Structure Sensitivity in the Decomposition of Ethylene Carbonate on Si Anodes

The interaction of ethylene carbonate (EC) with Si surfaces is studied by density functional theory. The results show a strong structure sensitivity in the adsorption of EC on Si surfaces. While the adsorbed EC molecule readily decomposes on the Li/Si(111) surface, it does not dissociate on the Li/Si(100) and Li/Si(110) surfaces. On Si(111), the O atom at the top of EC is detached from the EC molecule and binds to the Li adatom, forming Li?O molecules. The mechanism of EC decomposition is the transfer of 2.4 electrons from the surface to the EC molecule, as well as the formation of a covalent bond between the Li adatom and the EC molecule. This result shows that in lithium‐ion batteries with Si anodes, dissociation of the solvent and formation of a solid electrolyte interphase layer start as soon as the Li atoms cover the anode surface.     

Conformal Surface Coatings to Enable High Volume Expansion Li‐Ion Anode Materials

An alumina surface coating is demonstrated to improve electrochemical performance of MoO₃ nanoparticles as high capacity/high‐volume expansion anodes for Li‐ion batteries. Thin, conformal surface coatings were grown using atomic layer deposition (ALD) that relies on self‐limiting surface reactions. ALD coatings were tested on both individual nanoparticles and prefabricated electrodes containing conductive additive and binder. The coated and non‐coated materials were characterized using transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, electrochemical impedance spectroscopy, and galvanostatic charge/discharge cycling. Importantly, increased stability and capacity retention was only observed when the fully fabricated electrode was coated. The alumina layer both improves the adhesion of the entire electrode, during volume expansion/contraction and protects the nanoparticle surfaces. Coating the entire electrode also allows for an important carbothermal reduction process that occurs during electrode pre‐heat treatment. ALD is thus demonstrated as a novel and necessary method that may be employed to coat the tortuous network of a battery electrode.     

Towards understanding the effects of carbon and nitrogen-doped carbon coating on the electrochemical performance of Li4Ti5O12 in lithium ion batteries: a combined experimental and theoretical study

We investigate the effects of carbon coating, with and without nitrogen-dopants, on the electrochemical performance of a promising anode material Li(4)Ti(5)O(12) (LTO) in lithium ion battery applications. The comparative experimental results show that LTO samples coated with nitrogen-doped carbon derived from pyridine and an ionic liquid exhibit significant improvements in rate capability and cycling performance compared with a LTO sample coated by carbon derived from toluene and the pristine LTO sample. For the first time, we construct an atomistic model for the interface between the lithium transition metal oxide and carbon coating layers. Our first-principles calculations based on density functional theory reveal that at this interface there is strong binding between the graphene coating layer and the Ti-terminated LTO surface, which significantly reduces the chemical activity of LTO surfaces and stabilizes the electrode/electrolyte interface, providing a clue to solve the swelling problem for LTO-based batteries. More importantly, electron transfer from the LTO surface to graphene greatly improves the electric conductivity of the interface. Nitrogen-dopants in graphene coatings further increase the interfacial stability and electric conductivity, which is beneficial to the electrochemical performance in energy storage applications.     

添加剂氟代碳酸乙烯酯对锂离子电池性能的影响

在1 mol·L-1 LiPF6/碳酸乙烯酯(EC)+碳酸二甲酯(DMC)+碳酸甲乙酯(EMC)(EC、DMC、EMC体积比为1:1:1)电解液中加入体积比为2%的添加剂氟代碳酸乙烯酯(FEC), 用循环伏安法(CV)、扫描电镜(SEM)、能量散射光谱(EDS)、电化学阻抗谱(EIS)等方法, 研究了FEC 对锂离子电池性能及石墨化中间相碳微球(MCMB)电极/电解液界面性质的影响. 结果表明, 体积比2%FEC的添加可以抑制部分电解液溶剂的分解, 在MCMB电极表面形成一层性能优良的固体电解液相界面(SEI)膜, 降低了电池的阻抗, 明显提高了电池的比容量和循环稳定性.     

Li-O2 battery with a dimethylformamide electrolyte

Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li-O(2) battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O(2) cathode on the first discharge-charge cycle are dominated by reversible Li(2)O(2) formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the cathode on discharge are Li(2)O(2), Li(2)CO(3), HCO(2)Li, CH(3)CO(2)Li, NO, H(2)O, and CO(2). Li(2)CO(3) accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li-O(2) battery.     

影响电池性能的因素：金属离子溶剂化结构衍生的界面行为还是固体电解质界面膜?

通过电解液分解在电极上形成的固体电解质界面（SEI）层被认为是影响电池性能的最重要因素。 然而，我们发现金属离子溶剂化结构也会影响其电极性能，尤其可以阐明许多SEI无法解释的实验现象。基于该综述，本文总结了金属离子溶剂化结构和衍生的金属离子去溶剂化行为的重要性，并建立了相应的界面模型以展示界面行为和电极性能之间的关系，并将其应用于不同的电极和电池体系。我们强调了电极界面离子/分子相互作用对电极性能的影响，该解释与以往基于SEI的解释不同。该综述为理解电池性能和指导电解液设计提供了一个新的视角。     

The understanding of solid electrolyte interface (SEI) formation and mechanism as the effect of flouro-o-phenylenedimaleimaide (F-MI) additive on lithium-ion battery

Solid electrolyte interface (SEI) is a critical factor that influences battery performance. SEI layer is formed by the decomposition of organic and inorganic compounds after the first cycle. This study investigates SEI formation as a product of electrolyte decomposition by the presence of flouro-o-phenylenedimaleimaide (F-MI) additive. The presence of fluorine on the maleimide-based additive can increase storage capacity and reversible discharge capacity due to high electronegativity and high electron-withdrawing group. The electrolyte containing 0.1 wt% of F-MI-based additive can trigger the formation of SEI, which could suppress the decomposition of remaining electrolyte. The reduction potential was 2.35 to 2.21 V vs Li/Li⁺ as examined by cyclic voltammetry (CV). The mesocarbon microbeads (MCMB) cell with F-MI additive showed the lowest SEI resistance (Rsei) at 5898 Ω as evaluated by the electrochemical impedance spectroscopy (EIS). The morphology and element analysis on the negative electrode after the first charge-discharge cycle were examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). XPS result showed that MCMB cell with F-MI additive provides a higher intensity of organic compounds (RCH₂OCO₂Li) and thinner SEI than MCMB cell without an additive that provides a higher intensity of inorganic compound (Li₂CO₃ and Li₂O), which leads to the performance decay. It is concluded that attaching the fluorine functional group on the maleimide-based additive forms the ideal SEI formation for lithium-ion battery.     

Solvent decompositions and physical properties of decomposition compounds in Li-ion battery electrolytes studied by DFT calculations and molecular dynamics simulations

The density functional theory (DFT) calculations have been performed for the reduction decompositions of solvents widely used in Li-ion secondary battery electrolytes, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonates (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), including a typical electrolyte additive, vinylene carbonate (VC), at the level of B3LYP/6-311+G(2d,p), both in the gas phase and solution using the polarizable conductor calculation model. In the gas phase, the first electron reduction for the cyclic carbonates and for the linear carbonates is found to be exothermic and endothermic, respectively, while the second electron reduction is endothermic for all the compounds examined. On the contrary, in solution both first and second electron reductions are exothermic for all the compounds. Among the solvents and the additive examined, the likelihood of undergoing the first electron reduction in solution was found in the order of EC > PC > VC > DMC > EMC > DEC with EC being the most likely reduced. VC, on the other hand, is most likely to undergo the second electron reduction among the compounds, in the order of VC > EC > PC. Based on the results, the experimentally demonstrated effectiveness of VC as an excellent electrolyte additive was discussed. The bulk thermodynamic properties of two dilithium alkylene glycol dicarbonates, dilithium ethylene glycol dicarbonate (Li-EDC) and dilithium 1,2-propylene glycol dicarbonate (Li-PDC), as the major component of solid-electrolyte interface (SEI) films were also examined through molecular dynamics (MD) simulations in order to understand the stability of the SEI film. It was found that film produced from a decomposition of EC, modeled by Li-EDC, has a higher density, more cohesive energy, and less solubility to the solvent than the film produced from decomposition of PC, Li-PDC. Further, MD simulations of the interface between the decomposition compound and graphite suggested that Li-EDC has more favorable interactions with the graphite surface than Li-PDC. The difference in the SEI film stability and the behavior of Li-ion battery cycling among the solvents were discussed in terms of the molecular structures.     

Investigation of Ig.G adsorption and the effect on electrochemical responses at titanium dioxide electrode

The adsorption of Immunoglobulin G on a titanium dioxide (TiO(2)) electrode surface was investigated using (125)I radiolabeling and electrochemical impedance spectroscopy (EIS). (125)I radiolabeling was used to determine the extent of protein adsorption, while EIS was used to ascertain the effect of the adsorbed protein layer on the electrode double layer capacitance and electron transfer between the TiO(2) electrode and the electrolyte. The adsorbed amounts of Ig.G agreed well with previous results and showed approximately monolayer coverage. The amount of adsorbed protein increased when a positive potential was applied to the electrode, while the application of a negative potential resulted in a decrease. Exposure to solutions of Ig.G resulted in a decrease of the double layer capacitance (C) and an increase in the charge-transfer resistance (R(2)) at the electrode solution interface. As more Ig.G adsorbed onto the electrode surface, the extent of C and R(2) variation increased. These capacitance and charge-transfer resistance variations were attributed to the formation of a proteinaceous layer on the electrode surface during exposure.     

A Long‐Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.     

A Long-Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.     

A Designed Durable Electrolyte for High-Voltage Lithium-Ion Batteries and Mechanism Analysis

Rechargeable lithium-ion batteries (LIBs) dominate the energy market, from electronic devices to electric vehicles, but pursuing greater energy density remains challenging owing to the limited electrode capacity. Although increasing the cut-off voltage of LIBs (>4.4 V vs. Li/Li⁺) can enhance the energy density, the aggravated electrolyte decomposition always leads to a severe capacity fading and/or expiry of the battery. Herein, a new durable electrolyte is reported for high-voltage LIBs. The designed electrolyte is composed of mixed linear alkyl carbonate solvent with certain cyclic carbonate additives, in which use of the ethylene carbonate (EC) co-solvent was successfully avoided to suppress the electrolyte decomposition. As a result, an extremely high cycling stability, rate capability, and high-temperature storage performance were demonstrated in the case of a graphite|LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) battery at 4.45 V when this electrolyte was used. The good compatibility of the electrolyte with the graphite anode and the mitigated structural degradation of the NCM622 cathode are responsible for the high performance at high potentials above 4.4 V. This work presents a promising application of high-voltage electrolytes for pursuing high energy LIBs and provides a straightforward guide to study the electrodes/electrolyte interface for higher stability.     

Solvent Molecule Cooperation Enhancing Lithium Metal Battery Performance at Both Electrodes

Developing electrolytes compatible with efficient and reversible cycling of electrodes is critical to the success of rechargeable Li metal batteries (LMBs). The Coulombic efficiencies and cycle lives of LMBs with ethylene carbonate (EC), dimethyl carbonate, ethylene sulfite (ES), and their combinations as electrolyte solvents show that in a binary‐solvent electrolyte the extent of electrolyte decomposition on the electrode surface is dependent on the solvent component that dominates the solvation sheath of Li⁺. This knowledge led to the development of an EC‐ES electrolyte exhibiting high performance for Li||LiFePO₄ batteries. Carbonate molecules occupy the solvation sheath and improve the Coulombic efficiencies of both the anode and cathode. Sulfite molecules lead to desirable morphology and composition of the solid electrolyte interphase and extend the cycle life of the Li metal anode. The cooperation between these components provides a new example of electrolyte optimization for improved LMBs.     

电解液添加剂硫酸亚乙酯对锂离子电池性能的影响

在1 mol/L LiPF₆/碳酸乙烯酯+碳酸二甲酯+碳酸甲乙酯（体积比1∶1∶1）电解液中,采用恒流充放电测试、循环伏安法（CV）、扫描电子显微镜（SEM）、能量散射光谱（EDS）、电化学阻抗谱（EIS）等测试技术,研究了添加剂硫酸亚乙酯（DTD）对锂离子电池性能及石墨化中间相碳微球（MCMB）电极/电解液界面性质的影响。 结果表明,在电解液中引入体积分数0.01%DTD后,MCMB/Li电池可逆放电容量从300 mA·h/g提高至350 mA·h/g,电池总阻抗降低,循环稳定性提高。CV测试发现,在首次还原过程中,DTD在电极电位1.4 V左右（vs Li/Li⁺）发生电化学还原,参与了MCMB电极表面固体电解质相界面膜（SEI膜）的形成过程。 同时,DTD对LiMn₂O₄电极性能无不良影响。     

Li_2CO_3添加剂对石墨电极性能的影响

运用电化学阻抗谱(EIS)和循环伏安法(CV)研究了在1mol/LLiPF6-EC(碳酸乙烯酯):DMC(碳酸二甲酯)电解液中添加Li2CO3对石墨电极性能的影响及机制.CV研究结果表明,在1mol/LLiPF6-EC:DMC电解液中添加Li2CO3能够有效抑制石墨电极首次充放电过程中碳酸乙烯酯(EC)的单电子还原过程,即还原分解产生乙烯和碳酸锂的过程,进而改善石墨电极的电化学循环性能.EIS研究结果表明,在添加Li2CO3的1mol/LLiPF6-EC:DMC电解液中,石墨电极表面的固体电解质相界面膜(SEI膜)具有较强的黏弹性,可以更好地适应锂离子嵌入过程中石墨颗粒体积的微小变化,从而使锂离子的嵌入过程更容易进行.     

Thermal Behavior Investigation of LiNi1/3Co1/3Mn1/3O2-Based Li-ion Battery under Overcharged Test

Thermal behavior of its components such as separator, electrolyte, cathode, anode, and each binder were investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG) to explain thermal runaway mechanism of Li‐ion battery under overcharged test. DSC results indicated the decomposition reaction temperature of SEI (solid electrolyte interface) layer in anode was at about 126°C. It was found that heat generation in anode under normal charged state increased obviously with the increasing of charged voltage. When the battery was overcharged to 4.6 V or 5.0 V, the onset temperature and heat generation of thermal reaction in anode changed a little, while those in cathode had large increase. It was proposed that thermal behavior in cathode mainly caused by the reaction of electrolyte with evolutional oxygen played a key role to thermal runaway for the studied Li‐ion battery under overcharged test.     

电极界面浓差极化对锂金属沉积的影响

锂金属作为下一代高能量密度电池的理想负极材料受到研究人员广泛关注。然而,锂枝晶生长引起的安全隐患和循环寿命短等问题严重影响了锂金属电池的实用化进程。本文以电化学现象和理论为依据,从浓差极化角度详细分析锂金属电沉积过程中枝晶生长、死锂形成和全电池失效机制,并对目前研究较多的多孔宿主电极中的浓差极化及枝晶抑制进行分析,提出锂金属界面浓差电池现象。本文得到的结论为研究人员更深入地探究锂金属保护策略提供了理论依据。     

A new type rechargeable lithium battery based on a Cu-cathode

In present work, we report a new type rechargeable lithium battery, in which a Cu-cathode in aqueous electrolyte and a Li-anode in non-aqueous electrolyte are united together by a lithium super-ionic conductor glass film (LISICON) through which only lithium-ions can pass. During the charge–discharge process, combining with the dissolution–deposition of metallic Cu (or Li) electrode, lithium ions transfer between aqueous electrolyte solution and non-aqueous electrolyte solution. In Li–Cu system, for the first time, the dissolution/deposition process of metallic Cu was used as cathode reaction to replace the Li-insertion/extraction reaction within conventional lithium-ion battery. The Cu-cathode is renewable, and displays a high capacity. The concept of Li–Cu system may provide a new direction for future lithium batteries study.     

Electrochemistry of Hydroquinone Derivatives at Metal and Iodine-modified Metal Electrodes

IntroductionPlatinumand gold surfaces can adsorb a wide vari-ety of ions, atoms and molecular functional groups,which is often accompanied by oxidation-reduction ordissociation of them. Numerous previous works havemade great progress in studying the surfa…     

Li_4Ti_5O_(12)纳米片的合成及储锂性能研究

以无定形的水合二氧化钛为前驱物,水热法合成了200～400nm大小的Li4Ti5O12纳米片作为锂离子电池负极材料.XRD(X射线衍射)、SEM(扫描电子显微镜)和TEM(透射电镜)分析表征样品的物相结构、表观形貌;循环伏安、充放电循环和电化学交流阻抗技术分别测定该纳米Li4Ti5O12在有机电解液和室温离子液体S114TFSI电解液中的电化学性能.结果表明,该材料具有较高的放电容量和良好的循环性能,有望成为锂二次电池新型负极材料.