Cathode Active Material Coating for Lower Resistance Solid-State Batteries
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Solution Overview
Problem
Lithium transition metal composite oxides with high nickel content exhibit high battery resistance, and existing surface coatings like lithium niobate do not adequately address this issue, necessitating further improvements in output characteristics.
Innovation Solution
A method involving a lithium transition metal composite powder with specific nickel and cobalt ratios, subjected to controlled heat treatments and coated with a niobium compound, creating a cobalt concentration gradient and niobium surface coating to inhibit resistance layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is used in lithium transition metal composite oxide, then battery capacity is improved, but battery resistance increases
Solution Approach 1:
The patent applies local quality by creating a cobalt concentration gradient within the cathode active material particles. The cobalt content is higher in the inner region (0.1-0.3 mol ratio) and lower in the outer region (0.05-0.2 mol ratio), allowing the inner core to provide high capacity while the outer layer reduces resistance, thus resolving the contradiction between capacity and resistance
Solution Approach 2:
The patent uses composite materials by combining lithium nickel oxide with lithium cobalt oxide in a specific gradient structure. This composite approach allows the material to simultaneously exhibit high capacity characteristics from nickel-rich regions and low resistance characteristics from cobalt-rich regions, resolving the technical contradiction
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 reduces battery resistance and enhances lithium-ion conductivity, leading to improved output characteristics in all-solid-state secondary batteries.
Implementation Method 1
subjecting the cobalt-adhered composite oxide to a first heat treatment performed at a temperature higher than 600° C. and lower than 800° C. to obtain a first heat-treated product
Implementation Method 2
the lithium transition metal composite oxide having a secondary particle surface containing a niobium compound on at least a part of the particle surface
Implementation Method 3
the lithium transition metal composite oxide having a higher cobalt concentration in a second region than in a first region, where the first region is a region that is approximately 60 nm deep from the secondary particle surface, and the second region is a region that is approximately 10 nm deep from the secondary particle surface
Data Source
AI summary
Provided is a method for producing a cathode active material for a secondary battery which enables configuring a battery with improved battery resistance. The method includes providing a lithium transition metal composite powder in which a ratio of the number of moles of nickel atoms to the total number of moles of metal atoms other than lithium is 0.5 or more and less than 1 and a ratio of the number of moles of cobalt atoms to the total number of moles of metal atoms other than lithium is 0 or more and less than 0.5, the lithium transition metal composite powder having a layered structure; contacting the lithium transition metal composite powder with a cobalt raw material to obtain a cobalt-adhered composite oxide; subjecting the cobalt-adhered composite oxide to a first heat treatment performed at a temperature higher than 600° C. and lower than 800° C. to obtain a first heat-treated product; contacting the first heat-treated product with a niobium raw material to obtain a niobium-adhered composite oxide; and subjecting the niobium-adhered composite oxide to a second heat treatment performed at a temperature higher than 300° C. and lower than 500° C. to obtain a second heat-treated product.