Nickel-rich Layered Cathode Materials Research Articles

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.

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.

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.

In-situ cladding PEDOT:PSS on V-doped NCA cathodes for optimized interface and high electrochemical performance of Li-ion battery

The LiNi0.8Co0.15Al0.05O2 (NCA) nickel-rich layered cathode material is widely used for Li-ion batteries because of its excellent structural stability and high specific capacity. However, the Li/Ni mixing effect and the generation of interfacial secondary reactions in NCA cathode materials reduce the electrochemical properties of Li-ion batteries. Herein, we report a series of vanadium (V)-doped NCA cathode (VNCA) materials with different amounts of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) polymers in-situ coated on the surface using a liquid-phase method. The introduction of PEDOT:PSS coating not only improves the conductivity of NCA cathode materials but also protects the surface of cathode materials from cracking during the cycle. Electrochemical results show that the PEDOT:PSS (2 wt%) coating possesses high capacity retention rate (83.58%) after 200 cycles at 1 C, which is better than that of the sample without coating (66.7%). The PEDOT:PSS (2 wt%) coated cathode materials also display superior rate performance to VNCA at high magnification. This work provides new methods and theoretical guidance for the development of efficient ternary cathode materials for Li-ion batteries.

Surface Gradient Ni-Rich Cathode for Li-Ion Batteries.

Nickel-rich layered oxide cathode material LiNixCoyMnzO2 (NCM) has emerged as a promising candidate for next-generation lithium-ion batteries (LIBs). These cathode materials possess high theoretical specific capacity, fast electron/ion transfer rate, and high output voltage. However, their potential is impeded by interface instability, irreversible phase transition, and the resultant significant capacity loss, limiting their practical application in LIBs. In this work, a simple and scalable approach is proposed to prepare gradient cathode material (M-NCM) with excellent structural stability and rate performance. Taking advantage of the strong coordination of Ni2+ with ammonia and the reduction reaction of KMnO4, the elemental compositions of the Ni-rich cathode are reasonably adjusted. The resulted gradient compositional design plays a crucial role in stabilizing the crystal structure, which effectively mitigates Li/Ni mixing and suppresses unwanted surficial parasitic reactions. As a result, the M-NCM cathode maintains 98.6% capacity after 200 cycles, and a rapid charging ability of 107.5 mAh g-1 at 15 C. Furthermore, a 1.2 Ah pouch cell configurated with graphite anode demonstrates a lifespan of over 500 cycles with only 8% capacity loss. This work provides a simple and scalable approach for the in situ construction of gradient cathode materials via cooperative coordination and deposition reactions.

The Role of Zinc Triflate Additive for Improved Electrochemical Performance of Nickel-Rich Layered Oxide Lithium Battery Cathode via Suppression of Interfacial Parasitic Reactions

Nickel-rich layered oxide cathode materials with low cobalt content, such as LiNi0.90Mn0.05Co0.05O2 (NMC90), have the potential to enable cost-effective, high-energy-density lithium-metal batteries. However, NMC90 cathode materials are prone to severe parasitic reactions at higher voltages during prolonged cycling. The addition of small percentages of electrolyte additives to the neat commercial electrolyte can significantly enhance the overall electrochemical performance of lithium-metal batteries. This study investigates the effects of zinc triflate (Zn(Otf)2) as an electrolyte additive on the enhancement of the electrochemical performances of lithium-metal batteries comprising nickel-rich layered oxide cathode materials. X-ray photoelectron spectroscopy analysis revealed that Zn(Otf)2 decomposition leads to enhanced fluorination at the interfacial layers, which contributes to improved chemical stability. Utilizing operando electrochemical mass spectroscopy, we demonstrate that Zn(Otf)2 additives effectively suppress the electrolyte degradation, which is otherwise detrimental to electrochemical performance. Electrochemical studies show that the inclusion of only ∼1% Zn(Otf)2 as additive in neat commercial electrolyte enhances the electrochemical performance indicated by a 10% improvement in discharge capacity after 150 cycles. This study paves the way for researchers to develop novel fluorinated triflate based electrolyte additives aimed at enhancing the stabilization of interfaces for lithium ion, and potentially also Li-metal batteries.

In-situ electrochemical passivation for constructing high-voltage PEO-based solid-state lithium battery

Polyethylene oxide (PEO) is one of the promising substrates for polymer solid electrolyte. However, when coupled with high energy density nickel-rich layered cathode materials, PEO faces the risk of catalytic decomposition by delithium nickel-rich materials. In this work, the in-situ electrochemical passivation strategy is employed to obtain high voltage PEO-based solid-state lithium battery. Trace commercial liquid electrolyte was added on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM811) electrode, and liquid electrolyte is prior to PEO electrolyte to react with the cathode during charge/discharge process, leading to the formation of cathode-electrolyte interface (CEI) layer. The CEI layer avoids the direct contact between PEO and NCM811, thus effectively prevents PEO from being decomposed by NCM811 under high voltage. As a result, the optimized NCM811||PEO||Li battery displays enhanced electrochemical performance, especially cycling performance. This simple but effective strategy not only simplifies the manufacturing process, but also has instructional guidance for high-voltage PEO-based battery.

Enhancing performance and stability of LiNi0.8Co0.1Mn0.1O2 cathode via Na/Y dual doping for Lithium-Ion batteries

Nickel-rich layered oxide cathode materials face limitations in practical applications due to trade-offs between capacity and structural stability. As more Li+ is extracted during charging, the layered structure of nickel-rich materials becomes increasingly fragile. To address this, a double doping strategy with Na and Y is proposed in this study to enhance the strength of the layered structure. The research findings demonstrate that Na doping enlarges the spacing between Li layers in the crystal structure, while Y doping improves the reversibility of the H2-H3 phase transition but narrows the Li layer spacing in nickel-rich materials. Na and Y double doping, the advantages of Na in enlarging the Li layer, and Y in improving the H2-H3 phase transition can be harnessed simultaneously. This double doping strategy ensures that the laminar structure of the cathode material remains stable even when it is highly detached, effectively solving the trade-off between the capacity and structural stability of nickel-rich laminar cathode materials. The application in LiNi0.8Co0.1Mn0.1O2 shows that the capacity and cycle life of cathode materials can be significantly improved after Na/Y double doping. These findings open up opportunities for practical applications of nickel-rich cathode materials in lithium-ion batteries.

Chemical modification of nickel-rich layered cathode materials to improve battery life

Mechanical integrity issues of Ni-rich cathode materials are major bottlenecks for their commercial application, stemming from the abrupt anisotropic lattice contraction during H2 ↔ H3 phase transitions. Herein, zirconium is used to modify LiNi0.9Co0.05Mn0.05O2 to solve the mechanical integrity issues. The relationship between the mechanical integrity issues and electrochemical performance is systematically examined to gain insights into the Zr activity-governing mechanisms. Results find that the addition of zirconium not only improves the diffusion ability of lithium ions by providing a rapid channel for diffusion of lithium ions, but also enhances mechanical properties by inhibiting cation mixing. As a result, the optimal LiNi0.9Co0.05Mn0.05O2 achieves superiority capacity retention of 84.12 % after 200 cycles at 5C, higher than that of unmodified LiNi0.9Co0.05Mn0.05O2 74.32 %. This work deeply investigates the information on the bulk structure and interaction mechanism between substitution cations and Ni-rich layered oxides, which provides a new insight to design and construct of advanced high-capacity cathode materials.

Stabilizing LiNi0.8Co0.1Mn0.1O2 cathodes with a mixed ionic-electronic conducting Li0.34La0.55MnO3-x multifunctional coating formed via in-situ conversion of surface Li residual

In this work, we for the first time utilize the harmful surface Li residual on NCM811 to in-situ form a mixed Li+/electron conducting Li0.34La0.55MnO3-x (LLMO) coating. The formation of the (electro)chemically stable LLMO coating not only achieves effective surface cleaning, but also stabilizes the cathode surface against electrolyte attack, alleviating structure degradation and intergranular cracking. Equally importantly, the mixed conducting LLMO layer affords considerably high Li+ and electronic conductivities (2.35 ×10−5 S/cm and 1.86 ×10−3 S/cm respectively), accelerating the charge-transfer process at the interface. The in-situ LLMO-coated NCM811 exhibits notable improvements in both rate and cycling performance, featuring a capacity retention rate of 82.51% over 100 cycles at 1 C in stark contrast to 48.26% of the pristine NCM811. When combined with a dendrite-suppressed Li@Pb@carbon cloth composite Li metal anode in a full battery, a high capacity retention rate of 86.96% over 200 cycles at 1 C and a N/P ratio of 37.7 is achieved, significantly outperforming that with NCM811 (42.24%, 40.2). This study provides a novel and comprehensive solution to stabilize nickel-rich layered cathode materials for high-energy-density Li-metal batteries.

Enhancing humidity resistance of nickel-rich layered cathode materials by low water-soluble CaF2 coating.

A low water-solubility but hydrophilic coating of CaF2 is demonstrated to be effective in mitigating the susceptibility of nickel-rich cathodes to moisture and even water. The ability of the cathode to resist water erosion is not inherently linked to either hydrophobicity or hydrophilicity, but lies in robust chemical bonding within the protective layer exhibiting low water solubility.

Fast charge induced phase evolution and element contribution of nickel-rich layered cathode for lithium-ion batteries

In nickel-rich layered cathode materials, three transition metals (TM = Ni, Co and Mn) play critical roles in Li storage performance. However, rate-dependent phase evolution and elemental contribution of nickel-rich cathode materials are not well understood, but very important for further design and development of these cathodes in high-power applications. Here, the rate-dependent phase evolution and elemental contribution of LiNi0.5Mn0.3Co0.2O2 (NMC532) cathode are investigated thoroughly by using time-resolved synchrotron-based in situ X-ray diffraction and absorption techniques. The increase of Ni content in NMC532 has been found to be the main cause of the complex structural changes, resulting in distortion of TM-O6 octahedron and strong static vibration between TM and O coordination. It is revealed that the fast charge (10 and 30C) of NMC532 leads to intermediate Li-poor phases, shrinking of H2 phase region, and prolonged O1 phase. During high-rate charging, Co is oxidized easily in low voltage region, while Ni mainly dominates charge compensation in high voltage region. It is found that delithiation-induced local structure distortion transfers from Ni to Co sites in fast kinetic process. These findings provide in-depth understanding for the fast charge behavior of Ni-rich layered cathode materials, and help to guide further development of advanced high power lithium-ion batteries.

Three-Dimensional Octahedral Nanocrystals of Cu2O/CuF2 Grown on Porous Cu Foam Act as a Lithophilic Skeleton for Dendrite-Free Lithium Metal Anode.

Metallic-lithium (Li) anodes are highly sought-after for next-generation energy storage systems due to their high theoretical capacity and low electrochemical potential. However, the commercialization of Li anodes faces challenges, including uncontrolled dendrite growth and volume changes during cycling. To address these issues, we developed a novel three-dimensional (3D) copper current collector. Here, we propose a two-step method to fabricate Cu2O/CuF2 octahedral nanocrystals (ONCs) onto 3D Cu current collectors. The resulting Cu foam with distributed ONCs provides active electrochemical sites, promoting uniform Li nucleation and dendrite-free Li deposition. The stable Cu2O/CuF2 ONCs@CF metallic current collector serves as a reliable host for dendrite-free lithium metal anodes. Additionally, the highly porous copper foam with a preconstructed conductive framework of Cu2O/CuF2 ONCs@CF effectively reduces local current density, suppressing volume changes during Li stripping and plating. The symmetric cell using Cu2O/CuF2 ONCs@CF metallic current collector exhibits excellent stability, maintaining over 1600 h at 1 mA cm-2 and a highly stable Coulombic efficiency of 98% over 100 cycles at the same current density, outperforming Li@CuF metallic current collectors. Furthermore, in a full-cell configuration paired with nickel-rich layered oxide cathode materials (Li@Cu2O/CuF2 ONCs@CF//NMC-811), the proposed setup demonstrates exceptional rate performance and an extended cycle life. In conclusion, our work presents a promising strategy to address Li anode challenges and highlights the exceptional performance of the Cu2O/CuF2 ONCs@CF metallic current collector, offering potential for high-capacity and long-lasting lithium-based energy storage systems.

Engineering robust biopolymer-derived carbon growth of Ni-rich cathode materials for high-performance Li-ion batteries

Nickel-rich ternary layered oxide (NCM811) is one of the most promising electrode materials for next-generation lithium ion batteries, offering high reversibility, ecofriendly, and low cost. However, this type of cathode material also has low thermal stability, phase changes during charge-discharge, and safety concerns, requiring considerable improvement to be commercially viable. This study induced carbon growth on a modified nickel-rich layered oxide NCM811 cathode material as positive electrodes for Li ion batteries, and subsequently performed electrochemical, structural, and post-mortem characterization for the material. Specific capacity retention for the best case cathodes improved to 75 % after 100 cycles at 0.1C rate under atmospheric conditions compared with current standard NCM electrodes. Full cell fabricated using that best case electrodes achieved 220 mAh g−1 initial charge capacity, retaining 81 % charge capacity after 50 cycles. Initial coulombic efficiency and cycle stability for the prepared best case cathode material was enhanced by optimum carbon growth due to the reconstructed layer structure's capacity to inhibit side reactions at the interface and stabilize bulk structure over cycles.

Mo–F Co-Doping LiNi0.83Co0.11Mn0.06O2 Stabilizes the Structure and Induces Compact Primary Particle To Improve the Electrochemical Performance

The Li+/Ni2+ cation disorder, material pulverization, surface phase transition, and transition metal (TM) ion dissolution are important issues that plague nickel-rich layered oxide cathode materials. In this paper, doping LiNi0.83Co0.11Mn0.06O2 with Mo6+ cation and F– anion effectively alleviates the above problems. The Mo6+ reduces the cations mixing, and the strong electronegativity of F strengthens the bonding with transition metal ions to resist HF corrosion. Furthermore, compact primary particles with interfused and radially aligned morphology induced by Mo–F co-doping reduce stress damage during cycling. The enhancement of electrochemical performance by Mo–F co-doping is systematically researched in terms of structure, morphology, secondary spherical pulverization, structural phase transition, and dissolution of transition metal ions.

Degradation of Nickel-Rich layered oxides in ambient air and its inhibition by surface coating and doping

Nickel-rich layered cathode materials [LiNixCoyMn1-x-yO2 (x ≥ 0.6), NCM] have been considered as one of the most promising cathode materials for high energy lithium-ion batteries (LIBs) due to the low cost and high energy density. However, NCM can easily degrade in the air·H2O and CO2 will react with NCM to produce surface impurities mainly consisting of LiOH and Li2CO3. These impurity species have a negative impact on LIBs, such as slurry gelation and side reactions, which hinder the practical application of NCM materials. Here, we use ambient pressure X-ray photoelectron spectroscopy (APXPS) to monitor the NCM surface reactions in air and identify the degradation mechanism. Then, surface coating and surface doping are deployed on NCM by the combination of atomic layer deposition (ALD) and post-annealing. We prove that ZrO2 surface coating and Zr4+ surface doping can significantly inhibit the formation of LiOH and Li2CO3 on NCM surface in air through thermogravimetric analysis (TGA) and titration and hence eliminate the electrochemical performance degradation of the battery. This simple modification method is expected to be a potential solution to the problem of residual lithium in the large-scale production of nickel-rich layered cathode materials.

W Modification of Nickel-Rich Ternary Cathode Material for Efficient Lithium-Ion Batteries

As one of the fastest-growing cathode materials, Nickel-rich layered cathode material has caused much attention in the “next-generation” Li-ion batteries (LIBs) owning to the high specific energy, high operating potential and long cycling life. However, it still encounters a great of complications to realize the improvement of poor cycle stability and structural defects. In an effort to emphatically investigate the obvious advantages of eco-friendly and low-cost W doping cathode material on the crystalline morphology and electrochemical properties, LiNi0.65−xCo0.15Mn0.20WxO2 (x = 0.5%, 1.0%, 2.0%) were synthesized by hydroxide coprecipitation and calcination crystallization method. Especially, when the amount of W is 1.0% molar ratio, the initial discharge capacity reaches 216.55 mAh g−1 and achieves a capacity retention of 95.95% after 100 cycles with the operation voltage of 2.7–4.4 V at 1C. The reliable results show that the primary particle size via doping appropriate content of W become significantly smaller which can effectively consolidate the stability of the crystal cathode material and improve the recycling performance evidently. In addition, the element of W was detected in the lattice of the crystal particle, which bring about somewhat increase of lattice spacing and expands the Li+ diffusion channels during charge/discharge cycles. This work provides a potential application prospect by the strategy of W modification in the cathode materials of micron-sized particles for efficient lithium-ion batteries.

Atomic-level insights into the first cycle irreversible capacity loss of Ni-rich layered cathodes for Li-ion batteries

Our study identifies that the first cycle IRC loss is strongly related to the irreversibility of the Ni charge state, which limits the capacity and energy density.

Micro- and nano-structural design strategies towards polycrystalline nickel-rich layered cathode materials

The development of micro- & nano-structure engineering in recent years is reviewed. The synthesis methods and mechanisms of different microstructures are summarized, and the future development direction of microstructure modification is proposed.

Enhanced Structural Stability and Capacity Retention of Ni-Rich LiNi0.91Co0.06Mn0.03O2 Cathode Material By Dual Doping and Coating for Libs

Nickel-rich layered cathode material has been received a lot of attention due to their superior cycle-ability, high energy density and improved safety. However, there are some issues which are needed to be resolved to ensure the long term application. The hostile attack of electrolyte with the charged cathode electrode results in the growth of thick solid electrolyte interphase (SEI) at the expense of Li+ consumption and increase in interfacial resistance. In addition, de/intercalation of Li+ leads to the continuous contraction and expansion of lattice structure that leads to the crack formation in the active material particles during extended cycling.In this work, a facile technique has been adopted to resolve the mentioned problems. In this study, Li3BO3 has been coated on the NCM surface to protect the active material against the continuous attack of electrolyte and boron is doped to enhance the structural stability of LiNi0.91Co0.06Mn0.03O2 NCM cathode material. The samples were characterized by XPS, XRD, SEM and TEM and the electrochemical properties were measured by assembling the coin cells. The XRD results confirm the shifting of (003) diffraction peak towards low angle which validates the boron doping in the crystal structure. The presence of B1s is confirmed on the surface of modified NCM by XPS analysis. The FETEM images shows a uniform and distinct coating layer of 12 nm on the surface of 0.05 wt% coated NCM. The 0.05 wt% NCM samples offers the highest discharge capacity of 215.3 mAh g-1 at 0.1C and capacity retention of 81.6% at 0.5C (1C = 202 mA g-1) after 100 cycles. The reason behind enhanced cycling is the high bond dissociation energy of B−O (ΔHf298 = 402 kJ mol−1) than Ni–O (ΔHf298 = 391.6 kJ mol−1), Co–O (ΔHf298 = 368 kJ mol−1) and even Mn–O (ΔHf298 = 402 kJ mol−1). Even at 2C cycling, LBO-0.05 NCM sample demonstrated a capacity retention of 79.4% after 100 cycles while pristine shows only 67.3%. The modified samples displayed superior rate performance as compare to pristine NCM, especially at high current density. The cyclic voltammetry and EIS results are in-line with the cycling data. The presence of B3+ doping in host structure and Li3BO3 coating on the NCM surface results in the superior electrochemical performance of modified NCM.