New materials enable lithium metal batteries to achieve ultra-long cycle life

Science and Technology Daily reporter Zhao Hanbin

In the field of new energy materials, how to achieve higher energy density, safer and longer-lasting lithium metal batteries has always been a major problem in the scientific research community. On September 6, the reporter learned from Yunnan University that Professor Guo Hong's team from the School of Materials and Energy of the university designed a new type of amide-functionalized polymer electrolyte, which provides a strong guarantee for the long-life operation of lithium metal batteries. The relevant results were published in the international journal "Energy and Environmental Science".

In today's rapidly changing energy storage technology, lithium metal batteries are regarded as an important direction of future battery technology due to their high energy density and potential safety improvement, among which the optimization of solid electrolyte performance is particularly critical. Although traditional polymer electrolytes have advantages such as good interface contact and great potential for industrial production, they face challenges such as insufficient mechanical properties, low lithium ion (Li+) transmission efficiency, and poor stability of electrode or electrolyte interfaces in practical applications. These problems seriously restrict the performance and life of lithium metal batteries.

Schematic diagram of the design of amide-functionalized materials. Photo provided by the interviewee

In response to these challenges, Professor Guo Hong's team proposed an innovative molecular design strategy. By introducing abundant amide sites, a unique hierarchical supramolecular network was constructed, which cleverly combined permanent chemical cross-linking and reversible hydrogen bonding, so that the polymer electrolyte has excellent flexibility while maintaining high mechanical strength. More importantly, the introduction of amide sites provides a fast and reversible transmission channel for lithium ions, significantly improving the ion conductivity of the electrolyte. In addition, the pre-desolvation effect of the entire polymer matrix further promotes the transmission efficiency of lithium ions, making their migration in the electrolyte faster and more uniform.

In addition to excellent transmission performance, this new polymer electrolyte can also form a stable interface layer on the electrode surface, effectively preventing the formation of lithium dendrites and the occurrence of interfacial side reactions. Lithium dendrites are a common problem in lithium metal batteries. They not only cause battery short circuits, but also accelerate the aging process of the battery. Therefore, this dual-enhanced interface stability is crucial to improving battery safety and cycle life.

Experimental results show that lithium metal batteries using this new electrolyte have shown amazing durability in cycle tests. Under full charge and discharge conditions, the battery with lithium iron phosphate positive electrode and lithium metal negative electrode still has a capacity retention rate of 96.5% after 850 cycles; while the battery with lithium cobalt oxide positive electrode maintains 96.8% of its capacity after 300 cycles.

It is understood that this new achievement is a major innovation in the design of solid-state electrolytes, proving its great potential in practical applications, providing new ideas for solving the many challenges faced by lithium metal batteries, and also laying a solid theoretical and material foundation for the future development of higher performance and longer life solid-state batteries, which has broad application prospects in electric vehicles, energy storage systems and other fields.