Hard-carbon is considered as one of the most promising anode materials for sodium-ion batteries (SIBs).

Using a materials genome approach on the basis of the density functional theory, we have formulated a new class of inorganic electrolytes for fast diffusion of Li + ions, through fine-tuning of lattice chemistry of anti-perovskite structures. Systematic modelling has been carried out to elaborate the structural stability and ion transportation characteristics in Li 3 AX based cubic anti-perovskite, through alloying on the chalcogen lattice site (A) and alternative occupancy of the halogen site (X). In addition to identifying effective ways for reduction of diffusion barriers for Li + ions in anti-perovskite phases via suitable designation of lattice occupancy, the current theoretical study leads to discovery and synthesis of a new phase with a double-anti-perovskite structure, Li 6 OSI 2 (or Li 3 O 0.5 S 0.5 I). Such a new compound is of fairly low activation barrier for Li + diffusion, together with a wide energy band gap to hinder conduction of electrons.Keywords: First-principles materials formulation; Superfast solid lithium ion conductor; double anti-perovskite; Li-ion battery Ⅰ. IntroductionSolid-state electrolytes (SSE) for lithium-ion battery (LIB) have attracted enormous attention, owing to their highly superior safety advantage over organic liquid ionic conductors and great potential in offering improved electrochemical capacity with lithium anode. 1-4 Still, extensive substitution of liquid organic electrolytes by SSE is yet desired, unless related technologies are further improved to meet the following key criteria: (a) High Li + ionic conductivity being greater than 1 mScm -1 (current technical request for liquid organic electrolytes); (b) Low electronic conductivity to avoid self-discharging in service; (c) Broad working temperature for stable operation from −100 to 300 °C; (d) being electrochemically compatible to lithium anode, 5 and (e) being light, economical, and environmentally friendly.As a landmark breakthrough, a new family of SSEs based on multi-component sulfides has been shown to provide significantly increased ionic conductivity, making them potential candidates as fast ion conductor for solid lithium-ion batteries. The discovery of Li 10 GeP 2 S 12 (LGPS), 6,7 which had high bulk Li + ions conductivity of over 10 mScm -1 at room temperature, demonstrated for the first time that Li + ionic conductivity in solid electrolytes could be superior to that in organic liquid electrolytes. The efficient conduction pathway for Li + was along the longer c-axis of the tetragonal phase of Li 10 GeP 2 S 12 , with an activation barrier of 0.22-0.25 eV for Li + diffusion. 6,7 The motivation in replacing the expensive Ge content led to discovery of a cheaper candidate Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , 8,9 which exhibited an even higher ionic conductivity of about 25 mScm -1 at room temperature. However, this latter electrolyte was shown not to be electrochemically stable with the lithium anode, which is considered an issue to hinder the full potential of the lithium metal anode, which has the highe...

A solid electrolyte with superb Li+ conductivity through tuning of the lattice chemistry in Li6PS5Cl. The ionic conductivity is enhanced through the combined effect of excess Li and substitution of S with Te.

Undoped, Cr-doped, and Nb-doped LiMn(1.5)Ni(0.5)O4 (LNMO) is synthesized via a PVP (polyvinylpyrrolidone)-combustion method by calcinating at 1000 °C for 6 h. SEM images show that the morphology of LNMO particles is affected by Cr and Nb doping. Cr doping results in sharper edges and corners and smaller particle size, and Nb doping leads to smoother edges and corners and more rounded and larger particles. The crystal and electron structure is investigated by XRD- and synchrotron-based soft X-ray absorption spectroscopy (sXAS). Cr doping and light Nb doping (LiNb(0.02)Ni(0.49)Mn(1.49)O4) improve the rate performance of LNMO. To explore the reason for rate-performance improvement, we conducted potential intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) tests. The Li(+) chemical diffusion coefficient at different state of charge (SOC) is calculated and suggests that both Cr and light Nb doping speeds up Li(+) diffusion in LNMO particles. The impedance spectra show that both R(SEI) and R(ct) are reduced by Cr and light Nb doping. The cycling performance is improved by Cr or Nb doping, and Cr doping increases both Coulombic efficiency and energy efficiency of LNMO at 1 C cycling. The LiCr(0.1)Ni(0.45)Mn(1.45)O4 remains at 94.1% capacity after 500 cycles at 1 C, and during the cycling, the Coulombic efficiency and energy efficiency remain at over 99.7% and 97.5%, respectively.

Solid electrolytes based on theoretically identified double antiperovskite phases Li 6 OSI 2 were successfully synthesized. Experimental characterization supported the theoretical prediction that S substitution of O leads to stabilization of the double antiperovskite structure and lattice softening to significantly enhance ionic conductivity, so that the total Li + conductivity in Li 6.5 OS 1.5 I 1.5 was two to three orders better than that of the best stoichiometric antiperovskite phase Li 3 OCl. However, both antiperovskite and double antiperovskite materials are fundamentally susceptible to surface reconstruction, which is behind significant boundary resistances typically known for materials based on antiperovskite hali-chalcogenides. Such a surface related problem was then effectively reduced through amorphous phase formation, thus offering a feasible route to exploit the full potential of this class of new materials as competitive candidates for solid Li-ion batteries.