Lithium Battery Electrolyte Additives for High-Ni Cathode Stability

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Solution Overview

Problem

Lithium secondary batteries with high Ni content in NCM-based positive electrode materials face challenges in maintaining long-life performance due to interfacial reactivity and structural instability, leading to performance degradation and capacity retention issues during repeated charge and discharge cycles.

Innovation Solution

Incorporating a borate-based salt compound and vinyl carbonate additives in the electrolyte solution to form a protective SEI layer on the positive electrode, stabilizing the electrode surface and preventing electrolyte oxidation and decomposition, thereby enhancing electrochemical properties and capacity retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the content of Ni in NCM-based positive electrode material is increased to achieve higher capacity, then the capacity of the lithium secondary battery is improved, but the interfacial reactivity increases and crystal structure stability decreases, leading to accelerated deterioration

Engineering Contradiction:

ImprovecapacityVSAvoidlong life performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A borate-based salt compound (Formula 1) is introduced as an intermediary substance in the electrolyte solution that mediates the interaction between the high-Ni NCM positive electrode and the electrolyte. This compound forms a stable protective film on the electrode surface, reducing direct contact and harmful reactions between the reactive Ni-rich material and the electrolyte, thereby maintaining both high capacity and long cycle life

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte solution by incorporating a specific borate-based salt compound with controlled amounts (0.1-4 wt%). This parameter change modifies the electrolyte's interaction characteristics with the high-Ni electrode, enabling stable operation at high capacities without sacrificing reliability

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If the content of Ni in NCM-based positive electrode material is increased to achieve higher capacity, then the capacity of the lithium secondary battery is improved, but the crystal structure stability decreases, causing performance degradation during repeated charge and discharge cycles

Engineering Contradiction:

ImprovecapacityVSAvoidNCM crystal structure stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The borate-based salt compound provides beforehand cushioning by forming a stable protective film on the NCM positive electrode surface before structural degradation can occur. This pre-formed protective layer acts as a buffer that prevents electrolyte penetration and protects the Ni-rich crystal structure from degradation during repeated charge-discharge cycles, maintaining both high capacity and structural stability

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If conventional electrolyte additives are used to coat the surface of NCM positive electrode, then electrochemical performance is improved, but the long-term stability and capacity retention remain insufficient due to inadequate protection against interfacial reactivity

Engineering Contradiction:

Improveelectrochemical performanceVSAvoidcapacity retention

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The invention uses a composite approach by combining the borate-based salt compound (Formula 1) with vinyl carbonate (Formula 2) in the electrolyte solution. This composite additive system creates a more robust and stable protective film on the NCM electrode surface compared to single additives, simultaneously improving electrochemical performance and ensuring long-term capacity retention through enhanced interfacial stability

Inventive Principle:

Principle #40Composite materials

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 use of these additives significantly improves the electrochemical performance and capacity retention of lithium secondary batteries, especially at high temperatures and voltages, by forming a stable protective film on the positive electrode, reducing degradation and maintaining stable charge and discharge performance.

Implementation Method 1

Incorporating a borate-based salt compound and vinyl carbonate additives in the electrolyte solution to form a protective SEI layer on the positive electrode

Methodology Applied

Scientific EffectSEI layer formation:

Implementation Method 2

stabilizing the electrode surface and preventing electrolyte oxidation and decomposition

Methodology Applied

Scientific EffectOxidation prevention: Oxidation

Implementation Method 3

A lithium secondary battery produces electric energy by repeating insertion and desorption of lithium ions in a positive electrode and a negative electrode

Methodology Applied

Scientific EffectIon insertion and desorption:

Data Source

PatentUS12183886B2Electrolyte solution for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2024.12.31 HYUNDAI MOTOR CO LTD

AI summary

Disclosed are an electrolyte solution and an additive thereof, which may improve electrochemical properties of a lithium secondary battery.