Driven by increasing demands for battery energy density from electronic devices, the development of higher-voltage electrolytes compatible with high-voltage LiNixCoyMn(1-x-y)O2 (NCM) cathodes and Li anodes has become an urgent necessity. Traditional organic liquid electrolytes are prone to uncontrollable side reactions with the highly reactive lithium metal anode, leading to continuous electrolyte decomposition, lithium dendrite growth, and irreversible capacity loss. Moreover, the volatility, flammability, and leakage risks of these liquid electrolytes pose severe safety concerns, thereby restricting their applicability in large-scale LMB systems. Consequently, future research needs to enhance electrolyte performance while further optimizing safety to promote the practical application of high-energy-density batteries.
Recently, a research team led by Yongsheng Chen at Nankai University achieved a significant breakthrough by developing a novel in-situ fabricated gel polymer electrolyte (GPE) with a localized high-concentration solvation structure (LHCE-GPE), which exhibited superior oxidation stability up to 4.95 V and high ionic conductivity of 2.8 mS cm−1 at room temperature. This innovative LHCE-GPE enables practical solid-state 18650 cylindrical lithium metal batteries to operate at 4.7 V, achieving a remarkable energy density of up to 250 Wh kg−1. Furthermore, when the cut-off voltage is increased to 4.8 V, the LHCE-GPE-based Li||Li1.2Ni0.13Co0.13Mn0.54O2 (LNCMO) cells can stably cycle for 150 cycles at 0.5 C with a high specific capacity of 248 mAh g−1. The unique solvation structure of LHCE-GPE within the polymer matrix not only enhances electrode–electrolyte interfacial stability and suppresses lithium dendrite growth but also ensures excellent performance across a wide temperature range and robust safety during rigorous mechanical abuse tests.
The synthesis of LHCE-GPE involved in-situ polymerization of a homogeneous precursor solution consisting of triethylene glycol dimethacrylate (TEGDMA) as the monomer and tailored LHCE-structured plasticizer at 60 ℃ within an assembled cell. The customized solvation structure facilitates the formation of an inorganic-rich interphase layer that effectively inhibits growth of lithium dendrite and maintains the stability of the cathode structure under high voltage.
In practical applications, LHCE-GPE has enabled solid-state 18650 cylindrical lithium metal batteries to achieve high energy densities of 250–283 Wh kg−1 at high voltages of 4.6 and 4.7 V. Moreover, LHCE-GPE has demonstrated extraordinary cycling stability, with Li||LiNi0.8Co0.1Mn0.1O2 cells achieving a remarkable cycling stability over 1000 cycles at 4.5 V and extended up to 2000 cycles at 4.3 V. These results represent among the highest levels performances reported for polymer-based LMBs under similar conditions. Additionally, the polymer electrolyte with a localized high-concentration solvation structure has achieved compatibility with various cathodes (LiNi0.6Co0.2Mn0.2O2, LiCoO2, LiFePO4), scalable preparation processes, and outstanding safety features, highlighting its significant potential in high-performance practical LMBs.
Furthermore, LHCE-GPE has shown exceptional safety characteristics, exhibiting neither electrolyte leakage nor combustion during rigorous nail-penetration tests. This represents a significant improvement compared to traditional liquid electrolytes, which typically exhibit violent combustion or explosion under comparable conditions. Even at a low temperature of −15°C, LHCE-GPE maintains high ionic conductivity and stable cycling performance.
The advancement made by this study constitutes an important step towards realizing high-energy, high-safety LMBs for future industrial applications. Therefore, the concept of designing polymer electrolytes with localized high-concentration structures provides a highly promising pathway for high-voltage, high-performance, and high-safety practical solid-state LMBs, thereby promoting their integration into diverse energy storage applications.
The authors acknowledge funding from the National Natural Science Foundation of China, and the National Key R&D Program of China.
