Sr-Dispersed Ni-Rich Cathode Material for Longer Battery Cycling
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Solution Overview
Problem
Lithium transition metal composite oxides with high Ni content cause side reactions with non-aqueous electrolytes, leading to deterioration of charge-discharge cycle characteristics in secondary batteries.
Innovation Solution
A lithium transition metal composite oxide with a predetermined ratio of Sr present at the surface and in the interior of secondary particles, suppressing side reactions with the non-aqueous electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium transition metal composite oxide with high Ni content (≥80%) is used, then initial discharge capacity is improved, but charge-discharge cycle characteristic deteriorates due to side reactions with non-aqueous electrolyte
Solution Approach 1:
The patent applies local quality by creating a Sr-enriched surface layer on secondary particles through controlled solid solution formation during synthesis. This surface layer has different compositional properties (higher Sr concentration) compared to the interior, providing localized protection against electrolyte side reactions while preserving the high-Ni core's capacity characteristics. The Gini coefficient control (≤0.85 at surface, ≤0.70 in interior) ensures optimal Sr distribution gradient for this protective effect.
Solution Approach 2:
The patent creates a composite structure within the lithium transition metal composite oxide by incorporating Sr into the crystal lattice to form a solid solution. This composite material approach combines the high capacity benefits of Ni-rich composition with the stability benefits of Sr incorporation, where Sr substitutes for Ni in the lattice and provides electrochemical stability while maintaining the layered oxide structure necessary for lithium insertion/extraction.
2Reliability
If Sr is dissolved in solid solution form in NCM-based lithium transition metal composite oxide, then charge-discharge cycle characteristic is improved, but battery characteristics still have room for improvement when using high Ni content material
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Sr concentration distribution parameters (Gini coefficients at surface and interior, and the intensity ratio ISr_OUT/ISr_IN between 1-5). By optimizing these distribution parameters rather than simply adding Sr uniformly, the patent achieves both improved cycle characteristics and maintained battery capacity. The specific parameter ranges control the balance between surface protection and bulk capacity retention.
3Ease of manufacture
If Sr distribution in lithium transition metal composite oxide is not controlled, then manufacturing is simpler, but surface Sr concentration may be insufficient to suppress side reactions with electrolyte
Solution Approach 1:
The patent applies preliminary action by incorporating Sr into the crystal lattice during the synthesis process itself, creating the desired surface-enriched Sr distribution before the material is formed into electrodes. The solid solution formation during heating treatment pre-establishes the protective Sr distribution pattern, eliminating the need for subsequent surface modification steps and simplifying overall manufacturing while ensuring adequate surface Sr concentration.
Data Source
AI summary
The positive electrode active material that is included in the non-aqueous electrolyte secondary battery includes a lithium transition metal composite oxide, said lithium transition metal composite oxide containing Ni and Sr, and including secondary particles that are formed by flocculation of primary particles. In an element concentration distribution of a cross-section of the lithium transition metal composite oxide that is obtained using time-of-flight secondary ion mass spectrometry, the Gini coefficient of Sr on the secondary particle surface is 0.85 or less, the Gini coefficient of Sr in the secondary particle interior is 0.7 or less, and the ratio ISr_OUT/ISr_IN of the standardized strength ISr_OUT of the Sr on the secondary particle surface to the standardized strength ISr_IN of the Sr in the secondary particle interior is 1-5 inclusive.