Microphase Separation and High Ionic Conductivity at High Temperatures of Lithium Salt-Doped Amphiphilic Alternating Copolymer Brush with Rigid Side Chains

An amphiphilic alternating copolymer brush (AACPB), poly­{(styrene-<i>g</i>-poly­(ethylene oxide))-<i>alt</i>-(maleimide-<i>g</i>-poly­{2,5-bis­[(4-methoxy­phenyl)­oxycarbonyl]­styrene})}­(P­{(St-<i>g</i>-PEO)-<i>alt</i>-(MI-<i>g</i>-PMPCS)}), was synthesized by alternating copolymerization of styrene-terminated poly­(ethylene oxide) (St-PEO) and maleimide-terminated poly­{2,5-bis­[(4-methoxy­phenyl)-oxy­carbonyl]­styrene} (MI-PMPCS) macromonomers using the “grafting through” strategy. ¹H NMR and gel permeation chromatography coupled with multiangle laser light scattering were used to determine the molecular characteristics of AACPBs. Although these AACPBs cannot microphase separate with thermal and solvent annealing methods, they can form lamellar structures by doping a lithium salt. This is a first report on lithium salt-induced microphase separation of AACPBs, and the lithium salt-doped AACPBs can serve as solid electrolytes for the transport of lithium ion. For the same AACPB, the ionic conductivity (σ) increases with increasing doping ratio. In addition, σ values of different AACPBs with the same doping ratio become higher for shorter PMPCS side chains. The σ value of the lithium salt-doped AACPB increases with increasing temperature in the range of 25–240 °C, and σ is 1.79 × 10^–4 S/cm at 240 °C. The relatively high σ values of the lithium-doped AACPBs at high temperatures benefit from the rigid PMPCS side chain and the AACPB architecture. The lithium salt-doped AACPBs have the potential to serve as solid electrolytes in high-temperature lithium ion batteries

Grape-Like Fe₃O₄ Agglomerates Grown on Graphene Nanosheets for Ultrafast and Stable Lithium Storage

An in situ simple and effective synthesis method is effectively exploited to construct MOF-derived grape-like architecture anchoring on nitrogen-doped graphene, in which ultrafine Fe₃O₄ nanoparticles are uniformly dispersed (Fe₃O₄@C/NG). In this hybrid hierarchical structure, new synergistic features are accessed. The graphene oxide plane with functional groups is expected to alleviate the aggregation problem in the MOFs’ growth. Moreover, the morphology and size of iron-based MOFs and carbon content are conveniently controlled by controlling the solution concentration of precursor. Through making use of in situ carbonization of the organic ligands in MOFs, Fe₃O₄ subunits are effectively protected by 3D interconnected conductive carbon at microscale. Consequently, when applied as anode materials, even as high as 10 A g^–1 after 1000 cycles, Fe₃O₄@C/NG still maintains as high as 458 mA h g^–1

High-Performance All-Solid-State Polymer Electrolyte with Controllable Conductivity Pathway Formed by Self-Assembly of Reactive Discogen and Immobilized via a Facile Photopolymerization for a Lithium-Ion Battery

All-solid-state polymer electrolytes (SPEs) have aroused great interests as one of the most promising alternatives for liquid electrolyte in the next-generation high-safety, and flexible lithium-ion batteries. However, some disadvantages of SPEs such as inefficient ion transmission capacity and poor interface stability result in unsatisfactory cyclic performance of the assembled batteries. Especially, the solid cell is hard to be run at room temperature. Herein, a novel and flexible discotic liquid-crystal (DLC)-based cross-linked solid polymer electrolyte (DLCCSPE) with controlled ion-conducting channels is fabricated via a one-pot photopolymerization of oriented reactive discogen, poly­(ethylene glycol)­diacrylate, and lithium salt. The experimental results indicate that the macroscopic alignment of self-assembled columns in the DLCCSPEs is successfully obtained under annealing and effectively immobilized via the UV photopolymerization. Because of the existence of unique oriented structure in the electrolytes, the prepared DLCCSPE films exhibit higher ionic conductivities and better comprehensive electrochemical properties than the DLCCSPEs without controlled ion-conductive pathways. Especially, the assembled LiFePO₄/Li cells with oriented electrolyte show an initial discharge capacity of 164 mA h g^–1 at 0.1 C and average specific discharge capacities of 143, 135, and 149 mA h g^–1 at the C-rates of 0.5, 1, and 0.2 C, respectively. In addition, the solid cell also shows the first discharge capacity of 124 mA h g^–1 (0.2 C) at room temperature. The outstanding cell performance of the oriented DLCCSPE should be originated from the macroscopically oriented and self-assembled DLC, which can form ion-conducting channels. Thus, combining the excellent performance of DLCCSPE and the simple one-pot fabricating process of the DLC-based all-solid-state electrolyte, it is believed that the DLC-based electrolyte can be one of the most promising electrolyte materials for the next-generation high-safety solid lithium-ion batteries

SnO₂@PANI Core–Shell Nanorod Arrays on 3D Graphite Foam: A High-Performance Integrated Electrode for Lithium-Ion Batteries

The rational design and controllable fabrication of electrode materials with tailored structures and superior performance is highly desirable for the next-generation lithium ion batteries (LIBs). In this work, a novel three-dimensional (3D) graphite foam (GF)@SnO₂ nanorod arrays (NRAs)@polyaniline (PANI) hybrid architecture was constructed via solvothermal growth followed by electrochemical deposition. Aligned SnO₂ NRAs were uniformly grown on the surface of GF, and a PANI shell with a thickness of ∼40 nm was coated on individual SnO₂ nanorods, forming a SnO₂@PANI core–shell structure. Benefiting from the synergetic effect of 3D GF with large surface area and high conductivity, SnO₂ NRAs offering direct pathways for electrons and lithium ions, and the conductive PANI shell that accommodates the large volume variation of SnO₂, the binder-free, integrated GF@SnO₂ NRAs@PANI electrode for LIBs exhibited high capacity, excellent rate capability, and good electrochemical stability. A high discharge capacity of 540 mAh g^–1 (calculated by the total mass of the electrode) was achieved after 50 cycles at a current density of 500 mA g^–1. Moreover, the electrode demonstrated superior rate performance with a discharge capacity of 414 mAh g^–1 at a high rate of 3 A g^–1