Stress Relief Principle of Micron‐Sized Anodes with Large Volume Variation for Practical High‐Energy Lithium‐Ion Batteries

• Published in: Advanced functional materials 2020-10, Vol.30 (40), p.n/a
• Main Authors: Lee, Yoonkwang, Lee, Taeyong, Hong, Jaehyung, Sung, Jaekyung, Kim, Namhyung, Son, Yeonguk, Ma, Jiyoung, Kim, Sung Youb, Cho, Jaephil
• Format: Article
• Language: English
• Subjects: Anodes; anodes design; Cycles; Density; Electrodes; Finite element method; Gravimetry; Lithium-ion batteries; Materials science; Mathematical analysis; Si/C composites; stress evolution; Structural integrity
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202004841

Practical applications of high gravimetric and volumetric capacity anodes for next‐generation lithium‐ion batteries have attracted unprecedented attentions, but still faced challenges by their severe volume changes, rendering low Coulombic efficiency and fast capacity fading. Nano and void‐engineering strategies had been extensively applied to overcome the large volume fluctuations causing the continuous irreversible reactions upon cycling, but they showed intrinsic limit in fabrication of practical electrode condition. Achieving high electrode density is particularly paramount factor in terms of the commercial feasibility, which is mainly dominated by the true density and tapping density of active material. Herein, based on finite element method calculation, micron‐sized double passivation layered Si/C design is introduced with restrictive lithiation state, which can withstand the induced stress from Li insertion upon repeated cycling. Such design takes advantage in structural integrity during long‐term cycling even at high gravimetric capacity (1400 mAh g−1). In 1 Ah pouch‐type full‐cell evaluation with high mass loading and electrode density (≈3.75 mAh cm−2 and ≈1.65 g cm−3), it demonstrates superior cycle stability without rapid capacity drop during 800 cycles. As a novel approach, stress relief design is introduced, which distributes silicon within the framework with rational material composition. In this work, micron‐sized and high tap density Si/C composite anode is presented to meet the industrial requirements. By the materials design, decrease in active Si caused by the matrix composite demonstrates superior cyclability, realizing structural reversibility with reduced volume change.