Lithium‐ion capacitors (LICs) are assembled with a battery‐type anode and a capacitor‐type cathode, so they combine high energy density of lithium‐ion batteries (LIBs) and excellent rate and cycling performance of supercapacitors (SCs). However, the current level still cannot satisfy the target. And the leading problem is LICs cannot offer enough capacity under high power density and long cycling life due to the storage mechanism of anodes. This paper gives the present attempts on electrodes, solid–electrolyte interface (SEI) and operation conditions. And after discussion, the paper holds that the discharge voltage plateau of anodes should be well‐chosen, and the anode structure like an ordered mesoporous structure can provide fast and versatile transport pathways for charge transfer and provide free space to accommodate the volume change upon Li‐ions insertion/extraction. In addition, the multilayer SEI with the synergism like LiF and Li2CO3 can provide better electronic insulation and ion conductivity. Furthermore, appropriate working potential is also an effective mean to improve performance of LICs.

storage systems (ESSs) to mitigate the intrinsically intermittent nature of renewable energy sources. [1] Lithium-ion batteries (LIBs), one of the most mature electrochemical ESSs, undergo rapid development and have widespread applications in portable devices, (hybrid) electric vehicles, as well as grid storage. [2] With the ever-growing demands for energy density, various novel materials (e.g., silicon), as well as electrode technologies (e.g., ultra-thick electrode), have been proposed for high-capacity applications as shown in Figure 1a. [3] There is a consistent trend/ need to evaluate the electrochemical behaviors of the high-capacity electrode using an increasing current density to match state-of-the-art lithium-ion technologies, e.g. the initial testing current for mechanism analysis of graphite in the 1990s was 0.2 mA cm −2 ; [4] while it goes to 10 mA cm −2 for performance competition of modern electrodes, equivalent to a 50-fold increase. [5] Along with the progress of electrode materials and technologies, less progress was made to parallelly upgrade the electrochemical evaluation methods. In 1980s, the classic three-electrode Pyrex glass cell with Li metal as the reference electrode was replaced by the two-electrode coin cell configuration with reduced distance between electrodes and amount of electrolyte to eliminate the non-negligible parasitic current and undesirable ohmic resistance. [6] Since then, the two-electrode coin-cell-type half-cells with Li metal as counter and reference electrodes have been the 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 singlechannel 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 highcapacity electrodes, which is of great s...

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.

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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 could reduce the use of non-active materials in batteries that its energy density would be improved and its cost would be cut. 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.