# Effect of Bottlebrush Particle Architecture on Their Efficiency as Protective Layers in Li-Metal Batteries

## TL;DR

This study explores how the structure of bottlebrush particles affects their performance as protective layers in lithium-metal batteries.

## Contribution

The paper identifies optimal structural parameters for bottlebrush particles to balance conductivity and mechanical strength in lithium-metal batteries.

## Key findings

- High grafting density and inorganic fraction improve mechanical strength but may increase polarization.
- Intermediate grafting density and molecular mass provide the best balance of conductivity and strength.
- Optimal parameters include a grafting density of 0.23 chains nm–2 and 10 wt% inorganic fraction.

## Abstract

Due to their impressive
energy density, lithium-metal
batteries have great potential to replace the widely used lithium-ion
batteries. However, some challenges, like dendrite growth and the
formation of “dead” lithium, still hamper their industrial
application to this day. Artificial solid electrolyte interfaces (aSEIs)
provide a protective coating on lithium electrodes to enforce uniform
lithium stripping/plating. Especially, poly­(ethylene glycol)-based
polymers are promising due to their high ionic conductivity, but a
challenge remains in their lack of mechanical strength. By grafting
these polymers from inorganic nanoparticles, such as silica, the high
ionic conductivity can be combined with the mechanical strength of
the nanoparticles. The physicochemical properties of these bottlebrush
particles (BBPs) are determined by the grafting density (GD), inorganic
fraction, and molecular mass of the grafted polymer chains. Each of
these parameters has a significant influence on the materials’
mechanical and conducting properties. In this work, each of these
parameters and their effect on performance as aSEIs for lithium-metal
anodes were studied. While high-molecular mass and grafting densities
with low inorganic fractions can increase ion conductivity, as well
as the mechanical strength of the material, unwanted elevated polarization
was observed. Conversely, low GD samples provided significant enhancement
of mechanical strength but reduced ionic conductivity. Overall, intermediate
GD of 0.23 chains nm–2, high inorganic fraction
of ca. 10 wt %, and intermediate molecular mass of ca. 100,000 g mol–1 provided the optimal balance for the tested BBPs
of ionic conductivity, mechanical properties to prevent dendrite formation,
as well as reduced polarization.