Layered Cathode Materials Research Articles

Performance improvement strategies of boron-doped lithium-rich layered oxide cathode materials for wide temperature condition

Herein, the boron-doped Li-rich materials are prepared by rapid nucleation-assisted solvothermal and high-temperature method. In this work, the effects of boron doping on crystal structure and cycling performances of as-prepared materials were investigated. The material characterization results show that the introduction of B reduces the TM valence, enlarges the (003) space distance, and modulates the local crystal structure, which may change the electrochemical performance of as-prepared samples. Li1.2Ni0.24Co0.08Mn0.48B0.02O2 (LLNCMBO-2) showed an increase in discharge capacity of 36.5 mAh g−1 at 0.1 C compared to the pristine sample. The LLNCMBO-2 exhibit high capacity retention of 85.50 % after 200 cycles with a voltage decay of only 254.9 mV. Additionally, the results of wide temperature testing show that the electrochemical performance of boron-doped samples improved evidently.

In-situ TiO2/reduced graphene oxide double-coated LiNi0.5Co0.2Mn0.3O2 microspheres as high-performance Li-ion cathode materials

LiNi0.5Co0.2Mn0.3O2(NCM) layered materials have high energy density and large power density but also exhibit obvious capacity fading and voltage decay during the cycle. A rational surface modification design is reported in this work to address these problems. Herein, tetrabutyl titanate (TBOT) was decomposed into TiO2 by hydrolysis-condensation reaction and high-temperature calcination, thus a homogeneous coating was generated on the surface of NCM. The coating layer of TiO2 stabilizes the crystal structure. Furthermore, rGO and reduced metal (Ni, Co, Ti) would be wrapped on the surface as a highly conductive second coating, which could provide a rapid electron conduction pathway. The dual surface-modified cathode shows an outstanding discharge capacity of 163.4 mAh g−1 at 0.2 C and 120 mAh g−1 at 10 C. This dual coating strategy provides valuable insights for further study on the modification mechanisms of other layered cathode materials.

Ca/Li Synergetic-Doped Na0.67Ni0.33Mn0.67O2 to Realize P2-O2 Phase Transition Suppression for High-Performance Sodium-Ion Batteries.

P2-type layered transition metal oxide Na0.67Ni0.33Mn0.67O2 is considered as a promising cathode for advanced sodium-ion batteries due to its high theoretical specific capacity. However, the P2-type cathode suffers severe P2-O2 phase transition during cycling process, resulting unsatisfactory cyclic stability and rate capability. Herein, a Ca/Li co-doped P2-type Na0.62Ca0.05Ni0.33Mn0.57Li0.10O2 (NCNMLO) cathode material was synthesized through a simple sol-gel method. With the synergistic effect of Ca-doping at Na sites and Li substitution at transition metal (TM) sites, the cathode achieves an excellent electrochemical performance due to the inhibited P2-O2 phase transition and improved ion diffusion with Na+/vacancy disordering arrangement. The NCNMLO cathode exhibits a good cyclic stability with 70.8% of capacity retention at 1 C after 200 cycles and excellent rate capability with 40.1 mAh g-1 at 20 C. The dual sites doping strategy provides an effective and simple approach for designing high-performance layered oxide cathode materials for sodium-ion batteries.

Surface Catalytic Repair for the Efficient Regeneration of Spent Layered Oxide Cathodes.

Direct recycling is considered to be the next-generation recycling technology for spent lithium-ion batteries due to its potential economic benefits and environmental friendliness. For the spent layered oxide cathode materials, an irreversible phase transition to a rock-salt structure near the particle surface impedes the reintercalation of lithium ions, thereby hindering the lithium compensation process from fully restoring composition defects and repairing failed structures. We introduced a transition-metal hydroxide precursor, utilizing its surface catalytic activity produced during annealing to convert the rock-salt structure into a layered structure that provides fast migration pathways for lithium ions. The material repair and synthesis processes share the same heating program, enabling the spent cathode and added precursor to undergo a topological transformation to form the targeted layered oxide. This regenerated material exhibits a performance superior to that of commercial cathodes and maintains 88.4% of its initial capacity after 1000 cycles in a 1.3 Ah pouch cell. Techno-economic analysis highlights the environmental and economic advantages of surface catalytic repair over pyrometallurgical and hydrometallurgical methods, indicating its potential for practical application.

F-doping effects on microstructure and electrochemical performance of cathode material Li1.2Mn0.54Ni0.13Co0.13O2

Lithium-rich manganese-based (Li-rich Mn-based) cathode materials possess high specific capacity, low self-discharge rate and steady working voltage, but cycle performance and rate performance need to be further improved. In this study, cathode materials Li1.2Mn0.54Ni0.13Co0.13O2-xFx (x = 0, 0.02, 0.05, 0.08) are synthesized by the co-precipitation method with the two-step calcination process. And the F-doping effects on the microstructure and the electrochemical performance are investigated in the cathode materials Li1.2Mn0.54Ni0.13Co0.13O2. The results indicate that among all the F-doped cathode materials, the crystal lattice parameters are increased, order degree and stability of the layered structure are improved. As for x = 0.05, cathode material Li1.2Mn0.54Ni0.13Co0.13O1.95F0.05 (LMO-F0.05) shows the best cycle performance and rate performance with its capacity retention rate 87.7% after 100 cycles at 0.2 C and discharge capacity 117 mAh g−1 at 5 C high power. It can be seen that F doping is a simple and crucial strategy to promote the Li ion diffusion and develop high performance layered cathode materials.

Durable high voltage solid-state sodium batteries with Pseudocapacitive P2 layered oxide cathode

Solid-state sodium batteries (SSBs) have attracted great interests due to their high energy density, good safety and low cost, but their performance including operation voltage, cycling stability and rate capability are far from satisfactory. In this study, a P2-Na0.68Li0.10Ni0.25Mn0.63Ca0.01Ti0.01O2 (NM-L10CT) layered cathode material were successfully fabricated, which possesses a high pseudocapacitance over 92 %, low volume strain of 0.8 %, high Na-ion diffusion coefficient and very good reversibility of anionic redox reaction. Moreover, room temperature solid-state sodium batteries with NM-L10CT and Na3Zr2Si2PO12 (NZSP) solid electrolyte are demonstrated, displaying much improved structural stability and cycling performance compared with that in liquid electrolyte batteries. The NM-L10CT/NZSP/Na SSBs exhibit very excellent electrochemical performance under high cut-off voltage, with high retention rates of 81.2 % after 500 cycles (2.0–4.2 V) and 74.2 % after 300 cycles (2.0–4.3 V), respectively. It has an outstanding rate performance with a high capacity of 115.4 mAh g-1 at 1 C and 74.5 mAh g-1 even at 10 C rate. This is due to the significantly reduced interface resistance and improved structural stability in solid state. This work demonstrates the successful application of high voltage layered cathode in SSBs and provides the insightful understanding of such material in liquid electrolyte and solid state battery.

Layered Oxide Cathode Materials for Sodium-Ion Batteries: A Mini-Review

Layered Oxide Cathode Materials for Sodium-Ion Batteries: A Mini-Review

Lithium-rich manganese-based layered oxide cathode materials for lithium-ion batteries modified by MoS2 coatings with two-dimensional graphene-like structures

Lithium-rich manganese-based layered oxide cathode materials (LRMCs) have some unique advantages such as high theoretical capacity (≥ 250 mAh g−1) and high energy density. Therefore, they are deemed as a kind of cathode material for lithium-ion batteries with an excellent prospect of application. However, the redox of oxygen anion is able to generate irreversible lattice oxygen loss, leading to irreversible loss of capacity, bringing about a sharp drop of working voltage, and seriously restricting the commercialization of LRMCs. In this paper, MoS2 coating with two-dimensional graphene-like structure was coated on the surface of LRMCs materials for improving the cycling stability and rate performance. The MoS2 coating can provide a two-dimensional diffusion channel for the migration of lithium-ions, which facilitates the fast release of lithium-ions during cycling process. The results show that the first discharge capacity, initial Coulomb efficiency and rate performance of LRMCs are improved. When the current density is 1 C, the first discharge specific capacity of LRMCs@MoS2 reaches 227.69 mAh g−1, and the capacity retention ratio is 84.98 % after 100 cycles. When the current density is 5 C, it can still provide a discharge specific capacity of 137.87 mAh g−1, demonstrating excellent electrochemical performance. This study comes up a simple and practical idea to realize the modification of cathode materials for high performance lithium-ion batteries.

Optimizing high-energy lithium-ion batteries: a review of single crystalline and polycrystalline nickel-rich layered cathode materials: performance, synthesis and modification

Layered Ni-rich Li [NixCoyMnz]O2 (NMC) and Li [NixCoyAlz]O2 (NCA) cathode materials have been used in the realm of extended-range electric vehicles, primarily because of their superior energy density, cost-effectiveness, and commendable rate capability. However, they face challenges such as structural instability, cation mixing, and surface degradation, which limit their practical application. This review comprehensively discusses the synthesis, modification, and performance optimization of nickel-rich cathodes, with a focus on single-crystal (SC) NMC cathodes. The unique properties and challenges of single-crystal nickel-rich cathodes are explored in comparison to polycrystalline (PC) cathodes, with a focus on performance-enhancing strategies such as doping and surface modification.

Facilitating superior electrochemical efficacy and ultra rapid kinetic in Co/Ni-free layered oxides for sodium-ion batteries with phosphate-growing layer fast ion conductors

Co/Ni-free layered oxides have garnered significant interest due to their environmental friendliness and facile synthesis methodologies, while facing major challenges of inferior cycling stability and rate capability. Addressing these drawbacks necessitates the enhancement of the surface properties of Co/Ni-free layered oxides. This work introduces a Co/Ni-free layered oxide, Na0.67Mn0.65Fe0.3Al0.05O2 (NMFA), which has been subjected to phosphate-based surface engineering. This targeted surface modification aims to augment the specific surface area and establish a protective layer on NMFA. Such improvements are critical for expanding the effective electrochemical reaction zone, broadening sodium ion diffusion pathways, curtailing the P2-OP4 phase transition, and reducing the activation energy for interfacial charge transfer. This multifaceted surface treatment epitomizes the ingenious design and realization of advanced Co/Ni-free layered oxide cathode materials through straightforward processing techniques. Notably, the NMFA subjected to 3%-AlPO4 surface modification demonstrated an initial discharge capacity of 189.1 mAh/g at 0.1C, maintaining its capacity after 500 cycles at 10C. Additionally, DFT calculations corroborate that such surface growth can bolster electrical conductivity, restrain oxygen liberation and foster sodium ion migration. This elucidates that the phosphate growth layer serves as the oxygen reservoir. Accordingly, this investigation propounds a promising avenue to circumvent the challenges confronting Co/Ni-free layered oxides, thus paving the way for the development of high-performance cathode materials.

A Novel 4-Fluorophenyl Isocyanate Additive Constructing Solid Cathodes-Electrolyte Interface for High-Performance Lithium-Ion Batteries.

Building a stable cathode-electrolyte interface (CEI) is crucial for achieving high-performance layered metal oxide cathode materials LiNixCoyMn1-x-yO2 (NCM). In this work, a novel 4-fluorobenzene isocyanate (4-FBC) electrolyte additive that contains isocyanate and benzene ring functional groups is proposed, which can form robust and homogeneous N-rich and benzene ring skeleton CEI film on the cathode surface, leading to significant improvement in the electrochemical performance of lithium-ion batteries. Taking LiNi0.5Co0.2Mn0.3O2 (NCM523) as an example, the NCM523/SiO@Graphite pouch full cells with electrolytes containing a mass fraction of 1% 4-FBC additives demonstrate improved capacity retention after 200 cycles, retaining capacity retention rates of 81.3%, which is much higher than that of 39.1% without additive. The improvement can be ascribed to the mitigation of electrolyte decomposition and inhibition of transition metal ions the dissolution from the cathode material due to the stable CEI film. Moreover, the electrochemical performance enhancement can also be achieved in high voltage and Ni-rich cathode materials, indicating the universality and effectiveness of this strategy for the practical applications of high energy density lithium-ion batteries.

Understanding the Carbon Additive/Sulfide Solid Electrolyte Interface in Nickel-Rich Cathode Composites and Prioritizing the Corresponding Interplay between the Electrical and Ionic Conductive Networks to Enhance All-Solid-State-Battery Rate Capability.

All-solid-state lithium batteries, including sulfide electrolytes and nickel-rich layered oxide cathode materials, promise safer electrochemical energy storage with high gravimetric and volumetric densities. However, the poor electrical conductivity of the active material results in the requirement for additional conducive additives, which tend to react negatively with the sulfide electrolyte. The fundamental scientific principle uncovered through this work is simple and suggests that the electrical network benefits associated with the introduction of short-length carbons will eventually be overpowered by the increase in bulk resistance associated with their instability in the sulfide electrolyte. However, applying just the right amount of short carbon fibres minimizes degradation of the sulfide solid electrolyte and maximizes the electron movement. Therefore, we propose the application of a low-weight-percent carbon nanotubes (CNTs) coating on the nickel-rich cathode LiNi0.8Co0.1Mn0.1O2 (NCM811) along with large-aspect-ratio carbon nanofibers (CNFs) as the primary conductive additive. When only 0.3 wt % CNTs was utilized with 4.7 wt % CNFs, an initial Coulombic efficiency of 83.55% at 0.05C and a notably excellent capacity retention of 90.1% over 50 cycles at 0.5C were achieved along with a low ionic resistance. This work helps to confirm the validity of applying short carbon pathways in sulfide-electrolyte-based cathode composites and proposes their combination with a larger primary carbon additive as a solution to the ongoing all-solid-state battery rate and instability issues.

K-Rich Spinel Interface of Air-Stable Layered Oxide Cathodes for Potassium-Ion Batteries.

Potassium-containing transition metal layered oxides (KxTmO2), although possessing high energy density and suitable operating voltage, suffer from severe hygroscopic properties due to their two dimensional (2D)layered structure. Their air sensitivity compromises structural stability during prolonged air exposure, therefore increasing the cost. The common sense for designing air-stable layered cathode materials is to avoid contact with H2Omolecules. In this study, it is surprisingly found that P3-type KxTmO2 forms an ultra-thin, potassium-rich spinel phase wrapping layer after simply water immersion, remarkedly reduces the reaction activity of the material's surface with air. Combined with Density Function Theory (DFT) calculations, this spinel phase is found to be able to effectively withstand air deterioration and preserving the crystal structure. Consequently, the water-treated material, when exposed to air, can largely maintain its good electrochemical performance, with capacity retention up to 99.15% compared to the fresh samples. Such an in situ surface phase transformation mechanism is also corroborated in other KxTmO2, underscoring its effectiveness in enhancing the air stability of P3-type layered oxides for K+ storage.

Review on layered oxide cathodes for sodium‐ion batteries: Degradation mechanisms, modification strategies, and applications

AbstractExploiting high‐capacity cathode materials with superior reliability is vital to advancing the commercialization of sodium‐ion batteries (SIBs). Layered oxides, known for their eco‐friendliness, adaptability, commercial viability, and significant recent advancements, are prominent cathode materials. However, electrochemical cycling over an extended period can trigger capacity fade, voltage hysteresis, structural instability, and adverse interface reactions which shorten the battery life and cause safety issues. Thus, it is essential to require an in‐depth understanding of degradation mechanisms of layered oxides. In this review, the crystal and electronic structures of layered oxides are revisited first, and a renewed understanding is also presented. Three critical degradation mechanisms are highlighted and deeply discussed for layered oxides, namely Jahn–Teller effect, phase transition, and surface decomposition, which are directly responsible for the inferior electrochemical performances. Furthermore, a comprehensive overview of recently reported modification strategies related to degradation mechanisms are proposed. Additionally, this review discusses challenges in practical application, primarily from a degradation mechanism standpoint. Finally, it outlines future research directions, offering perspectives to further develop superior layered cathode materials for SIBs, driving the industrialization of SIBs.

Effects of multi-element composition regulation on the structure and electrochemistry of P2-type layered cathode materials

P2-type Mn-based oxides are promising cathode materials for sodium-ion batteries due to their low cost and high capacity virtue. However, the irreversible phase transition and unstable anion redox at high operating voltages (∼4.2 V) will cause structural distortions, leading to slow sodium-ion diffusion kinetics and severe capacity degradation. Herein, a multi-elemental composition regulation strategy is proposed to enhance the structural stability of P2-type cathode by optimizing the structure and modulating the irreversible oxygen redox during high-voltage cycling. A series of multi-element cathodes Na0.67(Fe1/4Co1/4Ni1/4Ti1/4)1-xMnxO2 (x = 0.4,0.5,0.6,0.7,0.8,0.9) are designed and the effects of component modulation on their structure and electrochemical behavior are systematically investigated. Especially, the optimized Na0.67Fe0.05Co0.05Ni0.05Ti0.05Mn0.8O2 cathode maintains P2 phase during the initial charging/discharging between 1.5 V and 4.5 V, inhibits irreversible oxygen redox, and exhibits small lattice expansion. Impressively, the above optimized cathode exhibits superior cycling stability with capacity retention of nearly 90 % and reversible capacity of 130.1 mAhg−1 after 100 cycles at 1C rate. Furthermore, the optimized cathode also displays an excellent rate capability (capacity of 108.2 mAh g−1 at 5 C rate) due to the enhanced Na+ diffusion kinetics. This work provides new insight into developing high-stable Mn-based oxide cathodes operating at high voltage for sodium-ion batteries.

Development of electrode and electrolyte materials for solid-state batteries based on Li1.3Al0.3Ti1.7(PO4)3

The dependence of the electrochemical characteristics of a layered cathode material containing LiNi0.5Mn0.3Co0.2O2 on the method for applying a protective layer of nanoparticles of the lithium-conducting material Li1.3Al0.3Ti1.7(PO4)3 with a NASICON structure to its surface has been studied. The surface modification has been found to improve the capacity retention in prolonged charge/discharge cycling (up to 15%) and to allow fast charge/discharge processes. The possibility of using a composite electrolyte consisting of a porous ceramic matrix of aluminum-substituted lithium titanium phosphate Li1.3Al0.3Ti1.7(PO4)3 with a transition layer of liquid electrolyte LP-71 has been shown. The use of a thick composite solid electrolyte results in a slight reduction (∼5–7 mAh g−1) in initial capacity compared to laboratory cells with the widely used Celgard 2400 separator impregnated with liquid electrolyte. Laboratory cells assembled with a composite electrolyte showed higher stability during charge/discharge cycling: after 80 deep charge/discharge cycles, the capacity reduction was ∼12% for cells with a composite electrolyte, while for the reference cell it was ∼23%.

Constructing unique dual-functional double-hollow architecture for enhanced high-voltage structural stability of layered oxide cathode

Elevating the working voltage has proven to be an effective strategy for enhancing the energy density of ternary layered cathode materials. However, the accelerated failure of secondary particle structure during high-voltage cycling hinders their practical application. Although some attempts have been exerted to address this issue by designing particle arrangement, these secondary structure modifications only provide the limited help to the structural failure problem. Herein, we focus on the cause and characteristic of secondary particle cracks, investigate their formation principle and development rule, and delicately propose a unique double-hollow secondary structure. The two hollow regions create an environment that facilitates the release of internal strain and reduces stress at grain boundaries, thus ensuring the homogeneous stress distribution within the secondary particles. Thereby, the formation of intergranular crack is effectively mitigated. Additionally, the hollow regions act as barrier layers to impede the crack propagation. The dual functions of this double-hollow structure efficiently maintain the tight connection among these primary particles, greatly boosting the high-voltage cycling stability. The designed material with double-hollow architecture exhibits an obvious capacity retention increase from 67.8 % (conventional structure) to 84.4 % at 1 C within 3.0-4.5 V after 300 cycles. This work demonstrates that the double-hollow structure can effectively address the key issues of crack occurrence and development, providing a novel structural design concept for the exploration of high-voltage cathode materials with superior stability.

Improving high-voltage cycling and stabilizing the electrode-electrolyte interface of nickel-rich layered cathodes by magnesium doping

Next-generation lithium-ion batteries will rely on nickel-rich layered oxides as cathode materials, but these materials are associated with structural and voltage losses. Magnesium (Mg) doping helps improve the performance of the nickel-rich layered cathode material. The Mg-modified LiNi0·90Mn0·05Co0·05O2 (NMC-90) has been successfully synthesized through a co-precipitation technique followed by calcination at 850 °C. Modified NMC-90 exhibits better-organized layers and improved interfacial properties than pristine ones based on structural, chemical, and morphological studies. In a voltage range of 2.8–4.5 V, Mg (0.01 mol%)-doped NMC-90 (NMC-M1) composite cathode shows an excellent discharge capacity of 211.11 mAh/g, whereas pristine NMC-90 (NMC-M0) attains only 210.59 mAh/g at 0.1C with an initial coulombic efficiency of 89.5 % for NMC-M1 and 87.5 % for NMC-M0 cathode. The NMC-M1 cathode demonstrated an impressive enhancement in cyclability after 60 cycles compared to the NMC-M0 at 1C rate, in which the NMC-M1 cathode attains a high capacity retention of 80 % while the NMC-M0 cathode shows only 37 %. This study illustrates the importance of studying the effects of elemental doping on cell performance. It will drive the future development of cathode materials with high Ni and low Co content.

Origin of enhanced electrochemical performance in lithium-rich cathode materials via the fast ion conductor Li2O-B2O3-LiBr

Lithium-rich cathode materials have garnered significant attention in the energy sector due to their high specific capacity. However, severe capacity degradation impedes their large-scale application. The employment of fast ion conductors for coating has shown potential in improving their electrochemical performance, yet the structural and chemical mechanisms underlying this improvement remain unclear. In this study, we systematically analyze, through first-principles calculations, the mechanism by which Li2O-B2O3-LiBr (Hereafter referred to as LBB) coating enhances the electrochemical performance of the lithium-rich layered cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 (Hereafter referred to as OLO). Our calculations reveal that the LBB coating introduces a more negative valence charge (average −0.14 e) around the oxygen atoms surrounding transition metals, thereby strengthening metal-oxygen interactions. This interaction mitigates irreversible oxygen oxidation caused by anionic redox reactions under high voltages, reducing irreversible structural changes during battery operation. Furthermore, while the migration barrier for Li+ in OLO is 0.61 eV, the LBB coating acts as a rapid conduit during the Li+ deintercalation process, reducing the migration barrier to 0.32 eV and slightly lowering the internal migration barrier within OLO to 0.43 eV. Calculations of binding energies to electrolyte byproducts HF before and after coating (at −7.421 and −3.253 eV, respectively) demonstrate that the LBB coating effectively resists HF corrosion. Subsequent electrochemical performance studies corroborated these findings. The OLO cathode with a 2% LBB coating exhibited a discharge capacity of 157.12 mAh g−1 after 100 cycles, with a capacity retention rate of 80.38%, whereas the uncoated OLO displayed only 141.67 mAh g−1 and a 72.45% capacity retention. At a 2 C rate, with the 2 wt% LBB-coated sample maintaining a discharge capacity of 140.22 mAh g−1 compared to only 107.02 mAh g−1 for the uncoated OLO.

Regulating bond structure and local electronic state optimizes the cycling stability of layered sodium-ion cathode materials

Regulating bond structure and local electronic state optimizes the cycling stability of layered sodium-ion cathode materials