Vacancy-engineered LiMn2O4 for long-lasting lithium-ion batteries via MOF-mediated synthesis

A research team from South China Normal University and Shanghai University has developed a metal-organic framework (MOF) chemistry engineering for hierarchical micro-/nano-structural F, O-dual-doped carbon embedded oxygen vacancy enriched LiMn₂O₄ cathode (O_V-LMO@FOC) for longevous lithium storage. By enhancing ionic/electronic conductivity and inhibiting Mn²⁺ dissolution, this innovative approach has led to over 1000 stable battery cycles with exceptional capacity retention. This study envisions the MOF-chemistry in surface modification and electronic modulation engineering of high-performance cathode materials towards industrialization in automotive market.

With the global intensification of carbon neutrality and surging popularity of electric vehicles (EVs), the development of electrode technology has been flourishing to intrigue the competitive electrochemical metrics (cost-efficiency, energy density, and cycling lifespan) of lithium-ion batteries (LIBs) upon the electrification of automobile industry. Cathode materials are arguably commensurate with more than 40% of both cost and energy density of LIB system. Among these, the all-manganese-based LMO endows the advantage complementary of environmental compatibility, high thermal stability, nontoxicity, high voltage (~4 V), high energy density and safety, as well as overwhelming cost superiority (the price of manganese is approximately 20% of Ni and below 10% of Co). Nevertheless, the LMO cathode is mainly plagued by the cubic-tetragonal Jahn-Teller distortion, Mn²⁺ dissolution in electrolyte due to the Mn³⁺ disproportionation mechanism, jeopardizes the electrode polarization and long-term cyclability, thus leading to severe capacity degradation upon electrochemical operation. Therefore, mitigating these fatal demerits is essential to obtain a long-life rechargeable LIB spinel cathode.

The Solution: The researchers elaborately design and fabricate a MOF-chemistry engineering for hierarchical micro-/nano-structural F, O-dual-doped carbon embedded spinel LiMn₂O₄ cathode (hereinafter termed as O_V-LMO@FOC) by solvothermal and high-temperature sintering methodologies as LIB cathode. Combining experimental and theoretical analyses, comprehensive investigations of O_V-LMO@FOC unveil that the uniformity and existence of oxygen vacancy and F, O-dual-doped carbon energetically facilitate Li⁺ adsorption and diffusion capability, boost electronic conductivity, suppress Mn dissolution in electrolyte, further improving fabulous long-term cycling stability. Consequently, compelling electrochemical metrics are achieved with superior specific capacity, distinguished rate capacity, and exceptional cyclability.

The Future: Future research will explore more practical application scenarios of this battery while controlling costs.

Bestowed by experimental and theoretical implementations, systematic investigations of O_V-LMO@FOC endow that the meticulous integration of F, O-dual-doped carbon and oxygen vacancy in LMO-based cathode reconfigures the electronic structure, boosts electronic conductivity, expedites diffusion capability, facilitates energetically preferable Li⁺ adsorption, and suppresses Mn dissolution in the electrolyte, consequently achieving fabulous long-term cycling stability. As expected, the O_V-LMO@FOC behaves with compelling electrochemical performance with prosperous reversible capacity (130.2 mAh g⁻¹ at 0.2 C upon 200 cycles), exceptional rate capacity (93.7 mAh g⁻¹ even at 20 C), and pronounced long-term cyclability (112.5 mAh g⁻¹ after 1200 cycles with 77.6% capacity retention at 1 C). Even at the ultrahigh current density of 5 C, the O_V-LMO@FOC bears a brilliant capacity of 96.9 mAh g⁻¹ upon 1000 cycles with an extraordinary capacity retention of 90.7%, and maintains a discharge capacity of 70.9 mAh g⁻¹ upon 4000 cycles.

The Impact: This work broadens horizons for meticulous engineering for MOF-chemistry in surface modification and electronic modulation towards longevous cycling-stable cathode materials.

The research has been recently published in the online edition of Materials Futures, a prominent international journal in the field of interdisciplinary materials science research.

Reference
Xiaoming Lin*, Jia Lin, Xiaomeng Lu, Xiaohong Tan, Hao Li, Wanxin Mai, Yuhong Luo, Yongbo Wu, Shuangqiang Chen, Chao Yang*, Yong Wang*. Vacancy-engineered LiMn₂O₄ embedded in dual-heteroatom-doped carbon via metal-organic framework-mediated synthesis towards longevous lithium ion battery. Materials Futures, 2024, DOI: 10.1088/2752-5724/ad9e08