Regulating the solvation chemistry of non-flammable high voltage electrolyte through salt-solvent ratio modulation

Mingyang Xin; Zhenhua Liu; Yuting Shi; Dan Li; Yanan Li; Xinming Zhang; Xi Chen; Silin Chen; Hao Sun; Haiming Xie; Yulong Liu

doi:10.1016/j.jcis.2023.03.046

Regulating the solvation chemistry of non-flammable high voltage electrolyte through salt-solvent ratio modulation

J Colloid Interface Sci. 2023 Jul 15:642:820-828. doi: 10.1016/j.jcis.2023.03.046. Epub 2023 Mar 24.

Authors

Mingyang Xin¹, Zhenhua Liu¹, Yuting Shi¹, Dan Li¹, Yanan Li¹, Xinming Zhang², Xi Chen², Silin Chen¹, Hao Sun³, Haiming Xie⁴, Yulong Liu⁵

Affiliations

¹ National & Local United Engineering Laboratory for Power Battery, Department of Chemistry, Northeast Normal University, Changchun 130024, China.
² Department of Materials Science and Engineering, University of California, Davis 95616, CA, United States.
³ National & Local United Engineering Laboratory for Power Battery, Department of Chemistry, Northeast Normal University, Changchun 130024, China. Electronic address: sunh600@nenu.edu.cn.
⁴ National & Local United Engineering Laboratory for Power Battery, Department of Chemistry, Northeast Normal University, Changchun 130024, China. Electronic address: xiehm136@nenu.edu.cn.
⁵ National & Local United Engineering Laboratory for Power Battery, Department of Chemistry, Northeast Normal University, Changchun 130024, China. Electronic address: liuyl290@nenu.edu.cn.

PMID: 37060648
DOI: 10.1016/j.jcis.2023.03.046

Abstract

Boosting the energy density and safety issue of lithium-ion batteries has become ever more important to satisfy the diverse applications such as energy storage and mobile electronic devices. Herein, we present a new high voltage polyether-based electrolyte (HVPEE) by solvation structure design that can endure high-voltage operations and also possess non-flammable features. Especially, HVPEEs show better compatibility and stability with electrode than conventional electrolyte. We find that the solvent separated ion pair (SSIP) and contact ion pair (CIP) dominate the ion-solvent structure of HVPEEs, rather than the free solvent and ions. In this way, the oxidative decomposition of HVPEE on the cathode interface can be suppressed significantly due to the reduced highest occupied molecular orbital of SSIP complex structure than that of free TFSI^-. As a result, the oxidation voltage can achieve as high as 5.35 V when the ether group/Li is optimized at 10/1 in the HVPEE, enabling the LiFePO₄//Li full cells deliver a capacity of 165 mA h g^-1 with a capacity retention of 98 % after 200 cycles. Moreover, when the cut-off voltage is 4.5 V, the discharge capacity of the LiNi_0.6Mn_0.2Co_0.2O₂//Li full cell can reach 170 mA h g^-1.

Keywords: Electrolyte; High-voltage; Molecular dynamics simulation; Solvation structure.