锂电制造业的先进电极加工技术

【综述背景与内容简介】

由于电动汽车的普及化，当前锂电池的需求产能正在急剧增长，预计将在2030年达到2500 GWh。当前，锂电制造业的支柱工艺为湿法电极加工， 该技术不仅能耗高、成本高（水系与非水系溶剂均有高沸点，另外非水系溶剂由于高毒性需要进行额外的回收处理），而且其生产的电极在电化学性能方面也尚有不足（如热烘干过程中的粘合剂迁移会导致因材料分部不均造成电化学性能和机械性能降低），因此该工艺无法很好地适配于当前发展趋势。为了更好地满足锂电池的产量缺口，锂电制造业需要开发采用新一代电极制备工艺以实现高性能电极的加工处理并达到绿色、高产、低成本的生产技术要求。

【创新成果】

近日，位于美国的阿贡国家实验室、橡树岭国家实验室、凯斯西储大学联合在国际知名期刊Nature Reviews Clean Technology 上发表了题为“Advanced Electrode Processing for Lithium-Ion Battery Manufacturing”的最新综述。该综述系统性地介绍了不同先进电极加工技术的工艺（包括湿法、干法、3D打印、辐照固化），深入地讨论了实际生产应用和回收领域的现状，并指出当前各锂电池电极加工技术的发展仍然不足，优势与挑战并存，强调科研人员要着眼于工业化发展，进一步深化各技术方向研发。该文回顾了锂电池电极产业加工发展，为促进锂电池制造业的技术革新提出了战略性的新思维。

【综述亮点】

1、传统的锂离子电池电极加工主要依赖于湿法加工，既耗时又耗能。所得电极电化学性能有限。

2、与传统湿法工艺相比，先进电极加工技术不仅更经济实惠而且能有着更低能耗和更环保的特点。另外利用laser ablation、co-extrusion、freeze casting (ice templating)、additive manufacturing来改进电极结构从而提高锂离子扩散动力学效率，但生产成本会有相应的提高。

3、干法电极加工技术已经展现出划时代的作用。它不仅可简化电极制造流程而且可以降低制造成本（约～11.5%）和能耗（>46%）。其中Maxwell型工艺作为目前最先进成熟的工艺正在工业界内逐渐取代湿法加工。

4、辐照固化电极加工技术具有最高的电极制备能力，而3D打印电极加工技术则可以制造出不同几何形状和结构的电极。

【图文解读】

Fig. 1: Electrode processing techniques.

Electrode processing techniques usually comprise three main steps: mixing (panels 1), electrode fabrication (panels 2) and calendering (panels 3). a, Conventional slurry-based processing. b, Dry processing. c, Radiation curing processing. d, 3D-printing processing.

Fig. 2: Modified electrodes manufactured by conventional slurry-based processing.

Conventional slurry-based processed electrodes with various modifications. a, Conventional slurry-based processing with a slot-die coater. b–d, Grid (panel b), line (panel c) and hole (panel d) patterns from laser ablation. e, Electrodes with ridges (regular coating) and valleys (thinner or no coating) from co-extrusion.

Fig. 3: Properties and performance of dry-processed electrodes.

Dry-processed electrode morphological properties affect their electrochemical performance. a, Tortuosity comparison between conventional electrodes and dry-processed electrodes at comparable electrode porosity, thickness and active material loading. b, Material distribution in conventional (left) and dry-processed electrodes (right). c, Cross-sectional scanning electron microscopy image of a Maxwell-type graphite dry-processed electrode. d, Improved cyclic performance of dry-processed lithium nickel manganese cobalt oxide (LNMO) electrodes. e, Electrochemical performance of a lithium-ion battery full cell, incorporating a graphite anode with (NM75/TE-Graphite cell 1 and cell 2) and without (NM75/E-Graphite cell 1 and cell 2) a polymer-based protective coating. Dry processing exhibits various advantages for manufacturing and can deliver electrodes with enhanced electrochemical performance. C, carbon; F, fluorine.

Fig. 4: Dry processing methods.

Mechanism of various dry processing methods. a, Ball milling-based dry mixing. b, Double-blade blender-based dry mixing. c, Maxwell type. d, Hot pressing and melting extrusion. e, Dry spraying deposition.

Fig. 5: Beam curing electrode processing.

Radiation curing processing working principles. a, Mechanism for ultraviolet (UV) curing processing. b, Size of lithium-ion battery electrode processing equipment for beam curing processing (blue) and conventional wet processing (red).

Fig. 6: 3D-priting electrode processing.

3D-printed electrodes have different structural features. a, Microgrid. b, Digit. c, Line. d, Cross-sectional view of the line structure. e, Spiral. f, Hierarchical. g, Fibre. h, Flexible direct ink writing processed electrode. i, Stereolithography printed and pyrolysed hard carbon electrode for sodium-ion batteries. j, Template-assisted electrodeposition porous electrode.

Table 1: Comparison of electrode manufacturing technologies.

【总结与展望】

由于人类社会对锂电池日益增长的需求，锂电池制造业需要在电极加工技术方面进行技术升级革新来取代有着诸多不足的传统湿法电机加工工艺。作为干法电极加工技术的代表，Maxwell型工艺以高实用性已经在锂电批量化工业生产方面拔得头筹，与此同时该技术也在固态电极和固态电解质的加工制备方面初露头角。辐照固化电极加工技术展现出极高的电极制备能力也在商业化方面有了小规模展示。3D打印电极加工技术因其可以制造多样几何形状和结构的能力正处于学术研究探索阶段。另外综述也对人工智能/机器学习技术和先进电极回收领域提出建设性的讨论与建议，强调了两者在促进未来锂电池制造业升级革新的作用。

转载自：材料人