# Cu-Enhanced Bottlebrush Composite Polymer Electrolytes for Superior Mechanical and Electrochemical Performance

## TL;DR

This paper introduces a new type of polymer electrolyte that improves the performance and safety of lithium metal batteries.

## Contribution

The novel contribution is the development of Cu-enhanced bottlebrush composite polymer electrolytes with superior mechanical and electrochemical properties.

## Key findings

- Cu(TFSI)2 incorporation increases ionic conductivity by 3-fold compared to unmodified electrolytes.
- Symmetric Li|Li cells showed stable cycling for over 500 hours with low overpotential.
- The electrolyte works well with both inorganic and organic cathodes, showing high capacity and extended cycle life.

## Abstract

The development of safe and high-performance electrolytes
is essential
to realize the full potential of lithium metal batteries (LMBs) for
next-generation energy storage. In this study, we report the design
and synthesis of composite polymer electrolytes (CPEs) based on polyoxanorbornene
bottlebrush polymers (BPs) with poly­(ethylene oxide) (PEO) side chains.
These unique bottlebrush architectures, synthesized via ring-opening
metathesis polymerization, enable precise control over mechanical
properties while maintaining a high ionic conductivity. The incorporation
of copper bis­(trifluoromethanesulfonyl)­imide (Cu­(TFSI)2) into the polymer matrix enhances ionic conductivity by disrupting
PEO crystallinity and modifying the local lithium coordination environment.
Electrochemical impedance spectroscopy revealed that the optimized
CPE with 2 wt % Cu­(TFSI)2 exhibited a 3-fold increase in
ionic conductivity compared to BPs without Cu salt incorporation.
Symmetric Li|Li cells demonstrated stable cycling with low overpotential
for over 500 h, highlighting the electrolyte’s excellent lithium
metal compatibility and dendrite suppression capabilities. Full-cell
tests with LiFePO4 (LFP) and perylenetetracarboxylic dianhydride
(PTCDA) cathodes further confirmed the electrolyte’s versatility,
delivering high capacities, superior rate performance, and extended
cycle life compared to conventional polymer electrolytes. This work
demonstrates that Cu-modified bottlebrush polymer electrolytes are
a promising platform for enabling high-performance, solid-state LMBs,
with broad applicability to both inorganic and organic cathodes.