Bingbing Chen

High-voltage and free-standing poly(propylene carbonate)/Li6.75La3Zr1.75Ta0.25O12 composite solid electrolyte for wide temperature range and flexible solid lithium ion battery

Solid electrolyte is regarded as a perfect way to enhance safety issues and boost energy density of lithium batteries. Herein, we developed a type of free-standing poly(propylene carbonate)/Li6.75La3Zr1.75Ta0.25O12 composite solid electrolyte for ambient temperature and flexible solid-state lithium batteries. The composite solid electrolyte exhibited excellent comprehensive performance in terms of high ionic conductivity (5.2 × 10−4 S cm−1) at 20 °C, a wide electrochemical window (4.6 V), high ionic transference number (0.75) and satisfactory mechanical strength (6.8 MPa). When evaluated as solid electrolyte for an ambient-temperature solid lithium battery, such a composite electrolyte delivered excellent rate capability (5C) at 20 °C. This superior performance can be comparable to a liquid electrolyte-soaked PP separator-based lithium battery at room temperature. To our knowledge, this is the best rate capability of a solid composite electrolyte for a solid lithium battery at ambient temperature. Moreover, such a composite electrolyte-based flexible LiFePO4/Li4Ti5O12 lithium ion battery delivered excellent rate capability and superior cycling stability. All these fascinating features make poly(propylene carbonate)/Li6.75La3Zr1.75Ta0.25O12 a very promising all-solid-state electrolyte for flexible solid lithium batteries. Our study makes a big step into addressing the challenges of ambient-temperature solid lithium batteries.

Effects of Boron Addition on Grain Refinement in TiAl-based Alloys

Solid state phase transformation characteristics of the body centred beta(Ti) into the hexagonal closed packed alpha(Ti) in Ti45Al8Nb-(0, 0.3, 0.5 and 0.8 at. pct) B alloys were investigated by heat treatment to clarify gamma/alpha(2) lamellar microstructure refinement induced by B addition. Experimental results confirmed two kinds of boron-reduced grain refinement mechanisms through refining either beta phase then alpha phase (beta-refinement) or alpha phase directly (alpha-refinement) to refine lamellar microstructure at room temperature; however, the role of alpha-refinement dominated the as-cast lamellar microstructure refinement over beta-refinement in Ti45Al8NbxB alloy. It was also found that during the alpha-refinement the convoluted flake- and plate-like borides along beta grain boundaries assisted nucleation of alpha phase, and the particle-like borides near beta grain boundaries impeded alpha phase growth.

Multifunctional Sandwich‐Structured Electrolyte for High‐Performance Lithium–Sulfur Batteries

Abstract Due to its high theoretical energy density (2600 Wh kg−1), low cost, and environmental benignity, the lithium–sulfur (Li‐S) battery is attracting strong interest among the various electrochemical energy storage systems. However, its practical application is seriously hampered by the so‐called shuttle effect of the highly soluble polysulfides. Herein, a novel design of multifunctional sandwich‐structured polymer electrolyte (polymer/cellulose nonwoven/nanocarbon) for high‐performance Li‐S batteries is demonstrated. It is verified that Li‐S battery with this sandwich‐structured polymer electrolyte delivers excellent cycling stability (only 0.039% capacity decay cycle−1 on average exceeding 1500 cycles at 0.5 C) and rate capability (with a reversible capacity of 594 mA h g−1 at 4 C). These electrochemical performances are attributed to the synergistic effect of each layer in this unique sandwich‐structured polymer electrolyte including steady lithium stripping/plating, strong polysulfide absorption ability, and increased redox reaction sites. More importantly, even with high sulfur loading of 4.9 mg cm−2, Li‐S battery with this sandwich‐structured polymer electrolyte can deliver high initial areal capacity of 5.1 mA h cm−2. This demonstrated strategy here may open up a new era of designing hierarchical structured polymer electrolytes for high‐performance Li‐S batteries.

CH3NH2 gas induced (110) preferred cesium-containing perovskite films with reduced PbI6 octahedron distortion and enhanced moisture stability

We report here the discovery of a fancy interaction between cesium iodide (CsI) and methylamine (CH3NH2) due to the presence of the hydrogen bond. The formed CsI·xCH3NH2 is a liquid phase, which facilitates the large scale fabrication of highly uniform cesium-containing perovskite films with strong (110) preferred orientation by the CH3NH2 gas healing process. With this method, at most 10% nonpolar Cs cations could fully dope into the crystal lattice and extremely enhance the interaction of the inorganic framework with a more symmetrical PbI6 octahedron, resulting in obvious improvement in moisture stability under continuous illumination.

A Smart Flexible Zinc Battery with Cooling Recovery Ability

Flexible batteries are essential for wearable electronic devices. To meet practical applications, they need to be mechanically robust and stable. However, strong or multiple bending may sever the interfacial contact between electrode and electrolyte, causing capacity fading or even battery failure. Herein we present a new cooling-recovery concept for flexible batteries, which involves a temperature-sensitive sol-gel transition behavior of the thermoreversible polymer hydrogel electrolyte. Once a battery has suffered from strong mechanical stresses, a simple cooling process can refresh the electrode-electrolyte interface. The energy-storage capability can be recovered with a healing efficiency higher than 98 %. It is believed that this study not only offers new valuable insights, but also opens up new perspectives to develop functional wearable devices.

Li–O2 Cell with LiI(3-hydroxypropionitrile)2 as a Redox Mediator: Insight into the Working Mechanism of I– during Charge in Anhydrous Systems

Redox mediators (RMs) have been widely applied to reduce the charge overpotential of nonaqueous lithium-oxygen (Li-O2) batteries. Among the reported RMs, LiI is under hot debate with lots of controversial reports. However, there is a limited understanding of the charge mechanism of I- in anhydrous Li-O2 batteries. Here, we study the chemical reactivity between the oxidized state of I- and Li2O2. We confirm that the Li2O2 particles could be chemically oxidized by I2 rather than I3- species. Furthermore, our work demonstrates that the generated I- from Li2O2 oxidation would combine with I2 to give I3- species, hindering further oxidation of Li2O2 by I2. To improve the working efficiency of I- RMs, we introduce a compound LiI(3-hydroxypropionitrile)2 (LiI(HPN)2) with a high binding ability of I-. Compared with LiI, the cell that contained LiI(HPN)2 shows a significantly increased amount of I2 species during charge and enhanced Li2O2 oxidation efficiency under the same working conditions.

Graphene boosted Cu2GeS3 for advanced lithium-ion batteries

Germanium-based materials as the anode for lithium ion batteries (LIBs) have been investigated extensively because of their high theoretical capacities. However, ternary germanium-based sulfides as the anode material for LIBs have been rarely investigated until now. In this work, we successfully synthesized a novel ternary Cu2GeS3 (CGS) incorporated with reduced graphene oxide (CGS@RGO) and measured their lithium storage performance. As a result, the binder-free CGS@RGO anodes deliver excellent stable cycling properties and high rate capabilities. These improved properties can be ascribed to the introduction of RGO, which acts as a buffer to accommodate the large volume change and maintain the structural integrity of the electrode. More importantly, this work opens an opportunity to develop novel Ge-based anodes for high performance LIBs.

Integrated Interface Strategy toward Room Temperature Solid-State Lithium Batteries

Solid-state lithium batteries have drawn wide attention to address the safety issues of power batteries. However, the development of solid-state lithium batteries is substantially limited by the poor electrochemical performances originating from the rigid interface between solid electrodes and solid-state electrolytes. In this work, a composite of poly(vinyl carbonate) and Li10SnP2S12 solid-state electrolyte is fabricated successfully via in situ polymerization to improve the rigid interface issues. The composite electrolyte presents a considerable room temperature conductivity of 0.2 mS cm-1, an electrochemical window exceeding 4.5 V, and a Li+ transport number of 0.6. It is demonstrated that solid-state lithium metal battery of LiFe0.2Mn0.8PO4 (LFMP)/composite electrolyte/Li can deliver a high capacity of 130 mA h g-1 with considerable capacity retention of 88% and Coulombic efficiency of exceeding 99% after 140 cycles at the rate of 0.5 C at room temperature. The superior electrochemical performance can be ascribed to the good compatibility of the composite electrolyte with Li metal and the integrated compatible interface between solid electrodes and the composite electrolyte engineered by in situ polymerization, which leads to a significant interfacial impedance decrease from 1292 to 213 Ω cm2 in solid-state Li-Li symmetrical cells. This work provides vital reference for improving the interface compatibility for room temperature solid-state lithium batteries.

Effect of electrochemical reaction on diffusion-induced stress in hollow spherical lithium-ion battery electrode

During the process of lithium-ion intercalation and de-intercalation, the electrode undergoes huge volumetric change. Diffusion-induced stress (DIS) has been investigated in solid and hollow spherical electrode. In this work, a new coupled model is established in a hollow spherical electrode to analyze the DIS with electrochemical reaction. The result shows that electrochemical reaction has a significant influence on the distribution of DIS, which can make the tensile stress decline and even convert the stress from tension to compression. The tendency to avoid the electrode fracture and failure induced by DIS is thus beneficial. Compared to stress evolution in solid and hollow sphere electrode, electrochemical-induced stress in solid electrode is much smaller than that in hollow electrode. Also, reaction-induced stress will keep increasing with the wall thickness decreases. Finally, a new strategy is put forward to optimize the reaction-induced stress and the electrode thickness, which may ultimately extend the overall battery life.

Dendrite-Free Lithium Deposition via Flexible-Rigid Coupling Composite Network for LiNi0.5Mn1.5O4/Li Metal Batteries

Notorious lithium dendrite causes severe capacity fade and harsh safety issues of lithium metal batteries, which hinder the practical applications of lithium metal electrodes in higher energy rechargeable batteries. Here, a kind of 3D-cross-linked composite network is successfully employed as a flexible-rigid coupling protective layer on a lithium metal electrode. During the plating/stripping process, the composite protective layer would enable uniform distribution of lithium ions in the adjacent regions of the lithium electrode, resulting in a dendrite-free deposition at a current density of 2 mA cm-2 . The LiNi0.5 Mn1.5 O4 -based lithium metal battery presents an excellent cycling stability at a voltage range of 3.5-5.0 V with the induction of 3D-cross-linked composite protective layer. From an industrial field application of view, thin lithium metal electrodes (40 µm, with 4 times excess lithium) can be used in LiNi0.5 Mn1.5 O4 (with industrially significant loading of 18 mg cm-2 and 2.6 mAh cm-2 )-based lithium metal batteries, which reveals a promising opportunity for practical applicability in high energy lithium metal batteries.