Positive Electrode Plate Resistivity Control for Lithium-Ion Battery Safety

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Solution Overview

Problem

Lithium-ion secondary batteries using ternary materials face safety issues due to insufficient thermal stability, leading to high-temperature decomposition, increased internal pressure, and potential fires or explosions, along with strong oxidation reactions that enhance safety hazards.

Innovation Solution

A positive electrode plate comprising a first active material (Li1+xNi aCo bM 1-a-bO 2-yAy) and a second active material (Li1+zMn cN 2-cO 4-dBd) with specific compositional ranges, combined with a conductive agent and binder, to achieve a resistivity of 3500 Ω·m or less, enhancing synergistic effects for improved safety and performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If ternary material is used as positive active material, then specific capacity and energy density are improved, but thermal stability deteriorates leading to safety issues

Engineering Contradiction:

Improvespecific capacityVSAvoidthermal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a composite positive active material consisting of Li1+xNiaCo bM1-a-bO2-yAy (0.05≤a+b≤0.95, 0<y≤0.5) combined with LiMn2O4. This composite structure leverages the high capacity of ternary materials while the spinel LiMn2O4 provides thermal stability and structural support, preventing catastrophic failure at high temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including the stoichiometric ratios (a, b, x, y), particle size distribution (D50: 3-8 μm), and density (3.8-4.2 g/cm³) to achieve a balance between capacity and thermal stability. By precisely controlling these parameters, the material maintains high specific capacity while resisting thermal decomposition.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If ternary material is fully charged, then energy density is improved, but oxidation reactions increase causing safety hazards

Engineering Contradiction:

Improveenergy densityVSAvoidoxidation reactions

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent introduces LiMn2O4 spinel structure as an intermediary material that mediates between the ternary material and the electrolyte. This intermediary layer reduces direct contact and harmful oxidation reactions between the fully charged ternary material and the electrolyte, while still allowing ion transport to maintain high energy density.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the strong oxidation property of fully charged ternary material from a harmful factor into a beneficial one by controlling the oxidation state through precise composition design. The controlled oxidation enhances the material's ability to accept lithium ions during charging, improving energy density while the spinel structure prevents uncontrolled side reactions.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If positive electrode plate resistivity is reduced to enhance synergistic effect, then safety performance is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvesafety performanceVSAvoidresistivity control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent controls the resistivity of the positive electrode plate within a specific range (3000-5000 μΩ·cm) by optimizing parameters such as active material composition, particle size distribution, binder content, and conductive additive content. This parameter optimization ensures low enough resistivity for safety while maintaining manufacturability through standard production processes.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3588625B1Positive electrode plate and lithium-ion secondary battery

Publication Date: 2020.12.23 CONTEMPORARY AMPEREX TECHNOLOGY CO LTD

AI summary

The present application discloses a positive electrode plate and a lithium-ion secondary battery, wherein the positive electrode plate comprises a positive electrode current collector and a positive active material layer disposed on at least one surface of the positive electrode current collector, and wherein the positive active material layer comprises a first positive active material and a second positive active material, and wherein the positive electrode plate has a resistivity of 3,500 Ω•m or less. The positive electrode plate provided by the present application enables the lithium-ion secondary battery to have high specific capacity and energy density and excellent safety performance, while at the same time to have excellent cycle performance and rate performance.