Boosting Thermal and Mechanical Properties: Achieving High-Safety Separator Chemically Bonded with Nano TiN Particles for High Performance Lithium-Ion Batteries

Currently, the commercial separator (Celgard2500) of lithium-ion batteries (LIBs) suffers from poor electrolyte affinity, mechanical property and thermal stability, which seriously affect the electrochemical performances and safety of LIBs. Here, the composite separators named PVDF-HFP/TiN for high-safety LIBs are synthesized. The integration of PVDF-HFP and TiN forms porous structure with a uniform and rich organic framework. TiN significantly improves the adsorption between PVDF-HFP and electrolyte, causing a higher electrolyte absorption rate (192%). Meanwhile, XPS results further demonstrate the tight link between PVDF-HFP and TiN due to the existence of Ti F bond in PVDF-HFP/TiN, resulting in a strong impediment for the puncture of lithium dendrites as a result of the improved mechanical strengths. And PVDF-HFP/TiN can effectively suppress the growth of lithium dendrites by means of uniform lithium flux. In addition, the excellent heat resistance of TiN improves the thermal stability of PVDF-HFP/TiN. As a result, the LiFePO₄||Li cells assembled PVDF-HFP/TiN-12 exhibit excellent specific capacity, rate performance, and capacity retention rate. Even the high specific capacity of 153 mAh g⁻¹ can be obtained at the high temperature of 80 °C. Meaningfully, a reliable modification strategy for the preparation of separators with high safety and electrochemical performance in LIBs is provided.     

PVDF-HFP基复合多孔聚合物电解质膜的研制

聚偏氟乙烯-六氟丙烯共聚物(PVDF-HFP)多微孔膜在锂离子电池领域中具有很好的应用前景.采用Bellcore制膜法,用纳米材料对PVDF-HFP为基质的聚合物微孔膜材料进行了改性.利用XRD,SEM,交流阻抗等测试手段对电解质膜的晶体结构、微观形貌、电化学性能等进行了表征.结果表明:改性后聚合物电解质膜的孔隙率增加、结晶度降低,PVDF-HFP/SiO2和PVDF-HFP/Al2O3聚合物电解质隔膜的电导率(20℃)分别达到2.762×10-3S/cm和3.517×10-3S/cm,相应的离子迁移数分别为0.80和0.82.     

Rational Design of a High-Loading Polysulfide Cathode and a Thin-Lithium Anode for Developing Lean-Electrolyte Lithium–Sulfur Full Cells

Lithium-sulfur cells are attractive energy-storage systems because of their high energy density and the electrochemical utilization rates of the high-capacity lithium-metal anode and the low-cost sulfur cathode. The commercialization of high-performance lithium–sulfur cells with high discharge capacity and cyclic stability requires the optimization of practical cell-design parameters. Herein, a carbon structural material composed of a carbon nanotube skeleton entrapping conductive graphene is synthesized as an electrode substrate. The carbon structural material is optimized to develop a high-loading polysulfide cathode with a high sulfur loading capacity (6–12 mg cm⁻²), rate performance (C/10–C/2), and cyclic stability for 200 cycles. A thin lithium anode based on the carbon structural material is developed and exhibits long lithium stripping/plating stability for ≈2500 h with a lithium-ion transference number of 0.68. A lean-electrolyte lithium–sulfur full cell with a low electrolyte-to-sulfur ratio of 6 µL mg⁻¹ is constructed with the designed high-loading polysulfide cathode and the thin lithium anode. The integration of all the critical cell-design parameters endows the lithium–sulfur full cell with a low negative-to-positive capacity ratio of 2.4, while exhibiting stable cyclability with an initial discharge capacity of 550 mAh g⁻¹ and 60% capacity retention after 200 cycles.     

Synthesis and electrochemical characteristics of Sn-Sb-Ni alloy composite anode for Li-ion rechargeable batteries

Micro-scaled Sn-Sb-Ni alloy composite was synthesized from oxides of Sn, Sb and Ni via carbothermal reduction. The phase composition and electrochemical properties of the Sn-Sb-Ni alloy composite anode material were studied. The prepared alloy composite electrode exhibits a high specific capacity and a good cycling stability. The lithiation capacity was 530 mAh g⁻¹ in the first cycle and maintained at 370-380 mAh g⁻¹ in the following cycles. The good electrochemical performance may be attributed to its relatively large particle size and multi-phase characteristics. The former reason leads to the lower surface impurity and thus the lower initial capacity loss, while the latter results in a stepwise lithiation/delithiation behavior and a smooth volume change of electrode in cycles. The Sn-Sb-Ni alloy composite material shows a good candidate anode material for the rechargeable lithium ion batteries.     

预嵌锂多壁碳纳米管的性能

使用稳定锂金属粉末(SLMP)/多壁碳纳米管(MWCNTs)作为负极、以活性炭(AC)作为正极组装锂离子电容器,研究其电化学性能。根据恒流充放电(GCD)和交流阻抗谱(EIS)研究了预嵌锂前后锂离子电容器的电化学性能。结果表明,嵌入适量的SLMP可消除碳纳米管大部分固有的不可逆容量并提高电容器的电化学性能。这种电容器具有较高的能量密度、功率密度和优异的循环性能。电流密度为0.05 A/g时预嵌锂碳纳米管锂离子电容器的比电容达到85.18 F/g,电流密度为0.05~4 A/g时最大能量密度和最大功率密度分别为140.4 Wh/kg和5.25 KW/kg,经过3000次循环后容量保持率仍约为82%。     

Two Birds One Stone: Graphene Assisted Reaction Kinetics and Ionic Conductivity in Phthalocyanine-Based Covalent Organic Framework Anodes for Lithium-ion Batteries

This work reports a covalent organic framework composite structure (PMDA-NiPc-G), incorporating multiple-active carbonyls and graphene on the basis of the combination of phthalocyanine (NiPc(NH₂)₄) containing a large π-conjugated system and pyromellitic dianhydride (PMDA) as the anode of lithium-ion batteries. Meanwhile, graphene is used as a dispersion medium to reduce the accumulation of bulk covalent organic frameworks (COFs) to obtain COFs with small-volume and few-layers, shortening the ion migration path and improving the diffusion rate of lithium ions in the two dimensional (2D) grid layered structure. PMDA-NiPc-G showed a lithium-ion diffusion coefficient (D_Li⁺) of 3.04 × 10⁻¹⁰ cm² s⁻¹ which is 3.6 times to that of its bulk form (0.84 × 10⁻¹⁰ cm² s⁻¹). Remarkably, this enables a large reversible capacity of 1290 mAh g⁻¹ can be achieved after 300 cycles and almost no capacity fading in the next 300 cycles at 100 mA g⁻¹. At a high areal capacity loading of ≈3 mAh cm⁻², full batteries assembled with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) and LiFePO₄ (LFP) cathodes showed 60.2% and 74.7% capacity retention at 1 C for 200 cycles. Astonishingly, the PMDA-NiPc-G/NCM-811 full battery exhibits ≈100% capacity retention after cycling at 0.2 C. Aided by the analysis of kinetic behavior of lithium storage and theoretical calculations, the capacity-enhancing mechanism and lithium storage mechanism of covalent organic frameworks are revealed. This work may lead to more research on designable, multifunctional COFs for electrochemical energy storage.     

PVDF-HFP基凝胶电解质用于LiNi0.5Co0.2Mn0.3O2三元正极锂离子电池

以聚偏氟乙烯-六氟丙烯(Poly(vinylidene fluoride-hexafluoropropylene),PVDF-HFP)为聚合物基体,新戊二醇二丙烯酸酯(Neopentyl glycol diacrylate,NPGDA)为交联剂,在引发剂偶氮二异丁腈(2,2′-Azobis(2-methylpropionitrile),AIBN)的作用下通过室温现场聚合法制备凝胶电解质用于锂离子电池。探索不同质量比PVDF-HFP/NPGDA对凝胶电解质性能和LiNi_(0.5)-Co_(0.2)Mn_(0.3)O_2三元正极锂离子电池性能的影响。结果表明,当质量比为1∶1时,凝胶电解质具有较高的离子电导率,为8.45mS·cm~(-1),锂离子迁移数为0.78,电化学窗口为4.5V。在电流密度30mA·g~(-1)恒流充放电,首次放电比容量为143mAh·g~(-1),循环50次后仍高达135.3mAh·g~(-1)。电流密度为300mA·g~(-1)时,放电比容量为100.2mAh·g~(-1)。     

Porous nanocrystalline TiO2 with high lithium-ion insertion performance

Porous nanocrystalline anatase TiO₂ was prepared by a modified hydrolytic route coupled with an intermediary amorphization/recrystallization process. The phase structure and morphology of the products were analyzed by X-ray diffraction, transmission electron microscopy, and field-emission scanning electron microscopy. The electrochemical properties were investigated by cyclic voltammetry, constant current discharge–charge tests, and electrochemical impedance techniques. Applied as an anode in a lithium-ion battery, the material exhibited excellent specific capacities of 130 mAh g^?1 (at the rate of 2000 mA g^?1) and 96 mAh g^?1 (at the rate of 4000 mA g^?1) after 100 cycles; the coulombic efficiency was ~99.5 %, indicating excellent rate capability and reversibility. Furthermore, the electrochemical impedance spectra showed improved electrode kinetics after cycling. These results indicate that the porous nanocrystalline TiO₂ synthesized by this improved synthesis route might be a promising anode material for high energy and high power density lithium-ion battery applications.     

Impact of CTAB on morphology and electrochemical performance of MoS<Subscript>2</Subscript> nanoflowers with improved lithium storage properties

The search for high capacity, low-cost electrode materials for lithium-ion batteries is a significant challenge in energy research. Among the numerous potential candidates, layered compounds such as MoS₂ (Molybdenum Disulfide) have attracted increasing attention. A facile hydrothermal reduction process using hexadecyltrimethy ammonium bromide (CTAB) as surfactant was developed for the synthesis of lithium-ion battery anode material MoS₂ nanoflowers. The impact of CTAB on morphology and electrochemical performance of MoS₂ has been investigated. With the increase of CTAB content, MoS₂ ultrathin nanosheets with high specific surface area and more active sites have been successfully synthesized. Electrochemical measurements demonstrated that MoS₂ nanoflowers synthesized with 1% content of CTAB have better electrochemical performance than others as anode materials for Li-ion batteries, which yield a high discharge capacity of 1245 mAh g^?1 at a current density of 50 mA g^?1 and a stable capacity retention of 740 mAh g^?1 until 100 electrochemical cycles.     

Electrochemical investigation on silicon/titanium carbide nanocomposite film anode for Li-ion batteries

A Si/TiC nanocomposite film was synthesized by a surface sol-gel method in combination with a following heat-treatment process. The electrochemical properties of the film anode for lithium ion batteries were investigated by galvanostatic charge-discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). Because of the homogeneous distribution of Si active particles in TiC matrix, the Si/TiC composite showed reversible lithium storage capacities of about 1000 and 1300 mAh g^− 1 at 160 and 80 mA g^− 1 even after 80 cycles, respectively. Using two-parallel diffusion path model, the reactive mechanisms of Li with Si/TiC composite film were interpreted. The chemical diffusion coefficients of the Si/TiC nanocomposite film at different electrode potentials were also discussed.     

Preparation and electrochemical performance of manganese oxide/carbon nanotubes composite as a cathode for rechargeable lithium battery with high power density

Manganese oxide/carbon nanotubes (MO/CNTs) composite was prepared by hydrothermally reducing KMnO₄ with CNTs, where the used CNTs are of dual role, i.e., they serve as reductant during reaction and the remaining CNTs act as conducting agent in the composite. This composite was characterized by X-ray diffraction and scanning electron microscopy techniques. In addition, the electrochemical performances of the composite were investigated, which suggested an excellent rate-capability of this material; e.g., it delivered a high discharge capacity as 131 mAh g^− 1 at a high current density of 4 A g^− 1 (20 C), and high capacity at low discharge current density, e.g., about 209 mAh g^− 1 at 0.2 C rate. Therefore, such a MO/CNTs composite is promising in high power application of lithium battery and electrochemical capacitor.     

Synthesis and characterisation of SnO2 nano-single crystals as anode materials for lithium-ion batteries

Rutile structure SnO₂ nano-single crystals have been synthesized using tin (IV) chloride as precursor by the modified hydrothermal method. Controllable morphology and size of SnO₂ could be obtained by adjusting the concentration of the hydrochloric acid. The SnO₂ nanoparticles were characterised by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical methods. The SnO₂ nanoparticles as anode materials in lithium-ion batteries exhibit high lithium storage capacities. The reversible capacities are more than 630 mA h g^− 1.     

Novel synthesis and electrochemical investigations of ZnO/C composites for lithium-ion batteries

For the first time, ZnO/C composites were synthesized using zinc glycerolate as a precursor through one-step calcination under a nitrogen atmosphere. The effect of the heat treatment conditions on the structure, composition, morphology as well as on the electrochemical properties regarding application in lithium-ion batteries are investigated. The products obtained by calcination of the precursor in nitrogen at 400—800 °C consist of zinc oxide nanoparticles and amorphous carbon that is in-situ generated from organic components of the glycerolate precursor. When used as anode material for lithium-ion batteries, the as-prepared ZnO/C composite synthesized at a calcination temperature of 700 °C delivers initial discharge and charge capacities of 1061 and 671 mAh g^?1 at a current rate of 100 mA g^?1 and hence 1.5 times more than bare ZnO, which reaches only 749/439 mAh g^?1. The native carbon improves the conductivity, allowing efficient electronic conductivity and Li-ion diffusion. By means of ex-situ XRD studies a two-step storage mechanism is proven.

     

Cathodic titania nanotube arrays as anode material for lithium-ion batteries

The titanium dioxide nanotube arrays (TNAs) have been synthesized at cathode and anode via standard electrochemical method for their subsequent use as anode material for lithium-ion batteries (LIBs). The TNAs fabricated at cathode have higher Ti³⁺ in comparison to TNAs at anode, which was confirmed using X-ray photoelectron spectroscopy and Raman spectrometry. Moreover, the lattice parameters of cathodic TNAs are estimated via Rietveld refinement of X-ray diffraction, which also conform to Ti³⁺ doping and insertion of protons (H⁺). The electrochemical impedance spectroscopy hints an increment in the electronic conductivity of TNAs fabricated at cathode. As a result, high reversible areal–specific capacity (~385.5 µAh cm^?2 at 100 µA cm^?2) with excellent rate capability is acquired by utilizing TNAs fabricated at cathode as anode material in LIBs.     

聚乙烯-乙烯醇磺酸锂/聚偏氟乙烯-六氟丙烯锂离子电池隔膜的制备及性能

以聚乙烯-乙烯醇的磺化物（EVOH-SO₃Li）和聚偏氟乙烯-六氟丙烯（PVDF-HFP）为原料,利用高压静电纺丝技术纺制成高孔隙率、纤维粗细均匀的EVOH-SO₃Li/PVDF-HFP复合隔膜材料。利用FTIR、SEM、万能拉伸试验仪、TGA、BMP3电化学工作站和电池检测系统对EVOH-SO₃Li/PVDF-HFP隔膜进行测试分析。测试结果表明:EVOH-SO₃Li/PVDF-HFP隔膜形成致密的三维网络结构,纤维粗细均匀,孔径均一,EVOH-SO₃Li/PVDF-HFP隔膜的孔隙率和吸液率分别为85%和437%;与纯EVOH-SO₃Li隔膜相比,EVOH-SO₃Li/PVDF-HFP复合隔膜的拉伸强度最大值从2.17 MPa提高至8.33 MPa,起始热分解温度升高至310℃,并表现出良好的电化学性能和电池性能。其中电化学稳定窗口由5.6 V增至5.8 V,界面阻抗由425.51 Ω降低至115.24 Ω,离子电导率由1.592×10-3 S/cm提高至3.102×10-3 S/cm;采用EVOH-SO₃Li/PVDF-HFP隔膜组装的锂离子电池在0.5 C放电电流下循环100次后容量保持率为96.65%。      

腐殖酸基石墨化材料的制备及其电化学性能

以腐殖酸为前驱体,通过高温热处理制备锂离子电池负极材料。采用扫描电子显微镜(SEM)、X射线衍射(XRD)和电化学测试系统对该材料的形貌、微晶结构和电化学性能进行表征。结果表明,腐殖酸基石墨化材料呈现出较为规整的石墨片层结构,且随着石墨化温度的升高,所得材料的石墨化度也越来越高。腐殖酸基石墨化材料均表现出良好的电化学性能,石墨化温度为2 800℃所制备的石墨化材料的首次放电比容量为356.7 mAh/g,充电比容量为277.6 mAh/g,首次充放电的库仑效率为77.81%,在1C和2C倍率下50次充放电循环后的容量保持率分别高达99.4%、95.9%,是一种理想的锂离子电池负极材料。     

Hollow hematite nanosphere/carbon nanotube composite: mass production and its high-rate lithium storage properties

Spray pyrolysis was used to produce hollow hematite (α-Fe(2)O(3)) nanosphere (HHNS)/carbon nanotube (CNT) composite on a large scale. The method offers simplicity, high productivity, versatility, low cost, and suitability for industry. The structure is composed of hollow nanospheres in a network of CNTs. The possible formation mechanism of hollow α-Fe(2)O(3) nanospheres is due to the rapid evaporation of water and the super-hydrophobicity of the CNT surface. The electrochemical tests show that the HHNS/CNT composite is a promising lithium storage material in terms of high capacity (～700 mAh g(-1)), good high-rate capability, and good cycle life (up to 150 cycles). The materials improve both lithium ion and electron transport, which are limiting factors on the high-rate capability of lithium-ion batteries. The production method can be easily adapted to produce a wide range of hollow metal oxide nanosphere/CNT composites.     

Carbon-nanofiber composite electrodes for thin and flexible lithium-ion batteries

Addition of vapor-grown carbon nanofiber (VGCF) into a LiCoO₂ composite electrode increases electrode’s conductivity and adhesion strength significantly. These increases are attributed to the uniform distribution of network-like VGCF of high conductivity; VGCF not only connects the surface of the active materials, its network penetrates into and connects each active material particle. VGCF composite electrode also improves the electrochemical performance of thin and flexible lithium-ion batteries such as discharge capacity at high current densities, cycle-life stability, and low-temperature (at −20 °C) discharge capacity. These improved electrochemical properties are attributed to the well-distributed network-like carbon nanofibers, VGCF, within the cathode. The addition of VGCF reduces the electron conducting resistance and decreases the diffusion path for lithium ions, hence increases the utilization of active materials during high-current discharge and low-temperature discharge. In addition, network-like VGCF forms a more uniform cathode structure so as to have a lower deterioration rate and correspondingly better life cycle stability.     

Glucose‐Induced Synthesis of 1T‐MoS2/C Hybrid for High‐Rate Lithium‐Ion Batteries

1T phase MoS₂ possesses higher conductivity than the 2H phase, which is a key parameter of electrochemical performance for lithium ion batteries (LIBs). Herein, a 1T‐MoS₂/C hybrid is successfully synthesized through facile hydrothermal method with a proper glucose additive. The synthesized hybrid material is composed of smaller and fewer‐layer 1T‐MoS₂ nanosheets covered by thin carbon layers with an enlarged interlayer spacing of 0.94 nm. When it is used as an anode material for LIBs, the enlarged interlayer spacing facilitates rapid intercalating and deintercalating of lithium ions and accommodates volume change during cycling. The high intrinsic conductivity of 1T‐MoS₂ also contributes to a faster transfer of lithium ions and electrons. Moreover, much smaller and fewer‐layer nanosheets can shorten the diffusion path of lithium ions and accelerate reaction kinetics, leading to an improved electrochemical performance. It delivers a high initial capacity of 920.6 mAh g^?1 at 1 A g^?1 and the capacity can maintain 870 mAh g^?1 even after 300 cycles, showing a superior cycling stability. The electrode presents a high rate performance as well with a reversible capacity of 600 mAh g^?1 at 10 A g^?1. These results show that the 1T‐MoS₂/C hybrid shows potential for use in high‐performance lithium‐ion batteries.     

Structure and electrochemical performance of ZnO/CNT composite as anode material for lithium-ion batteries

Metal oxides are well-known potential alternatives to graphite as anode materials of lithium-ion batteries, and they can deliver much higher reversible capacities than graphite even at high current densities. In this study, hexagonal disk-shaped ZnO are synthesized by a facile solution reaction of ZnCl₂ and its composite is prepared in the presence of carbon nanotubes (CNTs). The as prepared ZnO/CNT composite has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fourier transform-infrared spectroscopy and Rutherford backscattering spectroscopy. Electrochemical characterization by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge tests demonstrate that the conversion reactions in ZnO and ZnO/CNT electrodes enable reversible capacity of 478 and 602 mAh g^?1, respectively for up to 50 cycles. Our investigation highlights the importance of anchoring of small ZnO particles on CNTs for maximum utilization of electrochemically active ZnO and CNTs for energy storage application in lithium-ion batteries.