P2-Type Sodium Cathode Material for Higher Weight Energy Density

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional positive electrode active materials with a P2-type structure for sodium-ion secondary batteries have limitations in weight energy density.

Innovation Solution

The development of a positive electrode active material comprising Na-containing oxide particles with a P2-type structure, specifically designed with a chemical composition of NaaMnx−pNiy−qCoz−rMp+q+rO2, where 0.70<a≤1.00, 0<x<1.00, 0<y<0.50, 0<z<1.00, and x+y+z=1, and an average particle diameter and aspect ratio optimized to achieve enhanced weight energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional P2-type structure positive electrode active materials are used, then the material can store and release sodium ions, but the weight energy density is insufficient

Engineering Contradiction:

Improveweight energy densityVSAvoidsodium ion capacity

Core Design Contradiction:

Use of energy by moving objectVSQuantity of substance

Solution Approach 1:

The patent optimizes the chemical composition parameters of the P2-type structure by controlling the ratio of transition metal elements (Mn, Ni, Co) and sodium content (Na0.67). It also controls particle morphology parameters including average particle diameter (2.0-5.0 μm) and aspect ratio (1.05-3.0), which collectively improve weight energy density while maintaining sodium ion storage capacity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite positive electrode active material by combining multiple transition metal elements (Mn, Ni, Co) in specific ratios within the P2-type structure. This composite approach allows optimization of both energy density and capacity by leveraging the complementary properties of different elements

Inventive Principle:

Principle #40Composite materials

2Speed

If the particle size is reduced to increase surface area for ion exchange, then the reaction rate improves, but the weight energy density decreases

Engineering Contradiction:

Improveion exchange rateVSAvoidweight energy density

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent identifies and optimizes critical particle parameters including average particle diameter (2.0-5.0 μm) and aspect ratio (1.05-3.0). This parameter optimization achieves a balance where particles are small enough for efficient ion exchange but large enough to maintain high weight energy density, resolving the contradiction between reaction rate and energy density

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240363848A1Positive electrode active material and sodium-ion secondary battery

Publication Date: 2024.10.31 TOYOTA JIDOSHA KK

AI summary

Disclosed is a positive electrode active material having a P2-type structure and having a large energy density. The positive electrode active material of the present disclosure comprises a Na-containing oxide. The Na-containing oxide particles have a P2-type structure. The Na-containing oxide particles at least comprise at least one element among Mn, Ni, and Co; Na; and O as constituent elements. The Na-containing oxide particles have an average particle diameter of 2.0 μm or more. The Na-containing oxide particles have an average aspect ratio of 1.0 or greater and 3.0 or less.