Lithium Battery Electrode with Layered Conductive Structure
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges with capacity density and cycle life due to the expansion and contraction of negative and positive electrode active substances, leading to delamination and reduced capacity, and existing solutions either compromise on capacity or suffer from mechanical strength issues with ceramic materials.
Innovation Solution
The electrode structure includes a current collector with alternately laminated first and second layers, where the first layer is a high-capacity material like silicon or tin, and the second layer is a conductive metal nitride or carbide with a higher Young's modulus, preventing delamination and maintaining mechanical strength during lithium ion occlusion and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity materials like silicon or tin are used for negative electrode active substance, then capacity per volume increases, but expansion and contraction during lithium ion occlusion and release causes delamination from current collector
Solution Approach 1:
The negative electrode active substance is divided into particles with a specific average particle size (1 μm to 10 μm), which segments the expansion and contraction stress, reducing delamination while maintaining high capacity
Solution Approach 2:
A binder layer is applied to the current collector surface, providing a flexible interface that accommodates the expansion and contraction of the active substance particles, preventing direct delamination from the rigid current collector
2Strength
If porous ceramic body is used to hold expandable active substance, then mechanical strength is improved, but capacity density decreases due to pore volume occupying space
Solution Approach 1:
The patent removes the porous ceramic body entirely, using only the binder layer on the current collector to hold the active substance particles, eliminating the capacity-wasting pore volume while maintaining mechanical strength through the binder
Solution Approach 2:
A composite structure is formed with the binder layer and active substance particles on the current collector, where the binder provides mechanical strength and the particles provide capacity, achieving both requirements without ceramic pores
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 configuration enhances the cycle life and capacity of lithium secondary batteries by allowing volumetric changes while maintaining electrical conductivity and mechanical integrity, enabling higher capacity and longer battery life.
Implementation Method 1
The second layer has a Young's modulus larger than the Young's modulus of the first layer
Implementation Method 2
a first layer containing a first material for occluding and releasing lithium ions
Data Source
AI summary
The present invention has an object of providing a lithium secondary battery and an electrode for a lithium secondary battery having a superb cycle characteristic.The present invention relates to an electrode for a lithium secondary battery, and a lithium secondary battery including the electrode, the electrode including a current collector and an active substance structure provided on the current collector, wherein the active substance structure includes at least one first layer containing a first material for occluding and releasing lithium ions and at least one second layer containing a conductive second material which does not chemically react with lithium; the first layer and the second layer are alternately laminated; and the second layer has a Young's modulus larger than the Young's modulus of the first layer.