Fluorinated Cathode Active Material for High-Rate Li Storage
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Solution Overview
Problem
The existing manufacturing conditions for surface-modified lithium-containing composite oxides in non-aqueous electrolyte secondary batteries fail to inhibit the deterioration of battery capacity during charge and discharge, leading to decreased discharge capacity and poor rate characteristics.
Innovation Solution
A non-aqueous electrolyte secondary battery using an active material with a core that can reversibly occlude and release Li, and a compound adhering to its surface represented by the formula M1aM2Fb (0.1≤a≤2.2, 2≤b≤6), where M1 includes Li, K, or Na, and M2 includes transition metals, Al, Si, B, P, Sn, Ge, Sb, Bi, Mg, or Sr, which improves the battery's rate characteristics by inhibiting side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface modification methods (mixing lithium-containing composite oxide powder with zirconium solutions and ammonium salt solutions followed by heat treatment) are used, then charge-discharge cycle characteristics are improved, but rate characteristics deteriorate due to decreased discharge capacity at high rates
Solution Approach 1:
The patent changes the chemical composition parameters of the surface coating from conventional zirconium-based compounds to fluorinated compounds with specific stoichiometry (M1aM2Fb where 0.1≤a≤2.2 and 2≤b≤6). This parameter change in the coating composition resolves the contradiction by providing a surface layer that simultaneously protects against degradation (improving reliability) and maintains ionic conductivity for high-rate discharge (improving productivity).
Solution Approach 2:
The patent creates a composite structure consisting of a lithium-containing composite oxide core (providing capacity) coated with a fluorinated compound shell (M1aM2Fb, providing protection and conductivity). This composite material approach resolves the contradiction by combining the benefits of the core material's high capacity with the coating material's protective and conductive properties, achieving both improved cycle characteristics and maintained rate characteristics.
2Reliability
If surface coating is applied to inhibit side reactions, then battery capacity stability is improved, but discharge capacity at high rates decreases
Solution Approach 1:
The patent optimizes the stoichiometric parameters of the surface coating (M1aM2Fb with specific ranges for a and b) to achieve the right balance between protection and conductivity. By precisely controlling the fluorine content and metal ratios in the coating, the patent maintains battery capacity stability while preventing the discharge capacity from decreasing at high rates.
Solution Approach 2:
The patent applies a surface coating only on the exterior of the lithium-containing composite oxide particles, creating a localized protective layer. This local quality approach allows the bulk material to maintain its high capacity characteristics while the surface provides protection against side reactions, thus improving capacity stability without significantly reducing discharge capacity even at high rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution effectively inhibits the deterioration of discharge capacity at high rates, enhancing the battery's rate characteristics and maintaining performance.
Implementation Method 1
a compound adhering to a surface of the core
Implementation Method 2
a core that is able to reversibly occlude and release Li
Data Source
AI summary
Provided is an active material that contributes to improved battery rate characteristics. This active material for nonaqueous electrolyte secondary batteries contains a core capable of reversible Li storage/release and contains a compound attached to the surface of the core. The compound is represented by the general formula M1aM2Fb (0.1≤a≤2.2, 2≤b≤6, M1 is at least one element selected from the group consisting of Li, K, and Na, and M2 is at least one element selected from the group consisting of transition metals and Al, Si, B, P, Sn, Ge, Sb, Bi, Mg, Ca, and Sr).