Cr-Doped LiRuO of the LiRuCrO (x = 0, 0.02, 0.05, 0.1) series was successfully synthesized and the effect of Cr on the electrochemical performance of LiRuO was systematically investigated. The results show that LiRuCrO exhibits the best performance in terms of capacity, rate capability and cycling stability.
In
battery electrolyte design principles, tuning Li+ solvation
structure is an effective way to connect electrolyte chemistry
with interfacial chemistry. Although recent proposed solvation tuning
strategies are able to improve battery cyclability, a comprehensive
strategy for electrolyte design remains imperative. Here, we report
a solvation tuning strategy by utilizing molecular steric effect to
create a “bulky coordinating” structure. Based on this
strategy, the designed electrolyte generates an inorganic-rich solid
electrolyte interphase (SEI) and cathode–electrolyte interphase
(CEI), leading to excellent compatibility with both Li metal anodes
and high-voltage cathodes. Under an ultrahigh voltage of 4.6 V, Li/NMC811
full-cells (N/P = 2.0) hold an 84.1%
capacity retention over 150 cycles and industrial Li/NMC811 pouch
cells realize an energy density of 495 Wh kg–1.
This study provides innovative insights into Li+ solvation
tuning for electrolyte engineering and offers a promising path toward
developing high-energy Li metal batteries.
Summary
Lithium‐rich layered oxides (LRLOs) are highly attractive cathode materials for next‐generation lithium‐ion batteries because of their high reversible capacity, but poor cycle performance and voltage decay are two main problems that strongly limit their practical applications. These challenges also apply to the Ru‐based LRLOs of Li2RuO3. The Li2RuO3 cathode material is highly attractive because of their high conductivity and favourable electrochemical reaction kinetics. To overcome the problems associated with Li2RuO3, in contrast to normal single atom doping, here, we propose a Na, Cr co‐doping strategy with the design of Li2−xNaxRu0.95Cr0.05O3 (x = 0, 0.02, 0.06, and 0.1) series materials. Cr doping increases capacity, and Na doping suppresses voltage decay. As a result, the discharge capacity of the optimal Li1.98Na0.02Ru0.95Cr0.05O3 sample over 240 mAh/g after 50 charge‐discharge cycles at 0.2 C is maintained, and the capacity retention reaches a value of 80.5% compared with 69.1% for the undoped Li2RuO3. The value of the voltage decay in the Li1.98Na0.02Ru0.95Cr0.05O3 sample is 125 mV after 100 cycles at a rate of 1 C, and the voltage decay is 188.4 mV for the undoped Li2RuO3. This finding will expand the scope for designing novel layered electrodes with excellent performance.
Searching for high-performance cathode materials is a crucial task to develop advanced lithium-ion batteries (LIBs) with high-energy densities for electrical vehicles (EVs). As a promising lithium-rich material, LiMnO delivers high capacity over 200 mAh g but suffers from poor structural stability and electronic conductivity. Replacing Mn ions by relatively larger Sn ions is regarded as a possible strategy to improve structural stability and thus cycling performance of LiMnO material. However, large difference in ionic radii of Mn and Sn ions leads to phase separation of LiMnO and LiSnO during high-temperature synthesis. To prepare solid-solution phase of LiMnO-LiSnO, a buffer agent of Ru, whose ionic radius is in between that of Mn and Sn ions, is introduced to assist the formation of a single solid-solution phase. The results show that the LiRuO-LiMnO-LiSnO ternary system evolves from mixed composite phases into a single solid-solution phase with increasing Ru content. Meanwhile, discharge capacity of this ternary system shows significantly increase at the transformation point which is ascribed to the improvement of Li/e transportation kinetics and anionic redox chemistry for solid-solution phase. The role of Mn/Sn molar ratio of LiRuO-LiMnO-LiSnO ternary system has also been studied. It is revealed that higher Sn content benefits cycling stability of the system because Sn ions with larger sizes could partially block the migration of Mn and Ru from transition metal layer to Li layer, thus suppressing structural transformation of the system from layered-to-spinel phase. These findings may enable a new route for exploring ternary or even quaternary lithium-rich cathode materials for LIBs.
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