Fluid-enhanced surface diffusion controls intraparticle phase transformations
- Fluid-enhanced surface diffusion controls intraparticle phase transformations
- 홍지현; 이양 리; 헌그루 첸; 임기필; 임종우; 디미트리오스 프래게다키스; 피터 아티아; 이상철; 노만 진; 요제 모스콘; 지쉔 구안; 윌리엄 젠트; 유영상; 미란 가베르첵; 사이풀 이슬람; 마틴 바잔트; 윌리엄 츄; Haitao D. Deng
- 에너지소재; 에너지저장; 소재고도분석; 리튬이차전지
- Issue Date
- Nature materials
- VOL 17-922
- Phase transformations driven by compositional change require mass flux across a phase boundary. In some anisotropic solids, however, the phase boundary moves along a non-conductive crystallographic direction. One such material is LiXFePO4, an electrode for lithium-ion batteries. With poor bulk ionic transport along the direction of phase separation, it is unclear how lithium migrates during phase transformations. Here, we show that lithium migrates along the solid/liquid interface without leaving the particle, whereby charge carriers do not cross the double layer. X-ray diffraction and microscopy experiments as well as ab initio molecular dynamics simulations show that organic solvent and water molecules promote this surface ion diffusion, effectively rendering LiXFePO4 a three-dimensional lithium-ion conductor. Phase-field simulations capture the effects of surface diffusion on phase transformation. Lowering surface diffusivity is crucial towards supressing phase separation. This work establishes fluid-enhanced surface diffusion as a key dial for tuning phase transformation in anisotropic solids.
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