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Li 2 MSiO 4 (M = Mn, Fe, Co, Ni, et al.) has received great attention because of the theoretical possibility to reversibly deintercalate two Li + ions from the structure. However, the silicates still suffer from low electronic conductivity, sluggish lithium ion diffusion and structural instability upon deep cycling. In order to solve these problems, a “hard-soft” templating method has been developed to synthesize three-dimensionally ordered macroporous (3DOM) Li 2 FeSiO 4 /C composites. The 3DOM Li 2 FeSiO 4 /C composites show a high reversible capacity (239 mAh g −1 ) with ∼1.50 lithium ion insertion/extraction, a capacity retention of nearly 100% after 420 cycles and excellent rate capability. The enhanced electrochemical performance is ascribed to the interconnected carbon framework that improves the electronic conductivity and the 3DOM structure that offers short Li ion diffusion pathways and restrains volumetric changes. [ABSTRACT FROM AUTHOR]

Here, we report a new enhanced extrinsic pseudocapacitve Li-ion storage mechanism via lithiation-induced structural optimization strategy. The flower-like C@SnS and bulk SnS exhibit initial capacity decay and subsequent increase of capacity on cycling. After a long-term lithiation/delithiation process, flower-like C@SnS and bulk SnS exhibit improved rate performance and reversible capacity in comparison with those of initial state. Moreover, a high capacity of 530 mAh g −1 is still remained even after 1550 cycles at a high current density of 5.0 A g −1 for flower-like C@SnS after pre-lithiation of 350 cycles. According to the comprehensive analysis of structural evolution and electrochemical performance, it demonstrates that SnS electrodes experience crystal size reduction and further amorphization on cycling, which enhances the reversibility of conversion reaction for SnS, leading to increasing capacity. On the other hand, surface-dominated extrinsic pseudocapacitive contribution results in enhanced rate performance because electrodes expose a large fraction of Li + sites on surface or near-surface region with structural optimization on cycling. This study reveals that extrinsic pseudocapacitance of SnS can be stimulated via lithiation-induced structural optimization, which gives rise to high-rate and long-lived performances. [ABSTRACT FROM AUTHOR]

Solid polymer electrolyte membranes (SPEMs) with star-shaped structure, consisting of octavinyl octasilsesquioxane (OV-POSS) with nanoscale organic/inorganic hybrid structure and poly(ethylene glycol) methyl ether methacrylate (PEGMEM), have been prepared by one-step free radical polymerization. OV-POSS with eight functional corner groups was used to produce star-shaped nanocomposites and PEGMEM was used as the polymer matrix to dissolve lithium ion. For comparison, SPEMs based on the corresponding linear copolymers, containing POSS moieties and PEGMEM segments, were also prepared. The SPEM with star-shaped structure containing 5.1 mol% POSS exhibits the highest ionic conductivity of 1.13×10 −4 S cm −1 and Li + transference number of 0.35 at 25 °C, which are about two times of that of SPEM with linear structure containing the same POSS content. Moreover, the Li/LiFePO 4 cell assembled with such star-shaped SPEM delivers the highest discharge capacity of 137.1 mAh g −1 under a current density of 0.5 C at 25 °C. At an evaluated temperature of 80 °C, this cell exhibits an initial discharge capacity of 163.8 mAh g −1 at 0.5 C, and even at high discharging C-rates of 5 and 10 C, the discharge capacity of 75.6 and 45.7 mAh g −1 can still be obtained, respectively. [ABSTRACT FROM AUTHOR]

Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO 2 -grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO 2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO 2 -grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10 −4 S cm −1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO 2 -grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g −1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C). [ABSTRACT FROM AUTHOR]

A novel composite electrolyte membrane (CEM), consisting of a viscous PEGMEM-co-SMA copolymer, lithium salt and cellulose matrix, has been prepared as a new class of electrolyte for high performance lithium-ion batteries (LIBs). This CEM exhibits a wide electrochemical stability window (>5 V vs. Li/Li + ), reasonably high ionic conductivity and thermal stability up to 315 °C. At temperature above the melting temperature (31.98–35.71 °C), the viscous flow nature of the copolymer is beneficial to fully infiltrate the electrode materials like liquid electrolyte to maintain uniform contact with electrode surfaces during charge/discharge process. The interfacial resistance ( R intf ) of the fresh cell based on this CEM is extremely low (3.8 Ω cm −2 ) and the Li/LiFePO 4 cell deliveries a discharge capacity as high as 156.9 mA h g −1 with a current density of 1 C at 80 °C. It is anticipated that this work provides a new insight for designing advanced electrolyte materials for LIBs with enhanced interfacial contact and excellent cycling performance. [ABSTRACT FROM AUTHOR]