Molybdenum-Coated Lithium Manganese Cathode for Lower Surface Resistance
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Solution Overview
Problem
Existing overlithiated lithium manganese-based oxides for lithium secondary batteries suffer from low electrochemical properties and stability due to high surface resistance and manganese elution, which degrades charge/discharge capacity and lifetime efficiency.
Innovation Solution
Surface modification of lithium manganese-based oxide using molybdenum to reduce surface resistance, form a spinel phase, and create a physical barrier against electrolyte reactions, thereby stabilizing the surface and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If overlithiated lithium manganese-based oxide is used as positive electrode active material, then theoretical high capacity under high voltage operating environment is achieved, but electrical conductivity is low and rate performance is poor
Solution Approach 1:
The patent applies parameter changes by controlling the Li/(Mn+Ni) molar ratio within a specific range (1.05-1.30) and adjusting the Ni content (0.10-0.40 mol ratio) to optimize both capacity and rate performance. This precise parameter control transforms the material properties to achieve high capacity while maintaining good rate performance
Solution Approach 2:
The patent creates a composite material system by combining overlithiated lithium manganese-based oxide with specific crystal structures (R-3m and C2/m space groups) and controlling phase composition. This composite approach integrates multiple beneficial properties to simultaneously achieve high capacity and improved electrical conductivity for better rate performance
2Quantity of substance
If LiNiO2-based positive electrode active material is synthesized, then high discharge capacity is achieved, but cation mixing between Li and transition metal occurs making synthesis difficult and rate performance poor
Solution Approach 1:
The patent resolves synthesis difficulty by changing the compositional parameters to Li/(Mn+Ni) molar ratio of 1.05-1.30 and Ni content of 0.10-0.40 mol ratio, which prevents excessive cation mixing while maintaining high discharge capacity. These parameter adjustments make the material synthesizable with conventional methods
Solution Approach 2:
The patent applies local quality by creating specific crystal phases (R-3m and C2/m space groups) with distinct local structures that prevent cation mixing in critical regions. This local structural optimization enables successful synthesis while maintaining high discharge capacity
3Object-affected harmful factors
If lithium manganese oxide is used as positive electrode active material, then excellent thermal safety and low cost are achieved, but capacity is small and high-temperature characteristics are poor
Solution Approach 1:
The patent creates a composite material by combining lithium manganese oxide with nickel in specific proportions (Ni content: 0.10-0.40 mol ratio) to form a new phase composition. This composite structure enhances capacity while preserving the excellent thermal safety characteristics of the lithium manganese oxide base material
Solution Approach 2:
The patent improves capacity by changing the compositional parameters to Li/(Mn+Ni) molar ratio of 1.05-1.30, which increases the lithium content and enables higher capacity. This parameter change maintains thermal safety by staying within stable compositional ranges
4Reliability
If LiCoO2 is used as positive electrode active material, then excellent lifetime characteristics and charging/discharging efficiency are achieved, but cost is high due to limited cobalt resource
Solution Approach 1:
The patent replaces expensive cobalt with cheaper nickel and manganese elements in a controlled composition (Ni: 0.10-0.40 mol ratio). This substitution uses abundant, low-cost materials to achieve comparable lifetime characteristics, significantly reducing material cost while maintaining performance
Solution Approach 2:
The patent optimizes the Li/(Mn+Ni) molar ratio to 1.05-1.30 to ensure excellent lifetime characteristics are achieved with the nickel-based composition. This parameter optimization ensures that the cheaper material substitute delivers performance equivalent to traditional LiCoO2
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 surface modification significantly enhances the lifetime characteristics of lithium secondary batteries by reducing surface resistance, preventing early deterioration, and improving electrochemical stability.
Implementation Method 1
surface modification of the lithium manganese-based oxide using molybdenum to reduce surface resistance
Implementation Method 2
form a spinel phase through surface modification
Implementation Method 3
create a physical barrier against electrolyte reactions, thereby stabilizing the surface
Implementation Method 4
when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Data Source
Figure 1~3
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a positive electrode active material including an overlithiated lithium manganese-based oxide, wherein through surface modification of the lithium manganese-based oxide, the surface resistance of the lithium manganese-based oxide is reduced, thereby improving the lifetime characteristics of the lithium secondary battery, which uses the lithium manganese-based oxide as a positive electrode active material, and a lithium secondary battery including the same.