钠电池极片的辊压工艺是什么？

What is the calendering process of electrodes for sodium-ion batteries?

辊压是烘干疏松极片的致密化工序，利用高精度双辊设备恒定压力碾压涂层，精准调控极片压实密度，平衡电芯体积能量密度与电化学循环性能。涂布烘干后的涂层孔隙率过高、粉体松散堆积，单位体积活性物质占比低，体积能量密度不足；辊压挤压粉体间隙缩小涂层厚度，提升单位体积储电量。工艺核心管控辊缝间隙、碾压压力、卷材走速三大参数，保证整卷极片压实密度均匀统一。辊压压力存在临界平衡值：压力过小压实不足，体积能量偏低；压力过大极片微孔完全闭合，电解液无法渗入内部储钠位点，离子传输受阻，充放电极化严重，循环快速衰减。辊压同步优化活性颗粒接触，降低极片本体接触电阻，提升电芯倍率放电能力，辊压后极片才能进入分切工序，压实密度是区分储能、动力电芯极片核心工艺指标。

Calendering is a densification procedure for loose dried electrodes. High-precision double rollers apply constant pressure to roll coatings and precisely control electrode compaction density, balancing cell volumetric energy density and electrochemical cycling performance. Coatings after coating and drying have excessive porosity and loose powder accumulation with low proportion of active materials per unit volume and insufficient volumetric energy density. Calendering compresses powder gaps to thin coatings and raise energy storage capacity per unit volume. Three core controlled parameters are roller gap, rolling pressure and strip speed to guarantee uniform compaction density across the whole electrode roll. There exists a critical equilibrium value for rolling pressure: insufficient pressure leads to inadequate compaction and low volumetric energy density; excessive pressure fully closes electrode micropores, blocking electrolyte infiltration into internal sodium storage sites, hindering ion transport, causing severe polarization and rapid capacity fading during cycling. Calendering simultaneously optimizes contact between active particles and reduces intrinsic electrode contact resistance to improve cell rate discharge capability. Electrodes can only enter the slitting procedure after calendering, and compaction density is the core process indicator distinguishing energy storage and power cell electrodes.