Ning Xu,Hebing Zhou,Youhao Liao,Guanjie Li,Mengqing Xu,Weishan Li
The rapid capacity fading of LiCoO 2 cathodes under high temperature limits its further development in high energy density of lithium ion batteries , caused by the unmatched liquid electrolyte that tends to decompose when the working potential exceeds 4.2 V (vs. Li + /Li). Gel polymer membrane blended with PEO (poly(ethylene oxide)) and P(VdF-HFP) (poly(vinylidene fluoride- co -hexafluoropropylene)) is used to enhance the oxidative stability of liquid electrolyte in the polymer matrix . In order to maximize the capacity of LiCoO 2 cathode, proper amount of SN (succinonitrile) that helps to construct a stable CEI (cathode electrolyte interface) film is added into the electrolyte. The SN-contained GPE (gel polymer electrolyte) has the highest oxidative decomposition potential of 5.2 V and the lowest interfacial resistance . At 55 °C, the LiCoO 2 /GPE/Li coin-cell keeps 82% of capacity after 350 cycles in 3.0 V ~ 4.45 V at 1 C rate, compared with that of 9% capacity retention using the polyethylene separator saturated with liquid electrolyte. The enhancement in the cyclic stability under elevated temperature attributes to the dual strategies: the GPE guarantees the better oxidative stability by suppressing the further oxidative decomposition of liquid electrolyte, while the high quality CEI film formed by the SN additive protects the structural integrity of LiCoO 2 cathode.
Liqin Xiong,Zheng Cheng,Guorong Hu,Yanbing Cao,Zhongdong Peng,Bin Zhang,Ke Du
High-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) emerges as an ideal cathode for high energy density lithium-ion batteries due to its 4.7 V operating voltage and low-cost manganese-rich composition. However, the severe interfacial degradation caused by transition metal dissolution and pervasive electrolyte decomposition compromises practical viability in commercial lithium-ion batteries, critically under elevated-temperature operation. To address this problem, we constructed a covalently anchored bis[3-(trimethoxysilyl)propyl]amine (BTPA) coating layer on the LNMO surface through atomic-scale grafting. The BTPA-coated LNMO confers exceptional cyclic stability and rate capability, representing a transformative advancement in cathode performance. At 50 °C, BTPA-coated LNMO cathode maintains 96.10 % capacity retention after 100 cycles at 1C, significantly outperforming pristine LNMO (58.92 % retention), while demonstrating exceptional rate capability with 109.42 mAh·g −1 delivered at 10C compared to 92.71 mAh·g −1 for the pristine LNMO. The synergistic suppression of Mn 3+ formation and parasitic reactions underpins unprecedented high-temperature cyclability, establishing a paradigm for extreme-condition energy storage.
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