# Composition‐Controlled Cathode Protective Layer via Powder‐Atomic Layer Deposition for All‐Solid‐State Batteries

## TL;DR

This paper shows how controlling the composition of a protective layer on battery cathodes improves battery performance and stability.

## Contribution

The study introduces composition-controlled protective layers as a new design parameter for cathode interface engineering in solid-state batteries.

## Key findings

- Lithium zirconium oxide layers with varying compositions were grown on LiNi0.8Co0.1Mn0.1O2 using atomic layer deposition.
- Coated cathode materials showed improved initial efficiency and capacity retention compared to uncoated ones.
- Composition directly affects ionic and electronic conductivities, impacting electrochemical performance.

## Abstract

Controlling the ionic and electronic conductivities of the protective layers on cathode active materials (CAMs) is critical for interface stabilization with sulfide‐based solid electrolytes in all‐solid‐state batteries (ASSBs). In this study, lithium zirconium oxide layers with varying compositions are grown on LiNi0.8Co0.1Mn0.1O2 using an O3‐based atomic layer deposition process. The ionic conductivity reaches 2.20 × 10−7 S cm−1 at 25 °C, and the electronic conductivity ranges from 10−10 to 10−7 S cm−1 depending on composition. These composition‐dependent transport properties directly affect electrochemical performance, leading to a 4.5% difference in initial Coulombic efficiency and a 37% difference in long‐term retention. Compared to their uncoated counterparts, the coated CAMs exhibited 6.7% and 43% increases in initial efficiency and capacity retention of the cells, respectively. This study establishes a quantitative correlation between the protective layer's composition and battery performance, emphasizing that composition control is a key strategy for interfacial engineering in sulfide‐based ASSBs.

Composition control of the LiZrO protective layer via atomic layer deposition modulates its ionic and electronic conductivities, directly affecting interfacial stability and electrochemical performances of the sulfide‐based all‐solid‐state batteries. This study establishes the composition of the protective layer as an essential design axis for cathode interface engineering, beyond conventional parameters such as film thickness and coating method.