NASICON Sodium Vanadium Phosphates for Single-Phase High-Voltage Cathodes

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Solution Overview

Problem

Existing Na-ion batteries face limitations in terms of operating voltage, energy density, volume expansion, and electrochemical reaction mechanisms, particularly with materials like Na3V2(PO4)3, which have low working voltage and limited capacity due to biphasic reactions.

Innovation Solution

A new Na-based positive electrode material with a formula (I) is developed, featuring a V/Z ratio of 212 Å^3 to 246 Å^3, allowing for a single-phase reaction mechanism and increased operating voltage from 3.0 V to 4.3 V vs. Na+/Na, enhancing energy density by 15% to 464 Wh/kg.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional Na3V2(PO4)3 material is used, then structural stability is maintained, but operating voltage remains low at 3.4 V vs. Na+/Na

Engineering Contradiction:

Improveoperating voltageVSAvoidstructural stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent modifies the chemical composition parameters of the NASICON structure by substituting V with Mo and W, and adjusting the Na content to create NaxV2-y-zMoyWz(PO4)3. This compositional parameter change enables the material to achieve higher operating voltages (3.0-4.3 V vs. Na+/Na) while maintaining the structural stability of the NASICON framework through controlled solid solution formation.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If Na3V2(PO4)3 undergoes biphasic reaction mechanism, then capacity is limited to 117.6 mAh/g, but extraction of third Na+ is prevented due to large migration energy

Engineering Contradiction:

ImprovecapacityVSAvoidreaction mechanism

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

By changing the compositional parameters (substituting V with Mo/W and adjusting Na content), the patent transforms the reaction mechanism from biphasic to solid-solution type. This parameter modification allows for smoother Na+ extraction and insertion, enabling higher capacity utilization while avoiding the kinetic barriers associated with phase transitions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite solid solution material NaxV2-y-zMoyWz(PO4)3 that combines multiple elements within a single crystalline phase. This composite approach at the atomic level enables the material to exhibit enhanced electrochemical performance with solid-solution reaction mechanism, avoiding the limitations of biphasic reactions while maintaining structural integrity.

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If conventional Na3V2(PO4)3 is used, then material cost is reduced, but energy density is limited due to low operating voltage

Engineering Contradiction:

Improveenergy densityVSAvoidmaterial cost

Core Design Contradiction:

Use of energy by moving objectVSEase of manufacture

Solution Approach 1:

The patent optimizes the compositional parameters of the NASICON material by controlling the ratios of V, Mo, and W, as well as the Na content. This parameter optimization achieves higher energy density (464 Wh/kg) through increased operating voltage while maintaining cost-effectiveness by using relatively abundant elements and straightforward solid-state synthesis methods.

Inventive Principle:

Principle #35Parameter changes

4Quantity of substance

If Na3V2(PO4)3 undergoes electrochemical reaction, then capacity is achieved, but volume expansion of 8.2% occurs

Engineering Contradiction:

ImprovecapacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent designs a composite solid solution NaxV2-y-zMoyWz(PO4)3 where Mo and W atoms are integrated into the NASICON framework alongside V atoms. This composite structure provides better volumetric stability during Na+ insertion/extraction cycles, reducing volume expansion while maintaining high capacity through the solid-solution reaction mechanism.

Inventive Principle:

Principle #40Composite materials

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 new material exhibits improved operating voltage, higher energy density, and reduced volume expansion, offering better performance than conventional Na3V2(PO4)3 and Li3V2(PO4)3 materials through a solid-solution mechanism.

Implementation Method 1

Methodology Applied

Scientific EffectSolid-solution mechanism:

Implementation Method 2

Sodium layered transition metal oxides, prussian blue analogues, and polyanionic compounds are considered as possible positive electrode materials for sodium-ion batteries.

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions

Data Source

PatentUS20250349848A1New nasicon-type high voltage sodium vanadium phosphates materials for na-ion batteries

Publication Date: 2025.11.13 TIAMAT

AI summary

The present invention concerns a material of formula (I):wherein:A is Na or Li or a mixture of Na and Li,1<x<3,0≤y≤1,0≤z≤1M is an electro-active transition element or a mixture of at least two electro-active transition elements,M′ is a non electro-active element or a mixture of at least two non electro-active elements, and the material of formula (I) presents a V/Z ratio varying from 212 Å3 to 246 Å3.