Ni-rich Oxide Research Articles

Solving the Residual Lithium Problem by Substoichiometric Synthesis of Layered Ni-Rich Oxide Cathodes

Solving the Residual Lithium Problem by Substoichiometric Synthesis of Layered Ni-Rich Oxide Cathodes

Oxidation behavior of an ultra-high strength and ductile Ni-enriched complex concentrated alloy

Recent research work revealed that Ni43.9Co22.4Fe8.8Al10.7Ti11.7B2.5 HEA is one of the ultra-high strength and ductile superlattice alloys. In this work, high-temperature oxidation behavior of the as-cast Ni43.9Co22.4Fe8.8Al10.7Ti11.7B2.5 alloy was investigated at 1000 ℃ up to 100 h. The oxidized samples were characterized using X-ray Diffractometer, Energy Dispersive Spectroscopy, and X-ray Photoelectron Spectroscopy. The results revealed that the initial microstructure of the alloy consists of face centered cubic (FCC) and L12 structures. High-temperature exposure resulted in the formation of Al2O3 and TiO2 scales during the initial hours of oxidation, which eventually spall-off after 25 h of exposure allowing further oxidation. The results showed that protective oxide layers such as Al2O3 and TiO2 were not present after 100 h of exposure. The external layer of the 100 h oxidized sample was composed of Fe, Co, and Ni-rich oxides which are known to have mere effective resistance against oxygen ingression. The alloy which has superior strength and ductility may be used for high temperature applications after attaining the thermally stable fine-grain microstructure by suitable thermomechanical processing / providing oxidation resistance coating / by doping with elements having superior oxidation resistance.

Role of grain-level chemo-mechanics in composite cathode degradation of solid-state lithium batteries

Solid-state Li-ion batteries, based on Ni-rich oxide cathodes and Li-metal anodes, can theoretically reach a high specific energy of 393 Wh kg−1 and hold promise for electrochemical storage. However, Li intercalation-induced dimensional changes can lead to crystal defect formation in these cathodes, and contact mechanics problems between cathode and solid electrolyte. Understanding the interplay between cathode microstructure, operating conditions, micromechanics of battery materials, and capacity decay remains a challenge. Here, we present a microstructure-sensitive chemo-mechanical model to study the impact of grain-level chemo-mechanics on the degradation of composite cathodes. We reveal that crystalline anisotropy, state-of-charge-dependent Li diffusion rates, and lattice dimension changes drive dislocation formation in cathodes and contact loss at the cathode/electrolyte interface. These dislocations induce large lattice strain and trigger oxygen loss and structural degradation preferentially near the surface area of cathode particles. Moreover, contact loss is caused by the micromechanics resulting from the crystalline anisotropy of cathodes and the mechanical properties of solid electrolytes, not just operating conditions. These findings highlight the significance of grain-level cathode microstructures in causing cracking, formation of crystal defects, and chemo-mechanical degradation of solid-state batteries.

Modifying Li-Rich Cathodes and Investigation into Fully Earth-Abundant Cathode Materials

The growing demand for electric vehicles and grid storage devices entails the search for materials to further enable these technologies. In this regard, the development of cost-effective, and energy-efficient lithium-ion battery cathodes is of the essence. In recent times, Ni-rich NMC oxides (LiNi x Mn y Co z O2, x+y+z = 1) have emerged as the latest and most advanced materials for use as Li-ion cathodes. However, increasing concerns over sustainability, supply chain issues, and cost-effectiveness of critical elements like Co and Ni have accelerated the search for earth-abundant, Mn and Fe-rich cathode materials.1 Lithium and manganese rich oxide materials (LMR), with general formula xLi2MnO3 • (1-x)LiMO2, can achieve higher energy densities compared to conventional NMC oxides, and thus represent attractive alternatives.2-3 Although issues like voltage fade and hysteresis are concerns with respect to practical application of LMR cathodes and have been well studied, the anomalous increase of area specific impedance (ASI) at low states of charge (SOC), has been comparatively overlooked. This presentation will discuss recent attempts to modify the low SOC ASI behavior of LMR materials by targeted substitution using Sn4+ as an example.The second part of this presentation will focus on investigations into the synthesis, structure, and electrochemical properties of layered-rock salt composites: xLi2MnO3 • (1-x)LiFeO2. Electrochemical performance of Mn-Fe rich systems is also fundamentally linked to the debated and conflicting theories of oxidation state, local structure, and migration behavior of the Fe3+/4+ red-ox couple. X-ray spectroscopic techniques have been used to address this issue. A composition-structure-property relationship is established within these systems and novel approaches are underway to further improve their electrochemical performance.References Communications Materials 2020, 1 (1), 99. Accounts of Chemical Research 2015, 48 (11), 2813-2821. Journal of The Electrochemical Society 2023, 170 (3), 030509.

Effect of Ash and Sulphate on Corrosion of Ni-Based Alloys in a Simulated Oxyfuel Combustion Environment

AbstractAlloys of Ni–25Cr–(2Mn–1Si) under mixed deposits of ash + (0, 10, 50 and 90) wt% sulphate were exposed to an Ar–60CO2–20H2O gas at 650 and 750 °C for up to 300 h, forming both protective chromia and regions of Ni-rich oxide. The presence of ash + sulphate mixtures improved Ni–25Cr alloy protection, increasing surface coverage by thin, protective chromia compared with the deposit-free condition. Increasing sulphate proportions in these mixtures led to an accelerated chromia scale growth and reduced internal oxidation zone (IOZ). These beneficial effects were more significant at 750 °C, where surface coverage by the protective scale was increased, and a chromia band was formed beneath nonprotective regions at the IOZ-substrate interface. Alloy additions of Mn and Si generally slowed the growth of outer NiO and IOZ but did not lead to exclusive chromia scale formation.

Synthesis, characterization, and evaluation of improved electrochemical performance of vanadium and zinc co-doped Ni-rich oxide cathode materials: experimental and first-principles study

Synthesis, characterization, and evaluation of improved electrochemical performance of vanadium and zinc co-doped Ni-rich oxide cathode materials: experimental and first-principles study

A Plastic-Crystal Electrolyte Layer Promotes Interfacial Stability of Ni-Rich Oxide Cathode in Li6PS5Cl-Based All-Solid-State Rechargeable Li Batteries.

Unfavorable parasitic reactions between the Ni-rich layered oxide cathode and the sulfide solid electrolyte have plagued the realization of all-solid-state rechargeable Li batteries. The accumulation of inactive by-products (P2Sx, S, POx n- and SOx n-) at the cathode-sulfide interface impedes fast Li-ion transfer, which accounts for sluggish reaction kinetics and significant loss of cathode capacity. Herein, we proposed an easily scalable approach to stabilize the cathode electrochemistry via coating the cathode particles by a uniform, Li+-conductive plastic-crystal electrolyte nanolayer on their surface. The electrolyte, which simply consists of succinonitrile and Li bis(trifluoromethanesulphonyl)imide, serves as an interfacial buffer to effectively suppress the adverse phase transition in highly delithiated cathode materials, and the loss of lattice oxygen and generation of inactive oxygenated by-products at the cathode-sulfide interface. Consequently, an all-solid-state rechargeable Li battery with the modified cathode delivers high specific capacities of 168 mAh g-1 at 0.1 C and a high capacity retention >80 % after 100 cycles. Our work sheds new light on rational design of electrode-electrolyte interface for the next-generation high-energy batteries.

Resynthesis of Ni-rich lithium nickel manganese cobalt oxide cathode materials from the industrial leachate of spent Li-ion batteries: The effect of PF6− species from electrolyte

A significant rise in the generation of spent Li-ion batteries (LIBs) is expected due to the widespread usage of LIBs in various applications. The benefit of spent LIB valorization can be maximized by a high value-added recycling process. The resynthesis of cathode active materials (CAMs), a promising recycling method that directly produces CAMs from LIB leachate, is explored in this study. We resynthesize Ni-rich LiNi0.9Co0.05Mn0.05O2 (NCM955) CAMs via coprecipitation and sintering by varying the amount of PF6−, which can raise environmental concerns, in industrial LIB leachate. Our first employment of glow discharge mass spectrometer in the investigation of PF6− decomposition behavior reveals that the small amounts of PO43− are precipitated into NCM precursors and F− remains in the leachate during resynthesis process. The incorporation of PF6− species during the coprecipitation results in an enlargement of crystal lattice parameters. The incorporated PF6− species increases the ratio of Ni2+ to Ni3+ and leads to the formation of LixPOyFz on the surface of NCM, which exerts a positive effect on the overall LIB performance. This study is the first attempt where the effect of PF6− species from LIB electrolyte is investigated in the resynthesis of the state-of-the-art NCM955 from industrial LIB leachate.

Surface-to-bulk synergistic modification enables stable interface of Ni-rich oxide cathode for all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) are supposed to a highly forward-looking battery technology by reason of their conspicuous energy density and excellent safety. Ni-rich layered oxide cathodes have been extensively studied in ASSLB systems with sulfide electrolytes owing to their high voltage and preeminent specific capacity. However, the electrochemical performance of ASSLBs is severely degraded due to the interfacial physical contact failure, space charge layer effect, and chemical/electrochemical side reactions between sulfide electrolytes and Ni-rich oxide cathodes. In this work, the surface of LiNi0.92Co0.04Mn0.04O2 (NCM92) is coated with a nano-level CeO2 buffer layer and is simultaneously doped with Ce element (NCM92–1%Ce) by one-step wet chemical method. Ce doping is beneficial for maintaining structural stability and suppressing irreversible phase transition. The CeO2 buffer layer can efficaciously avoid the oxidation and decomposition phenomenon at the interface between NCM92 and sulfide electrolyte. As expected, NCM92–1%Ce cathode shows the discharge specific capacity of 141.46 mAh g−1 after 80 cycles at 0.2C with 79.32% capacity retention rate, which is much higher than that of the unmodified NCM92 cathode. The results indicate that the surface-to-bulk synergistic modification strategy can successfully improve the structure toughness and interface stability of Ni-rich oxide cathode for ASSLBs with sulfide electrolytes.

Effect of high-energy shot peening process on the oxidation behaviour of AISI 321 stainless steel at 900 °C

ABSTRACT The present work comparatively investigates the oxidation behaviour of AISI 321 austenitic stainless steel at 900 °C in Ar-21vol.%O2 in two conditions of solution annealed (SAed) and after a high-energy shot peening process (HESPed). Kinetic observations indicated that during the initial 25 h of oxidation, the HESPed sample exhibits higher oxidation kinetics. However, as oxidation progresses, the kinetics of the SAed sample surpasses in a way that after 150 h, the weight gain for SAed is 0.93 mg/cm2, and for HESPed, it is 0.71 mg/cm2. GI-XRD results after 150 h of oxidation revealed similar oxide phases on both samples, including (Cr,Fe)2O3, Mn(Fe,Cr)2O4, and Fe2O3. An important point is that the oxide formed on the surface of the SAed sample, unlike HESPed, undergoes severe spallation and cracking after 150 h, leading to sub-surface oxidation and the formation of Ni-rich oxide phases such as Ni(Fe,Cr)2O4. The enhancement observed in the oxidation performance of the HESPed sample can be ascribed to the augmented density of high-diffusivity paths, a consequence of the high-energy shot peening process, and the prompt development of uniform inner Si-rich and intermediate Cr-rich oxide layers.

Comprehensive Study of Ti and Ta Co-Doping in Ni-Rich Cathode Material LiNi0.8Mn0.1Co0.1O2 Towards Improving the Electrochemical Performance.

Layered Ni-rich oxides (LiNi1-x-yCoxMnyO2) cathode materials are of current interest in high-energy-demanding applications, such as electric vehicles because of high discharge capacity and high intercalation potential. Here, the effect of co-doping a small amount of Ti and Ta on the crystal structure, morphology, and electrochemical properties of high Ni-rich cathode material LiNi0.8Mn0.1Co0.1-x-yTixTayO2 (0.0≤x+y≤0.2) was systematically investigated. This work demonstrates that an optimum level of Ti and Ta doping is beneficial towards enhancing electrochemical performance. The optimal Ti4+ and Ta5+ co-doped cathode LiNi0.8Mn0.1Co0.09Ti0.005Ta0.005O2 exhibits a superior initial discharge capacity of 161.1 mAh g-1 at 1 C, and excellent capacity retention of 87.1 % after 250 cycles, compared to the pristine sample that exhibits only 59.8 % capacity retention. Moreover, the lithium-ion diffusion coefficients for the co-doped cathode after the 3rd and 50th cycles are 9.9×10-10 cm2 s-1 and 9.3×10-10 cm2 s-1 respectively, which is higher than that of the pristine cathode (3.3×10-10 cm2 s-1 and 2.5×10-10 cm2 s-1 respectively). Based on these studies, we conclude that Ti and Ta co-doping enhances structural stability by mitigating irreversible phase transformation, improving Li-ion kinetics by expanding interlayer spacing, and nanosizing primary particles, thereby stabilizing high-nickel cathode materials and significantly enhancing cyclability.

First-principles study of the structures and redox mechanisms of Ni-rich lithium nickel manganese cobalt oxides

To reduce the cobalt (Co) content in lithium-ion batteries, Ni-rich (high-Ni) lithium nickel manganese cobalt oxides (NMC) are pursued as one of the next-generation cathode materials. However, there is still debate on the crystal and electronic structures of the baseline, LiNiO2. Density Functional Theory (DFT) calculations were performed to provide a theoretical understanding of Ni-rich NMC. First, it was found that the commonly used R3¯m structure for LiNiO2 is metallic, contrary to the experimentally reported mix-conducting behavior. Among the four different space groups, R3¯m, C2/m, P21/c, and P2/c, P2/c with charge disproportionation of Ni2+ and Ni4+ is the most energetically stable and semiconducting structure of LiNiO2. Therefore, the atomic structures of representative Ni-rich NMC were built by partially replacing Ni with Co or Mn in the P2/c LiNiO2 to form LixNiyMnzCo1-y-zO2. In the fully lithiated (x = 1.0) high Ni content NMC (y > 0.5), the oxidation state of all Mn ions becomes 4+, while Co ions still maintain 3+, and part of the Ni ions become 2+ to compensate for the charge. Upon delithiation, the local environment shows more variation of the charge states on the transition metal (TM) ions. The average oxidation on each TM follows a sequence of losing electrons that starts from Ni2+ to Ni3+, then oxidizing Ni3+ and Co3+, while Mn4+ remains electrochemically inactive till x = 0. A general relationship for the oxidation state change in each TM as a function of x and y is derived and shows agreement with both modeling and experimental data.

Homogenous coating of Li+ conductive Li5AlO4 on single-crystalline nonstoichiometric Li1.04Ni0.92Al0.04O2 for rechargeable lithium-ion batteries

Cobalt-free, nickel-rich LiNi1-xAlxO2 (x ≤ 0.1) is an attractive cathode material because of high energy density and low cost but suffers from severe structural degradation and poor rate performance. In this study, we propose a molten salt-assisted synthesis in combination with a Li-refeeding induced aluminum segregation strategy to prepare Li5AlO4-coated single-crystalline slightly Li-rich Li1.04Ni0.92Al0.04O2. The symbiotic formation of Li5AlO4 from reaction between molten lithium hydroxide and doped aluminum in the bulk ensures a high lattice matching between the Ni-rich oxide and the homogenous conductive Li5AlO4 that permits high Li+ conductivity. Benefiting from mitigated undesirable side reactions and phase evolution, the Li5AlO4-coated single-crystalline Li1.04Ni0.92Al0.04O2 delivers a high specific capacity of 220.2 mA h g−1 at 0.1 C and considerable rate capability (182.5 mA h g−1 at 10 C). Besides, superior capacity retention of 90.8% is obtained at 1/3 C after 100 cycles in a 498.1 mA h pouch full cell. Furthermore, the particulate morphology of Li1.04Ni0.92Al0.04O2 remains intact after cycling at a cutoff voltage of 4.3 V, whereas slightly Li-deficient Li0.98Ni0.97Al0.05O2 features intragranular cracks and irreversible lattice distortion. The results highlight the value of molten salt-assisted synthesis and Li-refeeding induced elemental segregation strategy to upgrade Ni-based layered oxide cathode materials for advanced Li-ion batteries.

LiNbO3 Coating and F- Doping Stabilize the Crystal Structure and Ameliorate the Interface of LiNi0.88Co0.06Mn0.03Al0.03O2 to Improve the Electrochemical Properties and Safety Capability.

Ni-rich layered materials Li[NixCoyMnzAl1-x-y-z]O2 (x > 0.8) are regarded as the competitive cathode for practical applications in lithium-ion batteries owing to the large discharging capacity. Nevertheless, the strong oxidation activity, the poor structure, and the thermal stability at the electrode-electrolyte interface would lead to much trouble, for example, inferior electrochemical properties and acute safety issues. To ameliorate the above problems, this work reports a strategy for the double modification of F- doping and LiNbO3 covering in LiNi0.88Co0.06Mn0.03Al0.03O2 cathode via using high-temperature calcining and ball-milling technology. As a result, the cathodes after F- doping and LiNbO3 covering not only demonstrate a more stabilized crystal structure and particle interface but also reduce the release of high-activity oxygen species to ameliorate the thermal runaway. The electrochemical tests show that the LiNbO3-F--modified cathode displays a superior rate capability of 159.3 mAh g-1 at 10.0 C and has the predominant capability retention of 92.1% in the 200th cycle at 25 °C, much superior than those (125.4 mAh g-1 and 84.0%) of bare cathode. Thus, the F- doped and LiNbO3-coated Ni-rich oxides could be a promising cathode to realize the high capacity and a stabilized interface.

Mechanically reinforced Ni-rich cathodes for High-Power and Long-Life All-Solid-State batteries

Mechanical integrity is crucial for the intra-particle ionic/electronic transfer in all-solid-state batteries. However, electrode particles suffer severe electrochemo-mechanical degradations during electrode compaction and high-voltage operation, which is extremely true in the popular high-energy cathodes of fragile polycrystalline Ni-rich oxides composed of loosely stacked nanoparticles. Herein, we develop mechanically reinforced polycrystalline Ni-rich cathodes consisting of densely packed large-size primary particles based on a scalable microstructure engineering strategy. The structural characterization and finite element simulation results demonstrate that this well-designed microstructure of cathodes can suppress the stress/strain accumulation and formation of cracks, and thus maintain the original microstructure and highly percolated ionic/electronic networks. All-solid-state batteries based on mechanically reinforced Ni-rich cathodes achieve significantly improved specific capacity, rate capability, and cyclic stability. This work provides a new sight for designing advanced cathodes to boost the development of high-power and long-life all-solid-state batteries.

Research on new Taylor flow reactor to prepare Ni-rich oxide and LLZO ceramic Li+ ion conductors

New, green technologies are better for the environment and this is increasingly important in the context of worsening global warming and climate change. With the prevalence of battery powered devices, an important part of this is improved battery technology with improved performance and enhanced energy efficiency. Professor Chun-Chen Yang, Department of Chemical Engineering, Ming Chi University of Technology, Taiwan is also a director of the Battery Research Centre of Green Energy (BRCGE), Taiwan, which is conducting R&D on new, revolutionary battery technologies. A focus for Yang and his team is lithium (Li) batteries and new versions that incorporate different elements, with a view to improving energy storage capacity and green sustainable energy practices. He recognises the need to increase the energy density and safety of these batteries in order to meet the requirements of future applications and is exploring the benefits of using a full solid-state Li metal battery (ASSLMB). The researchers are conducting studies using a Taylor flow reactor to prepare Ni-rich oxide and LLZO ceramic Li+ ion conductors and have already yielded advantages and they hope, in the future, the method can be adopted on a wide scale and lead to the development of new and improved batteries. First, the team is keen to overcome issues associated with the difficulty of controlling uniformity and quality.

Comparison and mechanism research of corrosion behavior of materials used in supercritical water-cooled reactors

In this study, the corrosion characteristics of essential materials used in supercritical water-cooled reactors (SCWRs) were investigated. Austenitic stainless steels 304 SS and 316 SS and nickel-based alloys 625 and 800 were exposed to supercritical water (SCW) at 500 °C and 25 MPa. The results showed that 304 SS, 316 SS, and Alloy 800 formed a double oxide layer, with the outer and inner layers enriched in Fe and Cr/Ni, respectively. Alloy 625 formed outer Ni-rich oxides (mainly NiO) and inner Cr-rich oxides and Ni-Cr oxides (mainly Cr2O3 and NiCr2O4, respectively). The results indicated that the difference in the protective performance of the corrosion products was mainly due to the Cr content, and the order of corrosion resistance was Alloy 625 > Alloy 800 > 304 SS > 316 SS. In addition, a corrosion mechanism model was established, which lays a good foundation for corrosion prediction and protection in SCWRs.

Revealing proton-coupled exchange mechanism in aqueous ion-exchange synthesis of nickel-rich layered cathodes for lithium-ion batteries

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries, leading to enhanced structural stability. However, the underlying mechanisms of ion exchange are still not fully understood. Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure. Herein, we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations. Our results reveal that the reaction pathway of ion exchange can be divided into two steps: protonation and lithiation. The proton is the key to achieving charge balance in the ion exchange process, as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis. In addition, the intermediate product shows high lattice distortion during ion exchange, but it ends up with a most stable product with high lattice energy. Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability. This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials, which advances the development of cathode materials for high-performance lithium-ion batteries.

Boosting the electrochemical performance of the Ni-rich LiNi0.96Co0.02Mn0.02O2 cathode by high-valence Zr/Mo dual-doping.

Ni-rich oxides are attractive high-energy cathodes for lithium-ion batteries but suffer from inherent instability. Herein, we employed an ectopic Zr4+/Mo6+ dual-doping strategy to reinforce the layered structure through robust M-O bonds and the pillar effect. This strategy mitigates lattice distortion during cycling and inhibits the interface side reactions.

Advantageous electrochemical behaviour of new core–shell structured cathodes over nickel-rich ones for lithium-ion batteries

A core–shell structured Ni-rich NMC oxide (NR-CS) exhibits a specific capacity of 212 mA h g−1 with 89% capacity retention compared to the 67% capacity retention for LiNi0.85Mn0.10Co0.05O2 (NMC85) after 120 cycles when tested at 20 mA g−1.