Lithium-Ion Cathode Layering for Low-SOC Resistance and Gas Control
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Solution Overview
Problem
Conventional lithium-ion secondary batteries exhibit high discharge resistance at low state of charge (SOC), especially at low temperatures, and generate excessive gases at high temperatures, leading to potential short circuits.
Innovation Solution
A lithium-ion secondary battery design featuring a positive electrode plate with a first and second active material layer, combined with a specific electrolyte conductivity, where the thickness ratio of the layers and electrolyte conductivity satisfy the condition −1≤log10(u/v)×w≤15.5, reducing discharge resistance and gas production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-layer positive electrode structure is used, then the battery structure is simple, but the discharge resistance is excessively large at low SOC and low temperature
Solution Approach 1:
The positive electrode active material layer is divided into two distinct layers: a first layer containing lithium-rich layered oxide material and a second layer containing spinel or olivine material. This segmentation allows each layer to contribute differently to the overall discharge performance, with the first layer providing high voltage plateau and the second layer maintaining stability at low SOC, thereby reducing discharge resistance without significantly increasing structural complexity.
2Temperature
If the battery is used or stored at high temperature, then the reactivity of electrodes with electrolyte is enhanced, but excessive gas is generated and battery volume expands
Solution Approach 1:
The positive electrode uses a composite structure combining lithium-rich layered oxide material in the first layer with spinel or olivine material in the second layer. This composite material approach leverages the high voltage characteristics of lithium-rich materials while the spinel/olivine components provide structural stability and reduced reactivity with electrolyte at high temperatures, thereby suppressing gas generation even when the battery is used or stored at elevated temperatures.
3Use of energy by moving object
If lithium-rich layered oxide material is used to achieve high voltage plateau, then energy density is improved, but discharge resistance increases at low SOC
Solution Approach 1:
The patent applies local quality by placing different materials in different positions within the electrode structure. The lithium-rich layered oxide material (providing high energy density) is positioned in the first layer, while the spinel or olivine material (providing low discharge resistance at low SOC) is positioned in the second layer. This spatial differentiation of material properties allows both high energy density and low discharge resistance to be achieved simultaneously in different regions of the electrode.
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 battery achieves significantly reduced discharge resistance at low SOC, improved high-temperature gas production performance, and cost efficiency, facilitating mass production with a simpler process.
Implementation Method 1
w is a conductivity of the electrolyte at a temperature of 25° C. in mS·cm−1
Data Source
AI summary
A lithium-ion secondary battery and related preparation method thereof, battery module, battery pack and apparatus. The lithium-ion secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the positive electrode plate includes a positive electrode current collector and a first positive electrode active material layer and a second positive electrode active material layer sequentially disposed on at least one side of the positive electrode current collector; the lithium-ion secondary battery satisfies: −1≤log10(u/v)×w≤15.5, wherein, u is a thickness of the first positive electrode active material layer in microns, v is a thickness of the second positive electrode active material layer in microns, w is a conductivity of the electrolyte at a temperature of 25° C. in mS·cm−1. The lithium-ion secondary battery has excellent performance such as low discharge resistance at low SOC and low gas production at high temperature.