Self-Healing Binder for High-Voltage Batteries

Abstract

Lithium-ion batteries are core components of flexible electronic devices. However, deformation types, such as impinging, bending, stretching, folding, and twisting, can cause internal cracks and, eventually, damage these batteries. The cracks separate the active particles from the conductive particles and the binder, as well as the electrode from the collector. Self-healing binders can alleviate this mechanical damage and improve the stress response of active material particles during high rates of charging and discharging of these batteries and the operation at a high voltage, thereby enhancing their cycle performance. In the present study, a thermoplastic intrinsic self-healing polymer (TISP) binder is proposed. The TISP is obtained by polymerization of butanediol (2,3-BDO), propylene glycol (1,3-PDO), succinic acid (SuA), sebacic acid (SeA), and iconic acid (IA). The hydroxyl and ester groups in its structure can form diverse bonds including the hydrogen and ion-dipole with active particles and the current collector, thereby producing elevated adhesion. Its properties, including a low glass transition temperature (−60 °C), amorphous structure, and low cross-link density, improve the mobility of polymer chains at 40 °C, and this facilitates structural recovery and the maintenance of strong adhesions. Owing to its higher occupied molecular orbital (HOMO) level than the electrolyte solvent, the TISP is likely oxidized before the main component of the electrolyte during charging. This decomposition produces a chemical passivation interphase on the cathode which reduces side reactions of LiCoO2 and the electrolyte under high-voltage conditions. Tests reveal that a LiCoO2 electrode battery using the TISP as a binder retains 162.4 mAh g–1 after 349 cycles at 4.5 V, and this represents an 86.5% capacity retention. In addition, heating (40 °C, 1 h) of a scratch-damaged electrode can recover a specific capacity of 156.6 mAh g–1 after 349 cycles at 4.5 V. Relative to a battery without any mechanical scratch, this capacity recovery represents approximately 96%, and this demonstrates the importance of the TISP to the high-voltage damaged electrode.

Towards Efficient Polymeric Binders for Transition Metal Oxides‐based Li‐ion Battery Cathodes

“…reported a thermoplastic intrinsically self‐healing polymer (TISP), in which the hydroxyl and ester groups form multiple bonds containing the ion‐dipole and hydrogen with cathode particles and the Al collector, thus resulting in enhanced adhesion (Figure 7a–b). [64] The scratch‐damaged TISP‐based LCO cathode displayed nearly 96 % capacity recovery relative to the intact battery after heating at 40 °C for 1 h, demonstrating fast self‐healing ability for applications (Figure 7c). In addition, TISP is liable to oxidize at the surface of LCO during charging, producing a chemical passivation layer that decreases parasitic reactions under high‐voltage conditions.…”

“…Reproduced with permission. [64] Copyright 2018, American Chemical Society. (d) Schematic diagram of multifunctional protective effect of PR-co-PAA for NMC622 cathode: i) maintain the electrode structural integrity; ii) suppress interfacial side reactions.…”

“… The surface morphology a) and the surfaces of SEM images b) of TISP‐LCO before and after heating at 40 °C for 1 h. c) Rate performance of TISP‐LCO batteries after scratching and self‐healing process. Reproduced with permission [64] . Copyright 2018, American Chemical Society.…”

Achievements, challenges, and perspectives in the design of polymer binders for advanced lithium-ion batteries

“…Hu, Xiang and coworkers prepared a multicomponent polyester binder for high-voltage batteries via the polycondensation of a mixture of alcohols (2,3-butanediol and 1,3-propylene glycol) with aliphatic dicarboxylic acids (succinic, sebacic, and iconic acids). 448 Based on the structure of the used components, the polymer was mainly linear, while its backbone was flexible, thus providing the strength of covalent bonds and conformational dynamics. Owing to the multicomponent structure, the chain regularity was destroyed, preventing crystallization and forming an amorphous material with a very low T g of ∼−60 °C.…”

Synthesis of Aminopolyolefins with Tunable Hydrophilicity and Chain Flexibility for Application as Binders in Aqueous Rechargeable Batteries

“…The enhanced performance was proposed to be due to the H-bonding ability imparted by the ureidopyrimidinone-functionalized poly­(acrylic acid) binder . The Xiang and Hu groups have demonstrated the importance of H-bonding, and the resulting self-healing, in binders to elevate the adhesion of active materials to the current collector and offer high capacity retention in high-voltage LIBs operated at high temperatures and a large number of cycles …”