Boron-Mixed Lithium Cathode Material to Limit Metal Elution
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Solution Overview
Problem
Existing lithium manganese-based oxides used as positive electrode active materials in lithium secondary batteries suffer from electrochemical property degradation due to excess lithium and manganese, leading to transition metal elution, which causes resistance abnormalities and accelerated lifetime degradation.
Innovation Solution
A positive electrode active material is developed by physically mixing a lithium manganese-based oxide with a boron-containing compound, forming a solid solution of C2/m and R3-m phases, to inhibit or mitigate transition metal elution and reduce side reactions with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an overlithiated lithium manganese-based oxide is used as a positive electrode active material, then high capacity under high voltage operating environment is achieved, but electrical conductivity decreases due to excessive manganese content, leading to poor rate characteristics
Solution Approach 1:
The patent uses a composite material structure consisting of an overlithiated lithium manganese-based oxide core (Li1.2Mn0.6O2.6) coated with a lithium nickel manganese oxide layer (Li1-x-yNixMnyO2). This composite structure combines the high capacity advantage of the overlithiated manganese oxide with the improved electrical conductivity and stability provided by the nickel-containing coating layer, thereby resolving the contradiction between high capacity and poor rate characteristics.
2Quantity of substance
If lithium manganese-based oxide with excess lithium and manganese is used, then theoretical high capacity is achieved, but transition metal elution occurs, causing resistance abnormalities and accelerated lifetime degradation
Solution Approach 1:
The patent applies a preliminary protective coating of lithium nickel manganese oxide on the surface of the overlithiated lithium manganese-based oxide particles before battery assembly. This pre-formed coating layer acts as a barrier that prevents transition metal elution during subsequent charge-discharge cycles, thereby preventing resistance abnormalities and extending battery lifetime while maintaining the high capacity benefits of the overlithiated core material.
3Quantity of substance
If LiNiO2-based positive electrode active material is used to achieve high discharge capacity, then battery characteristics are improved, but cation mixing between Li and transition metals occurs, making synthesis difficult and degrading rate characteristics
Solution Approach 1:
The patent employs a core-shell structure where the core region (overlithiated lithium manganese-based oxide) provides high capacity, while the shell region (lithium nickel manganese oxide coating) provides structural stability and prevents cation mixing. This local differentiation of material properties allows the system to achieve high discharge capacity without suffering from the synthesis difficulties and rate characteristic degradation associated with homogeneous LiNiO2 materials.
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
This approach enhances the electrochemical stability and prevents capacity degradation, maintaining high discharge capacity and extending the battery's lifetime by reducing transition metal elution and impurity formation.
Implementation Method 1
forming a solid solution of C2/m and R3-m phases
Implementation Method 2
when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Data Source
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, which is capable of preventing the electrochemical properties of a lithium secondary battery, including rate characteristics, from being degraded due to an excess of lithium and manganese in the lithium manganese-based oxide, and particularly preventing the lifetime degradation of a lithium secondary battery by inhibiting or mitigating the elution of a transition metal from the lithium manganese-based oxide, and a lithium secondary battery including the same.