High-Nickel Cathode Composition With Phosphate Surface Protection
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Solution Overview
Problem
High-Ni-containing lithium transition metal composite oxides in positive electrodes of non-aqueous electrolyte secondary batteries face challenges in improving discharge capacity, as they tend to be structurally unstable and prone to surface degradation, leading to reduced capacity and conductivity issues.
Innovation Solution
Incorporating at least one of Ca or Sr into the positive electrode active material and adding a phosphate, such as lithium phosphate, to enhance particle strength and form a protective coating film, thereby improving discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content ratio of Ni in the lithium transition metal composite oxide is increased to obtain high discharge capacity, then the charge capacity is improved, but the discharge capacity cannot be improved due to structural instability and surface degradation
Solution Approach 1:
The patent changes the chemical composition parameters by adding Ca or Sr elements to the lithium transition metal composite oxide. This compositional modification stabilizes the crystal structure and suppresses surface degradation, allowing the high Ni content (≥75 mol%) to be maintained without suffering from structural instability, thereby resolving the contradiction between achieving high charge capacity and maintaining structural stability
Solution Approach 2:
The patent creates a composite material system by incorporating Ca or Sr into the lithium transition metal composite oxide matrix. This composite approach combines the high capacity benefits of Ni with the structural stability provided by Ca/Sr, enabling both improved charge capacity and maintained structural integrity during cycling
2Quantity of substance
If the content ratio of Ni in the lithium transition metal composite oxide is increased to obtain high discharge capacity, then the charge capacity is improved, but the discharge capacity is reduced due to surface degradation
Solution Approach 1:
The patent introduces Ca or Sr as intermediary elements that mediate between the high-Ni active material and the electrolyte environment. These intermediaries form stable surface phases that prevent direct contact and harmful reactions between the Ni-rich composite oxide and the electrolyte, thereby protecting the discharge capacity while maintaining high charge capacity
Solution Approach 2:
By modifying the compositional parameters (adding Ca/Sr), the patent changes the surface properties and electrochemical stability of the composite oxide, enabling it to maintain reliable discharge capacity even at high Ni content where surface degradation would normally occur
3Quantity of substance
If the content ratio of Ni in the lithium transition metal composite oxide is increased, then the charge capacity is improved, but conductivity issues arise due to structural instability
Solution Approach 1:
The patent modifies the structural parameters by incorporating Ca or Sr, which stabilize the crystal structure and maintain good conductivity pathways. This structural stabilization ensures that even with high Ni content (≥75 mol%) providing high charge capacity, the material maintains reliable electrical conductivity for electron and ion transport
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 addition of Ca or Sr and phosphate in the positive electrode mixture layer stabilizes the lithium transition metal composite oxide, reducing surface degradation and enhancing discharge capacity by forming a protective coating film that suppresses side reactions with the electrolyte.
Implementation Method 1
adding a phosphate, such as lithium phosphate, to enhance particle strength and form a protective coating film
Implementation Method 2
forming a protective coating film that suppresses side reactions with the electrolyte
Implementation Method 3
Incorporating at least one of Ca or Sr into the positive electrode active material and adding a phosphate, such as lithium phosphate, to enhance particle strength and form a protective coating film, thereby improving discharge capacity
Data Source
AI summary
Provided is a positive electrode active substance that increases the discharge capacity of a battery. This positive electrode for a non-aqueous electrolyte secondary battery comprises a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector. The positive electrode mixture layer contains: a positive electrode active substance that includes a lithium transition metal complex oxide with a layered halite structure; and a phosphate. The lithium transition metal complex oxide contains at least nickel and aluminum, and calcium and/or strontium; the content ratio of nickel in the lithium transition metal complex oxide is at least 75 mol % relative to the total amount of metal elements other than lithium; and the phosphate content of the positive electrode mixture layer, if the positive electrode active substance content is 100 parts by mass, is 0.1-5 parts by mass.