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Developing high‐capacity electrodes requires the evaluation of electrochemical behaviors with an increasing current density. Currently, the current density for evaluation of high‐capacity electrodes has reached a new stage where the polarization at the lithium counter electrode has become a technical barrier for the accurate evaluation of battery electrodes, resulting in severe performance and mechanism mischaracterizations. Here, the accurate electrochemical behavior for high‐capacity electrodes via a single‐channel three‐electrode vehicle is decoupled, by which the impact of lithium counter electrode is minimized. The testing high‐capacity graphite electrode is capable of delivering an excellent rate capability with 81.7% capacity retention at 0.3 C, as well as stable cycling performance retaining 97.5% practical reversible capacity after 225 cycles, much higher than the graphite electrode tested with traditional half‐cell testing vehicle but in close agreement with the results obtained from a well‐matched full cell, reflecting accurate electrochemical performance evaluations of high‐capacity electrodes. Moreover, detailed electrochemical mechanisms of impedance and diffusion properties for working electrodes are also successfully decoupled individually. This work uncovers the mismatch between traditional evaluation configuration and increasing testing current density and provides a guideline for accurate electrochemical evaluation for ever‐increasing high‐capacity electrodes, which is of great significance for high‐energy lithium or other alkali‐metal ion batteries. [ABSTRACT FROM AUTHOR]

In past years, lithium-ion batteries (LIBs) can be found in every aspect of life, and batteries, as energy storage systems (ESSs), need to offer electric vehicles (EVs) more competition to be accepted in markets for automobiles. Thick electrode design can reduce the use of non-active materials in batteries to improve the energy density of the batteries and reduce the cost of the batteries. However, thick electrodes are limited by their weak mechanical stability and poor electrochemical performance; these limitations could be classified as the critical cracking thickness (CCT) and the limited penetration depth (LPD). The understanding of the CCT and the LPD have been proposed and the recent works on breaking the CCT and improving the LPD are listed in this article. By comprising these attempts, some thick electrodes could not offer higher mass loading or higher accessible areal capacity that would defeat the purpose. [ABSTRACT FROM AUTHOR]

A stable solid electrolyte interphase (SEI) is highly desired to prevent parasitic reactions during normal operation of lithium‐ion batteries (LIBs). Lithium carbonate (Li2CO3) is one of the most significant components for smooth SEI passivation layers; while the formation mechanism and special distribution of the Li2CO3 layer has not yet been illustrated. Here, an over‐potential tailored Li2CO3 growth mechanism based on the typical hard carbon anode is demonstrated. With an increase in the over‐potential, the size of Li2CO3 decreases gradually as the amount increases. When the over‐potential is large (potential at 0.01 V), a Li2CO3‐rich thin and dense inorganic layer with the average thickness of 4.4 nm in the SEI is constructed. The special SEI the completely wraps the boundaries of the anode enables a larger Li‐ion de‐solvation energy barrier and a lower Li‐ion diffusion energy barrier, which supports low self‐discharge behavior and a fast kinetic rate at the anode. More generally, this Li2CO3 growth mechanism is also applicable to commercialized graphite anodes and similar results are also obtained. Therefore, this work provides a new insight into the Li2CO3 growth mechanism in SEIs, as well as a guideline for the design of stable artificial SEIs. [ABSTRACT FROM AUTHOR]

Pre-lithiation is the most effective method to overcome the initial capacity loss of high-capacity electrodes and has the potential to be used in beyond-conventional lithium-ion batteries. In this article we focus on two types of pre-lithiation: the first type can be applied to batteries in which the cathode has been fully lithiated but the anode has a large initial capacity loss, such as batteries made with lithium metal oxide cathode and silicon-carbon anode. The second type can be applied to batteries in which both electrodes are initially lithium-free and suffer a loss of lithium during the initial cycles, such as batteries made with sulfurized polyacrylonitrile cathode and silicon-carbon anode. We describe the pre-lithiation procedures and electrode potential profiles during pre-lithiation corresponding to different pre-lithiation sources for both types of pre-lithiation. We also derive formulas for the theoretical specific energy and energy density that are based entirely on measurable parameters such as specific capacities, porosities, mass densities of two electrodes and extra lithium source, Coulombic efficiencies of electrodes, and the voltage of the cell. These formulas can be applied to different pre-lithiation sources to predict the specific energy of conventional and beyond conventional lithium-ion batteries as a function of the type of pre-lithiation. [ABSTRACT FROM AUTHOR]

Next‐generation Li‐ion batteries (LIBs) with higher energy density adopt some novel anode materials, which generally have the potential to exhibit higher capacity, superior rate performance as well as better cycling durability than conventional graphite anode, while on the other hand always suffer from larger active lithium loss (ALL) in the first several cycles. During the last two decades, various pre‐lithiation strategies are developed to mitigate the initial ALL by presetting the extra Li sources to effectively improve the first Coulombic efficiency and thus achieve higher energy density as well as better cyclability. In this progress report, the origin of the huge initial ALL of the anode and its effect on the performance of full cells are first illustrated in theory. Then, various pre‐lithiation strategies to resolve these issues are summarized, classified, and compared in detail. Moreover, the research progress of pre‐lithiation strategies for the representative electrochemical systems are carefully reviewed. Finally, the current challenges and future perspectives are particularly analyzed and outlooked. This progress report aims to bring up new insights to reassess the significance of pre‐lithiation strategies and offer a guideline for the research directions tailored for different applications based on the proposed pre‐lithiation strategies summaries and comparisons. [ABSTRACT FROM AUTHOR]

Pre-lithiation plays an increasingly significant role for high-energy Li-ion batteries (LIBs) since it can improve the energy density by compensating the Li loss during the initial cycle. The pre-lithiation related research so far has been focused on the development of materials and methods of pre-lithiation but has lacked theoretical and mathematical descriptions to illustrate the relationship between pre-lithiation and energy density. In this contribution, a series of mathematical formulas are derived to describe the gravimetric and volumetric energy densities of LIBs with pre-lithiation, by which the effects of the important parameters, e.g. the Coulombic efficiencies (CEs) of anode, the capacities of Li sources, etc., on the energy densities are well demonstrated. Then, the developed theory and mathematical formulas are applied to practical LIB systems, i.e. the cell using Li nickel manganese cobalt oxide (NMC) as a cathode and silicon-carbon (Si-C) composite as an anode, to identify possible energy density improvement after pre-lithiation. These systematic formulas with great universality have the potential to give significant guidelines for future studies on the pre-lithiation methods and be useful tools for the design of high energy LIBs with imperfect CEs from fundamental and practical perspectives. [ABSTRACT FROM AUTHOR]

Pre-lithiation is an essential technique for development of Li-ion sulfur batteries (LISBs), which have lower cost and higher durability than conventional Li-ion batteries. Herein, a simple and scalable pre-lithiation approach by direct contact with lithium foil is applied to a sulfur-polyacrylonitrile (S-PAN) cathode to construct LISBs, which exhibit an initial capacity of 1367 mAh g−1 and maintain 1192 mAh g−1 after 100 cycles. Moreover, we demonstrate the feasibility of proposed method on both electrodes for performance enhancement. The theoretical estimation further demonstrates the potential of the system for achieving high specific capacity and good cycle life at low cost. [ABSTRACT FROM AUTHOR]

Li2TiSiO5 was recently proposed as a Ti‐based anode material for lithium‐ion batteries (LIBs), with the desirable characteristics of low discharge potential and relatively high specific capacity. However, the intrinsically poor electronic and ionic conductivities give rise to its sluggish electrochemical performance. In this work, Li2TiSiO5 modified with a dual‐carbon network (C@LTSO/CNT) is developed by performing a facile synthesis. The obtained dual‐carbon network coupled with small‐sized LTSO particles delivers enhanced electron conductivity frameworks, abundant active interfaces, and a notably higher inner porosity for multidirectional ion diffusion. Such a unique architecture leads to a high specific capacity as well as an ultrafast electrochemical process for LTSO through remarkable electronic and ionic transfer. C@LTSO/CNT electrodes with a low discharge plateau at 0.28 V achieve an extremely competitive specific capacity of over 430 mAh g−1 at 0.5 C, a superb high‐rate performance over 125 mAh g−1 up to 10 C, and a stable cycle lifespan of 1500 cycles without any degradation, displaying significant potential as an ideal anode candidate. Thus, a high‐performance LIB full cell is fabricated with a C@LTSO/CNT anode and a LiFePO4 cathode. This cell shows an energy density of 200 Wh kg−1 with greatly improved properties of high‐power density and pronounced cycling stability. [ABSTRACT FROM AUTHOR]

Si nanoparticles and multi-walled carbon nanotubes (MWNTs) were combined using the simple, inexpensive, and scalable approach involving ultrasonication and positive-pressure filtration to generate binder-free freestanding flexible Si–MWNT (Si–MW) composite paper anodes for Li-ion batteries. Through controlling the Si/carbon nanotube (CNT) weight ratio, the composite with 3:2 Si/CNT ratio exhibited the optimal balance between the high capacity of SiNPs and high conductivity and structural stabilization quality of MWNTs, leading to high rate capability as well as specific capacity and cyclability surpassing the conventional slurry-cast SiNP electrode using binder and current collector and other complicated freestanding Si/carbon composite designs. After 100 cycles, our electrode retained a capacity of 1170 mA h/g at 100 mA/g and 750 mA h/g at 500 mA/g. Moreover, a different electrolyte composition enabled a reversible capacity of 1300 mA h/g at 100 mA/g after 100 cycles. The freestanding feature of our electrodes is promising for enhanced energy density of Li-ion cells. [ABSTRACT FROM AUTHOR]

Lithium-ion capacitors (LICs) were investigated for high power, moderate energy density applications for operation in extreme environments with prolonged cycle-life performance. The LICs were assembled as three-layered pouch cells in an asymmetric configuration employing Faradaic pre-lithiated hard carbon anodes and non-Faradaic ion adsorption-desorption activated carbon (AC) cathodes. The capacity retention was measured under high stress conditions, while the design factor explored was electrolyte formulation using a set of carbonates and electrolyte additives, with a focus on their stability. The LIC cells were evaluated using critical performance tests under the following high stress conditions: long-term voltage floating-cycling stability at room temperature (2.2–3.8 V), high temperature storage at 3.8 V, and charge voltages up to 4.4 V. The rate performance of different electrolytes and additives was measured after the initial LIC cell formation for a 1C–10C rate. The presence of vinylene carbonate (VC) and tris (trimethylsilyl) phosphate (TMSP) were found to be essential to the improved electrochemical performance of the LIC cells under all testing conditions. [ABSTRACT FROM AUTHOR]

Abstract: Equivalent circuit model (EMC) of a high-power Li-ion battery that accounts for both temperature and state of charge (SOC) effects known to influence battery performance is presented. Electrochemical impedance measurements of a commercial high power Li-ion battery obtained in the temperature range 20 to 50°C at various SOC values was used to develop a simple EMC which was used in combination with a non-linear least squares fitting procedure that used thirteen parameters for the analysis of the Li-ion cell. The experimental results show that the solution and charge transfer resistances decreased with increase in cell operating temperature and decreasing SOC. On the other hand, the Warburg admittance increased with increasing temperature and decreasing SOC. The developed model correlations that are capable of being used in process control algorithms are presented for the observed impedance behavior with respect to temperature and SOC effects. The predicted model parameters for the impedance elements R s , R ct and Y 013 show low variance of 5% when compared to the experimental data and therefore indicates a good statistical agreement of correlation model to the actual experimental values. [Copyright &y& Elsevier]

Abstract: A polymer gel electrolyte has been prepared based on polyvinyl alcohol, lithium salt and organic solvent N-methyl-2-pyrrolidone (NMP). This gel has the potential for use in secondary batteries and electrochemical capacitors. The conductivity of this gel electrolyte can be as high as 2×10−3–5.8×10−4 S/cm at room temperature. Functioning as separator and electrolyte, this gel system was used to evaluate the specific capacitance of an electrochemical capacitor with carbon nanotube films as the active electrodes. [Copyright &y& Elsevier]