Functional-Layer Battery Separator for Dendrite and Thermal Shrinkage
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Solution Overview
Problem
Rechargeable lithium batteries face issues with lithium dendrite formation and thermal runaway due to increased current density, leading to separator shrinkage and potential ignition, despite efforts to enhance heat resistance and mechanical strength.
Innovation Solution
A ceramic layer with ceramic particles and a functional layer containing inorganic particles with a working potential greater than 1 V are integrated into the separator and negative electrode-separator assembly, replacing traditional polyolefin-based separators to prevent rapid shrinkage and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading amount of active material is increased to improve energy density, then energy density is improved, but current density increases causing lithium dendrite formation and short-circuit risk
Solution Approach 1:
The patent introduces a coating layer comprising inorganic particles (such as Al2O3, SiO2, TiO2, or ZrO2) and binder on the separator surface as an intermediary between the electrodes. This coating layer acts as a protective barrier that prevents direct contact between lithium dendrites and the separator, thereby maintaining reliability while allowing high energy density designs.
Solution Approach 2:
The patent employs a composite coating layer combining inorganic particles with organic binder materials (such as polyvinylidene fluoride, carboxymethyl cellulose, or styrene-butadiene rubber). This composite structure provides both mechanical strength to prevent short-circuits and chemical stability to resist dendrite penetration, enabling safe operation at high loading amounts.
2Strength
If inorganic coating is applied to enhance heat resistance and mechanical strength, then separator stability is improved, but thermal shrinkage during short-circuit still occurs leading to thermal runaway
Solution Approach 1:
The patent modifies the thermal properties of the separator by coating it with inorganic particles that have high thermal stability. The coating layer changes the effective thermal expansion coefficient and heat resistance parameters of the separator system, allowing it to maintain mechanical strength and dimensional stability even at elevated temperatures during short-circuit conditions, thereby preventing thermal shrinkage-induced thermal runaway.
3Quantity of substance
If separator thickness is reduced to improve energy density, then energy density is improved, but separator's ability to prevent short-circuit and thermal runaway is compromised
Solution Approach 1:
The patent utilizes a porous coating layer structure that provides sufficient mechanical strength and thermal stability for short-circuit prevention while maintaining thin overall thickness. The porous structure allows ion transport while the inorganic particle network provides structural support, enabling the separator to be thinner without compromising safety.
Solution Approach 2:
The coating layer serves as an intermediary protective barrier that compensates for the reduced thickness of the separator. Even when the base separator is thin, the coating layer provides an additional safety barrier against dendrite penetration and thermal shrinkage, maintaining short-circuit prevention capability while enabling higher energy density through reduced separator mass.
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 suppresses lithium dendrite formation and side reactions, enhancing the safety and cycle life of rechargeable lithium batteries while maintaining high capacity and density.
Implementation Method 1
a functional layer on the negative electrode and including inorganic particles having a working potential (vs Li/Li+) of greater than or equal to about 1 V and a binder
Implementation Method 2
excellent or suitable shape retention at high temperatures, preventing or reducing rapid shrinkage of the separator due to a short-circuit
Data Source
AI summary
A separator for a rechargeable lithium battery, negative electrode-separator assembly for a rechargeable lithium battery, and rechargeable lithium battery are provided. The separator includes a ceramic layer including ceramic particles and a binder, and a functional layer on the ceramic layer including inorganic particles having a working potential (vs Li/Li+) of greater than or equal to about 1 V and a binder.