High-Ni Cathode Material With Size-Tuned Boron Surface Coating

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Solution Overview

Problem

Existing positive electrode active materials in non-aqueous electrolyte secondary batteries face challenges in maintaining high energy density while inhibiting capacity decrease during high-temperature charging and discharging, and increasing resistance due to secondary particle cracking and electrolyte decomposition.

Innovation Solution

A positive electrode active material with a lithium-transition metal composite oxide containing 80 mol% Ni and varying boron mole fractions on first and second particles, where the mole fraction of boron is higher on larger particles to inhibit secondary particle cracking and lower on smaller particles to reduce resistance, thereby enhancing both high-temperature stability and rate characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If boric acid compound is adhered onto particle surface to inhibit electrolyte decomposition, then high-temperature capacity stability is improved, but battery resistance increases and rate characteristics deteriorate

Engineering Contradiction:

Improvehigh-temperature capacity stabilityVSAvoidbattery resistance

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies different boron contents to different particle sizes: larger particles (first particles) have higher boron content to prevent cracking and maintain structural stability, while smaller particles (second particles) have lower boron content to reduce resistance and improve rate characteristics. This local differentiation resolves the contradiction between high-temperature stability and resistance by optimizing boron distribution according to particle size requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the boron content parameter across different particle size populations. By controlling the boron mole fraction to be higher in first particles and lower in second particles, the patent optimizes the balance between structural stability (requiring higher boron) and electrical conductivity (requiring lower boron), thereby resolving the contradiction between capacity stability and resistance.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If high Ni content composite oxide is used to achieve high energy density, then energy density is improved, but secondary particle cracking occurs and capacity decreases at high temperature

Engineering Contradiction:

Improveenergy densityVSAvoidhigh-temperature capacity retention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent creates a composite structure where a boron-containing compound coats the surface of the lithium-transition metal composite oxide particles. This composite material approach allows the high-Ni core to provide energy density while the boron-containing shell prevents electrolyte decomposition and particle cracking at high temperatures, thereby resolving the contradiction between energy density and high-temperature reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies boron-containing compounds specifically on the particle surfaces rather than uniformly throughout the bulk material. This localized application allows the high-Ni content bulk to maintain high energy density while the surface layer provides protection against high-temperature degradation, resolving the contradiction between energy density and thermal stability.

Inventive Principle:

Principle #3Local quality

3Reliability

If uniform boron distribution is applied to all particles, then high-temperature stability is improved, but rate characteristics deteriorate due to increased resistance

Engineering Contradiction:

Improvehigh-temperature capacity stabilityVSAvoidrate characteristics

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements non-uniform boron distribution based on particle size: larger particles receive higher boron content for structural stability, while smaller particles receive lower boron content for reduced resistance and improved rate characteristics. This local quality differentiation resolves the contradiction between high-temperature stability and rate characteristics by optimizing boron content according to each particle size's specific requirements.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP4024530B1Positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery

Publication Date: 2026.03.11 PANASONIC HOLDINGS CORP

Figure 1

AI summary

This positive electrode active material for nonaqueous electrolyte secondary batteries is a positive electrode active material that comprises a lithium transition metal composite oxide containing at least 80 mol% Ni with reference to the total number of moles of metal elements excluding Li, and that has B present on the particle surface of at least this composite oxide. Assuming that a particle having a particle diameter larger than the 70% volume-based particle diameter (D70) is denoted as a first particle and a particle having a particle diameter smaller than the 30% volume-based particle diameter (D30) is denoted as a second particle, the mole fraction of B, with reference to the total number of moles of metal elements excluding Li, in the first particle is larger than the mole fraction of B, with reference to the total number of moles of metal elements excluding Li, in the second particle.