Dual-Coated Positive Electrode Material for Stable High-Energy Cells
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density and capacity, with existing positive electrode active materials often relying on cobalt, which can lead to structural instability and reduced performance over time.
Innovation Solution
A positive electrode active material comprising first and second lithium composite oxides with specific coating layers, where the first particles are coated with aluminum and the second particles are coated with cobalt, providing a mixture with improved structural stability and performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cobalt is used in lithium composite oxide to achieve high capacity, then energy density is improved, but structural stability deteriorates leading to reduced lifetime
Solution Approach 1:
The patent applies different coating materials to particles of different sizes: small particles (≤10 μm) are coated with cobalt to enhance capacity, while large particles (>10 μm) are coated with aluminum to maintain structural stability. This local differentiation resolves the contradiction by allowing cobalt to provide energy density benefits where it matters most (small particles with high surface area) while aluminum provides structural stability where needed (large particles that form the bulk structure).
Solution Approach 2:
The patent creates a composite particle system where cobalt-coated small particles are embedded within or mixed with aluminum-coated large particles. This composite structure allows the system to simultaneously achieve the high capacity benefits of cobalt and the structural stability benefits of aluminum, resolving the contradiction between energy density and structural stability.
2Productivity
If particle size is reduced to increase surface area for lithium ion intercalation, then charge-discharge efficiency is improved, but structural collapse increases reducing lifetime
Solution Approach 1:
The patent segments the particle size distribution into two distinct groups: small particles (≤10 μm) that provide high surface area for efficient lithium ion intercalation, and large particles (>10 μm) that provide structural stability. The segmentation allows each size fraction to fulfill its specific function without suffering from the drawbacks of the other.
Solution Approach 2:
Different coating strategies are applied to different particle size ranges: cobalt coating on small particles to maximize capacity utilization, and aluminum coating on large particles to prevent structural collapse. This local quality differentiation resolves the contradiction between charge-discharge efficiency and lifetime.
3Use of energy by moving object
If high nickel content is used to achieve high capacity, then energy density is improved, but structural stability deteriorates
Solution Approach 1:
The patent uses composite materials by combining high-nickel lithium composite oxide with dual coating layers of aluminum and cobalt. The aluminum coating provides structural stability to the nickel-rich core, while the cobalt coating enhances capacity. This composite structure allows high nickel content to achieve high energy density without sacrificing structural stability.
Solution Approach 2:
The patent changes the coating composition parameters based on particle size: aluminum coating for structural stability and cobalt coating for capacity enhancement. By adjusting these coating parameters, the patent enables high nickel content materials to achieve both high energy density and maintained structural stability.
4Duration of action of moving object
If aluminum coating is applied to suppress structural collapse, then lifetime is improved, but charge-discharge efficiency may be reduced due to lower conductivity
Solution Approach 1:
The patent applies aluminum coating selectively to large particles (>10 μm) where structural stability is most needed, while applying cobalt coating to small particles (≤10 μm) where conductivity and capacity are prioritized. This local quality differentiation ensures aluminum provides lifetime benefits without unnecessarily reducing overall charge-discharge efficiency.
Solution Approach 2:
The patent creates a composite coating system where aluminum and cobalt work together: aluminum provides structural stability and prevents collapse, while cobalt provides high conductivity and capacity. This composite coating material resolves the contradiction between lifetime improvement and charge-discharge efficiency maintenance.
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 active material enhances the lifetime and charge-discharge efficiency of lithium batteries by suppressing structural collapse and side reactions, leading to improved high-temperature stability and increased energy density.
Implementation Method 1
Each of the first particles may further include a first coating layer on a surface of the first lithium composite oxide. Each of the second particles may further include a second coating layer on a surface of the second lithium composite oxide. The first coating layer may include aluminum. The second coating layer may include cobalt.
Implementation Method 2
A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte, which positive and negative electrodes include an active material in which intercalation and deintercalation of lithium ions are possible, and generates electrical energy caused by oxidation and reduction reactions.
Data Source
AI summary
Disclosed are positive electrode active materials and rechargeable lithium batteries. The positive electrode active material comprises a first particle that includes a first lithium composite oxide and has a first average particle diameter, and a second particle that includes a second lithium composite oxide and has a second average particle diameter less than the first average particle diameter. The first particle further includes a first coating layer on a surface of the first lithium composite oxide. The second particle further includes a second coating layer on a surface of the second lithium composite oxide. Each of the first and second lithium composite oxides is lithium composite oxide that includes nickel (Ni) and excludes cobalt (Co). The first coating layer includes aluminum (Al). The second coating layer includes cobalt (Co).