A novel preparation method of active materials for the lithium secondary battery

LiNi_0.8Co_0.2O₂ is a promising candidate to replace LiCoO₂. The present paper describes the preparation of LiNi_0.8Co_0.2O₂ compounds from nitrate sources and sucrose (or sugar) by the sucrose combustion process (SCP), which involves application of a conventional combustion method. In the proposed approach, sucrose serves as a fuel, a dispersing agent, and a precipitation suppressant. Precursors were made via a combustion reaction, and LiNi_0.8Co_0.2O₂ was subsequently synthesized by heat treatment at 800 °C for 16 h in oxygen atmosphere. The initial discharge capacity was 175 mA h/g when a cell was operated at 2.7–4.3 V at 0.5 C-rate. Furthermore, it shows good cycling stability. When increased amount of sucrose were added as a start material, the final calcined powder displayed smaller particle size and better discharge capacity. It is expected that optimization of the heat treatment conditions would yield LiNi_0.8Co_0.2O₂ with excellent properties. Furthermore, SCP is expected to be applicable to the production of various materials.     

LiCoO2梯度包覆LiNi0.96Co0.04O2电极材料的电化学性能

镍钴酸锂(LiNi0.8Co0.2O2)与目前商业用锂离子电池正极材料钴酸锂(LiCoO2)相比,具有成本低、实际比容量高和环境友好等优势。但LiNi0.8Co0.2O2的充放循环性能还有待提高,对其进行阳离子掺杂或表面修饰可以改善其电化学性能,这方面的研究已经成为热点。Fey等人[1]用溶胶凝胶法制     

A simple and effective strategy to synthesize Al2O3-coated LiNi0.8Co0.2O2 cathode materials for lithium ion battery

A facile method has been developed to synthesize Al₂O₃-coated LiNi_0.8Co_0.2O₂ cathode materials. The sample was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy dispersive analysis of X-rays (EDAX). Electrochemical tests show that the cycling stability of LiNi_0.8Co_0.2O₂ at room temperature is effectively improved by Al₂O₃ coating. The differential scanning calorimetry (DSC) and high temperature (60 °C) cycling tests indicate that Al₂O₃ coating can also improve the thermal stability of LiNi_0.8Co_0.2O₂, which is attributed to that the coating layer can protect the LiNi_0.8Co_0.2O₂ particles from reacting with the electrolyte.     

Towards high-performance cathode materials for lithium-ion batteries: Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-coated LiNi<Subscript>0.8</Subscript>Co<Subscript>0.15</Subscript>Zn<Subscript>0.05</Subscript>O<Subscript>2</Subscript>

Zn-doped LiNi_0.8Co_0.2O₂ exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi_0.8Co_0.15Zn_0.05O₂ as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al₂O₃ layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂ cathode delivers a highly reversible capacity of 182 mA h g^?1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi_0.8Co_0.15Zn_0.05O₂ cathode. The enhanced electrochemistry performance can be attributed to the Al₂O₃-coated protective layer, which prevents the direct contact between the LiNi_0.8Co_0.15Zn_0.05O₂ and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂, which rationally illuminates the protection mechanism of the Al₂O₃-coated layer.     

Synergistic Dual-Additive Electrolyte Enables Practical Lithium-Metal Batteries

A rechargeable Li metal anode coupled with a high-voltage cathode is a promising approach to high-energy-density batteries exceeding 300 Wh kg⁻¹. Reported here is an advanced dual-additive electrolyte containing a unique solvation structure and it comprises a tris(pentafluorophenyl)borane additive and LiNO₃ in a carbonate-based electrolyte. This system generates a robust outer Li₂O solid electrolyte interface and F- and B-containing conformal cathode electrolyte interphase. The resulting stable ion transport kinetics enables excellent cycling of Li/LiNi_0.8Mn_0.1Co_0.1O₂ for 140 cycles with 80 % capacity retention under highly challenging conditions (≈295.1 Wh kg⁻¹ at cell-level). The electrolyte also exhibits high cycling stability for a 4.6 V LiCoO₂ (160 cycles with 89.8 % capacity retention) cathode and 4.95 V LiNi_0.5Mn_1.5O₄ cathode.     

Synergistic Dual‐Additive Electrolyte Enables Practical Lithium‐Metal Batteries

A rechargeable Li metal anode coupled with a high‐voltage cathode is a promising approach to high‐energy‐density batteries exceeding 300 Wh kg^?1. Reported here is an advanced dual‐additive electrolyte containing a unique solvation structure and it comprises a tris(pentafluorophenyl)borane additive and LiNO₃ in a carbonate‐based electrolyte. This system generates a robust outer Li₂O solid electrolyte interface and F‐ and B‐containing conformal cathode electrolyte interphase. The resulting stable ion transport kinetics enables excellent cycling of Li/LiNi_0.8Mn_0.1Co_0.1O₂ for 140 cycles with 80 % capacity retention under highly challenging conditions (≈295.1 Wh kg^?1 at cell‐level). The electrolyte also exhibits high cycling stability for a 4.6 V LiCoO₂ (160 cycles with 89.8 % capacity retention) cathode and 4.95 V LiNi_0.5Mn_1.5O₄ cathode.     

Synthesis and electrochemical properties of Ca-doped LiNi<Subscript>0.8</Subscript>Co<Subscript>0.2</Subscript>O<Subscript>2</Subscript> cathode material for lithium ion battery

LiNi_0.8Co_0.2O₂ and Ca-doped LiNi_0.8Co_0.2O₂ cathode materials have been synthesized via a rheological phase reaction method. X-ray diffraction studies show that the Ca-doped material, and also the discharged electrode, maintains a hexagonal structure even when cycled in the range of 3.0–4.35 V (vs Li⁺/Li) after 100 cycles. Electrochemical tests show that Ca doping significantly improves the reversible capacity and cyclability. The improvement is attributed to the formation of defects caused by the partial occupancy of Ca²⁺ ions in lithium lattice sites, which reduce the resistance and thus improve the electrochemical properties.     

Recent advances in layered LiNi x CoyMn1−x−y O2 cathode materials for lithium ion batteries

Lithium cobalt oxide, LiCoO₂, has been the most widely used cathode material in commercial lithium ion batteries. Nevertheless, cobalt has economic and environmental problems that leave the door open to exploit alternative cathode materials, among which LiNi _x Co_yMn_{1 − x − y} O₂ may have improved performances, such as thermal stability, due to the synergistic effect of the three ions. Recently, intensive effort has been directed towards the development of LiNi _x Co _y Mn_{1 − x − y} O₂ as a possible replacement for LiCoO₂. Recent advances in layered LiNi _x Co_yMn_{1 − x − y} O₂ cathode materials are summarized in this paper. The preparation and the performance are reviewed, and the future promising cathode materials are also prospected.     

掺F影响LiNi0.8Co0.1Mn0.1O2结构和性能的微观机制

以氟化锂为氟源,通过高温固相法合成了F掺杂的LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2。采用X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)和电化学测试等手段研究F影响LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2结构和性能的微观机制。结果表明:适量F掺杂可以提高正极材料的放电比容量,改善其倍率性、循环性和热稳定性。当F掺杂量(物质的量分数)为1.5%时,材料的综合电化学性能最优,初始放电比容量(0.2C)和50周循环容量保持率(1C)分别由原始的174.0 mAh·g~(-1)(78.7%)提高到178.6 mAh·g~(-1)(85.7%)。LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2材料性能的改善可归因于F能够增强过渡金属层、锂层与氧层之间的结合力,提高材料的结构稳定性。此外,F掺杂还有利于降低电化学反应中的界面电阻和电荷转移阻抗。     

Surface modification of LiNi0.8Co0.1Mn0.1O2 with conducting polypyrrole

A facile method for the surface modification of high-voltage and high-temperature LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials is demonstrated. In order to prepare polypyrrole (PPy) coating LiNi_0.8Co_0.1Mn_0.1O₂ material, the facile chemical polymerization method uses Fe(III) tosylate as oxidant and ethanol as solvent to avoid the side reaction with solvent. TEM depicts that LiNi_0.8Co_0.1Mn_0.1O₂ serves as hard template and the nanoscale PPy layer grows along the surface of LiNi_0.8Co_0.1Mn_0.1O₂ during the synthesis process. Because of flocculent and nanofiber coating layer, much improved rate performance, high temperature cycling, as well as high voltage performance are obtained. Cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) results demonstrate that the PPy coating layer effectively alleviates the side reactions between liquid electrolytes and LiNi_0.8Co_0.1Mn_0.1O₂ surface that are highly unstable at high temperature and high charge voltage.     

Synthesis of non-stoichiometric lithium nickel cobalt oxides and their structural and electrochemical characterization

Non-stoichiometric phases of lithium nickel cobalt oxides were synthesized by a sol–gel method using oxalic acid as a chelating agent. The structural properties have been examined using X-ray diffraction techniques. Electrochemical coin cell studies showed materials with excess lithium stoichiometry had interesting properties of improved capacity and cyclability. Of all the compositions with excess lithium stoichiometry, Li_1.1Ni_0.8Co_0.2O₂, showed better electrochemical characteristics with a first cycle discharge capacity of 182 mAh/g and a 10th cycle of 172 mAh/g than the ideal stoichiometry LiNi_0.8Co_0.2O₂. The structural and electrochemical properties of Li_xNi_0.8Co_0.2O₂ with x=1.00, 1.05, 1.10 and 1.15 are discussed in detail.     

Li4Mn5O12包覆对三元正极材料结构和性能的影响

LiNi(1/3)Mn(1/3)Co(1/3)O2具有很高的理论比容量,但是三元正极材料在高电压下长循环时,其表面结构发生较大的衰退,导致电池的循环性能和倍率性能变差。本文采用耐高电压且结构稳定的富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2可以有效改善材料的电化学性能。通过XRD、SEM、XPS和TEM等手段对包覆后的材料进行分析,证实了在LiNi(1/3)Mn(1/3)Co(1/3)O2的表面形成了10nm厚的均匀Li4Mn5O(12)的包覆层;在循环100圈后,包覆后的LiNi(1/3)Mn(1/3)Co(1/3)O2仍具有179.5m Ah/g的放电比容量和88.6%容量保持率,明显高于未包覆的LiNi(1/3)Mn(1/3)Co(1/3)O2的78.3%容量保持率。因此,利用富锂尖晶石Li4Mn5O(12)包覆LiNi(1/3)Mn(1/3)Co(1/3)O2为实现更高能量密度的锂离子电池提供了新的途径。     

Cathodic performance of anatase (TiO2)-coated Li(Ni0.8Co0.2)O2

We report the use of Li(Ni_0.8Co_0.2)O₂ coated with different amounts of anatase (TiO₂) as a cathode material for lithium-ion cells. Electrochemical behavior is modified owing to coating and/or incorporation of titanium into the first few surface layers of Li(Ni_0.8Co_0.2)O₂. Compositions with molar concentrations of x=0.005 and 0.02 exhibit better capacity retention than the mother compound (40 cycles, 0.5 C rate, 2.75–4.30 V). Electronic Publication     

Thermal processes in the systems with Li-battery cathode materials and LiPF6 -based organic solutions

Thermodynamic instability of positive electrodes (cathodes) in Li-ion batteries in humid air and battery solutions results in capacity fading and batteries degradation, especially at elevated temperatures. In this work, we studied thermal interactions between cathode materials Li₂MnO₃, xLi₂MnO₃ ^.(1???x)Li(MnNiCo)O₂,LiNi_0.33Mn_0.33Co_0.33O₂, LiNi_0.4Mn_0.4Co_0.2O₂, LiNi_0.8Co_0.15Al_0.05O₂ LiMn_1.5Ni_0.5O₄, LiMn(or Fe)PO₄, and battery solutions containing ethylene carbonate (EC) or propylene carbonate (PC), dimethyl carbonate (DMC) or ethylmethyl carbonate (EMC) and LiPF₆ salt in the temperature range of 40–400 °C. It was found that these materials are stable chemically and well performing in LiPF₆-based solutions up to 60 °C. The thermal decomposition of the electrolyte solutions starts >180 °C. The macro-structural transformations of cathode materials upon exothermic reactions were studied by transmission electron microscopy (TEM), X-ray difraction (XRD) and Raman spectroscopy. Differential scanning calorimetry (DSC) studies have shown that the exothermic reactions in the temperature range of 60–140 °C lead to partial decomposition of both the cathode material and electrolyte solution. The systems thus formed consisted of partially decomposed solutions and partially chemically delithiated cathode materials covered by reactions products. Thermal reactions terminate and this system reaches equilibrium at about 120 °C. It remains stable up to the beginning of the solution decomposition at about 180 °C. The increased content of surface Li₂CO₃ is found to significantly affect the thermal processes at high temperature range due to extensive exothermic decomposition at low temperatures.     

Preparation and characterization of LiNi0.8Co0.2O2/PANI microcomposite electrode materials under assisted ultrasonic irradiation

A preparation method for a new electrode material based on the LiNi_0.8Co_0.2O₂/polyaniline (PANI) composite is reported. This material is prepared by in situ polymerization of aniline in the presence of LiNi_0.8Co_0.2O₂ assisted by ultrasonic irradiation. The materials are characterized by XRD, TG-DTA, FTIR, XPS, SEM-EDX, AFM, nitrogen adsorption (BET surface area) and electrical conductivity measurements. PANI in the emeraldine salt form interacts with metal-oxide particles to assure good connectivity. The dc electrical conductivity measurements at room temperature indicate that conductivity values are one order of magnitude higher in the composite than in the oxide alone. This behavior determines better reversibility for Li-insertion in charge-discharge cycles compared to the pristine mixed oxide when used as electrode of lithium batteries.     

The ionic conductivity, thermal expansion behavior, and chemical compatibility of La0.54Sr0.44Co0.2Fe0.8O3-δ as SOFC cathode material

In this paper, the ionic conductivities of La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ were measured by electron-blocked alternating current impedance analysis technique. The results show that the oxygen ion conductivity of La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ is nearly five times higher than that of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ, which makes La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ cathode more conductive than YSZ electrolyte. Consequently, the electrochemical reaction region is extended from the interface between the cathode and the electrolyte to the whole surface of the cathode grains, with a result of the cathode polarization overpotential being decreased and the cell electrical performance being improved. Besides, the XRD results show that both La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ begin to react with 8YSZ([Y₂O₃]_0.08·[ZrO₂]_0.92) at 850 °C, but La_0.54Sr_0.44Co_0.2Fe_0.8O_3-δ with a faster reaction rate. The thermal expansion experiments manifest that the two LSCFs have approximate thermal expansion coefficients, being about 14 × 10⁻⁶–15 × 10⁻⁶ K⁻¹ from 500 °C to 700 °C, which is moderately higher than that of 8YSZ.     

Electrochemical characterization of polypyrrole–LiNi<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>O<Subscript>2</Subscript> composite cathode material for aqueous rechargeable lithium batteries

A series of polypyrrole (PPy)–LiNi_1/3Mn_1/3Co_1/3O₂ composite electrodes are formed by physical mixing of polypyrrole with LiNi_1/3Mn_1/3Co_1/3O₂ cathode material. LiNi_1/3Mn_1/3Co_1/3O₂ is synthesized by reaction under autogenic pressure at elevated temperature method. Highly resolved splitting of 006/102 and 108/110 peaks in the XRD pattern provide an evidence to well-ordered layered structure of the compound. The ratios of the intensities of 003 and 104 peaks are found to be >1, which indicate no pronounced mixing of the cation. Cyclic voltammetry and AC impedance studies revealed that the addition of polypyrrole significantly decreases the charge-transfer resistance of LiNi_1/3Mn_1/3Co_1/3O₂ electrodes. The electrochemical reactivity of PPy–LiNi_1/3Mn_1/3Co_1/3O₂ composite electrode is examined during lithium ion insertion and de-insertion by galvanostatic charge–discharge testing; 10 wt.% PPy–LiNi_1/3Mn_1/3Co_1/3O₂ composite electrode exhibits better electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiNi_1/3Mn_1/3Co_1/3O₂ electrode. The cell with 10 wt.% PPy added cathode shows significant improvement in the electrochemical performance compared with that having pristine cathode. The capacity remains about 70% of the initial value after 50 cycles while for cell with pristine cathode only about 28% of initial capacity remains after 40 cycles.     

LiNi<Subscript>0.8</Subscript>Co<Subscript>0.2−x</Subscript>Ti<Subscript>x</Subscript>O<Subscript>2</Subscript> nanoparticles: synthesis,structure, and evaluation of electrochemical properties for lithium ion cell application

Layered Ti-doped lithiated nickel cobaltate, LiNi_0.8Co_{0.2 − x}Ti_xO₂ (where x = 0.01, 0.03, and 0.05) nanopowders were prepared by wet-chemistry technique. The structural properties of synthesized materials were characterized by X-ray diffraction (XRD) and thermo-gravimetric/differential thermal analysis (TG/DTA). The morphological changes brought about by the changes in composition of LiNi_0.8Co_{0.2 − x}Ti_xO₂ particles were examined through surface examination techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. Electrochemical studies were carried out using 2016-type coin cell in the voltage range of 3.0–4.5 V (vs carbon) using 1 M LiClO₄ in ethylene carbonate and diethyl carbonate as the electrolyte. Among the various concentrations of Ti-doped lithiated nickel cobaltate materials, C/LiNi_0.8Co_0.17Ti_0.03O₂ cell gives stable charge–discharge features.     

Suppressing Universal Cathode Crossover in High-Energy Lithium Metal Batteries via a Versatile Interlayer Design**

The universal cathode crossover such as chemical and oxygen has been significantly overlooked in lithium metal batteries using high-energy cathodes which leads to severe capacity degradation and raises serious safety concerns. Herein, a versatile and thin (≈25 μm) interlayer composed of multifunctional active sites was developed to simultaneously regulate the Li deposition process and suppress the cathode crossover. The as-induced dual-gradient solid-electrolyte interphase combined with abundant lithiophilic sites enable stable Li stripping/plating process even under high current density of 10 mA cm⁻². Moreover, X-ray photoelectron spectroscopy and synchrotron X-ray experiments revealed that N-rich framework and CoZn dual active sites can effectively mitigate the undesired cathode crossover, hence significantly minimizing Li corrosion. Therefore, assembled lithium metal cells using various high-energy cathode materials including LiNi_0.7Mn_0.2Co_0.1O₂, Li_1.2Co_0.1Mn_0.55Ni_0.15O₂, and sulfur demonstrate significantly improved cycling stability with high cathode loading.     

Recycling Valuable Metals from Spent Lithium-Ion Batteries Using Carbothermal Shock Method

Pyrometallurgy technique is usually applied as a pretreatment to enhance the leaching efficiencies in the hydrometallurgy process for recovering valuable metals from spent lithium-ion batteries. However, traditional pyrometallurgy processes are energy and time consuming. Here, we report a carbothermal shock (CTS) method for reducing LiNi_0.3Co_0.2Mn_0.5O₂ (NCM325) cathode materials with uniform temperature distribution, high heating and cooling rates, high temperatures, and ultrafast reaction times. Li can be selectively leached through water leaching after CTS process with an efficiency of >90 %. Ni, Co, and Mn are recovered by dilute acid leaching with efficiencies >98 %. The CTS reduction strategy is feasible for various spent cathode materials, including NCM111, NCM523, NCM622, NCM811, LiCoO₂, and LiMn₂O₄. The CTS process, with its low energy consumption and potential scale application, provides an efficient and environmentally friendly way for recovering spent lithium-ion batteries.