Cathode Material LiNi0 Research Articles

A facile synthesis of cobalt-free nickel-rich ternary cathode material LiNi0.9Fe0.05Al0.05O2 for lithium-ion batteries

To develop high-energy density and inexpensive LIBs, it is exigent to hunt for inexpensive cathode materials with high capacity and operating voltage. Herein, cobalt-free Ni-based ternary material LiNi0.9Fe0.05Al0.05O2 was prepared by a modified rheological phase reaction method. LiNi0.9Fe0.05Al0.05O2 exhibits high discharge capacity of 195 mAh g−1 at 0.1C, better rate capability and cyclability. LiNi0.9Fe0.05Al0.05O2 is competitive among Ni-based cathode materials based on the comprehensive consideration of cost and electrochemical performance.

Achieving Thermodynamic Stability of Single‐Crystal Co‐Free Ni‐Rich Cathode Material for High Voltage Lithium‐Ion Batteries

AbstractNi‐rich layered cathode materials are progressively considered as the standard configuration of high‐energy electric vehicles by virtues of their high capacity and eliminated “range anxiety.” However, the poor cyclic stability and severe cobalt supply crisis would restrain their wide commercial applicability. Here, a cost‐effective single‐crystal Co‐free Ni‐rich cathode material LiNi0.8Mn0.18Fe0.02O2 (NMF), which outperforms widely commercial polycrystalline LiNi0.83Co0.11Mn0.06O2 (MNCM) and single‐crystal LiNi0.83Co0.11Mn0.06O2 (SNCM) is reported. Surprisingly, NMF can compensate for the reversible capacity loss under the designed conditions of high‐temperature and elevated‐voltage, achieving a competitive energy density compared with conventional MNCM or SNCM. Combining operando characterizations and density functional theory calculation, it is revealed that NMF cathode with improved dynamic structure evolution largely alleviates the mechanical strain issue commonly found in Ni‐rich cathode, which can reduce the formation of intragranular cracks and improve the safety performance. Consequently, this new Co‐free NMF cathode can achieve a perfect equilibrium between material cost and electrochemical performance, which not only reduces the production cost by >15%, but also demonstrates excellent thermal stability and cycling performance..

A Fresh One-Step Spray Pyrolysis Approach to Prepare Nickel-Rich Cathode Material for Lithium-Ion Batteries.

The Ni-rich layered cathode material LiNi0.8Co0.1Mn0.1O2 (NCM811) with high specific capacity and acceptable rate performance is one of the key cathode materials for high-energy-density lithium-ion batteries. Coprecipitation, the widely utilized method in the precursor synthesis of NCM811 materials, however, suffers long synthetic processes and challenges in uniform element distribution. The spray pyrolysis method is able to prepare oxide precursors in seconds where all transition-metal elements are well distributed, but the difficulty of lithium distribution will also arise when the lithium salts are added in the subsequent sintering process. Herein, a fresh one-step spray pyrolysis approach is proposed for preparing high-performance NCM811 cathode materials by synthesizing lithium-contained precursors in which all elements are well distributed at a molecular level. The precursors with folded morphology and exceptional uniformity are successfully obtained at a low pyrolysis temperature of 300 °C by an acetate system. Furthermore, the final products commendably inherit the folded morphology of the precursors and exhibit excellent cyclic retentions of 94.6% and 88.8% after 100 and 200 cycles at 1 C (1 C = 200 mA g-1), respectively.

A review on nickel-rich nickel-cobalt-manganese ternary cathode materials LiNi0.6Co0.2Mn0.2O2 for lithium-ion batteries: performance enhancement by modification.

The new energy era has put forward higher requirements for lithium-ion batteries, and the cathode material plays a major role in the determination of electrochemical performance. Due to the advantages of low cost, environmental friendliness, and reversible capacity, high-nickel ternary materials are considered to be one of ideal candidates for power batteries now and in the future. At present, the main design idea of ternary materials is to fully consider the structural stability and safety performance of batteries while maintaining high energy density. Ternary materials currently face problems such as low lithium-ion diffusion rate and irreversible collapse of the structure, although the battery performance can be improved utilizing coating, ion doping, etc., the actual demand requires a more effective modification method based on the intrinsic properties of the material. Based on the summary of the current research status of the ternary material LiNi0.6Co0.2Mn0.2O2 (NCM622), a comparative study of the modification paths of the material was conducted from the level of molecular action mechanism. Finally, the major problems of ternary cathode materials and the future development direction are pointed out to stimulate more innovative insights and facilitate their practical applications.

Li8ZrO6 as a Pre-lithiation Additive for Lithium-Ion Batteries

A major limitation of lithium-ion batteries is that 5–20% of lithium in the cathode is irreversibly lost on the anode surface during the first charge–discharge cycle. This reduces the capacity of the battery for the rest of its operating life. To compensate for the lithium loss, extra lithium can be added to the cathode prior to cell operation, a process called pre-lithiation. Li8ZrO6 (LZO) is lithium-rich with 8 Li+ per formula unit and can potentially provide a large number of lithium ions at relatively low mass loadings to compensate for the irreversible first-cycle capacity loss. LZO was evaluated as a pre-lithiation additive in combination with the cathode material LiNi0.5Mn1.5O4 (LNMO) and assembled in coin cells with graphite as an anode. Two forms of LZO were studied, one synthesized with intrinsic carbon (LZO/C) and one without intrinsic carbon. The fraction of LZO in the composites with LNMO was varied to determine the ratio providing the highest specific capacity per total mass of LNMO and LZO. For the same loading, the LZO additive without intrinsic carbon provided more lithium (5 Li+ per LZO or 550 mA h/g) than LZO/C (4 Li+ per LZO or 440 mA h/g) when charged to 4.8 V versus graphite. A loading of 5 wt % LZO was determined to be the optimal amount, delivering the largest number of Li ions with the smallest mass of the LZO additive, which resulted in 10–11% (on the basis of LNMO–LZO mass) or 15–18% (on the basis of LNMO mass) improved reversible specific capacity and 30% improved capacity retention for 50 charge–discharge cycles. Electrochemical impedance spectroscopy revealed that the combined contact and charge transfer resistance of an LNMO half-cell decreases significantly after prelithiation with LZO.

Mind the miscibility gap: Cation mixing and current density driven non-equilibrium phase transformations in spinel cathode materials

Cathode materials that exhibit phase transitions with large structural rearrangements during electrochemical cycling are generally seen as disadvantageous. Large volume changes and lattice mismatches between intermediate phases tend to lead to significant kinetic barriers, as well as strain and particle cracking. In this regard, solid solution reactions are more desirable as they provide lower energy barriers and no miscibility gap between co-existing phases. The high-voltage cathode material LiNi0.5Mn1.5O4 is an interesting candidate for high power and rate capability applications, however little is known on how its phase transitions occur on the particle level. In the presented work operando X-ray diffraction was utilized together with detailed peak profile analysis to elucidate the phase transition mechanism dependency on transition metal cation order and current density. When fully disordered, the material was found to undergo a bulk single-phase solid solution reaction between the intermediate phases LiNi0.44Mn1.56O4 and Li0.5Ni0.44Mn1.56O4 followed by a first order phase transition with a coherent interphase between the intermediates Li0.5Ni0.44Mn1.56O4 and Ni0.44Mn1.6O4. When fully ordered and slightly less ordered, two separate first order phase transitions with a coherent interphase between the same intermediate phases were observed. On discharge, the fast kinetics of the transition between Li0.5Ni0.44Mn1.56O4 and LiNi0.44Mn1.56O4 resulted in less strain on the former phase. For all samples the miscibility gap between the intermediate phases narrowed with increased current density, suggesting that the solid solution domain formed at the coherent interphase can be extended when the rate of (de)lithiation exceeds the movement speed of the interphase at the phase transition. This effect was found to be larger with increasing cation disorder. The influence of transition metal ordering on the ability to form solid solutions is in good agreement with computational phase diagrams of LiNi0.5Mn1.5O4, showing that disorder is important for promoting and stabilizing solid solutions. These results indicate that the degree of transition metal ordering within the material is of importance for obtaining a material with small lattice mismatches between the involved intermediate phases and for rational design of full solid solution materials.

Realization of a high voltage Ni rich layer LiNi0.5Co0.2Mn0.3O2 single crystalline cathode for LIBs by surface modification

Single crystalline ternary cathode material LiNi0.5Co0.2Mn0.3O2(NCM523) can operate at extremely high voltages and could offer exceptional energy density. The single crystal morphology is less easy to form the cracks and could express better structure stability compared to the polycrystalline counterpart. However, irreversible parasitic side reactions in the interface during cycling may lead to rapid electrochemical degradations. Herein, a simple chemical wet method that modifies the single-crystal NCM523 particles with Al2O3 coating is proposed. The coating layer can effectively suppress the phase transformation and irreversible phase transition on the NCM surface during cycling. Furthermore, the cladding layer can prevent the erosion of by-products such as HF. As a result, the Al2O3 modified NCM523 delivers a high specific capacity of 192.5mAh g−1, excellent cycling stability and rate capability. The capacity retention was 91.7% after 50 cycles even at ultra-high cut-off voltage of 4.7 V. This surface engineering strategy paves the way to promote the development of small size single crystal NCM523 materials for next generation LIBs.

Effect of grain size of single crystalline cathode material of LiNi0.65Co0.07Mn0.28O2 on its electrochemical performance

In this paper, single crystalline cathode materials LiNi0.65Co0.07Mn0.28O2 with different grain size are successfully prepared via controlling the key experimental parameters. Tap density, compact density, specific surface area, X-ray diffraction, scanning electron microscopy and transmission electron microscopy are performed to evaluate the effect of grain size on the physical property and electrochemical performance of single crystalline material. The electrochemical tests reveal excellent rate capability and cycle stability at the cut-off voltage of 4.5 V for the sample with grain size around 3 μm with a capacity retention of 83% while only 40% of initial capacity is retained for the sample in 9 μm. The inferior electrochemical performance of large-sized single crystalline material is attributed to the severe planar gliding, particle cracking and irreversible phase transition. A moderate grain size between 3 and 5 μm can achieve desirable physical property and electrochemical performance.

Enhanced high-voltage robustness of ultra-high nickel cathodes by constructing lithium-ion conductor buffer layer for highly stable lithium-ion batteries

Ultra-high nickel layered oxide cathode materials, of much interest due to their higher energy density and price advantages, have become one of the key development directions of cathode materials for lithium-ion batteries. However, a critical challenge for commercial applications is the rapid capacity fading and severe structural degradation, especially at the high cut-off voltage, which originates from interfacial instability and irreversible phase transition. Here we designed a protective Li3PO4 buffer layer modified ultra-high nickel cathode materials LiNi0.92Co0.04Mn0.04O2 (denoted as NCM9) to dramatically improve high-voltage robustness and structural stability through a mild synchronous lithium strategy. Our results affirmed that the Li3PO4 buffer layer plays an undeniable role in suppressing the capacity and structural degradation, and found that it effectively alleviates the irreversibility of the H2-H3 phase transition of the ultra-high nickel cathode material and enhances mechanical and interfacial stability. Additionally, the main exothermic peak temperature of the modified sample at 256.86 °C was higher than that of the pristine sample at 236.86 °C, which fully confirms the significant improvement of the thermal stability of the modified sample. This work provides additional insights into the complex mechanism of high-voltage robustness and improved structural stability of ultra-high nickel cathodes at high cut-off voltage.

Production of nickel-rich LiNi0.89Co0.08Al0.03O2 cathode material for high capacity NCA/graphite secondary battery fabrication

Abstract Li-ion secondary battery is highly recommended as a power source to highly advanced battery electric vehicles. Among various types, the lithium nickel cobalt aluminum oxide (NCA) battery is considered suitable for high energy and power application. In this study, the NCA cathode material LiNi0.89Co0.08Al0.03O2 was produced via the oxalate co-precipitation technique to reduce the overall production cost and process complexity. Oxalic acid and a small amount of sodium hydroxide were used as the precipitant and pH regulator, respectively. Homogenous and loose metal oxalate precipitate formation was confirmed by X-ray diffraction (XRD), scanning electron microscopy, and Fourier-transform infrared spectroscopy analysis. XRD patterns of the as-obtained micron-sized NCA showed a well-layered hexagonal structure. The electrochemical properties of the cathode in the full cell were thoroughly examined. The specific discharge capacity of the as-obtained NCA in NCA/LiPF6/graphite at a current rate of 20 mA/g was 142 mAh/g. The as-prepared NCA sample had capacity retention of 80% after being charged and discharged at 0.1 A/g for 101 cycles. Scaling up of NCA production process to 2 kg per batch was conducted and evaluation of NCA product quality was performed by material characterization. Based on the overall results and considering the overall process, such an approach is expected to be developed and improved for future large-scale production purposes.

Nanoscale Compositional Mapping of Commercial LiNi0.8Co0.15Al0.05O2 Cathodes Using Atom Probe Tomography

Nickel-rich cathodes provide improved specific capacity, which leads to higher gravimetric energy density, which, in turn, is critical for electric vehicles. However, poor long-term capacity retention at elevated temperatures/high C rates (the rate of charge and discharge on a battery) stems from material issues: surface phase changes, corrosive side reactions with the electrolyte, ion dissolution, and propagation of cracks. Introducing dopants, developing nanoscale surface coatings, and graded core–shell structures all improved the electrochemical performance of nickel-rich cathodes. However, material-level understanding of the effect of Li composition and distribution in Ni-rich cathodes is limited due to a lack of characterization methods available that can directly image Li at the nanoscale. Hence, it is critical to establish methods such as atom probe tomography (APT) that have both nanometer-scale spatial resolution and high compositional sensitivity to quantitatively analyze battery cathodes. To fully realize its potential as a method for quantitative compositional analysis of commercial Li-ion batteries, we provide a comprehensive description of the challenges in sample preparation and analyze the dependency of the analysis parameters, specifically laser pulse energy on the measured stoichiometry of elements in a high-Ni-content cathode material LiNi0.8Co0.15Al0.05O2 (NCA). Our findings show that the stoichiometry variations cannot be explained by charge–state ratios or Ga implantation damage alone during FIB preparation, indicating that additional factors such as crystallographic orientation may need to be considered to achieve quantitative nanoscale compositional analysis of such battery cathodes using APT.

(Invited, Digital Presentation) Phase Interactions and Degradation in Battery Composite Electrodes

The composite electrodes of lithium-ion and sodium-ion batteries must balance complex interactions between the many physical phenomena that underpin battery operation. Active materials host electroactive species. Porous regions support the movement of ions, and secondary phases containing binders and conductive additives provide a supporting electron conducting matrix. Cycling and aggressive operating conditions drive changes in these phases and the balance between them. The alteration of these electrode phases manifests in declining performance and ultimately battery failure. Here, we present an overview of research on degradation processes observed in a diverse set of battery materials using X-ray imaging methods—nanotomography, microtomography, and X-ray absorption near edge structure (XANES) imaging—complemented by electrochemical experiments and other materials characterization methods.Metallic anodes offer a high-capacity alternative to carbon-based anodes for lithium-ion and sodium-ion batteries. Among these metallic anodes tin-based active materials present high-capacity and electrochemical activity in both lithium and sodium chemistries. However, high capacity comes at the price of excessive volume expansion and attendant performance degradation. Studies of Cu6Sn5 alloy anodes in lithium-ion batteries performed using X-ray tomography and nanoscale 2D XANES reveal material volume expansion, fracture, and dissolution as key failure mechanisms within the active material. However, the expansion and contraction of the metallic active material during cycling also leads to significant changes in the supporting carbon-binder domains of the electrodes. Such changes are also observed in the cycling of tin-based composite anodes in both lithium-ion and sodium-ion applications. Active material pulverization of tin due to lithiation and sodiation processes is evident in phase size distributions observed with X-ray microtomography. These changes are accompanied by alteration of the supporting carbon-binder regions.Low cobalt layered oxide cathode materials for lithium-ion batteries present an opportunity for maintaining desirable theoretical capacities while removing cobalt, a metal that presents significant humanitarian issues within its supply chain. However, removal of cobalt from these layered oxide systems removes its stabilizing influence on the electrode structure, especially when cycling at voltages above 4.0 V vs. Li/Li+. Degradation of the low cobalt cathode material Li(Ni0.8Mn0.1Co0.1)O2 has been assessed under different cut-off voltage and operating temperatures using a suite of electrochemical and materials characterization techniques. Higher cycling temperature was found to accelerate degradation mechanisms within the active material, specifically rock-salt phase formation and active material dissolution. Elevated temperature was found to cause significant changes in the supporting carbon-binder domains as well. These changes in both the active material and supporting phases manifest in degradation of electrochemical performance with respect to lost capacity and altered electrode impedances.Taken together, the above studies provide a picture of battery degradation that is driven by anticipated changes in the active material and more nuanced variations that occur in the supporting phases. These observations motivate holistic approaches for the analysis and design of battery electrodes that fit their status as heterogeneous functional materials.

Enhancing Cellulose‐Based Separator with Polyethyleneimine and Polyvinylidene Fluoride‐Hexafluoropropylene Interpenetrated 3D Network for Lithium Metal Batteries

AbstractAside from the electrolyte, a separator is another important component in lithium‐based batteries that has a direct impact on the safety feature and electrochemical performances. To overcome the thermal shrinkage and poor electrolyte affinity of commonly used polyolefin separators, cellulose‐based separators are appealing due to their abundant polar functional groups, thermal stability, and environmental friendliness, especially for large‐sized and high‐energy‐density batteries. Herein, a porous three‐dimensional (3D) network of polymer cellulose‐based separator (denoted as PIC) modified with polyethyleneimine (PEI) and polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) was prepared using a non‐solvent induced phase separation approach. The lithium metal batteries consisting of a PIC separator can deliver a specific capacity of up to 114 mAh g−1 even at a high C‐rate of 8 C (1.36 A g−1) after 300 cycles. Such superior performances of the lithium metal batteries can be attributed to the good wetting ability (390 % electrolyte absorption) and high ionic conductivity (0.754 mS cm−1) of the as‐prepared PIC separator. More importantly, the introduction of polyethyleneimine as a cross‐linking agent significantly improves the mechanical strength of the separator, promotes the uniform deposition of lithium, and compatibility with high voltage (4.4 V) cathode materials LiNi0.8Mn0.1Co0.1O2. This work demonstrates a new strategy for the separator design for high‐performance lithium metal battery applications.

Bifunctional coating layer on Ni-rich cathode materials to enhance electrochemical performance and thermal stability in lithium-ion batteries

In this study we use N,N′-bismaleimide-4,4′-diphenylmethane (BMI), trithiocyanuric acid (TCA), and Jeffamine®-M1000 (molar ratio: 2:1:1; BTJ211) as a novel hybrid oligomer additive and surface modifier for coating (at concentrations of ca. 0.5–2 wt.%) of the cathode material LiNi0.80Co0.15Al0.05O2 (NCA) for lithium-ion batteries (LIBs). Qualitative analysis (1H NMR spectroscopy) confirms the polymerization of the BTJ additive. Morphological analyses (scanning electron microscopy/energy dispersive spectroscopy and high-resolution transmission electron microscopy) reveal that the hybrid oligomer is coated uniformly on the surface of the NCA, forming a BTJ@NCA powder material. Coin-type cells incorporating the 1 wt% BTJ@NCA electrode exhibit a significantly improved capacity retention (CR%) of 80.3%, relative to that of the bare NCA electrode (62.1%), at 1 C for 100 cycles at an upper voltage of 4.5 V. Electrochemical impedance spectroscopy and cyclic voltammetry reveal that this superior electrochemical performance originated from a lower charge transfer resistance (678.3 Ω vs. 349.6 Ω), improving Li+ ion diffusivity, and a lower polarization potential (242.9 mV vs. 368.9 mV). Furthermore, operando microcalorimetry of the cells containing the BTJ@NCA electrodes reveals that the modified electrodes can effectively decrease heat release by 69.6% when charging.

Synthesis and Electrochemical Characterization of LiNi0.5Co0.2Mn0.3O2 Cathode Material by Solid-Phase Reaction.

In this paper, using four carbonates as raw materials, the cathode material LiNi0.5Co0.2Mn0.3O2 was prepared with the “ball milling-calcining” solid-phase synthesis method. The specific reaction process, which consists of the decomposition of the raw materials and the generation of target products, was investigated thoroughly using the TG-DSC technique. XRD, SEM and charge/discharge test methods were utilized to explore the influence of different sintering temperatures on the structure, morphology and electrochemical performance of the LiNi0.5Co0.2Mn0.3O2 cathode. The results show that 900~1000 °C is the appropriate synthesis temperature range. LiNi0.5Co0.2Mn0.3O2 synthesized at 1000 °C delivers optimal cycling stability at 0.5 C. Meanwhile, its initial discharge specific capacity and coulomb efficiency reached 167.2 mAh g−1 and 97.89%, respectively. In addition, the high-rate performance of the cathode sample prepared at 900 °C is particularly noteworthy. Cycling at 0.5 C, 1 C, 1.5 C and 2 C, the corresponding discharge specific capacity of the sample exhibited 148.1 mAh g−1, 143.1 mAh g−1, 140 mAh g−1 and 138.9 mAh g−1, respectively.

Storage degradation mechanism of layered Ni-rich oxide cathode material LiNi0.8Co0.1Mn0.1O2

With advantages such as high specific capacity and low cost, Ni-rich layered oxides are considered to be ideal cathode materials for power batteries. However, due to the high sensitivity of materials to air, structural degradation occurs during transportation and storage, resulting in the formation of an impurity layer. The degradation of the structure will weaken the comprehensive properties of Ni-rich cathode materials. The impurity layer will bring difficulties to the subsequent electrode manufacturing process, which seriously limits the practical application of Ni-rich materials. Therefore, it is particularly important to explore the storage decline mechanism of Ni-rich materials. Herein, the decay mechanism of structure and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 materials after storage at room temperature and high humidity and high-temperature and humidity were studied. It is found that the instability of Ni3+ leads to the appearance of NiO rock salt phase on the surface of the material, accompanied by the formation of reactive oxygen species. Lithium and reactive oxygen species in the material react with H2O and CO2 in the air to form surface residual lithium compounds. The formation of the inert NiO layer and residual lithium compounds hinders the diffusion kinetics of Li+, resulting in serious capacity loss. During the high-temperature storage process, the material forms thicker residual lithium compounds, which aggravates the decay process. After 28 days of high-temperature storage, a residual lithium compound layer of about 7 nm thickness was formed, which seriously hindered the transmission of Li+. This study is helpful to deeply understand the storage failure behavior of Ni-rich cathode materials and promote the large-scale industrial production and application of Ni-rich cathode materials.

Multi-Role Surface Modification of Single-Crystalline Nickel-Rich Lithium Nickel Cobalt Manganese Oxides Cathodes with WO3 to Improve Performance for Lithium-Ion Batteries

Compared with the polycrystalline system, the single-crystalline ternary cathode material has better cycle stability because the only primary particles without grain boundaries effectively alleviate the formation of micro/nanocracks and retain better structural integrity. Therefore, it has received extensive research attention. There is no consistent result whether tungsten oxide acts as doping and/or coating from the surface modification of the polycrystalline system. Meanwhile, there is no report on the surface modification of the single-crystalline system by tungsten oxide. In this paper, multirole surface modification of single-crystalline nickel-rich ternary cathode material LiNi0.6Co0.2Mn0.2O2 by WO3 is studied by a simple method of adding WO3 followed by calcination. The results show that with the change in the amount of WO3 added, single-crystalline nickel-rich ternary cathode material can be separately doped, separately coated, and both doped and coated. Either doping or coating effectively enhances the structural stability, reduces the polarization of the material, and improves the lithium-ion diffusion kinetics, thus improving the cycle stability and rate performance of the battery. Interestingly, both doping and coating (for SC-NCM622-0.5%WO3) do not show a more excellent synergistic effect, while the single coating (for SC-NCM622-1.0%WO3) after eliminating the rock-salt phase layer performs the most excellent modification effect.

Accelerated synthesis of Li(Ni0.8Co0.1Mn0.1)O2 cathode materials using flame-assisted spray pyrolysis and additives

Nickel-rich cathode materials are promising in lithium-ion battery applications because of their high energy density and low material cost. Unfortunately, reducing the synthesis cost of nickel-rich cathode materials is challenging because of the time-consuming and energy-intensive calcination. Therefore, the current work aims to explore strategies for significantly reducing the calcination time of nickel-rich cathode material Li(Ni0.8Co0.1Mn0.1)O2 (NCM811). We used a flame-assisted spray pyrolysis method to synthesize samples with and without using low-cost urea as an additive. Both in situ thermal X-ray diffraction (XRD) and ex situ XRD revealed that urea addition weakened the sensitivity of crystallization and cation mixing to calcination conditions. As a result, with only 20 min of calcination at 875 °C and without any preheating and ramping steps, the NCM811 sample showed an ordered layered structure and comparable electrochemical performance to those with long-time calcination. Moreover, the current work demonstrated that the shortened post calcination was benefited from lithium-embedded particles that likely improved the uniformity of lithium distribution in as-synthesized powder. Therefore, carefully designing initial lithium distribution in particles prior to calcination could also be a useful strategy for other synthesis methods to shorten high-temperature calcination steps, leading to significant reductions in energy consumption and fabrication cost.

Investigation on the structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 modified with Sn

Ni-rich layered cathode materials are promising cathode materials for lithium-ion batteries with high energy density. To reveal the influence of Sn-coating and doping on the structure and electrochemical performances of Ni-rich layered cathode materials, LiNi0.8Co0.1Mn0.1O2, LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) are designed and synthesized. The effect of lithium-tin-oxide coating and Sn-doping on the structural and electrochemical behavior of Ni-rich cathode material are compared and investigated. Compared with the bare LiNi0.8Co0.1Mn0.1O2 cathode material, both LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and Sn-doped LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) samples exhibit better electrochemical performances. The capacity retention for Li2SnO3-coated and Sn-doped materials after 270 cycles at 0.5C can reach as high as 93.7 and 96.6%, respectively. Besides, improved rate capabilities and thermal stability are also obtained for Li2SnO3-coated and Sn-doped materials. The superior electrochemical performances and enhanced thermal stability of Li2SnO3 coated samples are mainly ascribed to the higher interfacial stability and those of Sn-doped materials may be mainly due to higher structural stability and lower polarization than those of the bare LiNi0.8Co0.1Mn0.1O2 cathode material. These results indicate that the introduction of Sn ions, especially Sn doping, may be an effective strategy to improve the performance of Ni-rich layered cathode materials.

Improvement of cycle performance of the high nickel cathode material LiNi0.88Co0.07Al0.05O2 for lithium-ion batteries by the spray drying of V2O5

LiNixCoyAl1−x-yO2 (NCA), as high nickel cathode material, has a high capacity and is one of the most promising cathode materials for lithium-ion batteries. However, the disadvantages such as more residual lithium compounds and serious capacity decay have hindered the industrial application of this material. In order to reduce the residual lithium compound on the surface of the material and restrain the capacity degradation, we designed and prepared a high nickel cathode material by pretreatment washing and subsequent spray drying, which has high cycle life and high discharge specific capacity. Compared to the first discharge specific capacity of 196.6 mAh g−1(0.2 C) for the raw material and 131.4 mAh g−1 after 100 cycles of 1 C, the discharge specific capacity of the modified sample 2V2O5@NCA was increased to 210.4 and 163.8 mAh g−1, respectively. Microstructure observation revealed that V2O5 not only uniformly covers the surface of the secondary particles, but also the presence of electrochemically active LiV3O8, which avoids the direct contact between the active material and electrolyte, thus significantly suppressing the interfacial side reactions between the cathode material and electrolyte and improving the structural stability of the material. Our exploration may pave a way for developing high cycle stability of high nickel cathode materials.