固态锂电池中正极/电解质界面的密度泛函计算研究

锂离子电池的广泛应用对储能器件的能量密度、安全性和充放电速度提出了新的要求. 全固态锂电池与传统锂离子电池相比具有更少的副反应和更高的安全性,已成为下一代储能器件的首选. 构建匹配的电极/电解质界面是在全固态锂电池中获得优异综合性能的关键. 本文采用第一性原理计算研究了固态电池中电解质表面及正极/电解质界面的局域结构和锂离子输运性质. 选取β-Li₃PS₄ (010)/LiCoO₂ (104)和 Li₄GeS₄ (010)/LiCoO₂ (104)体系计算了界面处的成键情况及锂离子的迁移势垒. 部分脱锂态的正极/电解质界面上由于Co-S成键的加强削弱了P/Ge-S键的强度,降低了对Li⁺的束缚,从而导致了更低的锂离子迁移势垒. 理解界面局域结构及其对Li+输运性质的影响将有助于我们在固态电池中构建性能优异的电极/电解质界面.     

Li2S-P2S5体系电解质及其在全固态锂离子电池中的应用研究进展

全固态锂离子电池具有安全性能好、能量密度高、工作温区广等优点,被广泛应用于便携式电子设备。固态电解质是全固态锂离子电池的关键材料之一,其中的硫化物电解质具有离子电导率高、电化学窗口宽、晶界电阻低和易成膜等特点,被认为最有希望应用于全固态锂离子电池。本文综述了Li_2S-P_2S_5体系电解质的发展状况,包括固态电解质的制备、改性、表征以及电极/固态电解质之间的固-固界面的稳定兼容问题。本文还涉及了以Li_2S-P_2S_5为电解质的全固态锂离子电池性能的研究进展。     

A review on electrode and electrolyte for lithium ion batteries under low temperature

Under low temperature (LT) conditions (−80 °C∼0 °C), lithium-ion batteries (LIBs) may experience the formation of an extensive solid electrolyte interface (SEI), which can cause a series of detrimental effects such as Li⁺ deposition and irregular dendritic filament growth on the electrolyte surface. These issues ultimately lead to the degradation of the LT performance of LIBs. As a result, new electrode/electrolyte materials are necessary to address these challenges and enable the proper functioning of LIBs at LT. Given that most electrochemical reactions in lithium-ion batteries occur at the electrode/electrolyte interface, finding solutions to mitigate the negative impact caused by SEI is crucial to improve the LT performance of LIBs. In this article, we analyze and summarize the recent studies on electrode and electrolyte materials for low temperature lithium-ion batteries (LIBs). These materials include both metallic materials like tin, manganese, and cobalt, as well as non-metallic materials such as graphite and graphene. Modified materials, such as those with nano or alloying characteristics, generally exhibit better properties than raw materials. For instance, Sn nanowire-Si nanoparticles (SiNPs−In-SnNWs) and tin dioxide carbon nanotubes (SnO₂@CNT) have faster Li⁺ transport rates and higher reversible capacity at LT. However, it′s important to note that when operating under LT, the electrolyte may solidify, leading to difficulty in Li⁺ transmission. The compatibility between the electrolyte and electrode can affect the formation of the solid electrolyte interphase (SEI) and the stability of the electrode/electrolyte system. Therefore, a good electrode/electrolyte system is crucial for successful operation of LIBs at LT.     

Critical challenges and progress of solid garnet electrolytes for all-solid-state batteries

Significant safety problems and poor cyclic stability of conventional lithium-ion batteries, which based on organic liquid electrolytes, hinder their practical application, while all-solid-state batteries (ASSBs) are considered the most promising candidates to replace traditional lithium-ion batteries. As a critical component of ASSBs, solid-state electrolytes play an essential role in ion transport properties and stability. At present, the solid garnet electrolyte is considered as one of the most promising electrolytes because of its excellent performance. However, it still faces many challenges in ionic conductivity, air stability, electrode/electrolyte interface, and lithium dendrites. Therefore, this review is concerned about the up-to-date progress and challenges which will greatly influence the large-scale application of solid garnet electrolytes. Firstly, various ways to improve the ionic conductivity of solid garnet electrolytes are comprehensively summarized. Then, the stability of solid garnet electrolytes in the air is carefully discussed. Secondly, the latest progress in interface engineering between anode/cathode and solid garnet electrolytes treated by different methods is reported. The formation mechanism and influencing factors of lithium dendrites in the solid garnet electrolyte are systematically focused on. Finally, the development and innovation of composite solid garnet electrolytes and 3D garnet electrolytes are summarized in detail. Some important characterization techniques for studying the aforementioned problems are also summarized. Based on the current development of solid garnet electrolytes and solid-state batteries, further challenges and perspectives are presented.     

Review on multi-scale models of solid-electrolyte interphase formation

Electrolyte reduction products form the solid-electrolyte interphase (SEI) on negative electrodes of lithium-ion batteries. Even though this process practically stabilizes the electrode–electrolyte interface, it results in continued capacity-fade limiting lifetime and safety of lithium-ion batteries. Recent atomistic and continuum theories give new insights into the growth of structures and the transport of ions in the SEI. The diffusion of neutral radicals has emerged as a prominent candidate for the long-term growth mechanism, because it predicts the observed potential dependence of SEI growth.     

Interfacial compatibility issues in rechargeable solid-state lithium metal batteries: a review

Solid-state lithium metal batteries(SSLBs) contain various kinds of interfaces, among which the solid electrode|solid electrolyte(ED|SE) interface plays a decisive role in the battery's power density and cycling stability. However, it is still lack of comprehensive knowledge and understanding about various interfacial physical/chemical processes so far. Although tremendous efforts have been dedicated to investigate the origin of large interfacial resistance and sluggish charge(electron/ion) transfer process, many scientific and technological challenges still remain to be clarified. In this review, we detach and discuss the critical individual challenge, including charge transfer process, chemical and electrochemical instability, space charge layers, physical contact and mechanical instability. The fundamental concepts, individual effects on the charge transfer and potential solutions are summarized based on material's thermodynamics, electrode kinetics and mechanical effects. It is anticipated that future research should focus on quantitative analysis, modeling analysis and in-situ microstructure characterizations in order to obtain an efficient manipulation about the complex interfacial behaviors in all solid-state Li batteries.     

Novel technique to form electrode–electrolyte nanointerface in all-solid-state rechargeable lithium batteries

The electrode–electrolyte nanocomposites, where the nano-sized NiS electrode with large capacity was embedded in the 80Li₂S · 20P₂S₅ electrolyte with high Li⁺ conductivity, were successfully prepared by the mechanochemical method. Contact area of solid–solid interface between the electrode and the electrolyte was remarkably increased in the nanocomposites. All-solid-state cell using the nanocomposites as a working electrode exhibited larger capacity and better cycling performance than the cell using the electrode obtained by conventional hand-mixing of powders. The mechanochemical technique sheds light on a new formation process of electrode–electrolyte interfaces endowing solid-state batteries with high power density and high energy density.     

锂离子电池介观尺度光滑粒子水力学模型

针对锂离子电池内耦合电化学反应的多物理传输过程,采用光滑粒子水力学数值技术,开发了可以考虑电极(包括隔膜)介观微结构的数值模型.以电极中固体活性物颗粒尺寸为主要考虑参数,初步探讨了该模型用于电极介观微结构设计的可行性.模型模拟得到放电过程中电池内部Li/Li+浓度场、固/液相电势场以及交换流密度等微观细节分布,以及电池宏观性能如输出电压等,据此可以分析并揭示电池放电过程的基础物理化学机制、电池宏观性能与构成电极的固体活性物颗粒尺寸之间的关联.研究还发现:当阴、阳极固体活性物颗粒尺寸均较小时,固体活性物颗粒内部Li分布更为均匀,电化学反应更均匀发生,电池输出电压最高.     

New lithium salts in electrolytes for lithium-ion batteries (Review)

The properties of electrolyte systems based on standard nonaqueous solvent composed of a mixture of dialkyl and alkylene carbonates and new commercially available lithium salts potentially capable of being an alternative to thermally unstable and chemically active lithium hexafluorophosphate LiPF₆ in the mass production of lithium-ion rechargeable batteries are surveyed. The advantages and drawbacks of electrolytes containing lithium salts alternative to LiPF₆ are discussed. The real prospects of substitution for LiPF₆ in electrolyte solutions aimed at improving the functional characteristics of lithium-ion batteries are assessed. Special attention is drawn to the efficient use of new lithium salts in the cells with electrodes based on materials predominantly used in the current mass production of lithium-ion batteries: grafitic carbon (negative electrode), LiCoO₂, LiMn₂O₄, LiFePO₄, and also solid solutions isostructural to lithium cobaltate with the general composition LiMO₂ (M = Co, Mn, Ni, Al) (positive electrode).     

锂离子电池低温性能改善研究进展

锂离子电池因其能量密度高,循环寿命长等优点已成为新型动力电池领域的研究热点,但其温度特性尤其是低温性能较差制约着锂离子电池的进一步使用. 本文综述了锂离子电池低温性能的研究进展,系统地分析了锂离子电池低温性能的主要限制因素. 从正极、电解液、负极三个方面讨论了近年来研究者们提高电池低温性能的改性方法. 并对提高锂离子电池低温性能的发展方向进行了展望.     

Nitrogen-doped carbon nanotubes by multistep pyrolysis process as a promising anode material for lithium ion hybrid capacitors

Lithium-ion hybrid capacitors (LIHCs) is a promising electrochemical energy storage devices which combines the advantages of lithium-ion batteries and capacitors. Herein, we developed a facile multistep pyrolysis method, prepared an amorphous structure and a high-level N-doping carbon nanotubes (NCNTs), and by removing the Co catalyst, opening the port of NCNTs, and using NCNTs as anode material. It is shows good performance due to the electrolyte ions enter into the electrode materials and facilitate the charge transfer. Furthermore, we employ the porous carbon material (APDC) as the cathode to couple with anodes of NCNTs, building a LIHCs, it shows a high energy density of 173 Wh/kg at 200 W/kg and still retains 53 Wh/kg at a high power density of 10 kW/kg within the voltage window of 0–4.0 V, as well as outstanding cyclic life keep 80% capacity after 5000 cycles. This work provides an opportunity for the preparation of NCNTs, that is as a promising high-performance anode for LIHCs.     

石榴石型固态电解质/铝锂合金界面构筑及电化学性能

本文通过在锂负极中熔入少量铝制备了一种含Al-Li合金（Al₄Li₉）的新型复合锂负极,可有效改善Garnet/金属锂界面润湿性,从而显著降低了界面阻抗. XRD研究结果表明这一复合锂负极由Al₄Li₉合金和金属锂两相复合而成. SEM研究表明,复合锂负极可以有效改善金属锂与Garnet电解质的界面接触,形成更为紧密的接触界面. 电化学测试表明,复合锂负极显著降低了金属锂与Garnet电解质的界面阻抗,界面阻抗由锂/Garnet电解质界面的740.6 Ω·cm ²降低到复合锂负极/Garnet电解质界面的75.0 Ω·cm ². 使用复合锂负极制备的对称电池在50 μA·cm ^-2和100 μA·cm ^-2电流密度锂沉积-溶出过程中表现出较低的极化和良好的循环稳定性,在50 μA·cm ^-2电流密度下,可以稳定循环超过400小时.     

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.     

多酚类化合物—丹宁酸用作锂金属负极电解液成膜添加剂

As the application of lithium-ion batteries in advanced consumer electronics, energy storage systems, plug-in hybrid electric vehicles, and electric vehicles increases, there has emerged an urgent need for increasing the energy density of such batteries. Lithium metal anode is considered as the "Holy Grail" for high-energy-density electrochemical energy storage systems because of its low reduction potential (-3.04 V vs standard hydrogen electrode) and high theoretical specific capacity (3860 mAh·g^-1). However, the practical application of lithium metal anode in rechargeable batteries is severely limited by irregular lithium dendrite growth and high reactivity with the electrolytes, leading to poor safety performance and low coulombic efficiency. Recent research progress has been well documented to suppress dendrite growth for achieving long-term stability of lithium anode, such as building artificial protection layers, developing novel electrolyte additives, constructing solid electrolytes, using functional separator, designing composite electrode or three-dimensional lithium-hosted material. Among them, the use of electrolyte additives is regarded as one of the most effective and economical methods to improve the performance of lithium-ion batteries. As a natural polyphenol compound, tannic acid (TA) is significantly cheaper and more abundant compared with dopamine, which is widely used for the material preparation and modification in the field of lithium-ion batteries. Herein, TA is first reported as an efficient electrolyte film-forming additive for lithium metal anode. By adding 0.15% (mass fraction, wt.) TA into the base electrolyte of 1 mol·L^-1 LiPF₆-EC/DMC/EMC (1 : 1 : 1, by wt.), the symmetric Li|Li cell exhibited a more stable cyclability of 270 h than that of only 170 h observed for the Li|Li cell without TA under the same current density of 1 mA·cm^-2 and capacity of 1 mAh·cm^-2 (with a cutoff voltage of 0.1 V). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and energy-dispersive X-ray spectroscopy (EDS) analyses demonstrated that TA participated in the formation of a dense solid electrolyte interface (SEI) layer on the surface of the lithium metal. A possible reaction mechanism is proposed here, wherein the small amount of added polyphenol compound could have facilitated the formation of LiF through the hydrolysis of LiPF₆, following which the resulting phenoxide could react with dimethyl carbonate (DMC) through transesterification to form a cross-linked polymer, thereby forming a unique organic/inorganic composite SEI film that significantly improved the electrochemical performance of the lithium metal anode. These results demonstrate that TA can be used as a promising film-forming additive for the lithium metal anode.     

A surface science approach to cathode/electrolyte interfaces in Li-ion batteries: Contact properties,charge transfer and reactions

Reactions and charge transfer at cathode/electrolyte interfaces affect the performance and the stability of Li-ion cells. Corrosion of active electrode material and decomposition of electrolyte are intimately coupled to charge transfer reactions at the electrode/electrolyte interfaces, which in turn depend on energy barriers for electrons and ions. Principally, energy barriers arise from energy level alignment at the interface and space charge layers near the interface, caused by changes of inner electric (Galvani) potential due to interfacial dipoles and concentration profiles of electronic and ionic charge carriers.In this contribution, we introduce our surface science oriented approach using photoemission (XPS, UPS) to investigate cathode/electrolyte interfaces in Li-ion batteries. After an overview of the processes at cathode/electrolyte interfaces as well as currently employed analysis methods, we present the fundamentals of contact potential formation and energy level alignment (electrons and ions) at interfaces and their analysis with photoemission. Subsequently, we demonstrate how interface analysis can be employed in Li-ion battery research, yielding new and valuable insights, and discuss future benefits.     

高锂离子电导的有机-无机复合电解质的渗流结构设计

固态聚合物电解质被认为是解决传统液态锂金属电池安全隐患和循环性能的关键材料,但仍然存在离子电导率低,界面兼容性差等问题。近年来,基于无机填料与聚合物电解质的高锂离子电导的有机-无机复合电解质备受关注。根据渗流理论,有机-无机界面被认为是复合电解质离子电导率改善的主要原因。因此,设计与优化有机-无机渗流界面对提高复合电解质离子电导率具有重要意义。本文从渗流结构的设计出发,综述了不同维度结构的无机填料用于高锂离子电导的有机-无机复合电解质的研究进展,并对比分析了不同渗流结构的优缺点。基于上述评述,展望了有机-无机复合电解质的未来发展趋势和方向。     

Unlocking Charge Transfer Limitations for Extreme Fast Charging of Li-Ion Batteries

Extreme fast charging (XFC) of high-energy Li-ion batteries is a key enabler of electrified transportation. While previous studies mainly focused on improving Li ion mass transport in electrodes and electrolytes, the limitations of charge transfer across electrode–electrolyte interfaces remain underexplored. Herein we unravel how charge transfer kinetics dictates the fast rechargeability of Li-ion cells. Li ion transfer across the cathode–electrolyte interface is found to be rate-limiting during XFC, but the charge transfer energy barrier at both the cathode and anode have to be reduced simultaneously to prevent Li plating, which is achieved through electrolyte engineering. By unlocking charge transfer limitations, 184 Wh kg⁻¹ pouch cells demonstrate stable XFC (10-min charge to 80 %) which is otherwise unachievable, and the lifetime of 245 Wh kg⁻¹ 21700 cells is quintupled during fast charging (25-min charge to 80 %).     

Artificial Solid Electrolyte Interphase Acting as “Armor” to Protect the Anode Materials for High-performance Lithium-ion Battery

The electrochemical performances of lithium-ion batteries(LIBs) are closely related to the interphase between the electrode materials and electrolytes. However, the development of lithium-ion batteries is hampered by the formation of uncontrollable solid electrolyte interphase(SEI) and subsequent potential safety issues associated with dendritic formation and cell short-circuits during cycling. Fabricating artificial SEI layer can be one promising approach to solve the above issues. This review summarizes the principles and methods of fabricating artificial SEI for three types of main anodes:deposition-type(e.g., Li), intercalation-type(e.g., graphite) and alloy-type(e.g., Si, Al). The review elucidates recent progress and discusses possible methods for constructing stable artificial SEIs composed of salts, polymers, oxides, and nanomaterials that simultaneously passivate anode against side reactions with electrolytes and regulate Li⁺ ions transport at interfaces. Moreover, the reaction mechanism of artificial SEIs was briefly analyzed, and the research prospect was also discussed.     

A systematic approach to the impedance of surface layers with mixed conductivity forming on electrodes

Electrode impedance can be evaluated on the basis of the electrode reaction kinetics in many systems, even for complicated electrode reactions. However, when a surface layer is present on the electrode surface, the theoretically well-established impedance model of the electrode reaction is often completed with phenomenological equivalent circuit elements in order to achieve the number of time constants as derived from the electrode impedance spectra measured. In these cases, the meaning of the phenomenological equivalent circuit elements are often unclear, though the presence of these elements is helpful to describe the system throughout the frequency domain used for the measurement. In the present work, an attempt will be shown to separate the effect of the electronic and ionic charge transfer in a surface layer and to identify the appropriate equivalent circuits. Examples are shown from the fields of lithium-ion batteries where a solid electrolyte interface as a surface layer is present at the negative electrode and the contribution of various charge carriers may be of importance.