Nonaqueous Electrolyte Additives for Lithium Battery Capacity Retention

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Solution Overview

Problem

Nonaqueous electrolyte rechargeable batteries face capacity deterioration due to irreversible lithium reactions, which reduce their durability and energy density over time, especially in applications like electric vehicles.

Innovation Solution

Incorporating an organic solvent with a donor number of 18 to 24 and a polycyclic aromatic hydrocarbon into the electrolyte, which reduces lithium incorporation into the coating and stabilizes solvated lithium ions, thereby enhancing the battery's charging and discharging capacity and output density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the total amount of lithium is increased by using a high capacity positive electrode, then the initial capacity is improved, but the capacity eventually reduces due to irreversible reactions

Engineering Contradiction:

Improvetotal amount of lithiumVSAvoidcapacity durability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A lithium salt of a specific carboxylic acid (having 3-7 carbon atoms) is introduced as an intermediary substance in the electrolyte. This intermediary forms a protective interface layer that mediates between the lithium ions and the electrode coating, preventing direct harmful interactions while allowing lithium transport, thus reducing irreversible capacity loss over cycles

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte by selecting a specific carboxylic acid lithium salt with controlled carbon chain length (3-7 atoms). This parameter optimization balances the salt's solubility, dissociation characteristics, and ability to form stable protective films, thereby improving long-term capacity retention while maintaining initial capacity

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If a high capacity positive electrode is used to compensate for irreversible capacity, then the initial energy density is improved, but the weight of unused positive electrode material increases

Engineering Contradiction:

Improveenergy densityVSAvoidweight of positive electrode active material

Core Design Contradiction:

Use of energy by moving objectVSWeight of moving object

Solution Approach 1:

The carboxylic acid lithium salt acts as a mediator that reduces the extent of irreversible lithium consumption. By forming a stable protective interface, it allows the battery to achieve higher effective capacity utilization, meaning less excess positive electrode material is needed to compensate for initial lithium loss, thereby improving energy density without proportionally increasing weight

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If the amount of lithium is increased to account for irreversible reactions, then the initial capacity is maintained, but the capacity deterioration accelerates over time

Engineering Contradiction:

Improveamount of lithiumVSAvoidbattery lifetime

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The carboxylic acid lithium salt introduces a protective intermediary layer that fundamentally changes the interaction mechanism between lithium ions and electrode surfaces. This intermediary prevents direct detrimental reactions, allowing the battery to utilize a smaller lithium excess while achieving better long-term stability and extended operational lifetime

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the typically harmful irreversible lithium reactions into a beneficial process by controlling the initial formation reactions through the carboxylic acid salt. The controlled initial reactions create a stable protective film that subsequently prevents further harmful reactions, turning the initial capacity loss into a protective mechanism that extends battery lifetime

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively restricts lithium consumption and improves the battery's durability and output performance by reducing irreversible reactions, maintaining capacity and energy density over long cycles.

Implementation Method 1

The nonaqueous electrolyte contains an additive and a polycyclic aromatic hydrocarbon. The additive includes an organic solvent having a donor number of 18 to 24

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 2

The nonaqueous electrolyte contains an additive and a polycyclic aromatic hydrocarbon. A content of the polycyclic aromatic hydrocarbon is 0.1% to 2.0% of a total mass of the nonaqueous electrolyte

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentUS9276288B2Nonaqueous electrolyte rechargeable battery

Publication Date: 2016.03.01 DENSO CORP

AI summary

A nonaqueous electrolyte rechargeable battery includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode and the negative electrode occlude and discharge lithium irons. The nonaqueous electrolyte contains an additive and a polycyclic aromatic hydrocarbon. The additive includes an organic solvent having a donor number of 18 to 24. A content of the polycyclic aromatic hydrocarbon is 0% to 2.0% of a total mass of the nonaqueous electrolyte.