15% in without additive) after 25 cycles at 75 mA g−1 and 40 °C, also inhibits the impedance growth during cycling. By increasing the charge/discharge current density from 15 mA g−1 to 450 mA g−1, the rate capability of LNMO cell with ADM additive is ca. 40%, while the counterpart is only 1.5%. By characterizations, the results interpret that the ADM additive decomposes and participates in the reaction pathway of cathode electrolyte interface (CEI) formation, which are more protective and resistant to electrolyte oxidative decompositions, and more potent in maintaining the structural integrity of nickel (Ni), manganese (Mn), and PF6−.

Enhancing the Electrochemical Performance of a High-Voltage LiNi0.5 Mn1.5 O4 Cathode in a Carbonate-Based Electrolyte with a Novel and Low-Cost Functional Additive.

Butyric anhydride (BA) is used as an effective functional additive to improve the electrochemical performance of a high-voltage LiNi0.5 Mn1.5 O4 (LNMO) cathode. In the presence of 0.5 wt % BA, the capacity retention of a LNMO/Li cell is significantly improved from 15.3 to 88.4 % after 200 cycles at 1 C. Furthermore, the rate performance of the LNMO/Li cell is also effectively enhanced, and the capacity goes up to 112 mAh g-1 even at 5 C, which is considerably higher than that of a LNMO/Li cell in electrolyte without BA additive (95.4 mAh g-1 at 5 C). Linear sweep voltammetry and cyclic voltammetry results reveal that the BA additive can be preferentially oxidized to construct a stable cathode electrolyte interphase (CEI) film on the LNMO cathode. Subsequently, the BA-derived CEI film can alleviate the decomposition of the electrolyte and the dissolution of Mn and Ni ions from the LNMO cathode as well as maintain the structural stability of LNMO during the cycling process; this leads to outstanding electrochemical performance. Thus, this work provides an effective and low-cost functional electrolyte for high-voltage LNMO-based LIBs.

Insight into the High-Temperature Cycling Stability of a Micro-nanostructured LiNi0.5Mn1.5O4/Graphene Composite Cathode for High-Voltage Lithium-Ion Batteries

LiNi0.5Mn1.5O4 (LNMO) cathode has drawn enormous interest for its extraordinarily high voltage and low cost. However, a high voltage leads to critical side reactions significantly degrading the cyc...

Tuning the Morphology and Electronic Properties of Single-Crystal LiNi0.5Mn1.5O4−δ: Exploring the Influence of LiCl–KCl Molten Salt Flux Composition and Synthesis Temperature

Single-crystal materials have played a unique role in the development of high-performance cathode materials for Li batteries due to their favorable chemomechanical stability. The molten salt synthesis method has become one of the most prominent techniques used to synthesize single-crystal layered and spinel materials. In this work, the molten salt synthesis method is used as a technique to tune both the morphology and Mn3+ content of high-voltage LiNi0.5Mn1.5O4 (LNMO) cathodes. The resulting materials are thoroughly characterized by a suite of analytical techniques, including synchrotron X-ray core-level spectroscopy, which are sensitive to the material properties on multiple length scales. The multidimensional characterization allows us to build a materials library according to the molten salt phase diagram as well as to establish the relationship among synthesis, material properties, and battery performance. The results of this work show that the Mn3+ content is primarily dependent on the synthesis temperature and increases as the temperature is increased. The particle morphology is mostly dependent on the composition of the molten salt flux, which can be tailored to obtain well-defined octahedrons enclosed by (111) facets, plates with predominant (112̅) facets, irregularly shaped particles, or mixtures of these. The electrochemical measurements indicate that the Mn3+ content has a larger contribution to the battery performance of LNMO than do morphological characteristics and that a significant amount of Mn3+ could become detrimental to the battery performance. However, with similar Mn3+ contents, morphology still plays a role in influencing the battery cycle life and rate performance. The insights of molten salt synthesis parameters on the formation of LNMO, with deconvolution of the roles of Mn3+ and morphology, are crucial to continuing studies in the rational design of LNMO cathode materials for high-energy Li batteries.

Enabling high areal capacity for Co-free high voltage spinel materials in next-generation Li-ion batteries

The rapidly growing technological demand for lithium-ion batteries has prompted the development of novel cathode materials with high energy density, low cost, and improved safety. High voltage spinel, LiNi0.5Mn1.5O4 (LNMO), is one of the most promising candidates yet to be commercialized. The two primary obstacles for this material are the inferior electronic conductivity and fast capacity degradation in full cells due to the high operating voltage. By systematically addressing these limitations, we successfully develop a thick LNMO electrode with areal capacity loadings up to 3 mAh·cm−2. The optimized thick electrode is paired with a commercial graphite anode at both the coin cell and pouch cell level, achieving a full cell capacity retention as high as 72% and 78%, respectively, after 300 cycles. We attribute this superior cycling stability to careful optimizations of cell components and testing conditions, with a specific focus improving electronic conductivity and high voltage compatibility. These results suggest precise control of materials quality, electrode architecture and electrolyte optimization can soon support the development of a cobalt-free battery system based on a thick LNMO cathode (>4 mAh·cm2), which will eventually meet the needs of next-generation Li-ion batteries with reduced cost, improved safety, and assured sustainability.

Improved high-temperature cyclability of AlF3 modified spinel LiNi0.5Mn1.5O4 cathode for lithium-ion batteries

In this current work, high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) decorated with AlF3 thin layer was successfully synthesized and investigated for the application in Li-ion batteries (LIBs). The electrochemical properties and dissolution behavior of transition metals of the AlF3-modified LNMO electrodes were investigated, especially at elevated temperature. The well-defined and homogeneous AlF3 coating on the surface of LNMO was conducted by a facile chemical modification approach, in which the thickness of AlF3 modification layer was adjusted by adjusting the AlF3 precursor concentrations. After the optimization of the AlF3 precursor concentration, the 1 wt% AlF3-modified LNMO electrode revealed the remarkably improved cyclability especially at elevated temperature. The 1 wt% AlF3-modified LNMO electrode displayed an impressive capacity retention up to 81.7% after charged/discharged at 0.2C at elevated temperature for 100 cycles, which was superior to that of the pristine LNMO electrode (70.1%). Its improved cyclability can be ascribed to the efficient suppression of electrolyte decomposition reaction and transition metal dissolution, thus signaling promising potential in high-voltage LIBs applications.

In situ synchrotron radiation diffraction study of the Li+ de/intercalation behavior in spinel LiNi0.5Mn1.5O4-δ

The oxygen vacancies are usually beneficial to Li-ion transport in high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) cathode material, but the influence of the oxygen deficiencies in the disordered spinel LNMO oxide on phase transition mechanism during charging/discharging remains unknown. Herein, the oxygen stoichiometry control of LNMO was achieved through a microwave annealing treatment. The prepared non-stoichiometric LiNi0.5Mn1.5O4-δ (Fd3-m) materials delivered a pronounced improvement of rate capability, e.g. the discharge capacity at an ultra-fast rate (10 C) is up to 104.3 mA h g−1. Instead of the typical two-step phase transformation process, a solid-solution-like reaction in the as-synthesized LiNi0.5Mn1.5O4-δ (Fd3-m) during cycling was deciphered by an in situ synchrotron radiation diffraction analysis. These findings shed light on the phase transition mechanism of defective spinel oxides with an enhanced electrochemical properties.

Insight into the effect of graphene coating on cycling stability of LiNi0.5Mn1.5O4: Integration of structure-stability and surface-stability

Graphene has presented promising features for application in lithium ion batteries(LIBs) due to its superior electronic conductivity and high surface area. It has been successfully used for modifying cathode materials to meet the increasing demand for LIBs with longer cycle life. However, the improving effect of graphene on cycling stability is still unclear, which restricts its further application in LIBs. Herein, graphene coated hollow sphere-like structure LiNi0.5Mn1.5O4(LNMO) wasdesigned and the improvement mechanism of graphene coating on LNMO’s cycling stability was investigated. The results show that graphene coating not only contributes to suppress structural deformation from mechanistic reaction and extend solid-solution reaction, but also helps protect electrode from corrosion by the products from electrolyte decomposition and suppress the generation of surface defects, especially at high temperature. Owing to graphene coating, graphene coated LNMO can deliver a discharge capacity of 91 mAh g−1 with high capacity retention of 82.5% after 1000 cycles under 20C and 83.8 mAh g−1 with 94.5% capacity retention after 100 cycles under 2C at 55 °C. This work deeply explores the effect of graphene coating on cycling stability from crystal stability and surface stability, which will help a wider application of graphene in energy storage field.

Comparison of fluorine sources on the electrochemical property of Li1.2Ni0.2Mn0.6O2 cathode materials

Li-rich nickel manganese oxide materials are promising cathode materials for their high theoretical capacity and cobalt-free property. However, the poor cycle and rate performance still hamper their commercial application. In this study, fluorine-doped Li1.2Ni0.2Mn0.6O2 (LNMO) materials have been prepared successfully with different fluorine sources. XRD results verified that the (003) and (104) peaks of F-doped samples slightly shift to the lower diffraction angle than bare LNMO, and the large lithium slab distance of F-doped samples is beneficial for the transport and diffusion of Li+. The sample with PVDF as fluorine sources exhibits the best electrochemical performance than other F-doped LNMO samples. Specifically, this sample exhibits a high discharge capacity of 213.5[Formula: see text]mAh g−1 at 0.2 C (2.0–4.8 V), corresponding to a capacity retention of 88.7% after 100 cycles. The excellent electrochemical performance is due to the substitution of fluorine for oxygen sites with the host lattice, which can significantly enhance the Li+ migration and stabilize the layer structure of LNMO during the cycle process. These results demonstrated that PVDF was the best fluorine source to facilitate the electrochemical property of LNMO.

Manganese-Based Lithium-Ion Battery: Mn3O4 Anode Versus LiNi0.5Mn1.5O4 Cathode

Lithium-ion batteries (LIBs) are widely used in portable consumer electronics, clean energy storage, and electric vehicle applications. However, challenges exist for LIBs, including high costs, safety issues, limited Li resources, and manufacturing-related pollution. In this paper, a novel manganese-based lithium-ion battery with a LiNi0.5Mn1.5O4‖Mn3O4 structure is reported that is mainly composed of environmental friendly manganese compounds, where Mn3O4 and LiNi0.5Mn1.5O4 (LNMO) are adopted as the anode and cathode materials, respectively. The proposed structure improves battery safety and reduce costs compared with current battery technology, provides comparable energy density with that of traditional graphite-based batteries. First, the characteristics and the electrochemical performances of the Mn3O4 anode and the LNMO cathode are investigated separately against Li metal in half cell configurations, with promising performances being demonstrated by both electrodes. Then, a full cell structure with Mn3O4 against LNMO is constructed that provides an average discharge voltage of 3.5 V and an initial specific capacity of 86.2 mA·h·g−1. More importantly, the electrochemical performance of the LNMO‖Mn3O4 full cell and its possible decay mechanisms are discussed systemically; and efficient strategies are proposed to further improve both the electrochemical performance of Mn3O4 and the stability of LNMO.

Understanding the Nature of Capacity Decay and Interface Properties in Li//LiNi0.5Mn1.5O4 Cells by Cycling Aging and Titration Techniques

The high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material for next generation lithium-ion batteries for fast charge-discharge applications, but its capacity decay mechanism and ...

Stabilized High-Voltage Cathodes via an F-Rich and Si-Containing Electrolyte Additive.

High-voltage cathodes provide a promising solution to the energy density limitation of currently commercialized lithium-ion batteries, but they are unstable in electrolytes during the charge/discharge process. To address this issue, we propose a novel electrolyte additive, pentafluorophenyltriethoxysilane (TPS), which is rich in elemental F and contains elemental Si. The effectiveness of TPS has been demonstrated by cycling a representative high-voltage cathode, LiNi0.5Mn1.5O4 (LNMO), in 1.0 M LiPF6-diethyl carbonate/ethylene carbonate/ethyl methyl carbonate (2/3/5 in weight). LNMO presents an increased capacity retention from 28 to 85% after 400 cycles at 1 C by applying 1 wt % TPS. Further electrochemical measurements combined with spectroscopic characterization and theoretical calculations indicate that TPS can not only construct a robust protective cathode electrolyte interphase via its oxidation during initial lithium desertion but also scavenge the detrimental hydrogen fluoride (HF) present in the electrolyte via its strong combination with the species HF, F-, and H+, highly stabilizing LNMO during the charge/discharge process. These features of TPS provide a new solution to the obstacle in the practical application of high-voltage cathodes not limited to LNMO.

Passivation of the Cathode-Electrolyte Interface for 5 V-Class All-Solid-State Batteries.

An all-solid-state battery is a potentially superior alternative to a state-of-the-art lithium-ion battery owing to its merits in abuse tolerance, packaging, energy density, and operable temperature ranges. In this work, a 5 V-class spinel LiNi0.5Mn1.5O4 (LNMO) cathode is targeted to combine with a high-ionic-conductivity Li6PS5Cl (LPSCl) solid electrolyte for developing high-performance all-solid-state batteries. Aiming to passivate and stabilize the LNMO-LPSCl interface and suppress the unfavorable side reactions such as the continuous chemical/electrochemical decomposition of the solid electrolyte, oxide materials including LiNbO3, Li3PO4, and Li4Ti5O12 are rationally applied to decorate the surface of pristine LNMO particles with various amounts through a wet-chemistry approach. Electrochemical characterization demonstrates that the composite cathode consisting of 8 wt % LiNbO3-coated LNMO and LPSCl in a weight ratio of 70:30 delivers the best electrochemical performance with an initial discharge capacity of 115 mA h g-1 and a reversible discharge capacity of 80 mA h g-1 at the 20th cycle, suggesting that interfacial passivation is an effective strategy to ensure the operation of 5 V-class all-solid-state batteries.

Temperature-controlled synthesis of spinel lithium nickel manganese oxide cathode materials for lithium-ion batteries

In this work, we successfully synthesized series of LiNi0.5Mn1.5O4 (LNMO) cathode materials with spinel structure by using a facile sol-gel method and then calcined at various temperature ranging from 600 to 1000 °C. The application of different calcination temperatures significantly influenced the surface morphology, stoichiometry and crystalline nature of the as-synthesized LNMO material. According to the results of physical characterizations, the LNMO materials calcined at various temperatures mainly revealed the stoichiometric disordered Fd-3m structure with a small amount of well-ordered P4332 phase. The structural analysis also exhibited that the control of the calcination temperature contributed to the higher crystalline nature. Moreover, the morphological investigations indicated that the increasing calcination temperatures caused the formation of large micron-sized LNMO material. In turn, the electrochemical evaluations revealed the impact of the calcination temperatures on enhancing the electrochemical performances of the LNMO electrode materials up to 900 °C. The LNMO electrode calcined at 900 °C exhibited an impressive initial discharge specific capacity of ca. 142 mAh g−1 between 3.5 and 4.9 V vs. Li/Li+, and remarkably improved capacity retention of 97% over 50 cycles. Those excellent electrochemical properties were associated with the presence of the dominant Fd-3m phase over the P4332 phase. Additionally, the results of the corrosion and dissolution tests which were performed for all calcined LNMO materials in order to estimate the amount of manganese and nickel ions leached from them, proved that the micro-sized LNMO calcined at 900 °C was the most stable.

Improved Adhesion of Nafion™-Coated Separator to Water-Processable LiNi0.5Mn1.5O4 Electrodes

The adhesion between electrode and separator is a key feature in cell assembly. Nafion™-coated separators for water-processed LiNi0.5Mn1.5O4 (LNMO) electrodes are here proposed as an alternative to the polyolefin separators. Specifically, polyolefin separators are modified with Nafion™ solutions and their adhesion to high-potential LNMO electrodes is investigated. The physicochemical properties of the Nafion™-coated separator and its electrochemical performance in Li/LNMO cells are discussed and compared to those obtained with polyolefin Celgard® (Charlotte, NC, USA) PP2075 separator. Improved adhesion and cycling stability, which could be further enhanced by a mild lamination process, were demonstrated with a thin layer of Nafion™ (0.1 mg cm−2).

Stable Cycling of High-Voltage Lithium-Metal Batteries Enabled by High-Concentration FEC-Based Electrolyte.

Functional electrolytes that are stable toward both Li-metal anode and high-voltage (>4 V vs Li/Li+) cathodes play a critical role in the development of high-energy density Li-metal batteries. Traditional carbonate-based electrolytes can hardly be used in high-voltage Li-metal batteries due to the dendritic Li deposits, low Coulombic efficiency, and anodic instability in the presence of aggressive cathodes. Herein, we design a concentrated dual-salt electrolyte that achieves high stability for both Li anodes and high-voltage cathodes of LiNi0.5Mn1.5O4 (LNMO) and LiNi0.7Co0.15Mn0.15O2 (NCM). A Li||Cu cell in the designed electrolyte shows a high Coulombic efficiency of >98% in long-term plating/stripping for 900 cycles. Li||LNMO and Li||NCM cells achieve a capacity retention of 88.5% over 500 cycles and 86.2% over 200 cycles with a cutoff voltage of 4.9 and 4.3 V, respectively. The Li||LNMO full cell with a cathode areal capacity of 1.8 mAh/cm2 and only 3× excess Li was fabricated, and it delivered a high capacity retention of 87.8% after 100 cycles. The reasons for the good cycling stability of the cells in a concentrated dual-salt electrolyte can be attributed to the reversible dendrite-free plating/stripping of a Li-metal anode and stable interfacial layers on both anode and cathode.

Crystal engineering of TMPOx-coated LiNi0.5Mn1.5O4 cathodes for high-performance lithium-ion batteries

The use of cobalt-free LiNi0.5Mn1.5O4 (LNMO) would provide a great leap forward towards the realization of sustainable lithium-ion batteries. However, the high operating voltage remains to be a great challenge for the cathode/electrolyte stability. Herein, we report a rational material design to address these challenges by carefully tuning the synthesis parameters in order to engineer LNMO crystals with tailored surface facets, providing an exceptional rate capability and improved interfacial stability. The additional introduction of protective TMPOx coatings further enhances the long-term cycling stability, in particular, at elevated cut-off potentials up to 4.95 V, increased temperature of 40 °C, and high dis-/charge rates. As a result of the careful design of the LNMO active material particles, lithium-ion cells employing this material together with Li4Ti5O12 anodes provide an excellent rate capability with 80% of the low-rate capacity at fast dis-/charge rates of 10C combined with highly stable cycling at such high rate, as highlighted by a capacity fading of less than 5% after 1000 cycles.

A Long Cycle-Life High-Voltage Spinel Lithium-Ion Battery Electrode Achieved by Site-Selective Doping.

Spinel LiNi0.5 Mn1.5 O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2 O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices.

A Long Cycle‐Life High‐Voltage Spinel Lithium‐Ion Battery Electrode Achieved by Site‐Selective Doping

AbstractSpinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next‐generation high energy‐density lithium‐ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site‐selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd m structure. This site‐selective doping not only suppresses unfavorable two‐phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg‐doped LNMOs exhibit extraordinarily stable electrochemical performance in both half‐cells and prototype full‐batteries with novel TiNb2O7 counter‐electrodes. This work pioneers an atomic‐doping engineering strategy for electrode materials that could be extended to other energy materials to create high‐performance devices.

Electrolyte Therapy for Improving the Performance of LiNi0.5Mn1.5O4 Cathodes Assembled Lithium-Ion Batteries.

High voltage spinel manganese oxide LiNi0.5Mn1.5O4 (LNMO) cathodes are promising for practical applications owing to several strengths including high working voltages, excellent operating safety, low costs, and so on. However, LNMO-based lithium-ion batteries (LIBs) fade rapidly mainly owing to unqualified electrolytes, hence becoming a big obstacle toward practical applications. To tackle this roadblock, substantial progress has been made thus far, and yet challenges still remain, while rare reviews have systematically discussed the status quo and future development of electrolyte optimization coupling with LNMO cathodes. Here, we discuss cycling degradation mechanisms at the cathode/electrolyte interface and ideal requirements of electrolytes for LNMO cathode-equipped LIBs, as well as review the recent advance of electrolyte optimization for LNMO cathode-equipped LIBs in detail. And then, the perspectives regarding the future research opportunities in developing state-of-the-art electrolytes are also presented. The authors hope to shed light on the rational optimization of advanced organic electrolytes in order to boost the large-scale practical applications of high voltage LNMO cathode-based LIBs.