Nickel-rich Cathode Materials Research Articles

NaH2PO4 as an Electrolyte Additive for Enhanced Thermal Stability of LiNi0.8Co0.1Mn0.1O2/Graphite Batteries

The wide use of nickel-rich layered cathode materials is plagued by their severe degradation at elevated temperatures. In this study, we introduce monobasic sodium phosphate (NaH2PO4) (P2) as a versatile electrolyte additive that improves the thermal stability of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material. P2 remarkably enhances the cycle and storage performances of NCM811/graphite cells at 60 °C. We elucidate that P2 plays a beneficial role in two ways: (i) it forms a conductive and protective cathode-electrolyte interphase layer that suppresses electrolyte decomposition and NiO-phase formation on the cathode; (ii) it controls the hydrofluoric acid content, and thus decelerates the formation of NiO-phase on the cathode and the degradation of the solid electrolyte interphase layer on the anode. Considering its excellent thermal stability and practical availability, P2 is a promising electrolyte additive for Ni-rich NCM cathodes that suffer from poor thermal stability.

Synthesis of Single Crystal LiNi0.92Co0.06Mn0.01Al0.01O2 Cathode Materials with Superior Electrochemical Performance for Lithium Ion Batteries

Compared to conventional polycrystallines, single crystal layered cathode materials exhibit the excellent structural and thermal stability, storage and lifetime at high voltage and elevated temperature. However, these single crystal materials are less reported, especially for Ni ≥ 0.92 in nickel-rich cathode materials. In this paper, single crystal LiNi0.92Co0.06Mn0.01Al0.01O2 (NCMA) cathode materials are researched. The experiment demonstrates that co-doping fluxing agents in B-NCMA (NCMA with 1000ppm W and 1000 ppm Mo) sample facilitate to generate uniform and small crystal size, which delivers a high initial discharge capacity of 221.4 mAh g−1 at 0.1 C. Moreover, the superior capacity retention of 94.9% after 100th cycle at 45 °C is obtained. Furthermore, DSC analysis of cycled B-NCMA material displays high thermal release temperature and low gas emission, revealing decent thermal stability. XRD, dQ·dV−1 and EIS results suggest that co-doping fluxing agents beneficial to form less cationic mixing, more stable phase structure and less internal resistance, respectively, which are associated with excellent rate capacity, cycling and thermal stability of single crystal NCMA. In our opinion, this study will stimulate that more fluxing agents are found and applied on single crystal nickel-rich cathode materials, which will have a bright future in the high-energy lithium ion battery fields.

Superior Electrochemical and Kinetics Performance of LiNi0.8Co0.15Al0.05O2 Cathode by Neodymium Synergistic Modifying for Lithium Ion Batteries

The nickel-rich layered cathode material LiNi0.8Co0.15Al0.05O2 (NCA) is receiving enormous attention for its high energy density and low cost. Nevertheless, its wide application is limited by its unsatisfactory cycle performance and rate performance. In this study, the synergetic modification of the Nd2AlO3N coating and Nd3+ doping is realized to enhance the electrochemical performance of NCA. The Nd2AlO3N coating can protect the electrode-electrolyte interface and inhibit the side reactions. In the meantime, the Nd3+ doping, with the larger ion radius of Nb3+ and stronger Nd-O bond energy, can effectively enhance the kinetics performance and stabilize the crystal structure of the NCA cathode material. The modified materials with above characters demonstrate an excellent electrochemical stability and kinetics performance, among which the Nd4000 sample has the quite best performance, and its capacity/capacity retention still reach 168 mAh·g−1/91% after 200 cycles, which are distinctly higher than the pristine 144.6 mAh·g−1/78.5%. The electrochemical impedance spectra and cyclic voltammetry results also demonstrate that the charge transfer resistance and electrode polarization are suppressed with neodymium modifying during the cycle, and the lithium ion diffusion coefficient is significantly increased compared with the pristine sample.

An Optimized Synthetic Process for the Substitution of Cobalt in Nickel-Rich Cathode Materials

An Optimized Synthetic Process for the Substitution of Cobalt in Nickel-Rich Cathode Materials

A Novel Core-shell Structured Nickel-rich Layered Cathode Material for High-energy Lithium-ion Batteries

A Novel Core-shell Structured Nickel-rich Layered Cathode Material for High-energy Lithium-ion Batteries

Revealing the correlation between structural evolution and Li+diffusion kinetics of nickel-rich cathode materials in Li-ion batteries

Slow lithium diffusion kinetics of H1 phase during discharge determines the initial irreversible capacity loss of NCM-based materials. By controlling lithium diffusion rate in the discharge process, extra capacity is obtained in the materials.

Synthesis and Characterization of Material LiNi0.8Co0.15Al0.05O2 Using One-Step Co-Precipitation Method for Li-Ion Batteries

<p>Li-ion battery is an energy storage device which could be applied as power source for electronic devices. The capacity of a battery is determined by the cathode material. Over this last decade, high nickel content cathode material is applied for electric vehicular technology. This study aims to synthesize a nickel-rich cathode material, LiNi<sub>0.8</sub>Co<sub>0.15</sub>Al<sub>0.05</sub>O<sub>2 </sub>(NCA) via one-step co-precipitation and study its characteristics. The Ni, Co and Al metal ion conversion during co-precipitation were analyzed using Atomic Adsorption Spectroscopy (AAS). Based on X-Ray diffraction analysis, NCA sample exhibited hexagonal-layered structure with high crystallinity. Based on Scherrer equation, the mean crystallite diameter of NCA sample is 40 nm. Scanning electron microscope (SEM) showed micron-sized homogenous particles with smooth surface. The final composition of Ni, Co and Al metal were confirmed using XRF. The capacity of the battery was determined using galvanostic test method with voltage range of 2.7-4.25 V using graphite as the counter anode. The initial specific discharge capacity of NCA is 60 mAh/g while the capacity loss<em> per cycle is </em><em>1</em><em>%.</em></p>

Well-ordered layered LiNi0.8Co0.1Mn0.1O2 submicron sphere with fast electrochemical kinetics for cathodic lithium storage

Abstract Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost. However, nickel-rich layered oxides also have exposed several defects for commercial application, such as uncontrollable ordered layered structure, which leads to higher energy barrier for Li+ diffusion. In addition, suffering from structural mutability, the bulk nickel-rich cathode materials likely trigger overall volumetric variation and intergranular cracks, thus obstructing the lithium ion diffusion path and shortening the service life of the whole device. Herein, we report well-ordered layered LiNi0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage. The as-fabricated LiNi0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1, remarkable energy density of 866 Wh kg–1, rapid Li ion diffusion coefficient (10–9 cm2 s–1) and low voltage decay. The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles, which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance. This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.

Controllable synthesis of spherical precursor Ni0.8Co0.1Mn0.1(OH)2 for nickel-rich cathode material in Li-ion batteries

Synthesis of precursor Ni0.8Co0.1Mn0.1(OH)2 in regular sphere shape as nickel-rich cathode material for Li-ion batteries remains challenging. Here, we report that the morphology of Ni0.8Co0.1Mn0.1(OH)2 can be tuned by controlling the reaction conditions of co-precipitation. The effects of the concentration of NH3·H2O, pH of reaction solution, and stirring speed were studied in detailed. Precursor Ni0.8Co0.1Mn0.1(OH)2 with outstanding spherical hierarchical structure was successfully prepared. The cathode material of LiNi0.8Co0.1Mn0.1O2 was then synthesized based on the prepared Ni0.8Co0.1Mn0.1(OH)2. It showed excellent crystal structure, morphology and electrochemical properties. Within the voltage range of 2.7–4.3V, the initial discharge specific capacity was 203.7mAh·g-1 and 198.8mAh·g-1 at rate of 0.1C and 0.2C (1C = 200 mA g-1, at 30°C), and the capacity retention were 94.4% and 88.0% for 100cycles and 200cycles (0.2C, at 30°C), respectively.

Thermal stress-induced charge and structure heterogeneity in emerging cathode materials

Nickel-rich layered oxide cathode materials are attractive near-term candidates for boosting the energy density of next generation lithium-ion batteries. The practical implementation of these materials is, however, hindered by unsatisfactory capacity retention, poor thermal stability, and oxygen release as a consequence of structural decomposition, which may have serious safety consequences. The undesired side reactions are often exothermic, causing complicated electro-chemo-mechanical interplay at elevated temperatures. In this work, we explore the effects of thermal exposure on chemically delithiated LiNi0.8Mn0.1Co0.1O2 (NMC-811) at a practical state-of-charge (50% Li content) and an over-charged state (25% Li content). A systematic study using a suite of advanced synchrotron radiation characterization tools reveals the dynamics of thermal behavior of the charged NMC-811, which involves sophisticated structural and chemical evolution; e.g. lattice phase transformation, transition metal (TM) cation migration and valence change, and lithium redistribution. These intertwined processes exhibit a complex 3D spatial heterogeneity and, collectively, form a valence state gradient throughout the particles. Our study sheds light on the response of NMC-811 to elevated temperature and highlights the importance of the cathode’s thermal robustness for battery performance and safety.

LiTa2PO8 coated nickel-rich cathode material for improved electrochemical performance at high voltage

LiNi0.8Co0.1Mn0.1O2 (NCM) will have higher energy density at high voltage, but severe electrochemical polarization and capacity decay are likely to occur because of structural degradation. In this paper, LiTa2PO8 is used as a coating layer to modify the NCM. Covered with a 2–4 nm coating layer, the material structure does not change significantly, and the structure is more stable. More importantly, LiTa2PO8 has an ordered channel with three-dimensional Li+ ion transport, which plays a key role in improving Li+ transmission efficiency. The results show that the electrochemical properties of the material are significantly improved after coating at high voltage. After 100 cycles, the capacity retention increases from 71.58% to 84.85%, voltage stability also notably improved, the polarization is weaker, and the reversible charge and discharge capacity at high rate (3C) is significantly higher than that of raw materials. The change in morphology after 100 cycles proves that the LiTa2PO8 coating prevents direct contact between the cathode materials and the electrolyte, inhibits the side reaction and enhance the surface structure stability of the cathode materials.

Improved Stability of Layered and Porous Nickel-Rich Cathode Materials by Relieving the Accumulation of Inner Stress.

The commercial application of high-capacity LiNi0.8 Co0.1 Mn0.1 O2 is impeded by its inferior cycling stability, which has been attributed to structural instability caused by stress accumulation during both calcination and cycling. A porous structure was deliberately introduced into nickel-rich material particles to relieve such stress. Cross-sectional SEM and mercury penetration tests confirmed the successful construction of a porous structure. Ex situ TEM and powder XRD confirmed that the porous structure reduced the stress concentration regions in uncycled nickel-rich material by providing a buffer space. In addition, the porous structure helps the permeation of the electrolyte and alleviates the stress accumulation during cycling, endowing the nickel-rich cathode materials with enhanced rate capability and suppressed phase transition. This strategy can be extended for the synthesis of diverse nickel-rich cathode materials to improve their cycling stability.

A first report on ex-situ synthesis and utilization of pure La4NiLiO8 in emerging high-performance safe batteries

Layered nickel-rich cathode materials such as LiNi0.5Co0.2Mn0.3O2 (NCM523) possess huge potential in developing high-performance secondary batteries. However, the micron-sized particles of NCM523 in electrode laminates produce spacious interparticle voids (electronically dead zones) which dampen the charge transference and cause bulk material degradation after interaction with the excessive liquid electrolyte within the voids, thus alarming their safe and confident use in batteries. In this context, we hereby ex-situ synthesize a highly electro-ionically conductive pure La4NiLiO8 for potential use as a voids-filling agent in enhancing the electrochemical performance and durability of the layered energy storage NCM523. The morphological and crystallinity analyses in conjunction with the thermal treatments confirm high stability of La4NiLiO8 up to 1150 °C, exceptionally low resistances, and fast charge conduction (335 mS cm−1). A simplistic but scientifically important filling of the inter-particle voids with only 6% of La4NiLiO8 decreases the charge transfer resistance from 103.2 to 19 Ω cm2, increases the discharge capacity from 185 mAh g−1 to 214 mAh g−1 at 0.2C, and enhances the capacity retention from 58.9 to 81.5% (after 500 cycles at 1C). Thus, the excellent physico-thermo-electrochemical characteristics and stability of La4NiLiO8 as a voids-filling agent are highly beneficial for developing high-performance safe secondary batteries.

Air-Induced Degradation and Electrochemical Regeneration for the Performance of Layered Ni-Rich Cathodes.

Nickel-rich layered oxides are promising cathodes for power batteries owing to their high capacity and low cost. However, during the production, storage, and application of nickel-rich cathodes, especially in case the Ni content exceeds 70%, their surfaces almost inevitably react with ambient air to form electrochemically inert Li2CO3 and LiOH, leading to significant capacity loss and therefore imposing a significant hurdle to practical applications of nickel-rich cathodes. Here, we reveal surface structures and electrochemical properties of the exposed LiNi0.8Co0.15Al0.05O2 (NCA) cathodes and investigate systematically the impact of exposure humidity, temperature, and time on NCA cathodes. We demonstrate that introduction of a 3.0-4.5 V galvanostatic cycling operation at initial cycles can remarkably regenerate the subsequent 3.0-4.3 V battery performances of the exposed cathode. This work represents a facile method to regenerate the battery performance of surface-degraded nickel-rich cathodes, opening up an avenue in fulfilling efficient production, storage, and application of nickel-rich cathode materials.

Targeted Surface Doping with Reversible Local Environment Improves Oxygen Stability at the Electrochemical Interfaces of Nickel-Rich Cathode Materials

Elemental doping represents a prominent strategy to improve interfacial chemistry in battery materials. Manipulating the dopant spatial distribution and understanding the dynamic evolution of the dopants at the atomic scale can inform better design of the doping chemistry for batteries. In this work, we create a targeted hierarchical distribution of Ti4+, a popular doping element for oxide cathode materials, in LiNi0.8Mn0.1Co0.1O2 primary particles. We apply multiscale synchrotron/electron spectroscopy and imaging techniques as well as theoretical calculations to investigate the dynamic evolution of the doping chemical environment. The Ti4+ dopant is fully incorporated into the TMO6 octahedral coordination and is targeted to be enriched at the surface. Ti4+ in the TMO6 octahedral coordination increases the TM-O bond length and reduces the covalency between (Ni, Mn, Co) and O. The excellent reversibility of Ti4+ chemical environment gives rise to superior oxygen reversibility at the cathode-electrolyte interphase and in the bulk particles, leading to improved stability in capacity, energy, and voltage. Our work directly probes the chemical environment of doping elements and helps rationalize the doping strategy for high-voltage layered cathodes.

Application of nano Al2O3 particles as precipitate nucleus for preparation of high rate nickel-rich cathode materials

Nickel-rich layered oxide LiNi1-x-yCoxAlyO2 (x + y < 0.4) cathodes are regarded as the most promising candidate cathodes for lithium ion batteries due to their high energy density, high work voltage and low cost. These cathodes are extensively used in electric vehicles and hybrid electric vehicles. Generally, coprecipitation methods are frequently employed for preparing nickel-rich cathodes, but the coprecipitation of Ni2+, Co2+ and Al3+ is very complicated and uncontrollable because the solubility product constants of Ni(OH)2, Co(OH)2 and Al(OH)3 are entirely different. This paper reports a modified coprecipitation method for the preparation of LiNi0.75Co0.15Al0.10O2, in which nano Al2O3 particles are employed as precipitate nucleus for the first time. Additionally, to magnify the difference between the different synthesis methods, a fluctuating pH environment is intentionally employed for the solution during the coprecipitation. Unlike the conventional method, the modified method successfully avoids the stringent demands for pH value during the synthesis, and the as-obtained LiNi0.75Co0.15Al0.10O2 cathode exhibits an excellent rate capability of 172.2 mAh g−1 at a rate of 10 C. Even more remarkably, the LiNi0.75Co0.15Al0.10O2 cathode presents significantly improved thermal/structural stability and electrochemical performance at high temperature, indicating its great potential for use as a commercial lithium ion battery cathode in electric vehicles and hybrid electric vehicles.

Aging Study of the Lithium Metal Batteries Using Nickel-Rich Cathode Materials

The lithium ion battery (LIB) is the most important energy storage device since the last decade, which is due to the excellent characteristics of operating voltage, cycle life and its low self-discharge rate. [1]. Nevertheless lithium ion batteries are gradually reaching their theoretical limits, in terms of energy density, power density as wells as durability and cost [2, 3]. Because electronic portables devices as wells as electric vehicles demand high energy density batteries, the development of next generation batteries has strongly increased during the recent years. To achieve high energy densities in these systems, lithium is used as anode due to its outstanding properties regarding the theoretical specific capacity (3860 mAh g-1) and the negative electrochemical potential (-3.04V vs. standard hydrogen electrode). However, the rapid degradation as well as safety issues related to the morphological transformation from dense to porous lithium metal affect the cell performance [4-7]. In this work, we studied the influence of the test conditions on the morphological changes on the lithium anode and cycle life of the lithium metal battery (LMB). For this, we carried out ex-situ measurements for a better understanding of the morphological changes of the anode material. Depending on the applied conditions, the cycle life of the system was improved with lower capacity fading and at the same time the morphological changes of the lithium anode were suppressed. In the second part, the investigation is focused into the degradation of different nickel-rich cathode materials. Most of the studies on lithium metal batteries are based on the degradation of the lithium anode, however, here; it could be shown that aging of the cathode material is an important part for the development of the LMB. The results showed a good cycle performance over 300 cycles with relative low capacity fading of the LMB with all the implemented cathodes. The electrochemical data analysis showed the degradation of the cathode material, controlling at the same time the morphological changes of the lithium anode. Literature [1] J. Ma, B. Chen, L. Wang, G. Cui, J. Power Sources, 392, 94 (2018) [2] H. Hao, X. Cheng. Z. Liu, F. Zhao, Energy Pol., 108, 355 (2017) [3] A. Mahmoudzadeh Andwari, A. Pesiridis, S. Rajoo, R. Martinez-Botas, V. Esfahanian, Renew. Sustain. Energy Rev., 78, 414 (2017) [4] D. Lu, Y. Shao, T. Lozano, W. D. Bennett, G. L. Graff, B. Polzin, J. Zhang, M. H. Engelhard, N. T. Saenz, W.A. Henderson, P. Bhattecharya, J. Liu, J. Xiao, Adv. Energy Mater., 5, 1400993 (2015) [5] K. Xu, Chem. Rev., 104, 4303 (2004) [6] D. Aurbach, E. Zinigrad, Y. Cohen, H. Teller, Solid State Ionics, 148, 405 (2002) [7] J. B. Goodenough, Y. Kim, Chem. Mater., 22, 587 (2010) Figure 1

Investigating the Electrochemical Effect of Core-Multi Shell Structured Nickel-Rich NMC Cathode Materials

Nickel-rich nickel manganese cobalt (NMC) oxide is a high energy density cathode material for lithium-ion batteries. However, surface-related fast capacity fading has been a major obstacle to its practical application. In this work, to address this issue, nickel-rich core-multi shell structured NMC oxide Li[Ni0.9-x-yMn0.05+xCo0.05+y]O2 (x and y ≤0.15) materials with multiple outer layers of stable NMC compositions were synthesized via co-precipitation method using a specially developed continuous stirred-tank reactor (CSTR). We have used scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) with cross-sections of the grided particle samples, and inductively coupled plasma mass spectrometry (ICP-MS) to understand the contribution of core and outer shell layers and total composition of the synthesized core-multi shell structured NMC materials. The synthesized cathodes consisted of high-nickel NMC90/5/5 (LiNi0.9Mn0.05Co0.05O2) core and NMC333, NMC622, and NMC811 outer shells have an overall composition of NMC811 or NMC622 depending on outer shell ratio. The analyzed concentration distribution inside the particles indicates that the nickel composition decreases linearly from the center of the particle to the surface and that the manganese and cobalt concentrations increase. The NMC811 and NMC622 of the core-multi-shell structure with optimized outer shell layer improve cycling capacity, capacity retention (92% after 100 cycles) and rate capability as compared to commercial materials having the same overall composition due to the unique microstructure of the stabilized particle surface by increasing the stable Mn4+ ratio at the shell. Electrochemical impedance spectroscopy (EIS) and differential scanning calorimetry (DSC) results showed that the high stability of core-multi shell structured NMC materials is responsible for the reduction in surface and charge transfer resistance by decreasing the reaction with the electrolyte.

A novel synthesis strategy to improve cycle stability of LiNi0.8Mn0.1Co0.1O2 at high cut-off voltages through core-shell structuring

Nickel-rich cathode materials have attracted considerable interest because of their high specific capacities, voltage ranges, and low cost. However, serious capacity attenuation and poor rate performance limit their application. This study proposes a novel strategy to improve the cycle stability of the nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) layer material by designing core-shell LiNi0.8Co0.1Mn0.1O2 (CS-NCM811). CS-NCM811 is designed by the characteristic reaction between dimethylglyoxime (C4H8N2O2) and nickel ion to form Ni(C4H7N2O2)2. The CS-NCM811 is characterized with high nickel content in its core and high manganese content on its surface, leading to a high capacity and excellent cycle stability. The capacity retention of CS-NCM811 was 72.8%, much higher than that of NCM811 (47.1%) after 500 cycles at a rate of 5 C. Not only is this method a novel strategy to design high capacity cathode materials but also provides some new insights into the cycle stability of nickel-rich layered cathode materials.

Investigation into Mechanical Degradation of Lithium-Ion Batteries with Nickel-Rich Cathode Materials - A Long-Term Cycling Study

Layered lithium transition-metal oxides of type LiNi x Co y Mn z O2 (NCM, with x + y + z = 1) are well established and represent the current state of the art cathode materials for different lithium-ion battery applications. The ultimate goal in the area of NCMs is to increase the nickel fraction in the material as much as possible, as this allows for higher specific capacities (for a given charge cutoff voltage). However, recent studies have demonstrated that with increasing practically used capacity the material suffers increasingly from volume changes, eventually leading to mechanical failure. Apart from volume changes, adverse side reactions like structural/morphological changes and/or phase transitions during cycling operation are also possible causes of degradation, affecting capacity retention and overall lifetime of a battery cell. In this work, we report on a long-term study on the structural, electronic and morphological changes of high-nickel NCM/graphite full-cells from operando X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and electrochemical impedance spectroscopy. The acquired data demonstrate that the capacity loss can be attributed predominantly to the cathode side. Using XRD we observed the presence of two differently active NCM phases. However, the NCM cathode material was still found capable of virtually complete Li (de-)lithiation, but with significantly slower kinetics due to, in part, built-up of resistive surface layers with cycling. Figure 1. a) Charge/discharge profiles of LiNi0.85Co0.1Mn0.05O2/graphite full-cells for various cycles at 1C rate and in the voltage range between 2.8 and 4.2 V. b) Phase fractions of the less and more active NCM phases after charging to 4.2 V (including a 1 h CV step). Figure 1