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Large-radius non-lithium cation doping can increase lithium-ion conductivity at low lithium-ion concentrations while the doping of non-lithium cations with a small radius can improve the lithium-ion conductivity at high lithium-ion concentrations.

Employing the solid polymer electrolyte (SPE) instead of traditional liquid electrolyte is an effective way to develop high safety and high-energy density solid-state lithium batteries. Herein, for the first time, the Ni3B2O3 (NBO) nanorods are incorporated into polyethylene oxide (PEO)-based SPE. Particularly, the optimized NBO-embedded SPE shows a high ionic conductivity of 8.5 × 10−5 S cm−1 at 30 °C, lowering the operating temperature of PEO-based SPE substantially. The corresponding LiFePO4/Li battery demonstrates a high discharge capacity of 154 mAh g−1 after 80 cycles at 0.2 C under 30 °C, with favorable capacity retention of 97.5%. The remarkable properties are attributed to the high ionic conductivity of modified SPE at ambient temperature, which is resulted from the decreased crystallinity and melting transition point, increased movement of PEO chain, and promotion of lithium salt dissociation, as well as the formation of the lithium ion migrating pathway on the interface between PEO and NBO nanorods.

Silicon (Si) is widely considered to be the most attractive candidate anode material for use in next-generation high-energy-density lithium (Li)-ion batteries (LIBs) because it has a high theoretical gravimetric Li storage capacity, relatively low lithiation voltage, and abundant resources. Consequently, massive efforts have been exerted to improve its electrochemical performance. While some progress in this field has been achieved, a number of severe challenges, such as the element’s large volume change during cycling, low intrinsic electronic conductivity, and poor rate capacity, have yet to be solved. Methods to solve these problems have been attempted via the development of nanosized Si materials. Unfortunately, reviews summarizing the work on Si-based alloys are scarce. Herein, the recent progress related to Si-based alloy anode materials is reviewed. The problems associated with Si anodes and the corresponding strategies used to address these problems are first described. Then, the available Si-based alloys are divided into Si/Li-active and inactive systems, and the characteristics of these systems are discussed. Other special systems are also introduced. Finally, perspectives and future outlooks are provided to enable the wider application of Si-alloy anodes to commercial LIBs.

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.

The overcharge behaviors of 1000 mAh LiCoO2/graphite pouch cells are systematically investigated through the analysis of morphology, structural and thermal stability of LiCoO2 under different state of charge (SOC) of 120%, 150%, 174%, 190% and 220%. The LiCoO2 experiences the phase transition from O3 to H1-3 and then O1 together with the grain breakage and boundary slip as evidenced by XRD and SEM analysis respectively, which results in the pronounced Co dissolution after the SOC of 174%. The impedance analysis of the pouch cells and coin cells demonstrates that the main contribution of impedance increase originates from the LiCoO2 electrode. Under the combined effect of structural collapse, Co dissolution, and electrolyte oxidization, the thermal stability of LiCoO2 cathode materials reduces with the progressing of overcharge as revealed by differential scanning calorimetry (DSC) results. We hope that this comprehensive understanding can provide meaningful guidance for advancing the overcharge performance of LiCoO2/graphite pouch cells.

High ionic conductivity, good electrochemical stability, and satisfactory mechanical property are the crucial factors for polymer solid state electrolytes. Herein, fast ion conductor LiAlSiO4 (LASO) is incorporated into polyethylene oxide (PEO)-based solid-state electrolytes (SSEs). The SSEs containing LASO exhibit enhanced mechanical properties performance compared to pristine PEO-LiTFSI electrolyte. A reduced melting transition temperature of 40.57 °C is enabled by introducing LASO in to PEO-based SSE, which is beneficial to the motion of PEO chain and makes it possible for working at a moderate environment. Coupling with the enhanced motion of PEO, dissociation of the lithium salt, and conducting channel of LASO, the optimized composite polymer SSE exhibits a high ionic conductivity of 4.68 × 10−4, 3.16 × 10−4 and 1.62 × 10−4 S cm−1 at 60, 50 and 40 °C, respectively. The corresponding LiFePO4//Li solid-state battery exhibits high specific capacities of 166, 160 and 139 mAh g−1 at 0.2 C under 60, 40 and 25 °C. In addition, it remains 130 mAh g−1 at 4.0 C, and maintains 91.74% after 500 cycles at 1.0 C under 60 °C. This study provides a simple approach for developing ionic conductor-filled polymer electrolytes in solid-state lithium battery application.

The sodium-ion battery is a strong candidate for the large-scale energy storage device due to its low cost and abundant resources. However, the severe self-discharge issue, which is rooted in the dissolution of the solid-electrolyte interphase (SEI) film in the sodium-ion battery, impedes its practical application. Thus, the central question is how to build a stable SEI film onto the electrode surface. Here, we propose and experimentally demonstrate a LiF-rich SEI film at the surface of hard carbon (HC) anode in sodium-ion battery, which is generated by adding lithium difluoro(oxalate)borate (LiODFB) additive into the electrolyte of 1 M NaPF6 in EC:DMC (1:1 in volume ratio). The X-ray photoelectron spectroscopy (XPS) and electron microscopy (SEM and TEM) results confirm that we obtain the LiF-rich SEI film at the HC electrode surface, which grows up with the increasing of the concentration of added LiODFB additive. But it blocks the transmission of Na ions into HC as evidenced by the initial galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) results. Although this work shows a negative result, it denies the possibility of using the lithium compounds with lower solubility as SEI components for Na-ion battery since it allows to transfer the lithium ions rather than the Na ions.

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.

With the proliferation of energy storage and power applications, electric vehicles particularly, solid-state batteries are considered as one of the most promising strategies to address the ever-increasing safety concern and high energy demand of power devices. Here, we demonstrate the Al4B2O9 nanorods-modified poly(ethylene oxide) (PEO)-based solid polymer electrolyte (ASPE) with high ionic conductivity, wide electrochemical window, decent mechanical property and nonflammable performance. Specifically, because of the longer-range ordered Li+ transfer channels conducted by the interaction between Al4B2O9 nanorods and PEO, the optimal ASPE (ASPE-1) shows excellent ionic conductivity of 4.35×10−1 and 3.1×10−1 S cm−1 at 30 and 60°C, respectively. It also has good electrochemical stability at 60°C with a decomposition voltage of 5.1 V. Besides, the assembled LiFePO4//Li cells show good cycling performance, delivering 155 mA h g−1 after 300 cycles at 1 C under 60°C, and present excellent low temperature adaptability, retaining over 125 mA h g−1 after 90 cycles at 0.2 C under 30°C. These results verify that the addition of Al4B2O9 nanorods can effectively promote the integrated performance of solid polymer electrolyte.

Lithium ion capacitors (LICs) have been widely used as energy storage devices due to their high energy density and high power density. For LICs, pre-lithiation of negative electrode is necessary. In this work, we employ a bifunctional Li6CoO4 (LCO) as cathodic pre-lithiation reagent to improve the electrochemical performance of LICs. The synthesized LCO exhibited high first charge specific capacity of 721 mAh g−1 and extremely low initial coulombic efficiency of 3.19%, providing sufficient Li+ for the pre-lithiation of negative electrode in the first charge. Simultaneously, Li6–xCoOy is generated from LCO during the first charge process, which exhibits pseudocapacitive property and contributes to capacity in form of surface capacitance during subsequent cycles, increasing the capacity of capacitive positive electrode. With the appropriate amounts of addition to the positive side in LICs, this bifunctional prelithiation reagent LCO shows significantly improved the electrochemical performance with the energy density of 78.5 Wh kg−1 after 300 cycles between 2.0 and 4.2 V at 250 mA g−1.

Lithium-ion capacitor (LIC) bridging the gap between the lithium ion battery and electrochemical capacitor has attracted myriad interest. Lignin, the second most abundant natural polymer, is also t...

Porous graphitic carbon nanorings (PGCNs) are proposed by smart catalytic graphitization of nano-sized graphene quantum dots (GQDs). The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm, and demonstrate extraordinary mesoporous structure, controllable graphitization degree and highly defective nature. The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process, undergoing the procedure of amorphous carbon, intermediate phase, graphitic carbon nanorings and graphitic carbon nanosheets. Further, the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed. The unique microstructure implies PGCNs a broad prospect for energy storage application. When applied as negative electrode materials in dual-carbon lithium-ion capacitors, high energy density (77.6 Wh·kg−1) and super long lifespan (89.5% retention after 40,000 cycles at 5.0 A·g−1) are obtained. The energy density still maintains at 24.5 Wh·kg−1 even at the power density of 14.1 kW·kg−1, demonstrating excellent rate capability. The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.

Cost-effective bifunctional electrocatalysts with desirable oxygen catalytic activity to both of ORR and OER are essential to the large-scale commercial application of metal-air batteries. In this work, a robust hydrothermal assembly strategy is presented to fabricate the three-dimensional (3D) urchin-like hybrid material of acid-treated multiwall CNTs (MWCNTs) and needle-like NiCo2O4 as a cost-effective bifunctional oxygen electrocatalyst. Benefiting from the particular 3D urchin-like mesoporous structure providing rich transport channels for O2 diffusion and electrolyte infiltration and abundant active sites for charge transfer reaction, and the synergistic effect of high electrocatalytically active NiCo2O4 and high conductive MWCNTs network, the optimized NCO@20%MWCNTs composite exhibits a superior OER and ORR catalytic activity. In its practical application, an ultrahigh initial round-trip efficiency of 79.4% and long-term cycle stability (950 cycles) at 10 mA cm−2 are achieved in Zn-air battery. This simple strategy for construction of the cost-effective unique 3D porous urchin-like structure together with the improved electrochemical catalytic activity provides a great potential for material design in oxygen catalysis and metal-air batteries.

Herein, we report a series of O3-type Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) oxides as sodium-ion battery cathode materials synthesized via spray pyrolysis method. The structure, morphology, and electrochemical performance of Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) are characterized by XRD, SEM, CV, and galvanostatic charge and discharge tests, respectively. Na(Ni1/3Mn1/3Fe1/3)0.95Al0.05O2 delivers an initial discharge capacity of 145.4 mAh g−1 at 0.1 C and exhibits a favorable reversible capacity about 128.4 mAh g−1 after 80 cycles at 0.2 C, with the capacity retention of 77.5% at the voltage range of 2.0 to 4.2 V. XPS analysis reveals that Al-doping could alleviate the Jahn-Teller effect caused by Mn3+ and enhance the structural stability of layered oxides. The results confirm that a small quantity of (5 at. %) Al-doping improves the structural stability of the material, therefore leading to the excellent electrochemical performance.

2D carbon materials show extraordinarily promising prospects in energy storage systems. To improve the performance of lithium-ion capacitors (LICs), it is urgently necessary for addressing the sluggish kinetics behavior of battery-type carbon negative electrode. Herein, novel 2D defective high-graphitic carbon nanosheets (GNS), which is derived from in-situ catalytic graphitization of 1D nanorods precursor, are presented and employed as negative electrode materials in LICs. The effects of defects contained in the as-prepared samples are further explored by the First-principle calculations, revealing that carbonylation and N-doping (particularly pyridine N) manifest synergistic effect on improving the electronic conductivity and regulating the microstructure. The high reversible capacity accompanied with large plateau capacity and superior rate capability in the half-cell test implies that GNS can be a promised candidate as negative electrode for LICs. Excitingly, the fabricated LICs exhibit high energy density of 112 Wh kg−1 and excellent power density of 19,600 W kg−1, together with outstanding energy density retention of 96.5% after 5000 cycles at 5 A g−1. The defects-controlled in-situ catalytic strategy for preparing GNS may provide a brand-new way for materials design for energy storage.