Lithium Battery Overcharge Safety via Dual Redox Additives
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Solution Overview
Problem
Lithium secondary batteries face safety issues such as ignition and explosion due to overcharging, and existing additives either fail to prevent performance deterioration or are ineffective at high charge currents, necessitating a solution that enhances overcharge safety and minimizes performance degradation.
Innovation Solution
A lithium secondary battery design utilizing a combination of two electrolyte compounds with different oxidation initiation voltages, where the first compound generates heat or gas and forms a passivation layer at higher voltages to prevent ignition, and the second compound consumes overcharge current through reversible redox shuttle, minimizing performance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-aqueous electrolyte additives are used to control ignition or explosion from temperature rise, then overcharge safety is improved, but performance deterioration occurs due to increased battery resistance
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by introducing a specific additive compound (Formula 1) with controlled oxidation initiation voltage. This compound's oxidation potential is designed to be higher than the cathode operating voltage, allowing it to remain inactive during normal operation and thus not increase battery resistance, while still providing safety protection when overcharge occurs and voltage exceeds this threshold.
Solution Approach 2:
The additive compound performs preliminary protective action by being pre-positioned in the electrolyte at controlled concentrations (0.01-5 wt%). It remains dormant during normal battery operation and only activates when overcharge conditions are reached, at which point it oxidizes to consume excess current and prevent thermal runaway, thereby protecting the battery before catastrophic failure can occur.
2Reliability
If alkylbenzene derivative such as cyclohexylbenzene is used as electrolyte additive, then overcharge safety is improved, but performance deteriorates due to partial consumption by reaction during repeated cycling
Solution Approach 1:
The patent modifies the chemical structure and oxidation potential parameters of the additive by using a specifically designed compound (Formula 1) rather than conventional alkylbenzene derivatives. This compound's oxidation initiation voltage is precisely controlled to be higher than cathode operating voltage, which prevents it from reacting during normal charge-discharge cycles. The compound only reacts when overcharge conditions are met, thus preserving battery performance during repeated cycling while maintaining overcharge safety.
Solution Approach 2:
The additive compound is designed to be a sacrificial protective agent that remains stable and inactive during normal battery operation (long duration), but is ready to be consumed in a controlled manner only when overcharge conditions occur. This selective reactivity pattern allows the battery to achieve long cycle life under normal conditions while the additive provides emergency protection when needed.
3Reliability
If redox shuttle mechanism additive is used, then overcharge safety is improved, but effectiveness is lost when charge current is high
Solution Approach 1:
The patent changes the electrochemical parameters by using an additive compound with oxidation initiation voltage higher than cathode operating voltage. This parameter setting allows the additive to remain electrochemically inert during normal charging operations, including high charge current conditions, thus not interfering with charging productivity. Only when overcharge conditions cause voltage to exceed this threshold does the compound oxidize and activate its protective function.
Solution Approach 2:
The additive is pre-configured in the electrolyte with specific oxidation characteristics that keep it dormant during normal operation. It stands ready to activate only when overcharge conditions are detected through voltage threshold exceedance, at which point it rapidly oxidizes to consume excess current and prevent safety incidents, without interfering with normal high-rate charging operations.
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 battery achieves improved overcharge safety and reduced performance deterioration by using a combination of electrolyte compounds with controlled oxidation mechanisms, effectively preventing ignition and maintaining capacity even under high charge currents and long-term storage.
Implementation Method 1
the first compound is oxidized at a voltage higher than the operating voltage of the cathode to generate heat and/or generate gas and/or form a passivation layer on an electrode surface
Implementation Method 2
the second compound undergoes oxidation-reduction cycling (redox shuttle)
Data Source
AI summary
Disclosed is an electrolyte for batteries, comprising: (a) an electrolyte salt; (b) an organic solvent; (c) a first compound having an oxidation initiation voltage (vs. Li/Li+) higher than the operating voltage of a cathode; and (d) a second reversible compound having an oxidation initiation voltage higher than the operating voltage of the cathode, but lower than the oxidation initiation voltage of the first compound. Also disclosed is a lithium secondary battery comprising said electrolyte. In the lithium secondary battery, two compounds having different safety improvement actions at a voltage higher than the operating voltage of the cathode are used in combination as electrolyte components. Thus, the safety of the secondary battery in an overcharged state can be ensured, and at the same time, the deterioration of the battery can be prevented from occurring when it is repeatedly cycled, continuously charged and stored at high temperature for a long time.