Lithium Nickel Composite Oxide Cell Swelling Control
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Solution Overview
Problem
Non-aqueous electrolyte secondary cells using lithium nickel composite oxide as the positive electrode active material face issues with cell swelling due to the decomposition of lithium carbonate, leading to inadequate cycle characteristics and increased thickness.
Innovation Solution
A non-aqueous electrolyte secondary cell design with a positive electrode active material comprising lithium nickel composite oxide, a porous layer with inorganic oxide and lithium carbonate on its surface, and a non-aqueous electrolyte, where the lithium carbonate content is limited to 0.20 mass % or less, and the porous layer thickness is between 1.0 to 5.0 μm, to minimize carbon dioxide generation and enhance electrolyte retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium carbonate is present on the surface of lithium nickel composite oxide, then high-temperature preservation characteristic is improved, but cell swelling occurs due to carbon dioxide generation
Solution Approach 1:
The patent converts the harmful effect of lithium carbonate decomposition (carbon dioxide generation causing cell swelling) into a beneficial effect by controlling the decomposition to form a protective film on the negative electrode. The carbon dioxide generated from lithium carbonate decomposition reacts with the negative electrode to form a stable protective film, which improves cycle characteristic while preventing further swelling.
Solution Approach 2:
The patent changes the parameter of lithium carbonate content from an uncontrolled amount to a specifically controlled amount (0.20 mass % or less). By precisely controlling this parameter, the patent achieves optimal balance between high-temperature preservation characteristic and prevention of cell swelling, resolving the technical contradiction.
2Reliability
If lithium carbonate content is increased to improve high-temperature preservation, then cycle characteristic improves, but cell swelling increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the lithium carbonate content to 0.20 mass % or less. This parameter control enables the patent to achieve sufficient cycle characteristic (improved by negative electrode film formation) while preventing excessive cell swelling, thus resolving the contradiction between cycle characteristic and cell thickness.
Solution Approach 2:
The patent converts the potentially harmful carbon dioxide generation into a beneficial film-forming process on the negative electrode. By controlling the lithium carbonate decomposition, the carbon dioxide serves to form a protective film that improves cycle characteristic without causing excessive swelling.
3Quantity of substance
If lithium carbonate is used to protect positive electrode surface, then initial capacity is improved, but carbon dioxide generation causes cell swelling
Solution Approach 1:
The patent controls the lithium carbonate content parameter to 0.20 mass % or less, which is sufficient to provide initial capacity protection and enable protective film formation, but limited enough to prevent excessive carbon dioxide generation and cell swelling.
Solution Approach 2:
The patent converts the carbon dioxide generation from a harmful effect (cell swelling) into a beneficial effect (protective film formation on negative electrode). The controlled decomposition of lithium carbonate provides both initial capacity protection and cycle characteristic improvement.
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 reduces cell swelling, improves cycle characteristics by facilitating stable film formation on the negative electrode, and maintains high capacity while preventing abrupt thickness increases.
Implementation Method 1
when the cell using the lithium nickel composite oxide is preserved at high temperature, the lithium nickel composite oxide is decomposed to generate carbon dioxide gas
Implementation Method 2
the porous layer provided on the surface of the positive electrode keeps therein the non-aqueous electrolyte in a preferable manner
Implementation Method 3
the carbon dioxide gas from the porous layer easily moves to the negative electrode
Implementation Method 4
The carbon dioxide gas now at the negative electrode reacts with it to form a stable covering film on the surface of the negative electrode
Data Source
AI summary
A non-aqueous electrolyte secondary cell that has high capacity and excellent cycle characteristic while preventing cell swelling is provided. The positive electrode of the cell has, as the positive electrode active material, lithium nickel composite oxide represented by LixNi1-yMyOz where 0.9<x≦1.1, 0≦y≦0.7, 1.9≦z≦2.1, and M contains at least one selected from Al, Co, and Mn. The amount of lithium carbonate on the surface of the lithium nickel composite oxide is 0.20 mass % or less relative to the lithium nickel composite oxide. On the surface of the positive electrode, a porous layer having inorganic oxide and lithium carbonate is provided.