Positive Active Material for Lithium Battery with Dual-Compound Structure

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Solution Overview

Problem

Nickel-based lithium transition metal oxides in rechargeable lithium batteries suffer from low discharge capacity per unit volume, safety issues at high voltages, and inefficient charge/discharge due to excess lithium and cation mixing, which affects their performance and stability.

Innovation Solution

A positive active material comprising a first compound and a second compound with specific nickel content and particle sizes, optimized through a two-stage heat-treating process to minimize cation mixing and enhance phase stability, is used in the rechargeable lithium battery, along with a method of preparing this material by mixing transition metal hydroxides and a lithium salt under controlled temperature conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If nickel-based lithium transition metal oxide with high Ni content (33-60 at%) is used to increase discharge capacity per unit weight, then charge/discharge capacity per unit weight is improved, but charge/discharge efficiency deteriorates and cation mixing increases

Engineering Contradiction:

Improvedischarge capacity per unit weightVSAvoidcharge/discharge efficiency

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent optimizes the Li to transition metal mole ratio parameter, setting it within 1.00 to 1.05 (preferably 1.01 to 1.03), and controls Ni content within 33-60 at% (preferably 40-50 at%). These parameter optimizations balance the discharge capacity per unit weight with charge/discharge efficiency, resolving the contradiction between quantity of substance and reliability.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If nickel-based lithium transition metal oxide with high Ni content (33-60 at%) is used to increase discharge capacity per unit weight, then discharge capacity per unit weight is improved, but cation mixing value increases

Engineering Contradiction:

Improvedischarge capacity per unit weightVSAvoidcation mixing value

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent optimizes the Li to transition metal mole ratio parameter, setting it within 1.00 to 1.05, and controls Ni content within 33-60 at%. These parameter optimizations balance the discharge capacity per unit weight with cation mixing value, resolving the contradiction between quantity of substance and stability of composition.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If nickel-based lithium transition metal oxide is used to achieve high discharge capacity, then discharge capacity is improved, but safety deteriorates during operation at high voltage

Engineering Contradiction:

Improvedischarge capacityVSAvoidsafety at high voltage

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the Li to transition metal mole ratio parameter and controls Ni content within specific ranges (33-60 at%, preferably 40-50 at%). These parameter optimizations balance discharge capacity with safety at high voltage, resolving the contradiction between quantity of substance and object-affected harmful factors.

Inventive Principle:

Principle #35Parameter changes

4Stability of the object's composition

If excess lithium is included in the positive active material to compensate for lithium loss, then structural stability is improved, but charge/discharge efficiency deteriorates

Engineering Contradiction:

Improvestructural stabilityVSAvoidcharge/discharge efficiency

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent precisely optimizes the Li to transition metal mole ratio parameter within 1.00 to 1.05 (preferably 1.01 to 1.03), avoiding both excess and deficient lithium. This precise parameter control balances structural stability with charge/discharge efficiency, resolving the contradiction between stability of composition and reliability.

Inventive Principle:

Principle #35Parameter changes

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 solution improves charge/discharge capacity, efficiency, and cycle-life characteristics of the lithium battery by reducing cation mixing and maintaining phase stability, leading to enhanced performance and safety.

Implementation Method 1

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS11552293B2Positive active material for rechargeable lithium battery, method of preparing the same and rechargeable lithium battery including the same

Publication Date: 2023.01.10 SAMSUNG SDI CO LTD

AI summary

A positive active material for a rechargeable lithium battery includes a first compound represented by Chemical Formula 1, and a second compound having a smaller particle diameter than the first compound and represented by Chemical Formula 2, wherein the first compound and the second compound have a Ni content of about 50 at % to about 60 at % based on a total amount of metal elements excluding Li. A rechargeable lithium battery including the first compound and the second compound satisfies Relation 1:Vs<V1≤3.6. [Relation 1]In Relation 1, V1 is a voltage value at a point where a tangent line to a value corresponding to 50% of the first peak value intersects the line dQ/dV=0, and Vs is a charge start voltage, as determined from a differential capacity (dQ/dV)-voltage charge/discharge plot.