Visual and colorimetric lithium ion sensing based on digital color analysis

A new optical analytical method, "Digital Color Analysis (DCA)", is proposed based on a digital color analyzer instead of the conventional optical methodology, "Spectrophotometry". The digital color analyzer is a hand-held-size instrument for measuring "colors", and it can transform the color information into numerical values, color library data, etc., that can be treated as analytical information. DCA gives us a more informative analytical method than spectrophotometry by treating colors as digital information. In addition, DCA can also simulate the optimum color variations for optimization of the visual sensor with computer assistance. By utilizing colors as digital information, colorimetric analysis that has been used for only semiquantitative analysis can serve as an accurate determination method. On the basis of DCA, we developed a plasticized PVC film optode and a paper optode for Li+ determination in saliva. After the optimization of color variation and the detection range for the Li+ measurements, the optode membrane gives colorless gray in the Li+ therapeutic range (at 10(-3) M) in saliva. Consequently, whether or not the optimum therapeutic Li+ concentration is maintained can be easily evaluated with these optodes. Especially, the sensing paper optode can be easily handled within a short measurement time (approximately 80 s) which is suitable for home use. Using the digital color analyzer with QxQy coordinates, a linear relation calibration curve can be obtained over the range from 10(-5) to 10(-1) M Li+, in which the analyzer can detect a concentration difference of approximately 0.1 mM Li+. For the near future, an accurate and simple analysis is needed for a health check at home that does not require going to a hospital. The optode based on DCA has great potential for this analytical purpose.     

Study on thermal behaviors of Li/H atom in the bulk graphite by molecular dynamics method

A system with periodical structure of graphite, in which a Li or H atom is set in the center of the supercell, has been simulated by molecular dynamics method to study the thermal diffusion of Li and H in the bulk graphite. It is found that the rates of diffusion of both Li and H atoms increase with the increase of the simulation temperature: from 50 K to 200 K, and the specific diffusive rates and behaviors for Li and H are different according to their trajectories. The diffusive curves for Li can be classified into three types, while H has only one type of diffusive curve, which shows that the interaction between Li and carbon is weaker than that between H and carbon. The conductive band gap of graphite is also calculated by the extended Hückel method. The gap is broadened by about 0.1 eV when graphite is intercalated with H, but the gap remains unchanged when graphite is intercalated with Li. It indicates that the addition of Li does not influence the conduction characteristic of graphite while that of H does. Thus Li-GIC (Graphite Intercalated Compound) is proposed to be a favorable material for the electrode.     

An Electron/Ion Dual‐Conductive Alloy Framework for High‐Rate and High‐Capacity Solid‐State Lithium‐Metal Batteries

The solid‐state Li battery is a promising energy‐storage system that is both safe and features a high energy density. A main obstacle to its application is the poor interface contact between the solid electrodes and the ceramic electrolyte. Surface treatment methods have been proposed to improve the interface of the ceramic electrolytes, but they are generally limited to low‐capacity or short‐term cycling. Herein, an electron/ion dual‐conductive solid framework is proposed by partially dealloying the Li–Mg alloy anode on a garnet‐type solid‐state electrolyte. The Li–Mg alloy framework serves as a solid electron/ion dual‐conductive Li host during cell cycling, in which the Li metal can cycle as a Li‐rich or Li‐deficient alloy anode, free from interface deterioration or volume collapse. Thus, the capacity, current density, and cycle life of the solid Li anode are improved. The cycle capability of this solid anode is demonstrated by cycling for 500 h at 1 mA cm^?2, followed by another 500 h at 2 mA cm^?2 without short‐circuiting, realizing a record high cumulative capacity of 750 mA h cm^?2 for garnet‐type all‐solid‐state Li batteries. This alloy framework with electron/ion dual‐conductive pathways creates the possibility to realize high‐energy solid‐state Li batteries with extended lifespans.     

An ICP-OES method with 0.2% expanded uncertainties for the characterization of LiA1O2

An improved inductively coupled plasma-optical emission spectrometry (ICP-OES) method has been applied to the determination of Li and A1 mass fractions and the Li/A1 amount-of-substance ratio in representative samples of LiA1O2. This ICP-OES method has uncertainty on the order of 0.2%,(2,3) comparable to the best analytical methods. This method is based on several strategies, which are detailed in this work. The mean measured mass fractions of Li and A1 in eight samples were 0.10151 +/- 0.00016 (+/-0.16%) and 0.41068 +/- 0.00056 (+/-0.14%), and the mean Li/A1 amount-of-substance ratio was 0.9793 +/- 0.0017 (+/-0.17%). The uncertainty is dominated by sample handling and heterogeneity-about a factor of 2 larger than the ICP-OES instrumental uncertainties, which were 0.04% for A1 and 0.07% for Li.     

Controlling Nucleation in Lithium Metal Anodes

Rechargeable batteries are regarded as the most promising candidates for practical applications in portable electronic devices and electric vehicles. In recent decades, lithium metal batteries (LMBs) have been extensively studied due to their ultrahigh energy densities. However, short lifespan and poor safety caused by uncontrollable dendrite growth hinder their commercial applications. Besides, a clear understanding of Li nucleation and growth has not yet been obtained. In this Review, the failure mechanisms of Li metal anodes are ascribed to high reactivity of lithium, virtually infinite volume changes, and notorious dendrite growth. The principles of Li deposition nucleation and early dendrite growth are discussed and summarized. Correspondingly, four rational strategies of controlling nucleation are proposed to guide Li nucleation and growth. Finally, perspectives for understanding the Li metal deposition process and realizing safe and high‐energy rechargeable LMBs are given.     

Conformal coating of thin polymer electrolyte layer on nanostructured electrode materials for three-dimensional battery applications

Various three-dimensional (3D) battery architectures have been proposed to address effective power delivery in micro/nanoscale devices and for increasing the stored energy per electrode footprint area. One step toward obtaining 3D configurations in batteries is the formation of core-shell nanowires that combines electrode and electrolyte materials. One of the major challenges however in creating such architectures has been the coating of conformal thin nanolayers of polymer electrolytes around nanostructured electrodes. Here we show conformal coatings of 25-30 nm poly(methyl methacralate) electrolyte layers around individual Ni-Sn nanowires used as anodes for Li ion battery. This configuration shows high discharge capacity and excellent capacity retention even at high rates over extended cycling, allowing for scalable increase in areal capacity with electrode thickness. Our results demonstrate conformal nanoscale anode-electrolyte architectures for an efficient Li ion battery system.     

支撑层对PDMS复合膜渗透汽化性能的影响

以相转化法制备的聚偏氟乙烯(PVDF)、聚丙烯腈(PAN)、聚砜(PSF)三种多孔膜作为支撑层,制备聚二甲基硅氧烷(PDMS)复合膜用于渗透汽化乙醇/水混合物的分离。采用能量色散X射线光谱仪(EDX)定量表征了PDMS在支撑层表面的厚度(L0)和支撑层内的渗入深度(Li),研究发现,PDMS在各支撑层表面的厚度、支撑层内渗入的厚度有显著差异,PDMS复合膜的渗透通量与(L0+Li)间存在近似的线性关系,表明PDMS在支撑层中渗入深度不同是造成不同底膜支撑的PDMS复合膜渗透汽化性能差异的根本原因。文中提出选择层总厚度(Lt=L0+Li)概念,通过线性拟合得到PDMS复合膜渗透通量与Lt之间的定量关系,可以用来估算PDMS复合膜的渗透通量,并预测复合膜渗透通量极大值。     

Mixed Ionic and Electronic Conductor for Li‐Metal Anode Protection

Li‐metal is the optimal choice as an anode due to its highest energy density. However, Li‐anodes suffer safety problems from dendritic Li‐growth and continuous corrosion by liquid electrolytes. Here, an effective strategy of using ultrathin and conformal mixed ionic and electronic ceramic conductor (MIEC) is proposed to stabilize Li‐anodes. An ultrathin Li_0.35La_0.52[V]_0.13TiO₃ (LLTO) ceramic film with superior ionic conductivity is first obtained by sintering single‐crystal LLTO nanoparticles, which have controlled surface facets and particle sizes. Then the MIEC property is developed in the LLTO film by introducing toluene as catalyst, which triggers the chemical reactions between LLTO and Li‐metal, leading to high electronic conductivity in the LLTO film. After evaporating toluene, a hybrid LLTO/Li anode with a conformal and stable interface is formed. When applying the hybrid anodes in Li‐metal batteries, the MIEC ceramic film blocks Li‐corrosion from electrolyte and the formation of Li‐dendrites by buffering the Li‐ion concentration gradient and leveling secondary current distribution on Li‐metal surface. At the same time, the Coulombic efficiency of batteries reaches to 98%. This finding will impact the general approach for tailoring the properties of Li‐metal anodes for achieving better Li‐metal battery performance.     

The Mechanism of Li Deposition on the Cu Substrates in the Anode-Free Li Metal Batteries

Due to the rapid growth in the demand for high-energy-density Lithium (Li) batteries and insufficient global Li reserves, the anode-free Li metal batteries are receiving increasing attention. Various strategies, such as surface modification and structural design of copper (Cu) current collectors, have been proposed to stabilize the anode-free Li metal batteries. Unfortunately, the mechanism of Li deposition on the Cu surfaces with the different Miller indices is poorly understood, especially on the atomic scale. Here, the large-scale molecular dynamics simulations of Li deposition on the Cu substrates are performed in the anode-free Li metal batteries. The results show that the surface properties of the Li panel can be altered through the different Cu substrate surfaces. Through surface similarity analysis, potential energy distributions,and inhomogeneous deposition simulations, it is found that the Li atoms exhibit different potential energy variances and kinetic characteristics on the different Cu surfaces. Furthermore, a proposal to reduce the fraction of the (110) facet in commercial Cu foils is made to improve the reversibility and stability of Li plating/stripping in the anode-free Li metal batteries.     

A Natural Biopolymer Film as a Robust Protective Layer to Effectively Stabilize Lithium‐Metal Anodes

Li metal is considered as an ideal anode for Li‐based batteries. Unfortunately, the growth of Li dendrites during cycling leads to an unstable interface, a low coulombic efficiency, and a limited cycling life. Here, a novel approach is proposed to protect the Li‐metal anode by using a uniform agarose film. This natural biopolymer film exhibits a high ionic conductivity, high elasticity, and chemical stability. These properties enable a fast Li‐ion transfer and feasiblity to accomodate the volume change of Li metal, resulting in a dendrite‐free anode and a stable interface. Morphology characterization shows that Li ions migrate through the agarose film and then deposit underneath it. A full cell with the cathode of LiFPO₄ and an anode contaning the agarose film exhibits a capacity retention of 87.1% after 500 cycles, much better than that with Li foil anode (70.9%) and Li‐deposited Cu anode (5%). This study provides a promising strategy to eliminate dendrites and enhance the cycling ability of lithium‐metal batteries through coating a robust artificial film of natural biopolymer on lithium‐metal anode.     

A Novel Organic “Polyurea” Thin Film for Ultralong‐Life Lithium‐Metal Anodes via Molecular‐Layer Deposition

Metallic Li is considered as one of the most promising anode materials for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. However, its commercialization has been impeded by the severe safety issues associated with Li‐dendrite growth. Non‐uniform Li‐ion flux on the Li‐metal surface and the formation of unstable solid electrolyte interphase (SEI) during the Li plating/stripping process lead to the growth of dendritic and mossy Li structures that deteriorate the cycling performance and can cause short‐circuits. Herein, an ultrathin polymer film of “polyurea” as an artificial SEI layer for Li‐metal anodes via molecular‐layer deposition (MLD) is reported. Abundant polar groups in polyurea can redistribute the Li‐ion flux and lead to a uniform plating/stripping process. As a result, the dendritic Li growth during cycling is efficiently suppressed and the life span is significantly prolonged (three times longer than bare Li at a current density of 3 mA cm^?2). Moreover, the detailed surface and interfacial chemistry of Li metal are studied comprehensively. This work provides deep insights into the design of artificial SEI coatings for Li metal and progress toward realizing next‐generation Li‐metal batteries.     

Directing Highly Ordered and Dense Li Deposition to Achieve Stable Li Metal Batteries

Li metal anode is promising to achieve high-energy-density battery. However, it has rapid capacity fading due to the generation of inactive Li (dead Li), especially at high current density. This study reveals that the random distribution of Li nuclei leads to large uncertainty for the further growth behavior on Cu foil. Here, periodical regulation of Li nucleation sites on Cu foil by ordered lithiophilic micro-grooves is proposed to precisely manipulate the Li deposition morphology. The management of Li deposits in the lithiophilic grooves can induce high pressure on the Li particles, leading to the formation of dense Li structure and smooth surface without dendrite growth. Li deposits comprising tightly packed large Li particles largely reduce the side reaction and the generation of isolated metallic Li at high current density. Less dead Li accumulating on the substrate significantly prolongs the cycling life of full cells with limited Li inventory. The precise manipulation of the Li deposition on Cu is promising for high-energy and stable Li metal batteries.     

In Situ Solid Electrolyte Interphase from Spray Quenching on Molten Li: A New Way to Construct High‐Performance Lithium‐Metal Anodes

Uncontrollable growth of Li dendrites and low utilization of active Li severely hinder its practical application. Construction of an artificial solid electrolyte interphase (SEI) on Li is demonstrated as one of the most effective ways to circumvent the above problems. Herein, a novel spray quenching method is developed in situ to fabricate an organic–inorganic composite SEI on Li metal. By spray quenching molten Li in a modified ether‐based solution, a homogeneous and dense SEI consisting of organic matrix embedded with inorganic LiF and Li₃N nanocrystallines (denoted as OIFN) is constructed on Li metal. Arising from high ionic conductivity and strong mechanical stability, the OIFN can not only effectively minimize the corrosion reaction of Li, but also greatly suppresses the dendrite growth. Accordingly, the OIFN‐Li anode presents prominent electrochemical performance with an enhanced Coulombic efficiency of 98.15% for 200 cycles and a small hysteresis of <450 mV even at ultrahigh current density up to 10 mA cm^?2. More importantly, during the full cell test with limited Li source, a high utilization of Li up to 40.5% is achieved for the OIFN‐Li anode. The work provides a brand‐new route to fabricate advanced SEI on alkali metal for high‐performance alkali‐metal batteries.     

Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator

The uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO₃ nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO₃ nanoparticles and the polar solvent reduces the ionic radius of the Li⁺-solvent complex, thus increasing the Li⁺ transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO₃ nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi₂ at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.     

面向可充电电池的锂金属负极的枝晶生长:理论基础、影响因素和抑制方法

在全球能源与环境问题日趋紧迫的大背景下,可再生能源的获取与利用途径及高效安全的储能技术的研发一直是工业界和科学界关注的热点之一。锂离子二次电池作为能量存储器件,拥有高比能量、长循环寿命等优点,近十几年来其研究取得了长足进展,并在各类便携式电子设备和电动交通工具中获得了广泛应用。然而,随着各种高性能设备的不断涌现,商业化的锂离子电池越来越难以满足其在能量密度、循环稳定性和安全性等方面的要求。为了进一步提高锂离子电池的能量密度,需要开发出高比容量的负极材料(硅、锡和锂等)以取代传统石墨负极。硅、锡等新式负极材料通过与锂离子反应形成含锂化合物的原理来存储与释放锂离子,完成电池的一个充放电过程。这个过程往往伴随着负极材料体积的剧烈变化,经历较长时间循环使用后会导致负极材料的粉化甚至从集流体上剥离,引起电池容量迅速衰减甚至失效。而锂负极通过锂在负极上的溶解和沉积来完成电池的充放电过程,该过程不存在反应相变所导致的体积变化。另外,锂金属负极材料具有极高的质量比容量(3 860mAh/g)、低密度(0.59g/cm3)和低的还原电位(-3.04V,相比于氢标准电极),被认为是一种理想的可充电电池负极材料。然而,锂的枝晶生长、锂金属电池低的库伦效率和锂的无主体沉积引起的体积膨胀等一些关键问题长期以来制约着锂负极的商业应用。锂的每次沉积都会产生枝晶,在充放电循环中,锂枝晶会导致电池内部短路甚至发生爆炸,带来严重的安全问题。除此之外,锂枝晶还会增加负极表面积,新暴露的锂金属会与电解液反应生成固态电解质膜(Solid electrolyte interface,SEI),这会损耗活性材料以及降低电池的库伦效率。为了解决以上问题,研究者们对锂金属电极进行了许多探索,尤其是在锂枝晶生长的机理及其抑制方法方面。一些理论模型如扩散模型、SEI保护模型、电荷诱导生长模型和薄膜生长模型等,以及与这些模型相对应的一些抑制方法如均匀锂离子流法、SEI膜保护法、稳定沉积主体法和静电屏蔽保护法等被提出。这些抑制方法能够在一定程度上缓解锂枝晶的生长问题,但都未能达到商业化应用的要求。本文总结了近几年研究人员针对锂离子电池锂金属负极的一些重要研究,系统地介绍了业内较为认同的枝晶生长模型和影响因素,并着重叙述了抑制枝晶生长的方法及成效,最后就锂金属负极将来的研究方向给出一些建议。     

水平集在盐水白带细胞显微图像分割中的应用

盐水白带细胞种类繁多成分复杂,细胞存在弱边缘、相互交织和面积小不易区分等特点,加之受杂质的影响,都给细胞分割带来困难.为此本文采用一种新的水平集方法,解决了传统水平集方法的演化曲线难以探测到细胞弱边缘的问题,而且这种水平集方法避免了重新初始化符号距离函数减少了计算量.实验结果表明,这种方法的演化曲线可以探测到细胞弱边缘,能够对盐水白带细胞显微图像进行分割.     

Reversible Deposition of Lithium Particles Enabled by Ultraconformal and Stretchable Graphene Film for Lithium Metal Batteries

Originating from inhomogeneous Li deposition and dissolution, the formation of dendritic and/or dead Li lies as a fundamental barrier to the practical implementation of Li metal anodes for high-energy Li-ion batteries. Here, an ultraconformal and stretchable solid-electrolyte interphase (SEI) composed of parallelly stacked few-layer defect-free graphene nanosheets, which can deform to remain ultraconformal during the expansion and shrinkage of micro-sized Li metal particles is reported. The shape-adaptive graphene protective skin is prepared via a facile mechanical method followed by Li stripping, which enables fast Li-ion diffusion, and inhibits Li dendrites and Li pulverization. The interlayer slips and wrinkles of the graphene film endow the robust protective skin with high stretchability. This work represents a unique strategy of building ultraconformal and stretchable 2D-materials-based protective skins on the surface of Li metal toward high-energy, long-life, and safe Li metal batteries.     

Li4Ti5O12／C复合负极材料的一步固相合成及不同碳源的影响

采用固相合成的方法，以Li2CO3，TiO2为原料，分别以葡萄糖、柠檬酸、聚丙烯及三者的混合物作为碳源一步烧结合成了亚微米级的Li4Ti5O12／c复合负极材料,XRD结果显示其具有理想的尖晶石结构。研究结果表明，以葡萄糖作为碳源制备的Li4Ti5O12／c材料的性能最佳，其碳含量最高，为2．07％，0.5c和1c倍率下的放电容量分别达到了220和191mAh／g。     

Determination of the cascade summation coefficients of gamma quanta for a semiconductor detector in the 59–2754 keV range

A method of measuring the cascade summation coefficients of a semiconductor Ge(Li)-detector with a relative efficiency of 15% without using calculation programs is proposed. An uncertainty of 2% (k = 2) in the cascade summation coefficients obtained for energies of 59–2754 keV is obtained. A method of constructing the overall efficiency curve of the detector up to an energy of 2754 keV using ⁶⁰Co, ⁸⁸Y, and ²⁴Na radionuclides is proposed. The measured cascade summation coefficients are compared with those calculated using the ETNA program (LNHB, France). __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 58–62, September, 2006.     

Computationally efficient two-dimensional direction-of-arrival estimation of electromagnetic sources using the propagator method

The authors develop a propagator-based algorithm for two-dimensional (2D) direction finding of electromagnetic sources under spatially correlated noise here. The planar-plus-an-isolated array geometry, first defined by Li et al. (1996) is adopted. The authors propose to replace the planar pressure-sensors in Li et al. (1996) by electromagnetic vector sensors, thus exploiting the benefits inherent in the additional measurements made by a vector sensor. Compared with the algorithm in Li et al. (1996), the presently proposed algorithm can offer closed-form automatically paired azimuth-elevation angle estimates, without costly 2D iterative searching. Moreover, the proposed algorithm can achieve the unambiguous direction estimates with enhanced accuracy by setting the planar electromagnetic vector sensors to space much farther apart than a half-wavelength. Therefore the proposed algorithm constitutes a distinct improvement over (Li et al., 1996).