Engineering A Boron‐Rich Interphase with Nonflammable Electrolyte toward Stable Li||NCM811 Cells Under Elevated Temperature

Abstract

Despite the high energy of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode, it still suffers serious decay due to the continuous solvents decomposition and unstable cathode electrolyte interphase (CEI) layers, especially under high temperatures. The intense exothermic reaction between delithiated NCM811 and flammable organic solvents, on the other hand, pushes the batteries to their safety limit. Herein, we tackle these two issues via engineering the electrolytes, i.e., utilizing salts with higher HOMO levels and nonflammable solvents with lower HOMO levels, to reduce the massive decomposition of solvents on the cathode side and improve battery safety under elevated temperatures. Consequently, a thin and boron‐rich CEI was generated on the surface of NCM811, which effectively inhibited the side reactions and particle cracks, thus improving the cycling stability and safety. Deviated from the highly concentrated electrolytes which heavily relies on the usage of massive salts, our electrolyte recipe could introduce a robust inorganic‐rich CEI but use much less salt (i.e., dilute electrolyte), and thus, offer an encouraging alternative towards practical applications. As such, by adopting the proposed electrolyte, the NCM811 cathode exhibits a high‐capacity retention of 81.2% after 950 cycles at 25°C and 75% after 300 cycles at 55°C. This work provides a universal electrolyte design strategy for designing stable and safe high‐temperature electrolytes for the NCM811 cathode.This article is protected by copyright. All rights reserved

Precycling Strategy in Suitable Voltage to Improve the Stability of Interfacial Film and Suppress the Decline of LiNi0.6Mn0.2Co0.2O2 Cathode at Elevated Temperatures

“…Consequently, there is a significant rise in impedance . In the RF process, the escalation in the proportion of inorganic components containing B on the electrode surface contributes to a reduced impedance, thereby mitigating capacity degradation . The abundance of B-containing substances is substantiated by the XPS characterization results (Figure b).…”

“…44 In the RF process, the escalation in the proportion of inorganic components containing B on the electrode surface contributes to a reduced impedance, thereby mitigating capacity degradation. 45 The abundance of Bcontaining substances is substantiated by the XPS characterization results (Figure 5b). Conversely, the R CEI and R ct values for NF exhibit a more rapid increase, which is attributed to the decomposition of electrolyte components on the electrode surface during high-temperature cycling, indicating a more pronounced thickening of the CEI.…”

Anion‐modulated Ion Conductor with Chain Conformational Transformation for stabilizing Interfacial Phase of High‐Voltage Lithium Metal Batteries

“…First, distinguishing from a single intermediate phase, the AMIC | electrode intermediate phase components are heterogeneous, including inorganic salts (F‐salts, B‐salts, and Li 2 O, etc.) near the lithium metal [25,26] and polycarbonate anion near the SPE side. Secondly, the presence of polyanions (Li‐ion mobility number close to 1) [27,28] can maintain the uniformity of the lithium ions electrodeposition process and the viscoelasticity of the polymer chains can further maintain the volume changes of the electrode due to charging and discharging and thus maintain the stability of the interfacial phase structure, [29,30] i.e., dynamic stability.…”

Anion‐modulated Ion Conductor with Chain Conformational Transformation for stabilizing Interfacial Phase of High‐Voltage Lithium Metal Batteries

“…First, distinguishing from a single intermediate phase, the AMIC j electrode intermediate phase components are heterogeneous, including inorganic salts (F-salts, B-salts, and Li 2 O, etc.) near the lithium metal [25,26] and polycarbonate anion near the SPE side. Secondly, the presence of polyanions (Li-ion mobility number close to 1) [27,28] can maintain the uniformity of the lithium ions electrodeposition process and the viscoelasticity of the polymer chains can further maintain the volume changes of the electrode due to charging and discharging and thus maintain the stability of the interfacial phase structure, [29,30] i.e., dynamic stability.…”