Next-generation Li-ion Batteries Research Articles

Reversible Configurations of 3-Coordinate and 4-Coordinate Boron Stabilize Ultrahigh-Ni Cathodes with Superior Cycling Stability for Practical Li-Ion Batteries.

Ultrahigh-Ni layered oxide cathodes are the leading candidate for next-generation high-energy Li-ion batteries owing to their cost-effectiveness and ultrahigh capacity. However, the increased Ni content causes larger volume variations and worse lattice oxygen stability during cycling, resulting in capacity attenuation and kinetics hysteresis. Herein, a Li2SiO3-coated Li(Ni0.95Co0.04Mn0.01)0.99B0.01O2 ultrahigh-Ni cathode that well-addresses all the above issues, which is also the first time to realize the real doping of B ions is demonstrated. The as-obtained cathode delivers a reversible capacity of up to 237.4 mAh g-1 (924 Wh kg-1 cathode) and a superior capacity retention of 84.2% after 500 cycles at 1C in pouch-type full-cells. Advanced characterizations and calculations verify that the boron-doping is existed in terms of 3-coordinate and 4-coordinate configurations and their high electrochemical reversibility during de-/lithiation, which greatly stabilizes oxygen anions and impedes Ni-ion migration to Li layer. Furthermore, the B-doping engineers the primary particle microstructure for better relaxing the lattice strain and accelerating Li-ion diffusion. This work advances the energy density of cathode materials into the domain of above 900 Wh kg-1, and the concept will inspire more intensive study on ultrahigh-Ni cathodes.

Mitigating the Kinetic Hysteresis of Co-Free Ni-Rich Cathodes via Gradient Penetration of Nonmagnetic Silicon.

Co-free Ni-rich layered oxides are considered a promising cathode material for next-generation Li-ion batteries due to their cost-effectiveness and high capacity. However, they still suffer from the practical challenges of low discharge capacity and poor rate capability due to the hysteresis of Li-ion diffusion kinetics. Herein, based on the regulation of the lattice magnetic frustration, the Li/Ni intermixing defects as the primary origin of kinetic hysteresis are radically addressed via the doping of the nonmagnetic Si element. Meanwhile, by adopting gradient penetration doping, a robust Si-O surface structure with reversible lattice oxygen evolution and low lattice strain is constructed on Co-free Ni-rich cathodes to suppress the formation of surface dense barrier layer. With the remarkably enhanced Li-ion diffusion kinetics in atomic and electrode particle scales, the as-obtained cathodes (LiNixMn1-xSi0.01O2, 0.6≤x≤0.9) achieve superior performance in discharge capacity, rate capability, and durability. This work highlights the coupling effect of magnetic structure and interfacial chemicals on Li-ion transport properties, and the concept will inspire more researchers to conduct an intensive study.

Li2FeCl4 as a Cost-Effective and Durable Cathode for Solid-State Li-Ion Batteries.

Low-cost cathode materials with high energy density and good rate performance are critical for the development of next-generation solid-state Li-ion batteries (SSLIBs). Here, we report Li2FeCl4 as a cathode material for SSLIBs with highly reversible Li intercalation and deintercalation, a high operation voltage of 3.7 V vs Li+/Li, good rate capability, and good cycling stability with an 86% capacity retention after 6000 cycles. Operando synchrotron XRD reveals that the phase evolution of Li2FeCl4 during charge-discharge cycling involves both solid-solution and two-phase reactions, which maintains a very stable framework during Li insertion and extraction.

ZnS Nanoseeds Sealed in N, P, S Co-Doped Carbon Hollow Rhombic Dodecahedra as a Superlithiophilic Host for Dendrite-Free Lithium Metal Anodes.

Lithium (Li) metal is considered ahopeful anode for next-generation Li-ion batteries thanks to its ultra-high theoretical specific capacity, extra-low theoretical density, and low negative potential. However, the uncontrolled growth of Li dendrites and volume fluctuation during plating/stripping processes severely hamper its commercial application. Herein, ZnS seeds sealed in N, P, S co-doped carbon hollow rhombic dodecahedra (ZnS@NPS-C HRD) is fabricated as a superlithiophilic host for Li metal anodes (LMAs) to solve the above problems. In addition, the Li nucleation and deposition mechanism on ZnS@NPS-C HRD is investigated by in situ optical microscopy, ex-situ X-ray diffraction, scanning electron microscopy, and theoretical calculations. Owing to the synergistic strategy of ZnS seeds-inducing nucleation and Li-limited growth, the as-prepared composite exhibits stability for 300 cycles in asymmetric cells and a long lifespan over 1100h in symmetric cells. Moreover, the ZnS@NPS-C HRD@Li|LiFePO4 full cell demonstrates a reversible capacity of 100.91mAhg-1 after 400 cycles at 1C.

One-step surface-to-bulk modification of single-crystalline Ni-rich Co-poor cathodes for high-rate and long-life Li-ion batteries at high-voltage operations

Single-crystalline Ni-rich Co-poor cathodes operating at high-voltage are attractive owing to their higher energy density for meeting the requirements of next-generation Li-ion batteries, yet they usually suffer from sluggish Li-ion diffusion kinetics and serious Li/Ni disordering. Herein, an in-situ co-precipitation strategy is implemented to achieve the novel In-doped and Li3InO3 coated single-crystalline LiNi0.90Co0.05Mn0.05O2 cathodes with a highly ordered layered structure. The In-doping facilitates grain growth by decreasing the surface energy of crystal faces, reducing the synthesis temperature by about 20 °C, which thus drastically suppresses Li/Ni disordering and lattice oxygen loss. Furthermore, the pillar effect of In-ion doping and the in-situ formation of the ultrafast Li-ion conductive Li3InO3 coating synergistically enhance the Li-ion diffusion kinetics. These merits enable the as-obtained Ni-rich Co-poor cathodes with a high reversible capacity of 229.4 mAh g−1 at 0.1C and 124.6 mAh g−1 at 7C. In a pouch-type full cell, 93.9 % of the initial capacity is still maintained after 500 cycles at 1C within 2.7–4.5 V. This finding opens up a new path for improving the rate performance and cycle life of single-crystalline Ni-rich cathodes for high-voltage Li-ion batteries.

Achieving ultra-low voltage fading in Co-free Li-rich layered oxides via effortless surface defect engineering

Cobalt (Co)-free lithium (Li)-rich layered oxides (LLOs) have emerged as promising cathode materials for the next generation of Li-ion batteries, attributed to their competitive market positioning and high energy density. Nevertheless, challenges arise from surface oxygen loss due to irreversible anionic redox reactions, leading to severe voltage and capacity decay that hinder the large-scale adoption of LLOs. Herein, we present an innovative, facile, and environmentally friendly hydrothermal approach to induce surface reconstruction of Li1.2Mn0.6Ni0.2O2 material. A multifaceted combination involving the spinel phase, oxygen vacancies, and reduced manganese is orchestrated to alleviate the irreversible oxygen redox and impressively enhance Li-ion diffusion. The modified sample, owing to this surface transition, demonstrates low-strain and low-distortion properties along with a substantial improvement in structural stability, supported by both experimental validations and theoretical studies. As a result, the engineered sample exhibits exceptional capacity retention of 97.12% after 150 cycles at 1C, with an ultra-low voltage decay (0.91 mV cycle−1). Additionally, noteworthy enhancements in initial coulombic efficiency and rate performance are also observed. This straightforward surface defect engineering method offers a pathway to developing “low-strain” LLOs with superior electrochemical performance, thereby laying a solid foundation for future commercial applications.

A Microstructure Resolved Multi-Material Model for Silico-Graphite Composite Electrode

Silicon (Si) has been considered as the most promising anode material for next-generation high-capacity Li-ion batteries due to its very high theoretical specific capacity. However, the large deformation associated with (de)lithiation and its detrimental consequences like pulverization, loss of electrical contact, and subsequent capacity loss, have long been a roadblock in deploying high-capacity electrodes. Grafting small amounts of Si with graphite has been proven to utilize the higher capacity of silicon and the stability of graphite. The intricacies of interactions between the two active materials and their effect on the overall performance of the composite electrode are still not well known. Here, we present a novel fully coupled multiphysics electrochemical-mechanical model based on 3D microstructure extracted from X-ray tomography scans of Si-C composite electrode. The theoretical framework integrates the large deformation and viscoplastic response of Si, and the two-way coupling between diffusion and interfacial reactions with mechanical stress. The resolution of the pore phase from the silicon and graphite phases allows for the simulation of the Li+ ion kinetics in the composite electrode and influence of the microstructure. The model is employed to study the phenomena of preferential lithiation, crosstalk between active materials, partial utilization due to mechanical influences, and develop strategies to maximize the specific capacity. Lastly, we also explore the potential and avoidance of mechanical damage within active materials and interfacial delamination. The first-of-its-kind 3D microstructure resolved, multi-material model presents a novel tool to simulate the performance of Si-C composite electrode and decode the depth of interactions between the active materials.

Multi-Doping Exploration of (Sb, Bi and Ba) by First Principles on Ordered Zn–Si–P Compounds as High-Performance Anodes for Next-Generation Li-Ion Batteries

Chalcopyrite ZnSiP2 has emerged as a promising anode material for next generation Li-ion-based batteries due to its high theoretical capacity. First principles multiple-dopant effect computations were made on the structural, electronic, magnetic, and thermodynamic responses for chalcopyrite ZnSiP2(1−x)Sbx, ZnSiP2(1−x)Bix, Zn(1−x)BaxSiP2, and Zn1−xBaxSiP2(1−x)Sbx, using both the norm conserving, ultra-soft pseudopotentials with generalized gradient approximation (GGA+PBE) and the main frame of density functional theory. Lattice coefficient volume, bulk modulus, formation energy, and total energy of host materials were computed and compared with experimental and theoretical results. Energy band gap for the pure chalcopyrite ZnSiP2 system (1.4 eV) matches previous data and validates the accuracy of current calculations as doping concentration (x = 0.6, 0.9, and 0.12) of (Sb, Bi, and Ba) at Zn and P sites increases. The corresponding band gap decreases, resulting in greater enhancement in electronic conductivity. Finally, the phonon dispersion relation, phonon density of states, vibration frequencies of phonon, Gibbs free energy, enthalpy, entropy effect, and Debye temperature (θ D) were estimated to confirm the thermodynamic stability of both pure and doped systems. These investigations are predicted to contribute a deeper sympathy of the doping effects on ZnSiP2, facilitating further advancements in anode materials design for Li-ion batteries.

Lithiophilic Multichannel Layer to Simultaneously Control the Li-Ion Flux and Li Nucleation for Stable Lithium Metal Batteries.

Although the Li metal has been gaining attention as a promising anode material for the next-generation high-energy-density rechargeable batteries owing to its high theoretical specific capacity (3860 mAh g-1), its practical use remains challenging owing to inherent issues related to Li nucleation and growth. This paper reports the fabrication of a lithiophilic multichannel layer (LML) that enables the simultaneous control of Li nucleation and growth in Li-metal batteries. The LML, composed of lithiophilic ceramic composite nanoparticles (Ag-plated Al2O3 particles), is fabricated using the electroless plating method. This LML provides numerous channels for a uniform Li-ion diffusion on a nonwoven separator. Furthermore, the lithiophilic Ag on the Li metal anode surface facing the LML induces a low overpotential during Li nucleation, resulting in a dense Li deposition. The LML enables the LiNi0.8Co0.1Mn0.1O2|| Li cells to maintain a capacity higher than 75% after 100 cycles, even at high charge/discharge rates of 5.0 C at a cutoff voltage of 4.4 V, and achieve an ultrahigh energy density of 1164 Wh kg-1. These results demonstrate that the LML is a promising solution enabling the application of Li metal as an anode material in the next-generation Li-ion batteries.

Densification of Alloying Anodes for High Energy Lithium-Ion Batteries: Critical Perspective on Inter- Versus Intra-Particle Porosity.

High Li-storage-capacity particles such as alloying-based anodes (Si, Sn, Ge, etc.) are core components for next-generation Li-ion batteries (LIBs) but are crippled by their intrinsic volume expansion issues. While pore pre-plantation represents a mainstream solution, seldom do this strategy fully satisfy the requirements in practical LIBs. One prominent issue is that porous particles reduce electrode density and negate volumetric performance (WhL-1) despite aggressive electrode densification strategies. Moreover, the additional liquid electrolyte dosage resulting from porosity increase is rarely noticed, which has a significant negative impact on cell gravimetric energy density (Whkg-1). Here, the concept of judicious porosity control is introduced to recalibrate existing particle design principles in order to concurrently boost gravimetric and volumetric performance, while also maintaining the battery's cycle life. The critical is emphasized but often neglected role that intraparticle pores play in dictating battery performance, and also highlight the superiority of closed pores over the open pores that are more commonly referred to in the literature. While the analysis and case studies focus on silicon-carbon composites, the overall conclusions apply to the broad class of alloying anode chemistries.

Structural modeling of high-entropy oxides battery anodes using x-ray absorption spectroscopy

High-entropy oxides (HEOs) are single phase solid solutions where five or more metals share the same sublattice, giving rise to unexpected features in various fields of applications. Recently, HEOs have emerged as an alternative conversion electrode anode material for next-generation Li-ion batteries, where the combination of several different elements in a single solid solution can synergistically act to overcome some of its main drawbacks, improving performance. Due to their chemical complexity, x-ray absorption spectroscopy (XAS) emerges as an appropriate technique to study the electronic (x-ray absorption near edge structure, XANES) and local structure (extended x-ray absorption fine structure, EXAFS) of these compounds as a function of cycling. This work aims to highlight the capabilities of XAS as an element-specific probe to understand a material’s structure at the atomistic level through EXAFS modeling of (MgFeCoNiCuZn)O high-entropy system and how to extract valuable information about the bond distance, number of near neighbors, and local disorder, which are crucial to a full understanding of the electrochemical reaction mechanisms of such battery electrodes.

Enabling high capacity and reversible Li storage in indium(III) oxide anode surrounded by carbon nanotube matrix

In2O3 is one of the post-transition metal oxides that can be a potential anode material for the Li-ion batteries (LIBs) because of its high theoretical capacity (869 mAh g−1) and low operating voltage (0.8 V vs Li/Li+) compared to other metal oxides. However, they have rarely been used in practical applications because of typical challenges such as irreversible capacity, unstable cycling stability, and poor coulombic efficiency. In this study, carbon nanotubes (CNTs) were successfully combined with In2O3 nanoparticles (NPs) via a solvothermal process. The In2O3 NPs and CNTs were homogeneously mixed by controlling the CNT dispersion (functionalization and appropriate solvent) and mixing sequence (dissolving the In2O3 precursor in the CNT-dispersed solution followed by thermal annealing). In addition, an increase in the oxygen vacancies in the In2O3 NPs by controlling the thermal annealing conditions (In2O3/CNT_Ar) could enhance robust binding with CNTs, increase the number of Li-ion binding sites, and improve the electrical conductivity. Therefore, at an appropriate ratio of In2O3 and CNT (92:8, w/w), the In2O3/CNT_Ar demonstrated remarkable cycling performance (830 mAh g−1 at a current density of 200 mA g−1 after 100 cycles) and rate capability (65% retention at 5 A g−1 relative to 100 mA g−1), which outperformed most In2O3-based anodes previously studied. Therefore, In2O3/CNT_Ar is a promising anode material for use in next-generation LIBs.

Operando Building of a Superior Interface Hybrid Film Enables Chemomechanically Durable Co-Free Ni-Rich Cathodes.

The Co-free Ni-rich layered cathodes become pivotal to reduce cost and increase benefit toward next-generation Li-ion batteries yet raise a major challenge for their extremely fragile cathode-electrolyte interface (CEI) film. Herein, we report the in situ construction of the Si/B-enriched organic-inorganic hybrid CEI films on LiNi0.9Mn0.1O2 (NM91) with the assistance of tris(trimethylsilyl) borate (TMSB) additive. The hybrid film exhibits superior Young's modulus, mechanical strength, and ductility, which greatly dissipate the microstrain of Co-free Ni-rich cathodes under various states of charge with high structural integrity. Furthermore, the surface oxygen anions have been significantly stabilized by bonding with the Si and B ions of TMSB with high safety. These merits enable a durable Co-free Ni-rich layered cathode with 96.9% and 87.7% capacity retentions (versus 72.7% and 70.2% of NM91) at a high rate of 5C and a high-temperature of 55 °C after 100 cycles. In a pouch-type full cell, 88.8% of initial capacity is still maintained after cycling at 1C for 500 times, greatly expediting the development and application of Co-free Ni-rich layered cathodes.

Bi-Directional H-Bonding Modulated Soft/Hard Polyethylene Glycol-Polyaniline Coated Si-Anode for High-Performance Li-Ion Batteries.

Ultrahigh-capacity silicon (Si) anodes are essential for the escalating energy demands driven by the booming e-transportation and energy storage field. However, their practical applications are strictly hampered by their intrinsically low electroconductivity, sluggish Li-ion diffusion, and undesirably large volume change. Herein, a high-performance Si anode, comprised of a modulated soft/hard coating of polyethylene glycol (PEG) (as Li-ion conductor) and polyaniline (PANI) (as electron conductor) on the surface of Si nanoparticles (NPs) through H-bonding network, is introduced. In this design, the abundant ─OH groups of soft PEG allow it to uniformly cover Si NPs while the hard PANI binds to PEG through its ─N─H group, thus constructing a tight connectin between Si and PEG-PANI (PP). Consequently, the elastic PP allows Si@PP to accommodate the huge volume expansion while possessing fine electronic/ionic conductivity. Therefore, the Si@PP anode exhibits a high initial Coulombic efficiency of 90.5% and a stable capacity of 1871mAhg-1 after 100 cycles at 1Ag-1 with a retention of 85.7%. Additionally, the Si@PP anode also demonstrates a high areal capacity of 3.01mAhcm-2 after 100 cycles at 0.5Ag-1. This work reveals a scalable interface design of multi-layer multifunctional coatings for high-performance electrode materials in next-generation Li-ion batteries.

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

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

Lateral growth of Lithium dendrite enforced by 3D porous Core@Shell-Cu@Li3N protective layer toward Long-Life Lithium metal anode

Li metal is promising as the anode for next-generation Li-ion batteries; however, uncontrollable dendrite growth and severe side reactions between the Li metal and electrolyte greatly restrict its commercialization. Here, a 3D porous protective layer constructed by core@shell-Cu@Li3N particles is developed to solve the above issues. This protective layer is easily prepared just by one-step dip coating in Cu(NO3)2/N-methyl-2-pyrrolidone (NMP) solution. Due to rapid Li+ transport and good wettability of the protective layer, it effectively modulates Li+ flux and thus homogenizes Li deposition. More importantly, as confirmed by both the experimental results and phase-field simulations, the 3D porous protective layer enforces the Li dendrite to laterally grow to form an interconnected network, which causes that the subsequent Li deposition is constrained and filled in the inner space rather than savage growth. Therefore, both the symmetric battery and full cell constructed by the protected Li electrode displays much longer lifespan than the one with bare Li even in unstable liquid carbonate electrolyte. Also, this protective layer is demonstrated to be compatible with Li1+xAlxTi2−x (PO4)3 (LATP) solid-state electrolyte by suppressing the side reactions. This work paves a new and facile strategy for developing high-performance Li metal anode.

Structure and molecular interactions in 1‑ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ion pair conformers: abinitio DFT based study

Density functional theory (DFT) calculations with Grimme’s B97D functional including dispersion are employed to provide both structural and electronic insight into the multifold interactions occurring in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid [EMI][TFSI], which is currently being targeted for applications in next-generation Li-ion battery electrolytes. The geometric structure, interaction energy and natural bond orbital analysis of the ion-pair conformers of [EMI][TFSI] show differences from the conventional H-bonds. A total of six stable [EMI][TFSI] ion pair conformers were observed. Our results show that a doubly ionic H-bond exists between [EMI]+ and [TFSI]− ion pair conformers. The greater the number of multiple H-bond type interactions, the greater the absolute value of the interaction energy. Moreover, results from the NBO analysis show that, for [EMI][TFSI] ion pair conformers, charge transfer occurs mainly from the lone pairs of oxygen and nitrogen atom to the σ-type anti-bonding orbital of the C–H and π-type anti-bonding orbitals of N–C bonds. This was evident from the values of the stabilization energy E(2) associated with each electron delocalization from the donor to acceptor orbitals. There exist large numbers of multiple concomitant hydrogen bonds, but the values of the stabilization energy E(2) are generally small (E(2)n→\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ o$$\\end{document}σ* < 3 kcal/mol) for the individual H-bond interactions. The shorter the C–H···O and/or C–H···N bond is, the larger charge transfer, and the larger the stabilization energy E(2) associated with electron delocalization from donor to acceptor. Generally, the [EMI][TFSI] ion pair conformers tend to form multiple but bent H bonds, reducing the strength of the individual H bonds from a potential (linear) maximum.

Enabling High-Performance Layered Li-Rich Oxide Cathodes by Regulating the Formation of Integrated Cation-Disordered Domains.

Layered Li-rich oxide cathode materials are capable of offering high energy density due to their cumulative cationic and anionic redox mechanism during (de)lithiation process. However, the structural instability of the layered Li-rich oxide cathode materials, especially in the deeply delitiated state, results in severe capacity and voltage degradation. Considering the minimal isotropic structural evolution of disordered rock salt oxide cathode during cycling, cation-disordered nano-domains have been controllably introduced into layered Li-rich oxides by co-doping of d0-TM and alkali ions. Combining electrochemical and synchrotron-based advanced characterizations, the incorporation of the phase-compatible cation-disordered domains can not only hinder the oxygen framework collapse along the c axis of layered Li-rich cathode under high operation voltage but also promote the Mn and anionic activities as well as Li+ (de)intercalation kinetics, leading to remarkable improvement in rate capability and mitigation of capacity and voltage decay. With this unique layered/rocksalt intergrown structure, the intergrown cathode yields an ultrahigh capacity of 288.4mAhg-1 at 0.1C, and outstanding capacity retention of ≈90.0% with obviously suppressed voltage decay after 100 cycles at 0.5, 1, and 2C rate. This work provides a new direction toward advanced cathode materials for next-generation Li-ion batteries.

Enhancing reversible capacity and cycling stability of Li&lt;sub&gt;1.2&lt;/sub&gt;Ni&lt;sub&gt;0.13&lt;/sub&gt;Fe&lt;sub&gt;0.13&lt;/sub&gt;Mn&lt;sub&gt;0.54&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; by inducing low Li/Ni misalignment through Mo doping

Li-ion batteries (LIBs) are widely used in mobile devices and electric vehicles, but the traditional layered transition metal cathode material, LiTMO&lt;sub&gt;2 &lt;/sub&gt;(TM=Ni, Co, Mn, or Al), has a low energy density that cannot satisfy the demand of commercial applications. The Li-rich Mn-based layered oxides (LRLOs) are a strong competitor to the traditional layered cathode materials for their specific capacity of more than 200 mAh/g. Due to the high energy density and low cost, Li-rich Mn-based layered oxides (LRLO) have been a promising candidate cathode for next-generation Li-ion batteries. The anionic redox reaction (ARR) in LRLO destabilizes the lattice oxygen, leading to voltage degradation and capacity loss. Although iron-substituted cobalt-free Li-rich materials can achieve less voltage decay, they suffer severe cation disorder and poor kinetics. Here, we develop a simple and feasible high-valent ion doping strategy by doping Mo into Li&lt;sub&gt;1.2&lt;/sub&gt;Ni&lt;sub&gt;0.13&lt;/sub&gt;Fe&lt;sub&gt;0.13&lt;/sub&gt;Mn&lt;sub&gt;0.54&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;(LNFMO), which expands the Li layer spacing and provides a broader channel for Li&lt;sup&gt;+&lt;/sup&gt; transport, thereby improving the diffusion kinetics of Li&lt;sup&gt;+&lt;/sup&gt;, effectively suppressing the cation disorder, and further stabilizing the layered structure. As a result, the Mo-doped LRLO exhibits significantly enhanced electrochemical performance, with an initial reversible capacity of 209.48 mAh/g at 0.2 C, and the initial specific capacity increasing from 137.02 mAh/g to 165.15 mAh/g at 1 C. After 300 cycles, specific capacity remains 117.49 mAh/g for the Mo-doped cathode, and the voltage decay decreases from 2.09 mV/cycle to 1.66 mV/cycle. The Mo-doped LRLO is systematically characterized, and the mechanism of cycle stabilization is revealed, which provides an important reference for designing high performance Li-rich cathode.

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

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