Separator Phosphate Inorganic Layers Battery Thermal Stability
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries face challenges in effectively blocking ion conduction between positive and negative electrodes during abnormal heat generation, leading to insufficient heat suppression, especially as battery capacity and energy density increase, causing separator deformation and ion conduction failure.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a separator with a first filler layer of phosphate particles and a second filler layer of inorganic particles with higher melting points, where phosphate particles enter the base material's pores, forming a polyphosphate film to block ion conduction and maintain separator shape, thereby suppressing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator thickness is reduced to increase battery capacity, then battery energy density is improved, but the shutdown function becomes insufficient and meltdown becomes likely
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base material (providing shutdown function) combined with phosphate particles (providing heat resistance). This composite structure allows the thin separator to maintain both its shutdown capability and thermal stability, resolving the contradiction between reduced thickness and sufficient shutdown function.
Solution Approach 2:
Phosphate particles are selectively added to specific regions of the separator, particularly concentrating them in areas prone to local overheating. This local enhancement of heat resistance allows the separator to maintain shutdown function while being thinner overall, addressing the contradiction between energy density and reliability.
2Temperature
If conventional inorganic particles are used in the separator, then heat resistance is improved, but ion conduction blocking during abnormal heat generation is insufficient
Solution Approach 1:
The invention changes the particle size parameter of phosphate particles to a specific range (0.03-1.0 μm, preferably 0.05-0.5 μm). This parameter optimization ensures that particles are small enough to disperse uniformly and effectively block ion conduction pathways, while being large enough to maintain heat resistance, thus resolving the contradiction between heat resistance and ion conduction blocking.
Solution Approach 2:
The phosphate particles are utilized within the porous structure of the separator base material. The particles fill and modify the pore structure, creating a configuration that maintains porosity for normal ion conduction during operation while blocking ion pathways during abnormal heat generation, thus achieving both heat resistance and effective ion conduction blocking.
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
The solution effectively blocks ion conduction and suppresses heat generation during abnormalities, maintaining separator shape and preventing further heat buildup, while optimizing the entry depth and particle size of phosphate particles to enhance heat management.
Implementation Method 1
some of the phosphate particles enter pores of the base material, and the average value of the entry depth of the particles is 0.1 μm or more and 3 μm or less
Implementation Method 2
a first filler layer including phosphate particles and formed on one surface of the base material... to block the ion conduction (movement of lithium ions) between the positive and negative electrodes
Implementation Method 3
a second filler layer including inorganic particles having a melting point higher than that of the phosphate particles and formed on the other surface of the base material
Data Source
AI summary
In a nonaqueous electrolyte secondary battery which is an example of the embodiment of the present invention, a separator comprises a porous base material, a first filler layer that includes phosphate particles and is formed on one side of the base material, and a second filler layer that includes inorganic particles which have a melting point that is higher than that of the phosphate particles and is formed on the other side of the base material. The volume-based 10% particle size (D10) of the phosphate particles is 0.02 to 0.5 μm and is smaller than the average pore size of the base material. A portion of the phosphate particles penetrates into voids of the base material, and an average value of penetration depth of the particles is 0.1 to 2 μm.