High-performance Lithium-ion Capacitors Research Articles

Effects of carbon black on the electrochemical performances of SiOx anode for lithium-ion capacitors

Lithium-ion capacitor (LIC) is a power-type energy storage device, possessing the advantages of high energy density, high power density, long cycle life and wide working temperature range. Silicon-based anode materials for LICs have ultrahigh theoretical specific capacities, about 5–10 times higher than traditional graphite anode. However, since silicon-based materials are semiconductors and the electrical conductivity is limited, the imbalance in reaction kinetics between the rapid non-Faradaic capacitive cathode and sluggish Faradaic redox anode is one of the main barrier to high-performance LICs. In this work, the effects of carbon conductive additive on the electrochemical performances of SiOx anode have been studied. Carbon black (CB, Super C45) shows good electrical conductivity and moderate initial coulombic efficiency, suitable for the conductive additive of SiOx anode. Due to the conducting network and the buffer space for volume expansion/contraction during lithiation/de-lithiation, the combination of CB and SiOx particles play a synergetic effect on improving rate capability and cycling stability of SiOx anode. The reversible specific capacity of SiOx anode containing 30 wt% CB can reach 1549 mAh g−1 in the voltage range of 0.01–2.0 V. It remains no capacity decay after 500 cycles in the shallow voltage range of 0.1–0.6 V, indicating that SiOx is a very promising anode material for LICs.

Realizing high-performance and low-cost lithium-ion capacitor by regulating kinetic matching between ternary nickel cobalt phosphate microspheres anode with ultralong-life and super-rate performance and watermelon peel biomass-derived carbon cathode

Lithium-ion capacitors (LICs) are emerging as one of the most advanced energy storage devices by combining the virtues of both supercapacitors (SCs) and lithium-ion batteries (LIBs). However, the kinetic and capacity mismatch between anode and cathode is the main obstacle to wide applications of LICs. Therefore, the effective strategy of constructing a high-performance LIC is to improve the rate and cycle performance of the anode and the specific capacity of the cathode. Herein, the nickel cobalt phosphate (NiCoP) microspheres anode is demonstrated with robust structural integrity, high electrical conductivity, and fast kinetic feature. Simultaneously, the watermelon-peel biomass-derived carbon (WPBC) cathode is demonstrated a sustainable synthesis strategy with high specific capacity. As expected, the NiCoP exhibits high specific capacities (567 mAh g−1 at 0.1 A g−1), superior rate performance (300 mAh g−1 at 1A g−1), and excellent cycle stability (58 mAh g−1 at 5 A g−1 after 15,000 cycles). The WPBC possesses a high specific surface area (SSA) of 3303.6 m2 g−1 and a high specific capacity of 226 mAh g−1 at 0.1 A g−1. Encouragingly, the NiCoP//WPBC-6 LIC device can deliver high energy density (ED) of 127.4 ± 3.3 and 67 ± 3.8Wh kg−1 at power density (PD) of 190 and 18240 W kg−1 (76.4% capacity retention after 7000 cycles), respectively.

Spiral Graphene Coupling Hierarchically Porous Carbon Advances Dual-Carbon Lithium Ion Capacitor

For the first time, novel spiral graphene (SGs), which are fabricated by an ultra-facile and robust catalytic graphitization strategy, are reported as a promising negative electrode material for lithium ion capacitors (LICs). The unique spiral graphene features a special helical structure, high graphitization and porous framework, resulting in high plateau capacity (222 mAh g−1 below 0.2 V at 0.05 A g−1) and outstanding rate capability (59 mAh g−1 at 5 A g−1). The formation mechanism of SGs is proposed by understanding the precipitation behaviour of carbon and moving trail of catalyst. The hierarchically porous carbon (HPC) derived from same source is also prepared and shows N, O co-doping property, large surface area of 1878 m2 g−1, high total pore volume of 2.11 cm3 g−1 with 86% of mesopores, making it an ideal capacitive material. More remarkably, by virtue of structural advantages, the optimized SG//HPC LICs with a mass loading of ~2.5 mg cm−2 for positive side deliver a high-energy density of 57 Wh kg−1 at a high-power density of 6323 W kg−1 and long-term cyclic stability (89.1% after 10000 cycles at 5 A g−1) in 2.0~4.2 V, outperforming advanced dual-carbon and non-dual-carbon LICs. The current work advances the design and fabrication of electrode materials for high-performance lithium ion capacitors and other energy storage devices.

A hierarchical Ti2Nb10O29 composite electrode for high-power lithium-ion batteries and capacitors

Ti2Nb10O29 (TNO) is a suitable electrode for high-performance lithium-ion batteries and capacitors because of its large lithium storage capacity and high Li+ diffusivity. Currently, the rate or power capability of TNO-based systems is limited by the poor electronic conductivity of the material. Here we report our findings in design, synthesis, and characterization of a hierarchical N-rich carbon conductive layer wrapped TNO structure (TNO@NC) using a novel polypyrrole-chemical vapor deposition (PPy-CVD) process. It was found that carbon coating with PPy–carbon partially reduces Ti and Nb cations, forms TiN, and creates oxygen vacancies in the TNO@NC structure that further increase overall electronic and ionic conductivity. Various defect models and density functional theory (DFT) calculations are used to show how oxygen vacancies influence the electronic structure and Li-ion diffusion energy of the TNO@NC composite. The optimized TNO@NC sample shows notable rate capability in half-cells with a reversible capacity of 300 mAh g−1 at 1 C rate and maintains 211 mAh g−1 at a rate of 100 C, which is superior to that of most MxNbyOz materials. Full cell LiNi0.5Mn1.5O4 (LNMO)||TNO@NC lithium-ion batteries (LIB) and active carbon (AC)||TNO@NC hybrid lithium-ion capacitors (LIC) exhibited notable volumetric and gravimetric energy and power densities.

Fe2TiO5 nanochains as anode for high-performance lithium-ion capacitor

The unique crystal structure and multiple redox couples of iron titanate (Fe2TiO5) provide it a high theoretical capacity and good cycling stability when used as an electrode. In this study, the electrospinning method is employed to synthesize one-dimensional (1D) Fe2TiO5 nanochains. The as-prepared Fe2TiO5 nanochains exhibited superior specific capacity (500 mAh·g−1 at 0.10 A·g−1), excellent rate performance (180 mAh·g−1 at 5.00 A·g−1), and good cycling stability (retaining 100% of the initial specific capacity at a current density of 1.00 A·g−1 after 1000 cycles). The as-assembled Fe2TiO5/SCCB lithium-ion capacitor (LIC) also delivered a competitive energy density (137.8 Wh·kg−1) and power density (11,250 W·kg−1). This study proves that the as-fabricated 1D Fe2TiO5 nanochains are promising anode materials for high-performance LICs.

Co3O4 porous nanorod/N-doped reduced graphene oxide composite with fast pseudocapacitive lithium storage for high-performance lithium-ion capacitors

Co3O4 porous nanorod/N-doped reduced graphene oxide composite with fast pseudocapacitive lithium storage for high-performance lithium-ion capacitors

Study on LiPO3@HC composite anodes with high capacity and rate capability for lithium ion capacitors

Lithium-ion capacitors (LICs) could satisfy the increasing energy demand in current society owning to their high energy density and power density, as well as long cycle property. However, it is still a sharp challenge to find the ideal anode materials with low Li+ de-intercalation potential and fast electrochemical kinetics. Among common electrode materials, hard carbon (HC) is the preferred anode material for LICs, but the unsatisfying capacity and low Initial Coulomb Efficiency (ICE) hinder its practical application. One of the main limiting factors is the poor electrical conductivity. In this paper, lithium metaphosphate (LPO) is coated on the surface of HC by a solid-phase method to improve electrical conductivity as well as capacity. 3wt% LPO coated HC delivers an impressive reversible capacity of 515.3 mAh g−1 at 0.1 C and outstanding rate performance (120.6 mAh g−1 at 10 C). The pre-lithiation technology is adopted to enhance ICE. As a result, ICE can increase from 67.6% to 96.7% after prelithiation. Furthermore, LIC with pre-lithiated 3% LPO@HC anode and active carbon (AC) cathode demonstrates an energy density of 17.8 Wh kg−1 and a power density of 3.8 kW kg−1. The capacitance retention rate is 80.9% after 1000 cycles at 2 C, revealing a promising potential way for high-performance lithium ion capacitors.

Revealing dual capacitive mechanism of carbon cathode toward ultrafast quasi-solid-state lithium ion capacitors

The appropriate pore size and C=O group are vital factors for improving absorption/desorption process of PF 6 − ions, greatly boosting electrochemical performances of carbon cathode and quasi-solid-state lithium ion capacitor. High-performance lithium ion capacitors (LICs) have been seriously hindered by the very low capacity and unclear capacitive mechanism of carbon cathode. Herein, after the combination of experimental results and theoretical calculations, it is found that the critical pore size of 0.8 nm for PF 6 − ion adsorption decreases strong interactive repulsion of electrons and largely reduces adsorption energy barrier, which greatly improves the charge accommodation capacity in electrical double-layer behavior. Most importantly, the chemical-bond evolution process of C=O group has been firstly revealed by X-ray photoelectron spectroscopy (XPS), indicating that the introduction of C=O group can provide abundant redox active sites for PF 6 − ion adsorption accompanied with enhanced pseudocapacitive capacity. Attributed to the synergistic effect of dual capacitive mechanism, porous carbon sheet (PCS) cathode shows a reversible specific capacity of 53.6 mAh g −1 even at a high current density of 50 A g −1 . Significantly, the quasi-solid-state LIC manifests state-of-the-art electrochemical performances with an integrated maximum energy density of 163 Wh kg −1 and an outstanding power density of 15,000 W kg −1 . This elaborate work promotes better fundamental understanding about capacitive mechanism of PF 6 − ion and offers a rational dual-capacitive strategy for the design of advanced carbon cathodes.

S, O dual-doped porous carbon derived from activation of waste papers as electrodes for high performance lithium ion capacitors.

To circumvent the imbalances of electrochemical kinetics and charge-storage capacity between Li+ ion battery anodes and capacitive cathodes in lithium-ion capacitors (LICs), dual carbon based LICs are constructed and investigated extensively. Herein, S, O dual-doped 3D net-like porous carbon (S-NPC) is prepared using waste paper as the carbon source through a facile solvothermal treatment and chemical activation. Benefiting from the combination effect of the rich S,O-doping (about 2.1 at% for S, and 9.0 at% for O), high surface area (2262 m2 g−1) and interconnected porous network structure, the S-NPC-40 material exhibits excellent electrochemical performance as both cathode material and anode material for LICs. S, O doping not only increases the pseudocapacity but also improves the electronic conductivity, which is beneficial to reduce the mismatch between the two electrodes. The S-NPC-40//S-NPC-40 LIC delivers high energy densities of 176.1 and 77.8 W h kg−1 at power densities of 400 and 20 kW kg−1, respectively, as well as superior cycling stability with 82% capacitance retention after 20 000 cycles at 2 A g−1. This research provides an efficient method to convert waste paper to porous carbon electrode materials for high performance LIC devices.

The preparation of three-dimensional binder-free polyaniline/aligned carbon nanotube on flexible etched Al foil substrate as high-performance pseudocapacitive cathode for nonaqueous lithium-ion capacitor

In this work, 3D binder-free polyaniline (PANI)/aligned carbon nanotube (ACNT) nanocomposite arrays on flexible etched Al foil with strong bonding strength is developed as a high-capacity pseudocapacitive cathode material in a non-aqueous electrolyte for lithium ion capacitors (LICs). The optimized PANI/ACNT nanocomposite with a rational 3D pore structure facilitates the ion transportation and fully utilizes the synergistic effect between PANI and ACNTs to improve capacitive performance substantially. The as-prepared nanoscale PANI demonstrates a specific capacity of 325.2 F•g−1 (180.7 mAh•g−1) at 0.5 A•g−1 in the non-aqueous lithium-ion electrolyte and achieves excellent rate performance and cycling stability (retains 95.6% after for 5,000 cycles charge-discharge at 1 A•g−1 in Li-half cell). Furthermore, when matched with a lithium titanate (Li4Ti5O12) anode, the nanoscale PANI delivers a superior specific energy of 295.3 Wh•kg−1 at the specific power of 125.1 W•kg−1. The as-fabricated LIC delivers a specific energy of 49.6 Wh•kg−1 at the specific power of 21.0 W•kg−1 and successfully retains 39.1 Wh•kg−1 at 480.5 W•kg−1. Moreover, the as-fabricated LIC exhibits an excellent capacity retention of 86.8% after 1,000 cycles at 2 A•g−1. The results verify that the as-prepared PANI/ACNTs/etched Al foil is a promising pseudocapacitive cathode material for high-performance LIC application.

Corncob-Derived Hierarchical Porous Activated Carbon for High-Performance Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are hybrid energy storage devices with a capacitor-type cathode and battery-type anode, which bridge the gap between conventional high-energy lithium-ion batteries and...

Prelithiated C-Si/SiO x Based Negative Electrode for High Power and High Energy Density Lithium-Ion Capacitors

A high-performance lithium ion capacitor (LIC) was developed with activated carbon as the positive electrode and pre-lithiated C-coated Si/SiO x nanospheres as the negative electrode for high-power and high-energy density energy storage system. The feasibility of pre-lithiated C-coated Si/SiO x was thoroughly examined as an advanced negative electrode for LIC by comparing prelithiated C-coated Si/SiO x based LIC with conventional graphite anode based LIC. Under optimized pre-lithiation conditions, the prelithiated C-coated Si/SiO x based LIC showed enhanced rate capability and reversible capacity with highly stable cycle performance at a current density of 10 A g-1 up to 1000 cycles. Such improvements may result from the unique physical and chemical properties of C-coated Si/SiO x . The detailed prelithiation condition and electrochemical behaviors of both active carbon and C-coated Si/SiO x in LIC system will be discussed in the presentation.

Synthesis of AlCl3-Graphite Intercalation Compounds for Lithium-Ion Capacitor Anode

Lithium-ion capacitors (LIC) are hybrid energy storage devices combining electric double layer capacitors (EDLC) and lithium-ion batteries (LIB). In typical LIC systems, faradaic reaction on anode restricts high power performance because of slow reaction rate than that of non-faradaic reaction on cathode. The conventional graphite anode suffers from low rate capability for LIC and shows low theoretical capacity which is not suitable for high energy density. To achieve high rate performance and high capacity, ferric chloride-graphite intercalation compounds (FeCl3-GICs) are reported as LIB anodes[1]. Intercalated FeCl3 enlarges interlayer spacing of graphite and reacts like following reaction (FeCl3+3Li++3e- ↔ Fe+3LiCl). We focused on aluminum chloride-GICs (AlCl3-GICs), lighter than FeCl3-GICs, as new anode materials for LIB and LIC. AlCl3-GICs have possibility of high rate performance and higher capacity at low potential by following reaction (AlCl3+3Li++3e-↔Al+3LiCl, Al+2.25Li++2.25e-↔Li2.25Al). In this paper, AlCl3-GICs were synthesized and evaluated their material characteristics and electrochemical properties. AlCl3-GICs was synthesized via vapor phase intercalation mehod[2]. First, graphite, AlCl3 and N-chlorosuccinimide as chlorinating agent were mixed under Ar atomosphere. Then, mixed powder was heated under vacuum at various temperatures (115, 135, 150, 200 ℃), forming AlCl3-GICs (named as 115, 135, 150, 200, respectively). Electrochemical properties were evaluated by galvanostatic charge/discharge test at various current densities with assembled Li//AlCl3-GIC cells. As experimental condition, electrolyte was 1M LiPF6 in EC/DEC (1/1 vol.), voltage range was 0.01–3.0 V and current density values were 0.1–2.0 A g-1. Fig. 1 shows XRD patterns of obtained AlCl3-GICs. Peaks derived from GICs were confirmed for all AlCl3-GICs. The different intensity ratio of pristine(002)/GIC(00x) of the AlCl3-GICs synthesized with different heating temperature indicated various intercalated structures. Fig. 2 shows rate performance of the Li//AlCl3-GIC cells. From this result, it was confirmed that AlCl3-GICs could react with Li+ and showed over 70 mAh g-1 even at high current density such as 2.0 A g-1 (over 4 C-rate). The results demonstrated high rate performance of AlCl3-GICs as anode for LIB and LIC. We have considered that the high rate capability can be due to improvement of Li+ diffusibility caused by enlarging interlayer spacings and/or increase of active surface area. Especially, 115 shows the discharge capacity of 432 mAh g-1, which is higher than theoretical capacity of graphite (372 mAh g-1) and the highest capacities among GICs at all current densities. Therefore, AlCl3-GICs have possibility as the anode for high performance LIC. In the poster, details of characteristics and application to LIC will be discussed. Acknowledgements This work is partially supported by the Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency (JST-ALCA, JPMJAL1008, JPMJAL1301). Reference [1] Y. Sun et al., Energy Technol., 7, 1801091 (2019).[2] H. Shioyama, Tanso, 161, 35-37 (1993). Figure 1

The Full-Cell Design of a Li-Ion Capacitor Using a Sn-Ni Alloy As an Anode

Lithium-ion capacitors (LIC) is composed of a capacitors-type cathode and battery-type anode. Thus, LIC has been considered as a favorable electrochemical energy storage device to bridge the lithium-ion batteries (LIB) and supercapacitors.1 We have reported that the synthesis of Sn-Ni alloy by electrodeposition in aqueous solution and its electrochemical behaviors as an anode for LIB and LIC.2,3 Through the above reports, we confirmed that the LIC consisting of Sn-Ni anode shows higher energy and power density than graphite anode based LIC because of high theoretical capacity of Sn (997 mAh g-1). Herein, the material characterization of Sn-Ni alloy was carried out. Besides, full-cell performances of LIC were tested and compared depending on with/without cell optimization.The Sn-Ni alloy is synthesized by electrodeposition using aqueous electrolyte consisting of Tin(II) chloride dihydrate and Nickel(II) chloride. The material characteristics of Sn-Ni alloy were examined by field emission scanning electron microscopy, X-ray diffraction, glow discharge optical emission spectroscopy, and inductively coupled plasma analysis. The electrochemical performances of Sn-Ni anode and LIC full-cell were tested using alf- and full-cell.The Sn-Ni alloy synthesized by electrodeposition has Ni3Sn4 phase which affects the reversible reaction of Sn-Ni alloy as an anode during lithiation/de-lithiation.2 For that reason, Sn-Ni alloy shows a good discharge performance as an anode for LIC (Fig. 1(a)). The in-depth chemical properties of Sn-Ni alloy was examined by GDOES (Fig. 1(b)). The region from the surface to around 6.9 μm shows that the Sn and Ni are mixed. After that, Cu peak corresponding to the Cu substrate was increased, resulting in an intermediate layer consisting of Sn, Ni, and Cu. The Cu signal after 29.4 μm is relatively higher than Sn and Ni, implying that only Cu substrate was presented. This result indicates that the Sn and Ni are mixed from top of Sn-Ni alloy to middle of film with a thickness of approximately 29. 4 μm.Full-cell optimization of LIC was conducted by mass balancing between cathode and anode. It was confirmed that LIC with cell optimization shows improved energy density and power density compared to LIC without cell optimization. Also, LIC consisting of Sn-Ni anode have higher energy and power density than LIC assembled using graphite anode (Fig.1 (c)). Through the above discussion, we believe that this report provides a blueprint for high-performance LIC with Sn-Ni alloy anode.(Figure 1)Fig. 1 (a) XRD patterns, (b) GDOES curves of Sn-Ni alloy, and (c) Ragone plot of LIC. Acknowledgement This work is partially supported by Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency (JST-ALCA, JPMJAL1008).

Non-corrosive and low-cost synthesis of hierarchically porous carbon frameworks for high-performance lithium-ion capacitors

Because of their capability of rapid lithium uptake/release and robust capacitive energy storage, hierarchically porous carbon frameworks are widely regarded as promising electrode materials for lithium-ion capacitors. The current technologies for their syntheses involve either a heavily corrosive KOH activation or harsh template-removing processes exerting heavy environmental burdens. To surmount these drawbacks, we, herein, report the production of such an architecture by simply carbonizing petroleum asphalt with KHCO3 contributing to hierarchically porous frameworks with high specific surface area in a non-corrosive condition. The microporous carbon nanosheets are curved to give mesopores and interconnected for macropores. Because of these structural merits, the rate-capable lithium storage is realized and the capacitive performance is three-times higher than that of widely used activated carbon cathodes. Furthermore, the lithium-ion capacitors simultaneously using these materials as the anode and cathode can deliver a high energy density of 112 Wh kg-1 at a power density of 260 W kg− and present an energy density of 48 Wh kg−1 at a high-power density of 52 kW kg-1. The versatile capabilities provided by the mild and low-cost carbon materials may find an alternative strategy for the real application of lithium-ion capacitors and other hybrid devices.

Ultrathin porous graphitic carbon nanosheets activated by alkali metal salts for high power density lithium-ion capacitors

Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors (LICs). In this work, onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering, and the effects of alkali metal salts on the structure, morphology and performance of the samples are focused. The results show that alkali metal salts as activator can etch graphitic carbons, and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt. Moreover, it also affects the graphitization degree of the materials. The porous graphitic carbons (S-GCs) obtained by NaCl activation exhibit high specific surface area (77.14 m2·g−1) and appropriate graphitization degree. It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy. High-performance LICs (S-GCs//AC LICs) are achieved with high energy density of 92 Wh·kg−1 and superior rate capability (66.3 Wh·kg−1 at 10 A·g−1) together with the power density as high as 10020.2 W·kg−1.

Iron oxide encapsulated in nitrogen-rich carbon enabling high-performance lithium-ion capacitor

Lithium-ion capacitors (LICs) could combine the virtues of high power capability of conventional super-3capacitors and high energy density of lithium-ion batteries. However, the lack of high-performance electrode materials and the kinetic imbalance between the positive and negative electrodes are the major challenge. In this study, Fe3O4 nanoparticles encapsulated in nitrogen-rich carbon (Fe3O4@NC) were prepared through a self-assembly of the colloidal FeOOH with polyaniline (PANI) followed by pyrolysis. Due to the well-designed nanostructure, conductive nitrogen-rich carbon shells, abundant micropores and high specific surface area, Fe3O4@NC-700 delivers a high capacity, high rate capability and long cycling stability. Kinetic analyses of the redox reactions reveal the pseudocapacitive mechanism and the feasibility as negative material in LIC devices. A novel LIC was constructed with Fe3O4@NC-700 as the negative electrode and expanded graphene (EGN) as the positive electrode. The well-matched two electrodes effectively alleviate the kinetic imbalance between the positive and negative electrodes. As a result, Fe3O4@NC-700//EGN LIC exhibits a wide operating voltage window, and thus achieves an ultrahigh energy density of 137.5 W h kg−1. These results provide fundamental insights into the design of pseudocapacitive electrode and show future research directions towards the next generation energy storage devices.

Multi-dimensional hybrid heterostructure MoS2@C nanocomposite as a highly reversible anode for high-energy lithium-ion capacitors

Lithium-ion capacitors (LICs) are a new generation of hybrid energy storage devices, and there is room for improvement in power characteristic, energy density and cycling life. This paper proposes a facile and high-efficiency strategy for the preparation of high-performance MoS2 based anodes, here we have successfully synthesized a multi-dimensional hybrid heterogeneous composite material (MoS2@C) in which nanoparticles, nanoflakes and hollow nanospheres coexist. The strong adhesion of the Mo-O-C bond formed between MoS2 and carbon ensures favorable structural integrity, while the architecture made of nanoflakes reduces the diffusion distance of Li+. In addition, the voids of the hollow structure can alleviate the volume change during repeated Li+ intercalation/de-intercalation processes and ensure good contact between the material and the electrolyte solution. Moreover, due to the confinement effect of the hollow structure and carbon and the introduction of oxygen vacancies, excellent rate performance is achieved. Given this, in a wide potential window of 0–4.5 V, the MoS2@C//AC device has the highest energy density (189.68 Wh kg−1), the maximum power density (11.25 kW kg−1), subordinate self-discharge rate and long lifespan. Therefore, this research work provides some important ideas and insights for the rational design of MoS2-based high-performance LICs anode materials.

3D porous Li3VO4@C composite anodes with ultra-high rate capacity for lithium-ion capacitors

Lithium ion capacitors have attracted enormous interest in recent years due to their high energy density, high power density as well as long cycle stability. However, it remains as a grand challenge to find a suitable battery-type anode material with low Li-ion insertion potential and fast electrochemical kinetics. In this work, we demonstrate that the 3D porous Li3VO4@C composites synthesized by a facile freeze-drying-assisted thermal treatment method can be favorably used for high-performance lithium ion capacitors. Benefiting from the uniformly distributed Li3VO4 nanoparticles and interconnected conductive carbon networks, the 3D porous Li3VO4@C anode displays a fast kinetics for both charge-transfer and ion-diffusion, excellent rate capability (317 mAh/g even at a high rate of 10 A/g) and superior cycling stability (322 mAh/g at 5A/g after 2000 cycles). A lithium ion capacitor based on these 3D porous Li3VO4@C composites delivers high energy/power densities (129.7 Wh/kg at 251.8 W/kg, 52.8 Wh/kg even at 15.2 kW/kg), revealing the promising potential applications in high-performance and long life Lithium ion capacitors.

Dendrite-structured FeF2 consisting of closely linked nanoparticles as cathode for high-performance lithium-ion capacitors

Abstract Lithium-ion capacitors (LICs) are regarded as a good choice for next-generation energy storage devices, which are expected to exhibit high energy densities, high power densities, and ultra-long cycling stability. Nevertheless, only a few battery-type cathode materials with limited kinetic properties can be employed in LICs, and their electrochemical properties need to be optimized urgently. Here, we exploit a new dendrite-structured FeF2 consisting of closely linked primary nanoparticles using a facile solvothermal method combined with the subsequent annealing treatment. This particular architecture has favorable transport pathways for both lithium ions and electrons and exhibits an ultrafast charge-discharge capability with high reversible capacities. Furthermore, a well-designed LIC employing the prepared dendrite-structured FeF2 as the battery-type cathode and commercialized activated carbon (AC) as supercapacitor-type anode was constructed in an organic electrolyte containing Li ions. The LIC operates at an optimal voltage range of 1.1–3.8 V and shows a maximum high energy density of 152 W h kg−1 and a high power density of 4900 W kg−1 based on the total mass of cathode and anode. Long-term cycling stability (85% capacity retention after 2000 cycles) was achieved at 1 A g−1. This work suggests that the dendrite-structured FeF2 is a prime candidate for high-performance LICs and accelerates the development of hybrid ion capacitor devices.