Novel Strategies to Accelerate Application of Lithium-Rich Mn Cathode

Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202209626″ width=”500″ height=”347″/>

HAADF and DPC-STEM in situ were used to directly observe Li-ion transport heterogeneity caused by phase separation, which elucidates the reason for the capacity limitation of Li-rich layered oxides. Credit: Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202209626

Lithium-Rich Mn 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 unstable, resulting in poor throughput capacity and cycling performance of LIBs, especially in solid-state batteries.

Recently, a research team led by Prof. Cui Guanglei from Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS), provided new information on revealing heterogeneous Li+ transport dynamics and stability regulation of anionic oxygen in LRMO cathode materials.

LRMO materials have better application prospects in solid-state batteries than commercial cathode materials due to their high specific capacitance and low cost. “It is an important premise for solving key scientific problems of LRMO by clarifying the micro-mechanism of degradation and developing innovative material preparation technology,” said Professor Cui of QIBEBT.

The team first observed the heterogeneous Li+ Transport behavior of LRMO in solid-state sulfide batteries using the in situ differential phase contrast imaging scanning transmission electron microscopy (STEM-DPC) technique. They found that the separation into two nanoscale phases (NCM111 phase and Li2MnO3 phase) in the LRMO was the decisive factor for the Li+ transport heterogeneity in the bulk phase and the interface of cathode and solid electrolyte, which greatly limits the capacity contribution of lithium-rich Li2MnO3.

Their study was published in Angewandte Chemie International Edition.

“We investigated the ‘structure-activity relationship’ between the microstructure, Li+ the transport kinetics and electrochemical performance of LRMO, and clarified the performance attenuation micro-mechanism for LRMO cathode in solid-state batteries,” said Ma Jun, associate professor at QIBEBT. This study further demonstrates the importance of accurately optimizing crystal structure and improving Li+ transport kinetics at the cathode/electrolyte interface.

In another study published in Advanced Energy Materialsthe researchers proposed a new swing-type non-isothermal sintering (SNS) material preparation technology, which stabilized the oxygen of the LRMO bulk-phase lattice and reduced the generation of unstable O2p Holes.

Compared with the traditional constant temperature sintering (CTS) technology, the electrochemical performance of the cathode prepared by SNS technology, such as specific discharge capacity and cycle stability, has been improved.

In addition, the feasibility of SNS technology was also verified in the cobalt-free lithium-rich manganese cathode material system (Li1.2min0.6Neither0.2O2).

“This study will provide guidance to stabilize the anionic oxygen structure and elevate the integral electrochemical properties of LRMO materials,” said Zhang Yuhan, the study’s first author.

“The above work lays a solid foundation for exploiting LRMO-based solid-state batteries with high energy density and high safety,” Prof. Cui said.


Flexible solid electrolytes for all-solid-state lithium batteries


More information:
Bowen Liu et al, Direct observation of Li-Ion transport heterogeneity induced by nanoscale phase separation in Li-rich cathodes of solid-state batteries, Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202209626

Yu-Han Zhang et al, Lattice Oxygen Stabilization in Li-Rich Mn-Based Oxides via Non-Isothermal Swing-Type Sintering, Advanced Energy Materials (2022). DOI: 10.1002/aenm.202202341

Provided by Chinese Academy of Sciences


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