石墨/Li（Ni1/3Co1/3Mn1/3）O2电池充放电过程中电极材料的XRD研究

利用XRD系统地研究了石墨/Li（Ni_1/3Co_1/3Mn_1/3）O₂ 18650型锂离子电池充放电过程中正负极活性材料的晶体结构和微结构的变化.已观测到，由于Li原子的脱嵌，使得LiMO₂点阵参数a缩小，c增大，微应变增大，衍射强度比I₁₀₄/I₁₀₁和I₀₁₂/I₁₀₁降低；此外，由于Li原子的嵌入，2H-石墨的点阵参数a和c，以及微应变ε和堆垛无序度P都增加.同时，讨论了活性材料Li（Ni_1/3Co_1/3Mn_1/3）O₂和石墨在电池充放电过程中的嵌脱锂的物理机理.在充电时，正极Li（Ni_1/3Co_1/3Mn_1/3）O₂中处于（000）位的Li原子优先脱离晶体点阵，继后才是位于（2/3 1/3 1/3）和（1/3 2/3 2/3）位的Li原子离开点阵.锂嵌入石墨，优先进入碳原子六方网格面间的间隙位置，当负极的堆垛无序度达到一定值后，3R相逐渐析出.当电池满充或过充时，在六方石墨中形成LiC₁₂和LiC₆相.放电时，与上述过程相反，但并非是完全可逆的.关键词：锂离子电池微结构X射线衍射嵌脱锂物理机理

XRD studies on the electrode materials in the charge-discharge process of a graphite/Li(Ni1/3Co1/3Mn1/3)O2 battery

Structure transformation and microstructure of the electrode active materials in a graphite / Li （Ni_1/3Co_1/3Mn_1/3）O₂ lithium ion battery during charge-discharge process have been studied by XRD. It is found that the lattice parameter of Li （Ni_1/3Co_1/3Mn_1/3）O₂, a and c, decrease and increase respectively. Its micro-strain ε and diffraction intensity ratio, I₁₀₄/I₁₀₁ and I₀₁₂/I₁₀₁, increases and decrease respectively, because Li atoms de-intercalate out of the crystal lattice of LiMO₂. Meanwhile, the lattice parameter, a and c, micro-strain ε and stacking disorder P of 2H-graphite all increase, becausing Li atoms to intercalate into 2H-graphite.During charge process, Li atoms occupying （000） sites may preferentially de-intercalate from LiMO₂ crystal lattice, and subsequently the Li atoms occupying （2/3 1/3 1/3）and（1/3 2/3 2/3）sites de-intercalate from LiMO₂. When intercalating into 2H-graphite, Li atoms preferentially occupy interstitial sites between C atom hexagonal net planes. When the stacking disorder degree reaches a given value, 3R-graphite phase may separate out gradually. When the battery has been fully charged or over charged, LiC₁₂ and LiC₆ phases can be formed. During discharge process, intercalation and de-intercalation behaviors of Li atoms are reversed. Li atoms may de-intercalate preferentially from interstitial sites of 2H-graphite and intercalate preferentially into （000） sites of LiMO₂ crystal lattice. But these processes are not fully reversible.