# Water-Scavenging Suspended Mediator in Electrolytes for Silicon-Based Lithium-Ion Batteries with High-Nickel Cathode

## TL;DR

A new electrolyte additive captures water to prevent battery degradation, enabling stable high-performance lithium-ion batteries with high-nickel cathodes.

## Contribution

A boroxine-linked COF is introduced as a water-scavenging suspended mediator to suppress hydrolysis and electrode corrosion in lithium batteries.

## Key findings

- A boroxine-linked COF effectively captures H2O, suppressing PF6− hydrolysis and HF formation.
- The water-scavenging electrolyte enabled a Li-metal battery with a high-nickel cathode to retain 73% capacity after 500 cycles at 1 C.
- The suspension strategy enabled stable cycling of a silicon-based battery with a high-nickel cathode over 500 cycles at 10 C.

## Abstract

Trace amounts of H2O are inevitably introduced during lithium battery manufacturing processes, which induces the hydrolysis of LiPF6, leading to HF formation, which triggers a cascade of deleterious reactions that degrade the solid electrolyte interphase (SEI) and corrode electrode materials. In this work, a water-scavenging electrolyte was constructed by employing a boroxine-linked covalent organic framework (COF) as the suspended phase. The ring-opening reaction of the boroxine ring units in COFs can effectively capture H2O, thereby suppressing the hydrolysis of PF6− and mitigating electrode corrosion caused by HF. Consequently, a Li-metal battery with a high-nickel cathode retained 73% of its initial capacity after 500 cycles at 1 C, and a silicon-based lithium-ion battery with a high-nickel cathode sustained stable cycling over 500 cycles at a high rate of 10 C. This suspension strategy, leveraging a boroxine-linked COF with dual H2O-scavenging capability, offers a scalable and versatile platform for electrolyte engineering toward practical next-generation lithium batteries.