Enabling safer, ultralong lifespan all-solid-state Li-organic batteries

Highlights

• A novel high-performance composite solid polymer electrolyte is prepared.

• The CSPE can effectively inhibit the dissolution and shuttle of organic cathode.

• Solid Li-organic battery shows superior rate performance and ultralong lifespan.

• The remarkable safety is achieved under high temperature and abuse conditions.

Abstract

Organic cathode materials have attracted widespread attention due to their diverse structures, abundant raw materials, low cost, and eco-friendliness. However, their practical applications are restricted because of the poor cycling stability and lifespan owing to the dissolution and shuttle effect of the organic cathode in the liquid electrolyte. In this work, a novel all-solid-state Li-organic battery with ultralong lifespan is developed by using perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) as the organic cathode, composite solid polymer electrolyte (hybrid polymer-LiTFSI-LLZTO, HLL) as the electrolyte, and Li metal as the anode. The as-prepared HLL electrolyte exhibits high ionic conductivity (1.46 × 10^-4 S cm⁻¹ at 30 °C), superior thermal stability (~202 °C), outstanding electrode/electrolyte interfacial compatibility, and significant suppression to the dissolution/shuttle of PTCDA and the growth of Li dendrite. Ascribing to these advantages, the solid-state PTCDA|HLL|Li battery delivers a reversible capacity of 60 mAh g⁻¹ after 1000 cycles at a high current density of 500 mA g⁻¹, corresponding to an outstanding capacity retention of 91%. Moreover, the solid-state PTCDA|Li battery presents an elevated thermal stable window (178 °C) and less heat release (430 J g⁻¹) compared with the analogous battery using liquid electrolyte (151 °C and 486 J g⁻¹). Furthermore, the solid-state battery exhibits desirable flexibility and satisfactory safety under various abuse conditions (bending, cutting, and punching), demonstrating its outstanding safety in practical environments. This work offers a new pathway toward safer, longer lifespan solid-state Li-organic batteries.

Introduction

Lithium-ion batteries (LIBs) have been widely used in portable electronic devices and electric vehicles due to their outstanding performance such as high energy density, no memory effect and low self-discharge [1], [2]. The soaring demand for LIBs poses a significant challenge to inorganic metal oxide-based cathode materials (LiCoO₂, LiNi_1-x-yCo_xMn_yO₂, etc.), which are expensive, scarce in resources, and environmentally unfriendly. Therefore, organic cathode materials are considered as promising alternatives due to their abundant raw materials, low cost, and eco-friendliness [3], [4]. Unfortunately, most organic cathode materials suffer from dissolution and shuttle issues in conventional liquid electrolytes, resulting in rapid capacity decline and poor cycling stability, which hinders their further applications [5], [6].

Recently, many strategies have been developed, such as surface coating [7], [8], polymerization [9], [10], salts formation [11], [12], and introducing solid-state electrolytes [13], [14], [15], which can significantly alleviate the dissolution issue. Among them, the introduction of solid-state electrolytes into Li-organic batteries not only offers the possibility to fully address the dissolution issue of organic cathodes, but also shows promising prospects in terms of energy density, mechanical robustness, and thermal safety. However, so far, there are only a handful of studies have been reported about the all-solid-state Li-organic batteries. Moreover, their lifespan was limited in the range of 10–300 cycles due to the inferior electrode–electrolyte interfacial compatibility [16], [17], [18], [19]. For example, Li et al. combined polyethylene oxide (PEO)-based composite polymer electrolyte and the organic anthraquinone cathode, which showed a capacity retention of 60% after 100 cycles, while the capacity retention of the analogous battery using liquid electrolyte is only 28% after 20 cycles [18]. The solid-state Li-organic battery using Li₃PS₄ solid electrolyte and azobenzene organic cathode delivered a capacity of 83 mAh g⁻¹ after 120 cycles, corresponding to a capacity retention of 69%, which is much higher than that of the battery using liquid electrolyte (16% after 20 cycles) [19]. Despite these encouraging results, the cycling stability and lifespan of solid-state Li-organic batteries should be further improved for commercial applications. Therefore, it is of great significance to develop novel solid-state electrolytes with high ionic conductivity and excellent electrode–electrolyte interfacial compatibility to produce high energy density, long lifespan all-solid-state Li-organic batteries.

Among solid-state electrolytes, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based composite polymer electrolyte has attached extensive attention due to its high solubility in dispersing medium, good film formability, and excellent electrochemical stability [20]. However, the low ionic conductivity and lithium ion transference number hinder its further applications. Introducing another polymer into the PVDF-HFP matrix to produce hybrid polymers is an effective way to address these limitations. For instance, Sasikumar et al. prepared a hybrid polymer electrolyte by incorporating polyvinyl acetate into a PVDF-HFP/LiTFSI matrix, showing a high ionic conductivity of 1.1 × 10^-3 S cm⁻¹ [21]. By combining poly(ethylene carbonate) (PEC) with PVDF-HFP electrolyte, Zhao et al. fabricated a hybrid polymer electrolyte that shows enhanced electrochemical performance compared with the pristine PVDF-HFP-based electrolyte [22].

In this work, we developed a high-performance all-solid-state Li-organic battery comprising a perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) cathode, a Li metal anode, and a novel composite solid polymer electrolyte (hybrid polymer-LiTFSI-LLZO, HLL). The prepared HLL electrolyte performs high ionic conductivity (1.46 × 10^-4 S cm⁻¹ at 30 °C), wide voltage window (~4.6 V), outstanding mechanical modulus (137.1 MPa), significant thermal stability (~202 °C), and excellent electrode–electrolyte interfacial compatibility. Thanks to these advantages, the fabricated solid-state PTCDA|HLL|Li battery offers a high initial capacity of 122 mAh g⁻¹ and 79% capacity retention after 100 cycles at a current density of 50 mA g⁻¹. Furthermore, even at a high current density of 500 mA g⁻¹, a satisfactory reversible capacity of 60 mAh g⁻¹ was achieved after 1000 cycles, corresponding to a superior capacity retention of 91%. More importantly, the solid-state battery displays an elevated thermal stable window (178 °C) and less heat generation (430 J g⁻¹) compared with the analogous battery using liquid electrolyte (151 °C and 486 J g⁻¹). Moreover, the solid-state PTCDA|HLL|Li battery not only cycled safely at high temperature, but also showed remarkable safety under various abuse conditions (bending, cutting, and punching), demonstrating its outstanding safety in practical environments.