(1. 遼寧工程技術(shù)大學(xué)材料科學(xué)與工程學(xué)院，阜新 123000；
2. 遼寧工程技術(shù)大學(xué)力學(xué)與工程學(xué)院，阜新 123000)
摘 要: 采用基于密度泛函的第一性原理，計(jì)算研究鋰離子電池石墨烯負(fù)極表面Li原子或團(tuán)聚體Lin(n＜10)的沉積行為，包括最低能量構(gòu)型、吸附能、差分密度電荷和態(tài)密度等性質(zhì)。結(jié)果表明：當(dāng)n≤2時(shí)，Li原子以分散的形式，優(yōu)先沉積在石墨烯碳六元環(huán)中心上方位置；隨著Li原子數(shù)的增加，當(dāng)n≥3時(shí)，Li原子優(yōu)先聚集，以團(tuán)聚體的形式沉積在石墨烯表面，在實(shí)際中有可能形成穩(wěn)定的Li4、Li7和Li9團(tuán)聚體。這表明石墨烯的最大儲(chǔ)鋰容量可能超過(guò)石墨，但容易形成鋰枝晶。電子結(jié)構(gòu)分析表明，Li原子或Lin團(tuán)聚體的電子轉(zhuǎn)移至臨近石墨烯的反鍵π軌道，Li原子的2s軌道和C原子的2p軌道出現(xiàn)明顯的雜化現(xiàn)象。隨著Li原子數(shù)n的增多，體系的費(fèi)米能級(jí)向石墨烯反鍵π軌道移動(dòng)，金屬性和電子導(dǎo)電性增強(qiáng)。Lin團(tuán)聚體底層的Li—Li鍵通常為離子鍵，最外層的Li—Li鍵通常為共價(jià)鍵；Lin團(tuán)聚體與石墨烯之間的Li—C鍵為具有部分共價(jià)鍵屬性的離子鍵，并且Li—C鍵強(qiáng)度隨著Li原子數(shù)量n的增多而逐漸減小。
關(guān)鍵字: 鋰離子電池；石墨烯；Lin團(tuán)聚體；第一性原理；沉積行為
（1. College of Materials Science and Engineering, Liaoning Technical University, Fuxin 123000;
2. School of Mechanics and Engineering, Liaoning Technical University, Fuxin 123000, China）
Abstract:Deposition behavior of Li atoms or aggregates Lin(n＜10) on graphene negative electrodes for lithium-ion batteries was investigated by the first principles calculations based on density functional theory, including the lowest energy configuration, adsorption energy, charge density difference and density of states. The results show that Li atom preferentially deposits above the center of the carbon six-membered ring of graphene in a dispersed form when n≤2. As the number of Li atoms increases, Li atoms preferentially aggregate to reunite and deposit on graphene when n≥3. It is possible to form Li4, Li7 and Li9 stable agglomerates in the charging process of the lithium ion battery, which indicates that the maximum lithium storage capacity of graphene may exceed that of graphite. However, the lithium dendrites will form easily. The electronic structure analysis shows that the electrons of Li atom or Lin aggregates transfer to the anti-bonded π orbital of graphene, and the 2s orbital of Li atom and the 2p orbital of C atom are obviously hybridized. The Fermi level of the system moves to the graphene anti-bond π orbital as the number of Li atoms n increases, which leads to the result that the metallicity and electronic conductivity increase. The Li—Li bond at the bottom of the Lin agglomerate is usually an ionic bond and the outermost Li—Li bond is usually a covalent bond. The Li—C bond between the Lin agglomerate and graphene is an ionic bond with partial covalent bond property and the strength of the Li—C bond gradually decreases as the number of Li atoms n increases.
Key words: lithium ion battery; graphene; Lin agglomerates; first-principles; deposition behavior
