Nb-Coated Positive Electrode Material With Uniform Particle Coverage
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Solution Overview
Problem
Secondary batteries, such as lithium ion batteries, face challenges in increasing their capacity due to limitations in positive electrode active materials, particularly in the distribution and dispersion of Nb elements on the surface of lithium-containing composite oxides.
Innovation Solution
A positive electrode for secondary batteries is developed with a lithium-containing composite oxide having a coating film of Nb elements, where the Gini coefficient of the Nb element, calculated from time-of-flight secondary ion mass spectrometry, is less than or equal to 0.5, ensuring uniform dispersion and improved battery capacity. The method involves baking a mixture of lithium and metal compounds to form the composite oxide and then mixing it with a Nb compound solution and baking again to control the Nb distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a coating film containing Nb element is formed on the surface of primary particles, then the capacity of the secondary battery is improved, but the manufacturing complexity increases due to the need to control Gini coefficient
Solution Approach 1:
The patent applies parameter changes by controlling the Gini coefficient of Nb element distribution as a quantitative parameter. By specifying that the Gini coefficient must be 0.7 or less, the patent transforms the qualitative requirement of 'uniform distribution' into a measurable and controllable parameter, thereby improving battery capacity while maintaining manageable manufacturing complexity through parameter-based control.
Solution Approach 2:
The patent replaces complex mechanical mixing processes with a chemical coating approach. Instead of mechanically mixing Nb compounds with the lithium-containing composite oxide, the patent uses a coating process where Nb compound is deposited on the surface of primary particles. This substitution simplifies the manufacturing process while achieving the desired uniform distribution of Nb element, as evidenced by the controlled Gini coefficient.
2Reliability
If Nb element is uniformly dispersed on the surface of primary particles, then the battery performance is improved, but the measurement and detection difficulty increases due to requiring TOF-SIMS analysis
Solution Approach 1:
The patent uses the Gini coefficient as an intermediary parameter to bridge the gap between Nb element distribution and battery performance. Instead of directly measuring and controlling the complex spatial distribution of Nb atoms, the patent employs the Gini coefficient as an intermediary metric that quantifies distribution uniformity. This intermediary parameter can be determined through TOF-SIMS analysis, allowing indirect but effective control of battery performance through a manageable measurement approach.
3Stability of the object's composition
If a coating film containing Nb element is formed through mixing with Nb compound solution, then the Nb distribution uniformity is improved, but the manufacturing time increases due to additional baking step
Solution Approach 1:
The patent applies preliminary action by forming the Nb-containing coating film on the surface of primary particles before the final electrode fabrication process. The coating process is performed as a preliminary step, where Nb compound solution is applied and baked to form a stable coating layer. This preliminary action ensures uniform Nb distribution is established early in the manufacturing process, and the coating structure is maintained through subsequent processing steps, thereby achieving composition uniformity without requiring extended manufacturing time.
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 capacity of secondary batteries by ensuring uniform Nb distribution on the surface of the lithium-containing composite oxide, leading to improved battery performance.
Implementation Method 1
mixing it with a Nb compound solution
Implementation Method 2
baking the obtained mixture
Implementation Method 3
time-of-flight secondary ion mass spectrometry (TOF-SIMS) of a cross section of the secondary particle
Implementation Method 4
time-of-flight secondary ion mass spectrometry
Data Source
AI summary
A positive electrode for secondary batteries according to the present invention comprises a positive electrode collector and a positive electrode mixture layer that is arranged on the positive electrode collector, and is characterized in that: the positive electrode mixture layer comprises a positive electrode active material that contains a lithium-containing composite oxide that is composed of secondary particles, each of which is formed of aggregated primary particles; a coating film that contains elemental Nb is formed on the surface of each primary particle of the lithium-containing composite oxide; and the Gini coefficient of elemental Nb as calculated from an element mapping image that is obtained by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of a cross-section of the secondary particles is 0.5 or less.