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University of Science and Technology Beijing
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Papers by H. Santner
Journal of Power Sources, 2003
The lithium-ion battery anode performance of graphites with and without high amounts of rhombohed... more The lithium-ion battery anode performance of graphites with and without high amounts of rhombohedral phase in the structure has been investigated. A main outcome was that in addition to possible graphite bulk structure effects, there are also strong influences of the graphite surface and the graphite ''sub-surface'' (part of the graphite bulk at the border of the particle near the surface) on the solid electrolyte interphase (SEI) formation process and on the tendency to solvent co-intercalation into graphite. Using transmission electron microscopy with atomic resolution, we indeed could determine unique and also different surface and ''sub-surface'' morphologies for the two graphites. In case of the graphite without rhombohedral phase, unique convoluted graphene layers could be determined at the prismatic surfaces; in case of the graphite with a high rhombohedral phase content a strongly disordered, approximately 1 nm thick ''sub-surface'' layer could be determined. The anode performance depends primarily on these surface and ''sub-surface'' graphite properties and the used electrolytes. The differences in the ''sub-surface'' layer structure have a most significant influence on the performance in an ethylene carbonate/dimethyl carbonate electrolyte. The differences in surface structure and morphology are considered to have the highest impact in a propylene carbonate/ethylene sulfite-based electrolyte. For ethylene carbonate/diethyl carbonate electrolyte, the performance differences are small so that no strong dependence on surface or ''sub-surface'' structures could be observed. #
Journal of Power Sources, 2003
We present results on the electrolyte additive acrylic acid nitrile (AAN), which allows the use o... more We present results on the electrolyte additive acrylic acid nitrile (AAN), which allows the use of propylene carbonate (PC)-based electrolytes together with graphitic anodes. This report will focus on the basic electrochemical properties and on XPS results of the films formed in the presence of AAN. Further data on in situ investigations of AAN is presented in another paper of this proceedings. The combination of both reports gives strong evidence, that the initiative step for solid electrolyte interphase (SEI) formation is a cathodic, i.e. by reduction induced electro-polymerisation of the vinyl-group. It is concluded that this electro-polymerisation may also be a main reduction mechanism of other vinyl compounds such as vinylene carbonate (VC), vinylene acetate and others. #
Analytical and Bioanalytical Chemistry, 2004
Lithium-ion batteries operate beyond the thermodynamic stability of the aprotic organic electroly... more Lithium-ion batteries operate beyond the thermodynamic stability of the aprotic organic electrolyte used and electrolyte decomposition occurs at both electrodes. The electrolyte must therefore be composed in a way that its decomposition products form a film on the electrodes which stops the decomposition reactions but is still permeable to the Li(+) cations which are the charge carriers. At the graphite anode, this film is commonly referred to as a solid electrolyte interphase (SEI). Aprotic organic compounds containing vinylene groups can form an effective SEI on a graphitic anode. As examples, vinyl acetate (VA) and acrylonitrile (AN) have been investigated by in-situ Fourier transform infrared (FTIR) spectroscopy in a specially developed IR cell. The measurements focus on electrolyte decomposition and the mechanism of SEI formation in the presence of VA and AN. We conclude that cathodic reduction of the vinylene groups (i.e., via reduction of the double bond) in the electrolyte additives is the initiating and thus a most important step of the SEI-formation process, even in an electrolyte which contains only a few percent (i.e. electrolyte additive amounts) of the compound. The possibility of electropolymerization of the vinylene monomers in the battery electrolytes used is critically discussed on the basis of the IR data obtained.
Journal of Power Sources, 2006
The long-term formation kinetics of the solid electrolyte interphase (SEI) was studied on graphit... more The long-term formation kinetics of the solid electrolyte interphase (SEI) was studied on graphite electrodes in 1M LiClO4/PC with 5% acrylonitrile (AN) as electrolyte additive by electrochemical impedance spectroscopy at 1.0 and 0.5V versus Li/Li+, i.e. mainly outside the graphite intercalation region. To support the interpretation of the results, comparative experiments with Ni and Pt electrodes were performed at the
Journal of Power Sources, 2003
The lithium-ion battery anode performance of graphites with and without high amounts of rhombohed... more The lithium-ion battery anode performance of graphites with and without high amounts of rhombohedral phase in the structure has been investigated. A main outcome was that in addition to possible graphite bulk structure effects, there are also strong influences of the graphite surface and the graphite ''sub-surface'' (part of the graphite bulk at the border of the particle near the surface) on the solid electrolyte interphase (SEI) formation process and on the tendency to solvent co-intercalation into graphite. Using transmission electron microscopy with atomic resolution, we indeed could determine unique and also different surface and ''sub-surface'' morphologies for the two graphites. In case of the graphite without rhombohedral phase, unique convoluted graphene layers could be determined at the prismatic surfaces; in case of the graphite with a high rhombohedral phase content a strongly disordered, approximately 1 nm thick ''sub-surface'' layer could be determined. The anode performance depends primarily on these surface and ''sub-surface'' graphite properties and the used electrolytes. The differences in the ''sub-surface'' layer structure have a most significant influence on the performance in an ethylene carbonate/dimethyl carbonate electrolyte. The differences in surface structure and morphology are considered to have the highest impact in a propylene carbonate/ethylene sulfite-based electrolyte. For ethylene carbonate/diethyl carbonate electrolyte, the performance differences are small so that no strong dependence on surface or ''sub-surface'' structures could be observed. #
Journal of Power Sources, 2003
We present results on the electrolyte additive acrylic acid nitrile (AAN), which allows the use o... more We present results on the electrolyte additive acrylic acid nitrile (AAN), which allows the use of propylene carbonate (PC)-based electrolytes together with graphitic anodes. This report will focus on the basic electrochemical properties and on XPS results of the films formed in the presence of AAN. Further data on in situ investigations of AAN is presented in another paper of this proceedings. The combination of both reports gives strong evidence, that the initiative step for solid electrolyte interphase (SEI) formation is a cathodic, i.e. by reduction induced electro-polymerisation of the vinyl-group. It is concluded that this electro-polymerisation may also be a main reduction mechanism of other vinyl compounds such as vinylene carbonate (VC), vinylene acetate and others. #
Analytical and Bioanalytical Chemistry, 2004
Lithium-ion batteries operate beyond the thermodynamic stability of the aprotic organic electroly... more Lithium-ion batteries operate beyond the thermodynamic stability of the aprotic organic electrolyte used and electrolyte decomposition occurs at both electrodes. The electrolyte must therefore be composed in a way that its decomposition products form a film on the electrodes which stops the decomposition reactions but is still permeable to the Li(+) cations which are the charge carriers. At the graphite anode, this film is commonly referred to as a solid electrolyte interphase (SEI). Aprotic organic compounds containing vinylene groups can form an effective SEI on a graphitic anode. As examples, vinyl acetate (VA) and acrylonitrile (AN) have been investigated by in-situ Fourier transform infrared (FTIR) spectroscopy in a specially developed IR cell. The measurements focus on electrolyte decomposition and the mechanism of SEI formation in the presence of VA and AN. We conclude that cathodic reduction of the vinylene groups (i.e., via reduction of the double bond) in the electrolyte additives is the initiating and thus a most important step of the SEI-formation process, even in an electrolyte which contains only a few percent (i.e. electrolyte additive amounts) of the compound. The possibility of electropolymerization of the vinylene monomers in the battery electrolytes used is critically discussed on the basis of the IR data obtained.
Journal of Power Sources, 2006
The long-term formation kinetics of the solid electrolyte interphase (SEI) was studied on graphit... more The long-term formation kinetics of the solid electrolyte interphase (SEI) was studied on graphite electrodes in 1M LiClO4/PC with 5% acrylonitrile (AN) as electrolyte additive by electrochemical impedance spectroscopy at 1.0 and 0.5V versus Li/Li+, i.e. mainly outside the graphite intercalation region. To support the interpretation of the results, comparative experiments with Ni and Pt electrodes were performed at the