Thin Film Silicon-Based Intermetallic Systems for Lithium Ion Battery Application

The demand for high energy lithium-ion battery systems has increased tremendously in the last few decades.[1] The most common anode material nowadays is graphitic carbon due to its long cycle life, low cost and abundant availability. Its drawback comes within a rather low specific capacity of 372 mAh/g. [2] To meet the requirements of next generation lithium ion batteries, new anode systems with a higher theoretical capacity are needed. A promising candidate to replace graphite is silicon, as it offers a capacity exceeding 3500 mAh/g at room temperature, while still being environmentally friendly and easily available. The main challenge before implementing Si as anode material is its enormous volume expansion upon lithiation causing the electrode material to collapse, thus resulting in a short cycle life. [3]

One approach to address this issue is the use of a stabilizing matrix, in which silicon is embedded. Therefore, several different alloy or intermetallic phase systems consisting of Cr, Ni, Ti or Mg in combination with Si are investigated on their use as a stabilizing matrix for Si based anode systems. Thin films of the binary systems are obtained via a co-magnetron sputter deposition process, in which we are able to steer the composition of the system by varying different parameters like the applied RF power during deposition. The as prepared thin films are electrochemically characterized by galvanostatic cycling as well as cyclic voltammetry. Embedding silicon in different alloys or intermetallic phases drastically changes the electrochemical performance, increasing capacity retention and cycle life of the anode system in lithium ion battery application.

 References:

 [1] J.B. Goodenough, Accounts Chem Res, (2012).

[2] M. Winter, Chem Unserer Zeit, 33 (1999) 320.

[3] U. Kasavajjula, C.S. Wang, A.J. Appleby, J Power Sources, 163 (2007) 1003-1039.