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Porous TiO2/C nanocomposite shells with high capacity, excellent cycle stability, and rate performance have been prepared. The synthesis involves coating colloidal TiO2 nanoshells with a resorcinol-formaldehyde (RF) layer with controllable thickness through a sol-gel-like process, and calcining the composites at 700 °C in an inert atmosphere to induce crystallization from amorphous TiO2 to anatase and simultaneous carbonization from RF to carbon. The cross-linked RF polymer contributes to the high stability of the shell morphology and the porous nature of the shells. A strong dependence of the capacity on the amount of incorporated carbon has been revealed, allowing the optimization of the electrode structure for high-rate cell performance.

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The crystal structure and electrochemical properties of LiNi1/3Mn1/3Co1/3O2 (NMC) synthesized from a lithium ion battery recovery stream have been studied previously. In this report, we study the Cu impurity effects on NMC in detail. The difference in crystal structures and electrochemical properties were examined for pure and copper impurity included products. Scanning electron microscopy figures show that the precursor particles of NMC are slightly bigger than that of NMC with copper impurity. After undergoing 150 cycles at 2C, X-ray diffraction refinements results show that the lattice parameters for impurity containing NMC and pure NMC change to different extents. Furthermore, due to the minor change of lattice parameters, copper-containing NMC offers a more stable capacity retention compared to pure NMC.

A previously introduced POSSIM (POlarizable Simulations with Second order Interaction Model) force field has been extended to include parameters for small molecules serving as models for peptide and protein side-chains. Parameters have been fitted to permit reproducing many-body energies, gas-phase dimerization energies and geometries and liquid-phase heats of vaporization and densities. Quantum mechanical and experimental data have been used as the target for the fitting. The POSSIM framework combines accuracy of a polarizable force field and computational efficiency of the second-order approximation of the full-scale induced point dipole polarization formalism. The resulting parameters can be used for simulations of the parameterized molecules themselves or their analogues. In addition to this, these force field parameters are currently being employed in further development of the POSSIM fast polarizable force field for proteins.

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We have studied stability of polyalanine alpha-helices with lysine residues added at C-and N-termini in gas-phase and aqueous solution. Monte Carlo simulations with the fixed-charges OPLS-AA and our polarizable POSSIM force fields were carried out. The results of the simulations confirm previously observed phenomena of the helix being stable with the LYS residue on the C-terminus and losing its helical structure if the charged LYS residue is located at the N-terminus of the polypeptide in gas-hase. Both OPLS-AA and POSSIM force fields performed essentially similarly, thus validity of the both for reproducing and predicting structures of such polypeptides has been confirmed. We have also studied the effect of replacing the normal N- and C-termini with methyl capping (this approach is often used in computational studies). Our results have demonstrated that the structure and stability of the polypeptides do not depend significantly on such a substitution although details of the resulting structure may change. The liquid-state simulations produced stable alpha-helixes regardless of the position of the protonated lysine residue. Overall, we have validated our polarizable POSSIM force field and the techniques used in the simulations, since the change of the helix structure as a function of the position of the LYS residue depends on a fine balance of energy contributions, and our methodology reproduced this balance well.

Silicon is a very promising anode material for lithium ion batteries. It has a 4200 mAh/g theoretical capacity, which is ten times higher than that of commercial graphite anodes. However, when lithium ions diffuse to Si anodes, the volume of Si will expand to almost 400% of its initial size and lead to the crack of Si. Such a huge volume change and crack cause significant capacity loss. Meanwhile, with the crack of Si particles, the conductivity between the electrode and the current collector drops. Moreover, the solid electrolyte interphase (SEI), which is generated during the cycling, reduces the discharge capacity. These issues must be addressed for widespread application of this material. In this work, caramel popcorn shaped porous silicon particles with carbon coating are fabricated by a set of simple chemical methods as active anode material. Si particles are etched to form a porous structure. The pores in Si provide space for the volume expansion and liquid electrolyte diffusion. A layer of amorphous carbon is formed inside the pores, which gives an excellent isolation between the Si particle and electrolyte, so that the formation of the SEI layer is stabilized. Meanwhile, this novel structure enhances the mechanical properties of the Si particles, and the crack phenomenon caused by the volume change is significantly restrained. Therefore, an excellent cycle life under a high rate for the novel Si electrode is achieved.