Construction of highly stable and fast kinetic interfacial films on the electrodes of graphite//LiNi0.5Mn1.5O4 cells by introducing a novel additive of 2-thiophene boric acid (2-TPBA)

• Published in: Journal of power sources Vol. 564; p. 232848
• Main Authors: Zhou, Kuan, Quan, Lijiao, Zhou, Hebing, Che, Yanxia, Li, Xiaoqing, Chen, Qiurong, Li, Weishan, Xu, Mengqing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2023
• Subjects: Electrolyte additive; High voltage; Interfacial film; LiNi0.5Mn1.5O4; Lithium-ion batteries; Interfacial film; Lithium-ion batteries; LiNi0.5Mn1.5O4; Electrolyte additive; High voltage
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2023.232848

A novel additive, 2-thiophene boric acid (2-TPBA), is investigated as a bifunctional surface film forming additive for both anode and cathode. By adding 1.0 wt% of 2-TPBA additive to the electrolyte (1.0 M LiPF6 in Ethylene carbonate (EC)/Diethyl carbonate (DEC)/Ethyl methyl carbonate (EMC) = 3/2/5, wt.%), the capacity retention of Li//LiNi0.5Mn1.5O4 and Li//graphite cells is significantly improved, specifically, from 37% to 93% after 200 cycles, and 31.9%–91.9% at 0.5C after 150 cycles, respectively. In addition, the cycling performance of graphite//LiNi0.5Mn1.5O4 full cell at 4.8 V is significantly improved from 48.7% to 70% after 160 cycles. The reaction mechanism of this additive is investigated using a combination of electrochemical methods, ex-situ spectroscopic characterization techniques and computational calculations. The improved performance results from the sacrificial reduction on the graphite anode and electron-polymerization of the 2-TPBA additive on the LiNi0.5Mn1.5O4 cathode surface to generate a stable and conductive surface film. S-based polymers and lithium fluorinated borate corresponding to the oxidation products of 2-TPBA additive are the main cathode electrolyte interphase (CEI) components on the LiNi0.5Mn1.5O4 cathode surface; while lithium thiophene borate is considered as the solid electrolyte interphase (SEI) component on graphite anode surface in the additive containing electrolyte. •2-thiophene boric acid is proposed as an additive for Gr.//LiNi0.5Mn1.5O4 cell.•Low impedance with fast kinetic SEI film and stable CEI is formed.•Cycling performance of Gr.//LiNi0.5Mn1.5O4 cell at 4.8 V is significantly improved.