第一性原理在锂离子电池电极材料中的应用研究

在锂离子电池电极材料研究中，第一性原理计算能在理论上协助解释实验结果，为材料的合成和性能改进提供理论依据。目前第一性原理计算在锂离子电池电极材料中的应用主要集中在正极材料磷酸铁锂和层状氧化物LiMO₂(M=Ni, Co, Mn, Al等)材料中，对热门三元材料，特别是三元材料改性前后界面结构变化的研究较少。围绕密度泛函理论，综述了其在电极材料工作电压、电子传导性和离子扩散性、结构稳定性、储锂容量的计算以及热力学性能预测及解释等方面的应用，对较为集中的研究方向的进展进行阐述和总结，为用第一性原理进一步研究LiNi _x Co _y Mn_{1- x - y} O₂复合材料提供借鉴。     

Li6Zr2O7陶瓷粉体的高温固相法和静电纺丝法制备及结构分析

Li₆Zr₂O₇是一种含锂量高的化合物，在锂离子电池、核反应堆用氚增殖材料以及捕集CO₂的固体吸附剂等领域应用前景广泛。本文以水合氢氧化锂和水合硝酸氧锆为主要原料，采用高温固相法和静电纺丝法制备了锆酸锂材料。通过热重分析仪(TG)、X射线衍射(XRD)和扫描电子显微镜(SEM)等手段对样品的合成过程和结构进行了表征和分析，研究了锂锆比、煅烧温度和煅烧时间对产物物相和组织结构的影响。采用高温固相法，在锂锆摩尔比为3:1～6:1，煅烧温度为750℃和850℃，煅烧时间为24 h的条件下均成功制备出了单斜相的Li₆Zr₂O₇陶瓷粉体。采用静电纺丝法，在锂锆比为3:1，煅烧温度为800℃，煅烧时间为1 h的条件下制备出了纤维状Li₆Zr₂O₇和Li₂Zr O₃两相共存的陶瓷粉体。     

Li3PO4的生成条件研究及其对LiFePO4正极材料性能的影响

研究了磷酸铁锂(LiFePO₄)制造过程中共生磷酸锂(Li₃PO₄)的生产条件,总结出混料锂铁比例、研磨粒径以及烧结工艺对共生磷酸锂(Li₃PO₄)含量的影响规律。实验结果表明,Li/Fe比例>1.04,研磨粒度>1.0μm,烧成温度达到820℃条件下,容易造成磷酸铁锂中Li₃PO₄杂质的生成。实验证明,当磷酸铁锂中Li₃PO₄含量升高会带来LiFePO₄正极材料充放电性能和电阻的增大,不利于材料电化学性能的发挥。     

Li2MnO3复合LiNi0.8Co0.1Mn0.1O2材料制备及电化学性能研究

通过采用共沉淀法制备了Ni_0.8Co_0.1Mn_0.1（OH）₂前驱体,利用固相法研磨混合碳酸锰和碳酸锂,在氧气氛围下煅烧制备得到了Li₂MnO₃-LiNi_0.8Co_0.1Mn_0.1O₂复合材料,通过利用X射线衍射（XRD）、场发射扫描电镜（FESEM）和透射电镜（TEM）表征了所制备材料的结构、成分和形貌等。通过恒流充放电、交流阻抗等方法对材料的电化学性能进行测试。结果表明,与未改性材料进行对比,3%（质量分数）Li₂MnO₃复合改性材料0.5C下首次放电容量为183 mA·h/g,经过120次充放电循环,容量保持率为93.9%;同时,在高倍率下复合改性材料放电容量也得到提高。因此,采用固相法煅烧复合Li₂MnO₃-LiNi_0.8Co_0.1Mn_0.1O₂材料,可以制备出电化学性能优异的正极材料。     

应用于锂铝硅酸盐微晶玻璃的实用成核剂

锂铝硅酸盐(Li₂O-Al₂O₃-SiO₂,LAS)玻璃及微晶玻璃因其独特的理化性质而受到广泛研究。为实现LAS微晶玻璃的安全生产与应用，全面探究LAS玻璃的结晶机理和结晶过程具有重要意义。基于Li₂O-Al₂O₃-SiO₂微晶玻璃成核剂的作用机理，讨论了不同种类成核剂对Li₂O-Al₂O₃-SiO₂玻璃成核过程的影响，为Li₂O-Al₂O₃-SiO₂微晶玻璃的研发与实际生产提供指导。本文针对不同种类成核剂对LAS微晶玻璃的成核与生长过程影响进行了总结与归纳。     

四元体系硼酸锂-硼酸钾-硼酸镁-水在308.15 K时固液相平衡研究

采用等温溶解平衡法研究四元体系硼酸锂-硼酸钾-硼酸镁-水在308.15 K时固液相平衡,测定了体系溶解度和平衡液相的密度、折光率和pH。研究发现：该体系308.15 K时的稳定相图中包含一个共饱点（L+Li₂B₄O₇·3H₂O+K₂B₄O₇·4H₂O+Mg₂B₆O₁₁·15H₂O）,其液相组成：w（Li₂B₄O₇）=3.112%、w（K₂B₄O₇）=16.64%、w（Mg₂B₆O₁₁）=0.101 8%;3个固相结晶区：Li₂B₄O₇·3H₂O、K₂B₄O₇·4H₂O、Mg₂B₆O₁₁·15H₂O,体系无复盐或固溶体生成。溶液中硼酸锂、硼酸钾对多水硼镁石有很强的盐析效应,液相的密度、折光率和pH随溶液中硼酸盐浓度的增加呈规律性变化。     

LCBO助烧结剂在锂镧锆钽氧电解质烧结中的应用

使用基于Li₂CO₃-Li₃BO₃二元共熔体系的Li_2.3C_0.7B_0.3O₃助烧结剂辅助锂镧锆钽氧(LLZTO)电解质的烧结过程,并使用这种电解质与商业磷酸铁锂正极组装全电池研究其电化学性能。结果表明,LLZTO@LCBO固态电解质具备高离子电导率(5.1×10^-4S/cm)和优异的电化学性能,LiFePO4|LLZTO@LCBO|Li电池能够支持1C倍率下稳定充放电,在0.5C下充放电循环100次后,放电容量为124.6mAh/g,容量保持率为94.7%。     

混合碱效应对Li2O-Al2O3-SiO2系玻璃结构和热膨胀性能的影响

本文用传统高温熔融法熔制Li₂O-Al₂O₃-SiO₂系高铝玻璃,改变碱金属氧化物n(Li₂O)/n(Na₂O)的摩尔比,运用阿基米德排水法、热膨胀仪、DSC、傅里叶变换红外光谱和拉曼光谱等测试手段和仪器,探究了混合碱金属效应对Li₂O-Al₂O₃-SiO₂系玻璃结构和热膨胀性能的影响。结果显示:随着n(Li₂O)/n(Na₂O)比例增大,混合碱金属效应对Li₂O-Al₂O₃-SiO₂系玻璃的密度和热膨胀系数的影响一致,表现为先增大后减小,当R=0.25(R=n(Li₂O)/[n(Li₂O)+n(Na₂O)],摩尔比)时,出现极值,此时密度达到最大2.447 4 g/cm³,热膨胀系数达到最大7.811 7×10^-6/℃;对玻璃特征温度的影响随着温度的升高而逐渐减弱至消失;对玻璃的析晶能力有一定的提升作用;对玻璃三维骨架结构中的硅氧四面体Qⁿ的影响也各不相同。     

Li_xCoO_2(0≤x≤1)结构稳定性和力学性质的第一性原理计算

采用基于密度泛函的第一性原理,从电子层次计算研究了锂离子电池正极材料Li_xCoO_2(0≤x≤1)的晶体结构、电子结构和力学性质。结果表明:Li_xCoO_2在脱锂过程中晶体结构会发生转变,当x=0.5时由六方结构R ■ m晶型转变为单斜结构P2/m晶型,当完全脱锂(x=0)时又转变为六方结构P ■ m1晶型。随着Li原子的脱出,Li_xCoO_2导带被部分填充,价带被完全填充,金属性质和电子导电性增强,并出现自旋极化。Li_xCoO_2中Co—O键为含有部分离子性特征的共价键,随着Li原子的脱出,Co—O键的离子性特征减弱,共价性特征增强。随着Li原子的脱出,Li_xCoO_2的体积模量(B)、剪切模量(G)和弹性模量(E)均呈现逐渐减小的趋势,而Poisson比和各向异性指数逐渐增大。G/B值变化趋势表明,LiCoO_2呈脆性,脱锂过程中向韧性转变。     

废旧锂电池中有价金属回收及三元正极材料的再制备

探讨了磷酸体系下不同因素对废旧锂电池正极材料中有价金属浸出效率的影响，结果表明：在浸出时间60min，反应温度60℃，磷酸浓度2mol/L，液固比20mL/g，还原剂(H₂O₂)体积分数为4%时，可得最佳浸出效果，Co、Li、Mn、Ni浸出效率分别可达96.3%、100%、98.8%和99.5%；浸出液添加相应比例金属离子，采用草酸共沉淀法制备前体材料(Ni_1/3Co_1/3Mn_1/3)C₂O₄，并得到相应再生磷酸溶液。再生磷酸进行循环浸出实验，实验研究结果表明：循环浸出5次之后Li的浸出率仍可保持在90.1%，而Co、Mn和Ni的浸出率在75.0%以上。前体添加锂源Li₂CO₃煅烧合成Li(Ni_1/3Co_1/3Mn_1/3)O₂材料，考察了不同温度对Li(Ni_1/3Co_1/3Mn_1/3)O₂材料合成的影响，结果显示，当合成温度为800℃时，得到的材料性能最优良，初次放电容量可达136.4mA·h/g。在0.2C下经过50圈循环后容量保持率为97.2%。     

富锂锰基正极材料反应机理研究进展

富锂锰基正极材料xLi₂MnO₃·（1-x）LiMO₂（M=Ni,Co或Mn）具有比容量高（≥250 mA·h/g）和成本低的显著优势,近年来受到学术界和工业界的广泛关注。但是,关于材料的结构和反应机理等问题一直存在着一些争议。对富锂锰基材料的结构和反应机理进行了总结和评述。对材料的结构总结了单相固溶体、两相混和物、局部阳离子有序排列3种观点,通过分析发现富锂锰基材料的结构与元素的比例、制备条件等密切相关。反应机理重点阐述了材料的Li⁺/H⁺交换理论、阴离子氧氧化还原机理（阴离子电荷补偿理论）和Mn⁴⁺/Mn⁷⁺反应机理假说,并对阴离子氧氧化还原反应过程的中间产物是否存在O—O二聚体或者氧空穴进行了讨论分析。最后,对这类材料未来的产品化应用方向提出了展望,混掺使用可能是富锂锰基材料产业化的切入点,高性价比的富锂锰基材料的产业化应用将再一次推动锂离子电池发展迈向一个新台阶。     

Preparation and evaluation of α-Al2O3 supported lithium ion sieve membranes for Li+ extraction

Spinel lithium manganese oxide ion-sieves have been considered the most promising adsorbents to extract Li⁺ from brines and sea water. Here, we report a lithium ion-sieve which was successfully loaded onto tubular α-Al₂O₃ ceramic substrates by dipping crystallization and post-calcination method. The lithium manganese oxide Li₄Mn₅O₁₂ was first synthesized onto tubular α-Al₂O₃ ceramic substrates as the ion-sieve precursor (i.e. L-AA), and the corresponding lithium ion-sieve (i.e. H-AA) was obtained after acid pickling. The chemical and morphological properties of the ion-sieve were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Both L-AA and H-AA showed characteristic peaks of α-Al₂O₃ and cubic phase Li₄Mn₅O₁₂, and the peaks representing cubic phase could still exist after pickling. The lithium manganese oxide Li₄Mn₅O₁₂ could be uniformly loaded not only on the surface of α-Al₂O₃ substrates but also inside the pores. Moreover, we found that the equilibrium adsorption capacity of H-AA was 22.9 mg·g^-1. After 12 h adsorption, the adsorption balance was reached. After 5 cycles of adsorption, the adsorption capacity of H-AA was 60.88% of the initial adsorption capacity. The process of H-AA adsorption for Li⁺ correlated with pseudo-second order kinetic model and Langmuir model. Adsorption thermodynamic parameters regarding enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS) were calculated. For the dynamic adsorption- desorption process of H-AA, the H-AA exhibited excellent adsorption performance to Li⁺ with the Li⁺ dynamic adsorption capacity of 9.74 mg·g^-1 and the Mn²⁺ dissolution loss rate of 0.99%. After 3 dynamic adsorption-desorption cycles, 80% of the initial dynamic adsorption capacity was still kept.     

Electrolytic production of NF3 with a LiNiO2 coated nickel sheet anode prepared by atmospheric plasma spraying technique

A nickel sheet coated with LiNiO₂ powder having average particle sizes of 40 and 50 μm in diameter by atmospheric plasma spraying technique was employed as the anode for electrolytic production of NF₃. In electrolysis of a molten NH₄F·2HF at 100 °C and 25 mA cm⁻², the anode gas generated at the LiNiO₂ coated Ni sheet anode was composed of N₂, O₂, NF₃, N₂F₂, N₂F₄, and N₂O, and its composition was almost the same as that at the Ni sheet anode. The current efficiency for the NF₃ formation on the LiNiO₂ coated Ni sheet anode was increased to reach the constant value of ca. 55% during electrolysis for 100 h, and it was almost the same as that on the Ni sheet anode. The anode consumption of the LiNiO₂ coated Ni sheet was small compared with that of the Ni sheet. Also, the oxygen content in the oxidized layer formed on the LiNiO₂ coated Ni sheet anode was high compared with that on the Ni sheet anode, and the surface of the LiNiO₂ coated Ni sheet anode was covered with a compact and adhesive film having some defects. Although the bottom of the hollow was covered with a thinner layer, no pore penetrated through the oxidized layer. Hence, the LiNiO₂ coated Ni sheet anode is favorable for the electrolytic production of NF₃, and the oxidized layer on the LiNiO₂ coated Ni sheet anode has the higher resistance to corrosion, because of the compact and adhesive film containing the higher content of oxygen formed on the anode.     

锂离子电池正极材料铌掺杂LiNiO2 的制备与电化学性能

为了提高LiNiO₂的电化学性能,用固相反应法制备了铌掺杂LiNiO₂材料,并用X射线衍射（XRD）分析、恒电流滴定技术（GITT）、电化学阻抗谱（EIS）等方法研究铌掺杂量对LiNiO₂的结构和性能的影响。结果表明适量的铌（Nb）掺杂可以提高LiNiO₂层状结构的有序程度,降低Li⁺/Ni²⁺混合程度,降低电荷转移阻抗,提高活性材料中锂离子的扩散系数。其中LiNi_0.99Nb_0.01O₂在0.5C循环100次的容量保持率为91.4%,5C时放电比容量为143 mA·h/g。而未掺杂铌的LiNiO₂在相同条件下的容量保持率和比容量仅为69.2%和127 mA·h/g。结果说明铌掺杂能够有效提高LiNiO₂的电化学性能。     

Efficiency enhancement in dye-sensitized solar cells by in situ passivation of the sensitized nanoporous electrode with Li2CO3

This work entails a method to improve the performance of dye-sensitized nanocrystalline TiO₂ solar cells by adding surface passivating elements to the electrolyte. The presence of either CO₂, Li₂CO₃ or K₂CO₃ in electrolyte increases both the photocurrent and the photovoltage, resulting in higher overall conversion efficiency of these solar cells. The additives are used to form a passivation layer of lithium carbonate on the dye free surface of the TiO₂ nanoparticles and the conductive substrate. This layer suppresses the rate of the main recombination reaction between the photoinjected electrons and the oxidized ions in the electrolyte solution. While blocking part of the recombination, the lithium carbonate layer allows motion of the Li⁺ ions towards the TiO₂ surface for charge screening. Consequently using this simple treatment, the conversion efficiency of dye-sensitized solar cell most improved by 17.2% (from 6.4% to 7.5%).     

Li3PO4掺杂的Li(Ni0.5Co0.2Mn0.3)O2锂离子电池正极材料的流变相法合成及电化学性能表征

采用氢氧化物共沉淀法制备了锂离子电池正极材料前驱体(Ni_0.5Co_0.2Mn_0.3)(OH)₂,并用流变相反应法合成了Li₃PO₄掺杂的Li(Ni_0.5Co_0.2Mn_0.3)O₂锂离子电池正极材料。运用X射线粉末衍射和恒电流充放电对产物进行了结构和电化学性能的表征,结果表明Li₃PO₄掺杂的Li(Ni_0.5Co_0.2Mn_0.3)O₂具有标准的层状α-NaFeO₂结构,样品为1 μm左右的片状一次颗粒聚集而成的类球形二次颗粒。掺杂1%(质量分数)Li₃PO₄的Li(Ni_0.5Co_0.2Mn_0.3)O₂锂离子电池在0.1C的倍率下首次放电比容量达到188.6 mA·h·g^-1(2.2～4.6 V vs Li⁺/Li),30次循环后容量保持率为 92.9%。循环伏安、交流阻抗测试表明Li₃PO₄的掺杂可减少充放电过程中电解液和电极之间的电荷传递电阻和锂离子扩散电阻,减小极化作用,从而提升了Li(Ni_0.5Co_0.2Mn_0.3)O₂材料的电化学性能。     

纳米片多面体锰基锂离子筛的制备及锂离子吸脱附特性

针对锰基锂离子筛容量发挥不充分、使用寿命短的问题,以电解二氧化锰、氯化锂及无水氯化铝为原料,采用水热法合成了铝原子掺杂锰基离子筛前驱体,经酸洗脱附锂离子后得到锰基锂离子筛H_1.6（Mn_1-x Al _x ）_1.6O₄。扫描电镜结果表明,铝原子掺杂后,样品呈均匀光滑的纳米片多面体形貌,进一步的吸脱附等温线分析显示,样品的比表面积显著提高。锂离子吸脱附特性研究结果表明,Li_1.6（Mn_0.7Al_0.3）_1.6O₄具有最佳的吸附提锂性能,锂离子溶液初始质量浓度为80 mg/L时,吸附容量为32.32 mg/L,5次循环提锂后,锂离子吸附容量可保持为初始吸附容量的95%。这些结果表明,结晶性好、比表面积大的纳米多面体锰基锂离子筛,吸附容量大、结构稳定性好,可为当前盐湖卤水中锂资源的开发和工艺优化提供技术参考。     

四元体系（Li+， Mg2+//Cl-， borate-H2O）308.15 K相平衡与相图研究

采用等温溶解平衡法,开展四元体系Li⁺, Mg²⁺//Cl^-, borate–H₂O固液相平衡与相图研究,测定平衡溶液的液相组成、密度、折射率和pH。该四元体系相图中存在的盐类矿物为：LiCl·H₂O、Li₂B₄O₇·3H₂O、 MgCl₂·6H₂O、Mg₂B₆O₁₁·15H₂O和锂光卤石LiCl·MgCl₂·7H₂O,其中锂光卤石LiCl·MgCl₂·7H₂O是异成分复盐,溶液中MgCl₂存在下章氏硼镁石（MgB₄O₇·9H₂O）不稳定,转化为多水硼镁石（Mg₂B₆O₁₁·15H₂O）。多水硼镁石结晶区最大,表明镁硼酸盐易于结晶析出,而锂光卤石结晶区最小。采用Pitzer热力学模型对该四元体系的溶解度进行理论预测,计算相图与实验相图吻合较好。该四元体系的稳定相平衡与相图研究,可为含锂硼盐湖老卤中锂、镁、硼产品开发及其综合利用提供理论依据。     

Anomalous Dielectric Behaviour in Melt Quenched Lithium Borate Glasses

Transparent glasses of lithium tetraborate (Li₂B₄O₇) were prepared by a splat quenching technique. X-ray powder diffraction (XRD) and high resolution transmission electron microscopic studies revealed the amorphous nature of the as-quenched samples. The glassy nature of these samples was confirmed by differential thermal analysis. Physical properties such as density, dielectric and ac conductivity have been studied. Glasses of Li₂B₄O₇ exhibit a dielectric anomaly close to the crystallization temperature which is attributed to the interfacial polarization caused by Li⁺ ion motion within the borate network.