Ni-rich LiNi0 Research Articles

Stabilizing and understanding the interface between nickel-rich cathode and PEO-based electrolyte by lithium niobium oxide coating for high-performance all-solid-state batteries

Abstract The pursuit of high energy density and safe lithium ion batteries (LIBs) is a urgent goal for the development of next-generation electric vehicles (EVs). All-solid-state batteries (ASSBs) with the combination of poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) and Ni-rich lithium nickel manganese cobalt oxide LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode are promising candidates for EVs due to their improved energy density and safety. However, the low electrochemical oxidation window of PEO-based SPE and the instability of NMC811 at the charge/discharge process seriously restrict the battery performance. Herein, a high voltage stable solid-state electrolyte layer lithium niobium oxide (LNO) is coated on the NMC811 electrode surface by atomic layer deposition for stabilizing NMC811-PEO solid polymer batteries. Electrochemical tests show that LNO coating can stabilize the NMC811 active materials and mitigate the decomposition of SPE upon the cycling process, rendering a good performance of NMC811-PEO solid polymer battery. Mechanism studies by SEM, STEM, XAS, and XPS disclose that the uncoated NMC811 suffers from chemomechanical degradations along with oxygen release triggering the decomposition of SPE, which results in unstable cathodic electrolyte interphase. With LNO coating, chemomechanical degradations and oxygen release are inhibited and the decomposition of SPE is mitigated. This work renders a stable and high-performance high-energy-density SSB for high voltage application, which paves the way toward next-generation solid-state LIBs.

The role of the pH value in water-based pastes on the processing and performance of Ni-rich LiNi0.5Mn0.3Co0.2O2 based positive electrodes

The influence of the preset pH value of the binder solution on aqueous processing of LiNi0.5Mn0.3Co0.2O2 positive electrodes is studied. The processed electrodes are investigated by means of electrochemical charge/discharge cycling, potentiostatic electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The results show major impact of the pH value of the binder solution on the cycling performance of lithium ion cells. Low binder solution pH values (here 7.6) lead to faster capacity fading within the first 100 cycles. In comparison, higher binder solution pH values (here 12.5) show similar fading compared to the reference electrodes based on poly(vinylidene difluoride) and N-methyl pyrrolidone as solvent. Positive electrode materials undergo a lithium-proton exchange, when in contact with water or other proton sources. Post-mortem analysis revealed that lower pH values of the binder solution potentially lead to more pronounced lithium-proton exchange. The previously inserted protons are extracted from the active material during electrochemical cycling, potentially initiate decomposition of the conductive salt LiPF6 and hence degrade the cell performance.In combination with LiPF6, inter alia HF might be formed, which then reacts with lithium from LiNi0.5Mn0.3Co0.2O2 or other active and inactive components and precipitate as M-F or other resistive interphases on the LiNi0.5Mn0.3Co0.2O2 surface.

Improving electrochemical performance of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode for Li-ion batteries by dual-conductive coating layer of PPy and LiAlO2

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM) as a high capacity cathode material is the most promising candidate for lithium-ion batteries. However, NCM still suffers from poor rate capability and insufficient cycle stability owing to the poor conductivity as well as side reactions. Here, a dual-conductive coating strategy is employed to address these issues. The PPy-LiAlO2 coated NCM composites (PPy-LA) are synthesized by hydrolysis–hydrothermal approach and in-situ chemical polymerization method. The LiAlO2 coating can suppress side reactions and enhance ionic conductivity, and the PPy coating can increase electronic conductivity. As a result, the PPy-LA sample delivers superior cycling stability and rate capability compared to NCM sample. The capacity retention of PPy-LA is 92.8% after 100 loops and a high capacity of 128 mAh/g is obtained at 2 A/g. This effective surface modification method could shed light on other cathode materials.

Glass ceramic coating on LiNi0.8Co0.1Mn0.1O2 cathode for Li-ion batteries

Alleviating the surface degradation of Ni-rich cathode materials is desirable to achieve better electrochemical performance. Herein, we report the surface coating of lithium diborate (Li2O-2B2O3) over the Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material and the systematic investigation of its electrochemical properties. The structural and morphological properties were characterized through X-ray diffraction (XRD), high resolution field-emission scanning electron microscopy (HR FE-SEM), and high resolution field-emission transmission electron microscopy (HR FE-TEM). As a cathode material for Li-ion batteries, the 1.0 wt% Li2O-2B2O3 coated NCM811 exhibits better electrochemical properties than the bare NCM811 as well as 0.5 and 2 wt% coated electrodes at room and elevated temperatures (60 °C). The improved electrochemical performance of 1.0 wt% Li2O-2B2O3 coated NCM811 might be due to the optimal coating amount that promotes better ion and electron movement along with prevention of surface degradation.

Effects of surface modification and organic binder type on cell performance of water-processed Ni-rich Li(Ni0.8Co0.1Mn0.1)O2 cathodes

The Ni-rich Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) is surface-modified using phosphoric acid (HPO) and silane reagents, and water-based cathode slurries of unmodified and modified NCM811 are prepared with poly(acrylonitrile) (PAN) or poly(acrylic acid) (PAA) added as the binder to compare the electrochemical performances of the constructed cells. Surface modification using HPO or the addition of PAA as the binder can substantially reduce the alkalinity of the prepared aqueous slurry of NCM811, thereby preventing the slurry from corroding the aluminum current collector, as well as retaining the good structural integrity of the dried electrode. The aforementioned advantage about the reduction in the alkalinity is not achieved when the hydrophobic silane-modified NCM811 or the neutral binder PAN is used. The best cell performance in terms of electrochemical reversibility, ionic and electronic impedance, and cycle stability is obtained when the water-based cathode slurry is prepared using HPO-modified NCM811 as the cathode active and PAA as the binder simultaneously. Moreover, the addition of PAA rather than the adoption of HPO-modified NCM811 contributes more to the improvement of cell performance.

Effect of Nb doping on the behavior of NCA cathode: Enhanced electrochemical performances from improved lattice stability towards 4.5V application

Although the Ni-rich LiNi0.8Co0.15Al0.05O2 (N85CA) material has been used as the commercial cathode of electric vehicle battery, the instability of the layered structure and the short lifespan under high voltage cycling prevent its practical application to higher energy density. Herein, Nb-doped N85CA material, with enhanced structural stability and improved cycle stability, is reported to work at 4.5V. In particular, Nb0.5%-N85CA shows the best electrochemical performance, with a discharge capacity of 200.2 mAh/g at 0.1C, and a retention of 94.19% after 100 runs at 0.5 C. As a comparison, the data of the pristine N85CA are 210.2 mAh/g and 69.46%, respectively. Such an obvious increase in the capacity retention is caused by the promoted lattice stability provided by the strong Nb–O bond that inhibits the H2–H3 phase transition in the electrochemical process. The incorporation of Nb5+ ions further increases the interslab thickness that enable a rapid migration of Li ions (2.23 × 10−10 S cm−1 vs. 8.32 × 10−11 S cm−1), and the rate behavior of the cathode is also enhanced. Furthermore, Nb0.5%-N85CA material displays a specific capacity of 156.2 mAh/g at 5 C, while that of the pristine N85CA is 123 mAh/g. The results strongly indicate that such Nb-doped N85CA material has high potential as a cathode candidate, especially for high energy applications.

An effective doping strategy to improve the cyclic stability and rate capability of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) is considered as a promising cathode material for high-capacity power batteries. Nevertheless, the rapid capacity fading during the charge/discharge process and inferior rate capability hinder their successful realization. Elemental doping plays a critical role in stabilizing the structure, inhibiting Li/Ni disorder, reducing polarization, improving electronic conductivity and enhancing Li-diffusion coefficient from the viewpoints of dopant radius, valence state and bonding energy. Herein, niobium (Nb), with optimal radius (0.64 Å), high valence state (Nb5+) and strong Nb-O bonding energy (753 kJ/mol), is introduced into NCM811 structure to improve the electrochemical performance and to evaluate this strategy. Then, X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical characterization are carried out to comprehensively evaluate the influence of Nb-doping on structure and electrochemical performance of NCM811 cathodes. Consequently, NCM811 cathode, with 1 at.% Nb, exhibited the highest capacity retention of 94.55% after 100 charge/discharge cycles (1 C) and rendered a superior charge storage capacity of 151.46 mAh/g at a high current rate of 5 C, demonstrating the effectiveness of the proposed strategy.

Synergistic effect of Li2MgTi3O8 coating layer with dual ionic surface doping to improve electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode materials

Surface modification plays a vital role in improving the rate performance and cycling stability of layered Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials for Li-ion batteries. In this study, Li2MgTi3O8 (LMTO)-coated NCM622 was successfully synthesized by wet coating combined with sintering process. The results of morphological analysis showed a uniform LMTO layer coated on the surface of NCM622 materials. The dual ions of Ti4+ and Mg2+ on surface structure of NCM622 were identified by X-ray diffraction and X-ray photoelectron spectroscopy. The surface coating layer prevented the direct contact between the active cathode material and the electrolyte which significantly reduced the side reactions, and the doping of Ti4+ and Mg2+ improved the structural stability of the NCM622 materials. The electrochemical performance indicates that NCM622 cathode with a coating layer of 0.5 wt% LMTO exhibited excellent cycle stability and maintained a capacity retention up to 76% after 200 cycles at 25 °C at 1 C-rate, which was higher than the value of 52% for the NCM622.

Surface modification of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials via a novel mechanofusion alloy route

This study aimed to prepare a composite coating material comprising a solid ionic conductor of lithium aluminum titanium phosphate (Li1.4Al0.4Ti1.6(PO4)3, LATP) and porous carbon through a sol-gel method. LiNi0.8Co0.1Mn0.1O2 (LNCM811) cathode material with dual-functional composite conductors (i.e., LATP@porous carbon), denoted as LATP-PC, was prepared. The dry-coating method, also called the “mechanical-fusion alloy route,” was used to modify Ni-rich LNCM811 cathode materials. X-ray diffraction (XRD), micro-Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed that the LATP ionic conductor generated herein was uniformly deposited on 3D porous carbon and served as a dual-functional composite coating on LNCM811. Furthermore, the capacity retention of LATP-PC@LNCM811 was approximately 85.57% and 80.86% after 100 cycles at −20 °C and 25 °C, respectively. By contrast, pristine LNCM811 had the capacity retention of 78% and 74.96% at −20 °C and 25 °C, respectively. Furthermore, the high-rate capability of the LATP-PC@LNCM811 material was markedly enhanced to 169.81 mAh g−1 at 10C relative to that of pristine LNCM811, which was approximately 137.67 mAh g−1. The electrochemical performance of LNCM811 was enhanced by the uniform dual-conductive composite coating. The results of the study indicate that the LATP-PC@LNCM811 composite material developed herein is a potentially promising material for future high-energy Li-ion batteries.

High-temperature storage deterioration behaviors of lithium-ion batteries using nickel-rich cathode and SiO–C composite anode

The deterioration behaviors of the lithium-ion pouch full cells consisted of Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and SiO–C composite anode after stored at 55 °C for 7 days were investigated. A significant increase in the interface impedance of the cell and a change in structure of the anode surface passivation films are attributed to constant electrolyte decomposition inducing the regeneration of SEI films, which result in the constant consumption of active lithium source and rapid capacity fading. After high-temperature storage, the initial charge capacity of anode is reduced from 609.1 to 514.3 mAh g−1. Furthermore, the disintegration of NCM811 cathode secondary particle was observed, and after high-temperature storage, the reversible capacity of cathode decreases from 170.6 to 134.9 mAh g−1.

Synthesis of Ni-Rich Layered-Oxide Nanomaterials with Enhanced Li-Ion Diffusion Pathways as High-Rate Cathodes for Li-Ion Batteries

Ni-rich LiNi0.6Co0.2Mn0.2O2 nanomaterials with a high percentage of exposed {010} facets have been prepared by surfactant-assisted hydrothermal synthesis followed by solid-state reaction. Characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) confirmed that the particles have enhanced the growth of nanocrystal planes in favor of Li-ion diffusion. Electrochemical tests show these cathode materials endow a large Li-ion diffusion coefficient, which leads to a superior rate capability and cyclability, suggesting these cathode materials are highly beneficial for practical application in Li-ion batteries.

Influence of Mo addition on the structural and electrochemical performance of Ni-rich cathode material for lithium-ion batteries

Molybdenum modified LiNi0.84Co0.11Mn0.05O2 cathode with different doping concentrations (0–5 wt.%) is successfully prepared and its electrochemical performances are investigated. It is demonstrated that molybdenum in LiNi0.84Co0.11Mn0.05O2 has a positive effect on structural stability and extraordinary electrochemical performances, including improved long-term cycling and high-rate capability. Among all samples, the 1 wt. % molybdenum LiNi0.84Co0.11Mn0.05O2 delivers superior initial discharge capacity of 205 mAh g−1 (0.1 C), cycling stability of 89.5% (0.5 C) and rate capability of 165 mAh g−1 (2 C) compared to those of others. Therefore, we can conclude that the 1 wt. % molybdenum is an effective strategy for Ni-rich LiNi0.84Co0.11Mn0.05O2 cathode used in lithium ion batteries.

Atomic-scale tuned interface of nickel-rich cathode for enhanced electrochemical performance in lithium-ion batteries

The Ni-rich layered LiNi0.6Mn0.2Co0.2O2 (NMC622) is one promising cathode for lithium-ion batteries (LIBs), but suffers from poor cycling stability under high cutoff potentials. The performance degradation was reflected as capacity fading and voltage drop, having their roots in instable interface of NMC622. Aimed at improving interfacial stability, in this study, we deposited nanoscale ZrO2 coatings conformally over NMC622 cathodes using atomic layer deposition (ALD). We found that, under a high cutoff voltage (4.5 V), the ALD ZrO2 coatings evidently improved the performance of NMC622 cathode, showing better cyclability and higher sustainable capacity. In addition, the ALD coatings dramatically boosted the rate capability of NMC622. All these compelling performance results are ascribed to the atomic-scale tunable ZrO2 coatings via ALD, which create stable interface and thereby inhibit unfavorable evolutions. In the study, we utilize a suite of characterization tools and various analyses to clarify the effects of ALD ZrO2 coatings. This study will be helpful for improving the performance of nickel-rich cathodes via interfacial engineering using ALD.

Ultra-Stable Performance of Ni-Rich Layered Oxide Cathodes for Lithium-Ion Batteries Using Ionic Liquid Electrolyte

High energy density lithium-ion batteries (LIBs) have continually been of great research interest amplified by the exponentially growing demand for electric vehicles.[1] Among the investigated systems, nickel-rich transition metal oxides appear very promising owing to their high specific capacity,[2] and low cobalt content, according to necessity of reducing the cobalt proportion in LIB cathodes due to its severe shortage and strong environmental and ecological concerns.[3] However, the increased nickel content also introduces previously overcome challenges of poor capacity retention and thermal stability due to the vulnerability of the nickel rich oxide towards interfacial side reactions.[4] Herein, a low volatility and non-flammable ionic liquid-based (IL) electrolyte[5] consisting of 0.8Pyr14FSI-0.2LiTFSI is employed to overcome those challenges faced by a Ni-rich LiNi0.8Co0.1Mn0.1O2 positive electrode. The cathode exhibits remarkable electrochemical performance in half-cell configuration, delivering a specific capacity of approximately 200 mAh g-1 and practically no capacity fading after 100 cycles at 0.1C at room temperature. After 600 cycles at 0.5C the cathode has an outstanding capacity retention of 97%, which is substantially higher than with the conventional organic carbonate-based electrolyte used for reference, attributed to a much more stable electrode-electrolyte interfacial layer. Even at elevated temperature (40 °C) the LiNi0.8Co0.1Mn0.1O2 in combination with the IL electrolyte offers a specific capacity of more than 200 mAh g-1 as well as a capacity retention around 99% after 100 cycles at 0.5C. To the best of our knowledge these results exceed the state-of-the-art performance reported for any Ni-rich positive electrode. Reference [1] W. Liu, P. Oh, X. Liu, M. J. Lee, W. Cho, S. Chae, Y. Kim, J. Cho, Angewandte Chemie 2015, 54, 4440.[2] S. H. A. Heist, and S. H. Lee, J . Electrochem . Soc 2019, 166 (6) A873-A879.[3] C.Vaalma, D. Buchholz, M. Weil, S. Passerini, Nature Review Materials 2018, 3, 18013.[4] U.-H. Kim, L.-Y. Kuo, P. Kaghazchi, C. S. Yoon, Y.-K. Sun, ACS Energy Letters 2019, 4, 576.[5] G. A. Elia, U. Ulissi, S. Jeong, S. Passerini, J. Hassoun, Energy & Environmental Science 2016, 9, 3210.

Nano LiFePO4 coated Ni rich composite as cathode for lithium ion batteries with high thermal ability and excellent cycling performance

Ni-rich LiNi0.82Co0.12Mn0.06O2 (denoted as NCM) is successfully coated by LFP nanoparticles (denoted as NCM@LFP) through physical mechanical fusion in industrial level. The 18650 full cells are assembled with NCM@LFP as cathode, which exhibits quite excellent cycling performance and thermal stability. After 500 cycles, NCM@LFP || Graphite full cell still delivers a discharge capacity of 165.3 mA h g−1 (capacity retention with 91.65%) at 1 C in voltage range from 3.0 to 4.2 V at room temperature. Besides, according to Accelerating rate calorimeter (ARC) test, the onset thermal runaway temperature Tc and self-heating interval time Δt of NCM@LFP || Graphite are much higher than that of NCM || Graphite, respectively, indicating an improved security performance of LFP-coated NCM@LFP || Graphite cell.

Al-doped ZnO (AZO) modified LiNi0.8Co0.1Mn0.1O2 and their performance as cathode material for lithium ion batteries

As one of the promising high energy density candidate lithium ion battery cathode materials, Ni-rich LiNi0.8Co0.1Mn0.1O2 (named NCM811) composites suffers from serious structural changes on (de)lithiation, which has a detrimental effect on the cycling stability, thermal stability and storage properties. In this work, Al doped ZnO (named AZO) was employed to modify the NCM811surface particles via simple solid-state reaction method. A suppression to the growth of interfacial impendence due to the positive effect of AZO coating during progressive cycles, which can be confirmed by electrochemical impedance spectroscopy. Good HF scavenging ability, avoiding the active material reduction degradation, was also brought in by the AZO coating. The modified NCM811 with enhanced structural stability, cycling capability and rate performance is a potential candidate for cathode materials of lithium-ion battery.

Effect of calcination time on the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

The layered Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials were synthesized by a solid-state method at different calcination times. The structure, morphological and electrochemical performance of the synthesized materials were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge-discharge tests. The results indicate that the sample prepared at 20h delivers higher rate capacities of 184.8, 182.8, 171.2, 158.3, 142.8, and 116.4 mAh g−1 at rates of 0.1C 0.2C, 0.5C, 1C, 2C, and 5C, respectively. And the sample prepared at 16h exhibits better cycle stability than others.

Enhanced Electrochemical Performance of Ni-Rich Cathode Materials with Li1.3Al0.3Ti1.7(PO4)3 Coating

In this work, a fast ionic conductor, Li1.3Al0.3Ti1.7(PO4)3 (LATP), has been successfully coated on a Ni-rich LiNi0.8Co0.1Mn0.1O2 surface by an improved sol–gel method with postannealing at 575 °C....

Stabilized Behavior of LiNi0.85Co0.10Mn0.05O2 Cathode Materials Induced by Their Treatment with SO2

We present in this paper a modification and stabilization approach for the surface of a high specific capacity Ni-rich cathode material LiNi0.85Co0.10Mn0.05O2 (NCM85) via SO2 gas treatment at 250–4...

The synergism of nanoplates with habit-tuned crystal and substitution of cobalt with titanium in Ni-rich LiNi0.80Co0.15Al0.05O2 cathode for lithium-ion batteries

LiNi0.80Co0.15Al0.05O2 (NCA), as a kind of commercial Ni-rich cathode material, draws significant attention due to its outstanding advantage of high capacity. Here, we synthesize layer LiNi0.80Co0.15-xTixAl0.05O2 (x = 0, 0.03, 0.06, 0.09) nanoplates with {010} electrochemical planes through a facile and versatile approach to improve their cycling life and rate capability. Among all the samples, LiNi0.80Co0.09Ti0.06Al0.05O2 nanoplates (NCA-T2) has the most {010} planes exposure. As cathode for Li-ion batteries, NCA-T2 displays the largest discharge capacity of 190.2 mAh g−1 corresponding to the capacity retention of 92.9% after 100 charge/discharge cycles at 0.1 C between 2.7 and 4.3 V. The capacity retention of NCA-T2 is much larger than 80.8% of the pristine NCA nanoplates with no Ti-substitution (NCA-T0). The Ti-substituted NCA-T2 sample displays the capacity retention of 90.6% at 5 C during 500 charge/discharge cycles. It suggests that the synergism of nanoplates with {010} electrochemical active planes and Ti in the Co sites can stabilize the structure and improve the rate capability. In addition, the density functional theory (DFT) calculation illustrates Ti doping can suppress the structure variation of NCA-T2.