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Lithium−sulfur (Li/S) technology holds great promise for efficient, safe, and economic next-generation batteries. However, commercialization is limited by some issues, which are related to the fast degradation of Li/S cells and poor rate capability. Existing strategies addressing these issues are often unsuitable for commercialization because of their complexity and lack of scalability. This Letter presents a simple, cheap, and scalable synthesis of a sulfur-based cathode material from commercially available poly(methyl methacrylate)/poly-(acrylonitrile) (PMMA/PAN) fibers. Thermal conversion of PMMA/PAN fibers with elemental sulfur yields sulfurized poly(acrylonitrile) (SPAN) with up to 46 wt % covalently bound sulfur. The fibrous morphology with cylindrical macropores helps to form electronic conduction networks in the cathode and provides directed diffusion pathways for ions. Consequently, these Li/SPAN cells show low internal resistances, high initial capacities up to 1672 mAh•g −1 sulfur , high rate capabilities up to 8C, and excellent cycle stabilities over 1200 cycles. In addition, structure and postmortem analysis allow the correlation of electrochemical performance with SPAN's chemical structure.

A detailed study is presented on the formation of MoO(2) nanoparticles from the dissolution of the precursor to the final rodlike product, with a focus on the exploration of the inorganic reaction occurring ahead of the nucleation step, and interplay between size and crystal structure of MoO(2). In situ X-ray absorption spectroscopy experiments show that the crystallization and the growth process of MoO(2) nanorods is initiated by rapid reduction of the MoO(2) Cl(2) precursor in benzyl alcohol and acetophenone. This reaction triggers the nucleation of 2 nm MoO(2) particles with spherical shape and hexagonal crystal structure. The transformation from spheres into rods emerges as a complex process driven by oriented attachment. High-resolution transmission electron microscopy and X-ray diffraction results provide evidence that the 2 nm particles first aggregate into 5-20 nm-large oriented assemblies. The increase in particle size induces the phase transition from hexagonal to the less symmetrical monoclinic crystal structure, and finally the transformation into rods. Is it shown that electrodes for lithium-ion batteries based on MoO(2) nanorods have a long-term cycling life. The specific discharge capacity even after 200 cycles at a discharge rate of 1 C is about 300 Ah kg(-1) .

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The effect of metallic lithium depositing on the negative electrode surface of a carbon-based lithium-ion battery instead of intercalating into the graphitic layers, namely lithium plating, can be assigned to charging at low temperatures and/or high currents. Cell parameters, such as performance and safety, are negatively influenced by this phenomenon. Elemental lithium deposited on the negative electrode requires more space than the intercalated compound and therefore increases the cell volume. Thus, the thickness changes during cycling can be used as a qualitative indicator for lithium plating. In this context, two different non-destructive experimental setups detecting the thickness profiles in situ are presented. Moreover, a quantitative titration technique to determine the exact amount of lithium deposited is established.The utilization of lithium-ion batteries (LIBs) in automotive applications requires extended cycle life and prolonged calendar life. Therefore, the investigation of their capacity-fading mechanisms is of increasing interest. 1 Carbon-based materials, in particular graphites, are commonly used as negative electrodes in these energy storage systems. 2,3 Thus, most studies regarding negative electrode-aging mechanisms were conducted with graphite-based cells. 4 Mechanisms, such as cracking of particles due to volume changes, decomposition of the binder, growth of the solid electrolyte interface (SEI), and metallic lithium deposition are primarily influences on the aging process of an negative electrode. 5 The latter degradation process, also known as lithium plating, is usually formed as a consequence of charging at low temperatures, high state of charge (SOC) and high charge rates. 6 These conditions lead to a polarized negative electrode and poorer electrode kinetics. As soon as the potential of the negative electrode falls below 0 V measured versus the Li/Li + half cell, lithium plating is thermodynamically favored on the negative electrode surface. 6,7 The structure of deposited lithium depends on the current applied. 8 Orsini et al. have demonstrated that lithium deposition on metallic electrode surfaces generally has a mossy structure through low-current charging, whereas high-charge rates lead to dendrites. 8,9 Lithium dendrites, which occur on graphite as well, have a serious effect on the cell's safety and performance issues. The dendrites, which grow directly on the negative electrode, can cause short circuits, leading to serious fire hazards associated with the flammable organic electrolyte. 6,10,11

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A microwave-assisted liquid-phase synthesis route to LiFePO 4 doped with divalent (Mn, Ni, Zn), trivalent (Al) and tetravalent (Ti) metal ions in varying concentrations is presented. In spite of the low synthesis temperature of 180 C all the as-synthesized powders are highly crystalline. The short reaction times of just a few minutes represent the basis for an efficient and time-saving screening of different types of dopants with respect to optimized electrochemical performance in lithium-ion batteries. The Ni-and Zn-doped LiFePO 4 with nominal dopant concentrations of 7 and 2 mol%, respectively, outperformed all the other samples, offering initial specific charge of 168 A h kg À1 and excellent capacity retention of 97% after 300 full cycles. A discharge rate of 8 C still resulted in 152 A h kg À1 after 50 cycles. The electrochemical investigations are accompanied by a detailed structural and morphological characterization. Whereas the elemental composition, obtained from quantitative energy dispersive X-ray (EDX) analysis, and the electric conductivity could not directly be correlated to the electrochemical performance, the Rietveld analysis showed that the better the fit the better the electrochemical performance. This observation points to a relation between the phase-purity of a sample and its electrochemical properties.

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