Jianhua Yin’s research while affiliated with Xiamen University and other places

Developing sacrificial cathode prelithiation technology to compensate for irreversible lithium loss is crucial for enhancing the energy density of lithium‐ion batteries. Antifluorite Li‐rich Li 5 FeO 4 (LFO) is a promising prelithiation agent due to its high theoretical capacity (867 mAh g ⁻¹ ) and superior decomposition dynamic (<4.0 V vs. Li/Li ⁺ ). However, the oxygen evolution mechanism in LFO remains unclear, limiting its application as an ideal prelithiation agent. Herein, we systematically track the full lifecycle oxygen footprint in LFO lattice, electrolyte and solid electrolyte interface (SEI). We demonstrate the lattice mismatch induced by the quasi‐disorder rocksalt intermediate phase can activate the lattice oxygen oxidation promoting the dimerization to O 2 . Specifically, in contrast to the O─O dimers formed within typical anionic‐redox active cathodes, the oxidation of lattice oxygen in LFO generates O ⁻ stabilized in Li 6 ‐O configuration. Significantly, a pair of edge‐sharing Li 6 ‐O configurations transforms into a superoxo dimer, which further evolves into O 2 via a ligand‐to‐metal charge transfer process. Moreover, we demonstrate that nucleophilic intermediates threaten the stability of electrolytes and SEI. Leveraging the insights above, we offer comprehensive perspectives for the modification of ideal prelithiation agents.

Developing sacrificial cathode prelithiation technology to compensate for irreversible lithium loss is crucial for enhancing the energy density of lithium‐ion batteries. Antifluorite Li‐rich Li5FeO4 (LFO) is a promising prelithiation agent due to its high theoretical capacity (867 mAh g⁻¹) and superior decomposition dynamic (<4.0 V vs. Li/Li⁺). However, the oxygen evolution mechanism in LFO remains unclear, limiting its application as an ideal prelithiation agent. Herein, we systematically track the full lifecycle oxygen footprint in LFO lattice, electrolyte and solid electrolyte interface (SEI). We demonstrate the lattice mismatch induced by the quasi‐disorder rocksalt intermediate phase can activate the lattice oxygen oxidation promoting the dimerization to O2. Specifically, in contrast to the O─O dimers formed within typical anionic‐redox active cathodes, the oxidation of lattice oxygen in LFO generates O⁻ stabilized in Li6‐O configuration. Significantly, a pair of edge‐sharing Li6‐O configurations transforms into a superoxo dimer, which further evolves into O2 via a ligand‐to‐metal charge transfer process. Moreover, we demonstrate that nucleophilic intermediates threaten the stability of electrolytes and SEI. Leveraging the insights above, we offer comprehensive perspectives for the modification of ideal prelithiation agents.

Efforts to improve the specific capacity and energy density of lithium nickel-cobalt-manganese oxide (NCM) cathodes focus on operating at high voltages or increasing nickel content. However, both approaches necessitate a...

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (Oⁿ⁻). Upon low‐DOD cycling, the accumulation of Oⁿ⁻ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li⁺ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of Oⁿ⁻ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.

More and more basic practical application scenarios have been gradually ignored/disregarded, in fundamental research on rechargeable batteries, e.g. assessing cycle life under various depths‐of‐discharge (DODs). Herein, although benefit from the additional energy density introduced by anionic redox, we critically revealed that lithium‐rich layered oxide (LRLO) cathodes present anomalously poor capacity retention at low‐DOD cycling, which is essentially different from typical layered cathodes (e.g. NCM), and pose a formidable impediment to the practical application of LRLO. We systemically demonstrated that DOD‐dependent capacity decay is induced by the anionic redox and accumulation of oxidized lattice oxygen (On‐). Upon low‐DOD cycling, the accumulation of On‐ and the persistent presence of vacancies in the transition metal (TM) layer intensified the in‐plane migration of TM, exacerbating the expansion of vacancy clusters, which further facilitated detrimental out‐of‐plane TM migration. As a result, the aggravated structural degradation of LRLO at low‐DOD impeded reversible Li+ intercalation, resulting in rapid capacity decay. Furthermore, prolonged accumulation of On‐ persistently corroded the electrode‐electrolyte interface, especially negative for pouch‐type full‐cells with the shuttle effect. Once the “double‐edged sword” effect of anionic redox being elucidated under practical condition, corresponding modification strategies/routes would become distinct for accelerating the practical application of LRLO.

In addressing the global climate crisis, the energy storage performance of Li‐ion batteries (LIBs) under extreme conditions, particularly for high‐energy‐density Li‐rich layered oxide (LRLO) cathode, is of the essence. Despite numerous researches into the mechanisms and optimization of LRLO cathodes under ideal moderate environment, there is a dearth of case studies on their practical/harsh working environments (e.g., pouch‐type full‐cell, high‐temperature storage), which is a critical aspect for the safety and commercial application. In this study, using pouch‐type full‐cells as prototype investigation target, the study finds the cell assembled with LRLO cathode present severer voltage decay than typical NCM layered cathode after high‐temperature storage. Further decoupling elucidates the primary failure mechanism is the over‐activation of lattice oxidized oxygen (aggravate by high‐temperature storage) and subsequent escape of oxidized oxygen species (Oⁿ⁻), which disrupts transition metal (TM) coordination and exacerbates electrolyte decomposition, leading to severe TM dissolution, interfacial film reconstruction, and harmful shuttle effects. These chain behaviors upon high‐temperature storage significantly influence the stability of both electrodes, causing substantial voltage decay and lithium loss, which accelerates full‐cell failure. Although the anionic redox reaction can bring additional energy, but the escape of metastable Oⁿ⁻ species would introduce new concerns in practical cell working conditions.

Layered oxide cathodes encounter structural challenges during cycling, prompting the exploration of an ingenious heterostructure strategy, which incorporates stable components into the layered structure as strain regulators to enhance materials cycle stability. Despite considerable research efforts, identifying suitable, convenient, and cost-effective materials and methods remains elusive. Herein, focused on lithium cobalt oxide (LiCoO2), we utilized its low-temperature polymorph as a strain-retardant embedded within a cathode. Our findings reveal that the low-temperature component, exhibiting zero-strain characteristic, adopts a complex configuration with a predominant lithiated spinel structure, also featuring both cubic-layered and typical-layered configurations. But this composite cathode exhibits a sluggish lithium-ion transport rate, attributed to Co&Li dislocation at the dual structural boundaries and the formation of cobalt(iii) oxide. This investigation presents a pioneering endeavor in employing heterostructure strategies, underscoring the critical role of such strategies in component selection, which ultimately propels the advancement of layered oxide cathode candidates for Li-ion battery technology.

Compensating for the irreversible loss of limited active sodium (Na) is crucial for enhancing the energy density of practical sodium‐ion batteries (SIBs) full‐cell, especially when employing hard carbon anode with initially lower coulombic efficiency. Introducing sacrificial cathode presodiation agents, particularly those that own potential anionic oxidation activity with a high theoretical capacity, can provide additional sodium sources for compensating Na loss. Herein, Ni atoms are precisely implanted at the Na sites within Na2O framework, obtaining a (Na0.89Ni0.05□0.06)2O (Ni–Na2O) presodiation agent. The synergistic interaction between Na vacancies and Ni catalyst effectively tunes the band structure, forming moderate Ni–O covalent bonds, activating the oxidation activity of oxygen anion, reducing the decomposition overpotential to 2.8 V (vs Na/Na⁺), and achieving a high presodiation capacity of 710 mAh/g≈Na2O (Na2O decomposition rate >80%). Incorporating currently‐modified presodiation agent with Na3V2(PO4)3 and Na2/3Ni2/3Mn1/3O2 cathodes, the energy density of corresponding Na‐ion full‐cells presents an essential improvement of 23.9% and 19.3%, respectively. Further, not limited to Ni–Na2O, the structure–function relationship between the anionic oxidation mechanism and electrode–electrolyte interface fabrication is revealed as a paradigm for the development of sacrificial cathode presodiation agent.