Core-Shell Cathode Material for Stable Overlithiated Li-Mn Batteries
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Solution Overview
Problem
Conventional overlithiated lithium manganese-based oxides in lithium secondary batteries suffer from instability and low electrochemical properties due to excessive lithium and manganese, which hinder their ability to replace commercially available NCM or NCA-type positive electrode active materials, especially in electric vehicle applications where high energy capacity and stability are crucial.
Innovation Solution
A positive electrode active material is developed using an overlithiated lithium manganese-based oxide with a core-shell structure, where the concentration of transition metals like nickel and doping metals is controlled differently in the core and shell regions, enhancing stability and electrochemical performance by mitigating the degradation caused by excessive lithium and manganese.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an overlithiated lithium manganese-based oxide with excessive lithium and manganese is used to increase capacity, then the theoretical capacity is improved, but the stability and electrochemical properties deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell region has a different composition (lower transition metal content, higher lithium content) compared to the core region. This gradient structure allows the shell to protect the high-capacity core while maintaining stability, resolving the contradiction between high lithium content and stability.
2Quantity of substance
If the concentration of transition metals is increased to enhance capacity, then the energy capacity is improved, but the degradation caused by excessive transition metals worsens
Solution Approach 1:
The patent creates a concentration gradient of transition metals where the shell has lower transition metal content compared to the core. This local variation reduces the harmful degradation effects (such as structural collapse and impedance increase) in the shell region while preserving the high capacity benefits in the core region.
3Ease of manufacture
If a homogeneous composition is used to simplify manufacturing, then the ease of manufacture is improved, but the electrochemical performance deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying the transition metal concentration as a gradient from core to shell rather than using a uniform composition. This controlled parameter variation optimizes electrochemical performance by balancing capacity and stability, while the gradient structure can be achieved through controlled synthesis methods.
4Quantity of substance
If the lithium content is increased beyond the stoichiometric ratio to achieve high capacity, then the charge capacity is improved, but the structural stability deteriorates
Solution Approach 1:
The patent creates a local quality gradient where the shell region has a higher lithium to transition metal ratio compared to the core. This allows the shell to accommodate excess lithium without causing severe structural degradation, while the core maintains a more stable stoichiometric composition for high capacity.
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 improves the electrochemical properties and stability of the lithium manganese-based oxide, increasing the charge-transfer and diffusion of Li ions, thereby enhancing the battery's rate capability and cycle life, making it suitable for high-capacity applications like electric vehicles.
Implementation Method 1
a lithium secondary battery storing electrical energy by means of a difference in chemical potential when lithium ions are intercalated/deintercalated into/from a positive electrode and a negative electrode
Implementation Method 2
Batteries store electrical power by using materials facilitating an electrochemical reaction at a positive electrode and a negative electrode
Implementation Method 3
due to cation mixing between Li and a transition metal, it is difficult to synthesize the LiNiO2-based positive electrode active material
Implementation Method 4
increasing the charge-transfer and diffusion of Li ions, thereby enhancing the battery's rate capability
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 which includes an overlithiated lithium manganese-based oxide including at least lithium, nickel, manganese and a doping metal, and in which the degradation in stability caused by excessive amounts of lithium and manganese in the lithium manganese-based oxide is mitigated and/or prevented by controlling the concentration of a transition metal in the lithium manganese-based oxide for each region, and a lithium secondary battery including the same.