Electrochemical Performance Of LiNi0 Research Articles

Impact of synergistic interfacial modification on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials

Developing sophisticated lithium-ion batteries with high energy and power density requires using high-voltage positive electrodes. Due to its three-dimensional lithium-ion diffusion and greater nominal operating voltage, spinel LiNi0.5Mn1.5O4 has emerged as one of lithium-ion batteries' most viable cathode materials. Electrolyte breakdown, Mn dissolution, and rapid cathode-electrolyte interface (CEI) degradation in lithium-ion cells are exacerbated by the high operating voltage of LNMO. Consequently, the long-term cycling of LNMO is hampered by such adverse side effects, making the commercialization of such a battery impractical. Here, we document the enhancement in the electrochemical performance of LNMO by surface modification utilizing a combination of Al2O3 coating and Graphene enveloping employing a facile wet synthesis technique. The presence of highly crystalline spherical secondary microspheres consisting of primary nanoparticles of disordered LiNi0.5Mn1.5O4, the surface modification with Al2O3, and the subsequent graphene wrapping were all confirmed by structural and surface analysis techniques. The fabricated cells containing the enhanced cathode material (LNMO-Al-GO) were cycled at a C/10 rate for 100 cycles in a voltage window of 3.5–4.9 V, providing a specific discharge capacity of 134.7 ± 3.8 mAhg−1. Delivering a capacity retention of 97.7 ± 3.9% compared to the unmodified LNMO sample (84.7 ± 5.3%). Ex-situ XRD, Electrochemical Impedance Spectroscopy (EIS), and Differential Scanning Calorimetry (DSC) investigations reveal that the alumina coating protects the cathode by acting as a hydrogen fluoride (H.F.) scavenger and minimizes unfavorable phase formations at the CEI, inhibiting Mn3+ dissolution and enhancing cyclability.

The intricate roles of Al2O3 on the structure and electrochemical performances of LiNi0.5Co0.2Mn0.3O2 cathode materials

Severe capacity fading of in NCM layered oxide cathode materials has hampered their practical adoption. This problem can be effectively alleviated by the introduction of Al3+. Previous studies have shown that when Al3+ is introduced into the lattice to partially replace the transition metals, it acts as a structural stabilizer and inter-Al3+ does not participate in the redox reactions. However, the reaction of an aluminum source with lithium salts has not attracted enough attention in the synthesis of Al3+doped cathode materials. In this paper, Al2O3-modified LiNi0.5Co0.2Mn0.3O2 cathode materials are revisited by the solid-state reaction methods. Combined with XRD results, SEM and mapping analysis, it is found that during the heattreatment process, a part of Al3+ ions are doped into the lattice of the cathode material, and it is proved that most parts of Al2O3 react with LiOH⋅H2O to form α-LiAlO2, which is coated on the surface of the cathode material. Considering that lithium will be consumed because of the reaction between Al2O3 and LiOH⋅H2O, we systematically adjusted the lithium amount. It is found that because LiOH reacts preferentially with Al2O3, the amount of lithium reacting with the Ni0.5Co0.2Mn0.3(OH)2 precursor is reduced, which will reduce the electrochemical performance of the cathode material. The deterioration of the electrochemical properties of LiNi0.5Co0.2Mn0.3O2 cathode materials with insufficient lithium is mainly due to the transition of the material structure from a layered structure to a spinel structure. Moreover, the lithium supplemented samples show higher initial charge and discharge capacities, rate capabilities and cycling performances than the lithium un-supplemented samples.

Doping-Induced Surface and Grain Boundary Effects in Ni-Rich Layered Cathode Materials.

In this work, the effects of dopant size and oxidation state on the structure and electrochemical performance of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) are investigated. It is shown that doping with boron (B) which has a small ionic radius and an oxidation state of 3+, leads to the formation of a boron oxide-containing surface coating (probably Li3 BO3 ), mainly on the outer surface of the secondary particles. Due to this effect, boron only slightly affects the size of the primary particle and the initial capacity, but significantly improves the capacity retention. On the other hand, the dopant ruthenium (Ru) with a larger ionic radius and a higher oxidation state of 5+ can be stabilized within the secondary particles and does not experience a segregation to the outer agglomerate surface. However, the Ru dopant preferentially occupies incoherent grain boundary sites, resulting in smaller primary particle size and initial capacity than for the B-doped and pristine NCM811. This work demonstrates that a small percentage of dopant (2mol%) cannot significantly affect bulk properties, but it can strongly influence the surface and/or grain boundary properties of microstructure and thus the overall performance of cathode materials.

Converting commercial MnO2 into Co-doped LiNi0.5Mn1.5O4 with adjustable disordered/ordered phase ratio by a quaternary molten salt

The electrochemical performances of LiNi0.5Mn1.5O4 (LNMO) materials are strongly correlated with the ratio of disordered to ordered phases. Nevertheless, there are few reports on the adjustment of ordered and disordered phase ratio. In this paper, the ratio of ordered to disordered phases in LNMO is successfully adjusted by using a quaternary molten salt, which is proven by XRD refinement, FT-IR, and XPS. Reductive quaternary molten salt and Co doping are favorable for Ni/Mn cation disorder, leading to the increased disordered phase. LNMO with an appropriate ratio of ordered to disordered phases can exhibit enhanced electronic/ionic transfer rate and structural stability, revealed by electrochemical tests and ex situ characterizations. Therefore, the optimized material delivers a reversible capacity of 121 mA h g−1 at 20 mA g−1 and a long cyclic life with 61 mA h g−1 at 1000 mA g−1 over 1200 cycles. The present work offers a new idea for achieving a regulated ratio of ordered to disordered phases in LNMO.

Irreparable Interphase Chemistry Degradation Induced by Temperature Pulse in Lithium-Ion Batteries.

While it is widely recognized that the operating temperature significantly affects the energy density and cycle life of lithium-ion batteries, the consequence of electrode-electrolyte interphase chemistry to sudden environmental temperature changes remains inadequately understood. Here, we systematically investigate the effects of a temperature pulse (T pulse) on the electrochemical performance of LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) pouch full cells. By utilizing advanced characterization tools, such as time-of-flight secondary-ion mass spectrometry, we reveal that the T pulse can lead to an irreversible degradation of cathode-electrolyte interphase chemistry and architecture. Despite negligible immediate impacts on the solid-electrolyte interphase (SEI) on graphite anode, aggregated cathode-to-anode chemical crossover gradually degrades the SEI by catalyzing electrolyte reduction decomposition and inducing metallic dead Li formation because of insufficient cathode passivation after the T pulse. Consequently, pouch cells subjected to the T pulse show an inferior cycle stability to those free of the T pulse. This work unveils the effects of sudden temperature changes on the interphase chemistry and cell performance, emphasizing the importance of a proper temperature management in assessing performance.

Irreparable Interphase Chemistry Degradation Induced by Temperature Pulse in Lithium‐Ion Batteries

AbstractWhile it is widely recognized that the operating temperature significantly affects the energy density and cycle life of lithium‐ion batteries, the consequence of electrode‐electrolyte interphase chemistry to sudden environmental temperature changes remains inadequately understood. Here, we systematically investigate the effects of a temperature pulse (T pulse) on the electrochemical performance of LiNi0.8Mn0.1Co0.1O2 (NMC811) pouch full cells. By utilizing advanced characterization tools, such as time‐of‐flight secondary‐ion mass spectrometry, we reveal that the T pulse can lead to an irreversible degradation of cathode‐electrolyte interphase chemistry and architecture. Despite negligible immediate impacts on the solid‐electrolyte interphase (SEI) on graphite anode, aggregated cathode‐to‐anode chemical crossover gradually degrades the SEI by catalyzing electrolyte reduction decomposition and inducing metallic dead Li formation because of insufficient cathode passivation after the T pulse. Consequently, pouch cells subjected to the T pulse show an inferior cycle stability to those free of the T pulse. This work unveils the effects of sudden temperature changes on the interphase chemistry and cell performance, emphasizing the importance of a proper temperature management in assessing performance.

Metal–organic framework coating layer with inherent self-reactivity toward lithium ions to enhance both structural stability and electrochemical performance of LiNi0.9Co0.085Mn0.015O2 cathodes

Layered cathode materials present challenges, including crack formation, cation mixing, and unfavorable side reactions with electrolytes, which limits rate and cycling performance. This study developed a lithium-intercalated metal–organic framework (i–MOF) with self-reactivity for Li+ to coat high-Ni cathodes. The 2D-packed structure enables free movement of Li+ on i-MOF and redox reactions between Li+ and carboxylate anions, facilitating rapid intercalation/deintercalation of Li+ into the Li layer of the cathode. The i-MOF layer reduces transition metal dissolution, prevents unfavorable side reactions, provides robust protection against corrosion, and enhances cathode properties such as redox reactions with Li+; high thermal stability (≤600 ℃); rapid Li+ diffusion at the cathode–electrolyte interface; protection against volume expansion and phase transition; and suppression of cathode–electrolyte side reactions. Consequently, i–MOF-coated LiNi0.9Co0.085Mn0.015O2 (i-NCM) exhibited improved electrochemical performance, enhanced structural stability, and minimal phase change. The i-NCM exhibited a higher initial discharge capacity (219.70 mAh g−1) than NCM (206.68 mAh g−1 at 0.1C) and superior cycling stability (144.72 and 106.92 mAh g−1 with 71.10 % and 46.84 % cycle retention after 100 cycles at 25 and 50 ℃, respectively). This study demonstrates the potential of i-MOFs as cathode coating materials for Li-ion batteries.

Regulation on electrochemical performance of LiNi0.5Mn1.5O4 cathode material via lithium silicate coating with different Li/Si ratio

Surface coating is regarded as an effective means to alleviate the rapid capacity fading of LiNi0.5Mn1.5O4 material. Lithium silicate, as an ideal coating material, combines the advantages of high ionic conductivity, chemical inertness, and HF capture. Considering the influence of Li/Si ratios on Li+ ions diffusion in lithium silicate, the effects of different Li/Si lithium silicate coatings on the structural and electrochemical performance of LiNi0.5Mn1.5O4 material are investigated. The results show that lithium silicate coatings increase the cation disordering degree, improve the crystallinity, stabilize the electrode/electrolyte interface, and improve Li+ diffusion kinetics. Li/Si ratio greatly affects the composition of lithium silicate coating, which changes from Li2Si2O5 + Li2SiO3 (1:1), Li2Si2O5 + Li4SiO4 (2:1, 3:1) to pure Li4SiO4 phase (4:1). First principles calculation manifests that Li+ migration energy barriers decrease with the increase of Li/Si ratio in lithium silicate. At Li/Si = 4:1, the coated sample shows the best electrochemical performance, with specific discharge capacity of 126.7 mAh g−1 at 10 C rate and capacity retention rate of 91.25% after 200 cycles at 1 C rate. The composition of lithium silicate coating can be controlled by changing Li/Si ratio, which in turn regulates the electrochemical performance of LiNi0.5Mn1.5O4 material.

Effect of sodium and yttrium co-doping on electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathode material for Li-ion batteries: Computational and experimental investigation

LiNi0.8Co0.15Al0.05O2 (NCA) has attracted a lot of attention owing to its high voltage, specific energy density, and specific capacity. However, the cycle durability of the NCA material is still a challenge. Oxygen evolution, migration of nickel cations to the lithium layers (cation mixing), and the destruction of the layered structure of NCA are the most important reasons for thermal and structural instability, reducing capacity, and increasing impedance. Doping is one of the most effective ways to improve the thermal and structural stability of the NCA. In this study, the addition of sodium (Na) on Li-site and yttrium (Y) on metal-site, as well as the simultaneous addition of these elements to NCA material, were investigated experimentally and theoretically. For the first time, we proposed a framework for parameterization of the structural and thermal stability of NCA during the lithiation/delithiation process in terms of first-principle density functional theory (DFT) calculations. It is shown that variation in the Bulk modulus can reflect structural responses, and the calculated Bader charge on oxygen atoms is directly connected to thermal stability concerns. The computational results confirmed the positive effect of Na+ and Y3+ on the structural and thermal stability of the NCA cathode systematically. Following those outcomes, different percentages of the dopants were added to the cathode material experimentally, and electrochemical tests such as cyclability, electrochemical impedance spectroscopy, cyclic voltammetry, and rate capability were performed. The electrochemical tests revealed that in single-doped samples, the optimal amount of Na+ and Y3+ was 0.5 % (mol%), and in co-doped samples, 0.5 % of each dopant (0.5Na-0.5Y-NCA) produced the best results. The optimal 0.5Na-0.5Y-NCA sample retained 92.34 % of its capacity after 100 charge and discharge cycles at a rate of 0.5C, compared to 67.11 % for the pristine NCA. The cooperative addition of sodium and yttrium with different mechanisms such as reducing released oxygen, reducing the formation of insulating compounds, increasing the diffusion coefficient, reducing charge transfer resistance, and improving structural and thermal stability demonstrated synergistic effects on stabilizing the layered structure and improving cycling performance. The underlying mechanisms of observed experimental improvements were interpreted and discussed according to computational outcomes.

Effect of Tempering Temperature on the Structure, Morphology and Electrochemical Performance of LiNi0.5Mn1.5O4

LiNi0.5Mn1.5O4, the cathode material for 5V lithium ion batteries, was synthesized through the coprecipitation-combustion process in air. The effect of tempering temperature on the structure, morphology and electrochemical performances were investigated. The phase and electrochemical properties of the samples were characterized by powder X-ray diffraction, scanning electron microscopy and constant current charge-discharge tests. The experimental results indicate that the samples tempered at 800°C-900°C all have spinel structure, with the increase of tempering temperature, the crystallinity and grain size of the sample increase.The sample tempering at 850°C has well-developed crystals, moderate crystal size and the best electrochemical performance.

Current collectors’ effects on the electrochemical performance of LiNi0·6Co0·2Mn0·2O2 suspension electrodes for lithium slurry battery

Take after the advantages of lithium-ion battery (LIB) and redox flow battery (RFB), semi-solid flow battery (SSFB) is a promising electrochemical energy storage device in renewable energy utilization. The flowable slurry electrode realizes decouple of energy and power density, while it also brings about new challenge to SSFBs, electron transport between active material and the out circuit. In this consideration, three types of current collectors (CCs) are applied to study the resistance and electrochemical performances of slurry cathodes within pouch cells for the first time. It proves that the electronic resistance (Re) between slurry electrode and the CC plays a decisive role in SSFB operation, and it is so large when Al foil is adopted that the cell cannot even work. Contact angle between Ketjen black (KB) slurry without active material (AM) and the CC is a preliminarily sign for the Re, the smaller the angle, the lower the resistance, and the better electrochemical performance of the cell.

Influence of Al3+ and PO43− co-doping on structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

Influence of Al3+ and PO43− co-doping on structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

Cr3+ and Co2+ doping modification on electrochemical performance of LiNi0.5Mn1.5O4 for Li-ion battery

Cr3+ and Co2+ doping modification on electrochemical performance of LiNi0.5Mn1.5O4 for Li-ion battery

Effect of Fe3+ and/or PO43– Doping on the Electrochemical Performance of LiNi0.5Mn1.5O4 Cathode Material for Li-Ion Batteries

An Fe3+/PO43– codoped LiNi0.5Mn1.4667Fe0.02P0.0133O4 sample has been prepared by a coprecipitation–hydrothermal method followed by two-step calcination. A novel wet chemical route, using FeSO4 rather than Fe2(SO4)3 as the Fe3+ source and NaH2PO4 as the PO43– source, is adopted to obtain uniform codoping of Fe3+ and PO43– ions in a carbonate precursor according to the precipitation–dissolution–transformation mechanism. For comparison, Fe3+-doped and PO43–-doped samples have been also synthesized via the same route. The effects of Fe3+/PO43– codoping and single doping on the crystalline structure, morphology, and electrochemical performance of LiNi0.5Mn1.5O4 are investigated. Compared with pristine and single doped samples, the codoped sample shows better electrochemical performance, with a specific discharge capacity of 125.2 mAh g–1 at 10 C and a capacity retention rate of 85.9% after 200 cycles at 1 C, under the synergy of Fe3+/PO43– codoping, including enhanced crystallinity, decreased Mn3+ content, significantly reduced primary particle size and secondary agglomeration, as well as the appearance of (110) surfaces in truncated octahedral primary particles.

Effect of MoO3 surface coating on electrochemical performances of LiNi0.8Co0.1Mn0.1O2 cathode

In this paper, we synthesize the MoO 3 modified LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode (denoted as M-NCM81) and compare with pristine LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode (denoted as P-NCM81). The M-NCM81 cathode delivers good cation ordering and typical spherical form. The M-NCM81 cathode shows initial discharge capacity of 203.8 mAh g −1 at 0.1 C, capacity retention of 79.8% under the 5.0 C. In addition, the M-NCM81 cathode still retain a discharge capacity of 172.2 mAh g −1after 100 cycles. Such electrochemical performances are significantly improved compared to those of P-NCM81. It can be elucidated that MoO 3 coating layer acts as a HF inhibitor/scavenger. The MoO 3 modification plays an important role in inhibiting severe structural degradation, derived from a harmful side reaction with electrolyte. It effectively suppresses the increase in charge-transfer resistance, leading to superior electrochemical performances.

Exploring the synergistic effect of Li+ and Br− co-doping on improving the microstructural and electrochemical performances of LiNi0.5Mn1.5O4 cathode materials

BackgroundFew studies have reported the effects of cation and anion co-doping in LNMO. MethodsPristine LiNi0.5Mn1.5O4 and Li1+xNi0.5Mn1.5O4-xBrx (0 ≤ x ≤ 0.04, mol%) were synthesized using a facile solid-state ball-milling process. Significant findingsThe structural characterization results suggested that Li+ and Br− co-doping effectively decreased the Mn3+content and LixNi1-xO impurity phases, and enhanced chemical and structural stability by forming stronger MnBr bonds rather than MnO bonds. Electrochemical performance tests indicated that the Li+ and Br− co-doped Li1.02Ni0.5Mn1.5O3.98Br0.02 sample (LNMO-Br0.02) possessed an excellent rate capability. The corresponding discharge capacity at 0.2 C, 0.5 C, 1 C, 2 C, 3 C, 5 C, 7 C, and 10 C were around 134.6, 132.8, 132.0, 127.4, 122.1, 112.9, 102.9, and 82.5 mAh/g, respectively. Under similar conditions, pristine LiNi0.5Mn1.5O4 yielded only 125.7, 124.8, 121.8, 117.0, 111.1, 95.2, 73.0, and 27.6 mAh/g. In addition, LNMO-Br0.02 delivered favorable cycling performance at room temperature (25 °C), and about 95.3% of the initial capacity (120.5 mAh/g) could be obtained after 270 cycles at 3 C. Post-cycling Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses revealed that LNMO-Br0.02 possessed the thinner cathode-electrolyte interphase (CEI) film than the other materials.

Influence of sintering temperatures on microstructure and electrochemical performances of LiNi0.93Co0.04Al0.03O2 cathode for high energy lithium ion batteries

In this study, we present a method for synthesizing Ni-rich LiNi0.93Co0.04Al0.03O2 (NCA) with a high-energy cathode material by the solid-phase method. The sintering temperature plays a very important role in the electrochemical performance of the LiNi0.93Co0.04Al0.03O2 since it affects the crystallinity and structural stability. Therefore, various sintering temperatures (660 °C/690 °C/720 °C/750 °C/780 °C/810 °C) are studied to get optimum electrochemical performances. The electrochemical performance of LiNi0.93Co0.04Al0.03O2 sintered at 720 °C shows the highest discharge capacity of 217.48 mAh g−1 with excellent Coulombic efficiency of 87.84% at 0.1 C. Moreover, the LiNi0.93Co0.04Al0.03O2 sintered at 720 °C exhibits excellent rate-capability (181.1 mAh g−1 at 2.0 C) as well as superior cycle stability (95.4% after 80 cycles at 0.5 C). This is because optimized sintering temperature leads to good structural stability with low cation disorder and residual lithium content.

Effect of Polyacrylonitrile Surface Coating on Electrochemical Performance of LiNi0.8Mn0.1Co0.1O2 in All Solid-State Batteries

Ni rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising cathode materials for high energy all solid-state batteries. However, its poor ionic and electronic conductivity along with high interfacial instability with thiophosphate-based solid electrolytes result in severe capacity loss with cycling. In this paper, a polyacrylonitrile (PAN) coating is applied on the surface of NMC811 followed by a simple heat treatment in air. The PAN coating layer not only helps to improve the electronic conductivity of the cathode composite but also prevents the direct contact of NMC811 active material with the solid electrolyte, reducing the decomposition of the electrolyte and formation of passivating layers with low ionic conductivity. Compared to pristine NMC811, the electrochemical properties of PAN-NMC composites are significantly improved. When cycled at 0.1 C rate, PAN-NMC composite shows an initial capacity of 192.16 mAh g−1 and capacity retention of 68.5% over 100 cycles compared to the lower capacity of 173.06 mAh g−1 and retention 58.68% for the pristine NMC811. These results indicate that the PAN coating greatly improves the conductivity and cycling performance of NMC811.

Three-dimensional networking binders prepared in situ during wet-slurry process for all-solid-state batteries operating under low external pressure

For all-solid-state Li batteries (ASLBs), the external operating pressure offsets the detrimental electrochemo-mechanical effects. In this work, a new scalable in situ protocol to reinforce binders for sulfide-electrolyte-based ASLBs operating under low or no external pressures is reported. The vulcanization of butadiene rubber (BR) using elemental sulfur proceeds in situ during the wet-slurry fabrication process for electrodes, forming a mechanically resilient crosslinked structure. The electrochemical performance of LiNi0.70Co0.15Mn0.15O2 electrodes fabricated using pristine or vulcanized BR diverge significantly as the operating pressure is lowered from 70 MPa to a practically acceptable value of 2 MPa. Complementary analysis using cross-sectional scanning electron microscopy and operando electrochemical pressiometry measurements confirms that the vulcanization of BR suppresses the electrochemo-mechanical degradation of electrodes, which suggests that the scaffolding structure of the vulcanized BR helps maintain the microstructural integrity of the electrodes upon charge and discharge. The significantly enhanced performance of the vulcanized BR is also demonstrated for pouch-type LiNi0.70Co0.15Mn0.15O2/Li4Ti5O12 full cells operated under no external pressure (reversible capacity of 121 vs. 150 mA h g−1 at 0.2C for electrodes with pristine vs. vulcanized BR, respectively).

Stabilization of crystal and interfacial structure of Ni-rich cathode material by vanadium-doping

Stable structure and interface of nickel-rich metal oxides is crucial for practical application of next generation lithium-ion batteries with high energy density. Bulk doping is the promising strategy to improve the structural and interfacial stability of the materials. Herein, we report the impact of vanadium-doping on the structure and electrochemical performance of LiNi0.88Co0.09Al0.03O2 (NCA88). Vanadium doped in high oxidation state (+5) would lead to alteration of the crystal lattice and Li+/Ni2+ cation mixing. Those are the main factors determining the cycling and rate capability of the materials. With optimization of vanadium-doping, the preservation of the integrity of the secondary particles of the materials, the enhancement of the diffusion of Li+ ions, and alleviation of the side reactions of the electrolyte can be efficiently achieved. As a result, NCA88 doped with vanadium of 1.5 mol % can provide superior cycling stability with capacity retention of 84.3% after 250 cycles at 2C, and rate capability with capacity retention of 65.5% at 10C, as compared to the corresponding values of 58.6% and 55% for the pristine counterpart, respectively. The results might be helpful to the selection of dopants in the design of the nickel-rich materials.