Rechargeable lithium-ion batteries (LIBs) are important electrochemical energy storage devices for consumer electronics and emerging electrical/hybrid vehicles. However, one of the formidable challenges is to develop ultrafast charging LIBs with the rate capability at least one order of magnitude (>10 C) higher than that of the currently commercialized LIBs. This tutorial review presents the state-of-the-art developments in ultrafast charging LIBs by the rational design of materials. First of all, fundamental electrochemistry and related ionic/electronic conduction theories identify that the rate capability of LIBs is kinetically limited by the sluggish solid-state diffusion process in electrode materials. Then, several aspects of the intrinsic materials, materials engineering and processing, and electrode materials architecture design towards maximizing both ionic and electronic conductivity in the electrode with a short diffusion length are deliberated. Finally, the future trends and perspectives for the ultrafast rechargeable LIBs are discussed. Continuous rapid progress in this area is essential and urgent to endow LIBs with ultrafast charging capability to meet huge demands in the near future.

Although some progress has been made on stretchable supercapacitors, traditional stretchable supercapacitors fabricated by predesigning structured electrodes for device assembling still lack the device-level editability and programmability. To adapt to wearable electronics with arbitrary configurations, it is highly desirable to develop editable supercapacitors that can be directly transferred into desirable shapes and stretchability. In this work, editable supercapacitors for customizable shapes and stretchability using electrodes based on mechanically strengthened ultralong MnO nanowire composites are developed. A supercapacitor edited with honeycomb-like structure shows a specific capacitance of 227.2 mF cm and can be stretched up to 500% without degradation of electrochemical performance, which is superior to most of the state-of-the-art stretchable supercapacitors. In addition, it maintains nearly 98% of the initial capacitance after 10 000 stretch-and-release cycles under 400% tensile strain. As a representative of concept for system integration, the editable supercapacitors are integrated with a strain sensor, and the system exhibits a stable sensing performance even under arm swing. Being highly stretchable, easily programmable, as well as connectable in series and parallel, an editable supercapacitor with customizable stretchability is promising to produce stylish energy storage devices to power various portable, stretchable, and wearable devices.

Spinel LiNi Mn O (LNMO) is the most promising cathode material for achieving high energy density lithium-ion batteries attributed to its high operating voltage (≈4.75 V). However, at such high voltage, the commonly used battery electrolyte is suffered from severe oxidation, forming unstable solid-electrolyte interphase (SEI) layers. This would induce capacity fading, self-discharge, as well as inferior rate capabilities for the electrode during cycling. This work first time discovers that the electrolyte oxidation is effectively negated by introducing an electrochemically stable silk sericin protein, which is capable to stabilize the SEI layer and suppress the self-discharge behavior for LNMO. In addition, robust mechanical support of sericin coating maintains the structural integrity during the fast charging/discharging process. Benefited from these merits, the sericin-based LNMO electrode possesses a much lower Li-ion diffusion energy barrier (26.1 kJ mol ) for than that of polyvinylidene fluoride-based LNMO electrode (37.5 kJ mol ), delivering a remarkable high-rate performance. This work heralds a new paradigm for manipulating interfacial chemistry of electrode to solve the key obstacle for LNMO commercialization, opening a powerful avenue for unlocking the current challenges for a wide family of high operating voltage cathode materials (>4.5 V) toward practical applications.

No abstract

Solution-processable inks based on lithium titanate with a conductive network architecture, toward high-rate lithium-ion batteries (LIBs) with a customized configuration are developed. The inks, with tunable viscosity, are compatible for on-demand coating techniques. The lithium titanate electrode derived from these inks exhibits excellent high-rate capacity (≈124 mA h g(-1) at 90 C, 15.7 A g(-1) ) after 1000 cycles.

Fundamental insight into the surface charging mechanism of TiO (B) nanomaterials is limited due to the complicated nature of lithiation behavior, as well as the limitations of available characterization tools that can directly probe surface charging process. Here, an in situ approach is reported to monitor the dynamic valence state of TiO (B) nanotube electrodes, which utilizes in situ X-ray absorption spectroscopy (XAS) to identify the origin and contribution of surface storage. A real-time correlation is elucidated between the rate-dependent electrode performance and dynamic Ti valence-state change. A continuous Ti valence state change is directly observed through the whole charging/discharging process regardless of charging rates, which proves that along with the well-known non-faradaic reaction, the surface charging process also originates from a faradaic reaction. The quantification of these two surface storage contributions at different charging rates is further realized through in situ dynamic valence state monitoring combined with traditional cyclic voltammetry measurement. The methodology reported here can also be applied to other electrode materials for the real-time probing of valence state change during electrochemical reactions, the quantification of the faradaic and non-faradaic reactions, and the eventual elucidation of electrochemical surface charging mechanisms.

Lithium-ion batteries (LIBs), as the most widely used power source for portable electronics and the electric vehicles industry, are expected to exhibit high standards in terms of safety, long lifespan, high energy density, and high power density. However, the commercial graphite anode still suffers from potential safety issues. To address this challenge, TiO 2 -based materials are being widely explored as anode materials and promising progress has been achieved in the past few decades. In this review, we present the stateof-the-art for materials design strategies for TiO 2 materials to achieve high-performance LIBs. First, a brief discussion of the basic requirements for LIBs is introduced as a prerequisite. Second, for the purpose of improving the electrode performance with TiO 2 materials, the corresponding material engineering approaches are illustrated, which include intrinsic methods and extrinsic approaches. Lastly, the challenges and future perspectives for nanostructured TiO 2 toward high-performance LIBs are outlined. This review is expected to give a comprehensive understanding and guidance on TiO 2 -based materials in the application of energy storage devices.

Lithium-ion batteries (LIBs) are primary energy storage devices to power consumer electronics and electric vehicles, but their capacity is dramatically decreased at ultrahigh charging/discharging rates. This mainly originates from a high Li-ion/electron transport barrier within a traditional electrode, resulting in reaction polarization issues. To address this limitation, a functionally layer-graded electrode was designed and fabricated to decrease the charge carrier transport barrier within the electrode. As a proof-of-concept, functionally layer-graded electrodes composing of TiO (B) and reduced graphene oxide (RGO) exhibit a remarkable capacity of 128 mAh g at a high charging/discharging rate of 20 C (6.7 A g ), which is much higher than that of a traditionally homogeneous electrode (74 mAh g ) with the same composition. This is evidenced by the improvement of effective Li ion diffusivity as well as electronic conductivity in the functionally layer-graded electrodes.