# Chemomechanical Origin of Morphological Disparity in Lithium Metal Electrodeposition

## TL;DR

This study explains why lithium deposits in batteries can have different shapes, showing that the initial layer on the copper surface controls the growth patterns.

## Contribution

The paper identifies the chemomechanical origin of lithium deposition morphology disparity through SEI layer composition.

## Key findings

- Solvent-derived SEI promotes whisker-like lithium deposits.
- Salt-derived SEI leads to particle-like lithium deposits.
- SEI layer composition directly influences lithium morphology.

## Abstract

The morphology of electrochemically deposited lithium (Li) critically governs the cycling stability and safety of Li metal batteries, yet the underlying controlling factors remain poorly understood. Even within the same coin cell, Li deposits can exhibit strikingly different morphologies, for example, sparse whiskers coexisting with particle‐like deposits, indicting strong local variations in growth conditions. By combining cryogenic transmission electron microscopy with phase‐field modeling, here we identify the root cause of this disparity. We reveal that the morphological divergence originates from the variations in structure and chemical composition of the initial SEI layer formed on the copper (Cu) substrate. Solvent‐derived organic SEI favors whisker growth, whereas salt‐derived SEI promotes particle formation. This study establishes a direct mechanistic link between SEI chemomechanical properties and Li morphology, providing design principles for tailoring SEI layers to control Li deposition.

Selective dissociation of either solvent or salt on copper current collector induced different solid electrolyte interphase (SEI) layers. The solvent derived organic SEI favors formation of Li whisker, while salt derived SEI favors formation of Li particle, revealing the root cause of Li morphology disparity within the same cell.