Non-Aqueous Electrolyte Additive for Low-Resistance SEI Formation
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Solution Overview
Problem
Existing non-aqueous electrolytes for lithium secondary batteries suffer from an increase in electrical resistance during repeated charge/discharge cycles, particularly when using silicon-containing negative electrode materials.
Innovation Solution
Incorporating a non-aqueous electrolyte containing a bismaleimide compound with a specific chemical structure, such as 1,5-bis(maleimide)-2-methylpentane, to form a high-quality solid electrolyte interface (SEI) film on the negative electrode surface, inhibiting resistance increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylene carbonate is used as an electrolyte additive to form SEI film, then the SEI film formation is improved, but the internal resistance of the battery increases
Solution Approach 1:
The patent changes the chemical structure parameters of the cyclic carbonate additive by introducing fluorine atoms at specific positions (using compounds with formulas (1) and (2) where R1-R6 are specific combinations of H, F, and alkyl groups). This structural modification allows the additive to form SEI films with different properties compared to conventional vinylene carbonate, achieving both good film formation and low resistance characteristics.
Solution Approach 2:
The patent uses composite electrolyte formulations combining fluorinated cyclic carbonate compounds with other carbonate solvents (cyclic and chain carbonates) and lithium salts. This composite approach creates a synergistic effect where the fluorinated additive provides protective SEI film formation while the carbonate solvents maintain ion conductivity, resolving the contradiction between film quality and resistance.
2Quantity of substance
If silicon-containing material is used as negative electrode active material to improve capacity density, then the theoretical capacity is increased, but the volume change during charge/discharge increases
Solution Approach 1:
The fluorinated cyclic carbonate compound acts as a protective agent that预先 forms a stable SEI film on the silicon-containing negative electrode surface before significant volume changes occur. This pre-formed film accommodates the volume expansion and contraction of silicon during lithiation and delithiation, preventing electrode degradation and maintaining structural stability throughout charge/discharge cycles.
Solution Approach 2:
The SEI film formed by the fluorinated cyclic carbonate compound acts as a flexible protective layer that can accommodate the volume changes of silicon during charge/discharge. This thin film structure allows the electrode to expand and contract while maintaining integrity, solving the volume stability problem of silicon-based high-capacity materials.
3Use of energy by moving object
If charge voltage is increased to provide higher energy density, then the energy density is improved, but the electrolyte decomposition and resistance increase may worsen
Solution Approach 1:
The fluorinated cyclic carbonate compound performs preliminary protective action by forming a stable SEI film on the electrode surfaces before high-voltage operation begins. This pre-formed protective layer prevents direct contact between the electrolyte and electrodes at high voltages, inhibiting decomposition reactions and maintaining electrolyte stability even when charged to high voltages for increased energy density.
Solution Approach 2:
The patent modifies the electrolyte composition parameters by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (formulas (1) and (2)). These structural changes in the additive enable the electrolyte to form more stable SEI films that can withstand higher voltages, allowing the battery to operate at increased charge voltages for higher energy density without excessive decomposition or resistance 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 SEI film formed by the bismaleimide compound effectively reduces battery resistance during charge/discharge cycles, maintaining battery performance over time.
Implementation Method 1
an electrolyte ingredient-derived coating film called 'solid electrolyte interface (SEI)' film is formed on the negative electrode surface
Implementation Method 2
The electrolyte is decomposed through reduction, and the decomposition product is deposited on the surface of a negative electrode
Implementation Method 3
An electrolyte plays a role in ion conduction to operate a battery
Data Source
AI summary
Provided is a non-aqueous electrolyte capable of inhibiting an increase in battery resistance when repeating charge/discharge cycles. The non-aqueous electrolyte includes a compound represented by the following Chemical Formula 1:wherein R1 represents a C3-C20 linear or branched alkylene group, and each of R2 to R5 independently represents a hydrogen atom, a halogen atom or a C1-C5 alkyl group.