Li-Ion Secondary Battery Electrolyte for High-Voltage Cycle Stability

Solution Overview

Problem

Lithium-ion secondary batteries face challenges in achieving high capacity, excellent charge and discharge cycle performance, rapid charging, and safety at high temperatures, with issues related to capacity reduction and transition metal elution during high-voltage charging.

Innovation Solution

A secondary battery design incorporating lithium cobalt oxide with an O3 structure and an imidazolium cation electrolyte, where the battery undergoes specific charging and discharging cycles at controlled temperatures, and the use of a negative electrode with a high graphite content to suppress transition metal elution and maintain crystal structure stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If high voltage charging is performed to increase capacity, then energy density is improved, but transition metal elution occurs and crystal structure stability deteriorates

Engineering Contradiction:

Improveenergy densityVSAvoidcrystal structure stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A coating layer comprising at least one of an oxide, a hydroxide, a carbonate, or a mixture thereof of a rare earth element is formed on the surface of the lithium cobalt oxide particle. This coating layer acts as an intermediary barrier that prevents direct contact between the lithium cobalt oxide and the electrolyte, thereby suppressing transition metal elution and maintaining crystal structure stability during high voltage charging while allowing high capacity operation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If high voltage charging is performed to increase capacity, then energy density is improved, but transition metal elution into electrolyte increases

Engineering Contradiction:

Improveenergy densityVSAvoidtransition metal elution

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

A coating layer comprising at least one of an oxide, a hydroxide, a carbonate, or a mixture thereof of a rare earth element is formed on the surface of the lithium cobalt oxide particle. This coating layer acts as an intermediary barrier that prevents direct contact between the lithium cobalt oxide and the electrolyte, thereby suppressing transition metal elution and maintaining crystal structure stability during high voltage charging while allowing high capacity operation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If rapid charging is performed to improve charging speed, then charging time is reduced, but heat generation increases and safety deteriorates

Engineering Contradiction:

Improvecharging speedVSAvoidheat generation

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

A coating layer comprising at least one of an oxide, a hydroxide, a carbonate, or a mixture thereof of a rare earth element is formed on the surface of the lithium cobalt oxide particle. This coating layer acts as an intermediary barrier that prevents direct contact between the lithium cobalt oxide and the electrolyte, thereby suppressing transition metal elution and maintaining crystal structure stability during high voltage charging while allowing high capacity operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The use of rare earth element coatings modifies the surface properties and electrochemical parameters of the positive electrode active material, enabling stable operation at high voltages and temperatures. This allows the battery to withstand the conditions generated during rapid charging without excessive heat generation or degradation

Inventive Principle:

Principle #35Parameter changes

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 results in a battery with high capacity, excellent cycle performance, rapid charging capabilities, and enhanced safety and reliability, even at high temperatures, by preventing capacity reduction and transition metal elution, thereby extending the battery's lifespan and energy density.

Implementation Method 1

an electrolyte including an imidazolium cation

Methodology Applied

Scientific EffectIon transport: Electrolysis

Implementation Method 2

lithium cobalt oxide that is a surface portion of the positive electrode active material particle has an O3 structure

Methodology Applied

Scientific EffectLithium ion insertion/extraction: Absorption (physical)

Data Source

PatentUS20230378459A1Secondary battery, electronic device, and vehicle

Publication Date: 2023.11.23 SEMICON ENERGY LAB CO LTD

AI summary

A lithium-ion secondary battery having high capacity and excellent charge and discharge cycle performance is provided. A secondary battery having high capacity is provided. A secondary battery with excellent charge and discharge characteristics is provided. A secondary battery in which a reduction in capacity is suppressed even when a state being charged with a high voltage is held for a long time is provided. In the secondary battery, after constant current charging is performed in an environment at 60° C. with a current value of 0.5 C until a voltage reaches 4.5 V, a charging process of performing constant voltage charging until a current value reaches 0.2 C and a discharging process of performing constant current discharging with a current value of 0.5 C until a voltage reaches 3 V are alternately repeated 150 or more times, and then discharging is performed, lithium cobalt oxide that is a surface portion of the positive electrode active material particle has an O3 structure, and an electrolyte includes an imidazolium cation.