Dual Coating Lithium Battery Cathode for Low Temperature Output

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Solution Overview

Problem

Lithium secondary batteries using conventional positive electrode materials exhibit increased resistance at low temperatures, insufficient low temperature output characteristics, significant deterioration in capacity when repeatedly charged and discharged at high temperatures, and poor durability at high voltages.

Innovation Solution

A positive electrode material for lithium secondary batteries is developed, comprising a positive electrode active substance particle with a Li-free first coating of titanium oxide and a Li-containing second coating of composite oxide, where the ratio of Li to Ti is between 0.1 and 3, and the total Ti content is between 0.01 and 10 mass%, enhancing low temperature output, high temperature cycle, and high voltage durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional positive electrode materials are used, then the battery can operate at high voltage, but the resistance increases at low temperatures and low temperature output characteristics are insufficient

Engineering Contradiction:

Improvelow temperature output characteristicsVSAvoidresistance at low temperatures

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The coating is divided into two distinct layers: a first coating layer containing titanium oxide (TiO2 or TinO2n-1) and a second coating layer containing lithium-titanium composite oxide. This segmentation allows each layer to perform specific functions - the first layer provides basic surface modification while the second layer with Li/Ti ratio of 0.1-3 optimizes low temperature performance, resolving the contradiction between power output and resistance at low temperatures

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite oxide materials in the second coating layer containing both lithium and titanium with a controlled atomic ratio. This composite material approach creates a synergistic effect where the lithium-titanium composite oxide provides superior low temperature conductivity and stability, addressing both the power output and resistance issues simultaneously

Inventive Principle:

Principle #40Composite materials

2Productivity

If conventional positive electrode materials are used, then the battery can achieve high capacity, but significant deterioration occurs when repeatedly charged and discharged at high temperatures

Engineering Contradiction:

ImprovecapacityVSAvoidhigh temperature cycle characteristics

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The dual coating structure is applied in advance to the positive electrode active substance particles before battery operation. The first coating of titanium oxide and the second coating of lithium-titanium composite oxide are pre-formed to provide protective and functional properties that prevent capacity deterioration during high temperature cycling, allowing the battery to maintain high capacity while improving cycle life

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the chemical composition parameters of the surface coating by controlling the Li/Ti atomic ratio in the second coating layer between 0.1 and 3. This parameter optimization creates a coating with enhanced thermal stability and electrochemical performance, enabling the battery to maintain capacity over extended high temperature cycling without significant deterioration

Inventive Principle:

Principle #35Parameter changes

3Power

If conventional positive electrode materials are used, then the battery can operate at high voltage, but durability against high voltage is insufficient

Engineering Contradiction:

Improvehigh voltage durabilityVSAvoiddurability against high voltage

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The dual coating structure acts as an intermediary layer between the positive electrode active substance and the electrolyte. The first coating of titanium oxide and the second coating of lithium-titanium composite oxide provide a stable interface that protects the electrode material from direct exposure to harsh electrolyte conditions at high voltage, thereby improving durability while maintaining high voltage operation capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention modifies the surface composition parameters by introducing titanium oxide and lithium-titanium composite oxide coatings with controlled Li/Ti ratios. This changes the electrochemical stability window and surface properties of the electrode, enabling it to withstand high voltage conditions more durably without sacrificing power output

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11626586B2Positive electrode material of lithium secondary battery, and lithium secondary battery using same

Publication Date: 2023.04.11 TOYOTA JIDOSHA KK

AI summary

Provided is a positive electrode material which can impart a lithium secondary battery with excellent low temperature output characteristics, excellent high temperature cycle characteristics and excellent durability against high voltage. A positive electrode material of a lithium secondary battery disclosed here includes a positive electrode active substance particle, a Li-free first coating at the surface of the positive electrode active substance particle, and a Li-containing second coating at the surface of the positive electrode active substance particle. The first coating contains a titanium oxide represented by TiO2 or TinO2n-1, wherein n is an integer of 3 or more. The second coating contains a composite oxide containing Li and Ti, wherein the ratio of the number of atoms of Li relative to the number of atoms of Ti is at least 0.1 and at most 3.