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Lithium-rich layered oxides (LLOs) hold the promise for high-energy battery cathodes. However, its application has been hindered by voltage decay associated with irreversible reactions at high voltages despite decades of intensive efforts. Here, we first theoretically studied the molecular orbitals of Mn-based Li-rich configurations. We found that the π-bond ring formed within the LiMn6 structure could participate in stable redox reactions as one unit, but Co could disrupt its symmetry. We thus designed and synthesized Co-free concentration-gradient LLOs (CF-CG-LLOs) materials. The combination of concentration gradient and Co removal leads to exceptional capacity retention without any fading over 100 cycles of the pouch cell. More importantly, it exhibits an extraordinarily low voltage decay of 0.15 mV/cycle, accompanied by a high Coulombic efficiency of 99.86%. This concept and demonstration of CF-CG-LLO cathodes reveal a viable avenue toward low-cost, high-energy-density battery cathodes. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LLOs) have gained significant attention due to their high capacity of over 250 mAh g−1, which originates from the charge compensation of oxygen anions activated under high voltage. However, the charge compensation of oxygen anions is prone to over‐oxidation, leading to serious irreversible oxygen release, surface‐interface reactions, and structural evolution. These detriments make LLOs undergo fast voltage decay and capacity fading, which have hindered their practical applications for many years. Herein, this work develops a multifunctional co‐doping strategy and constructs W─O bonds with strong bonding interaction and covalence, low bond energy Li─S bonds with non‐binding electrons near the Fermi level, and continuous and homogeneous surface spinel‐like layer induced by W/S co‐doping. Their synergistic effect significantly mitigates the irreversible oxygen release and surface‐interface reactions and improves structural stability of Li‐rich layered cathodes. Thus, the designed and prepared Co‐free Li‐rich layered cathode (Li1.232Mn0.574Ni0.191W0.003O1.995S0.005) delivers superior voltage and capacity stability. Its capacity retention after 400 cycles is as large as 86%, and its voltage decay rate from the 10th to the 400th cycle is only 0.626 mV cycle−1. [ABSTRACT FROM AUTHOR]

Li‐rich cathode materials (LRMs) are regarded as the key cathode candidates for next‐generation lithium‐ion batteries(LIBs) because of their high specific capacity and environmental friendliness. However, LRMs encounter poor cyclability and low initial coulombic efficiency (ICE) hindering their practical application. Herein, a general near‐surface in situ reconstruction strategy is proposed of constructing the Li/O dual vacancies and spinel‐carbon dual coating layers on the surface of LRMs concurrently to improve Li+ storage performance. The as‐prepared LRMs exhibit a greatly strengthened specific capacity of 283 mAh g−1 with an enhanced ICE of 94% and long‐term cyclability of 91% retention after 200 cycles compared with the pristine LRMs (212 mAh g−1 with an ICE of 65%, 76% retention after 200 cycles). Furthermore, it is theoretically revealed that O vacancies (Ov) prefer to occur at the interface of the C2/m and R3¯$\bar{3}$m phases to mitigate lattice stress, rather the O sites in individual C2/m or R3¯$\bar{3}$m phase with more coordinated atoms. Besides, Li ions exhibit lower migration energy from C2/m phase to R3¯$\bar{3}$m phase with the Ov located at the lattice interface. Therefore, this strategy opens a new avenue in the design perspective of the LRMs' near‐surface for high‐energy‐density LIBs. [ABSTRACT FROM AUTHOR]

Full concentration gradient lithium‐rich layered oxides are catching lots of interest as the next generation cathode for lithium‐ion batteries due to their high discharge voltage, reduced voltage decay and enhanced rate performance, whereas the high lithium residues on its surface impairs the structure stability and long‐term cycle performance. Herein, a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium‐rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post‐annealing process. It realizes not only a stable Li2TiO3 coating layer with 3D diffusion channels for fast Li+ ions transfer, but also dopes partial Ti4+ ions into the sub‐surface region of full concentration gradient lithium‐rich layered oxides to further strengthen its crystal structure. Consequently, the modified full concentration gradient lithium‐rich layered oxides exhibit improved structure stability, elevated thermal stability with decomposition temperature from 289.57 °C to 321.72 °C, and enhanced cycle performance (205.1 mAh g−1 after 150 cycles) with slowed voltage drop (1.67 mV per cycle). This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium‐rich layered oxides, which can facilitate its practical application for developing higher energy density lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LROs) are considered as promising cathodes in building next-generation lithium-ion batteries (LIBs) with superior charge-discharge capacity. Nevertheless, LROs are confronted with irreversible oxygen loss accompanied with surface-to-bulk degradation upon cycling. To inhibit the oxygen release and to increase the lifespan of LROs, we report on an innovative strategy to rapidly construct an ultrathin oxygen-deficient shell layer covering the surface of LROs’ particles via a sparking plasma sintering (SPS) technique. It is demonstrated that the inner structure of the LROs’ particles is maintained, whereas the surface of the particles forms a thin shell (∼5 nm) consisting of a considerable amount of oxygen vacancies. Benefitting from the existence of an oxygen-deficient shell, the cathode activation is facilitated and the oxygen loss is suppressed, leading to enhanced capacity and prominent cyclability under long cycling. The modified LRO exhibits outstanding electrochemical performance, delivering a maximum capacity of 187.67 mAh g−1 and a capacity retention of 95.71% after 200 cycles at 250 mA g−1. Our work evidences that SPS is a fast and effective approach to construct oxygen-deficient shell on LRO cathodes for high-performance LIBs.

Lithium‐rich layered oxides (LLOs, Li1.2Mn0.54Ni0.13Co0.13O2) are widely used as cathode materials for lithium‐ion batteries due to its high specific capacity, high operating voltage and low cost. However, the LLOs are faced with rapid decay of charge/discharge capacity and voltage, as well as interface side reactions, which limit its electrochemical performance. Herein, the dual strategies of sulfite/sodium ion co‐doping and lithium carbonate coating were used to improve it. It founds that modified LLOs achieve 88.74 % initial coulomb efficiency, 295.3 mAh g−1 first turn discharge capacity, in addition to 216.9 mAh g−1 at 1 C, and 87.23 % capacity retention after 100 cycles. Mechanism research indicated that the excellent electrochemical performance benefits from the doping of both Na+ and SO32−, and it could significantly reduce the migration energy barrier of Li+ and promote Li+ migration. Meanwhile, anion and cation are co‐doped greatly reduces the band gap of LLOs and increase its electrical conductivity, and its binding effect on Li+ is weakened, making it easier for Li+ to shuttle through the material. In addition, the lithium carbonate coating significantly inhibits the occurrence of interfacial side reactions of LLOs. This work provides a theoretical basis and practical guidance for the further development of LLOs with higher electrochemical performance. [ABSTRACT FROM AUTHOR]

High‐capacity Li‐rich layered oxides using oxygen redox as well as transition metal redox suffer from its structural instability due to lattice oxygen escaped from its structure during oxygen redox and the following electrolyte decomposition by the reactive oxygen species. Herein, we rescued a Li‐rich layered oxide based on 4d transition metal by employing an organic superoxide dismutase mimics as a homogeneous electrolyte additive. Guaiacol scavenged superoxide radicals via dismutation or disproportionation to convert two superoxide molecules to peroxide and dioxygen after absorbing lithium superoxide on its partially negative oxygen of methoxy and hydroxyl groups. Additionally, guaiacol was decomposed to form a thin and stable cathode‐electrolyte interphase (CEI) layer, endowing the cathode with the interfacial stability. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LLOs) are promising candidate cathode materials for safe and inexpensive high‐energy‐density Li‐ion batteries. However, oxygen dimers are formed from the cathode material through oxygen redox activity, which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns. Herein, a flake‐like LLO is prepared and aberration‐corrected scanning transmission electron microscopy (STEM), in situ high‐temperature X‐ray diffraction (HT‐XRD), and soft X‐ray absorption spectrum (sXAS) are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes. Void‐induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage. Particle degradation originates from side facets, such as the (010) facet, while the close (003) facet is stable. These results are further understood through ab initio molecular dynamics calculations, which show that oxygen atoms are lost from the {010} facets. Therefore, the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating, which result in crevice‐voids in the ab plane facets. The study reveals important aspects of the mechanism responsible for oxygen ‐anionic activity‐based degradation of LLO cathode materials used in lithium‐ion batteries. In particular, this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LROs) are one class of the most competitive high‐capacity cathode materials due to their anion/cation synergistic redox activity. However, excessive oxidation of the oxygen sublattices can induce serious oxygen loss and structural imbalance. Hence, a near‐surface reconfiguration strategy by fluorinating graphene is proposed to precisely regulate Mn3+/Mn4+ and O2−/(O2)n− redox couples for remarkably stabilizing high‐capacity LROs and realizing the simultaneous reduction of the lattice stress, regulation of the Mn metal at a lower charge state, and construction of 3D Li+ diffusion channels. Combining with a highly conductive graphene‐coating layer, the surface oxygen loss, transition metal dissolution, and electrolyte catalytic decomposition are suppressed. Benefiting from this synergy, the modified LROs disclose higher initial Coulombic efficiency and discharge‐specific capacity and improve cyclability compared with pristine LROs. Further, it is revealed that the F− impact becomes easier for the O sites at the lattice interface of C2/m and R3¯$\bar{3}$m to sufficiently buffer lattice stress. Moreover, lithium ions coupled to the doped F atoms at the lattice interface migrate to the Ni‐rich R3¯$\bar{3}$m lattice sites with lower migration energies. This consolidated understanding will open new avenues to regulate reversible oxygen redox of LROs for high‐energy‐density lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxide (LLO) are considered high-capacity cathode materials for next-generation lithium-ion batteries. In this study, LLO cathode materials were synthesized via the hydroxide coprecipitation method followed by a two-step lithiation process using different lithium contents and lithium sources. The effects of lithium content and lithium source on structure and electrochemical performance were investigated. This study demonstrated the clear impact of Li/TM ratio on electrochemical performance. Lower Li/TM ratio reduced the irreversible capacity loss in the first cycle and provided better cycling stability among all samples. The best results exhibited an initial discharge capacity of 279.65 mAh g−1 and reached a discharge capacity of 231.9 mAh g−1 (82.9% capacity retention) after 30 cycles. The sample using Li2CO3 as lithium source exhibits better electrochemical performance than the sample using LiOH as lithium source. Therefore, it is important to choose the appropriate lithium source and optimal lithium content for improving structural properties and electrochemical performance of LLO. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO2, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg−1, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling. [ABSTRACT FROM AUTHOR]

As one of the high‐energy cathode materials of lithium‐ion batteries (LIBs), lithium‐rich‐layered oxide with "single‐crystal" characteristic (SC‐LLO) can effectively restrain side reactions and cracks due to the reduced inner boundaries and enhanced mechanical stabilities. However, there are still high challenges for SC‐LLO with diverse performance requirements, especially on their cycle stability improvement. Herein, a novel concentration gradient "single‐crystal" LLO (GSC‐LLO), with gradually decreasing Mn and increasing Ni contents from center to surface, is designed and prepared by combining co‐precipitation and molten‐salt sintering methods, yielding a capacity retention of 97.6% and an energy density retention of 95.8% within 100 cycles at 0.1 C. The enhanced performance is mostly attributed to the gradient‐induced stabilized structure, free of cracks and less spinel‐like structure formation after long‐term cycling. Furthermore, the gradient design is also beneficial to the safety of LLOs as suggested by the improved thermal stability and reduced gas release. This study provides an effective strategy to prepare high‐energy, high‐stability, and high‐safety LLOs for advanced LIBs. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are considered a promising energy storage technology in portable electronics and electric vehicles due to their high energy density, competitive cost, and environmental friendliness. Improving cathode materials is an effective way to meet the demand for better batteries, of which the utilization of high-voltage cathode materials is an important development trend. In recent years, lithium-rich layered oxides have gained great attention due to their desirable energy density. This review presents the relationships between lattice structure and electrochemical properties, the underlying degradation mechanisms, and corresponding modification strategies. The recent progress and strategies are then highlighted, including element doping, surface coating, morphology design, size control, etc. Finally, a concise perspective for future developments and practical applications of lithium-rich layered oxides has been provided. [ABSTRACT FROM AUTHOR]

Elemental doping is widely used to improve the performance of cathode materials in lithium-ion batteries. However, macroscopic/statistical investigation on how doping sites are distributed in the material lattice, despite being a key prerequisite for understanding and manipulating the doping effect, has not been effectively established. Herein, to solve this predicament, a universal strategy is proposed to quantitatively identify the locations of Al and Mg dopants in lithium-rich layered oxides (LLOs). Solid evidence confirms that Al prefers to occupy the transition metal (TM) layer, while Mg evenly occupies both TM and Li layers. As a result, Mg significantly reduces the thickness of LiO 2 slabs at room temperature, which will increase the energy barrier of oxygen activation and enhance the structure stability of LLOs. The suppressed oxygen activity in Mg-doped LLO can be kinetically unlocked at 55 °C. The different characteristics of Al and Mg enlighten an Al/Mg co-doping strategy to optimize LLOs, which significantly improves the cycle performance while lifting the capacity. These insights from the quantitative identification of doping sites shed light on the manipulation of doping effects toward better cathodes., (© 2024 Wiley‐VCH GmbH.)

Abstract Lithium‐rich layered oxides (LLOs) with high energy density and low cost are regarded as promising candidates for the next‐generation cathode materials for lithium‐ion batteries (LIBs). However, there are still some drawbacks of LLOs such as oxygen instability and irreversible structure reconstruction, which seriously limit their electrochemical performance and practical applications. Herein, the high‐valence Ta doping is proposed to adjust the electronic structures of transition metals, which form strong Ta‐O bonds and reduce the covalency of Ni‐O bonds, thereby stabilizing the lattice oxygen and enhancing the structural/thermal stabilities of LLOs during electrochemical cycling. As a result, the optimized Ta‐doped LLO can deliver a capacity retention of 80% and voltage decay of 0.34 mV cycle−1 after 650 cycles at 1C. This study enriches the fundamental understanding of the electronic structure adjustment of LLOs and contributes to the optimization of LLOs for high‐energy LIBs.

Activation of oxygen redox during the first cycle has been reported as the main trigger of voltage hysteresis during further cycles in high‐energy‐density Li‐rich 3d‐transition‐metal layered oxides. However, it remains unclear whether hysteresis only occurs due to oxygen redox. Here, it is identified that the voltage hysteresis can highly correlate to cationic reduction during discharge in the Li‐rich layered oxide, Li1.2Ni0.4Mn0.4O2. In this material, the potential region of discharge accompanied by hysteresis is apparently separated from that of discharge unrelated to hysteresis. The quantitative analysis of soft/hard X‐ray absorption spectroscopies discloses that hysteresis is associated with an incomplete cationic reduction of Ni during discharge. The galvanostatic intermittent titration technique shows that the inevitable energy consumption caused by hysteresis corresponds to an overpotential of 0.3 V. The results unveil that hysteresis can also be affected by cationic redox in Li‐rich layered cathodes, implying that oxygen redox cannot be the only reason for the evolution of voltage hysteresis. Therefore, appropriate control of both cationic and anionic redox of Li‐rich layered oxides will allow them to reach their maximum energy density and efficiency. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide (LRLO) materials are promising positive-electrode materials for Li-ion batteries. Antisite defects, especially nickel and lithium ions, occur spontaneously in many LRLOs, but their impact on the functional properties in batteries is controversial. Here, we illustrate the analysis of the formation of Li/Ni antisite defects in the layered lattice of the Co-free LRLO Li1.2Mn0.6Ni0.2O2 compound through a combination of density functional theory calculations performed on fully disordered supercells and a thermodynamic model. Our goal was to evaluate the concentration of antisite defects in the trigonal lattice as a function of temperature and shed light on the native disorder in LRLO and how synthesis protocols can promote the antisite defect formation. [ABSTRACT FROM AUTHOR]

The instability of the electrode-electrolyte interface in high-voltage cathode materials significantly hinders the development of high-energy-density lithium-ion batteries (LIBs). In this study, 1,3-diphenyl-1,1,3,3-tetramethyldisiloxane (DTS) is employed as an electrolyte additive to enhance the cycling stability and capacity retention for Li||LLO (Li-rich layered oxide) batteries operating at 4.8 V. Theoretical calculations show that DTS can preferentially oxidize on the surface of the cathode. The oxidation forms a robust cathode electrolyte interface (CEI) on the LLO surface, significantly mitigating cracking, regeneration, and irreversible phase transitions of the LLO cathode. As anticipated, the Li||LLO batteries with the DTS electrolyte exhibit a capacity retention of 85.4% after 100 cycles at 4.8 V compared to the baseline electrolyte (45.2%). Furthermore, these batteries demonstrate superior capacity retention after 100 cycles at 4.8 V, even with the presence of 1000 ppm of H 2 O.

Lithium-rich layered oxide (LLO) are considered high-capacity cathode materials for next-generation lithium-ion batteries. In this study, LLO cathode materials were synthesized via the hydroxide coprecipitation method followed by a two-step lithiation process using different lithium contents and lithium sources. The effects of lithium content and lithium source on structure and electrochemical performance were investigated. This study demonstrated the clear impact of Li/TM ratio on electrochemical performance. Lower Li/TM ratio reduced the irreversible capacity loss in the first cycle and provided better cycling stability among all samples. The best results exhibited an initial discharge capacity of 279.65 mAh g−1 and reached a discharge capacity of 231.9 mAh g−1 (82.9% capacity retention) after 30 cycles. The sample using Li2CO3 as lithium source exhibits better electrochemical performance than the sample using LiOH as lithium source. Therefore, it is important to choose the appropriate lithium source and optimal lithium content for improving structural properties and electrochemical performance of LLO.

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li1+xTM1−xO2, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg−1, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling.

Featured Application: Environmentally friendly positive electrode materials for high-capacity lithium-ion batteries. The replacement of cobalt in the lattice of lithium-rich layered oxides (LRLO) is mandatory to improve their environmental benignity and reduce costs. In this study, we analyze the impact of the cobalt removal from the trigonal LRLO lattice on the structural, thermodynamic, and electronic properties of this material through density functional theory calculations. To mimic disorder in the transition metal layers, we exploited the special quasi-random structure approach on selected supercells. The cobalt removal was modeled by the simultaneous substitution with Mn/Ni, thus leading to a p-doping in the lattice. Our results show that cobalt removal induces (a) larger cell volumes, originating from expanded distances among stacked planes; (b) a parallel increase of the layer buckling; (c) an increase of the electronic disorder and of the concentration of Jahn–Teller defects; and (d) an increase of the thermodynamic stability of the phase. Overall p-doping appears as a balanced strategy to remove cobalt from LRLO without massively deteriorating the structural integrity and the electronic properties of LRLO. [ABSTRACT FROM AUTHOR]

The utilization of lithium-rich layered oxides (LLOs) materials shows promising possibilities for the innovation of high-capacity Li-ion batteries with enhanced energy density. However, their practical applications are limited by continuous voltage decay, inferior cycling stability, and poor rate capability. In this work, a novel doping strategy is proposed, where PrPO 4 is introduced during the high-temperature solid-state reaction to prepare Co-free Li-rich layered oxides. It is found that other than as a dopant, PrPO 4 can activate Li 2 MnO 3 to form well-distributed Pr 0.96 Mn 0.982 O 3 and Li 3 PO 4 in LLOs particles, which availably suppresses the phase transition. The obtained material increases the initial coulombic efficiency (ICE) from 75.8% to 84.1%, and improves capacity retention from 74.6% to 90.9% compared with the pristine material. Meanwhile, the average voltage decay decreases from 2.33 mV/cycle to 1.25 mV/cycle over 200 cycles. This work provides valuable insights into the development of LLOs using rare-earth phosphate, offering valuable knowledge for further advancements in this field. [Display omitted] • PrPO 4 doping is proposed to enhance the electrochemical performance of the Co-free Li-rich layered oxide. • PrPO 4 successfully activate Li 2 MnO 3 to improve the sluggish kinetic of Li 2 MnO 3 phase. • PrPO 4 doping effectively suppress layered to spinel/rock-salt phase transition of Lithium-rich layered oxides. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide (LRLO) materials are promising positive-electrode materials for Li-ion batteries. Antisite defects, especially nickel and lithium ions, occur spontaneously in many LRLOs, but their impact on the functional properties in batteries is controversial. Here, we illustrate the analysis of the formation of Li/Ni antisite defects in the layered lattice of the Co-free LRLO Li1.2Mn0.6Ni0.2O2 compound through a combination of density functional theory calculations performed on fully disordered supercells and a thermodynamic model. Our goal was to evaluate the concentration of antisite defects in the trigonal lattice as a function of temperature and shed light on the native disorder in LRLO and how synthesis protocols can promote the antisite defect formation.

Lithium-rich layered oxides have the advantages of high specific capacity (> 250 mAh g−1) and high energy density, which make them highly competitive in the lithium-ion cathode material market. However, low efficiency, poor cycle stability, and poor rate performance severely constrained their development. In this paper, the spherical lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 compound was rapidly synthesized by microwave hydrothermal method, and the microwave hydrothermal time was optimized. The samples were characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS). The prepared lithium-rich compound is porous spherical secondary particles, of which the size distributed between 2.5 and 3.5 μm, which makes materials have larger specific surface area and active potential and promotes the improvement of electrochemical kinetics. The results of 100 charge-discharge cycles show that the microwave hydrothermal 40-min cathode has good stability, and the capacity retention rate can reach 91.4%. Furthermore, it can still provide a discharge capacity of 160.5 mAh g−1 at a current density of 5 C. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LRLOs) exhibit specific capacities above 250 mAh g−1, i.e., higher than any of the commercially employed lithium‐ion‐positive electrode materials. Such high capacities result in high specific energies, meeting the tough requirements for electric vehicle applications. However, LRLOs generally suffer from severe capacity and voltage fading, originating from undesired structural transformations during cycling. Herein, the eco‐friendly, cobalt‐free Li1.2Ni0.2Mn0.6O2 (LRNM), offering a specific energy above 800 Wh kg−1 at 0.1 C, is investigated in combination with a lithium metal anode and a room temperature ionic liquid‐based electrolyte, i.e., lithium bis(trifluoromethanesulfonyl)imide and N‐butyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide. As evidenced by electrochemical performance and high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and online differential electrochemical mass spectrometry characterization, this electrolyte is capable of suppressing the structural transformation of the positive electrode material, resulting in enhanced cycling stability compared to conventional carbonate‐based electrolytes. Practically, the capacity and voltage fading are significantly limited to only 19% and 3% (i.e., lower than 0.2 mV per cycle), respectively, after 500 cycles. Finally, the beneficial effect of the ionic liquid‐based electrolyte is validated in lithium‐ion cells employing LRNM and Li4Ti5O12. These cells achieve a promising capacity retention of 80% after 500 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LROs) possess enormous potential in the new generation of high-energy lithium-ion batteries due to their high specific capacity, working voltage, and low cost. However, they still face low initial coulombic efficiency, poor cycling stability and multiplication performance, and persistent voltage decay, which seriously hinder their development in the lithium-ion battery industry. In this article, the Li 1·4 Y 0·4 Ti 1·6 (PO 4) 3 ionic conductive layer is constructed on the surface of LROs using surface residuals as lithium sources. Such a one-step modification method not only improves the rate performance of LROs by enhanced kinetic property of Li+, but also elongates the cycling lives at high-temp and high-rates by the inhibition of interfacial side reactions. As a result, the LRO cathode with a high initial coulombic efficiency of 89.3% and a good capacity retention of 83.2% after 200 cycles at 1C is obtained. It is noteworthy that this multifunctional surface modification strategy can stimulate the potential of LROs in lithium-ion batteries and provide a new way to stabilize their structure. [Display omitted] • Surface lithium residues were utilized to construct LYTP coating on LROs. • The LYTP modification suppresses the irreversible oxygen release of LROs. • The modified LRO exhibits improved capacity, cycling and rate capabilities. [ABSTRACT FROM AUTHOR]

The replacement of cobalt in the lattice of lithium-rich layered oxides (LRLO) is mandatory to improve their environmental benignity and reduce costs. In this study, we analyze the impact of the cobalt removal from the trigonal LRLO lattice on the structural, thermodynamic, and electronic properties of this material through density functional theory calculations. To mimic disorder in the transition metal layers, we exploited the special quasi-random structure approach on selected supercells. The cobalt removal was modeled by the simultaneous substitution with Mn/Ni, thus leading to a p-doping in the lattice. Our results show that cobalt removal induces (a) larger cell volumes, originating from expanded distances among stacked planes; (b) a parallel increase of the layer buckling; (c) an increase of the electronic disorder and of the concentration of Jahn–Teller defects; and (d) an increase of the thermodynamic stability of the phase. Overall p-doping appears as a balanced strategy to remove cobalt from LRLO without massively deteriorating the structural integrity and the electronic properties of LRLO.

Single-crystal lithium-rich layered oxides (LLOs) with excellent mechanical properties can enhance their crystal structure stability. However, the conventional methods for preparing single-crystal LLOs, require large amounts of molten salt additives, involve complicated washing steps, and increase the difficulty of large-scale production. In this study, a sodium tungstate (Na 2 WO 4 )-assisted sintering method is proposed to fabricate high-performance single-crystal LLOs cathode materials without large amounts of additives and additional washing steps. During the sintering process, Na 2 WO 4 promotes particle growth and forms a protective coating on the surface of LLOs particles, effectively suppressing the side reactions at the cathode/electrolyte interface. Additionally, trace amounts of Na and W atoms are doped into the LLOs lattice via gradient doping. Experimental results and theoretical calculations indicate that Na and W doping stabilizes the crystal structure and enhances the Li + ions diffusion rate. The prepared single-crystal LLOs exhibit outstanding capacity retention of 82.7% (compared to 65.0%, after 200 cycles at 1 C) and a low voltage decay rate of 0.76 mV per cycle (compared to 1.80 mV per cycle). This strategy provides a novel pathway for designing the next-generation high-performance cathode materials for Lithium-ion batteries (LIBs)., (© 2023 Wiley‐VCH GmbH.)

Lithium-rich layered oxides (LLOs) have been extensively studied as cathode materials for lithium-ion batteries (LIBs) by researchers all over the world in the past decades due to their high specific capacities and high charge-discharge voltages. However, as cathode materials LLOs have disadvantages of significant voltage and capacity decays during the charge-discharge cycling. It was shown in the past that fine-tuning of structures and compositions was critical to the performances of this kind of materials. In this report, LLOs with target composition of Li1.17Mn0.50Ni0.24Co0.09O2 were prepared by carbonate co-precipitation method with different pH values. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and electrochemical impedance spectroscopies (EIS) were used to investigate the structures and morphologies of the materials and to understand the improvements of their electrochemical performances. With the pH values increased from 7.5 to 8.5, the Li/Ni ratios in the compositions decreased from 5.17 to 4.64, and the initial Coulombic efficiency, cycling stability and average discharge voltages were gained impressively. Especially, the material synthesized at pH = 8.5 delivered a reversible discharge capacity of 263 mAhg−1 during the first cycle, with 79.0% initial Coulombic efficiency, at the rate of 0.1 C and a superior capacity retention of 94% after 100 cycles at the rate of 1 C. Furthermore, this material exhibited an initial average discharge voltage of 3.65 V, with a voltage decay of only 0.09 V after 50 charge-discharge cycles. The improved electrochemical performances by varying the pH values in the synthesis process can be explained by the mitigation of layered-to-spinel phase transformation and the reduction of solid-electrolyte interface (SEI) resistance. We hope this work can shed some light on the alleviation of voltage and capacity decay issues of the LLOs cathode materials. [ABSTRACT FROM AUTHOR]

In order to alleviate the capacity and voltage attenuation of the Li-rich materials, a series of tungsten-doped Li1.2Mn0.54-xNi0.13Co0.13WxO2 (0 ≤ x ≤ 0.04) were produced through a sol-gel method. The XRD patterns exhibit a representative structure of hexagonal α-NaFeO2 and a well-layered structure. XPS index that the valence of W is 6+. From the results of charge-discharge cycling, appropriate W doping for Li-rich layered oxides can prominently raise its performance. After 100 cycles, the 0.02W-doped sample obtain a capacity retention ratio of 82.6% (154.7 mAh g−1) at 1 C, but the ratio for the pure sample only is 77.5% (121.7 mAh g−1) at the same conditions. Meanwhile, the 0.02W-doped sample can obtain the best properties at different rates. The results reveal that the modification method of W-doping can stabilize the structure of the Li-rich materials and enhance the properties. [ABSTRACT FROM AUTHOR]

Summary: Lithium‐rich layered oxides (LRLOs) are highly attractive cathode materials for next‐generation lithium‐ion batteries because of their high reversible capacity, but poor cycle performance and voltage decay are two main problems that strongly limit their practical applications. These challenges also apply to the Ru‐based LRLOs of Li2RuO3. The Li2RuO3 cathode material is highly attractive because of their high conductivity and favourable electrochemical reaction kinetics. To overcome the problems associated with Li2RuO3, in contrast to normal single atom doping, here, we propose a Na, Cr co‐doping strategy with the design of Li2−xNaxRu0.95Cr0.05O3 (x = 0, 0.02, 0.06, and 0.1) series materials. Cr doping increases capacity, and Na doping suppresses voltage decay. As a result, the discharge capacity of the optimal Li1.98Na0.02Ru0.95Cr0.05O3 sample over 240 mAh/g after 50 charge‐discharge cycles at 0.2 C is maintained, and the capacity retention reaches a value of 80.5% compared with 69.1% for the undoped Li2RuO3. The value of the voltage decay in the Li1.98Na0.02Ru0.95Cr0.05O3 sample is 125 mV after 100 cycles at a rate of 1 C, and the voltage decay is 188.4 mV for the undoped Li2RuO3. This finding will expand the scope for designing novel layered electrodes with excellent performance. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides are promising cathode materials for lithium-ion batteries due to their high reversible capacities (more than 250 mAh g−1). Nevertheless, in operation, the oxygen lattice would be transformed into O 2 gas with phase transformation. Thus, to suppress O 2 gas, it is necessary to pre-generate the oxygen vacancies in the surface of materials. Herein, for facile and scalable pre-generation of oxygen vacancies, pristine Li 2 MnO 3 ·LiNi 1/3 Co 1/3 Mn 1/3 O 2 oxide (PLR-NCM) is treated directly by CO 2 gas just at the room temperature. The modified material (MLR-NCM), with rich oxygen vacancies in the surface and no obvious structural change inside, shows a discharge capacity of 321 mAh g−1 based on half-cells at 55 °C and 0.1 C (1.0 C = 250 mA g−1), and 240 mAh g−1 as full cells at the room temperature. In addition, it also exhibits high cycling and rate performance owing to the significantly improved lithium ion and electron diffusion efficiencies. Importantly, by real-time monitoring of structural evolution using in situ XRD technique, we find that the O 2 gas release of the modified material is successfully suppressed. This facile method proposed in our work provides a new strategy for greatly improving the performance of lithium-ion batteries. Image 1 • Modified Li-rich layered materials (MLR-NCM) with rich oxygen vacancies are prepared. • Oxygen vacancies in MLR-NCM are formed by facile and scalable direct CO 2 treatments. • MLR-NCM show high Li-storage capacity, cycling and rate performances. • In situ XRD technique is used to confirm that oxygen vacancies suppress O 2 release. • Full cells with MLR-NCM perform excellent Li-storage performance at room temperature. [ABSTRACT FROM AUTHOR]

Abstract Lithium-rich layered oxide materials are considered as one of the most promising cathodes for high-energy lithium-ion batteries. However, their practical applications are currently restricted by its low initial Coulombic efficiency and poor rate capability and cycling stability. In this study, we report the preparation of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires that have porous structures with different contents of spinel phase via a co-precipitation method followed by carefully controlled calcination steps. Structural characterizations verify that the as-prepared nanowires are composed of interconnected nano-sized subunits with porous structures, and spinel phases are embedded inside the layered structure. The electrochemical measurements show that the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires bearing moderate content of spinel phase exhibit a high capacity of 291 mAh g−1 at 0.1 C and excellent capacity retention of 91.8% after 200 cycles at 1 C. The results also demonstrate that electrochemical performance of the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires is influenced by the content of spinel phase which can be readily tuned by changing the heating rate in the calcination step. The combination of one-dimension porous structures and built-in spinel domains in Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires improves the electrolyte contact and Li+ diffusion, and restrains structural degeneration. Graphical abstract Image 1 Highlights • Li-rich layered oxide Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 nanowires are synthesized. • The nanowires possess both 1D porous structure and built-in spinel domains. • The appropriate content of spinel phase can enhance the electrochemical properties. • The nanowires have excellent capacity retention of 91.9% after 200 cycles at 1 C. [ABSTRACT FROM AUTHOR]

The widespread application of Li-rich cathode material is restricted due to capacity attenuation and poor rate capability caused by crystal structure transformation and irreversible lattice oxygen escape during cycling. The Fe3+-doped effects on lattice structures and electrochemical properties of Li 1.2 Ni 0.26−x Mn 0.54 Fe x O 2 (x = 0, 0.03, 0.05 and 0.08) cathode materials fabricated by a sol-gel method are systematically studied in this paper. Doped materials exhibit good electrochemical performance such as high discharge specific capacity and capacity retention at high current density rates. Li 1.2 Ni 0.21 Mn 0.54 Fe 0.05 O 2 can supply a specific capacity of 190.7 mAh g−1 with 73.6 % capacity retention after 100th cycle at 2 C, and rate capacities of 230.6, 208.5, 193.1, 172.1 and 105.6 mAh g−1 at 0.1, 0.5, 1, 2 and 5 C, respectively. It is attributed to the enhanced structural stability, enlarged Li layer spacing, intensive interaction between transition metals and oxygen, less manganese disproportionation and oxygen release and increased Li+ diffusion coefficient by Fe3+ doping. • Moderate Fe3+ doping maintains well layered structure and phase stability. • Fe3+ doping enhances the performance as cycle stability and rate capability. • Strong Fe-O and oxygen vacancy inhibit the loss of lattice oxygen and active mass. • Fe3+ doping enlarges Li layer spacing and improves the Li+ diffusion coefficient. [ABSTRACT FROM AUTHOR]

Layered oxides represent a prominent class of cathodes employed in lithium-ion batteries. The structural degradation of layered cathodes causes capacity decay during cycling, which is generally induced by anisotropic lattice strain in the bulk of cathode particle and oxygen release at the surface. However, particularly in lithium-rich layered oxides (LLOs) that undergo intense oxygen redox reactions, the challenge of simultaneously addressing bulk and surface issues through a singular modification technique remains arduous. Here a thin (1-nm) and coherent spinel-like phase is constructed on the surface of LLOs particle to suppress bulk strain and surface O 2 release by just adjusting the amount of lithium source during synthesis. The spinel-like phase hinders the surface O 2 release by accommodating O 2 inside the surface layer, while the trapped O 2 in the bulk impedes strain evolution by ≈70% at high voltages compared with unmodified LLOs. Consequently, the enhanced structural stability leads to an improved capacity retention of 97.6% and a high Coulombic efficiency of ≈99.5% after 100 cycles at 0.1°C. These findings provide profound mechanistic insights into the functioning of surface structure and offer guidance for synthesizing high-capacity cathodes with superior cyclability., (© 2023 Wiley-VCH GmbH.)

The effect of the Nb5+ substitution with a charge-compensated strategy in lithium-rich layered oxides (LLOs) Li1.2Ni0.13+xCo0.13-xMn0.54-xNbxO2 (x = 0, 0.01, 0.02, and 0.03) has been investigated systematically. A hydroxide co-precipitation method followed by a high-temperature solid-state reaction is adopted in the synthesis process. Structural characterization confirms that the low dose substituting of Nb5+ in the layered structures forms a solid solution, and the samples show low cation mixing and enlarged Li+-diffusing channels, which imply favorable high-rate capability. The initial charge/discharge measurements suggest that the oxygen loss from the network during the delithiation process has been suppressed by the substitution of Nb5+ due to the formation of robust Nb-O bonds and a decrease in TM-O (TMs are transition metals) covalence. Moreover, these Nb-O bonds contribute to the stabilization of the crystalline framework, resulting in an excellent cycle stability with a mitigated voltage decay. [ABSTRACT FROM AUTHOR]

Abstract: Lithium‐rich layered oxides have attracted much attention for the high energy density, but they still suffer from cycling degradation and sluggish kinetic capability. In the present study, a novel modification of Li1.143Mn0.544Ni0.136Co0.136O2 sphere cathode materials by a hierarchical surface configuration is proposed, which integrates advantages of dual oxide layers of both amorphous and nanocrystalline Al2O3, as well as an inner spinel membrane. Mainly promoted by an ultrafast heterogeneous nucleation of Al(NO)3 nanoseeds caused by huge solubility differences, it only takes several minutes for pretreatment. After common annealing at low temperature, the obtained material is capable to deliver a high discharge capacity of 296.3 mAh g−1 with initial Coulombic efficiency of 92.9% at 0.1 C rate, and maintain stable cycling at both 0.2 and 0.5 C rates. Besides, rate performances are also enhanced as a result of the superior interface gained after surface modification, which produces reduced polarization during cycling. Through comprehensive analyses, improved surface property and stability are confirmed as the key to these enhancements. This strategy is anticipated to inspire new modification designs in future high energy density cathode materials. [ABSTRACT FROM AUTHOR]

Non-eutectic-salt route increases the grain densification and regulates the distribution of Li 2 MnO 3 -like domain of Li-rich layered oxides to acquire Li-ion batteries with high volumetric energy density. [Display omitted] • Non-eutectic salt balances grain growth and grain densification during sintering. • Non-eutectic salt regulates the distribution of Li 2 MnO 3 -like domain during sintering. • Grain densification and particle size distribution have great impact on compaction density. • Electrochemical properties are strongly dependent on the distribution of Li 2 MnO 3 -like domain. • Increasing volumetric energy density without compromising capacity is essential. When a weak mechanical strength of particles on cathode materials occurs, the prepared electrode fails to achieve a high compaction density with undegraded performances, which causes a low volumetric energy density in batteries. Herein, we propose a LiOH-Li 2 CO 3 non-eutectic-salt reaction route to achieve the particles with high densification and superior mechanical stability in Li-rich layered oxides. Temperature-dependent in situ synchrotron X-ray diffraction and advanced scanning/transmission electron microscopy help reveal the process of the structural and morphological rearrangement on this non-eutectic-salt reaction. In the non-eutectic-salt system, the pinning effect caused by the minority second-phase particles can restrict an excessive particle growth and increase a grain densification to improve the mechanical properties of the particles. In contrast to conventional reaction route, the compaction density of the as-fabricated electrode can reach 2.8 g cm−3 with very few particles cracking. Consequently, the target material delivers an initial discharge capacity of 273 mAh g-1 and the columbic efficiency over 90%, as well as a capacity retention of 87.2% after 150 cycles at C/2. A 2.1 Ah multilayer pouch cell with graphite anode shows a capacity retention of 78.6% with current of 760 mA after 300 cycles. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides, one of the most promising cathodes for high energy Li-ion batteries, commonly undergo some issues such as poor rate performance, low Coulombic efficiency, voltage degradation and so on. In this work, Li 1.18 Mn 0.56 Ni 0.13 Co 0.13 O 2 cathodes with excellent rate capability and cycling stability are prepared by a new molten-salt method using KCl and NaCl as complex flux. The electrochemical tests show that these cathodes can deliver an initial discharge specific capacity of 224.3 mA h g −1 at 300 mA g −1 . Meanwhile, the capacity retention ratio remains 92.1% after 100 cycles. The outstanding electrochemical performance is mainly attributed to the uniform distribution of TM-elements in Li 1.18 Mn 0.56 Ni 0.13 Co 0.13 O 2 cathodes, which can promote the electrochemical activation of Li 2 MnO 3 -like component. Especially, it is found that the uniformity of TM elements in Li-rich cathodes can be improved by choosing molten-salt method as the synthetic strategy. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide is one of the most promising cathode materials for high-energy-density Li-ion batteries (LIBs). The composition, structure and morphology of precursors have significant influence on the electrochemical performance of the final cathode material. The capacity and initial coulombic efficiency of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 can be simultaneously improved by sintering a nanoplate precursor with Li 2 CO 3 in our previous work. Herein, the morphology and the formation mechanism of such nanoplate are investigated through a designed orthogonal tests. The optimal concentration of transition metal ions, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and polyvinyl pyrrolidone (PVP) are 0.1, 0.031 and 0.004 g mL −1 , respectively. The as-prepared Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 from optimal nanoplate demonstrate an improved discharge capacity (323.8 mAh g −1 at 20 mA g −1 ), initial coulombic efficiency (81.3%), and rate capability (195.8 mAh g −1 at 3C). This new precursor architecture opens a promising avenue for the development of high-performances cathode materials of LIBs. [ABSTRACT FROM AUTHOR]

Lithium-rich manganese-based layered oxides (LRM) have garnered considerable attention as cathode materials due to their superior performance. However, the inherent structural degradation and obstruction of ion transport during cycling lead to capacity and voltage decay, impeding their practical applications. Herein, an Sb-doped LRM material with local spinel phase is reported, which has good compatibility with the layered structure and provides 3D Li + diffusion channels to accelerate Li + transport. Additionally, the strong Sb-O bond enhances the stability of the layered structure. Differential electrochemical mass spectrometry indicates that highly electronegative Sb doping effectively suppresses the release of oxygen in the crystal structure and mitigates successive electrolyte decomposition, thereby reducing structural degradation of the material. As a result of this dual-functional design, the 0.5 Sb-doped material with local spinel phases exhibits favorable cycling stability, retaining 81.7% capacity after 300 cycles at 1C, and an average discharge voltage of 1.87 mV per cycle, which is far superior to untreated material with retention values of 28.8% and 3.43 mV, respectively. This study systematically introduces Sb doping and regulates local spinel phases to facilitate ion transport and alleviate structural degradation of LRM, thereby suppressing capacity and voltage fading, and improving the electrochemical performance of batteries., (© 2023 Wiley-VCH GmbH.)

A self-compacting engineering to obtain Li 1.15 Mn 0.56 Ni 0.16 Co 0.08 O 2 materials with high compactness and outstanding electrochemical profile. [Display omitted] • The self-compacting engineering improves the compactness of the material and stabilizes the overall structure. • The co-doping of cation (Mg) and anion (Cl) inhibits the transition from lamellar to spinel phase. • The improved cathode shows an outstanding cycling stability (80.9 % after 300 cycles) and relieved voltage decay (0.5416 V after 300 cycles). Lithium-rich layered oxides (LLOs) are emerging as powerful competitors for Li-ion battery materials with high reversible capacity (≈ 300 mAh/g) and high energy density. Nevertheless, these oxides are prone to irreversible removal of oxygen and Li from the lattice during cycling, which in turn leads to notable capacity and voltage decay. Herein, we propose a self-compacting engineering to improve the compactness and electrochemical performance of LLOs materials. The results of particle cross-section characterization show that the particle interior of the modified LLOs is more compact than the raw LLOs. Electrochemical testing results indicate that the designed LLOs cathode exhibits discharge-specific capacities of 296 mAh/g at 0.1C as well as 230 mAh/g at 1C with 80.9 % capacity retentions after 300 cycles. Besides, effective suppression is achieved especially at 200 mA g−1 with a voltage decay of 0.0018 V/cycle. The increased structural density can inhibit the entry of electrolyte into the interior of the particles and ease the collapse of the internal structure, and the co-doping of cation (Mg) and anion (Cl) inhibits the transition from lamellar to spinel phase, which significantly improves the electrochemical performance of LLOs. The self-compacting engineering paves a broad path in manipulating structural stability to enhance LLOs performance for high-energy LIBs. [ABSTRACT FROM AUTHOR]