A Dry‐Processed Al₂O₃/LiAlO₂ Coating for Stabilizing the Cathode/Electrolyte Interface in High‐Ni NCM‐Based All‐Solid‐State Batteries

Abstract

Due to their high theoretical energy densities and superior safety, thiophosphate‐based all‐solid‐state batteries (ASSBs) are considered as promising power source for electric vehicles. However, for large‐scale industrial applications, interfacial degradation between high‐voltage cathode active materials (CAMs) and solid‐state electrolytes (SSEs) needs to be overcome with a simple, cost‐effective solution. Surface coatings, which prevent the direct physical contact between CAM and SSE and in turn stabilize the interface, are considered as promising approach to solve this issue. In this work, an Al2O3/LiAlO2 coating for Li(Ni0.70Co0.15Mn0.15)O2 (NCM) is tested for ASSBs. The coating is obtained from a recently developed dry coating process followed by post‐annealing at 600 °C. Structural characterization reveals that the heat treatment results in the formation of a dense Al2O3/LiAlO2 coating layer. Electrochemical evaluations confirm that the annealing‐induced structural changes are beneficial for ASSB. Cells containing Al2O3/LiAlO2‐coated NCM show a significant improvement of the rate capability and long‐term cycling performance compared to those assembled from Al2O3‐coated and uncoated cathodes. Moreover, electrochemical impedance spectroscopy analysis shows a decreased cell impedance after cycling indicating a reduced interfacial degradation for the Al2O3/LiAlO2‐coated electrode. The results highlight a promising low‐cost and scalable CAM coating process, enabling large‐scale cathode coating for next‐generation ASSBs.

High‐Performance All‐Solid‐State Batteries Enabled by Intimate Interfacial Contact Between the Cathode and Sulfide‐Based Solid Electrolytes

“…On the other hand, ASSBs employing NCM@LPSCl operating at stack pressure of 3 MPa shows a comparable initial specific capacity to that of the cell operating at stack pressure of 20 MPa due to the enhanced microstructure of NCM@LPSCl. For comparison, the electrochemical performances of the electrode employing the NCM cathode materials for application in ASSBs are summarized in Table S3 (Supporting Information) 5, [32][33][34][35][36][37][38] . It is hard to compare fairly the electrochemical properties due to the different operation conditions, such as operating temperature, applied stack pressure, anode material, and electrode compositions.…”

Recent Developments in the Field of Sulfide Ceramic Solid‐State Electrolytes

“…[ 167 ] It was demonstrated [ 179 ] that Li 3 B 11 O 18 interlayer (less than 10 nm thick) efficiently protected the <LiNi 0.5 Co 0.2 Mn 0.3 O 2 /L 3 PS 4 > interface from degradation on cycling and markedly improved cycle performance of the <LiNi 0.5 Co 0.2 Mn 0.3 O 2 |L 3 PS 4 |graphite> cell. The cycle performance of the <NCM|Li 6 PS 5 Cl|In‐Li> cell was increased by coating the LiNi 0.70 Co 0.15 Mn 0.15 (NCM701515) CAM with Li 4 Ti 5 O 12 interlayer [ 180 ] ; the cycle performance of the <Li(Ni 0.70 Co 0.15 Mn 0.15 )O 2 |Li 6 PS 5 Cl|In–Li> cell was improved by coating the CAM with Al 2 O 3 –LiAlO 2 shell, [ 181 ] and the cycle performance of the <Li[(Ni 0.9 Co 0.05 Mn 0.05)0.8 Co 0.2 ]O 2 |Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 |Li–In> cell was improved by coating the CAM with Al 2 O 3 –LiAlO 2 shell (≈3 nm thick). [ 182 ] It was demonstrated that <In|Li 7 P 2 S 8 I|LiNi 0.6 Co 0.2 Mn 0.2 O 2 > cell cycle life may be improved by the CAM coating with NiCo 2 S 4 nano particles; while this coating has a high electronic conductivity, [ 183 ] it efficiently prevents mutual diffusion of CAM and SSE ions.…”

Insights into interfacial chemistry of Ni-rich cathodes and sulphide-based electrolytes in all-solid-state lithium batteries

“…The thio-LISICON b-Li 3 PS 4 has been used as a SSE in Ni-rich ASSLBs. [115][116][117][118][119][120] Undoubtedly, electrochemical parasitic reactions occur at electrode/electrolyte interfaces without protection. For example, ASSLBs composed of NCM622/b-Li 3 PS 4 and side reactions that occurred at the interface upon cycling were studied.…”

“…A series of coating materials have been constructed for Ni-rich cathodes, including Li + -conducting coating layers ( e.g. LiNbO 3 , 114,155–158 Li 2 ZrO 3 , 119,159,160 Li 4 Ti 5 O 12 , 161–163 LiAlO 2 , 118,164 Li 2 MoO 4 , 165 Li 3 PO 4 , 166 LiTaO 3 , 129 Li 3 B 11 O 18 , 109 LiPON, 167 LiNb 0.5 Ta 0.5 O 3 , 131,168,169 Li 0.35 La 0.55 TiO 3 , 125 Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , 170 Li 0.35 La 0.5 Sr 0.05 TiO 3 , 171 Li 2 CO 3 –LiNbO 3 , 115 Li 2 CO 3 –Li 2 ZrO 3 172 and LiInO 2 –LiI 173 ), binary oxides ( e.g. Al 2 O 3 , 164 ZrO 2 , 174 HfO 2 175 and TiO 2 176 ) and carbon-based materials.…”