High-Nickel Cathode Material Processing for Better Cycle Stability
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Solution Overview
Problem
Existing methods for improving the cycle characteristics of non-aqueous electrolyte secondary batteries, such as water-washing and sulfate treatment, either lead to residual alkaline components causing issues or worsen the battery's cycle characteristics.
Innovation Solution
A method involving the use of a sodium ion-containing solution to wash lithium transition metal composite oxide particles, followed by mixing with a boron compound and heat-treating the mixture at specific temperatures to produce a positive electrode active material with improved cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If water-washing is performed to reduce residual alkaline components, then the harmful effects of residual alkaline components are reduced, but the cycle characteristics of the battery worsen
Solution Approach 1:
A sodium-containing compound is introduced as an intermediary substance during the water-washing process. The sodium compound preferentially reacts with or adsorbs the residual alkaline components (such as lithium hydroxide), forming a stable complex that can be easily removed. This mediator enables effective removal of harmful alkaline components while protecting the lithium nickel-based composite oxide particles from damage that would otherwise occur during aggressive washing, thereby maintaining good cycle characteristics.
2Quantity of substance
If the ratio of nickel to total metals other than lithium is increased to achieve higher electrical charge-discharge capacity, then the electrical charge-discharge capacity per unit weight is improved, but the synthesis difficulty increases and residual alkaline components remain
Solution Approach 1:
The synthesis parameters are optimized by controlling the nickel ratio to be greater than 0.80 (while maintaining stability through appropriate cobalt content), adjusting the sintering temperature and atmosphere to achieve complete reaction of high-nickel compositions, and controlling particle size distribution. These parameter changes enable the production of high-capacity lithium nickel-based composite oxides with reduced residual alkaline components, making high-nickel materials manufacturable while maintaining high electrical charge-discharge capacity.
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 method effectively reduces residual alkaline components, enhances the uniform dispersion of boron, and improves the electrical charge and discharge characteristics and cycle stability of the batteries.
Implementation Method 1
contacting first particles that contain a lithium transition metal composite oxide with a solution containing sodium ions to obtain second particles containing the lithium transition metal composite oxide and sodium element
Implementation Method 2
a compound containing boron is attached on at least a part of the surfaces of the primary particles
Implementation Method 3
heat-treating the mixture at a temperature in a range of from 100° C. to 450° C.
Implementation Method 4
mixing the second particles and a boron compound to obtain a mixture; and heat-treating the mixture
Data Source
AI summary
A method of producing a positive electrode active material, the method includes: contacting first particles that contain a lithium transition metal composite oxide with a solution containing sodium ions to obtain second particles containing the lithium transition metal composite oxide and sodium element, wherein the lithium transition metal composite oxide has a layered structure and a composition ratio of a number of moles of nickel to a total number of moles of metals other than lithium in a range of from 0.7 to less than 1; mixing the second particles and a boron compound to obtain a mixture; and heat-treating the mixture at a temperature in a range of from 100° C. to 450° C.