Gradient Cathode Composition for Low-Resistance Lithium-Ion Batteries

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Solution Overview

Problem

Lithium secondary batteries face challenges with stability, output characteristics, and low temperature performance due to the unstable crystal structure of existing cathode active materials, particularly LiCoO2, which deteriorates thermal characteristics and results in lower output and increased internal resistance.

Innovation Solution

A secondary battery design incorporating a cathode active material with a concentration gradient of metals from the central portion to the surface, combined with a conductive material mixture of carbon nanotubes and carbon black at specific ratios, to enhance stability, output, and low temperature performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiCoO2 is used as cathode active material, then stable charge and discharge characteristics and high battery voltage are achieved, but thermal characteristics deteriorate due to unstable crystal structure during charging

Engineering Contradiction:

Improvecharge and discharge characteristicsVSAvoidthermal characteristics

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a concentration gradient of metal elements within the cathode active material particles. The surface region contains a different composition than the central region, with the surface having enhanced stability characteristics while the interior maintains high capacity. This spatial variation in composition allows different regions to fulfill different functions: surface regions provide structural stability and thermal resistance, while interior regions provide high lithium content for capacity.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If lithium transition metal oxide with metal composition concentration gradient is used, then thermal stability is improved, but output characteristic decreases due to large internal resistance

Engineering Contradiction:

Improvethermal stabilityVSAvoidoutput characteristic

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The patent applies parameter changes by systematically varying the concentration of metal elements (such as Ni, Co, Mn) as a function of position within the particle. By controlling the gradient profile of metal composition from surface to center, the patent optimizes both thermal stability (through surface enrichment with stable elements) and electrical conductivity (through appropriate interior composition), thereby improving output characteristics while maintaining thermal stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by combining multiple metal elements (Ni, Co, Mn, etc.) in a controlled concentration gradient within a single cathode active material phase. This creates a compositionally graded composite structure where different metal combinations in different regions provide complementary properties: surface regions with higher stability elements for thermal resistance, and interior regions optimized for lithium insertion/extraction and electrical conductivity.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional cathode active material is used, then manufacturing is simple, but low temperature performance is poor due to high internal resistance

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlow temperature performance

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

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 exhibits improved stability, output characteristics, and low temperature performance by forming an effective conductive path between the cathode active material and conductive materials, maintaining high capacity and lifespan while reducing internal resistance.

Implementation Method 1

a conductive material mixture in which carbon nanotube is mixed with carbon black at an appropriate ratio... forming an effective conductive path between the cathode active material and conductive materials

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

The lithium secondary battery uses a principle in which electrical energy is generated by a change in chemical potential when lithium ions are inserted into and desorbed from a cathode and an anode

Methodology Applied

Scientific EffectChemical potential change:

Implementation Method 3

a cathode active material in which at least one of metals forming the cathode active material has a concentration gradient in an entire region from a central portion up to a surface portion

Methodology Applied

Scientific EffectConcentration gradient: Density Gradient

Data Source

PatentUS11870068B2Lithium ion secondary battery

Publication Date: 2024.01.09 SK ON CO LTD

AI summary

Provided is a secondary battery, specifically, a secondary battery having excellent stability and improved output characteristic and low temperature characteristic by including a cathode active material in which at least one of metals forming the cathode active material has a concentration gradient in at least a portion of a region between a central portion and a surface portion; and a conductive material mixture in which carbon nanotube is mixed with carbon black at an appropriate ratio, the carbon black being a spherical nanoparticle.