Frontispiece: Stainless Steel-Like Passivation Inspires Persistent Silicon Anodes for Lithium-Ion Batteries

Passivation of stainless steel by additives forming mass-transport blocking layers is widely practiced, where Cr element is added into bulk Fe−C forming the Cr₂O₃-rich protective layer. Here we extend the long-practiced passivation concept to Si anodes for lithium-ion batteries, incorporating the passivator of LiF/Li₂CO₃ into bulk Si. The passivation mechanism is studied by various ex situ characterizations, redox peak contour maps, thickness evolution tests, and finite element simulations. The results demonstrate that the passivation can enhance the (de)lithiation of Li-Si alloys, induce the formation of F-rich solid electrolyte interphase, stabilize the Si/LiF/Li₂CO₃ composite, and mitigate the volume change of Si anodes upon cycling. The 3D passivated Si anode can fully retain a high capacity of 3701 mAh g⁻¹ after 1500 cycles and tolerate high rates up to 50C. This work provides insight into how to construct durable Si anodes through effective passivation.     

锂离子电池快充石墨负极研究与应用

Driven by the excessive environmental pollution caused by the over-use of non-renewable fossil-derived energy, renewable energy and electrochemical energy storage devices have made great progress in the past decades. Electrochemical energy storage devices, such as lithium-ion batteries, have the advantages of high capacity, long life cycle, and good safety performance; therefore, they have been used in various applications. For example, economical and environment-friendly electric vehicles have recently taken up increasing market share. However, when compared with vehicles propelled using fossil-derived energy, the slow charging speed of electric vehicles has always restricted their further promotion. The realization of rapid charging for electric vehicles can alleviate the high-pressure usage of charging piles as well as increase the application and market share of electric vehicles. Therefore, it is important to develop high-performance lithium-ion batteries with rapid charge and discharge capacities. The fast-charging capacity of lithium-ion batteries is limited by the slow migration of lithium ions in the electrode and the electrode/electrolyte interface. Therefore, the key to developing fast-charging lithium-ion batteries lies in the successful design of suitable electrode materials. Because of its low cost and excellent electrochemical performance, graphite has been widely used to develop the cathode of lithium-ion batteries. However, the migration of lithium ions in graphite is slow, resulting in large polarization during the high-current charge and discharge processes. In addition, the low lithium intercalation potential of graphite leads to lithium precipitation during fast charging, which can decrease the electrochemical performance and cause potential safety hazards. Therefore, graphite must be improved to meet the needs of such fast-charging devices. In this article, we systematically introduce the research progress made in recent years within the scope of rapid-charging improvement of graphite(-based) cathodes and then highlight the modification strategies for graphite with the goal of achieving functional coating, desired morphological and structural design, optimized electrolyte properties, and an improved charging protocol. Additionally, this article evaluates the advantages and disadvantages of the modification strategies as well as their application prospects. The scheme of functional coating for modifying graphite must simplify the process and improve production efficiency to meet the needs of industrial development. Morphology design should ensure satisfactory initial Coulomb efficiency, while the improvement of the electrolyte properties and optimization of the charging protocol need to consider the commercialization costs. Finally, this paper proposes further evaluation of the effects of the modification strategies based on soft-pack or cylindrical batteries to strengthen the commercialization prospect of the modification strategies.      

锂离子电池快充石墨负极研究与应用

相较于传统燃油汽车,电动汽车缓慢的充电速度始终制约了其进一步推广。为电动汽车实现“加油式”快速充电能够缓解充电桩的使用压力,增加电动汽车的应用场景和市场占有率。因此,亟需开发出具有快速充放电能力的高性能锂离子电池。石墨因其低廉的价格和优异的电化学性能已经在锂离子电池负极领域得到了广泛的商业化应用,然而其较低的嵌锂电位导致在快充过程中出现析锂,损害电化学性能的同时会带来安全隐患。因此,必须对石墨进行改良处理,以适应快充技术的需要。本文系统介绍了近年来石墨负极快充化改良领域的研究进展,从成分设计,形貌调控,结构优化,电解液适配等方面进行了评述,并总结了快充石墨面临的挑战,展望了其发展前景,为推动快充技术的商业化应用提供了借鉴。     

多孔锂-硅薄膜锂离子电池负极材料的电沉积制备及其电化学性能

采用多步恒电流沉积技术, 在铜箔上电沉积制备了多孔锂-硅薄膜电极(LSF). 用X射线衍射(XRD)和扫描电镜(SEM)测试手段研究了该电极的结构和表面形貌. 作为锂离子电池负极材料, 电化学测试结果表明锂-硅薄膜电极具有较好的循环稳定性, 通过改变电沉积条件, 可有效调控该电极的嵌脱锂容量及首次循环效率. 譬如, 在0.5 mol·L^-1四氯化硅+0.7 mo·L^-1高氯酸锂的碳酸丙烯酯电解液中, 首先以-3.82 mA·cm^-2的恒定电流密度沉积600 s, 再将电流密度恒定为-1.27 mA·cm^-2, 继续电沉积7200 s, 制得锂-硅薄膜电极(LSF^-3), 该电极以12.7 μA·cm^-2的电流密度预循环2次, 其首次循环库仑效率高达97.1%. 预循环2次后, 电流密度增加到25.5 μA·cm^-2, 此时,锂-硅薄膜电极充电质量比容量和面积比容量分别为1410 mAh·g^-1及240.6 μAh·cm^-2; 50次循环后充电比容量为179 μAh·cm^-2 (1049 mAh·g^-1), 容量保持率为74.4%. 锂-硅薄膜电极中的活性锂组分可补偿首次循环时不可逆容量损失, 同时薄膜电极中的多孔结构可缓解电极材料的体积效应并改善其循环性能.     

锂离子电池Sn-Co-Zn合金负极材料电沉积及其储锂性能

运用电沉积技术制备出Sn-Co-Zn合金电极材料.采用X射线衍射(XRD)和扫描电子显微镜(SEM)分析了该合金材料的相结构和表面形貌.通过循环伏安和电位阶跃实验研究了Sn-Co-Zn合金的电沉积机理,实验表明,Sn-Co-Zn合金电沉积按扩散控制连续成核和三维生长方式进行.XRD结果表明,该合金由CoSn3、Co3Sn2和Zn组成.电化学性能测试表明:Sn-Co-Zn合金电极首次放电(脱锂)容量达751mAh·g-1,首次循环的库仑效率为88%;30周循环之后放电容量为510mAh·g-1.该Sn-Co-Zn合金电极良好的电化学储锂性能可能归因于材料的多相结构.     

核壳结构金属-有机骨架及其衍生物在锂离子电池负极材料中的应用

金属-有机骨架(MOFs)材料具有比表面积较大、孔径可调、制备容易、结构与功能多样性等优势,被广泛应用于电化学能源转化与储存领域。其中独特的核壳结构材料由于表面修饰的作用往往更能表现出内核与壳层之间的协同作用。本文介绍了核壳结构MOFs作为锂离子电池负极材料的发展现状,并重点综述其衍生物(多孔碳材料、金属氧化物、金属硫/硒化物以及金属/金属氧化物)的制备方法以及在锂离子电池负极中的应用。MOFs经高温煅烧或改变化学反应条件可制备出结构可调的无机电极材料并表现出更优异的电化学性能。最后总结了核壳结构MOFs材料作为锂电负极材料存在的问题和挑战,并提出可能的解决途径和未来的应用前景。     

三元锂离子电池容量衰减机理研究进展

三元锂离子电池主要是指使用镍钴锰酸锂(NCM)或镍钴铝酸锂(NCA)作为正极材料的锂离子电池,三元锂离子电池广泛应用于电动汽车、3C电子产品、储能等领域。然而,三元锂离子电池的循环寿命已成为其进一步发展的最大障碍,因此了解三元锂离子电池的容量衰退机理具有重要意义。三元锂离子电池的衰退机理主要包括五个方面:晶体结构的改变和相变、活性材料的损失、电解质的分解和消耗、可脱嵌锂离子的损耗以及固体电解质界面的形成。本文总结了近年来相关方面的研究进展,以期更全面地总结三元锂离子电池的容量衰减机理,并对三元锂离子电池的应用前景进行了展望。     

Probing Degradation in Lithium Ion Batteries with On-Chip Electrochemistry Mass Spectrometry**

The rapid uptake of lithium ion batteries (LIBs) for large scale electric vehicle and energy storage applications requires a deeper understanding of the degradation mechanisms. Capacity fade is due to the complex interplay between phase transitions, electrolyte decomposition and transition metal dissolution; many of these poorly understood parasitic reactions evolve gases as a side product. Here we present an on-chip electrochemistry mass spectrometry method that enables ultra-sensitive, fully quantified and time resolved detection of volatile species evolving from an operating LIB. The technique's electrochemical performance and mass transport is described by a finite element model and then experimentally used to demonstrate the variety of new insights into LIB performance. We show the versatility of the technique, including (a) observation of oxygen evolving from a LiNiMnCoO₂ cathode and (b) the solid electrolyte interphase formation reaction on graphite in a variety of electrolytes, enabling the deconvolution of lithium inventory loss (c) the first direct evidence, by virtue of the improved time resolution of our technique, that carbon dioxide reduction to ethylene takes place in a lithium ion battery. The emerging insight will guide and validate battery lifetime models, as well as inform the design of longer lasting batteries.     

Irreparable Interphase Chemistry Degradation Induced by Temperature Pulse in Lithium-Ion Batteries

While it is widely recognized that the operating temperature significantly affects the energy density and cycle life of lithium-ion batteries, the consequence of electrode-electrolyte interphase chemistry to sudden environmental temperature changes remains inadequately understood. Here, we systematically investigate the effects of a temperature pulse (T pulse) on the electrochemical performance of LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) pouch full cells. By utilizing advanced characterization tools, such as time-of-flight secondary-ion mass spectrometry, we reveal that the T pulse can lead to an irreversible degradation of cathode-electrolyte interphase chemistry and architecture. Despite negligible immediate impacts on the solid-electrolyte interphase (SEI) on graphite anode, aggregated cathode-to-anode chemical crossover gradually degrades the SEI by catalyzing electrolyte reduction decomposition and inducing metallic dead Li formation because of insufficient cathode passivation after the T pulse. Consequently, pouch cells subjected to the T pulse show an inferior cycle stability to those free of the T pulse. This work unveils the effects of sudden temperature changes on the interphase chemistry and cell performance, emphasizing the importance of a proper temperature management in assessing performance.     

Quantifying Degradation Parameters of Single-Crystalline Ni-Rich Cathodes in Lithium-Ion Batteries

Single-crystal LiNi_xCo_yMn_zO₂ (SC-NCM, x+y+z=1) cathodes are renowned for their high structural stability and reduced accumulation of adverse side products during long-term cycling. While advances have been made using SC-NCM cathode materials, careful studies of cathode degradation mechanisms are scarce. Herein, we employed quasi single-crystalline LiNi_0.65Co_0.15Mn_0.20O₂ (SC-NCM65) to test the relationship between cycling performance and material degradation for different charge cutoff potentials. The Li/SC-NCM65 cells showed >77 % capacity retention below 4.6 V vs. Li⁺/Li after 400 cycles and revealed a significant decay to 56 % for 4.7 V cutoff. We demonstrate that the SC-NCM65 degradation is due to accumulation of rock-salt (NiO) species at the particle surface rather than intragranular cracking or side reactions with the electrolyte. The NiO-type layer formation is also responsible for the strongly increased impedance and transition-metal dissolution. Notably, the capacity loss is found to have a linear relationship with the thickness of the rock-salt surface layer. Density functional theory and COMSOL Multiphysics modeling analysis further indicate that the charge-transfer kinetics is decisive, as the lower lithium diffusivity of the NiO phase hinders charge transport from the surface to the bulk.     

Revealing the Interfacial Chemistry of Fluoride Alkyl Magnesium Salts in Magnesium Metal Batteries

Exploring promising electrolyte-system with high reversible Mg plating/stripping and excellent stability is essential for rechargeable magnesium batteries (RMBs). Fluoride alkyl magnesium salts (Mg(OR^F)₂) not only possess high solubility in ether solvents but also compatible with Mg metal anode, thus holding a vast application prospect. Herein, a series of diverse Mg(OR^F)₂ were synthesized, among them, perfluoro-tert-butanol magnesium (Mg(PFTB)₂)/AlCl₃/MgCl₂ based electrolyte demonstrates highest oxidation stability, and promotes the in situ formation of robust solid electrolyte interface. Consequently, the fabricated symmetric cell sustains a long-term cycling over 2000 h, and the asymmetric cell exhibits a stable Coulombic efficiency of 99.5 % over 3000 cycles. Furthermore, the Mg||Mo₆S₈ full cell maintains a stable cycling over 500 cycles. This work presents guidance for understanding structure–property relationships and electrolyte applications of fluoride alkyl magnesium salts.     

Sn Anodes Protected by Intermetallic FeSn2 Layers for Long-lifespan Sodium-ion Batteries with High Initial Coulombic Efficiency of 93.8 %

With a theoretical capacity of 847 mAh g⁻¹, Sn has emerged as promising anode material for sodium-ion batteries (SIBs). However, enormous volume expansion and agglomeration of nano Sn lead to low Coulombic efficiency and poor cycling stability. Herein, an intermetallic FeSn₂ layer is designed via thermal reduction of polymer-Fe₂O₃ coated hollow SnO₂ spheres to construct a yolk-shell structured Sn/FeSn₂@C. The FeSn₂ layer can relieve internal stress, avoid the agglomeration of Sn to accelerate the Na⁺ transport, and enable fast electronic conduction, which endows quick electrochemical dynamics and long-term stability. As a result, the Sn/FeSn₂@C anode exhibits high initial Coulombic efficiency (ICE=93.8 %) and a high reversible capacity of 409 mAh g⁻¹ at 1 A g⁻¹ after 1500 cycles, corresponding to an 80 % capacity retention. In addition, NVP//Sn/FeSn₂@C sodium-ion full cell shows outstanding cycle stability (capacity retaining rate of 89.7 % after 200 cycles at 1 C).     

Decreasing Irreversible Capacity of Graphite Electrodes in Lithium-Ion Batteries by Direct Contact of Graphite with Metallic Lithium

The feasibility of reducing the irreversible capacity of negative graphite electrodes in lithium-ion batteries by a direct contact of such electrodes with lithium in the electrolyte is studied. It is shown that the dynamics of the formation of the passive film on graphite and the degree of the decrease in the irreversible capacity depend on the ratio between weights of graphite and lithium in contact. This method of reducing the irreversible capacity does not diminish the reversible capacity of graphite during the cycling. The irreversible capacity of the initial graphite cycled in 1 M LiPF₆ in a mixture of propylene carbonate and diethyl carbonate at a current density of 20 mA g^–1 is 550–1150 mA h g^–1. The reversible capacity of electrodes cycled in the same conditions reaches 290 mA h g^–1.     

二次离子电池高比容量负极碳载体的研究进展

二次离子电池商业化负极石墨的比容量已接近理论比容量. 合金型负极和金属负极因具有高比容量而受到广泛关注, 但其循环性能差和安全性问题限制了实际应用, 据此提出载体设计策略. 碳材料具有来源广泛、 易于调控等特性, 常用作二次离子电池高比容量负极的载体. 本文从碳载体的孔结构、 比表面积、 电子导电率、 离子导电率、 杂原子掺杂和界面修饰的角度出发, 综述了其在硅基、 磷基、 锗基、 锡基负极以及金属锂、 钠等负极中的研究进展, 展望了碳载体的发展前景和方向.     

Influencing Factors on Li-ion Conductivity and Interfacial Stability of Solid Polymer Electrolytes,Exampled by Polycarbonates,Polyoxalates and Polymalonates

The application of solid polymer electrolytes (SPEs) in all-solid-state(ASS) batteries is hindered by lower Li⁺-conductivity and narrower electrochemical window. Here, three families of ester-based F-modified SPEs of poly-carbonate (PCE), poly-oxalate (POE) and poly-malonate (PME) were investigated. The Li⁺-conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li⁺, the Li⁺-conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl-units are observed more effective than −O−CH₂−CF₂−CF₂−CH₂−O− during the in situ passivation of Li-metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li-metal and high-voltage-cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl-group in malonate and the suppression of enol isomerization. The coordinating capability with Li⁺, molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.     

锂离子电池硅氧化物负极首次库伦效率的影响因素与提升策略

硅氧化物(SiO_x, 0<x≤2)具有高的比容量和低的嵌锂电位, 且体积膨胀率显著低于纯硅负极, 因而被认为是替代传统石墨负极材料的理想选择之一. 然而SiO_x负极在首次嵌锂过程中表面形成的固体电解质界面膜(SEI)以及大量的不可逆产物, 造成其首次库伦效率偏低, 严重阻碍了SiO_x负极的实际应用. 本文从SiO_x的结构模型出发, 系统阐述了SiO_x负极的嵌锂机理以及首次库伦效率低的原因; 归纳了SiO_x负极首次库伦效率的提升策略及其研究进展; 并对提升SiO_x负极首次库伦效率的未来发展方向进行了展望.     

Reaction Mechanisms of the Degradation of Fluoroethylene Carbonate,an Additive of Lithium-Ion Batteries,Unraveled by Radiation Chemistry

Numerous additives are used in the electrolytes of lithium-ion batteries, especially for the formation of an efficient solid electrolyte interphase at the surface of the electrodes. Understanding the degradation processes of these compounds is thus important; they can be seen through radiolysis. In the case of fluoroethylene carbonate (FEC), picosecond pulse radiolysis experiments evidenced the formation of FEC^.−. This radical is stabilized in neat FEC, whereas the ring opens to form more stable radical anions when FEC is a solute in other solvents, as confirmed by quantum chemistry calculations. In neat FEC, pre-solvated electrons primarily undergo attachment rather than solvation. On long timescales, the gases produced (H₂, CO, and CO₂) were quantified. A reaction scheme for both the oxidizing and reducing pathways at stake in irradiated FEC is proposed. This work shows that the nature of the primary species formed in FEC depends on the amount of FEC in the solution.     

分光光度法测定益本昌类药酒中微量锗

用苯基荧光酮-溴化十六烷基三甲基铵分光光度法测定了益本昌药酒和益本昌风湿骨痛药酒中锗含量.结果显示,益本昌风湿骨痛药酒中锗含量(1.8512±0.0376 mg/L)比益本昌药酒(0.5481±0.0169 mg/L)丰富.探讨了该类药酒中锗与疗效的关系.     

Electrochemical Behavior of Polypyrrole‐modified SnS2 for Use as Anode Material in Lithium‐Ion Batteries

SnS₂/polypyrrole (PPy) composites were successfully synthesized by PPy modification of SnS₂ via a simple and effective solvothermal and chemical method. The microstructure, morphology, electrical conductivity, PPy content, and electrochemical properties of these materials were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), four‐point probe technique, thermogavimetry (TG), and constant‐current charge/discharge tests, respectively. The results demonstrate that PPy is tightly coated on the 3D flower‐like SnS₂ and that the conductivity of SnS₂ /PPy composites can be greatly improved by the PPy modification. The electrochemical results indicate that PPy is not involved in the electrode reaction, but it can dramatically improve the reversible capacity and cyclic performance. The recharge capacity retention after 30 cycles remained at 523 mAh/g, which is significantly higher than that of SnS₂ without modification by PPy. The better cycling performance compared to SnS₂ nanoparticles should be due to the 3D nano‐flower‐like SnS₂ particles and the modification of SnS₂ by PPy.     

碱式模式氢化物发生原子荧光法测定食用菌中痕量锗

研究了碱式模式氢化物发生原子荧光法测定痕量锗。考察了HG－AFS仪器参数及氢化物发生条件对锗荧光强度的影响以及常见共存元素的干扰。在选定的最佳工作条件下,测定了真菌中的痕量锗。方法检出限（3σ）为0.76μg/L,相对标准偏差(RSD)为0.81％,回收率为94.6％－101.3％。