The combined use of soft carbon (PeC) as anodic material, and propylene carbonate (PC) as electrolyte solvent is a promising strategy for the realization of high performance lithium-ion capacitors (LIC). PeC electrodes display a capacity of around 80 mAhg −1 during cycling carried out at 5C, which can be maintained for more than 10,000 cycles. This performance is higher than that displayed by most of the carbonaceous electrodes so far proposed for LIC. PC is known to be a safer electrolyte compared to mixtures of organic carbonates used so far in LIC, and therefore its use is beneficial for the realization of safer LIC. When a correct pre-lithiation process is applied, LICs based on PeC and PC display high performance in terms of capacity and cycling stability. When a current density of 10.6 mA/cm 2 (corresponding to 5.6 A/g) is applied to a LIC average energy and power of 21.7 Wh kg −1 and 4.1 kW kg −1 (based to the total active material), respectively, were achieved.

Lithium transition metal oxides are commonly used as cathode materials in modern mobile and stationary power supplies. Lithium transition metal fluorides are an interesting new class of materials for lithium ion batteries featuring a higher voltage due to substitution of oxygen by the more electronegative fluorine. A sol-gel based process with trifluoroacetic acid as fluorine source was used to synthesize LiNiFeF 6 . Ball-milling with carbon and binder was applied to obtain an electrochemical active LiNiFeF 6 /carbon/binder nano composite. In this study we report on the first electrochemical characterization of a quaternary lithium transition metal fluoride as positive electrode for lithium ion batteries, containing two different transition metals. After 20 cycles of galvanostatic cycling a reversible specific capacity of 88 mAh/g, which is 92% of the initial specific capacity, was retained. In a rate performance test with rates of up to 1C a reversible capacity of 53 mAh/g was obtained. The electrochemically active redox couple Fe 3+ /Fe 2+ was identified by Mössbauer spectroscopy and cyclic voltammetry.The search for alternative cathode materials for lithium batteries to replace common oxide materials has generated considerable research activity to provide reliable battery systems for large-scale applications such as electric vehicles and grid storage. Previous investigations have been performed on a large number of compounds that can be applied as cathode materials for secondary lithium ion batteries such as layered LiMO 2 , silicates Li 2 MSiO 4 and polyanionic olivines LiMPO 4 (M = Fe, Mn, Co). 1,2 Several hundred publications have been published on quaternary lithium metal oxides. 4,5 However, no electrochemical investigations are given about quaternary lithium transition metal fluorides as positive electrode materials. Lithium transition metal fluorides in particular are very promising materials compared to common oxide materials with corresponding electrochemically active cations because the more electronegative fluorine atoms increase the redox potential leading to a higher specific energy. 3 Regarding the theoretic capacity of quaternary lithium transition metal fluorides, they could offer multiple redox couples e.g. M 3+/2+ or M 4+/3+ (e.g. M = V, Cr, Mn, Co or Ni) (eq.

We present the synthesis, crystal structure, hardness, IR/Raman and UV/Vis spectra, and FP-LAPW calculations of the electronic structure of Li(2)B(12)Si(2), the first ternary compound in the system Li/B/Si. Yellow, transparent single crystals were synthesized from the elements in tin as solvent at 1500 degrees C in h-BN crucibles in arc-welded Ta ampoules. Li(2)B(12)Si(2) crystallizes orthorhombic in the space group Cmce (no. 64) with a=6.1060(6), b=10.9794(14), c=8.4050(8) A, and Z=4. The crystal structure is characterized by a covalent network of B(12) icosahedra connected by Si atoms and Li atoms located in interstitial spaces. The structure is closely related to that of MgB(12)Si(2) and fulfils the electron-counting rules of Wade and Longuet-Higgins. Measurements of Vickers (H(V)=20.3 GPa) and Knoop microhardness (H(K)=20.4 GPa) revealed that Li(2)B(12)Si(2) is a hard material. The band gap was determined experimentally and calculated by theoretical means. UV/Vis spectra revealed a band gap of 2.27 eV, with which the calculated value of 2.1 eV agrees well. The IR and Raman spectra show the expected oscillations of icosahedral networks. Theoretical investigations of bonding in this structure were carried out with the FP-LAPW method. The results confirm the applicability of simple electron-counting rules and enable some structural specialties to be explained in more detail.

Focused ion beam/scanning electron microscopy tomography (FIB/SEMt) and synchrotron X-ray tomography (Xt) are used to investigate the same lithium manganese oxide composite cathode at the same specific spot. This correlative approach allows the investigation of three central issues in the tomographic analysis of composite battery electrodes: (i) Validation of state-of-the-art binary active material (AM) segmentation: Although threshold segmentation by standard algorithms leads to very good segmentation results, limited Xt resolution results in an AM underestimation of 6 vol% and severe overestimation of AM connectivity. (ii) Carbon binder domain (CBD) segmentation in Xt data: While threshold segmentation cannot be applied for this purpose, a suitable classification method is introduced. Based on correlative tomography, it allows for reliable ternary segmentation of Xt data into the pore space, CBD, and AM. (iii) Pore space analysis in the micrometer regime: This segmentation technique is applied to an Xt reconstruction with several hundred microns edge length, thus validating the segmentation of pores within the micrometer regime for the first time. The analyzed cathode volume exhibits a bimodal pore size distribution in the ranges between 0–1 μm and 1–12 μm. These ranges can be attributed to different pore formation mechanisms.