Encapsulated Lithium Battery Electrode for Volume Expansion Control
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Solution Overview
Problem
Lithium secondary batteries face challenges with active materials like silicon and sulfur, which experience high volume expansion during lithiation, leading to pulverization, delamination, and loss of energy capacity due to mechanical stress and unstable solid electrolyte interphase formation, and existing solutions are often energy-intensive or costly.
Innovation Solution
A method of encapsulating active materials within a multi-layered structure using polymeric binders and carbon-based additives, where the application of energy creates a carbonized outer shell for structural support and a soft inner polymer layer for volume expansion accommodation, along with a nano-porous structure for enhanced lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If active materials like silicon and sulfur are used to increase energy density, then capacity is improved, but volume expansion during lithiation causes pulverization and delamination
Solution Approach 1:
The patent embeds active material particles inside hollow porous spheres, creating a nested structure where the active material is contained within a protective shell. This nested configuration allows the active material to expand into the hollow space while the outer shell maintains structural integrity and prevents pulverization.
Solution Approach 2:
The patent employs hollow porous spheres as flexible shells that can accommodate volume changes of the active material. The porous structure provides mechanical flexibility while maintaining structural support, allowing the shell to expand and contract with the active material during lithiation without causing delamination or pulverization.
2Strength
If particle sizes of active materials are reduced to prevent pulverization, then mechanical stability is improved, but contact surface area for ion diffusion decreases
Solution Approach 1:
The patent utilizes hollow porous spheres as the encapsulating structure. The porous walls provide a large internal surface area that maintains good contact with the active material particles inside, facilitating efficient ion diffusion while the overall spherical structure maintains mechanical stability.
Solution Approach 2:
The patent transitions from considering only the external surface area of particles to utilizing the internal surface area of the hollow porous spheres. This dimensional approach allows ion diffusion to occur through the porous walls and internal surfaces, significantly increasing the effective contact surface area while maintaining mechanical stability.
3Area of stationary object
If nano-porous structures are created on active materials to increase contact surface area, then ion diffusion is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the structural parameter of the encapsulating material from solid to hollow porous. This parameter change inherently provides large surface area for ion diffusion without requiring additional complex manufacturing steps to create pores, as the porous structure is integrated into the hollow sphere formation process.
Solution Approach 2:
The patent creates a composite structure combining hollow porous spheres with active material particles. This composite approach achieves the desired nano-porous characteristics and large surface area through the hierarchical structure of the composite, avoiding the need for separate complex pore-creation processes.
4Stability of the object's composition
If hard outer shells are used to suppress volume change, then structural stability is improved, but stress is applied to other active materials causing delamination
Solution Approach 1:
The patent employs hollow porous spheres that act as flexible shells rather than rigid hard shells. These shells can expand and contract with the active material volume changes, providing structural stability while avoiding the generation of excessive mechanical stress that would cause delamination of surrounding materials.
Solution Approach 2:
The porous structure of the hollow spheres provides a compliant framework that can accommodate volume changes through pore expansion and contraction. This porous architecture maintains structural stability while absorbing volume expansion stresses, preventing stress transmission to adjacent active 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 effectively suppresses volume expansion, prevents pulverization, and stabilizes the solid electrolyte interphase, resulting in improved energy capacity and cycling stability while reducing energy and cost burdens.
Implementation Method 1
the elastic modulus of the polymeric binder is 100 MPa or more and less than 1 Gpa, thereby the polymeric binder is capable of suppressing the volume change of the active material
Implementation Method 2
wherein the carbon-based additive has a carbonization temperature of 100° C. or more and less than 300° C.
Data Source
AI summary
The present disclosure relates to a method for manufacturing an electrode for a lithium secondary battery having encapsulated active material using energy application, and the method helps to minimize the volume change of an electrode or negative side effects, such as high internal stress, a fracture, pulverization, delamination, electronic isolation from a conductive agent, the formation of an unstable solid-electrolyte interphase, and a loss of energy capacity of the batteries.