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The fast growth experienced by the field of lithium‐ion capacitors (LICs) in the last five years led to tremendous progress in this technology. However, the authors have observed some parallelism with its ultracapacitor (UC) sister technology, where an over‐rapid growth in the last decade resulted in a loss of focus and the need of several tutorials for reconducting incorrect reporting habits. In the light of what may be coming, the authors aim to set this work as a direction to the scientific community and the new researchers in the field to serve as i) a retrospective analysis of the original target for LICs to prevent focus deviation and ii) a guideline for proper LIC design and assembly toward high energy, high power, and long cycle life, as well as for correct electrochemical characterization and reporting. The underlying thread throughout this report is the technology behind the frontrunner LIC ULTIMO, a reference device in the market that presents 3–4 times the energy density of an UC and can stand over 1 million cycles, unraveled by means of ante‐mortem analysis. [ABSTRACT FROM AUTHOR]

In this work, we are presenting both lithium and sodium ion capacitors (LIC and NIC) entirely based on electrodes designed from recycled olive pit bio-waste derived carbon materials. On the one hand, olive pits were pyrolized to obtain a low specific surface area semigraphitic hard carbon to be used as the ion intercalation (battery-type) negative electrode. On the other hand, the same hard carbon was chemically activated with KOH to obtain a high specific surface area activated carbon that was further used as the ion-adsorption (capacitor-type) positive electrode. Both electrodes were custom-made to be assembled in a hybrid cell to either build a LIC or NIC in the corresponding Li- and Na-based electrolytes. For comparison purposes, a symmetric EDLC supercapacitor cell using the same activated carbon in 1.5 M Et 4 NBF 4 /acetonitrile electrolyte was also built. Both LIC and NIC systems demonstrate remarkable energy and power density enhancement over its EDLC counterpart while showing good cycle life. This breakthrough offers the possibility to easily fabricate versatile hybrid ion capacitors, covering a wide variety of applications where different requirements are demanded. [ABSTRACT FROM AUTHOR]

The dream of using beyond-carbon metalloids or transition metals as anode materials in electrochemical energy storage systems has been long pursued for the sake of greater capacity. However, two major challenges remain unresolved: the high volumetric expansion suffered by those materials, causing severe mechanical stress ending up in device failure, and the large first cycle irreversibility. In this work, we tackle both in a single approach, by using titanium to buffer mechanical stress of antimony (TiSb 2) and by adopting the recently proven dilithium squarate sacrificial salt (Li 2 C 4 O 4) strategy to pre-lithiate the system. Overall, herein developed alloy-based lithium-ion capacitor (LIC) demonstrates between double and triple volumetric performance respect to a dual carbon LIC. Moreover, the system is shown to be stable over 20000 cycles and 1000 h of floating at 3.8 V and room temperature. Post-mortem analysis correlates the origin of failure to the electrolyte oxidation and not to the degradation of the alloying material itself. Re-assembled TiSb 2 , AC, and full device with fresh electrolyte show to almost perform as good as the originals. [Display omitted] • Lithium-ion capacitor based on alloying TiSb 2 and activated carbon. • TiSb 2 is pre-lithiated by using a sacrificial salt, namely, Li 2 C 4 O 4. • LIC is stable over 20000 cycles. • LIC is stable over 1000 h floating at 3.8V. • Post-mortem analysis reveals electrolyte degradation to be the source of failure. [ABSTRACT FROM AUTHOR]

The viability of the sodium-ion batteries as a post-lithium storage technology is strongly tied to the development of high-performance carbonaceous anode materials. This requires screening novel precursors, and tuning their electrochemical properties. Soft carbons as promising anode materials, not only for batteries, but also in hybrid capacitors, have drawn great attention, due to safe operation voltage and high-power properties. Herein, several vinyl polymer-derived soft carbons have been prepared via pyrolysis, and their physicochemical and sodium storage properties have been evaluated. According to the obtained results, vinyl polymers are a promising source for preparation of soft carbon anode materials for sodium-ion battery application. In addition, their applicability towards Li-ion battery and hybrid capacitors (e.g., Li ion capacitors, LICs) has been examined. This work not only contrasts the carbonization products of these polymers with relevant physicochemical characterization, but also screens potential precursors for soft carbons with interesting alkali metal-ion (e.g., Na or Li, with an emphasis on Na) storage properties. This can stimulate further research to tune and improve the electrochemical properties of the soft carbons for energy storage applications. [ABSTRACT FROM AUTHOR]

Herein we report an easy, ecofriendly and cheap synthetic approach for the preparation of carbon composites from the pyrolysis and activation of coffee waste and graphene oxide, and their evaluation as potential electrodes for lithium ion capacitors (LICs). An exhaustive optimization of some important parameters such as particle size, electronic conductivity or mass loading has been done for the battery-type electrode; whereas the optimum combination of specific surface area and pore size distribution were also investigated for the capacitor-type electrode. Optimized electrodes allowed to go one step beyond the state-of-the-art of biowaste based dual carbon LICs in terms of energy, power and cyclability. Assembled LICs show values of 100 Wh kg−1 AM at 9000 W kg−1 AM and retain above 80% of the initial capacitance after 3000 cycles, which is enhanced to 15,000 cycles by decreasing the voltage window. New carbon composites obtained from coffee waste and graphene oxide through a very simplistic and ecofriendly approach are proposed as electrodes for lithium ion capacitors. Image 1 [ABSTRACT FROM AUTHOR]

Abstract In this work, a lithium ion capacitor (LIC) based on carbon electrodes prepared from furfuryl alcohol-derived polymers is presented. While furfuryl alcohol is not a new carbon precursor, it has been evaluated in the past mainly for negative electrodes with Li-ion insertion. Here we describe both an activated carbon (AC) and a hard carbon (HC) made from the same furfuryl alcohol-derived polymers, for both electrodes of the LIC. The polymerization technique used to make carbon from the furfuryl alcohol precursor is different from all the methods described earlier, and is flexible enough to make soft, high surface area AC, as well as a denser, low surface area HC. The HC and the HC-based negative electrode used in this study are targeted at a high-energy and high-power LIC application by specifically reducing the carbon particle size to sub-micrometric levels, using a HC with a specific surface area of ∼300 m2 g−1 and keeping the electrode mass loading to <2 mg cm−2. The HC delivers a stable capacity of ∼400 mAh g−1 vs. Li+/Li at C/10, with excellent capacity retention of 50% at 10C (>200 mAh g−1) and 25% at 50C (∼100 mAh g−1). The AC used for the capacitor-type positive electrode was activated to a specific surface area of ∼1670 m2 g−1. For comparison purposes, a symmetric electric double layer capacitor (EDLC) using the same AC, in a 1.5 M Et 4 NBF 4 (acetonitrile) electrolyte, was also fabricated. Overall, the LIC showed considerably higher energy density over its EDLC counterpart, delivering a maximum energy density (based on the total electrode active mass weight) of 150 Wh kg−1 AM at a power density of 150 W kg−1 AM , with a 66% retention of the initial energy at the highly demanding 10,000 W kg−1 AM power peak point. Additionally, long cycle life was measured, with 83% capacitance retention after 10,000 cycles. Graphical abstract Image 1 Highlights • Synthesis of Hard Carbon and Activated Carbon from furfuryl alcohol. • Development of ultrafast performing Hard Carbon (<100 mAh g−1 at 50C). • Fabrication of Lithium Ion Capacitor with mass balance 1:2 (HC:AC). • Fabrication of Lithium Ion Capacitor exceeding 100 Wh Kg−1 AM at 10 KW Kg−1 AM. • Lithium Ion Capacitor with 83% capacity retention after 10,000 cycles. [ABSTRACT FROM AUTHOR]

The effort to increase the energy density of conventional electric double-layer capacitors (EDLCs) goes through the development of lithium-ion capacitors (LICs). Herein, we report a self-standing, binder-free composite as the battery-type negative electrode obtained by a low-cost and easily scalable method. Tin(IV) oxide nanoparticles (<10 nm) embedded in a reduced graphene oxide matrix (SnO 2 -rGO) were prepared by an in-situ synthetic approach that involves the freeze/freeze-drying of a graphene oxide suspension in the presence of a tin precursor and its subsequent thermal reduction under argon atmosphere. Physicochemical and electrochemical characterization confirmed the optimum nano-structuration of the composite showing ultrafast response at high current densities. Its coupling with a highly porous olive pits waste-derived activated carbon (AC) as the capacitor-type positive electrode, enables the fabrication of a LIC with an excellent energy density output. The newly designed LIC is able to deliver 60 Wh kg −1 at 2.9 kW kg −1 (t discharge  ≈ 1 min) and still 27 Wh kg −1 at 10.6 kW kg −1 (t discharge  ≈ 10 s). [ABSTRACT FROM AUTHOR]

• Carbon aerogels designed at wish with tailored micro and meso porosity. • Balance between micropores and volume of mesopores with the proper diameter needed. • At low current densities, high volume of micropores implies high capacitance. • At high current densities, the mesoporosity is determinant. • LIC assembled using the carbon aerogels is comparable to that using a commercial activated carbon. Nowadays, carbons are reaching high attention in the field of materials science due to their low cost and good availability. However, in most of their potential applications, specific characteristics are required for their good performance. The properties of natural carbon materials sometimes are not easy to modify as they are directly related to their precursor source. Carbon aerogels are promising materials to solve this drawback as their porosity can be easily tailored by selecting suitable initial conditions during the synthesis. Although these materials have been already employed in a wide range of applications, the combination of a well-developed porosity with high electrical conductivity, normally opposite characteristics in carbon materials, makes them suitable candidates for being used in high-power electrochemical devices. In this sense, carbon aerogels might be of interest for a technology such as lithium-ion capacitors, which, despite having reached the market, still require improvements to trigger their expansion. In the present study, carbon aerogels are used as positive electrodes, in which it is observed that micropores are essential to attain high capacitances at low current densities and that the presence of mesopores is a key factor for the stability of the device in the range of medium-high current densities. However, a certain diameter of mesoporous is essential for their effectiveness. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, the benefits and drawbacks of replacing graphite by hard carbon as negative electrode in a lithium-ion capacitor are studied. Beyond the material selection and electrode optimization, the impact of the cell design in the final performance is also evaluated. When selecting hard carbon, final prototype avoids using any critical raw material, since a sacrificial salt (dilithium squarate) has been also used as a pre-lithiation strategy, instead of the most preferred industrial metallic lithium-based solution. The combination of these two strategies shows unique features, enabling the development of a highly sustainable, easy-to-recycle, eco-friendly energy storage solution, towards a more realistic approach. Likewise, this solution offers high versatility and degree of freedom to tune the mass loading, mass balance and operating voltage, enabling custom-made prototypes, offering a large portfolio of products, owing to the electrochemical characteristics of hard carbon. Prototype's internal components design determines final cell performance, which it is directly related to the equilibrium between the most relevant metrics, i.e. , energy, power and cyclability. Thus, smart ad-hoc designs can be developed to cover a wide range of applications and specific needs of different market niches. Full performance analysis for different-in-design monolayer pouch cells that can operate beyond 4.0 V is reported in this work. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work we report for the first time the use of 3-cyanopropionic acid methyl ester (CPAME), with vinylene carbonate (VC) as additive, as an alternative solvent when targeting high voltage lithium ion capacitors (LICs). In view of the promising viscosity, conductivity, and electrochemical stability window, its use in LICs is explored. To this end, a hard carbon (HC) is selected as the negative electrode, while an activated carbon (AC) is the preferred choice as the positive electrode, both being biomass (olive-pits) waste derived. The electrochemical characterization of the HC shows good specific capacities at both low and high current densities (e.g. 322 mAh g−1 at C/10 and 80 mAh g−1 at 10C). In addition, the cyclic voltammogram of the AC reveals a stable electrochemical potential window rising to 4.6 V vs. Li+/Li. This fact allows to develop a LIC operating at 1.5–4.5 V able to deliver high energy and high power density values (i.e. 121 Wh kg−1 AM at 299 W kg−1 AM and 69 Wh kg−1 AM at 2217 W kg−1 AM). Image 1 • 3-cyanopropionic acid methyl ester (CPAME) as an alternative solvent to EC:DMC. • 1M LiPF 6 (CPAME) as new electrolyte for lithium ion capacitor technology. • Fabrication of a lithium ion capacitor operating at cell voltage of 1.5 – 4.5 V. • Fabrication of a lithium ion capacitor delivering 106 Wh kg−1 AM at 2800 W kg−1 AM. • Lithium ion capacitor with 70% capacitance retention after 5000 cycles. [ABSTRACT FROM AUTHOR]