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Zr-modified LiNi1/3Co1/3Mn1/3− xZr xO2 samples were prepared through a rheological-phase method. The results indicate that there is only partial Zr doping into the bulk phase of the LiNi1/3Co1/3Mn1/3O2 particles, whereas the rest of the Zr remained on the surface to form a Li2ZrO3 coating layer during the Zr-modification process. The Zr-modified LiNi1/3Co1/3Mn1/3− xZr xO2 samples show lower discharge specific capacities at low rates, however, which exhibit clearly improved rate capabilities than that of pristine LiNi1/3Co1/3Mn1/3O2. Among the Zr-modified LiNi1/3Co1/3Mn1/3− xZr xO2 samples, LiNi1/3Co1/3Mn1/3−0.01Zr0.01O2 ( x=0.01) shows the best rate capability, which exhibts158, 142, and 132 mAh g−1 at 1.0, 2.0, and 3.0 C, respectively. The related results indicate that the doped Zr in pristine LiNi1/3Co1/3Mn1/3O2 could improve the structure stability and the formation of an inactive Li2ZrO3 coating layer which could suppress the interfacial side reaction of LiNi1/3Co1/3Mn1/3O2. [ABSTRACT FROM AUTHOR]

The commercial Li 4 Ti 5 O 12 (LTO) is successfully modified by SrF 2 via a low temperature coprecipitation process. The results indicate that Sr 2+ and F − do not co-dope into the bulk phase of the LTO, but instead form a SrF 2 coating layer on the surface of the LTO. The suitable SrF 2 buffer layer could cover the catalytic active sites of the LTO and suppress the electrolyte reduction decomposition on the surface of the LTO, which means that the SrF 2 modification is favorable to suppress gas generation of the LIBs using LTO as anode material during charge/discharge cycles and storage. Moreover, according to optimized the amount of SrF 2 , the 2 wt% of SrF 2 in the SrF 2 modified LTO composites exhibits the best rate capability and an excellent cyclic performance. [ABSTRACT FROM AUTHOR]

Abstract: The influences of LiBF4, LiClO4, lithium bis(oxalato) borate (LiBOB), LiPF6 with VC and without VC, and the mixed electrolytes composed of different ratios of LiBOB and LiPF6 or LiClO4 on the electrochemical properties of Si/graphite/disordered carbon (Si/G/DC) composite electrode were systematically investigated by constant current charge–discharge and electrochemical impedance spectra (EIS) techniques. Scanning electron microscopy (SEM) was used to observe the change of electrodes in morphology after given cycle numbers. X-ray photoelectron spectroscopy (XPS) was employed to understand the influences of different mixed electrolytes on the composition of SEI layers. The results showed that Si/G/DC composite electrode in the mixed electrolytes presented better electrochemical performance than in single electrolyte. The compactness and compositions of SEI layers intensively influenced the cycle performance of Si/G/DC composite materials. LiBOB and additive VC had a good synergistic effect on the formation of the dense SEI layers. In particular, Si/G/DC in 0.5M LiBOB+0.38M LiPF6 electrolytes containing VC exhibited a high reversible capacity and excellent cycle performance. [Copyright &y& Elsevier]

Abstract: Binary conductive additives (BCA), formed by sonication of mesoporous carbon (MC) and acetylene black (AB), were used as conductive additives to improve the electrochemical performance of a LiCoO2 composite cathode. The electrochemical performance of the LiCoO2 composite cathode dispersed with BCA was investigated. The results showed that the electrochemical performance (including the discharge capacity, the discharge voltage and the total internal resistance) of a BCA loaded LiCoO2 composite cathode was better than that of a cathode loaded with AB. The possible mechanism is that the MC in BCA can adsorb and retain electrolyte solution, which allows an intimate contact between the lithium ions and the cathode active material LiCoO2 due to its large mesopore specific surface area. A simplified model was also proposed. [Copyright &y& Elsevier]

Abstract: Silicon/graphite/disordered carbon (Si/G/DC) is coated by Li2ZrO3 using Zr(NO3)4·5H2O and CH3COOLi·2H2O as coating reagents. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize Li2ZrO3-coated Si/G/DC composite. The Li2ZrO3-coated Si/G/DC composite exhibits a high reversible capacity with no capacity fading from 2nd to 70th cycle, indicating its excellent cycleability when used as anode materials for lithium ion batteries. A compact and stable solid-electrolyte interphase (SEI) layer is formed on the surface of Li2ZrO3-coated Si/G/DC electrode. Analysis of electrochemical impedance spectra (EIS) shows that the resistance of the coated material exhibits less variation during cycling, which indicates the integrity of electrode structure is kept during cycling. XPS shows that F and P elements do not appear in the SEI layers of Li2ZrO3-coated Si/G/DC electrode, while they have a relatively high content in SEI layers of Si/G/DC electrode. The improvement of Li2ZrO3-coated Si/G/DC is attributed to the decrease of lithium insertion depth and the formation of stable SEI film. [Copyright &y& Elsevier]