Secondary Battery Electrode with Layered Active Materials
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Solution Overview
Problem
Conventional secondary batteries face challenges in achieving high volumetric energy density and volumetric output density, which are essential for extending the running distance and performance of electric vehicles, as fine processing of electrode active materials increases electrode volume and decreases energy density.
Innovation Solution
The use of spinel-structured lithium manganate and a composite oxide with a specific chemical formula (LiCovNiXMnYMZO2) as electrode active materials, where the composite oxide has a smaller average particle diameter than the spinel-structured lithium manganate, arranged in two layers to enhance both energy and output density, with the composite oxide providing a two-dimensional lithium diffusion route and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the average particle diameter of electrode active material is reduced to enhance electron conductivity and lithium ion diffusibility, then the electrode reaction area increases and output density improves, but the electrode volume increases and volumetric energy density decreases
Solution Approach 1:
The electrode active material layer is divided into two distinct layers: a first layer containing spinel-structured lithium manganate with larger particle diameter (3 μm or more) for high energy density, and a second layer containing composite oxide with smaller particle diameter (0.3 to 3 μm) for high output density. This segmentation allows each layer to specialize in different functions, resolving the contradiction between volume and performance.
Solution Approach 2:
Different regions of the electrode are assigned different material compositions and particle sizes optimized for their specific functions. The first layer (larger particles) is optimized for energy storage capacity, while the second layer (smaller particles) is optimized for rapid electron conductivity and lithium ion diffusibility. This local optimization allows the electrode as a whole to achieve both high energy density and high output density.
2Power
If the thickness of electrode active material layer is reduced to enhance electron conductivity and lithium ion diffusibility, then the electrode reaction area increases and output density improves, but the volumetric energy density decreases
Solution Approach 1:
The electrode active material layer is segmented into two layers with different thicknesses and compositions. The first layer has greater thickness and contains larger particles for energy storage, while the second layer has smaller thickness and contains smaller particles for rapid reaction. This segmentation resolves the contradiction between layer thickness and performance.
Solution Approach 2:
The electrode uses a composite structure combining two different active materials: spinel-structured lithium manganate in the first layer and composite oxide (LiCovNiXMnYMZO2) in the second layer. This composite material approach allows the electrode to simultaneously achieve high energy density from the first layer and high output density from the second layer, resolving the contradiction between energy density and output density.
3Power
If fine processing of electrode active material is performed to increase electrode reaction area, then output density improves, but volumetric energy density decreases
Solution Approach 1:
Fine processing (small particle diameter) is applied locally to the second layer containing composite oxide, where it enhances electron conductivity and lithium ion diffusibility. The first layer retains larger particle sizes optimized for energy storage. This localized application of fine processing resolves the contradiction between output density and volumetric energy density.
Solution Approach 2:
The electrode employs a composite structure where fine-processed composite oxide particles (0.3 to 3 μm) in the second layer provide high output density through enhanced conductivity and diffusibility, while the coarser spinel-structured lithium manganate particles (3 μm or more) in the first layer maintain high volumetric energy density. This composite material strategy resolves the contradiction between fine processing benefits and volumetric efficiency.
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
This configuration enhances volumetric output density while maintaining volumetric energy density, suppressing internal resistance increase due to electrode material deterioration, and ensuring excellent performance at high temperatures.
Implementation Method 1
the composite oxide having a two-dimensional lithium diffusion route
Implementation Method 2
positive and negative electrodes capable of occluding and emitting Li ions
Data Source
AI summary
A secondary battery electrode, which is formed by stacking an electrode active material layer (I) containing spinel-structured lithium manganate as an electrode active material and an electrode active material layer (II) containing, as an electrode active material, a composite oxide represented by the following Chemical formula (1) in a thickness direction of the electrode, in which the electrode active material layer (I) is disposed in contact with a current collector, and an average particle diameter of the composite oxide is smaller than an average particle diameter of the spinel-structured lithium manganate. In such a way, it is possible to provide a secondary battery electrode capable of realizing a secondary battery excellent in both of a volumetric energy density and a volumetric output density.LiCovNiXMnYMZO2 (1)