Dual-Additive Electrolyte for Li-Ion Overcharge Mitigation
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Solution Overview
Problem
Lithium-ion batteries face degradation and performance reduction due to overcharging, which can lead to lithium plating, electrolyte breakdown, and thermal runaway.
Innovation Solution
The use of an electrolyte additive mixture containing diethyl allylphosphonate and 4-fluorobiphenyl, or 1-phenyl-1-cyclohexene, or a combination thereof, to mitigate overcharge responses and delay the onset of thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-ion batteries operate at high voltages and high specific energies, then energy density and power output are improved, but overcharge responses such as lithium plating, electrolyte breakdown, and thermal runaway occur more readily
Solution Approach 1:
The patent applies preliminary action by introducing overcharge additives (diethyl allylphosphonate combined with 4-fluorobiphenyl or 1-phenyl-1-cyclohexene) into the electrolyte before overcharge conditions occur. These additives proactively form protective films on electrode surfaces and preemptively inhibit harmful reactions, thereby delaying thermal runaway and mitigating overcharge damage while allowing the battery to operate at high energy densities
Solution Approach 2:
The patent employs composite materials by combining diethyl allylphosphonate with either 4-fluorobiphenyl or 1-phenyl-1-cyclohexene to create a synergistic additive system. This composite approach leverages the complementary properties of each component: diethyl allylphosphonate forms stable surface films, while the fluorobiphenyl or cyclohexene derivatives provide additional thermal stability and overcharge protection, together delivering enhanced reliability at high voltages
2Power
If overcharging occurs, then cell potential and temperature increase, but this leads to electrolyte breakdown, separator melting, and thermal runaway
Solution Approach 1:
The patent implements beforehand cushioning by incorporating overcharge additives that create protective barriers and absorb excess energy before thermal runaway can initiate. The diethyl allylphosphonate and its partner additives cushion the impact of overcharge by forming stable surface layers that prevent direct contact between electrolyte and electrodes under extreme conditions, delaying thermal runaway and reducing the severity of temperature spikes
Solution Approach 2:
The patent applies blessing in disguise by utilizing the overcharge conditions themselves to trigger beneficial protective mechanisms. When overcharging occurs, the additives undergo controlled reactions that form protective films and release heat in a controlled manner, converting the harmful overcharge energy into beneficial protective layers that prevent catastrophic failure
Data Source
AI summary
An electrochemical cell including an additive mixture for alleviating the symptoms of overcharge is disclosed. The additive mixture may include a combination of at least two of diethyl allylphosphonate, 4-fluorobiphenyl, and 1-phenyl-1-cyclohexene. For example, an electrolyte may include allylphosphonate and 4-fluorobiphenyl. In yet another example, an electrolyte may include 1-phenyl-1-cyclohexene.