A porous three-dimensional nitrogen-doped graphene (3D-NG) was introduced as an interconnected framework for sulfur in lithium-sulfur batteries. The 3D-NG-sulfur composite (3D-NGS) with a high sulfur content of 87.6 wt% was synthesized via a facile one-pot solution method and sulfur was well dispersed within it. The as-designed 3D-NGS composite exhibits excellent rate capability and cyclability.The discharge specific capacity is 792 mA h g À1 after 145 cycles at a current density of 600 mA g À1 and the capacity fading rate is 0.05% per cycle. Even at a high rate of 1500 mA g À1 , the composite still shows a good cycle performance with a capacity of 671 mA h g À1 after 200 cycles. The outstanding electrochemical performance can be attributed to the flexible porous 3D structure and N-doping in graphene. The flexible 3D-NG can provide a conductive framework for electron transport and alleviate the volume effect during cycling. N-doping can facilitate the penetration of Li ions across the graphene and restrain sulfur due to the strong chemical bonding between S and the nearby N atoms.

energy density, high voltage, and long cycle life. [ 2 ] As one of the most widely used cathode materials, LiNi x Mn y Co z O 2 (labeled as NMC) has been investigated extensively, due to their high reversible capacity, good environmental compatibility, and relatively high Li-ion diffusivity. In the previous works, different kinds of NMC materials with different content ratio of Ni, Co, and Mn have been developed, and their electrochemical properties have also been studied, such as Li(Ni 1/3 Mn 1/3 Co 1/3 ) O 2 (111), [ 3,4 ] Li(Ni 0.4 Mn 0.4 Co 0.2 )O 2 (442), [ 5 ] Li(Ni 0.42 Mn 0.42 Co 0.16 )O 2 (552), [ 6 ] Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 (532), [ 7 ] Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 (622), [ 8 ] and Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 (71515). [ 9 ] For example, Noh et al. compared the electrochemical properties including the Li-ion diffusion coeffi cient, capacity retention, and electrochemical stabilities (25 to 55 °C) of layered NMC cathode materials ((111), (532), (622), (71515), (811) and Li(Ni 0.85 Mn 0.075 Co 0.075 )O 2 ) at room temperature and found that the Ni content had a great infl uence on the electrochemical properties. [ 10 ] Solid phase diffusion coeffi cient ( D s ) is one of the most important parameters for the active materials of the LIBs, as it determines the charge and discharge rate capability directly. In particular, for high power density applications, fast Li-ion transport in cathode materials is a key factor and must be needed. As a result, many experimental and theoretical works have been devoted to investigating the Li-ion diffusion properties in layered cathode materials. [ 11,12 ] However, to the best of our knowledge, there is little work reported to study the relationship between the layer distance and kinetics of Li-ion diffusion in different temperatures of layered NMC cathode materials systematically, which is important for LIBs applied in multitemperature environments.At the same time, in order to measure D s accurately, many methods such as galvanostatic intermittent titration technique (GITT), [ 3,[13][14][15][16] potentiostatic intermittent titration technique (PITT), [ 14,17 ] electrochemical impedance spectroscopy, [ 18 ] and cyclic voltammetry [ 19 ] have been developed in the past decades. Although factors such as the inaccuracy of the assumptions, Understanding and optimizing the temperature effects of Li-ion diffusion by analyzing crystal structures of layered Li(Ni x Mn y Co z )O 2 (NMC) ( x + y + z = 1) materials is important to develop advanced rechargeable Li-ion batteries (LIBs) for multi-temperature applications with high power density. Combined with experiments and ab initio calculations, the layer distances and kinetics of Li-ion diffusion of LiNi x Mn y Co z O 2 (NMC) materials in different states of Li-ion de-intercalation and temperatures are investigatedsystematically. An improved model is also developed to reduce the system error of the "Galvanostatic Intermittent Titration Technique" with a correction of NMC particle size distribution. The Li-ion diff...

A 3D-printing technology and printed 3D lithium-ion batteries (3D-printed LIBs) based on LiMn 0.21 Fe 0.79 PO 4 @C (LMFP) nanocrystal cathodes are developed to achieve both ultrahigh rate and high capacity. Coin cells with 3D-printed cathodes show impressive electrochemical performance: a capacity of 108.45 mAh g −1 at 100 C and a reversible capacity of 150.21 mAh g −1 at 10 C after 1000 cycles. In combination with simulation using a pseudo 2D hidden Markov model and experimental data of 3D-printed and traditional electrodes, for the fi rst time deep insight into how to achieve the ultrahigh rate performance for a cathode with LMFP nanocrystals is obtained. It is estimated that the Li-ion diffusion in LMFP nanocrystal is not the rate-limitation step for the rate to 100 C, however, that the electrolyte diffusion factors, such as solution intrinsic diffusion coeffi cient, effi ciency porosity, and electrode thickness, will dominate ultrahigh rate performance of the cathode. Furthermore, the calculations indicate that the above factors play important roles in the equivalent diffusion coeffi cient with the electrode beyond a certain thickness, which determines the whole kinetic process in LIBs. This fundamental study should provide helpful guidance for future design of LIBs with superior electrochemical performance.

Calcium phosphate cements (CPCs) are clinically effective void fillers that are capable of bridging calcified tissue defects and facilitating regeneration. However, CPCs are completely synthetic/inorganic, unlike the calcium phosphate that is found in calcified tissues, and they lack an architectural organization, controlled assembly mechanisms, and have moderate biomechanical strength, which limits their clinical effectiveness. Herein, we describe a new class of bioinspired CPCs that can glue tissues together and bond tissues to metallic and polymeric biomaterials. Surprisingly, alpha tricalcium phosphate cements that are modified with simple phosphorylated amino acid monomers of phosphoserine (PM-CPCs) bond tissues up to 40-fold stronger (2.5–4 MPa) than commercial cyanoacrylates (0.1 MPa), and 100-fold stronger than surgical fibrin glue (0.04 MPa), when cured in wet-field conditions. In addition to adhesion, phosphoserine creates other novel properties in bioceramics, including a nanoscale organic/inorganic composite microstructure, and templating of nanoscale amorphous calcium phosphate nucleation. PM-CPCs are made of the biocompatible precursors calcium, phosphate, and amino acid, and these represent the first amorphous nano-ceramic composites that are stable in liquids.