Lithium-rich Mn-based oxide (LRMO) is one of the next-generation cathode materials for lithium-ion batteries (LIBs), which is expected to exceed the high energy density of 550 Wh kg- 1.
However, the redox reaction of anionic oxygen (O2-) is slow and not stable, resulting in low rate capability and cycling performance of LIBs, especially in solid-state batteries.
Recently, a research team led by Professor CUI Guanglei from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS), has provided new insights to reveal the heterogeneous transport dynamics of Li+ and the regulation of the oxygen stability of the LRMO cathode anion. materials.
LRMO materials have better application prospects in solid-state batteries than commercial cathode materials due to their high specific capacity and low cost. “It is an important premise to solve the key scientific problems of LRMO by clarifying the micro-mechanism of degradation and developing an innovative material preparation technology,” said Professor CUI of QIBEBT.
The team first observed the heterogeneous Li + transport behavior of LRMO in sulfide solid-state batteries using the technique of in situ differential phase contrast imaging scanning transmission electron microscopy (STEM- DPC). They found that the nanoscale biphasic separation (NCM111 phase and Li2MnO3 phase) in LRMO was the decisive factor for the heterogeneity of Li+ transport in the bulk phase and the cathode-solid electrolyte interface, which severely restricts the capacity contribution of lithium. rich in Li2MnO3.
Their study was published in Angewandte Chemie International Edition.
“We investigated the ‘structure-activity relationship’ between the microstructure, Li + transport kinetics and electrochemical performance of LRMO and elucidated the micromechanism of performance attenuation of LRMO cathode in solid-state batteries,” he said MA Jun, QIBEBT Associate Professor. This study further manifests the importance of precisely optimizing the crystal structure and improving Li + transport kinetics at the cathode/electrolyte interface.
In their study published in Advanced Energy Materials, the researchers proposed a new oscillation-like non-isothermal sintering (SNS) material preparation technology, which stabilized lattice oxygen in the bulk phase of LRMO and reduced the generation of unstable O2p holes.
Compared with traditional constant temperature sintering (CTS) technology, the electrochemical performance of the cathode prepared by SNS technology has been improved, such as specific discharge capacity and cycle stability.
In addition, the feasibility of the SNS technology has also been verified in the cobalt-free lithium-rich manganese-based cathode material system (Li1.2Mn0.6Ni0.2O2).
“This study will provide guidance for stabilizing the anionic oxygen structure and elevating the comprehensive electrochemical properties of LRMO materials,” said ZHANG Yuhan, the first author of the study.
“The previous work lays a solid foundation for exploiting LRMO-based solid-state batteries with high energy density and high safety,” Professor CUI said.
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