Scientists at the Fraunhofer FEP institute have developed a non-toxic and efficient manufacturing process for porous silicon layers for use as lithium-ion battery anodes.
The vacuum coating process for the syntheses of porous silicon thin film deposits silicon and zinc simultaneously on metal substrates. The breakthrough was discovered during project PoSiBat— an investigation into whether highly porous silicon layers had the potential to boost the energy density of lithium-ion batteries.
Although silicon, as a replacement of graphite promises a 10-25% improvement in a cell’s energy density, cycling leads to a change in its volume, which leads to a rapid mechanical and electrochemical destruction of the material compound and finally to cell failure.
Dr. Stefan Saager, from Fraunhofer FEP, told BEST Battery Briefing: “The expansion during charging was not stopped, rather the pores provide space for stress relaxation.
“We checked the battery performance by assembling coated copper substrates in argon atmosphere in a half cell configuration and by galvanostatic charging and discharging.
“With the novel silicon anode’s excellent electrochemical performance, particularly high capacities of ≥3000 mAh/g, reasonable coulombic efficiencies of ≥90% in the initial cycle and comparably high cycle life >150 cycles were demonstrated.
“The utilisation of thin metal foils is also conceivable but it was not tested yet. Therefore there are some more development tasks for commercialisation. We hope to reach last challenges in collaboration with industry partners.”
The scientists are now looking forward to collaborating with battery manufacturers to transfer the results into high-performance products. They are open to cooperation.
The results of the project will be presented at the Thin Film Technology for Energy Systems workshop at V2019 and at the Fraunhofer FEP booth No. 22 (October 8 –10, 2019, in Dresden, Germany).