Yuanlong Zhu’s research while affiliated with Xiamen University and other places

Electrolyte engineering is crucial for improving cathode electrolyte interphase (CEI) to enhance the performance of lithium‐ion batteries, especially at high charging cut‐off voltages. However, typical electrolyte modification strategies always focus on the solvation structure in the bulk region, but consistently neglect the dynamic evolution of electrolyte solvation configuration at the cathode‐electrolyte interface, which directly influences the CEI construction. Herein, we reveal an anti‐synergy effect between Li⁺‐solvation and interfacial electric field by visualizing the dynamic evolution of electrolyte solvation configuration at the cathode‐electrolyte interface, which determines the concentration of interfacial solvated‐Li⁺. The Li⁺ solvation in the charging process facilitates the construction of a concentrated (Li⁺‐solvent/anion‐rich) interface and anion‐derived CEI, while the repulsive force derived from interfacial electric field induces the formation of a diluted (solvent‐rich) interface and solvent‐derived CEI. Modifying the electrochemical protocols and electrolyte formulation, we regulate the “inflection voltage” arising from the anti‐synergy effect and prolong the lifetime of the concentrated interface, which further improves the functionality of CEI architecture.

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.

Electrolyte engineering is crucial for improving cathode electrolyte interphase (CEI) to enhance the performance of lithium‐ion batteries, especially at high charging cut‐off voltages. However, typical electrolyte modification strategies always focus on the solvation structure in the bulk region, but consistently neglect the dynamic evolution of electrolyte solvation configuration at the cathode‐electrolyte interface, which directly influences the CEI construction. Herein, we reveal an anti‐synergy effect between Li+‐solvation and interfacial electric field by visualizing the dynamic evolution of electrolyte solvation configuration at the cathode‐electrolyte interface, which determines the concentration of interfacial solvated‐Li+. The Li+ solvation in the charging process facilitates the construction of a concentrated (Li+‐solvent/anion‐rich) interface and anion‐derived CEI, while the repulsive force derived from interfacial electric field induces the formation of a diluted (solvent‐rich) interface and solvent‐derived CEI. Modifying the electrochemical protocols and electrolyte formulation, we regulate the “inflection voltage” arising from the anti‐synergy effect and prolong the lifetime of the concentrated interface, which further improves the functionality of CEI architecture.

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.

Developing sacrificial cathode pre‐lithiation technology to compensate for active lithium loss is vital for improving the energy density of lithium‐ion battery full‐cells. Li 2 CO 3 owns high theoretical specific capacity, superior air stability, but poor conductivity as an insulator, acting as a promising but challenging pre‐lithiation agent candidate. Herein, extracting a trace amount of Co from LiCoO 2 (LCO), we develop a lattice engineering through substituting Li sites with Co and inducing Li defects to obtain Co‐Li 2 CO 3 @LCO, in which both the bandgap and Li‐O bond strength have essentially declined. Benefiting from the synergistic effect of Li defects and bulk phase catalytic regulation of Co, the potential of Li 2 CO 3 deep decomposition significantly decreases from typical >4.7 V to ∼4.25 V versus Li/Li ⁺ , presenting >600 mAh/g compensation capacity. Impressively, coupling 5 wt% Co‐Li 2 CO 3 @LCO within NCM‐811 cathode, 235 Wh/kg pouch‐type full‐cell is achieved, performing 88% capacity retention after 1000 cycles. This article is protected by copyright. All rights reserved

Compensating the irreversible loss of limited active lithium (Li) is essentially important for improving the energy‐density and cycle‐life of practical Li‐ion battery full‐cell, especially after employing high‐capacity but low initial coulombic efficiency anode candidates. Introducing prelithiation agent can provide additional Li source for such compensation. Herein, we precisely implant trace Co (extracted from transition metal oxide) into the Li site of Li2O, obtaining (Li0.66Co0.11□0.23)2O (CLO) cathode prelithiation agent. The synergistic formation of Li vacancies and Co‐derived catalysis efficiently enhance the inherent conductivity and weaken the Li−O interaction of Li2O, which facilitates its anionic oxidation to peroxo/superoxo species and gaseous O2, achieving 1642.7 mAh/g~Li2O prelithiation capacity (≈980 mAh/g for prelithiation agent). Coupled 6.5 wt % CLO‐based prelithiation agent with LiCoO2 cathode, substantial additional Li source stored within CLO is efficiently released to compensate the Li consumption on the SiO/C anode, achieving 270 Wh/kg pouch‐type full‐cell with 92 % capacity retention after 1000 cycles.

Compensating the irreversible loss of limited active lithium (Li) is essentially important for improving the energy‐density and cycle‐life of practical Li‐ion battery full‐cell, especially after employing high‐capacity but low initial coulombic efficiency anode candidates. Introducing prelithiation agent can provide additional Li source for such compensation. Herein, we precisely implant trace Co (extracted from transition metal oxide) into the Li site of Li2O, obtaining (Li0.66Co0.11□0.23)2O (CLO) cathode prelithiation agent. The synergistic formation of Li vacancies and Co‐derived catalysis efficiently enhance the inherent conductivity and weaken the Li‐O interaction of Li2O, which facilitates its anionic oxidation to peroxo/superoxo species and gaseous O2, achieving 1642.7 mAh/g~Li2O prelithiation capacity (~980 mAh/g for prelithiation agent). Coupled 6.5 wt% CLO‐based prelithiation agent with LiCoO2 cathode, substantial additional Li source stored within CLO is efficiently released to compensate the Li consumption on the SiO/C anode, achieving 270 Wh/kg pouch‐type full‐cell with 92% capacity retention after 1000 cycles.

Both LiFePO4 (LFP) and NaFePO4 (NFP) are phosphate polyanion‐type cathode materials, which have received much attention due to their low cost and high theoretical capacity. Substitution of manganese (Mn) elements for LFP/NFP materials can improve the electrochemical properties, but the connection between local structural changes and electrochemical behaviors after Mn substitution is still not clear. This study not only achieves improvements in energy density of LFP and cyclic stability of NFP through Mn substitution, but also provides an in‐depth analysis of the structural evolutions induced by the substitution. Among them, the substitution of Mn enables LiFe0.5Mn0.5PO4 to achieve a high energy density of 535.3 Wh kg⁻¹, while NaFe0.7Mn0.3PO4 exhibits outstanding cyclability with 89.6% capacity retention after 250 cycles. Specifically, Mn substitution broadens the ion‐transport channels, improving the ion diffusion coefficient. Moreover, LiFe0.5Mn0.5PO4 maintains a more stable single‐phase transition during the charge/discharge process. The transition of NaFe0.7Mn0.3PO4 to the amorphous phase is avoided, which can maintain structural stability and achieve better electrochemical performance. With systematic analysis, this research provides valuable guidance for the subsequent design of high‐performance polyanion‐type cathodes.