Non-aqueous Electrolyte Battery Overcharging Safety via Gas Agent Ratio
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in maintaining battery characteristics during normal usage while ensuring high reliability against overcharging, as increasing the quantity of gas generating agents to enhance overcharging resistance deteriorates input-output characteristics and durability.
Innovation Solution
Incorporating a mixture of cyclohexylbenzene (CHB) and 4,4′-difluorobiphenyl (4,4′-FBP) as gas generating agents in a specific mass ratio within the non-aqueous electrolyte, activating the pressure-activated current interrupt mechanism at an early stage of overcharging to prevent overcharging, while minimizing the overall content to maintain initial IV resistance and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the quantity of gas generating agent is increased to enhance overcharging resistance, then reliability upon overcharging is improved, but input-output characteristics and durability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the gas generating agent by selecting specific compounds (cyclohexylbenzene and 4,4'-difluorobiphenyl) with appropriate oxidation potentials and gas generation characteristics. This allows achieving the required gas generation quantity for CID activation without excessive addition that would harm battery performance
Solution Approach 2:
The patent uses a composite gas generating system combining two different compounds (cyclohexylbenzene and 4,4'-difluorobiphenyl) with complementary properties. This composite approach enables synergistic gas generation that activates the CID mechanism effectively while maintaining acceptable input-output characteristics and durability
2Reliability
If the quantity of gas generating agent is increased to enhance overcharging resistance, then reliability upon overcharging is improved, but durability (cycle characteristics) deteriorates
Solution Approach 1:
The patent optimizes the concentration and chemical nature of the gas generating agents to achieve sufficient gas generation for CID activation while minimizing the total amount added to the electrolyte. This parameter optimization ensures that durability is not significantly compromised while maintaining high overcharging resistance
Solution Approach 2:
The gas generating agents are designed to be consumed only when needed (during overcharging events) to produce gas for CID activation. Under normal operating conditions, these compounds remain inert and do not affect battery durability, effectively serving as on-demand safety components
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
This approach effectively activates the current interrupt mechanism upon overcharging, maintaining high battery characteristics and resistance to overcharging, ensuring both reliability and performance during normal usage, particularly in high-capacity batteries.
Implementation Method 1
the gas generating agent is oxidized on the surface of the positive electrode, thereby generating hydrogen ions
Implementation Method 2
a compound that decomposes and generates a gas (hereinafter referred to as a 'gas generating agent') when the battery reaches an overcharged state
Implementation Method 3
The hydrogen ions are reduced at the negative electrode, thereby generating hydrogen gas (H2)
Implementation Method 4
As a result of this gas, the pressure inside the battery case increases rapidly, and the current interrupt mechanism can be activated
Data Source
AI summary
Provided is a non-aqueous electrolyte secondary battery that can achieve both battery characteristics during normal usage and resistance to overcharging at high levels. In this non-aqueous electrolyte secondary battery, an electrode body, which includes a positive electrode and a negative electrode, and a non-aqueous electrolyte are housed in a battery case. The battery case is provided with a current interrupt mechanism that activates when the pressure inside the case increases. The non-aqueous electrolyte contains cyclohexylbenzene and 4,4′-difluorobiphenyl as gas generating agents that decompose and generate gas when the battery reaches an overcharged state. In addition, when the overall quantity of the non-aqueous electrolyte is taken to be 100 mass %, a ratio of the content (mass %) of the 4,4′-difluorobiphenyl (W2) relative to the content (mass %) of the cyclohexylbenzene (W1) (W2/W1) is 0.025 to 0.25.