New Insights on Graphite Anode Stability in Rechargeable Batteries: Li Ion Coordination Structures Prevail over Solid Electrolyte Interphases

Abstract

Graphite anodes are not stable in most noncarbonate solvents (e.g., ether, sulfoxide, sulfone) upon Li ion intercalation, known as an urgent issue in present Li ions and next-generation Li−S and Li−O 2 batteries for storage of Li ions within the anode for safety features. The solid electrolyte interphase (SEI) is commonly believed to be decisive for stabilizing the graphite anode. However, here we find that the solvation structure of the Li ions, determined by the electrolyte composition including lithium salts, solvents, and additives, plays a more dominant role than SEI in graphite anode stability. The Li ion intercalation desired for battery operation competes with the undesired Li + −solvent co-insertion, leading to graphite exfoliation. The increase in organic lithium salt LiN(SO 2 CF 3 ) 2 concentration or, more effectively, the addition of LiNO 3 lowers the interaction strength between Li + and solvents, suppressing the graphite exfoliation caused by Li + −solvent co-insertion. Our findings refresh the knowledge of the well-known SEI for graphite stability in metal ion batteries and also provide new guidelines for electrolyte systems to achieve reliable and safe Li−S full batteries.

Phase Inversion Strategy to Flexible Freestanding Electrode: Critical Coupling of Binders and Electrolytes for High Performance Li–S Battery

“…The initial capacity is 1042 mAh g −1 with the 75% utilization of sulfur and retains 658 mAh g −1 over 100 cycles (Figure d). Note that the full battery performance in this work is more improved than the previously reported highest performance of full‐cell using 5 m LiTFSI in 1,3‐dioxolane (DOL) electrolyte and that with sulfur‐carbon cathode . Those reported full lithium‐ion sulfur batteries suffered from fast capacity fade and unstable Coulombic efficiency, which could be ascribed to the inability of the electrode to suppress the shuttle effect.…”

Anode Interface Engineering and Architecture Design for High‐Performance Lithium–Sulfur Batteries

“…These complex and unstable SEI layers have been identified as a major obstacle to achieving high‐performance batteries. For example, a passivated film cannot effectively form on a graphite anode surface because of the intercalation of solvent molecules, resulting in an adverse effect on electrolyte performance . Although an SEI film can form on a Si anode surface, the SEI film continuously breaks and reforms due to the large volume change of Si anode during cycling, resulting in a thick surface layer and the loss of active materials.…”

“…Using DOL as a solvent and LiNO 3 as an additive can stabilize Li‐metal‐free anode surfaces for the following reasons: 1) The addition of LiNO 3 can hinder the co‐intercalation of Li ions with the electrolyte solvent, resulting in better graphite stability . 2) On the Si surface, LiNO 3 induces the polymerization of DOL to form Li 2 O and flexible polymeric R‐NO 2 species, which are essential compounds in the protective SEI layer (Figure e) . However, Li‐metal‐free anodes with protective SEI films still exhibit lower reversibility in ether‐based electrolytes than in carbonate‐based electrolytes, which adversely affects their electrochemical performance …”

“…2) On the Si surface, LiNO 3 induces the polymerization of DOL to form Li 2 O and flexible polymeric R‐NO 2 species, which are essential compounds in the protective SEI layer (Figure e) . However, Li‐metal‐free anodes with protective SEI films still exhibit lower reversibility in ether‐based electrolytes than in carbonate‐based electrolytes, which adversely affects their electrochemical performance …”

Metal–Organic Coordination Strategy for Obtaining Metal‐Decorated Mo‐Based Complexes: Multi‐dimensional Structural Evolution and High‐Rate Lithium‐Ion Battery Applications

“…These results demonstrate the advantages of 2D architectures and heteroatom doping for obtaining high performance. 340 mA hg À1 ) [48] for the same energyc apacity. Besides, the R ct of ac ycled nanopetal was measured as 28.1 W,c omparable to the value foraf resh nanopetal before cycling, furtherd emonstrating the structurals tability.…”