Lithium-Ion Cell Anode Structure for Volume-Stable High Energy Density
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Solution Overview
Problem
Lithium-ion cells with metallic anodes face challenges such as complete degradation during discharge, massive volume changes, and uneven lithium deposition, which lead to mechanical stress and potential damage, especially when using high-capacity active materials like silicon, and require improved internal resistance and thermal management.
Innovation Solution
The implementation of a secondary lithium-ion cell design featuring a ribbon-shaped electrode-separator assembly with a porous, electrically conductive matrix for the anode, where metallic lithium is embedded in the matrix to minimize volume changes and enhance conductivity, combined with a housing and contact element configuration that reduces internal resistance and facilitates efficient heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metallic lithium is used as the active material for the anode to increase capacity, then the energy density is improved, but the volume changes massively during charging and discharging causing mechanical stress and potential damage
Solution Approach 1:
The patent employs a porous anode structure where metallic lithium is deposited within a porous matrix material. The porosity allows the lithium to expand and contract during charging and discharging without causing mechanical failure, thus maintaining structural integrity while achieving high lithium capacity.
Solution Approach 2:
The anode is designed as a composite structure combining metallic lithium with a porous matrix material (such as carbon or metal oxide). This composite approach allows the lithium to provide high capacity while the matrix provides mechanical stability and accommodates volume changes, resolving the contradiction between capacity and structural integrity.
2Quantity of substance
If high-capacity active materials like silicon are used in the anode to increase energy density, then the lithium capacity is improved, but uneven lithium deposition occurs leading to mechanical stress and potential damage
Solution Approach 1:
The porous matrix provides a large surface area and uniform pore distribution that promotes even lithium deposition throughout the anode structure. The porous architecture ensures consistent lithium ion transport and uniform nucleation sites, preventing localized stress concentrations and improving deposition uniformity.
3Quantity of substance
If the anode is designed to accommodate high-capacity materials to increase energy density, then the lithium capacity is improved, but complete degradation during discharge occurs reducing cell lifespan
Solution Approach 1:
The composite anode structure combines high-capacity metallic lithium with a stable porous matrix material. The matrix provides structural support that prevents complete degradation of the lithium during discharge cycles, maintaining electrode integrity and extending cell lifespan while preserving high lithium capacity.
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 significantly increases energy density while minimizing volume changes and internal resistance, ensuring stable operation and improved thermal management, thus addressing the limitations of previous cell designs.
Implementation Method 1
a porous, electrically conductive matrix for the anode, where metallic lithium is embedded in the matrix to minimize volume changes
Implementation Method 2
a porous, electrically conductive matrix for the anode, where metallic lithium is embedded in the matrix to minimize volume changes and enhance conductivity
Implementation Method 3
Electrochemical cells can convert stored chemical energy into electrical energy by virtue of a redox-reaction
Implementation Method 4
This ion current crosses the separator and is ensured by an ion-conducting electrolyte
Data Source
AI summary
A secondary lithium ion cell includes an electrode-separator assembly in the form of a winding with two terminal end faces. The electrode separator assembly comprising an anode, a cathode, and a separator. The anode comprises an anode current collector comprising a first longitudinal edge, a second longitudinal edge, a strip-shaped main region, and a free edge strip extending along the first longitudinal edge. The strip shaped main region of the anode current collector is loaded with a layer of negative electrode material and the free edge strip of the anode current collector is not loaded with the negative electrode material. The layer of negative electrode material comprises metallic lithium. The cathode comprises a cathode current collector comprising a first longitudinal edge, a second longitudinal edge, a strip-shaped main region, and a free edge strip extending along the first longitudinal edge.