Cathode Composition and Carbon Collector for Thermal Runaway Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium cobalt oxide-based batteries face safety concerns due to thermal runaway issues, particularly during nail penetration tests, where internal short circuits can lead to high temperatures and thermite reactions with aluminum current collectors, causing fires.
Innovation Solution
A battery design featuring a carbon sheet positive electrode current collector with carbon nanotubes, where the carbon sheets are oriented orthogonally, and a positive electrode active material with a surface layer containing lithium cobalt oxide, nickel, and magnesium, with a concentration gradient of nickel and magnesium to enhance stability and prevent thermite reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium cobalt oxide with layered rock-salt crystal structure is used to enable high capacity, then the battery capacity is improved, but the safety deteriorates due to crystal structure collapse and thermal runaway
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of nickel and magnesium elements within the lithium cobalt oxide crystal structure. The surface region has higher concentrations of nickel and magnesium compared to the interior, providing localized structural stabilization at the critical surface region where phase changes initiate, while maintaining high lithium ion capacity in the bulk material.
Solution Approach 2:
The patent creates a composite positive electrode active material by incorporating nickel and magnesium elements into the lithium cobalt oxide structure. This composite approach forms a multi-element compound (LiCo1-x-yNixMgyO2) that combines the high capacity characteristics of lithium cobalt oxide with the structural stability provided by nickel and magnesium, preventing crystal collapse during charging cycles.
2Quantity of substance
If high charge voltage is applied to extract more lithium ions for high capacity, then the battery capacity is improved, but the crystal structure collapses leading to thermal runaway
Solution Approach 1:
The concentration gradient structure provides localized structural reinforcement at the surface region where phase changes first occur during charging. The higher nickel and magnesium content at the surface stabilizes the crystal structure against collapse, enabling deeper lithium ion extraction at high charge voltages without triggering thermal runaway.
Solution Approach 2:
The patent changes the compositional parameters of the positive electrode active material by introducing nickel and magnesium elements with specific ionic radii that differ from cobalt. This parameter change stabilizes the crystal lattice dimensions and reduces the tendency for phase transitions during lithium ion extraction, allowing operation at higher charge voltages.
3Power
If aluminum is used as positive electrode current collector for good conductivity, then the electrical conductivity is improved, but thermite reactions occur at high temperatures causing fires
Solution Approach 1:
The patent introduces a protective coating layer as an intermediary between the aluminum current collector and the positive electrode active material. This coating acts as a physical barrier that prevents direct contact between aluminum and lithium cobalt oxide, thereby preventing thermite reactions while maintaining electrical conductivity through the coating layer.
Solution Approach 2:
The patent converts the potential harm of aluminum's reactivity at high temperatures into a benefit by using aluminum's high electrical conductivity while protecting it from thermal runaway through the stable surface region of the positive electrode active material. The nickel-magnesium stabilized surface prevents the temperature rise that would trigger thermite reactions, allowing aluminum's conductive properties to be fully utilized.
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 design significantly reduces the risk of thermal runaway and enhances safety by preventing thermite reactions, maintaining high discharge capacity and stability even under high charge voltages.
Implementation Method 1
The positive electrode current collector is a carbon sheet... maintaining high discharge capacity and stability
Implementation Method 2
lithium ions can move two-dimensionally between layers composed of CoO6 octahedrons
Implementation Method 3
when an internal short circuit occurs by a nail penetration test or the like, Joule heat is generated to make lithium cobalt oxide have high temperatures
Data Source
AI summary
A positive electrode active material that inhibits a decrease in discharge capacity in charge and discharge cycles and a battery using the positive electrode active material are provided. A high-safety battery is provided. The battery includes a positive electrode including a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is a carbon sheet. The positive electrode active material contains lithium cobalt oxide containing nickel and magnesium. The detected amount of nickel in a surface portion of the positive electrode active material is larger than that in an inner portion of the positive electrode active material. The detected amount of magnesium in the surface portion of the positive electrode active material is larger than the detected amount of magnesium in the inner portion of the positive electrode active material. The surface portion in the positive electrode active material includes a region where the distribution of nickel and the distribution of magnesium overlap with each other.