Ren Wen-Feng, Le Jia-Bo, Li Jun-Tao, Hu Yi-Yang, Pan Si-Yu, Deng Li, Zhou Yao, Huang Ling, Sun Shi-Gang
State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Liaoning Key Laboratory of Lignocellulose Chemistry and BioMaterials, College of Light Industry and Chemical Engineering, Dalian Polytechnic University, Dalian 116034, China.
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):639-649. doi: 10.1021/acsami.0c18743. Epub 2020 Dec 23.
Binders play a crucial role in the development of silicon (Si) anodes for lithium-ion batteries with high specific energy. The large volume change of Si (∼300%) during repeated discharge and charge processes causes the destruction and separation of electrode materials from the copper (Cu) current collector and ultimately results in poor cycling performance. In the present study, we design and prepare hydrogen-bonding cross-linked thiourea-based polymeric binders (denoted CMC--SN) in consideration of their excellent binding interaction with the Cu current collector and low cost as well. The CMC--SN binders are formed through thermopolymerization of chain-type carboxymethylcellulose sodium (CMC) with thiourea (SN) in the drying process of Si electrode disks. A tight and physical interlocked layer between the CMC--SN binder and Cu current collector is derived from a dendritic nonstoichiometric copper sulfide (CuS) layer on the interface and enhances the binding of electrode materials with the Cu current collector. When applying the CMC--SN binders to micro- (∼3 μm) (μSi) and nano- (∼50 nm) (nSi) Si particles, the Si anodes exhibit high initial Coulomb efficiency (91.5% for μSi and 83.2% for nSi) and excellent cyclability (1121 mA h g for μSi after 140 cycles and 1083 mA h g for nSi after 300 cycles). The results demonstrate that the CMC--SN binders together with a physical interlocked layer have significantly improved the electrochemical performance of Si anodes through strong binding forces with the current collector to maintain electrode integrity and avoid electric contact loss.
粘结剂在高比能锂离子电池硅（Si）负极的开发中起着至关重要的作用。在反复充放电过程中，硅（约300%）的大幅体积变化会导致电极材料与铜（Cu）集流体发生破坏和分离，最终导致循环性能不佳。在本研究中，我们设计并制备了基于氢键交联硫脲的聚合物粘结剂（表示为CMC-SN），考虑到它们与铜集流体具有优异的结合相互作用且成本低廉。CMC-SN粘结剂是在硅电极盘干燥过程中，通过链状羧甲基纤维素钠（CMC）与硫脲（SN）的热聚合形成的。CMC-SN粘结剂与铜集流体之间紧密的物理互锁层源自界面上的树枝状非化学计量硫化铜（CuS）层，并增强了电极材料与铜集流体的结合。当将CMC-SN粘结剂应用于微米级（约3μm）（μSi）和纳米级（约50nm）（nSi）的硅颗粒时，硅负极表现出高初始库仑效率（μSi为91.5%，nSi为83.2%）和优异的循环性能（μSi在140次循环后为1121 mA h/g，nSi在300次循环后为1083 mA h/g）。结果表明，CMC-SN粘结剂与物理互锁层通过与集流体的强结合力显著改善了硅负极的电化学性能，以保持电极完整性并避免电接触损失。
