Secondary Battery Safety Device with Mechanical Sensor
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Solution Overview
Problem
Lithium-ion secondary batteries face explosions due to excessive internal pressure and temperature from overcharge or short circuits, with existing safety devices failing to effectively dissipate accumulated energy, leading to potential damage or injury.
Innovation Solution
A mechanical connection sensor is mounted on the outer surface of the battery cell, connected in series with a resistor and the electrodes, which switches on to create a short circuit and discharge the battery when excessive pressure is detected, thereby consuming energy and preventing explosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a safety plate is mounted at the outside of the battery to intercept current when inner pressure reaches critical level, then the increase of pressure is prevented, but energy has already been accumulated in the battery and the battery may still explode when overcharge is continuously performed or when inner temperature increases
Solution Approach 1:
The patent applies preliminary action by providing a discharge path through the resistor before the battery reaches critical pressure levels. The mechanical connection sensor continuously monitors pressure and enables energy dissipation through the resistor in advance, so that when abnormal conditions occur, the energy has already been gradually released rather than accumulated, preventing explosion even if overcharge continues or temperature increases.
Solution Approach 2:
The patent converts the harmful accumulated energy into a beneficial dissipation process. By connecting the resistor in parallel with the battery and using the mechanical connection sensor to control the discharge path, the energy that would otherwise cause explosion is redirected through the resistor where it is safely converted to heat, transforming a potential hazard into a protective mechanism.
2Reliability
If a pressure detection means is used to drive a FET for discharging the battery cell, then the battery cell can be discharged when swelling is detected, but when the circuit is abnormally operated, the safety device is not operated and the normal operation cannot be guaranteed
Solution Approach 1:
The patent replaces the electronic FET-based discharge mechanism with a mechanically simple resistor-based parallel discharge path. The mechanical connection sensor directly controls the connection to the resistor without complex circuitry, substituting electronic control components with a simpler mechanical-switching approach that is more reliable and less prone to circuit abnormalities.
Solution Approach 2:
The patent uses a resistor as a simple, inexpensive component for energy dissipation. Rather than relying on complex reusable electronic control systems, the resistor serves as a dedicated energy sink that can handle the discharge load reliably, providing a fail-safe mechanism that does not depend on complex circuit operation.
3Loss of energy
If the inner pressure of the battery cell is increased due to abnormal operation and the battery cell swells, then the mechanical connection sensor is operated to consume electrical energy at the resistor, but the battery cell may still explode when overcharge is continuously performed or when inner temperature increases
Solution Approach 1:
The patent ensures continuous energy dissipation by maintaining the resistor connected in parallel with the battery throughout operation. The mechanical connection sensor continuously monitors pressure and keeps the discharge path active, ensuring that energy is continuously dissipated rather than allowing accumulation, providing uninterrupted protection against explosion even during continuous overcharge or temperature increase.
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 allows for rapid and reliable operation of the safety device, even if the circuit malfunctions, effectively reducing the risk of explosion by dissipating energy through the resistor, ensuring safe battery operation.
Implementation Method 1
a mechanical connection sensor, as a safety device, fixed to the outside of a battery cell for detecting the pressure of the battery cell
Implementation Method 2
electrical energy accumulated in the battery cell is forcibly consumed at the resistor, whereby the energy of the battery cell is decreased
Data Source
AI summary
Disclosed herein is a secondary battery having a mechanical connection sensor, as a safety device, fixed to the outer surface of a prismatic or pouch-shaped battery cell while the mechanical connection sensor is set to OFF. The mechanical connection sensor is connected in series with a resistor having a predetermined resistance value and with a cathode and an anode of the battery cell. When the battery cell swells to a critical value or more due to the abnormal operation of the battery cell, the mechanical connection sensor is turned ON, and therefore, the mechanical connection sensor conducts with the result that the electrical energy of the battery cell is consumed at the resistor. In the secondary battery having the safety device according to the present invention, when the battery swells due to the abnormal response of the battery, energy accumulated in the battery is forcibly consumed, unlike a conventional battery that merely intercepts the current. As a result, the continuous occurrence of the abnormal response is fundamentally prevented, and therefore, more rapid process is possible with excellent pressure sensitivity. Consequently, the safety of the battery is improved.