Tailoring Silicon Composite Anodes with Li⁺-Containing Organic Ionic Plastic Crystals for Solid-State Batteries

Abstract

Silicon is one of the highest-capacity anode active materials and, therefore, its use in solid-state batteries (SSBs) is expected to provide both high energy density and safety. Although the creation of solid-state Si electrodes via a scalable method is important from the perspective of battery production, its effect on electrochemical performance has yet to be clarified for the electrodes containing Li+-doped organic ionic plastic crystals (OIPCs) as solid electrolytes. Here, we made various Si−OIPC composite electrodes using four electrode-preparation methods and measured their electrochemical performances to decipher the method−structure−property relationship for high-performing SSBs. The Si−OIPC composite electrode containing 50 mol% LiFSI in N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ([C2mpyr][FSI]) showed the highest initial Coulombic efficiency and cyclability. Three out of four methods provided the Si−Li0.50[C2mpyr]0.50[FSI] electrodes with relatively large capacity retentions that were close to that of the Si electrode in a liquid electrolyte. Elemental analysis for the electrode cross-sections resolved the homogeneous distribution of Li0.50[C2mpyr]0.50[FSI], except for the one made by the drop-casting method, suggesting that three methods can establish the long-range ion-conduction network in the electrode to improve the electrochemical stability of Si during cycling. This study clarifies the importance of the OIPC-incorporation method in fabricating highly functional OIPC-based electrodes for SSBs.

New Plastic Crystal Composite Electrodes Employing Delocalized Transition Metal Salts for Low-Cost, High-Safety All-Solid-State Salt Batteries

“…This electrolyte was chosen in this work, although in theory any solid-state electrolyte could be employed, including polymer, polymer gel, and ceramic or glassy electrolytes. We have also recently demonstrated the use of this OIPC as a readily processable binder within graphite and silicon anodes, paving the way for a host of new soft-solid electrodes for solid-state batteries. Importantly, Fe(BF 4 ) 2 ·6H 2 O is employed for the first time as an active material, together with the OIPC and graphene conductive additive, to form a new type of electrode (denoted Fe-PBL-G and Fe-PBN-G) for metal (Li and Na) batteries.…”

Modeling Rate Dependent Volume Change in Porous Electrodes in Lithium-Ion Batteries

“…6,7 As battery pack designs for electric vehicles increase in energy to meet range requirements and mitigate range anxiety 8 for consumers, higher energy density materials 9 such as silicon [10][11][12][13][14][15][16][17][18] containing materials have come into focus. Silicon and other high-capacity anode materials undergo significant volume change [19][20][21][22][23] during lithiation, [24][25][26] which can ultimately impact the performance of the battery pack and electric vehicle due to the engineering changes that must be made to account for the silicon volume change. Additionally, a desire exists to increase the speed 27 at which battery cell designs move from concept to production reality.…”