Polymeric binder is extremely important for Si-based anode in lithium-ion batteries due to large volume variation during charging/discharging process. Here, natural rubber-incorporated chitosan networks were designed as a binder material to obtain both adhesion and elasticity. Chitosan could strongly anchor Si particles through hydrogen bonding, while the natural rubber could stretch reversibly during the volume variation of Si particles, resulting in high cyclic performance. The prepared electrode exhibited the specific capacities of 1350 mAh/g after 1600 cycles at the current density of 8 A/g and 2310 mAh/g after 500 cycles at the current density of 1 A/g. Furthermore, the cycle test with limiting lithiation capacity was conducted to study the optimal binder properties at varying degree of the volume expansion of silicon, and it was found that the elastic property of binder material was strongly required when the large volume expansion of Si occurred.

3505wileyonlinelibrary.com dielectric capacitors possess higher power density, faster charge-discharge capability, and longer lifetime, [ 3,4 ] but bear energy densities that are one order of magnitude lower than those of batteries. [ 5 ] As the energy density of capacitors is governed by the dielectric materials that separate the opposite static charges between two electrodes, the development of dielectric materials with greatly improved energy density is thus becoming one of the major enabling technologies. [ 6 ] In general, the energy density ( U e ) of linear dielectric materials is given by U e = ½ ε r ε 0 E 2 , where ε r is the effective permittivity, ε 0 is the vacuum permittivity, and E is the applied fi eld. Inorganic dielectric materials, while enjoying high dielectric permittivities, are limited by low breakdown strength ( E b ), i.e., typically in the scale of kV m ), and graceful failure mechanism, although their permittivities are orders of magnitude smaller than those of their inorganic counterparts. [ 7,8 ] To integrate the complementary advantages of inorganic and organic dielectric materials, polymer nanocomposites composed of inorganic ceramic fi llers with high dielectric constant ( k ) have been prepared by using a variety of methods, including mechanical blending, [ 9,10 ] solution mixing, [11][12][13][14][15] and surface-initiated polymerization. [ 16,17 ] As expected, k values of the polymer nanocomposites have indeed been improved, but there exist serious drawbacks in the nanocomposite approach. (1) The presence of a large contrast in k values between two phases augments the local electric fi eld distortions and results in a highly inhomogeneous fi eld distribution, and consequently, decreases E b . [ 4 ] As U e of dielectrics scales as the second power of the applied electric fi eld, a reduced E b would diminish any substantial improvement in energy storage capability even though k is increased. (2) The structural imperfections at the fi ller/ matrix interface such as fl aws and voids caused by the poor fi ller distribution and incompatibility between the inorganic and organic phases not only are detrimental to E b , but also give rise to large conduction loss. This, in turn, reduces the discharged energy density and shortens the lifetime of devices because of Joule heating. A Hybrid Material Approach Toward Solution-Processable Dielectrics Exhibiting Enhanced Breakdown Strength and High Energy DensityKuo Han , Qi Li , Chalathorn Chanthad , Matthew R. Gadinski , Guangzu Zhang , and Qing Wang * The ever-increasing demand for compact electronics and electrical power systems cannot be met with conventional dielectric materials with limited energy densities. Numerous efforts have been made to improve the energy densities of dielectrics by incorporating ceramic additives into polymer matrix. In spite of increased permittivities, thus-fabricated polymer nanocomposites typically suffer from signifi cantly decreased breakdown strengths, which preclude a substantial gain in energy density. Here...

Single-ion conducting electrolytes present a unique alternative to traditional binary salt conductors used in lithium-ion batteries. It has been shown theoretically that single-ion electrolytes can eliminate the salt concentration gradient and polarization loss in the cell that develop in a binary salt system, resulting in substantial improvements in materials utilization for high power and energy densities. Here, we describe synthesis and characterization of a class of single-ion electrolytes based on aromatic poly(arylene ether)s with pendant lithium perfluoroethyl sulfonates. The microporous polymer film saturated with organic carbonates exhibits a nearly unity Li + transference number, very high conductivities (e.g., > 10 −3 S m −1 at room temperature) over a wide range of temperatures, great electrochemical stability, and outstanding mechanical properties. Excellent cyclability with almost identical charge and discharge capacities has been demonstrated at ambient temperature in the batteries assembled from the prepared single-ion conductors.