Porous Insulating Layer in Lithium Secondary Battery
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Solution Overview
Problem
Lithium secondary batteries with porous insulating layers experience decreased output and shortened cycle life when subjected to restraining pressures, leading to electrode material separation and increased internal resistance due to expansion and contraction during charging and discharging.
Innovation Solution
A lithium secondary battery design featuring a porous insulating layer with insulating particles of 0.4 to 0.9 g/cm3 tap density and a lamination pressure of 4 to 50 kgf/cm2, which maintains the distance between electrodes constant and prevents compression of the insulating layer, thereby inhibiting output decreases and enhancing adhesion between electrode active material and current collectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous insulating layer is formed on the electrode active material layer to prevent electrode separation, then adhesion between electrode active material and current collector is improved, but the insulating layer compresses under restraining pressure causing increased internal resistance and decreased battery output
Solution Approach 1:
The patent changes the physical parameters of the porous insulating layer by controlling the tap density of insulating particles within 0.35-0.95 g/cm³ and applying lamination pressure within 1-50 kgf/cm². This parameter optimization ensures the insulating layer maintains its porous structure and prevents compression under restraining pressure, thereby maintaining battery output while providing adequate adhesion protection.
Solution Approach 2:
The patent utilizes a porous insulating layer formed from insulating particles with controlled tap density. The porous structure allows the layer to absorb and distribute restraining pressure without compressing, preventing both electrode separation and internal resistance increase. The porosity enables the layer to maintain its protective function while accommodating mechanical stresses during battery assembly and operation.
2Reliability
If lamination pressure is increased to improve adhesion of electrode active material to current collector, then electrode separation is prevented, but the porous insulating layer compresses causing increased internal resistance
Solution Approach 1:
The patent optimizes the lamination pressure parameter within the range of 1-50 kgf/cm² and insulating particle tap density within 0.35-0.95 g/cm³. This controlled parameter range ensures sufficient adhesion is achieved during manufacturing while preventing excessive compression of the porous insulating layer that would increase internal resistance. The balanced parameter selection resolves the contradiction between adhesion quality and electrical performance.
3Stability of the object's composition
If restraining pressure is applied to the battery assembly to maintain electrode distance, then electrode positioning is stabilized, but the porous insulating layer compresses causing output decrease
Solution Approach 1:
The porous insulating layer acts as a pressure-absorbing buffer that maintains electrode distance stability while preventing compression-induced performance degradation. The porous structure distributes restraining pressure throughout the layer, allowing it to fulfill its positioning function without compressing to the extent that would increase internal resistance and decrease battery output.
Solution Approach 2:
By controlling the tap density of insulating particles and lamination pressure within specific ranges, the patent creates a porous insulating layer with optimized mechanical properties. This layer can withstand restraining pressure while maintaining its porous structure, thereby stabilizing electrode positioning without compromising battery output through excessive compression.
Data Source
AI summary
A lithium secondary battery provided by the present invention includes an electrode body (80) having a structure in which a positive electrode (10) and a negative electrode (20) are laminated, with a separator (30) interposed therebetween, and a porous insulating layer (40) obtained by filling and molding insulating particles is formed on the surface of at least one of the positive electrode (10) and the negative electrode (20) on the side facing the separator (30), wherein insulating particles having a tap density of 0.4 g/cm3 to 0.9 g/cm3 are used as the insulating particles that compose the porous insulating layer (40), and moreover a pressure (90) that is applied in the direction of the lamination to the electrode body (80) is set to a range of 4 kgf/cm2 to 50 kgf/cm2.