Core-Shell Electrode Active Material for Lithium Battery Safety
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Solution Overview
Problem
Lithium secondary batteries face issues with safety and cycling characteristics due to the formation of transition metal-deficient layers and passivating layers on electrode active materials, leading to impaired lithium ion and electron movement, increased resistance, and thermal runaway.
Innovation Solution
A lithium secondary battery design featuring a core-shell structure with lithium metal oxide particles and a polymer layer on the surface of the electrode active material, which enhances coating performance, reduces specific surface area, and suppresses reactivity with moisture and electrolyte solutions, thereby improving adhesion, stability, and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If no post-processing surface treatment is applied to the cathode active material, then manufacturing complexity is reduced, but a transition metal-deficient layer forms on the surface due to decomposition reactions with the electrolyte solution, impeding lithium ion and electron movement and causing structural changes that deteriorate cycling characteristics
Solution Approach 1:
The patent applies preliminary surface treatment by coating the cathode active material with a specific compound before battery assembly. This pre-coating prevents the formation of the transition metal-deficient layer during initial charging cycles, thereby protecting the underlying active material from degradation and maintaining good cycling characteristics throughout battery operation.
2Reliability
If a passivating layer forms non-uniformly or thickly on the active material surface due to electrolyte solution decomposition, then protection from further degradation is improved, but resistance increases causing deterioration in high rate characteristics
Solution Approach 1:
The patent carefully controls the composition and thickness parameters of the surface coating layer. By optimizing these parameters, the coating provides sufficient protection against electrolyte decomposition while maintaining adequate ionic and electronic conductivity, thus preserving high rate discharge characteristics even after extended cycling.
3Quantity of substance
If lithium compound is generated on the anode surface during operation, then capacity reduction and output characteristics degradation occur due to lithium loss, but this is a natural consequence of initial charging and discharging where 5 to 25% irreversible capacity is exhibited by carbon-based anode active materials
Solution Approach 1:
The patent introduces a surface coating on the cathode active material that acts as an intermediary layer, preventing direct contact between the active material and electrolyte solution. This intermediary layer reduces side reactions that lead to lithium compound formation on the anode, thereby minimizing lithium loss and extending battery operational life while maintaining good initial capacity.
4Temperature
If the battery operates abnormally causing internal temperature increase, then thermal energy increases, but oxygen is generated and thermal runaway phenomenon occurs indicating poor safety
Solution Approach 1:
The patent applies preliminary protective coating to the cathode active material that prevents the formation of unstable surface phases and reduces the likelihood of exothermic decomposition reactions. This preliminary protection creates a barrier that prevents thermal runaway initiation even when the battery experiences abnormal temperature increases, thereby improving safety.
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 core-shell structure enhances cycling characteristics, reduces heat generation, and improves safety by limiting lithium migration and electrolyte reactions, resulting in improved electrochemical performance and extended battery life.
Implementation Method 1
a decomposition reaction between an electrolyte solution and a metal, and the transition metal-deficient layer or a resistor film on the surface of the active material impedes movement of lithium ions and electrons
Implementation Method 2
a shell including lithium metal oxide particles and polymer formed on a core
Data Source
Figure 1~2
Figure 3a~3b
Figure 3c~4
AI summary
Disclosed is an electrode active material including a core formed from one selected from the group consisting of lithium-containing transition metal oxide, a carbon material, a lithium metal, and a metal compound, or mixtures thereof, and a shell formed on a surface of the core and including lithium metal oxide particles and polymer, and a lithium secondary battery using the same.