(1. 中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083；
2. 中南大學(xué) 深圳研究院 深圳高性能電池材料與器件工程研究中心，深圳 518057)
摘 要: 針對擴(kuò)散極化及其影響因素，以LiMn2O4/石墨鋰離子電池為研究對象，基于一維電化學(xué)模型開展了其放電過程中擴(kuò)散極化的數(shù)值仿真研究。結(jié)果表明：在放電過程中，正負(fù)電極均存在固、液相擴(kuò)散極化，且隨著放電過程的深入，固、液相擴(kuò)散極化均在增大。電極活性物質(zhì)顆粒粒徑對固相擴(kuò)散過程影響顯著，減小活性物質(zhì)顆粒粒徑能有效地降低固相擴(kuò)散極化。當(dāng)正、負(fù)極活性物質(zhì)顆粒粒徑分別由10和12 μm減小到5和6 μm，在1C放電 1 800 s時，顆粒表面和中心的鋰離子濃度差分別降低至原來的25.35%和25.07%；當(dāng)正、負(fù)極活性物質(zhì)顆粒分別由10和12 μm增加至20和24 μm時，顆粒表面和中心的鋰離子濃度差分別增加至原來的391.66%和266.96%。電極厚度是影響液相擴(kuò)散極化的一個主要因素，厚度的減小能夠縮短液相擴(kuò)散的路徑，從而減小電極的液相擴(kuò)散極化。當(dāng)正、負(fù)極電極厚度分別由90和60 μm增加至112.5和75 μm，在1C放電1 800 s時，厚度方向的最大鋰離子濃度差與平均濃度的比值相應(yīng)地由14.05%和1.71%增加至19.54%和2.61%；當(dāng)正、負(fù)極厚度分別由90和60 μm減小至67.5和45 μm時，厚度方向的最大鋰離子濃度差與平均濃度的比值分別由14.05%和1.71%減小至8.72%和0.98%。
關(guān)鍵字: 數(shù)值仿真；電化學(xué)模型；固相擴(kuò)散；液相擴(kuò)散；鋰離子電池
（1. School of Metallurgy Science and Engineering, Central South University, Changsha 410083, China;
2. Engineering Research Center of High Performance Battery Materials and Devices in Shenzhen,
Research Institute in Shenzhen, Central South University, Shenzhen 518057, China）
Abstract:Taking a LiMn2O4/graphite battery as the research object, the diffusion polarization and its influencing factors of the battery were studied by numerical simulation method based on the one-dimensional electrochemical model. The results show that both liquid phase and solid phase diffusion polarizations exist in the positive and negative electrodes, and diffusion polarization increase with the conducting of the discharge process. The particle size of active materials has a distinct impact on the solid phase diffusion polarization, reducing the active material particle sizes can reduce the solid phase diffusion polarization effectively. As the particle radius of active materials in positive and negative electrodes decrease from 10 and 12 μm to 5 and 6 μm, respectively, the lithium ion concentration differences at surface and center will drop by 25.35% and 25.07%, respectively, when it discharges at 1C for 1 800 s. When the particle radius of active materials in positive and negative electrodes increase from 10 and 12 μm to 20 and 24 μm, respectively, the lithium ion concentration differences at surface and center in positive and negative electrode rise by 391.66% and 266.96%, respectively. The electrode thickness is a major influence factor of the liquid phase diffusion polarization, decreasing it can decrease the liquid diffusion path and the liquid phase diffusion polarization. As the thicknesses of positive and negative electrode increase from 90 and 60 μm to 112.5 and 75 μm, respectively, the ratios of the largest lithium ion concentration difference and the average lithium ion concentration along the positive and negative thickness direction increase from 14.05% and 1.71% to 19.54% and 2.61%, respectively. And when the thicknesses of positive and negative electrode decrease from 90 and 60 μm to 67.5 and 45 μm, respectively, the ratios between the largest lithium ion concentration difference and the average lithium ion concentration along the positive and negative thickness direction decrease from 14.05% and 1.71% to 8.72% and 0.98%, respectively.
Key words: numerical simulation method; electrochemical model; solid phase diffusion; liquid phase diffusion; Li-ion battery
