Cathode Active Material Surface Doping for Low-Temperature Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium ion batteries suffer from reduced discharge capacity and energy density in low-temperature environments, necessitating the development of suitable positive electrode materials and electrolytes to maintain high performance in such conditions.
Innovation Solution
A positive electrode active material composed of cobalt, oxygen, magnesium, and aluminum with a layered rock-salt crystal structure, along with an electrolyte containing lithium hexafluorophosphate, ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, optimized for low-temperature operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials are used, then the battery can operate at high temperatures, but the discharge capacity and energy density are significantly reduced in low-temperature environments
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface portion (shell) has different compositional characteristics from the inner portion (core). The surface portion contains elements like aluminum, magnesium, or lithium that specifically address low-temperature interface reactions, while the inner portion maintains high-capacity materials like lithium cobalt oxide or lithium nickel manganese cobalt oxide. This local differentiation allows the battery to maintain high discharge capacity in low-temperature environments while preserving overall energy density.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (cobalt, nickel, manganese, aluminum, magnesium, lithium) in specific ratios within the positive electrode active material. The composite structure, particularly the core-shell configuration with distinct compositional regions, enables the material to exhibit both high-capacity characteristics from the inner portion and low-temperature performance from the surface portion, thereby resolving the contradiction between reliability in cold environments and discharge capacity.
2Quantity of substance
If the positive electrode active material is optimized for high discharge capacity, then energy density improves, but the material becomes less stable in low-temperature conditions
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable surface layer or coating on the positive electrode active material before battery operation. This surface portion, enriched with elements like aluminum or magnesium, is designed to stabilize the material composition and prevent degradation reactions that would otherwise occur in low-temperature environments. By preparing this protective layer in advance, the high-capacity inner material can maintain both its discharge capacity and compositional stability when exposed to cold conditions.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the compositional parameters of the positive electrode active material, specifically controlling the ratios of cobalt, nickel, manganese, aluminum, and magnesium in the surface portion versus the inner portion. By optimizing these compositional parameters and the thickness of the surface layer, the material achieves a balance where high discharge capacity from the inner high-nickel region is maintained while the surface composition parameters are tuned to ensure stability in low-temperature environments.
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 proposed solution enables lithium ion batteries to maintain high discharge capacity and energy density, with reduced capacity and energy density loss in low-temperature environments, while ensuring safety and reliability.
Implementation Method 1
a positive electrode active material containing cobalt, oxygen, magnesium, aluminum, and nickel... The positive electrode active material includes the magnesium and the aluminum in a surface portion
Implementation Method 2
The positive electrode active material includes the magnesium and the aluminum in a surface portion... When the positive electrode active material is subjected to EDX line analysis in a depth direction, the positive electrode active material includes a region where the magnesium is distributed closer to a surface side of the positive electrode active material than the aluminum is
Data Source
AI summary
A lithium ion battery having excellent charge performance and discharge performance even in a low-temperature environment is provided. A lithium ion battery includes a positive electrode active material containing cobalt, oxygen, magnesium, aluminum, and nickel. The median diameter of the positive electrode active material is greater than or equal to 1 μm and less than or equal to 12 μm. Magnesium and aluminum are included in a surface portion. The surface portion is a region within 50 nm in depth from the surface of the positive electrode active material. The positive electrode active material includes a region where magnesium is distributed closer to the surface side of the positive electrode active material than aluminum is.