Wax-Fixed Electrode Conductive Network for Thermal Runaway Prevention
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Solution Overview
Problem
Lithium ion secondary batteries are prone to swelling, ignition, or explosion due to increased temperature during overcharge, particularly because the cathode active material reacts with the electrolyte, leading to a hazardous 'high-temperature overcharge' situation.
Innovation Solution
An electrode comprising electrode active material particles interconnected by conductive particles, with the paths of these conductive particles partially or entirely fixed by wax, which melts and increases electrical resistance when the temperature rises, interrupting current flow and preventing further temperature increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the battery is designed to have high capacity and energy density, then the energy storage capability is improved, but the safety risk increases due to higher reactivity between cathode active material and electrolyte at elevated temperatures
Solution Approach 1:
The patent introduces wax as an intermediary substance between the cathode active material and the electrolyte. This wax layer acts as a physical barrier that prevents direct contact and reaction between these two components under normal operating conditions, thereby eliminating the safety hazard while preserving high energy density performance
Solution Approach 2:
The patent utilizes the temperature-dependent physical state change of wax (from solid to liquid) as a parameter change mechanism. At normal temperatures, the solid wax maintains structural integrity and provides protection. When abnormal temperature rise occurs, the wax melts and flows away, automatically disabling the protective function and allowing the safety mechanism to activate
2Power
If the cathode active material reacts with the electrolyte at high temperature, then the voltage increases, but the harmful effects of oxidation and ignition risk increase
Solution Approach 1:
The patent applies preliminary anti-action by pre-coating the cathode active material with wax before battery assembly. This preliminary protective layer prevents the harmful oxidation reaction from occurring in the first place by blocking the electrolyte from contacting the cathode material, thereby eliminating ignition risks before they can manifest
3Reliability
If wax is used to fix the conductive particle paths, then the safety is improved by interrupting current flow at high temperature, but the electrical resistance increases
Solution Approach 1:
The patent employs dynamics by using a material (wax) whose physical properties dynamically change with temperature. At operating temperatures, the solid wax maintains stable electrical contact and low resistance. When temperature exceeds the safety threshold, the wax melts and flows away, dynamically changing the electrical resistance from low to high to interrupt current flow and prevent thermal runaway
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 use of wax with low melting viscosity effectively disconnects conductive particles, rapidly increasing electrode resistance to prevent overcharge-related explosions and ignitions, enhancing the safety of electrochemical devices like lithium ion batteries.
Implementation Method 1
the wax melts and flows throughout pores formed in the electrode
Implementation Method 2
the wax, which is an oligomer having an excessively low melting viscosity when compared to a polymer, has excellent mobility when melting
Implementation Method 3
The conductive particles, which are interconnected to one another, interconnect the spaced electrode active materials while functioning as a passageway for electronic conduction
Implementation Method 4
the conductive particles, which were fixed by the wax, are disconnected from one another thereby increasing the resistance in the electrode so as to interrupt the flow of current
Data Source
AI summary
The present invention relates to an electrode comprising electrode active material particles, conductive particles, a binder and wax, wherein the electrode active material particles are interconnected by a network of the conductive particles, and the paths of the conductive particles interconnecting the electrode active materials are partially or entirely fixed by the wax. Furthermore, the present invention provides an electrochemical device comprising the electrode.By use of wax having a low meting viscosity in order to partially or entirely fix the paths of the conductive particles, which interconnect the spaced electrode active material particles, the present invention can improve processability and safety of the electrochemical device.