Non-Electroconductive Polymer Coating on Graphite Mitigating Electrochemical Degradation of PTFE for a Dry-Processed Lithium-Ion Battery Anode.

Polytetrafluoroethylene (PTFE)-based dry process for lithium-ion batteries is gaining attention as a battery manufacturing scheme can be simplified with drastically reducing environmental damage. However, the electrochemical instability of PTFE in a reducing environment has hampered the realization of the high-performance dry-processed anode. In this study, we present a non-electroconductive and highly ionic-conductive polymer coating on graphite to mitigate the electrochemical degradation of the PTFE binder and minimize the coating resistance. Poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) coatings on the anode material effectively inhibit the electron transfer from graphite to PTFE, thereby alleviating the PTFE breakdown. The graphite polymer coatings improved initial Coulombic efficiencies of full cells from 67.2% (bare) to 79.1% (PEO) and 77.8% (P(VDF-TrFE-CFE)) and increased initial discharge capacity from 157.7 mAh g(NCM)-1 (bare) to 185.1 mAh g(NCM)-1 (PEO) and 182.5 mAh g(NCM)-1 (P(VDF-TrFE-CFE)) in the full cells. These outcomes demonstrate that PTFE degradation in the anode can be surmounted by adjusting the electron transfer to the PTFE.

Dual-Seed Strategy for High-Performance Anode-Less All-Solid-State Batteries.

Interest in all-solid-state batteries (ASSBs), particularly the anode-less type, has grown alongside the expansion of the electric vehicle (EV) market, because they offer advantages in terms of their energy density and manufacturing cost. However, in most anode-less ASSBs, the anode is covered by a protective layer to ensure stable lithium (Li) deposition, thus requiring high temperatures to ensure adequate Li ion diffusion kinetics through the protective layer. This study proposes a dual-seed protective layer consisting of silver (Ag) and zinc oxide (ZnO) nanoparticles for sulfide-based anode-less ASSBs. This dual-seed-based protective layer not only facilitates Li diffusion via multiple lithiation pathways over a wide range of potentials, but also enhances the mechanical stability of the anode interface through the in situ formation of a Ag-Zn alloy with high ductility. The capacity retention during full-cell evaluation is 80.8% for 100 cycles when cycled at 1 mA cm-2 with 3 mAh cm-2 at room temperature. The dual-seed approach provides useful insights into the design of multi-seed concepts in which, from a mechanochemical perspective, various lithiophilic materials synergistically impact upon the anode-less interface.