Graded Electrode Composition for All-Solid Battery Ion Conduction
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Solution Overview
Problem
Lithium secondary batteries face issues with overpotential, electrode material expansion, and interruption of conductive and metal ion conduction paths due to uneven ion mobility and structural deformation during charge and discharge cycles.
Innovation Solution
An all-solid secondary battery design with a positive electrode and negative electrode active material layer composition distribution where the electrolyte content ratio increases from the solid electrolyte interface to the current collector interface, ensuring sufficient ion mobility and porosity to absorb expansion and contraction, thereby reducing overpotential and maintaining conductive paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte is mixed with active material in the electrode, then ion conduction is enabled, but the ion conduction path may be interrupted depending on mixing ratio, increasing impedance
Solution Approach 1:
The patent applies local quality by creating a gradient distribution of solid electrolyte within the electrode active material layer. The mixing ratio varies continuously from the current collector interface to the solid electrolyte layer interface, with higher electrolyte content near the current collector and lower content near the solid electrolyte layer. This spatial variation in composition optimizes both ion conduction path continuity and electrical impedance at different locations within the electrode.
Solution Approach 2:
The patent implements parameter changes by systematically varying the solid electrolyte content ratio as a gradient parameter throughout the electrode thickness. By controlling the mixing ratio to increase from the current collector side toward the solid electrolyte layer side, the invention optimizes the balance between maintaining conductive paths and enabling ion conduction, thereby reducing overall electrode impedance while ensuring reliable ion transport.
2Quantity of substance
If electrode active material layer is made dense, then energy density increases, but conductive path and metal ion conduction path may be interrupted
Solution Approach 1:
The patent applies local quality by creating distinct regions within the electrode active material layer with different electrolyte concentrations. The gradient structure ensures that regions closer to the current collector have higher electrolyte content to maintain conductive path continuity, while regions closer to the solid electrolyte layer have lower electrolyte content to maximize active material density and energy storage capacity.
Solution Approach 2:
The patent segments the electrode active material layer into multiple zones with varying electrolyte content. This segmentation allows different portions of the electrode to fulfill different functions: the current collector-side region prioritizes electrical conductivity and electron transport, while the solid electrolyte layer-side region prioritizes ion conduction and active material utilization, thereby maintaining both conductive path continuity and high energy density.
3Productivity
If positive electrode and negative electrode alternately expand and contract during charge and discharge, then lithium ion movement is enabled, but battery may warp or deform and cracks may occur
Solution Approach 1:
The patent applies beforehand cushioning by designing a gradient electrolyte distribution that anticipates and compensates for expansion and contraction stresses. The higher electrolyte content near the current collector provides a cushioning effect that absorbs mechanical stress during volume changes, preventing crack formation and maintaining structural integrity throughout charge and discharge cycles.
4Reliability
If mixing ratio between solid electrolyte and active material is optimized, then ion conduction is improved, but no consideration is given to distribution of ion mobility in the electrode
Solution Approach 1:
The patent implements parameter changes by transforming the uniform mixing ratio into a gradient parameter that varies spatially within the electrode. This gradient parameter (electrolyte content ratio) is systematically changed from the current collector interface to the solid electrolyte layer interface, thereby controlling ion mobility distribution throughout the electrode without requiring complex multi-layer structures.
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 design decreases battery resistance, enhances energy density, and improves discharge characteristics by ensuring efficient ion movement and structural integrity during charge and discharge cycles.
Implementation Method 1
a solid electrolyte that holds between the positive electrode body and the negative electrode body
Implementation Method 2
reducing the possibility that an electrode active material layer expands and contracts
Implementation Method 3
Lithium ions (Li+) generated in the formula (1) move in an electrolyte held between the negative electrode and the positive electrode, from the negative electrode to the positive electrode due to electro-osmosis
Data Source
AI summary
In an all-solid secondary battery, in an electrode active material layer of at least one of positive and negative electrode bodies, a total content ratio, which is represented by a ratio of mass of an electrolyte contained in the electrode active material layer to mass of an active material contained in the electrode active material layer, is larger than 1; and the electrode active material layer of the at least one of the positive and negative electrode bodies has a composition distribution in which a local content ratio, which is represented by a ratio of mass of the electrolyte contained in a portion of the electrode active material layer to mass of the active material contained in the portion of the electrode active material layer, increases from a solid electrolyte interface toward a current collector interface in a thickness direction of the electrode active material layer.