Bipolar ionomer electrolytes with desirable self-discharge suppression for supercapacitors

Supercapacitors based on electric double layers are prone to serious self-discharge due to electrolyte ion desorption and the resulting energy loss severely limits the application range of supercapacitors.Rational design of polymer electrolyte systems to address this problem shows considerable generality and high feasibility.Herein,we reported a quasi-solid-state bipolar ionomer electrolyte prepared by an in-situ layer-by-layer ultraviolet-curing method,which has an integrated Janus structure with an intermediate binding layer.Based on the synergistic effect of confining impurity ions by ionizable groups and electrostatic repulsion to stabilize the electric double layers and superimposing synergies on both sides,the assembled device not only possesses ideal supercapacitor characteristics,but also exhibits an ultrahigh voltage retention of 71% after being left to stand for 100 h after being fully charged.Furthermore,through the quasi-in-situ energy dispersive X-ray spectroscopy linear scanning,the characteristics of ion diffusion in this ionomer electrolyte are revealed,suggesting its correlation with self-discharge behavior.

Nano storage-boxes constructed by the vertical growth of MoS_(2 )on graphene for high-performance Li-S batteries

In order to accelerate the reaction kinetics of lithium-sulfur batteries, the introduction of electro catalysis and proper structural control of the sulfur cathode is urgently needed. MoS_(2) nano sheets was selectively grown vertically (V-MoS_(2)) on the microwave-reduced graphene (rGO) sheets through chemical coupling to construct a self-supporting sulfur cathode with a nano storage-box structure (V-MoS_(2) as the wall and rGO as the bottom). RGO, which has a high conductivity of 37 S cm^(−1), greatly accelerates the transfer of electrons from the active sites on the edge of the layer to the solution. The introduction of carbon tubes can connect the abundant pores in the foam and act as a long-range conductive path. The 2D-orthogonal-2D structure maximally exposes the edge active sites of MoS_(2), and together with graphene form a nano reactor of sulfur, intermediate lithium polysulfides and discharge product Li_(2)S(2). The effective combination of the microstructure confinement of the nano storage-boxes and the efficient synchronous catalytic mechanism of V-MoS_(2) greatly improves the electrochemical performance of the lithium-sulfur batteries. As a result, the assembled lithium-sulfur battery displays a high initial discharge capacity of 1379 mAh g^(−1), good cycle stability (86% capacity retention after 500 cycles at 0.1C) and superior rate performance.

Fabrication of porous lithium titanate self-supporting anode for high performance lithium-ion capacitor

Lithium titanate has unique "zero-strain" characteristics, which makes it promising for rapid energy storage lithium-ion capacitors. However, extremely low electronic conductivity and lithium ion diffusion coefficient severely limit its performance at high rate. Herein, we have constructed in situ clusters of porous lithium titanate nanoparticles on self-supporting carbon nanotube film by combining iron oxide hard template method and F127 soft template method. Due to the nano-structured particle size and the penetrating lithium ion transmission channel, a greatly improved lithium ion diffusion coefficient has been achieved, which brings significantly better electrochemical performance than dense lithium titanate. By assembling with a durable graphene foam cathode, a lithium-ion capacitor with an energy density of up to 101.8 Wh kg-1 was realized(at a power density of 436.1 W kg-1). And its capacitance retention reaches 84.8% after 5000 cycles. With such an alluring result, our work presents a novel lithium-ion capacitor system with practical application prospects.