Core-Shell Electrode Active Material for Battery Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries face issues with initial capacity reduction and stability due to the formation of a solid electrolyte interface (SEI) layer during charging, which consumes lithium ions and leads to reduced battery performance and cyclability, especially when using carbon-based or metalloid-based active materials that undergo significant volume changes.
Innovation Solution
A core-shell electrode active material is introduced, where a polymer or oligomer with a glass transition temperature of 25° C. or less is used as the shell to prevent SEI layer formation, enhance elasticity, and minimize gas generation, thereby maintaining battery capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte interface (SEI) layer is formed on the anode surface during initial charge, then the anode surface is protected and lithium ions can pass, but lithium ions are consumed irreversibly and initial capacity is reduced
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable SEI layer during an initial charging cycle before the battery enters normal operation. This pre-formed layer prevents subsequent electrolyte decomposition and protects the anode surface, while the battery is subsequently charged to higher voltages (4.4V-4.8V) that further stabilize the SEI layer, reducing ongoing lithium consumption and improving initial capacity retention
Solution Approach 2:
The patent changes the voltage parameter by charging the battery to unusually high voltages (4.4V-4.8V) during initial cycles. This parameter change transforms the SEI layer formation process, creating a more stable and protective layer that reduces subsequent lithium ion consumption. The high voltage treatment modifies the chemical composition and structure of the SEI layer, improving its protective function while minimizing capacity loss
2Quantity of substance
If a metal or metalloid-based active material with high electric capacity is used, then battery capacity increases, but volume changes significantly during intercalation/deintercalation causing decomposition and stability degradation
Solution Approach 1:
The patent employs a flexible polymer coating shell that envelops the metal or metalloid core particles. This flexible shell accommodates the significant volume changes that occur during lithium ion intercalation and deintercalation, preventing mechanical stress from causing particle decomposition. The coating maintains structural integrity while allowing the high-capacity core material to function, thus preserving both capacity and stability
Solution Approach 2:
The patent creates a composite structure combining a metal or metalloid core (providing high electric capacity) with a polymer coating shell (providing structural stability). This composite material approach allows the beneficial properties of both components to coexist: the core delivers high capacity while the shell provides mechanical stability and prevents decomposition during volume changes, solving the contradiction between capacity and stability
3Temperature
If a carbon material is used as anode active material, then high voltage battery can be achieved, but maximum theoretical capacity is limited to about 370 mAh/g
Solution Approach 1:
The patent uses composite materials by combining carbon-based materials (enabling high voltage operation) with metal or metalloid-based materials (providing high theoretical capacity). The carbon component maintains structural stability at high voltages while the metal/metalloid component contributes additional capacity through alloying or intercalation mechanisms, achieving both high voltage and high capacity simultaneously
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 effectively suppresses SEI layer formation, maintains high battery capacity, and improves stability by allowing lithium ion transfer while preventing direct contact between the electrolyte and the core, reducing gas generation and volume changes during charge/discharge cycles.
Implementation Method 1
a surface of the core is coated with the shell... allowing lithium ion transfer while preventing direct contact between the electrolyte and the core
Implementation Method 2
a polymer or an oligomer having a glass transition temperature of 25° C. or less when impregnated with an electrolyte... enhance elasticity
Implementation Method 3
minimize gas generation and volume changes during charge/discharge cycles
Data Source
AI summary
Disclosed is an electrode active material having a core-shell structure, which includes: (a) a core capable of intercalating and deintercalating lithium ions; and (b) a shell including a polymer or an oligomer having a glass transition temperature of 25° C. or less when impregnated with an electrolyte, wherein a surface of the core is coated with the shell. Also, an electrode manufactured by using the electrode active material and a secondary battery including the electrode are disclosed. The shell (b) suppresses the formation of an SEI layer during initial charge of a battery, and prevents initial capacity reduction.