LCO Battery Electrolyte Additives for High-Temperature Stability

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Solution Overview

Problem

Lithium cobalt oxide batteries face poor high-temperature performance due to lithium deintercalation leading to oxygen atom activity, electrolyte decomposition, and gas overflow, which worsens as charge cut-off voltage increases, posing safety and expansion issues.

Innovation Solution

An electrolyte comprising fluoroethylene carbonate and a P—N bond-containing compound, along with a sulfur-containing compound and phosphoric acid cyclic anhydride, is used to enhance the stability of the cathode surface, absorb oxygen, inhibit electrolyte decomposition, and improve high-temperature cycle and storage performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the charge cut-off voltage of LCO is increased to improve specific capacity, then the energy density is improved, but the high-temperature performance deteriorates due to increased oxygen atom activity and electrolyte decomposition

Engineering Contradiction:

Improvespecific capacityVSAvoidhigh-temperature performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a P—N bond-containing compound as an intermediary substance that mediates between the LCO cathode and the electrolyte. This compound forms a protective interface layer that prevents direct contact and harmful reactions between the electrolyte and oxygen atoms on the LCO surface, thereby enabling high charge cut-off voltages without suffering from electrolyte decomposition and gas overflow at high temperatures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite electrolyte system combining fluoroethylene carbonate (FEC) and P—N bond-containing compounds. This composite formulation creates a synergistic effect where FEC provides base electrolyte functionality while the P—N compound forms a stable protective film, allowing the battery to operate at high voltages (4.4V or higher) without the high-temperature performance degradation that would normally occur.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If lithium ions continue to deintercalate to increase capacity, then the energy density is improved, but gas overflow occurs due to lattice oxygen activity, causing safety problems and battery expansion

Engineering Contradiction:

Improveenergy densityVSAvoidgas overflow and safety issues

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The P—N bond-containing compound performs preliminary protective action by forming a stable interface film on the LCO surface before harmful reactions can occur. This pre-formed protective layer prevents oxygen atoms from becoming active and releasing gas during subsequent charging cycles at high voltages, thereby eliminating safety problems and battery expansion issues that would otherwise result from continuous lithium deintercalation.

Inventive Principle:

Principle #9Preliminary anti-action

3Quantity of substance

If the charge cut-off voltage is raised to allow more ions to participate in charging and discharging, then the capacity is improved, but the stability of Co atoms on the surface decreases, leading to dissolution and oxidation of the electrolyte

Engineering Contradiction:

ImprovecapacityVSAvoidsurface stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The P—N bond-containing compound acts as an intermediary protective layer between the LCO surface and the electrolyte. This intermediate film stabilizes the surface composition by preventing direct interaction between electrolyte components and oxygen atoms, thereby maintaining surface stability even when operating at high charge cut-off voltages that would otherwise cause Co atom dissolution and electrolyte oxidation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 electrolyte formulation improves the stability of the cathode surface, reduces gas production, and significantly enhances the high-temperature cycle and storage performance of lithium ion batteries by forming a protective film and maintaining interface stability.

Implementation Method 1

the compound can also absorb oxygen released from a cathode, inhibit electrolyte decomposition

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

improves the stability of the cathode surface... by forming a protective film and maintaining interface stability

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Data Source

PatentUS20230361349A1Electrolyte, electrochemical device and electronic device

Publication Date: 2023.11.09 NINGDE AMPEREX TECHNOLOGY LTD

AI summary

An electrolyte includes an organic solvent, a lithium salt and additives, in particular, the additives include a fluoroethylene carbonate and a P—N bond-containing compound, the P—N bond-containing compound having a structure shown in formula I; A mass percentage of the fluoroethylene carbonate in the electrolyte is a %, a mass percentage of the P—N bond-containing compound in the electrolyte is b %, and 0.1≤a/b≤200.