Lithium Polyacrylate (LiPAA) as an Advanced Binder and a Passivating Agent for High-Voltage Li-Ion Batteries

Intensive studies of an advanced energy material are reported and lithium polyacrylate (LiPAA) is proven to be a surprisingly unique, multifunctional binder for high-voltage Li-ion batteries. The absence of effective passivation at the interface of high-voltage cathodes in Li-ion batteries may negatively affect their electrochemical performance, due to detrimental phenomena such as electrolyte solution oxidation and dissolution of transition metal cations. A strategy is introduced to build a stable cathode-electrolyte solution interphase for LiNi_0.5Mn_1.5O₄ (LNMO) spinel high-voltage cathodes during the electrode fabrication process by simply using LiPAA as the cathode binder. LiPAA is a superb binder due to unique adhesion, cohesion, and wetting properties. It forms a uniform thin passivating film on LNMO and conducting carbon particles in composite cathodes and also compensates Li-ion loss in full Li-ion batteries by acting as an extra Li source. It is shown that these positive roles of LiPAA lead to a significant improvement in the electrochemical performance (e.g., cycle life, cell impedance, and rate capability) of LNMO/graphite battery prototypes, compared with that obtained using traditional polyvinylidene fluoride (PVdF) binder for LNMO cathodes. In addition, replacing PVdF with LiPAA binder for LNMO cathodes offers better adhesion, lower cost, and clear environmental advantages. Multiple positive functions of lithium polyacrylate (LiPAA) binder are found for high-voltage Li-ion batteries. The LiPAA binder acts as a stable cathode-electrolyte solution interphase (CEI) and provides extra Li ions, which significantly improves electrochemical performance. Compared with traditional polyvinylidene fluoride binder, LiPAA offers better adhesion, lower cost, and clear environmental advantages.