Cyclic Aminosilane‐Based Additive Ensuring Stable Electrode–Electrolyte Interfaces in Li‐Ion Batteries

Abstract

Ni‐rich cathodes are considered feasible candidates for high‐energy‐density Li‐ion batteries (LIBs). However, the structural degradation of Ni‐rich cathodes on the micro‐ and nanoscale leads to severe capacity fading, thereby impeding their practical use in LIBs. Here, it is reported that 3‐(trimethylsilyl)‐2‐oxazolidinone (TMS‐ON) as a multifunctional additive promotes the dissociation of LiPF6, prevents the hydrolysis of ion‐paired LiPF6 (which produces undesired acidic compounds including HF), and scavenges HF in the electrolyte. Further, the presence of 0.5 wt% TMS‐ON helps maintain a stable solid–electrolyte interphase (SEI) at Ni‐rich LiNi0.7Co0.15Mn0.15O2 (NCM) cathodes, thus mitigating the irreversible phase transformation from layered to rock‐salt structures and enabling the long‐term stability of the SEI at the graphite anode with low interfacial resistance. Notably, NCM/graphite full cells with TMS‐ON, which exhibit an excellent discharge capacity retention of 80.4%, deliver a discharge capacity of 154.7 mAh g−1 after 400 cycles at 45 °C.

Unanticipated Mechanism of the Trimethylsilyl Motif in Electrolyte Additives on Nickel-Rich Cathodes in Lithium-Ion Batteries

“…The solution was stirred at 25 °C for 24 h. The resulting solution was filtered and then analyzed by 31 P nuclear magnetic resonance (NMR) spectroscopy (400 MHz, Bruker Avance 3HD) with a tetrahydrofuran (THF)- d 8 NMR solvent. The cross-sectional samples for the observation of microcracking of the PC-NCM811 particles were prepared by an ion-milling system (HITACHI IM4000) . Moreover, the phase transition of the PC-NCM811 particle was observed by STEM (JEM-2100Fm JEOL).…”

“…Sectional samples for micro-cracking observation of NCM811 cathode were processed by the ion milling method (Hitachi IM4000). [36] Furthermore, the structural change of NCM811 was detected by STEM (JEM-2100Fm JEOL). Electronic energy loss spectrophotometric measurements were made to examine the transformation in the cathode structure with the valence state of Mn, Ni and Co. VSP-300 Galvanostats and potentistat were used to measure total cell impedances.…”

Demystifying the Lattice Oxygen Redox in Layered Oxide Cathode Materials of Lithium-Ion Batteries

“…However, the doping of Ni only slightly alters the bulk chemistry of the LCO cathode materials. It mainly presents surface effects, such as mitigating the formation of CEI and initiating phase transformation in the near-surface region, and those were usually ignored in the past. − First, the O 2 -type LCO cathode materials render high specific capacity and Li + and electronic conductivities; therefore, it is not clear why the transition of bulk phase inevitably causes capacity fading . Second, the strategy of surface coating has been usually employed to ameliorate the electrochemical property of the LCO cathode materials.…”

Improving the Cyclic Stability of LiNi0.5Mn1.5O4 at High Cutoff Voltage by Using Pyrene as a Novel Additive

“…[ 8 ] Compared with surface modification, electrolyte additive is a more economical and effective method to improve the interface stability of LiNi 0.5 Mn 1.5 O 4 cathode. [ 9 ] At present, different film‐forming additives including trifluoromethyl sulfide (PTS), [9d] 1,1‐sulfonyldiimidazole (SDM), [ 10 ] allyloxytrimethylsilsilane (AMSL), [ 11 ] tris(pentafluorophenyl)silane (TPFPS), [ 12 ] (pentafluorophenyl)diphenylphosphine (PFPDPP), [ 13 ] p‐toluenesulfonyl isocyanate (PTSI), [ 14 ] tris(pentafluorophenyl)borane (TPFPB), [ 15 ] 3‐(trimethylsilyl)‐2‐oxazolidinone (TMS‐ON), [ 16 ] and so on have been used to improve the interface stability of the LiNi 0.5 Mn 1.5 O 4 , but it finds that some film‐forming additives also increase the interface resistance, which is harmful to the rate performance of the cells. [ 10,17 ] To compare with aforementioned film‐forming additives, using a monomer of a conductive polymer as a film‐forming additive is a more effective method to improve the interface stability because it can not only effectively protect the surface of cathode, but also improve the rate performance of cells by its excellent conductivity.…”