LiMPO4 Cathode Crystal Orientation for Lower-Resistance Li-Ion Batteries
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Solution Overview
Problem
Lithium-containing composite oxides in lithium ion secondary batteries have high resistance, limiting the increase of discharge capacity and energy density.
Innovation Solution
A lithium ion secondary battery design featuring a positive electrode with a flat single crystal lithium-containing composite oxide (LiMPO4) where the b-axis of the olivine structured particles intersects with the current collector at an angle, allowing easier lithium ion migration and reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium-containing composite oxides with conventional particle structures are used, then the battery structure is simple and manufacturing is easy, but the internal resistance is high which limits discharge capacity and energy density
Solution Approach 1:
The patent changes the crystallographic orientation parameters of lithium-containing composite oxide particles, specifically controlling the intersection angle between the b-axis and current collector surface to be between 30-60 degrees. This parameter change optimizes lithium ion diffusion pathways, reducing internal resistance and increasing discharge capacity without fundamentally altering the manufacturing process complexity
Solution Approach 2:
The patent uses composite lithium-containing composite oxides with olivine structure (LiMPO4 where M is Fe, Mn, Co, Ni) that combine specific crystal structures with controlled particle morphology. The composite nature of these materials allows simultaneous optimization of electrical conductivity, ion diffusion, and structural stability to achieve high discharge capacity
2Productivity
If the b-axis of lithium-containing composite oxide particles is oriented perpendicular to the current collector surface, then lithium ion diffusion is maximized, but the manufacturing precision required to achieve this orientation is extremely high
Solution Approach 1:
Instead of requiring perfect perpendicular orientation (90 degrees), the patent applies partial action by accepting an orientation range of 30-60 degrees intersection angle. This partial orientation control achieves sufficient lithium ion diffusion enhancement while dramatically reducing manufacturing precision requirements, making the process industrially feasible
Solution Approach 2:
The patent incorporates orientation control mechanisms during the slurry coating process itself, rather than requiring post-processing alignment. By preliminary orienting particles during application to the current collector, the desired 30-60 degree intersection angle is achieved naturally through process parameters rather than precise post-manufacturing adjustment
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 enhances discharge capacity and power output by facilitating lithium ion diffusion, resulting in a battery with higher theoretical discharge capacity and reduced internal resistance.
Implementation Method 1
facilitating lithium ion diffusion
Data Source
AI summary
A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer over the positive electrode current collector. The positive electrode active material layer includes a plurality of lithium-containing composite oxides each of which is expressed by LiMPO4 (M is one or more of Fe (II), Mn (II), Co (II), and Ni (II)) that is a general formula. The lithium-containing composite oxide is a flat single crystal particle in which the length in the b-axis direction is shorter than each of the lengths in the a-axis direction and the c-axis direction. The lithium-containing composite oxide is provided over the positive electrode current collector so that the b-axis of the single crystal particle intersects with the surface of the positive electrode current collector.