Nanogravel structured NiO/Ni foam as electrode for high-performance lithium-ion batteries

Nanogravel structured NiO/Ni electrodes were fabricated by using two-step thermal oxidation method of commercial nickel (Ni) foam in air for lithium-ion batteries (LIBs). The macro- and micro-structures of the NiO/Ni foam were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), and Raman spectroscopy. Galvanostatic tests revealed that the electrode exhibits no obvious capacity fading over 40 cycles at 1 C (718 mAg^?1) and 2.5 C (1.8 Ag^?1) current rate. The discharge capacity was higher than the theoretical capacity of NiO even at a high-current rate of 2.5 C. The electrodes can deliver a reversible capacity of 1116.65 mAh g^?1 after 20th cycle at 1 C rate and 1026.20 mAh g^?1 after 40th cycle at 2.5 C rate. The cyclic voltammograms and impedance spectra analysis indicated that a redox reaction of NiO–Ni⁰ with formation and decomposition of Li₂O. The excellent electrochemical performance is mainly attributed to the nanogravel structure of the NiO/Ni foam electrodes as well as its excellent electrical contact between NiO and Ni. The unique nanostructured NiO on the highly conductive metallic Ni in core resulted in the enhanced discharge capacity, coulombic efficiency, cyclic stability, and rate capability when utilized as negative electrodes in LIBs.     

The significance of the stable Rhombohedral structure in Li-rich cathodes for lithium-ion batteries

The lithium-rich layered oxides offer higher capacity, but suffer from severe capacity fade and voltage decay. Aluminum doping can improve the stability of the structure, but the fundamental mechanism has not been fully revealed. In this work, cathode materials with different Al-doping contents are investigated. To characterize the structural evolutions upon cycling, ex situ XRD and ex situ TEM are performed. It is demonstrated that the voltage decay is attributed to the decrease of Rhombohedral phase, while capacity fade is possibly associated with the increase of surface impedance. Therefore, continuous voltage decay and capacity fade are observed for undoped Li-rich cathode. In comparison, the Al-doped cathodes have stable LiNi_1/3Co_1/3Mn_1/3O₂ and surface impedance, leading to superior capacity retention and a stable output voltage.     

Synthesis and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 cathodes in lithium-ion and all-solid-state lithium batteries

Ionics - LiNi1/3Co1/3Mn1/3O2 cathodes have been prepared by a solid-state reaction process. The effects of calcination and post-annealing temperature on electrochemical performances were...     

Oligo(ethylene oxide)-functionalized trialkoxysilanes as novel electrolytes for high-voltage lithium-ion batteries

Oligo(ethylene oxide)-functionalized trialkoxysilanes were synthesized through hydrosilylation reaction by reacting trialkoxysilane with oligo(ethylene oxide) allyl methyl ether using PtO₂ as a catalyst. The physical properties of these compounds, such as viscosity, dielectric constant, and ionic conductivity, were characterized. Among them, [3-(2-(2-methoxyethoxy)ethoxy)-propyl]triethoxysilane (TESM2) exhibited a commercial viable ionic conductivity of 1.14 mS cm^?1 and a wide electrochemical window of 5.2 V. A preliminary investigation was conducted by using TESM2 as an electrolyte solvent for high-voltage applications in lithium-ion batteries. Using 1 M LiPF₆ in TESM2 with 1 vol% vinyl carbonate as an electrolyte, LiCoO₂/Li half-cell delivered a specific capacity of 153.9 mAh g^?1 and 90 % capacity retention after 80 cycles (3.0–4.35 V, 28 mA g^?1); Li_1.2Ni_0.2Mn_0.6O₂/Li₄Ti₅O₁₂ full cell exhibited the initial capacity of 161.3 mAh g^?1 and 86 % capacity retention after 30 cycles (0.5–3.1 V, 18 mA g^?1).     

Electrochemical performances of a novel lithium bis(oxalate)borate-based electrolyte for lithium-ion batteries with LiFePO4 cathodes

Lithium bis(oxalate)borate (LiBOB) is a promising salt for lithium-ion batteries. However, it is necessary to exert the electrochemical performance of LiBOB by the appropriate solvent. With dimethyl sulfite (DMS) as mixed solvents, the electrochemical behavior of γ-butyrolactone (GBL) with LiBOB is studied in this paper. It shows that LiBOB-GBL/DMS electrolyte has high oxidation potential (>5.3 V) and satisfactory conductivities. When used in lithium and mesophase carbon microbead cells, the novel electrolyte exhibits not only excellent film-forming characteristics but also low impedances of the interface films. Besides, when used in LiFeO₄/Li cells, compared to the cell with the electrolyte system of 1 mol L^?1 LiPF₆–ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1, v/v), LiBOB-based electrolyte exhibits several advantages, such as more stable cycle performance at room temperature and higher mean voltage.     

A review on microwave synthesis of electrode materials for lithium-ion batteries

The applications of microwave processing of electrode materials for Li-ion batteries have been reviewed. This paper intends to insist at the advantages of the microwave processing and its credentials for commercialization. In order to achieve successive commercialization/industrial application, a systematic understanding of the microwave processing becomes imperative. In the advent of this, an extensive study on the behavior of material in electromagnetic field has been presented. Microwave processing of various materials like lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium titanium oxide and their derivatives, copper bismuth oxide, antimony sulfide, and tin oxide graphite has been reviewed in detail. Also, the dependence of microwave processing in operating frequency, geometry, preheating, soaking time, susceptor material, and single (or) multimode cavity has been reviewed.     

Dinitrile compound containing ethylene oxide moiety with enhanced solubility of lithium salts as electrolyte solvent for high-voltage lithium-ion batteries

A dinitrile compound containing ethylene oxide moiety (4,7-dioxa-1,10-decanedinitrile, NEON) is synthesized as an electrolyte solvent for high-voltage lithium-ion batteries. The introduction of ethylene oxide moiety into the conventional aprotic aliphatic dinitrile compounds improves the solubility of lithium hexafluorophosphate (LiPF₆) used commercially in the lithium-ion battery industry. The electrochemical performances of the NEON-based electrolyte (0.8 M LiPF₆?+?0.2 M lithium oxalyldifluoroborate in NEON:EC:DEC, v:v:v?=?1:1:1) are evaluated in graphite/Li, LiCoO₂/Li, and LiCoO₂/graphite cells. Half-cell tests show that the electrolyte exhibits significantly improved compatibility with graphite by the addition of vinylene carbonate and lithium oxalyldifluoroborate and excellent cycling stability with a capacity retention of 97 % after 50 cycles at a cutoff voltage of 4.4 V in LiCoO₂/Li cell. A comparative experiment in LiCoO₂/graphite full cells shows that the electrolyte (NEON:EC:DEC, v:v:v?=?1:1:1) exhibits improved cycling stability at 4.4 V compared with the electrolyte without NEON (EC:DEC, v:v?=?1:1), demonstrating that NEON has a great potential as an electrolyte solvent for the high-voltage application in lithium-ion batteries.     

A study of the capacity fade of porous NiO/Ni foam as negative electrode for lithium-ion batteries

High energy density materials such as NiO that undergoes conversion reaction hold promise for lithium (Li)-ion batteries (LIBs). However, porous NiO experiences substantial volume change due to the diffusion-induced stress during electrochemical operation, which causes mechanical fractures and morphological changes of porous NiO electrodes, leading to capacity fade through internal short circuit (ISCr). In this study, both non-destructive and destructive operations were used to visualize and quantify the origins and evolutions of the capacity fading of porous NiO/Ni foam electrodes. Results indicated that charge transfer resistance was dominant among all the internal resistances before ISCr, whereas solid electrolyte interface (SEI) resistance was dominant after ISCr of LIBs. The generation of the large amount of heat and pressure during ISCr caused the volume expansion and the formation of the micro-cracks in the struts of the porous NiO/Ni foam electrodes. Together with the electrolyte decomposition, this led to capacity fade. The results of this study provide insights for developing of NiO/Ni electrode for LIBs.     

Hydrothermal synthesis and electrochemical performance studies of Al2O3-coated LiNi1/3Co1/3Mn1/3O2 for lithium-ion batteries

LiNi_1/3Co_1/3Mn_1/3O₂ nanocrystallites were synthesized by a one-step hydrothermal method, and uniform second particles were formed by a subsequent calcination process. X-ray diffraction results indicate that the as-synthesized material can be indexed by α-NaFeO₂ layered structure with R-3 m space group. The results of Rietveld refinements show the I ₀₀₃/I ₁₀₄ value of the material is 2.032, and the nanostructured material presents low cation mixing, small cell volume, and a consequent suppression of lattice strain. The rate performances of the as-synthesized material can be further improved by coating Al₂O₃. The discharging capacity of Al₂O₃-coated material reaches 154.4 mAh g^?1, and the capacity retention maintains 80.3 % after 50 cycles at 5 C in the voltage range of 2.5 to 4.5 V, while those of the bare one is only 139.0 mAh g^?1 and 71.6 %, respectively. The transmission electron microcopy observation shows no zigzag layer exists on the surface of particle after cycles for Al₂O₃-coated LiNi_1/3Co_1/3Mn_1/3O₂. Compared to bare LiNi_1/3Co_1/3Mn_1/3O₂, the de-intercalation potential difference before and after cycles of Al₂O₃-coated one is smaller. This indicates that Al₂O₃ coating can reduce the electrochemistry polarization in the electrode bulk.     

Li2MnSiO4/carbon nanofiber cathodes for Li-ion batteries

Pure single-phase Li₂MnSiO₄ nanoparticle-embedded carbon nanofibers have been prepared for the first time via a simple sol-gel and electrospinning technique. They exhibit an improved electrochemical performance over conventional carbon-coated Li₂MnSiO₄ nanoparticle electrodes, including a high discharge capacity of ～200 mAh g^?1, at a C/20 rate, with the retention of 77 % over 20 cycles and a 1.6-fold higher discharge capacity at a 1 C rate.     

锂离子电池用具有分级三维离子电子混合导电网络结构的纳微复合电极材料

文章评述了分级三维离子电子混合导电网络结构和具有该结构的纳微复合电极材料在锂离子电池中的应用等方面的最新研究工作进展.首先介绍了纳微复合电极结构相关概念及其优缺点,然后列举了一些运用此概念设计并构筑出的电极材料实例.研究证明,此新型电极结构能够大幅提高锂离子电池电极材料的储锂性能,并且该结构设计还可推广到其他电化学储能...     

Carbon-coated Si/graphite composites with combined electrochemical properties for high-energy-density lithium-ion batteries

Carbon-coated Si/graphite composites with different Si/graphite weight ratio have been fabricated using solid-state reaction with aim to improve the cyclic stability, coulombic efficiency, and rate capability simultaneously. Microstructural investigation reveals that the Si particles are covered by amorphous carbon and attached to the carbon-coated graphite surface. Electrochemical evaluation has been performed using cyclic voltammetry and charge/discharge cycling at different current densities, which indicate that addition of graphite can not only enhance the first-cycle coulombic efficiency to 90 % but also improve the cyclic stability drastically. The carbon-coated Si/graphite composite with appropriate contents of Si, graphite, and carbon is expected to be promising candidate as anode materials for high-energy-density lithium-ion batteries.     

Effects of binder content on manganese dissolution and electrochemical performances of spinel lithium manganese oxide cathodes for lithium ion batteries

In this study, the effects of the polyvinylidene fluoride (PVdF) binder on the Mn dissolution behavior and electrochemical performances of LiMn₂O₄ (LMO) electrodes are investigated. It is found that increasing the PVdF content (3, 5, 7, and 10 wt.%) leads to reduced Mn dissolution, and thus superior cycle performance at elevated temperature (60 °C). This can be ascribed to increased binder coverage on the LMO surface, as evidenced by X-ray photoelectron spectroscopy measurements, which acts a role as a passivation layer for Mn dissolution. The rate capability of the LMO electrode is hardly deteriorated as the PVdF content increases, despite the increasing surface coverage. Electrochemical impedance measurements reveal that the LMO electrode with higher binder loading exhibits lower electrode impedance, which is suggested to be due to enhanced electronic passage through the composite LMO electrode.     

High rate performance of Li[Ni1/3Co1/3Mn1/3]O2 synthesized via co-precipitation method by different precipitators

In the present study, we investigated the effect of three different precipitators (NaOH, Na₂CO₃ and (NH₄)₂CO₃) on the synthesized layered Li[Ni_1/3Co_1/3Mn_1/3]O₂ cathode materials via co-precipitation method. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and galvanostatic charge–discharge measurements. The XRD patterns analysis showed that all the resulted Li[Ni_1/3Co_1/3Mn_1/3]O₂ materials possess a layered hexagonal structure. It was found that at high discharge rate (2C), the prepared Li[Ni_1/3Co_1/3Mn_1/3]O₂ system using Na₂CO₃ as the precipitator exhibits better cycling performance in the charge–discharge tests compared to others, indicating that Na₂CO₃ is an optimum precipitator. After 100 cycles at 2C discharge rate in the voltage range from 2.8 to 4.5 vs. Li/Li⁺, the Li[Ni_1/3Co_1/3Mn_1/3]O₂ system using Na₂CO₃ as the precipitator retains 97% of its initial discharge capacity.     

Enhanced electrochemical performance of La- and Zn-co-doped LiMn2O4 spinel as the cathode material for lithium-ion batteries

We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles?? surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500???g/cm³ in 24?h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.     

Modified carbothermal synthesis and electrochemical performance of LiFePO4/C composite as cathode materials for lithium-ion batteries

LiFePO₄/C active materials were synthesized via a modified carbothermal method, with a low raw material cost and comparatively simple synthesis process. Rheological phase technology was introduced to synthesize the precursor, which effectively decreased the calcination temperature and time. The LiFePO₄/C composite synthesized at 700 °C for 12 h exhibited an optimal performance, with a specific capacity about 130 mAh g^?1 at 0.2C, and 70 mAh g^?1 at 20C, respectively. It also showed an excellent capacity retention ratio of 96 % after 30 times charge–discharge cycles at 20C. EIS was applied to further analyze the effect of the synthesis process parameters. The as-synthesized LiFePO₄/C composite exhibited better high-rate performance as compared to the commercial LiFePO₄ product, which implied that the as-synthesized LiFePO₄/C composite was a promising candidate used in the batteries for applications in EVs and HEVs.     

Nanowires of spinel cathode material for improved lithium-ion storage

Li-excess layered materials, such as Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ (LMNCO) et al. are promising cathode materials that can be used in batteries for hybrid electric vehicles (HEV)/electric vehicles (EV), due to their excellent lithium-storage capability and very high energy density. Dramatic capacity loss during electrochemical cycling seriously hinders their practical implementation. It is found that the LMNCO layered cathode material suffers from structural instability and irreversible layered-to-spinel phase transition during lithiation/delithiation, leading to dramatic loss of capacity and deteriorated electrochemical kinetics. To overcome this challenge, we synthesize spinel-structured LHMNCO TBA nanowires using an electrospinning method followed by facile ion-exchange promoted phase transition. After 100 electrochemical cycles at the specific current 0.5 C, spinel-structured LHMNCO TBA still retains a capacity of about 200 mAh/g, corresponding to a capacity retention ratio of 90.5%, much higher than that of layered LMNCO nanowires, which only maintains a specific capacity of 137 mAh/g with only 48.9% capacity retention.     

Controllable synthesis of spherical silicon and its performance as an anode for lithium-ion batteries

Spherical silicon is controllably synthesized by the hydrolysis of tetraethylorthosilicate (TEOS) with the addition of different contents of ammonia to form SiO₂, then reduced by magnesium powder in argon atmosphere at 900 °C for 3 h. The experimental results show that the electrochemical performance of the as-prepared silicon anode is much affected by the morphology of silicon, and the spherical silicon with a particle size of 250–300 nm shows a reversible capacity of 1,345.8 mAh g^?1 with the capacity retention of 83.2 % after 20 cycles. The relationship between the electrochemical performance of the spherical silicon and the diameters of silicon sphere makes it possible to control the performance of the silicon anode by adjusting the hydrolysis conditions of TEOS.