钛酸锂基锂离子电池及其健康状态研究进展

锂离子电池的高功率密度和高能量密度等特性使其成为电动汽车能源和新能源电网储能的重要载体。功率性能和安全特性是锂离子电池发展的两个主要挑战。钛酸锂Li₄Ti₅O₁₂材料因具有良好的结构稳定性、安全性能、长循环寿命、高功率特性和高低温放电性能,被认为是锂电池负极材料的良好备选。综述了以钛酸锂材料为负极的锂离子电池的相关工作,介绍了钛酸锂材料的结构、电化学特性、制备方法和作为电池负极材料面临的主要问题,重点介绍了钛酸锂负极电池的全电池性能和健康状态研究等方面。     

锂电池百篇论文点评(2020.10.01—2020.11.30)

该文是一篇近两个月的锂电池文献评述,以"lithium"和"batter*"为关键词检索了Web of Science从2020年10月1日至2020年11月30日上线的锂电池研究论文,共有2731篇,选择其中100篇加以评论.层状正极材料主要研究了高镍三元材料和富锂相材料中的氧氧化还原机制,掺杂和表面包覆是常用的改性方法.硅基复合负极材料的研究重点包括负极嵌锂的体积膨胀问题以及通过引入新的黏结剂和在材料表面预形成SEI等方法提升材料的循环性能,有关负极的研究工作还包括Ti2Nb10O29负极、还原氧化石墨烯及其复合材料负极、三维碳负极材料等.电解液添加剂的研究包括适用于高电压三元材料、富锂材料、高电压磷酸钴锂材料、锂硫电池和厚电极的功能电解液添加剂.固态电解质的研究对象涵盖硫化物固体电解质、聚合物与硫化物/氧化物固体电解质复合材料、硅掺杂的Li6PS5I和硼酸锂掺杂的Li7La3Zr2O12等.无机电解质和无机/聚合物复合电解质固态电池、锂硫和锂空气电池的论文也有几篇.表征分析偏重于固液界面SEI、金属锂沉积过程、锂在电极中的空间分布he1电池气胀问题等.理论模拟工作涉及SEI形成机制以及厚电极电池的动力学等.     

Preparation and research for Li4Ti5O12/AC-based hybrid supercapacitors

尖晶石型Li4Ti5O12因其长循环寿命、高功率以及宽工作温度特性,现已成为新一代超级电容器的重点发展方向。本工作分别选用商品化活性炭、钛酸锂为正、负电极材料,通过“Z型”叠片方式组装成容量达30000 F、内阻值小于0.5 mΩ的混合型超级电容器。考察了不同导电剂添加量、不同正负电极平衡比、单体高低温与安全性能测试情况。结果表明,导电剂含量为8%（质量分数）、正负电极质量比为2.23～2.82时,混合型超级电容器具有30000 F以上的容量和稳定的循环寿命,同时单体内阻能够恒定在0.5 mΩ以下。此外,该混合型超级电容器具有良好的高低温与安全性能,是一种具有广阔应用前景的储能器件。     

锂离子电池补锂技术

锂离子电池在化成过程中,负极SEI膜的形成会消耗大量活性锂,特别是在添加部分高容量硅基负极材料的情况下,导致电池首周库仑效率和电池容量低.补充活性锂是解决这一问题的有效手段,目前已报道的补充活性锂的途径很多,主要是负极补锂和正极极补锂两大类.负极补锂包括金属锂物理混合锂化,如在负极中添加金属锂粉或在极片表面辊压金属锂箔;化学锂化,使用丁基锂等锂化剂对负极进行化学预嵌锂;自放电锂化,负极与金属锂在电解液中接触完成自放电锂化;电化学预锂化,在电池中引入金属锂作为第三极,负极与金属锂第三极组成对电极充放电完成预锂化.正极补锂是向锂离子电池的正极中添加具有高不可逆容量的含锂化合物,根据化合物的种类不同,可以分为以Li2O、Li2O2、Li2S为代表的二元含锂化合物,以Li6CoO4、Li5FeO4为代表的三元含锂化合物和以Li2DHBN、Li2C2O4为代表的有机含锂化合物.补锂技术的应用不仅提高了锂离子电池的容量,还可以提升含硅负极电池的循环寿命.本文总结了补锂技术的发展状况和本课题组在补锂技术方面的一些工作,并展望了补锂技术在锂离子电池中的应用前景.     

高温下Ti掺杂对Li4SiO4吸收CO2性能的影响

采用固相合成法和溶胶凝胶法分别制备了可直接在高温下吸收CO2的硅酸锂(Li4SiO4),并进行了Ti的掺杂改性.采用X射线衍射仪、比表面积测定仪和热重分析仪对Li4SiO4进行了表征及CO2吸收性能的测试,并在固定床台架上进行了CO2循环吸收/解吸的试验研究.结果表明:溶胶凝胶法制备的纯Li4SiO4更有利于在高温下对CO2的吸收;CO2的分压对高温下Li4SiO4吸收CO2有很大影响,分压越大,吸收的CO2量越大;当TiO2的掺杂比例x=0.02时,改性的Li4SiO4对CO2的最大吸收量可达31.59%;经过20次循环后,固溶体Li4Si0.98Ti0.02 O4对CO2的吸收量仅下降了20%,从第4次循环后此样品基本达到完全再生,说明其具有较大的CO2吸收量和优良的再生性能.     

Recent research progress of Li4Ti5O12 as anode materials for lithium-ion batteries

锂离子电池凭借诸多优势广泛应用于便携式电子产品（3C）领域,在电动汽车及可穿戴设备方面具有巨大应用前景,是未来最具潜力的储能电池之一。作为一种锂离子电池负极材料,尖晶石型Li₄Ti₅O₁₂相比石墨负极具有较高嵌锂电位,且"零应变材料"的特性决定Li₄Ti₅O₁₂材料具有较好的循环稳定性及热稳定性,从而备受关注。本文简要介绍了钛酸锂（Li₄Ti₅O₁₂）的结构和性能,详细阐明了Li₄Ti₅O₁₂的嵌锂机制、制备及改性方法,总结了相应制备及改性方法对Li₄Ti₅O₁₂材料的充放电特性、循环性能等电化学性能的影响,针对Li₄Ti₅O₁₂的胀气产生原因、机制和胀气解决方法进行简单阐述,并对纯电动乘用车的应用前景提出了几点建议。     

Rb掺杂Li4Ti5O12作为锂离子电池负极材料的合成及电化学性能

合成了不同Rb掺杂量的钛酸锂（Li_4-xRb_xTi₅O₁₂; x = 0.010, 0.015, 0.020）作为锂离子电池的负极材料。测试结果显示,Rb离子掺杂有效增强了钛酸锂的电子电导率。相同的测试条件下,相比于未掺杂样品和高Rb含量掺杂样品（x = 0.015, 0.020）,适量的Rb掺杂钛酸锂（Li_3.99Rb_0.01Ti₅O₁₂; x = 0.010）表现出最优的电化学性能。Li_3.99Rb_0.01Ti₅O₁₂材料表现出161.2 mA∙h/g的初始容量,且在1 C下经过1000次循环后容量保持率可达90.9%。此外,全电池Li_3.99Rb_0.01Ti₅O₁₂ // LiFePO₄在0.5 C条件下首次放电容量为144 mA∙h/g,经过150次循环后,容量保持率为78.8%。     

ZnO包覆锂电池阴极材料LiMn2O4性能研究

文中研究通过溶剂凝胶法合成锂电池阴极材料锰酸锂(Li Mn2O4),并使用Zn O对其表面进行包覆改性。通过X射线衍射(XRD),扫描电镜(SEM),充放电循环测试等手段对得到的产品进行物理化学性能测试。研究结果表明,改性后的材料的循环性能较改性前相比有较大的提高,这主要是由于表明包覆物质减少了活性材料与电解液的接触面积,抑制了锰离子的溶剂,在充放电过程中稳定了Li Mn2O4结构。     

The cycle life investigation for spinel LiNi0.5Mn1.5O4 full cells

分别以石墨和钛酸锂为负极活性物质,制备了尖晶石镍锰酸锂的32131型圆柱锂离子电池.石墨负极电池和钛酸锂负极电池容量分别为7.5 A·h和5.5 A·h,质量能量密度分别达到152 W·h/kg和81 W·h/kg.常温充放电循环测试结果表明,石墨和钛酸锂两种负极体系电池循环寿命将分别达到400次和1000次,这种循环寿命的差别主要体现在负极上,即正极材料中溶解的Mn在石墨负极表面沉积并持续催化SEI膜生成,减少了电池中可使用的活性Li⁺,进而导致电池寿命快速衰减;相比而言,钛酸锂负极表面不存在明显SEI,同时正极过量设计电池也使得钛酸锂体系电池的镍锰酸锂与电解液间的界面副反应低于石墨体系的负极过量设计电池.     

有机溶剂浸泡法回收再利用锂离子电池钛酸锂负极材料

利用有机溶剂法回收了废旧锂离子电池中的钛酸锂负极材料,并对回收的钛酸锂材料的结构、形貌和电化学性能进行了测试。XRD结果表明,材料除炭后添加适量锂源进一步合成得到的产物具有尖晶石结构,且不含其他的杂质。SEM图像显示,其颗粒分布均匀、无团聚现象。EIS结果表明,最终回收的钛酸锂电极材料比未添加锂源进行煅烧处理的材料具有较小的电荷转移阻抗和较高的锂离子扩散系数。在0.1 C倍率下,经过100次循环后其容量保持率为92.4%,具有优异的循环稳定性和可逆性,可以实现循环利用。     

Preparation of a new Ti catalyst for improved performance of NaAlH4

Three effective Ti catalysts for NaAlH₄ were made by stoichiometrically reacting TiCl₃ with LiAlH₄ in tetrahydrofuran (THF), NaAlH₄ in THF, and LiAlH₄ in diethyl ether (Et₂O). The solid products produced after drying were named ex situ catalysts and designated respectively as Ti(Li)T, Ti(Na)T and Ti(Li)E. NaAlH₄ was dry doped with 2 mol% of these ex situ catalysts, and for comparison, NaAlH₄ was conventionally wet doped with 2 mol% TiCl₃ in THF that made in situ catalyst (designated as TiCl₃). All four doped samples were dry ball milled, and hydrogenation and dehydrogenation studies were carried out over five cycles. Temperature programmed desorption, constant temperature desorption, and constant temperature cycling curves showed that the effectiveness of these catalysts decreased as Ti(Li)T > Ti(Na)T > TiCl₃ > Ti(Li)E. Ti(Li)T ex situ catalyst, being the best Ti catalyst, markedly decreased the dehydrogenation temperature, improved both the hydrogenation and dehydrogenation kinetics with sustained rates over cycling, and exhibited the least loss of hydrogen storage capacity over cycling. Ti(Li)T ex situ catalyst exhibited properties commensurate with some of the best NaAlH₄ catalysts to date, such as CeCl₃, ScCl₃ and Ti nanocluster. It is easy to make, readily available and relatively inexpensive.     

C2H2M (M = Ti,Li) complex: A possible hydrogen storage material

The hydrogen storage capacity of Ti-acetylene (C₂H₂Ti) and Li-acetylene (C₂H₂Li) complex has been tested using second order Møller Plesset method with different basis sets. Single Ti(Li) decorated acetylene complex can adsorb maximum of five(four) hydrogen molecules, which corresponds to the gravimetric hydrogen storage capacity of 12(19.65) wt % and it meets the target of 9 wt % by 2015 specified by US Department of Energy. The hydrogen adsorption energies with zero point energy and Gibbs free energy correction show that hydrogen adsorption on C₂H₂Ti is energetically favourable for a wide range of temperature and that is unfavourable on C₂H₂Li complex even at a very low temperature. Atom centered density matrix propagation molecular dynamics simulations reveal that four H₂ molecules remain adsorbed on C₂H₂Ti complex at 300 K. Though H₂ uptake capacity of C₂H₂Li complex is higher than that of C₂H₂Ti complex, the thermochemistry results favour to C₂H₂Ti complex over C₂H₂Li complex as a possible hydrogen storage media.     

Density functional theory study on hydrogen storage capacity of metal-embedded penta-octa-graphene

H₂ storage capabilities of penta-octa-graphene (POG) adorned by lightweight alkali metals (Li, Na, K), alkali earth metals (Be, Mg, Ca) and transition metals (Sc, Ti, V, Cr, Mn) are studied by density functional theory. Metals considered, with the exception of Be and Mg, can be stably adsorbed to POG, effectively avoiding metal clustering. The average H₂ adsorption energies are calculated in a range from 0.14 to 0.95 eV for Li (Na, K, Ca, Sc, Ti, V, Cr, Mn) decorated POG. Because the H₂ adsorption energies for reversible physical adsorption lie in the range of 0.15–0.60 eV and the desorption temperatures fall in the range of 233–333 K under the delivery pressure, 4Li@POG and 2Ti@POG are found to be the most suitable for H₂ storage at ambient temperature. By polarization and hybridization mechanisms, up to 3 and 5 hydrogen molecules are stably adsorbed around each Li and Ti, respectively. The H₂ gravimetric densities can reach up to 9.9 wt% and 6.5 wt% for Li and Ti decorated POG, respectively. Our findings suggest that, with metal decoration, such a novel two-dimensional carbon-based structure could be a promising medium for H₂ storage.     

Multiple Ti and Li doped carbon nanoring for hydrogen storage

Multiple Ti and Li atom doped carbon nanorings are considered for hydrogen storage using density functional theory for the first time. There are five six membered carbon rings bonded through C–C bond in a carbon nanoring. Formation energy values show that both, Li as well as Ti atom doped carbon nanoring, are thermodynamically stable structures. Cohesive energy values indicate that Li and Ti atom doped carbon nanoring structures are more stable than undoped carbon nanoring. No clustering of metal atoms occurs in metal doped carbon nanorings which usually reduces the hydrogen storage capacity of a material. Li atom doped carbon nanoring is not suitable for hydrogen storage even at very low temperature at 1 atm pressure as well as at high pressure at room temperature. Ti atom doped carbon nanoring is suitable for hydrogen storage below 225 K and 1 atm pressure as well as at high pressure at room temperature. H₂ desorption temperature is found to be 113 and 450 K for Li and Ti atom doped carbon nanoring respectively. H₂ molecules interact strongly with Ti atom doped carbon nanoring than Li atom doped carbon nanoring that results in higher H₂ desorption temperature for the former than the latter.     

Favorable combination of positive and negative electrode materials with glyme-Li salt complex electrolytes in lithium ion batteries

Tetraglyme (G4)-lithium bis(trifluoromethanesulfonyl)amide (TFSA) complexes with different G4 ratio were investigated. An increase in the amount of G4 led to the decrease in the viscosity, and increase in the ionic conductivity of the complex, and G4-LiTFSA showed higher thermal stabilities than the conventional organic electrolyte, when the molar ratio of G4 was more than 40 mol%. The increase in the G4 amount improved the rate capabilities of Li/LiCoO₂ cells in the range where the molar ratio of G4 was between 40 mol% and 60 mol%. The stable Li ion intercalation-deintercalation was not observed in the Li/graphite cell of [Li(G4)][TFSA] (G4: 50 mol%) without additives. However, the additives for forming solid electrolyte interface (SEI) film, such as vinylene carbonate, vinylethylene carbonate, and 1,3-propane sultone, led to the charge-discharge performance comparable to that of the conventional organic electrolyte. The adoption of Li₄Ti₅O₁₂ and LiFePO₄ led to excellent reversibilities of the Li half cells using [Li(G4)][TFSA], probably because of the favorable operation voltage. In the case of the LiFePO₄/Li₄Ti₅O₁₂ cell, the cell with [Li(G4)][TFSA] showed the better rate capability than that with the conventional organic electrolyte, when the rate was less than 1 CmA, and it is concluded that [Li(G4)][TFSA] can be the candidate as the alternative of organic electrolytes when the most appropriate electrode-active materials are used.     

Confinement effects on structural,electronic properties and dehydrogenation thermodynamics of LiBH4

Confinement effect on the structural, electronic and thermodynamic properties of LiBH₄ is investigated by density functional theory. The thermodynamically and dynamically stable confinement structure is testified to be γ-LiBH₄@C₃₁Ti according to the adsorption energy and vibrational frequency calculations. The tridentate structure formed by [BH₄]⁻ and Li⁺ in the unconfined LiBH₄ changes into bidentate structure in γ-LiBH₄@C₃₁Ti. We observe that both the occupied and unoccupied states of H 1s, B 2s, B 2p, Li 2s, and Li 2p orbitals in the partial DOSs of γ-LiBH₄@C₃₁Ti shift to high energy level and the splits of DOS peaks occur at the states of H 1s, B 2p, and Li 2p orbitals. Different from the first-step decomposition reaction of LiBH₄, the one for γ-LiBH₄@C₃₁Ti changes into 2LiBH₄@C₃₁Ti → 2LiH + 2B@C₃₁Ti + 3H₂. Moreover, the reaction enthalpy for the first-step decomposition reaction of γ-LiBH₄@C₃₁Ti decreases to 5.864 eV, which is smaller than that (17.204 eV) of LiBH₄. According to the hydrogen removal energy calculations, we observe that the confinement effects make the removal of the first and second hydrogen atoms in γ-LiBH₄@C₃₁Ti easy.     

Effects of TiO2 coating on high-temperature cycle performance of LiFePO4-based lithium-ion batteries

LiFePO₄ particles were coated with TiO₂ (molar ratio = 3%) via a sol–gel process, and the effects of the coating on cycle performance of LiFePO₄ cathode at 55 °C against either a Li or a C (mesocarbon microbead) anode were investigated. It was found that, while the coating reduces capacity fading of the LiFePO₄/Li cell, it imposes a deteriorating effect on the LiFePO₄/C cell. Analyses on cell impedance and electrode surface morphology and composition showed that the oxide coating reduced Fe dissolution from the LiFePO₄ cathode and hence alleviated the impedance increase associated with the erosion process. This leads to reduced capacity fading as observed for the LiFePO₄/Li cell. However, the oxide coating itself was eroded upon cycling, and the dissolved Ti ions were subsequently reduced at the anode surface. Ti deposit on the C anode was found to be more active than Fe in catalyzing the formation of the solid-electrolyte interphase (SEI) layer, causing accelerated capacity decay for the LiFePO₄/C cell. The results point out the importance of evaluating the effect of cathode coating material on the anode side, which has generally been overlooked in the past studies.     

Preparation and rate capability of Li4Ti5O12 hollow-sphere anode material

Spinel lithium titanate, Li₄Ti₅O₁₂, with novel hollow-sphere structure was fabricated by a sol–gel process using carbon sphere as template. The effect of the hollow-sphere structure as well as the wall thickness on the Li storage capability and high rate performance was electrochemically evaluated. High specific capacity, especially better high rate performance was achieved with this Li₄Ti₅O₁₂ hollow-sphere electrode material with thin wall thickness. It is believed that this macroporous hollow-sphere structure has shortened the Li diffusion distance, increased the contact area between Li₄Ti₅O₁₂ and electrolyte, and also led to better mixing of the active material with AB. All these factors have resulted in the good rate capability of the hollow-sphere structured Li₄Ti₅O₁₂ electrode material.     

The reversible hydrogen storage abilities of metal Na (Li,K, Ca,Mg, Sc,Ti, Y) decorated all-boron cage B28

The density functional theory is used to study the hydrogen storage abilities of alkali metal Li (Na, K), alkaline-earth metal Mg (Ca), and transition metal Ti (Ti, Sc, Y) decorated B₂₈, which is the possible smallest all-boron cage and contains one hexagonal hole and two octagonal holes. The most stable structure of B₂₈ explored by the calypso search is as same as that explored by Zhao et al. [Nanoscale 7(2015)15086]. It is calculated that the hollow sites outside of the cavities should be the most stable for all metals except for Ti. The average adsorption energy of H₂ molecules (E_ad) adsorbed by each Na (Ca, K, Mg, Sc, Y and Li) atom outside of the B₂₈ cage are in the range from 0.2 to 0.6 eV, which is suitable for hydrogen storage under near-ambient conditions. However, the largest hydrogen gravimetric density (HGD) for the B₂₈Sc₃-12H₂ structure is smaller than the target of 5.5 wt% by the year 2017 specified by the US Department of Energy (DOE). Therefore, the metal Ti (Sc) decorated all-boron cage B₂₈ should not be good candidates for hydrogen storage. The calculated desorption temperature and the molecular dynamic simulation indicate that the B₂₈M₃-nH₂ (M = Na, Li, Ca, K, Mg, Y) structures are easy to desorb the H₂ molecules at the room temperature (T = 300 k). Furthermore, the B₂₈ cages bridged by the sp²-terminated B₅ chain can hold Na (Li, Ca, K, Mg, Y) atoms to capture hydrogen molecules with moderate E_ad and HGD. These findings suggest a new route to design hydrogen storage materials under the near-ambient conditions.