Oxide Cathode Particle Morphology for Solid-State Battery Contact
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Solution Overview
Problem
All-solid-state lithium ion batteries face challenges in achieving good contact between the solid electrolyte and positive electrode active material, leading to deteriorated battery performance, such as increased internal resistance and reduced capacity, due to insufficient electrical contact at their interface.
Innovation Solution
An oxide-based positive electrode active material with a compositional formula of Li a Ni x Co y Mn 1-x-y O 2, where 0.98 ≤ a ≤ 1.05; 0.8 ≤ x ≤ 1.0; and 0 ≤ y ≤ 0.20, is developed, with an average particle diameter D50 of 1.0 to 5.0 µm, a tap density of 1.6 to 2.5 g/cc, and circularity of 0.85 to 0.95, produced through a method involving a crystallization reaction in an aqueous solution with controlled pH, ammonium ion concentration, and temperature, followed by firing with a lithium compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the particle diameter of the positive electrode active material is decreased to increase contact points with the solid electrolyte, then the electrical contact state improves, but the tap density is lowered, resulting in decreased energy density per volume
Solution Approach 1:
The patent applies parameter changes by precisely controlling multiple parameters during the crystallization process including pH (10.5-11.5), temperature (50-65°C), ammonium ion concentration (5-25 g/L), and stirring power (1.8-7.3 kW/m³) to achieve particles with optimal size distribution (D50: 1.0-5.0 μm) and morphology (circularity: 0.85-0.95) that simultaneously improve contact and maintain high tap density (1.6-2.5 g/cc)
Solution Approach 2:
The patent utilizes controlled porosity and specific particle morphology achieved through the crystallization process, creating particles with high circularity (0.85-0.95) and appropriate size distribution that enhance interfacial contact with solid electrolyte while maintaining high packing density, effectively combining the benefits of increased surface area with high tap density
2Quantity of substance
If lithium cobaltate is used as the positive electrode active material, then the charge/discharge capacity is improved, but the cost increases and supply stability decreases due to cobalt scarcity and price volatility
Solution Approach 1:
The patent applies parameter changes by adjusting the compositional formula parameters (a, x, y in Li a Ni x Co y Mn 1-x-y O 2) within specific ranges to optimize the balance between capacity and cost, achieving high capacity materials with reduced cobalt content while maintaining performance through precise compositional control
Solution Approach 2:
The patent employs composite materials by creating a quaternary lithium nickel cobalt manganese oxide composite that combines the advantages of different metal oxides, achieving high charge/discharge capacity while reducing dependence on scarce cobalt through the synergistic effect of nickel, cobalt, and manganese components
3Temperature
If lithium manganate is used as the positive electrode active material, then the thermal stability is improved, but the charge/discharge capacity and cycle characteristics deteriorate
Solution Approach 1:
The patent employs composite materials by integrating manganese oxide components into a quaternary lithium nickel cobalt manganese oxide structure, where manganese provides thermal stability while nickel and cobalt contribute to high charge/discharge capacity, achieving a balanced performance profile that overcomes the limitations of binary compounds
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
This approach enhances the contact area and conductivity between the solid electrolyte and positive electrode active material, resulting in improved battery characteristics, including increased energy density and capacity retention, while maintaining thermal stability and cost-effectiveness.
Implementation Method 1
a step of performing a crystallization reaction using an aqueous solution containing basic aqueous solutions of a nickel salt, a cobalt salt, and a manganese salt, an aqueous ammonia and an alkali metal as a reaction solution while controlling a pH of the reaction solution to a range of from 10.5 to 11.5, and an ammonium ion concentration to a range of from 5 to 25 g/L and a temperature of the reaction solution to a range of from 50 to 65 °C
Implementation Method 2
firing with a lithium compound
Data Source
Figure 1
AI summary
Provided is an oxide-based positive electrode active material for all-solid-state lithium ion batteries, which can obtain improved battery characteristics upon use for an all-solid-state lithium ion battery. An oxide-based positive electrode active material for all-solid-state lithium ion batteries, the oxide-based positive electrode active material having a compositional formula represented by LiaNixCoyMn1-x-yO, with 0.98 ≤ a ≤ 1.05; 0.8 ≤ x ≤ 1.0; and 0 ≤ y ≤ 0.20, wherein the oxide-based positive electrode active material has an average particle diameter D50 of from 1.0 to 5.0 µm, a tap density of from 1.6 to 2.5 g/cc, and a circularity of from 0.85 to 0.95.