SEI-Component Formation on Nano-Silicon in Rechargeable Lithium-Based Batteries Using Modified Ether-Based Electrolytes

TONY JAUMANN; JUAN BALACH; MARKUS KLOSE; STEFFEN OSWALD; ULRIKE LANGKLOTZ; HOLGER ALTHUES; JÜRGEN ECKERT; LARS GIEBELER

Encuentro; 228th ECS Meeting; 2015

Lithium-ion (Li-ion) batteries are currently the first choice as energy storage for many applications (i.e. portable electronic devices) owing to its high energy density and good cycle life. In order to extend its field of application (i.e. hybrid electric vehicles) and satisfy the consumer demands, new cell chemistry with higher potential energy density has to be developed. The lithium-sulfur (Li-S) battery is a promising candidate as the next generation energy storage system because of theoretically five times higher energy density than state-of-the-art Li-ion batteries and the abundant availability of sulfur as active material. However, several issues hampered its commercialization up to now. Among others, the metallic lithium anode in such batteries is unfavorable due to depletion of electrolyte, uncontrollable dendrite formation, self-discharge through reduction of polysulfides and safety issues.Herein, we present an advanced silicon anode and its favorably application in Li-S batteries. The anode material is composed of low-sized silicon nanoparticles inside of a porous carbon scaffold obtained through a convenient and economical synthesis procedure. The silicon electrode was assembled with a standard sulfur cathode through a facile pre-lithiation and was investigated in our group. The conventional Li-S battery typically fails after few cycles, if the electrolyte is reduced to reasonable amounts owing to a depletion of the organic solvents on highly reactive lithium. By using the novel lithiated silicon anode we can considerably extend the cycle life and build an even anode/cathode balanced battery. Furthermore, we observed a reduced shuttle phenomenon as well as self-discharge of polysulfides at the anode. In order to rationalize our observations, we studied the surface phenomenon and structural changes of the silicon anode through ex-situ XPS measurements and in-situ diffraction experiments at synchrotron lines. In particular, the influence of polysulfides on the solid-electrolyte-interface (SEI) of silicon will be showed in our poster.