Layered Positive Electrode Composition for Contact Resistance Reduction

Solution Overview

Problem

Lithium-nickel-manganese composite oxides used as positive electrode active materials in secondary batteries exhibit low electron conductivity, reduced current collecting properties, and high contact resistance with aluminum foil, leading to increased resistance and polarization, which deteriorates charge and discharge characteristics over repetitive cycles.

Innovation Solution

A positive electrode structure comprising a current collector with a first layer of lithium transition metal composite oxide having a high cobalt content, a second layer of cobalt-free lithium transition metal composite oxide, and third particles at the interface, optimizing particle diameters and layer thicknesses to enhance electron conductivity and adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium-nickel-manganese composite oxide is used as positive electrode active material, then large charge and discharge capacity is achieved, but electron conductivity is low

Engineering Contradiction:

Improvecharge and discharge capacityVSAvoidelectron conductivity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses a composite structure consisting of a first lithium transition metal composite oxide layer (containing Co, Ni, Mn) and a second lithium transition metal composite oxide layer (containing Ni, Mn but less Co), creating a composite material system that combines the high capacity of Li-Ni-Mn oxide with the improved conductivity of Co-containing oxide

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by creating a layered structure where the first layer (with higher Co content) is positioned at the interface with the current collector to improve conductivity and contact properties, while the second layer (with lower Co content) provides high capacity in the bulk

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If cobalt-free lithium transition metal composite oxide is used, then production cost is reduced, but contact resistance with aluminum foil is high

Engineering Contradiction:

Improveproduction costVSAvoidcontact resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by creating a layered structure where the first layer (with higher Co content) is positioned at the interface with the current collector to improve conductivity and contact properties, while the second layer (with lower Co content) provides high capacity in the bulk

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses a composite structure consisting of a first lithium transition metal composite oxide layer (containing Co, Ni, Mn) and a second lithium transition metal composite oxide layer (containing Ni, Mn but less Co), creating a composite material system that combines the high capacity of Li-Ni-Mn oxide with the improved conductivity and adhesion of Co-containing oxide

Inventive Principle:

Principle #40Composite materials

3Productivity

If repetitive charge and discharge cycles are performed, then battery capacity is utilized, but expansion and contraction generate gaps with aluminum foil causing resistance increase

Engineering Contradiction:

Improvebattery capacity utilizationVSAvoidcontact resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by creating a first layer with higher Co content that has better mechanical properties and adhesion to the aluminum current collector, which acts as a cushioning layer to maintain contact during the expansion and contraction cycles of the active material

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent uses a composite structure consisting of a first lithium transition metal composite oxide layer (containing Co, Ni, Mn) and a second lithium transition metal composite oxide layer (containing Ni, Mn but less Co), creating a composite material system that combines the high capacity of Li-Ni-Mn oxide with the improved conductivity and mechanical stability of Co-containing oxide

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20250132325A1Positive electrode for secondary batteries, and secondary battery

Publication Date: 2025.04.24 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A positive electrode with a positive electrode mixture layer provided on a surface of a positive electrode current collector, which includes a first layer contacting the positive electrode current collector and a second layer contacting the first layer. The first layer includes first active material particles with a particle diameter L. The second layer includes active material particles with a particle diameter R. Third positive electrode active material particles with a particle diameter r are included at least at an interface between the first and the second layers, wherein R>L>r. The first active material particles include a lithium transition metal composite oxide with a ratio of Co in metal element atoms other than Li of 2 atom % or more. The second and third active material particles including a different lithium transition metal composite oxide than the first active material particles.