Spallation Neutron Production by 0.8, 1.2 and 1.6 GeV Protons on various Targets

Spallation neutron production in proton induced reactions on Al, Fe, Zr, W, Pb and Th targets at 1.2 GeV and on Fe and Pb at 0.8, and 1.6 GeV measured at the SATURNE accelerator in Saclay is reported. The experimental double-differential cross-sections are compared with calculations performed with different intra-nuclear cascade models implemented in high energy transport codes. The broad angular coverage also allowed the determination of average neutron multiplicities above 2 MeV. Deficiencies in some of the models commonly used for applications are pointed out.Comment: 20 pages, 32 figures, revised version, accepted fpr publication in Phys. Rev.

The use of deuterated ethyl acetate in highly concentrated electrolyte as a low-cost solvent for in situ neutron diffraction measurements of Li-ion battery electrodes

A low-cost deuterated electrolyte suitable for in situ neutron diffraction measurements of normal and high voltage Li-ion battery electrodes is reported here. Li[Ni0.4Mn0.4Co0.2]O2/graphite (NMC(442)/graphite) pouch cells filled with 1:0.1:2 (molar ratio) of lithium bis(fluorosulfonyl) imide (LiFSi):LiPF6: ethyl acetate (EA) and LiFSi:LiPF6:deuterated EA (d8-EA) electrolytes were successfully cycled between 2.8 V and 4.7 V at 40 C for 250 h without significant capacity loss, polarization growth, or gas production. The signal-to-noise ratio of neutron powder diffraction patterns taken on NMC(442) powder with a conventional deuterated organic carbonate-based electrolyte and filled with LiFSi:LiPF6:d8-EA electrolyte were virtually identical. Out of all the solvents widely available in deuterated form tested in highly-concentrated systems, EA was the only one providing a good balance between cost and charge-discharge capacity retention to 4.7 V. The use of such an electrolyte blend would half the cost of deuterated solvents needed for in situ neutron diffraction measurements of Li-ion batteries compared to conventional deuterated carbonate-based electrolytes

In-situ neutron diffraction study of a high voltage Li(Ni0.42Mn0.42Co0.16)O2/graphite pouch cell

The application of detailed in-situ neutron diffraction studies on lithium ion batteries has been limited in part due to the requirement of expensive deuterated carbonate-based electrolyte. This work presents an in-situ neutron diffraction study of the structural evolution of the Lix (Ni0.4Mn0.4Co0.2)O2 (NMC442) positive electrode material using a recently-developed low-cost deuterated ethyl acetate-based electrolyte. Rietveld analysis show that the NMC442 c lattice parameter gradually increases until x = 0.47 (4.03 V) and then decreases during the first charge. The decreasing trend of the c lattice parameter with time during the hold at 4.7 V and 4.9 V agrees very well with the change of current. Overall the structural changes appear highly reversible when 4.7 V is used as an upper cutoff voltage, even following a 10 h hold at 4.7 V. However, the electrode/electrolyte changes dramatically when charged and held at 4.9 V. There is a significant drop in background attributed to electrolyte decomposition and an unexpected increase in the a lattice parameter is noted after the 4.9 V hold. Therefore, the electrolyte system used is both beneficial for in-situ neutron diffraction studies and battery performance until 4.7 V, but appears to degrade in combination with the electrode at 4.9 V. By comparison to Li(Ni0.8Mn0.1Co0.1)O2 (NMC811), the contraction of the c lattice with increasing voltage and decreasing lithium content of the NMC442 is less rapid. The transition metal composition significantly affects the c lattice contraction above 4.0 V

Effect of Sulfate Electrolyte Additives on LiNi_1/3Mn_1/3Co_1/3O₂/Graphite Pouch Cell Lifetime: Correlation between XPS Surface Studies and Electrochemical Test Results

The role of two homologous cyclic sulfate electrolyte additives, trimethylene sulfate (or 1,3,2-dioxathiane-2,2-dioxide, TMS) and ethylene sulfate (or 1,3,2-dioxathiolane-2,2-dioxide, DTD), used either alone or in combination with vinylene carbonate (VC) on the lifetime of LiNi_1/3Mn_1/3­Co_1/3O₂(NMC)/graphite pouch cells was studied by correlating data from gas chromatography/mass spectroscopy (GC–MS), d<i>Q</i>/d<i>V</i> analysis, ultrahigh precision coulometry, storage experiments, and X-ray photoelectron spectroscopy. For VC alone, more stable and protective SEI films were observed at the surface of both electrodes due to the formation of a polymer of VC, which results in higher capacity retention. For TMS, similar chemical SEI compositions were found compared to the TMS-free electrolytes. When VC was added to TMS, longer cell lifetime is attributed to VC. For DTD, a cell lifetime that competes with VC was explained by a preferential reduction potential and a much higher fraction of organic compounds in the SEI films. When VC was added to DTD, the contribution of both additives to the SEI films is consistent with the initial reactivity observed from d<i>Q</i>/d<i>V</i> and GC–MS analysis