Facile Fabrication of Ethoxy-Functional Polysiloxane Wrapped LiNi_0.6Co_0.2Mn_0.2O₂ Cathode with Improved Cycling Performance for Rechargeable Li-Ion Battery

Abstract

Dealing with the water molecule on the surface of LiNi0.6Co0.2Mn0.2O2 (NCM) cathode and hydrogen fluoride in the electrolyte is one of the most difficult challenges in Li-ion battery research. In this paper, the surface polymerization of tetraethyl orthosilicate (TEOS) on NCM to generate ethoxy-functional polysiloxane (EPS) wrapped NCM (E-NCM) cathode under mild conditions and without any additions is utilized to solve this intractable problem. The differential scanning calorimetry, transmission electron microscopy, and X-ray photoelectron spectroscopy results show that the formed amorphous coating can provide a protective shell to improve the NCM thermal stability, suppress the thickening of the solid electrolyte interphase (SEI) layer, and scavenge HF in the electrolyte. The E-NCM composite with 2 mol % EPS delivers a high discharge capacity retention of 84.9% after 100 cycles at a 1 C discharge rate in the 2.8-4.3 V potential range at 55 °C. Moreover, electrochemical impedance spectroscopy measurements reveal that the EPS coating could alleviate the impedance rise during cycling especially at an elevated temperature. Therefore, the fabricated E-NCM cathode with long-term cycling and thermal stability is a promising candidate for use in a high-energy Li-ion battery.

Suppressing Nickel Dissolution in Ni‐rich Layered Oxide Cathodes Using NiF2 as Electrolyte Additive

“…A large number of secondary particles cracked and even pulverized (Figure a‐b), which confirms the structure of pristine was visibly destroyed on account of the dissolution of TMs . Furthermore, large cracks and pulverization of particles lead more fresh active sites to interact with electrolyte, generating more TMs dissolution . However, the surface morphology and structure of 100‐NiF 2 cathode are well preserved (Figure c–d ) , which means that NiF 2 can protect the cathode from corroding of electrolyte.…”

“…[37,38] Furthermore, large cracks and pulverization of particles lead more fresh active sites to interact with electrolyte, generating more TMs dissolution. [5,39] However, the surface morphology and structure of 100-NiF 2 cathode are well preserved (Figure 6c-d), which means that NiF 2 can protect the cathode from corroding of electrolyte. On the one hand, the suppression of TMs dissolution reduces the loss of active cathode materials, [40] restraining the capacity attenuation.…”

“…[2][3][4] However, layered Ni-rich materials still suffer from the serious dissolution of transition metals (TMs) of cathode and oxidation decomposition of electrolyte. [5][6][7] Both of these two intricate problems lead to capacity degradation. Particularly, the dissolution of transition metals also brings about the structural degradation of the Ni-rich cathode materials.…”

Origin of Performance Differences of Nickel‐Rich LiNi0.9Mn0.1O2 Cathode Materials Synthesized in Oxygen and Air

“…[8,9] In reality, different synthesis conditions, such as different atmospheres, have significant effects on surface, structure, and performance of NRLC, which is still not satisfactory. [10][11][12][13] Until now, many measures are taken to improve the performance of NRLC such as metal ions doping and surface coating. Doping of sodium improves the rate capability and the capacity retention of LiNi 0.8 Co 0.15 Al 0.05 by suppressing the hexagonal to hexagonal (H2/H3) phase transition to alleviate the particle pulverization.…”

LiNixCoyMnzO2 cathode materials for lithium (-ion) batteries

“…Through time-resolved X-ray diffraction & mass spectrometry (TR-XRD/MS), Bak et al [39] revealed the same phase transformation upon heating the charged electrode. Taken together, the deterioration of chemical and structural stability of cathode material will be accelerated, leading to continuous capacity decay and thus inferior electrochemical performances [40,41]. , and olivine compounds with three-dimensional pathways (i.e., LiFePO4).…”