Enhancing the Thermal and Upper Voltage Performance of Ni-Rich Cathode Material by a Homogeneous and Facile Coating Method: Spray-Drying Coating with Nano-Al2O3

Dual Modification Strategy for Enhanced Cycling and Rate Performance of Ni-Rich Cathode Materials in Lithium-Ion Batteries

A great challenge in the commercialization process of layered Ni-rich cathode material LiNixCoyMn1-x-yO2 (NCM, x ≥ 80%) for lithium-ion batteries is the surface instability, which is exacerbated by the increase in nickel content. The high surface alkalinity and unavoidable cathode/electrolyte interface side reactions result in significant decrease for the capacity of NCM material. Surface coating and doping are common and effective ways to improve the electrochemical performance of Ni-rich cathode material. In this study, an in situ reaction is induced on the surface of secondary particles of NCM material to construct a stable lithium sulfate coating, while achieving sulfur doping in the near surface region. The synergistic modification of lithium sulfate coating and lattice sulfur doping significantly reduced the content of harmful residual lithium compounds (RLCs) on the surface of NCM material, suppressed the side reactions between the cathode material surface and electrolyte and the degradation of surface structure of the NCM material, effectively improved the rate capability and cycling stability of the NCM material.

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Electrochemical coupling in subnanometer pores/channels for rechargeable batteries

Subnanometer pores/channels (SNPCs) play crucial roles in regulating electrochemical redox reactions for rechargeable batteries. The delicately designed and tailored porous structure of SNPCs not only provides ample space for ion storage but also facilitates efficient ion diffusion within the electrodes in batteries, which can greatly improve the electrochemical performance. However, due to current technological limitations, it is challenging to synthesize and control the quality, storage, and transport of nanopores at the subnanometer scale, as well as to understand the relationship between SNPCs and performances. In this review, we systematically classify and summarize materials with SNPCs from a structural perspective, dividing them into one-dimensional (1D) SNPCs, two-dimensional (2D) SNPCs, and three-dimensional (3D) SNPCs. We also unveil the unique physicochemical properties of SNPCs and analyse electrochemical couplings in SNPCs for rechargeable batteries, including cathodes, anodes, electrolytes, and functional materials. Finally, we discuss the challenges that SNPCs may face in electrochemical reactions in batteries and propose future research directions.

Structural Insight into Protective Alumina Coatings for Layered Li-Ion Cathode Materials by Solid-State NMR Spectroscopy

Layered transition metal oxide cathode materials can exhibit high energy densities in Li-ion batteries, in particular, those with high Ni contents such as LiNiO2. However, the stability of these Ni-rich materials often decreases with increased nickel content, leading to capacity fade and a decrease in the resulting electrochemical performance. Thin alumina coatings have the potential to improve the longevity of LiNiO2 cathodes by providing a protective interface to stabilize the cathode surface. The structures of alumina coatings and the chemistry of the coating-cathode interface are not fully understood and remain the subject of investigation. Greater structural understanding could help to minimize excess coating, maximize conductive pathways, and maintain high capacity and rate capability while improving capacity retention. Here, solid-state nuclear magnetic resonance (NMR) spectroscopy, paired with powder X-ray diffraction and electron microscopy, is used to provide insight into the structures of the Al2O3 coatings on LiNiO2. To do this, we performed a systematic study as a function of coating thickness and used LiCoO2, a diamagnetic model, and the material of interest, LiNiO2. 27Al magic-angle spinning (MAS) NMR spectra acquired for thick 10 wt % coatings on LiCoO2 and LiNiO2 suggest that in both cases, the coatings consist of disordered four- and six-coordinate Al-O environments. However, 27Al MAS NMR spectra acquired for thinner 0.2 wt % coatings on LiCoO2 identify additional phases believed to be LiCo1-xAlxO2 and LiAlO2 at the coating-cathode interface. 6,7Li MAS NMR and T1 measurements suggest that similar mixing takes place near the interface for Al2O3 on LiNiO2. Furthermore, reproducibility studies have been undertaken to investigate the effect of the coating method on the local structure, as well as the role of the substrate.

An effective co-modification strategy to enhance the cycle stability of LiNi0.8Co0.1Mn0.1O2 for lithium-ion batteries

Ni-rich cathode materials suffer from rapid capacity fading caused by interface side reactions and bulk structure degradation. Previous studies show that Co is conducive to bulk structure stability and sulfate can react with the residual lithium (LiOH and Li2CO3) on the surface of Ni-rich cathode materials and form a uniform coating to suppress the side reactions between the cathode and electrolyte. Here, CoSO4 is utilized as a modifier for LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode materials. It reacts with the residual lithium on the surface of the NCM811 cathode to form Li-ion conductive Li2SO4 protective layers and Co doping simultaneously during the high-temperature sintering process, which can suppress the side reactions between the Ni-rich cathode and electrolyte and effectively prevent the structural transformation. As a result, the co-modified NCM811 cathode with 3 wt% CoSO4 exhibits an improved cycling performance of 81.1% capacity retention after 200 cycles at 1C and delivers an excellent rate performance at 5C of 187.4 mA h g-1, which is 10.2% higher than that of the pristine NCM811 cathode.

Review of the Scalable Core-Shell Synthesis Methods: The Improvements of Li-Ion Battery Electrochemistry and Cycling Stability

The demand for lithium-ion batteries has significantly increased due to the increasing adoption of electric vehicles (EVs). However, these batteries have a limited lifespan, which needs to be improved for the long-term use needs of EVs expected to be in service for 20 years or more. In addition, the capacity of lithium-ion batteries is often insufficient for long-range travel, posing challenges for EV drivers. One approach that has gained attention is using core-shell structured cathode and anode materials. That approach can provide several benefits, such as extending the battery lifespan and improving capacity performance. This paper reviews various challenges and solutions by the core-shell strategy adopted for both cathodes and anodes. The highlight is scalable synthesis techniques, including solid phase reactions like the mechanofusion process, ball-milling, and spray-drying process, which are essential for pilot plant production. Due to continuous operation with a high production rate, compatibility with inexpensive precursors, energy and cost savings, and an environmentally friendly approach that can be carried out at atmospheric pressure and ambient temperatures. Future developments in this field may focus on optimizing core-shell materials and synthesis techniques for improved Li-ion battery performance and stability.

Effective and Low-Cost In Situ Surface Engineering Strategy to Enhance the Interface Stability of an Ultrahigh Ni-Rich NCMA Cathode

Ultrahigh Ni-rich quaternary layered oxides LiNi_1-x-y-zCo_xMn_yAl_zO₂ (1 - x - y - z ≥ 0.9) are regarded as some of the most promising cathode candidates for lithium-ion batteries (LIBs) because of their high energy density and low cost. However, poor rate capacity and cycling performance severely limit their further commercial applications. Herein, an in situ coating strategy is developed to construct a uniform LiAlO₂ layer. The NH₄HCO₃ solution is added to a NaAlO₂ solution to form a weak alkaline condition, which can reduce the hydrolysis rate of NaAlO₂, thus enabling uniform deposition of Al(OH)₃ on the surface of a Ni_0.9Co_0.07Mn_0.01Al_0.02(OH)₂ (NCMA) precursor. The LiAlO₂-coated samples show enhanced cycling stability and rate capacity. The capacity retention of NCMA increases from 70.7% to 88.3% after 100 cycles at 1 C with an optimized LiAlO₂ coating amount of 3 wt %. Moreover, the 3 wt % LiAlO₂-coated sample also delivers a better rate capacity of 162 mAh g^-1 at 5 C, while that of an uncoated sample is only 144 mAh g^-1. Such a large improvement of the electrochemical performance should be attributed to the fact that a uniform LiAlO₂ coating relieves harmful interfacial parasitic reactions and stabilizes the interface structure. Therefore, this in situ coating approach is a viable idea for the design of higher-energy-density cathode materials.

Recent progress on the low and high temperature performance of nanoscale engineered Li-ion battery cathode materials

Lithium ion batteries (LIB) are the domain power house that gratifies the growing energy needs of the modern society. Statistical records highlight the future demand of LIB for transportation and other high energy applications. Cathodes play a significant role in enhancement of electrochemical performance of a battery, especially in terms of energy density. Therefore, numerous innovative studies have been reported for the development of new cathode materials as well as improving the performance of existing ones. Literature designate stable cathode-electrolyte interface (CEI) is vital for safe and prolonged high performance of LIBs at different cycling conditions. Considering the context, many groups shed light on stabilizing the CEI with different strategies like surface coating, surface doping and electrolyte modulation. Local temperature variation across the globe is another major factor that influences the application and deployment of LIB chemistries. In this review, we discuss the importance of nano-scale engineering strategies on different class of cathode materials for their improved CEI and hence their low and high temperature performances. Based on the literature reviewed, the best nano-scale engineering strategies investigated for each cathode material have been identified and described. Finally, we discuss the advantages, limitations and future directions for enabling high performance cathode materials for a wide range of applications.

Insights into the Enhanced Structural and Thermal Stabilities of Nb-Substituted Lithium-Rich Layered Oxide Cathodes

Lithium-rich manganese-based layered oxides (LLOs) are considered to be the most promising cathode materials for next-generation lithium-ion batteries (LIBs) for their higher reversible capacity, higher operating voltage, and lower cost compared with those of other commercially available cathode materials. However, irreversible lattice oxygen release and associated severe structural degradation that exacerbate under high temperature and deep delithiation hinder the large-scale application of LLOs. Herein, we propose a strategy to stabilize the layered lattice framework and improve the thermal stability of cobalt-free Li_1.2Mn_0.53Ni_0.27O₂ by doping with 4d transition metal niobium (Nb). Detailed atomic-scale imaging, in situ characterization, and DFT simulations confirm that the induced strong Nb-O bonds stabilize the oxygen lattice framework and restrains the fracture of TM-O bonds, thereby inhibiting the release of lattice oxygen and the continuous migration of TM ions to the lithium layer during the cycle. Furthermore, Nb doping also promotes the surface rearrangement to form a Ni-enrichment layered/rocksalt heterogeneous interface to enhance surface structural stability. As a result, the Nb-doped material delivers a capacity of 181.7 mAh g^-1 with retention of 85.5% after 200 cycles at 1C, extraordinary thermal stability with a capacity retention of 80.7% after 200 cycles at 50 °C, and superior rate capability.

An effective dual-modification strategy to enhance the performance of LiNi0.6Co0.2Mn0.2O2 cathode for Li-ion batteries

Ni-rich ternary layered oxides represent the most promising cathodes for lithium ion batteries (LIBs) due to their relatively large specific capacities and high energy/power densities. Unfortunately, their inherent chemical instability and surface side reactions during the charge/discharge processes lead to rapid capacity fading and poor cycling life, which seriously restrict their practical applications. Herein, we report a simple dual-modification strategy for preparing LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials by Li2SnO3 surface coating and Sn4+ gradient doping. The gradient Sn doping stabilizes the layered structure due to the strong Sn-O covalent bond and relieves the Li+/Ni2+ cation disorder by the partial oxidation of Ni2+ to Ni3+. Besides, the ionic and electronic conductive Li2SnO3 coating serves as a protective layer to eliminate the side reactions with electrolyte/air. In LIB testing, the dual-modified NCM622 cathode with 2% Sn delivers an enhanced cycling performance with 88.31% capacity retention after 100 cycles from 3.0 to 4.5 V at 1C compared to the bare NCM622. Meanwhile, the dual-modified NCM622 shows an improved reversible capacity of 136.2 mA h g-1 at 5C and enhanced electrode kinetics. The dual-modification strategy may enable a new approach to simultaneously relieve the interfacial instability and bulk structure degradation of Ni-rich cathode materials for high energy density LIBs.

NCA, NCM811, and the Route to Ni-Richer Lithium-Ion Batteries

The aim of this article is to examine the progress achieved in the recent years on two advanced cathode materials for EV Li-ion batteries, namely Ni-rich layered oxides LiNi0.8Co0.15Al0.05O2 (NCA) and LiNi0.8Co0.1Mn0.1O2 (NCM811). Both materials have the common layered (two-dimensional) crystal network isostructural with LiCoO2. The performance of these electrode materials are examined, the mitigation of their drawbacks (i.e., antisite defects, microcracks, surface side reactions) are discussed, together with the prospect on a next generation of Li-ion batteries with Co-free Ni-rich Li-ion batteries.

The Effect of Crystalline Microstructure of PVDF Binder on Mechanical and Electrochemical Performance of Lithium-Ion Batteries Cathode

In this paper, the effect of the crystalline microstructures of polyvinylidene fluoride (PVDF), as cathode binder, on mechanical and electrochemical properties of the cathode, and on the cell performance is investigated. The crystalline phases of the PVDF films prepared at different temperatures are determined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) and also mechanical strength of PVDF films evaluated by a tensile test. The cathodes were prepared at altered temperatures to achieve different PVDF phases. The effect of various crystalline phases on the cathode performance was studied. The obtained cathodes were analyzed by scanning electron microscope (SEM), contact angle measurement, and adhesion test. The electrochemical performance of the cathodes was evaluated by charge-discharge cycling test and AC impedance spectroscopy. Mechanical tests results showed that the cathode which is prepared at 60 °C has the best adhesion and mechanical stability. In addition, the charge-discharge cycling studies showed that this cathode has the highest capacity efficiency. AC impedance spectroscopy illustrated that this electrode has the lowest charge transfer resistance and SEI resistance.

Enhanced Cyclability and High-Rate Capability of LiNi0.88Co0.095Mn0.025O2 Cathodes by Homogeneous Al3+ Doping

To suppress capacity fading of nickel-rich materials for lithium-ion batteries, a homogeneous Al³⁺ doping strategy is realized through tailoring the Al³⁺ diffusion path from the bulk surface to interior. Specifically, the layered LiNi_0.88Co_0.095Mn_0.025O₂ cathode with the radial arrangement of primary grains is successfully synthesized through optimization design of precursors. The Al³⁺ follows the radially oriented primary grains into the bulk by introduction of nano-Al₂O₃ during the sintering process, realizing the homogeneous Al³⁺ distribution in the whole material. Particularly, a series of nano-Al₂O₃-modified LiNi_0.88Co_0.095Mn_0.025O₂ are investigated. With the 2% molar weight of Al³⁺ doping, the capacity retention ratio of the cathode is tremendously improved from 52.26 to 91.57% at 1 C rate after 150 cycles. Even at a heavy current density of 5 (&10) C for the LiNi_0.88Co_0.095Mn_0.025O₂-Al_2% cathode, a high reversible capacity of 172.3 (&165.7) mA h g^-1 can be acquired, which amount to the 84.46 (&81.25) % capacity retention at 0.2 C. Moreover, voltage deterioration is significantly suppressed by homogeneous Al³⁺ doping from the results of median voltage and dQ/dV curves. Therefore, homogeneous Al³⁺ doping benefited from the radial arrangement of primary grains provides an effective and practical way to prolong lifespan, as well as improves rate performance and voltage stability of nickel-rich ternary materials.

Enhancing the Electrochemical Performance of LiNi0.4Co0.2Mn0.4O2 by V2O5/LiV3O8 Coating

Despite layered LiNi_xCo_yMn_zO₂ having drawn much attention for their high capacity and high energy density, they still endure strong capacity decay upon prolonged cycling and high C-rates, primarily due to sluggish Li⁺ and charge-transfer kinetics and detrimental parasitic reactions with the electrolyte. To address these issues, application of a surface-coating layer made of V₂O₅/LiV₃O₈ on LiNi_0.4Co_0.2Mn_0.4O₂ (V-NCM) is pursued. Benefiting from the ionic conductivity of LiV₃O₈ and the electronic conductivity of V₂O₅, resulting in both enhanced Li⁺ diffusion and charge-transfer kinetics, the coated material offers significantly improved C-rate capability. Additionally, better long-term cycling performance is achieved mostly due to the mitigated parasitic reactions at the electrode/electrolyte interface that result in lower structural degradation. As a result, Li/V-NCM cells deliver over 100 mA h g^-1 capacity at 10 C and also achieve 86.1% (2 C) and 94.1% (10 C) capacity retention after 200 cycles. These V-NCM cells operate quite stably even at elevated temperature, that is, 40 and 60 °C. The coating strategy herein reported may also be useful to enhance the cycling stability and C-rate capability of other layered cathode materials.

Improving the Electrochemical Performance and Structural Stability of the LiNi0.8Co0.15Al0.05O2 Cathode Material at High-Voltage Charging through Ti Substitution

LiNi_0.8Co_0.15Al_0.05O₂ (NCA) has been proven to be a good cathode material for lithium-ion batteries (LIBs), especially in electric vehicle applications. However, further elevating energy density of NCA is very challenging. Increasing the charging voltage of NCA is an effective method, but its structural instability remains a problem. In this work, we revealed that titanium substitution could improve cycle stability of NCA under high cutoff voltage significantly. Titanium ions with a relatively larger ion radius could modify the oxygen lattice and change the local coordination environment of NCA, leading to decreased cation migration, better kinetic and thermodynamic properties, and improved structural stability. As a result, the Ti-substituted NCA cathode exhibits impressive reversible capacity (198 mA h g^-1 at 0.1C) with considerable cycle stability under a cutoff voltage up to 4.7 V. It is also revealed that Ti could suppress oxygen release in the high-voltage region, benefitting cycle and thermal stabilities. This work provides valuable insight into the design of high-voltage layered cathode materials for high-energy-density LIBs.

Optimized electrochemical performance of Ni rich LiNi0.91Co0.06Mn0.03O2 cathodes for high-energy lithium ion batteries

We report high electrochemical performances of LiNi0.91Co0.06Mn0.03O2 cathode material for high-energy lithium ion batteries. LiNi0.91Co0.06Mn0.03O2 is synthesized at various sintering temperatures (640~740 °C). The sintering temperatures affect crystallinity and structural stability, which play an important role in electrochemical performances of LiNi0.91Co0.06Mn0.03O2. The electrochemical performances are improved with increasing sintering temperature up to an optimal sintering temperature. The LiNi0.91Co0.06Mn0.03O2 sintered at 660 °C shows remarkably excellent performances such as initial discharge capacity of 211.5 mAh/g at 0.1 C, cyclability of 85.3% after 70 cycles at 0.5 C and rate capability of 90.6% at 2 C as compared to 0.5 C. These results validate that LiNi0.91Co0.06Mn0.03O2 sintered at 660 °C can be regarded as a next generation cathode.

Enhancing High-Voltage Performance of Ni-Rich Cathode by Surface Modification of Self-Assembled NASICON Fast Ionic Conductor LiZr2(PO4)3

Coating methodology is commonly employed in the enhancement of Ni-rich cathodes for Li-ion batteries as an efficient approach, while its strategy and effect are still great challenges to achieve success in surface modifications for comprehensive electrochemical properties. In this work, the surface of Ni-rich cathode LiNi_0.82Co_0.15Al_0.03O₂ (NCA) is modified by intimately coating NASICON-type solid electrolyte LiZr₂(PO₄)₃ (LZP) via a facile approach involving electrostatic attraction. With well-designed architecture and a uniform NASICON-type LZP nanolayer wrapping over the NCA microsphere, the entire electrode demonstrates exceptional Li⁺ diffusion and conductivity and suppresses the side reaction between electrolyte and electroactive NCA, stabilizing the phase interface with less Li⁺/Ni²⁺ cation mixing. As a result, the NCA@LZP can deliver a high reversible capacity of 182 mAh g^-1 at 1C in 2.7-4.3 V, maintaining the capacity retention of 84.6% after 100 cycles. More importantly, the structure stability of NCA is enhanced substantially by surface modification of LZP at high cutoff voltage. It achieves a reversible capacity of 204 mAh g^-1 and keeps 100.4 mAh g^-1 after 500 cycles at 1C in the potential range of 2.7-4.5 V. This effective strategy of using NASICON fast ionic conductor like LZP as a coating layer may provide a new insight to modify the surface of Ni-rich electrode, improving the rate capability and cyclic performance under high voltage.

New Chemical Insights into the Beneficial Role of Al2O3 Cathode Coatings in Lithium-ion Cells

Inorganic surface coatings such as Al₂O₃ are commonly applied on positive electrode materials to improve the cycling stability and lifetime of lithium-ion cells. The beneficial effects are typically attributed to the chemical scavenging of corrosive HF and the physical blockage of electrolyte components from reaching the electrode surface. The present work combines published thermochemistry data with new density functional theory calculations to propose a new mechanism of action: the spontaneous reaction of the LiPF₆ electrolyte salt with Al₂O₃-based surface coatings. Using ¹⁹F and ³¹P solution nuclear magnetic resonance spectroscopy, it is demonstrated that the storage of LiPF₆-containing electrolyte solution with Al₂O₃ produces LiPO₂F₂, a well-known electrolyte additive. The production of LiPO₂F₂ is also observed for electrolyte solutions that were stored for 14 days at 40 °C with Al₂O₃-coated LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) and LiNi_0.8Co_0.15Al_0.05O₂ (NCA) materials. Given the beneficial nature of this species for the lifetime and stability of lithium-ion cells, this reaction is here proposed to similarly benefit the performance of cells that use Al₂O₃-coated cathode materials.

Design and Synthesis of Double-Functional Polymer Composite Layer Coating To Enhance the Electrochemical Performance of the Ni-Rich Cathode at the Upper Cutoff Voltage

Graphene has been implemented as a desirable additive to improve the electrochemical performance of Ni-rich cathode materials. However, it is not only hard to ensure the intimate interaction between them in practice, which may affect the surface electronic conductivity of the composite, but also a challenge to fabricate cathodes with uniform graphene coating because of its two-dimensional planar structure. Besides, the graphene coating layer is easily peeled off from the cathode material during the cycling process, especially at the upper cutoff voltage. Therefore, we introduced a double-functional layer synergistically modified strategy to facilitate the electrochemical properties of LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials. In the designed architecture, the LiNi_0.8Co_0.1Mn_0.1O₂ particles were uniformly enwrapped by a functional reduced graphene oxide (RGO)-KH560 polymer composite layer which consists of an inner high-flexibility epoxy-functionalized silane (KH560) layer and an outer RGO layer with high electronic conductivity. The KH560 layer, in the structural system, is especially critical in connecting the layer of outer RGO and the inner surface of the active material, which brings about the perfect and complete double-functional coating layer and in turn fully expresses the modification effect of both KH560 and RGO in the improvement of electrochemical performance. Consequently, higher capacity retention, better rate, and improved high-temperature performances (55 °C) at the upper cutoff voltage (4.5 V) of this composite are identified when compared with the RGO-coated and pristine samples. In particular, the cathode with RGO (0.5%)-KH560 (0.5%) coating exhibits capacity retentions of 95.2 and 81.5% after 150 cycles at 1 C, 4.5 V at room and high temperatures, respectively.

Design of a 3D-Porous Structure with Residual Carbon for High-Performance Ni-Rich Cathode Materials

Recently, LiNi_0.8Co_0.1Mn_0.1O₂ has drawn much attention because of its high energy density. Here, 3D-porous LiNi_0.8Co_0.1Mn_0.1O₂ and the one with residual carbon have been synthesized using a resorcinol-formaldehyde-assisted sol-gel approach. Scanning electron microscopy images verify that the synthesized LiNi_0.8Co_0.1Mn_0.1O₂ possesses a 3D-porous morphology. X-ray photoelectron spectroscopy analysis and transmission electron microscopy-mapping images indicate the existence of residual carbon in the secondary particle of 3D-porous LiNi_0.8Co_0.1Mn_0.1O₂. Furthermore, 3D-porous LiNi_0.8Co_0.1Mn_0.1O₂ with residual carbon exhibits outstanding electrochemical properties. At a current density of 1900 mA g^-1, the 3D-porous LiNi_0.8Co_0.1Mn_0.1O₂ with residual carbon can still deliver a reversible capacity of 113 . Moreover, after 150 cycles at 0.2 C, the capacity retention of 3D-porous LiNi_0.8Co_0.1Mn_0.1O₂ with residual carbon reaches to 95%. The excellent electrochemical properties can be ascribed to the unique 3D-porous morphology and residual carbon in the secondary particle.

Spray-Drying of Electrode Materials for Lithium- and Sodium-Ion Batteries

The performance of electrode materials in lithium-ion (Li-ion), sodium-ion (Na-ion) and related batteries depends not only on their chemical composition but also on their microstructure. The choice of a synthesis method is therefore of paramount importance. Amongst the wide variety of synthesis or shaping routes reported for an ever-increasing panel of compositions, spray-drying stands out as a versatile tool offering demonstrated potential for up-scaling to industrial quantities. In this review, we provide an overview of the rapidly increasing literature including both spray-drying of solutions and spray-drying of suspensions. We focus, in particular, on the chemical aspects of the formulation of the solution/suspension to be spray-dried. We also consider the post-processing of the spray-dried precursors and the resulting morphologies of granules. The review references more than 300 publications in tables where entries are listed based on final compound composition, starting materials, sources of carbon etc.

Conductive Polymers Encapsulation To Enhance Electrochemical Performance of Ni-Rich Cathode Materials for Li-Ion Batteries

Ni-rich cathode materials have drawn lots of attention owing to its high discharge specific capacity and low cost. Nevertheless, there are still some inherent problems that desiderate to be settled, such as cycling stability and rate properties as well as thermal stability. In this article, the conductive polymers that integrate the excellent electronic conductivity of polyaniline (PANI) and the high ionic conductivity of poly(ethylene glycol) (PEG) are designed for the surface modification of LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials. Besides, the PANI-PEG polymers with elasticity and flexibility play a significant role in alleviating the volume contraction or expansion of the host materials during cycling. A diversity of characterization methods including scanning electron microscopy, energy-dispersive X-ray spectrometer, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared have demonstrated that LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials is covered with a homogeneous and thorough PANI-PEG polymers. As a result, the surface-modified LiNi_0.8Co_0.1Mn_0.1O₂ delivers high discharge specific capacity, excellent rate properties, and outstanding cycling performance.

Synthesis Method for Long Cycle Life Lithium-Ion Cathode Material: Nickel-Rich Core-Shell LiNi0.8Co0.1Mn0.1O2

High-nickel materials with core-shell structures, whose bulk is rich in nickel content and the outer shell is rich in manganese content, have been demonstrated to improve cycle stability. The high-nickel cathode material LiNi_0.8Co_0.1Mn_0.1O₂ is a very promising material for lithium-ion batteries; however, its low rate performance and especially cycle performance currently hamper further commercialization. This study presents a new synthesis method to prepare this core-shell material (LiNi_0.8Co_0.1Mn_0.1O₂@ x[Li-Mn-O], x = 0.01, 0.03, 0.06). Electrochemical data show that LiNi_0.8Co_0.1Mn_0.1O₂@ x[Li-Mn-O] ( x = 0.03, CS-0.03) exhibits the best high-rate performance, cycle stability, and thermal stability. The initial discharge capacity of the core-shell sample CS-0.03 is 118 mAh g^-1, which is almost the same as the discharge capacity of pristine LiNi_0.8Mn_0.1Co_0.1O₂ (117 mAh g^-1) at the rate of 10 C in the voltage range of 3.0-4.3 V. Notably the capacity decay of CS-0.03 is 18.4% after 200 cycles compared to 27% decay in capacity of the pristine sample. Furthermore, CS-0.03 exhibits better thermal cycling stability. The capacity retention of the CS-0.03 sample reached 65.1% which is over 1.3 times than that of the pristine one, whose capacity retention is 49.2% after 105 cycles (55 °C). Evidently, the core-shell structured CS-0.03 sample has excellent cycle stability and this synthesis method can be applied to other cathode materials.

Revealing the role of NH4VO3 treatment in Ni-rich cathode materials with improved electrochemical performance for rechargeable lithium-ion batteries

Although Ni-rich layered oxides are considered a candidate of next-generation cathode materials, their inherent properties, such as surface lithium residues and structural destruction, cause detrimental electrochemical performance, especially at elevated temperatures. Here, a facile ball-milling method is proposed to remove the lithium residues and enhance the electrochemical performance of LiNi0.6Co0.2Mn0.2O2. After NH4VO3 treatment, a lithium ion-conductive Li3VO4 coating layer is found on the LiNi0.6Co0.2Mn0.2O2 surface at heat-treatment temperatures of 300 and 450 °C, with a small part of vanadium ions diffusing into the surface lattice. When the temperature surpasses 600 °C, almost all vanadium ions dope into the bulk structure. The complex relationships between the post-sintering temperature and surface structure and their impact on electrochemical properties are discussed in detail. Electrochemical tests show that 0.5 wt% NH4VO3 treated LiNi0.6Co0.2Mn0.2O2 at 450 °C exhibits much improved cycling stability (96.1% cycling retention at 0.5C after 100 cycles and 97.2% after 50 cycles at 55 °C), rate capability (117.0 mA h g-1 at 5C), and storage property (4683 ppm lithium residue amount after storing in air for 7 days). Such superior performance is ascribed to the Li3VO4 coating layer that inhibits the electrolyte decomposition and helps create a stable and thinner cathode-electrolyte interface, resulting in decreased interfacial resistance. In addition, this coating layer suppresses internal micro-stress and phase transformation from a layered to spinel and rock-salt structure, which increases the structural integrity of LiNi0.6Co0.2Mn0.2O2 during repeated charge-discharge cycling.

Effect of cobalt content on the electrochemical properties and structural stability of NCA type cathode materials

Computational design of environmentally benign low-cost, cathode materials with reduced cobalt concentration.

LiNi0.8Co0.15Al0.05O2: Enhanced Electrochemical Performance From Reduced Cationic Disordering in Li Slab

Sub-micron sized LiNi_0.8Co_0.15Al_0.05O₂ cathode materials with improved electrochemical performance caused by the reduced cationic disordering in Li slab were synthesized through a solid state reaction routine. In a typical process, spherical precursor powder was prepared by spray drying of a uniform suspension obtained from the ball-milling of the mixture of the starting raw materials. Then the precursor powders were pressed into tablets under different pressures and crushed into powder. The pressing treated powders were finally calcinated under oxygen atmosphere to obtain the target cathode materials. XRD investigation revealed a hexagonal layered structure without impurity phase for all samples and significant increase in the diffraction intensity ratio of I₍₀₀₃₎/I₍₁₀₄₎ was observed. Rietveld refinement further confirmed the reduced cationic disordering in Li slab by such pressing treatment, and the smallest disordering was observed for sample S4 with only 1.3% Ni ions on Li lattice position. The electrochemical testing showed an improvement in electrochemical behavior for those pressing treated samples. The calculation of diffusion coefficients using EIS data showed improved Li diffusion coefficient after pressing treatment. The sample S4 presented a diffusion coefficient of 4.36 × 10⁻¹¹ cm²·s⁻¹, which is almost 3.5 times the value of untreated sample.

Preparation and Rate Capability of Carbon Coated LiNi1/3Co1/3Mn1/3O2 as Cathode Material in Lithium Ion Batteries

LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) is regarded as a promising material for next-generation lithium ion batteries due to the high capacity, but its practical applications are limited by the poor electronic conductivity. Here, a one-step method is used to prepare carbon coated LiNi_1/3Co_1/3Mn_1/3O₂ (NCM/C) by applying active carbon as reaction matrix. TEM shows LiNi_1/3Co_1/3Mn_1/3O₂ particles are homogeneously coated by carbon with a thickness about 10 nm. NCM/C delivers the discharge capacity of 191.2 mAh g^-1 at 0.5 C (85 mA g^-1) with a columbic efficiency of 91.1%. At 40 C (6800 mA g^-1), the discharge capacity of NCM/C is 54.6 mAh g^-1, whereas NCM prepared through sol-gel route only delivers 13.2 mAh g^-1. After 100 charge and discharge cycles at 1 C (170 mA g^-1) the capacity retention is 90.3% for NCM/C, whereas it is only 72.4% for NCM. The superior charge/discharge performance of NCM/C owes much to the carbon coating layer, which is not only helpful to increase the electronic conductivity but also contributive to inhibit the side reactions between LiNi_1/3Co_1/3Mn_1/3O₂ and the liquid electrolyte.

Influence of integrated microstructure on the performance of LiNi0.8Co0.15Al0.05O2 as a cathodic material for lithium ion batteries

An integrated network of LiNi_0.8Co_0.15Al_0.05O₂ spheres may accumulate the stress generated during cycling to maintain the stability of the microstructure.