# Hydroxyethyl Cellulose as Water‐Soluble Co‐Binder for High Mass Loading LiNi0.5Mn1.5O4 Lithium‐Ion Battery Cathodes

## TL;DR

This paper introduces a new water-soluble binder for making high-performance, fluorine-free lithium-ion battery cathodes.

## Contribution

The novel use of hydroxyethyl cellulose as a co-binder with guar gum enables high mass loading electrodes without fluorine.

## Key findings

- HEC and GG combination improves mechanical and electrochemical properties of LNMO electrodes.
- Cells achieved 2.2 mAh cm−2 areal capacity and 82% capacity retention after 200 cycles.
- The system supports fluorine-free, water-processed high-voltage cathodes.

## Abstract

Combining high‐voltage cobalt‐free LiNi0.5Mn1.5O4 (LNMO) with fluorine‐free water‐soluble binders holds the promise of achieving more sustainable and environment‐friendly lithium‐ion batteries (LIBs). However, achieving high mass loading electrodes with lithium transition metal oxides as the active material remains a challenge. Herein, 2‐hydroxyethyl cellulose (HEC) is proposed as suitable binding agent, crosslinked via citric acid with guar gum (GG). The incorporation of HEC is pivotal for realizing a homogeneous dispersion of the electrode components, which is essential for the mechanical properties. Hence, the advantageous combination of co‐crosslinked HEC and GG allows for the simultaneous optimization of electrochemical and mechanical properties, enabling the preparation of well performing high mass loading LNMO electrodes with about 15 mg cm−2, providing a capacity retention as good as reference electrodes employing polyvinylidene difluoride as binder. Coupling these electrodes with graphite‐based negative electrodes enables lithium‐ion cells with an areal capacity of ~2.2 mAh cm−2 and a capacity retention of 82 % after 200 cycles, rendering this system promising for the realization of water‐processed, F‐free, high‐voltage cathodes.

2‐Hydroxyethyl cellulose is introduced as water‐soluble co‐binder to achieve high electrode mass loadings for fluorine‐free LiNi0.5Mn1.5O4 cathodes. In combination with guar gum, the electrochemical and mechanical properties are simultaneously optimized, enabling graphite∥LiNi0.5Mn1.5O4 cells with an areal capacity of 2.2 mAh cm‐2 and a capacity retention of 82% after 200 cycles.