Composite Phase Change Material for Lithium Battery Cooling
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Solution Overview
Problem
Existing phase change materials are inadequate for efficiently cooling lithium-ion batteries, particularly those used in power tools, due to limitations in thermal conductivity, stability, and flame retardancy, which can lead to reduced battery efficiency and lifespan.
Innovation Solution
A composite phase change material comprising polyethylene glycol, nanoscale silica particles, and a composite flame retardant with a graphite-to-polymer ratio of 1:2, which includes expanded graphite and ammonium polyphosphate, is developed, along with a preparation method involving the mixing and evaporation of these components to enhance thermal conductivity and flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single inorganic or organic phase change material is used, then the material is simple to prepare, but the thermal conductivity efficiency is insufficient
Solution Approach 1:
The patent uses composite phase change material comprising polyethylene glycol, expanded graphite, and ammonium polyphosphate. The expanded graphite provides high thermal conductivity while ammonium polyphosphate adds flame retardancy, resolving the contradiction between preparation simplicity and thermal conductivity efficiency by combining multiple materials with complementary properties
2Reliability
If conventional phase change material is used, then the material has basic cooling function, but the flame retardancy is insufficient
Solution Approach 1:
The patent incorporates ammonium polyphosphate as a flame retardant additive in the composite phase change material. This compound contains phosphorus that forms a protective char layer during combustion, significantly improving flame retardancy while maintaining the cooling function through phase change
3Use of energy by moving object
If phase change material is used for battery cooling, then the thermal storage density is high, but the stability during phase change is insufficient
Solution Approach 1:
The expanded graphite in the composite material forms a three-dimensional conductive network that provides structural support during phase change. This network prevents leakage and maintains morphological stability while the polyethylene glycol component provides high thermal storage density through latent heat of fusion
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 composite phase change material demonstrates improved thermal conductivity, stability, and flame retardancy, effectively managing heat in lithium-ion batteries, thereby increasing their efficiency and service life.
Implementation Method 1
A phase change material is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. For instance, heat may be absorbed or released when the material changes from solid to liquid and vice versa.
Implementation Method 2
The composite phase change material, having less corrosiveness, non-toxicity, and a high stability, has been widely applied in the thermostatical control field... the composite phase change material demonstrates improved thermal conductivity
Data Source
AI summary
A composite phase change material and the method for forming the material is disclosed herein. Thereof, especially a composite phase change material for lithium battery cooling, comprising polyethylene glycol, silica vehicle and composite flame retardant comprising graphite and polymer, wherein the weight ratio of the graphite and polymer is approximately 1:2. The composite phase change material according to the invention has a good stability and a thermal conductivity, a small corrosivity, a high phase transition enthalpy of 150-350 J/g, and a morphological stability during phase change. Moreover, addition of high thermal conductivity material and composite flame retardant ensures good thermal conductivity and excellent flame retardant effect of the phase change material.