Advanced electrical energy storage technology is a game changer for a clean, sustainable, and secure energy future because efficient utilization of newable energy hinges on cost-effect and efficient ...energy storage. Further, the viability of many emerging technologies depends on breakthroughs in energy storage technologies, including electric vehicles (EVs) or hybrid electric vehicles (HEVs) and smart grids. Lithium-ion batteries (LIBs), a great success in the portable electronics sector, are believed also the most promising power sources for emerging technologies such as EVs and smart grids. To date, however, the existing LIBs (with LiCoOx cathode and graphite anode) are still unable to meet the strict requirements for safety, cycling stability, and rate capability. The development of advanced anode materials, which can overcome the shortcomings of graphite anode (such as formation of dendritic lithium during charge and undesirable solid electrolyte interface), is of critical importance to enhancing the cycling stability and operational safety of LIBs. Lithium titanate (Li4Ti5O12) has recently attracted considerable attentions as a potential anode material of LIBs for high power applications due to several outstanding features, including a flat charge/discharge plateaus (around 1.55V vs. Li/Li+) because of the two-phase lithium insertion/extraction mechanism and minimum chance for the formation of SEI and dendritic lithium, dramatically enhance the potential for high rate capability and safety. In addition, there is almost no volume change during the lithium insertion and extraction processes, ensuring a high cycling stability and long operational life. However, the electronic conductivity of Li4Ti5O12 is relatively low, resulting in large polarization lose, more so at higher cycling rates, and poor rate performance. Currently, considerable research efforts have been devoted to improving the performance of Li4Ti5O12 at fast charge/discharge rates, and some important progresses have been made. In this review, we first present a general overview of the structural features, thermodynamic properties, transport properties, and the electrochemical behavior of Li4Ti5O12 under typical battery operating conditions. We then provide a comprehensive review of the recent advancements made in characterization, modification, and applications of Li4Ti5O12 electrodes to LIBs, including nanostructuring, surface coating, morphological optimization, doping, and rational design of composite electrodes. Finally, we highlight the critical challenges facing us today and future perspectives for further development of Li4Ti5O12-based electrodes. It is hoped that this review may provide some useful guidelines for rational design of better electrodes for advanced LIBs.
Developing low‐cost, high‐performance electro‐catalysts is essential for large‐scale application of electrochemical energy devices. In this article, reported are the findings in understanding and ...controlling oxygen defects in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) for significantly enhancing the rate of oxygen evolution reaction (OER) are reported. Utilizing surface‐sensitive characterization techniques and first‐principle calculations, it is found that excessive oxygen vacancies promote OH− affiliation and lower the theoretical energy for the formation of O* on the surface, thus greatly facilitating the OER kinetics. On the other hand, however, oxygen vacancies also increase the energy band gap and lower the O 2p band center of PBSCF, which may hinder OER kinetics. Still, careful tuning of these competing effects has resulted in enhanced OER activity for PBSCF with oxygen defects. This work also demonstrates that oxygen defects generated by different techniques have very different characteristics, resulting in different impacts on the activity of electrodes. In particular, PBSCF nanotubes after electrochemical reduction exhibit outstanding OER activity compared with the recently reported perovskite‐based catalysts.
Oxygen vacancies in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) are found to promote OH‐ affiliation and lower the theoretical energy for the formation of O* on the surface. However, oxygen vacancies also increase the energy band gap and lower the O 2p band center of PBSCF. Careful tuning of these competing effects has resulted in enhanced oxygen evolution reaction activity for PBSCF with oxygen defects.
Reversible protonic ceramic electrochemical cells (R-PCECs) are ideally suited for efficient energy storage and conversion; however, one of the limiting factors to high performance is the poor ...stability and insufficient electrocatalytic activity for oxygen reduction and evolution of the air electrode exposed to the high concentration of steam. Here we report our findings in enhancing the electrochemical activity and durability of a perovskite-type air electrode, Ba
Co
Fe
Nb
O
(BCFN), via a water-promoted surface restructuring process. Under properly-controlled operating conditions, the BCFN electrode is naturally restructured to an Nb-rich BCFN electrode covered with Nb-deficient BCFN nanoparticles. When used as the air electrode for a fuel-electrode-supported R-PCEC, good performances are demonstrated at 650 °C, achieving a peak power density of 1.70 W cm
in the fuel cell mode and a current density of 2.8 A cm
at 1.3 V in the electrolysis mode while maintaining reasonable Faradaic efficiencies and promising durability.
Abstract
Developing highly efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is critical for many energy devices. While regulating the proton-coupled electron transfer ...(PCET) process via introducing additive into the system has been reported effective in promoting OER activity, controlling the PCET process by tuning the intrinsic material properties remains a challenging task. In this work, we take double perovskite oxide PrBa
0.5
Sr
0.5
Co
1.5
Fe
0.5
O
5+δ
(PBSCF) as a model system to demonstrate enhancing OER activity through the promotion of PCET by tuning the crystal orientation and correlated proton diffusion. OER kinetics on PBSCF thin films with (100), (110), and (111) orientation, deposited on single crystal LaAlO
3
substrates, were investigated using electrochemical measurements, density functional theory (DFT) calculations, and synchrotron-based near ambient X-ray photoelectron spectroscopy. The results clearly show that the OER activity and the ease of deprotonation depend on orientation and follow the order of (100) > (110) > (111). Correlated with OER activity, proton diffusion is found to be the fastest in the (100) film, followed by (110) and (111) films. Our results point out a way of boosting PCET and OER activity, which can also be successfully applied to a wide range of crucial applications in green energy and environment.
The development of high-performance supercapacitors (SCs) often faces some contradictory and competing requirements such as excellent rate capability, long cycling life, and high energy density. One ...effective strategy is to explore electrode materials of high capacitance, electrode architectures of fast charge and mass transfer, and electrolytes of wide voltage window. Here we report a facile and readily scalable strategy to produce high-performance N-doped graphene with a high specific capacitance (∼390 F g−1). A symmetric SC device with a wide voltage window of 3.5 V is also successfully fabricated based on the N-doped graphene electrode. More importantly, the as-assembled symmetric SC delivers a high energy density of 55 Wh kg−1 at a power density of 1800 W kg−1 while maintaining superior cycling life (retaining 96.6% of the initial capacitance after 20,000 cycles). Even at a power density as high as 8800 W kg−1, it still retains an energy density of 29 Wh kg−1, higher than those of previously reported graphene-based symmetric SCs.
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•N-doped graphene with 3D porous architecture was successfully prepared.•The electrode delivered high specific capacitance and excellent cycling stability.•The symmetrical supercapacitor achieved a remarkable energy and power density.
Over the past decade, wood‐derived materials have attracted enormous interest for both fundamental research and practical applications in various functional devices. In addition to being renewable, ...environmentally benign, naturally abundant, and biodegradable, wood‐derived materials have several unique advantages, including hierarchically porous structures, excellent mechanical flexibility and integrity, and tunable multifunctionality, making them ideally suited for efficient energy storage and conversion. In this article, the latest advances in the development of wood‐derived materials are discussed for electrochemical energy storage systems and devices (e.g., supercapacitors and rechargeable batteries), highlighting their micro/nanostructures, strategies for tailoring the structures and morphologies, as well as their impact on electrochemical performance (energy and power density and long‐term durability). Furthermore, the scientific and technical challenges, together with new directions of future research in this exciting field, are also outlined for electrochemical energy storage applications.
Recent progress in the development of wood and its derivative materials for advanced energy storage devices, including supercapacitors and rechargeable batteries, is reviewed, in particular for their micro/nanostructure, structure engineering strategies, and electrochemical performance.
Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique ...nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoO x ) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoO x /NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon–graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.
Rechargeable metal-air batteries and water splitting are highly competitive options for a sustainable energy future, but their commercialization is hindered by the absence of cost-effective, highly ...efficient and stable catalysts for the oxygen evolution reaction. Here we report the rational design and synthesis of a double perovskite PrBa
Sr
Co
Fe
O
nanofiber as a highly efficient and robust catalyst for the oxygen evolution reaction. Co-doping of strontium and iron into PrBaCo
O
is found to be very effective in enhancing intrinsic activity (normalized by the geometrical surface area, ∼4.7 times), as validated by electrochemical measurements and first-principles calculations. Further, the nanofiber morphology enhances its mass activity remarkably (by ∼20 times) as the diameter is reduced to ∼20 nm, attributed to the increased surface area and an unexpected intrinsic activity enhancement due possibly to a favourable e
electron filling associated with partial surface reduction, as unravelled from chemical titration and electron energy-loss spectroscopy.
Mixed transition metal oxides with hierarchical, porous structures, constructed from interconnected nano-building blocks, are considered promising positive electrodes for high-performance hybrid ...supercapacitors. Here we report our findings in design, fabrication, and characterization of 3D hierarchical, porous quaternary zinc-nickel-aluminum-cobalt oxide (ZNACO) architectures assembled from well-aligned nanosheets grown directly on nickel foam using a facile and scalable chemical bath deposition process followed by calcination. When tested as a binder-free electrode in a 3-electrode configuration, the ZNACO display high specific capacity (839.2Cg−1 at 1Ag−1) and outstanding rate capability (~82% capacity retention from 1Ag−1 to 20Ag−1), superior to those of binary-component NiCo2O4 and ZnCo2O4 as well as single-component Co3O4 electrode. More remarkably, a hybrid supercapacitor consisting of an as-fabricated ZNACO positive electrode and an activated carbon negative electrode exhibits a high energy density of 72.4Whkg−1 at a power density of 533Wkg−1 while maintaining excellent cycling stability (~90% capacitance retention after 10,000 cycles at 10Ag−1), demonstrating a promising potential for development of high-performance hybrid supercapacitors. Further, the unique electrode architecture is also applicable to other electrochemical systems such as batteries, fuel cells, and membrane reactors.
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•3D hierarchical porous Zn-Ni-Al-Co oxide (ZNACO) nanosheets grown directly on Ni foam is constructed for the first time.•The resultant binder-free electrodes manifest outstanding electrochemical performances with high capacity, excellent rate capability and cycling stability.•The synergetic contribution and advantageously structural features contribute to outstanding capacitive performance.•The assembled ZNACO//AC hybrid supercapacitor achieved a remarkable energy density of 72.4Whkg−1 at a power density of 533Wkg−1.
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