High Tap Density Lithium Cathode via Reducing Atmosphere Heating
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Solution Overview
Problem
Current methods for preparing lithium positive electrode active materials for lithium secondary batteries face challenges in achieving high tap density and stability, requiring multiple heating steps and excess lithium, which affects energy density and cycle performance.
Innovation Solution
A process involving a heating step under a reducing atmosphere to produce a lithium positive electrode active material with a high tap density and stability, utilizing a precursor that is partly or fully decomposed, resulting in a spinel phase with a net chemical composition of LixNiyMn2-yO4-δ, where 0≤x≤1.1, 0.4≤y≤0.5, and 0≤δ≤0.1, with a tap density of 1.8 g cm−3 or higher and maintaining capacity over 100 cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple heating steps are used to prepare lithium positive electrode active material, then the material achieves desired spinel phase and composition, but the process complexity and energy consumption increase
Solution Approach 1:
The patent combines multiple heating steps into a single heating step that achieves both precursor decomposition and spinel phase formation simultaneously. The heating step is conducted at a temperature sufficient to decompose the precursor and form the spinel phase, eliminating the need for separate decomposition and sintering steps.
Solution Approach 2:
The patent optimizes the heating temperature and atmosphere parameters to enable single-step synthesis. By controlling the heating temperature to be sufficient for both precursor decomposition and spinel phase formation, and by using an appropriate atmosphere, the process achieves reliable spinel phase formation in one step.
2Reliability
If excess lithium is added to ensure complete lithium incorporation, then the desired composition is achieved, but the energy density of the battery decreases
Solution Approach 1:
The patent uses a precursor that is pre-formulated with the correct stoichiometric ratio of lithium to other metals. The precursor is designed to decompose and release lithium at the appropriate time during the heating step, ensuring complete lithium incorporation without requiring excess lithium to be added to the mixture.
Solution Approach 2:
The patent employs a precursor as an intermediary substance that facilitates controlled lithium release. The precursor contains lithium in a form that is released during decomposition, acting as a mediator between the starting materials and the final spinel phase, ensuring proper lithium incorporation without excess.
3Reliability
If high heating temperatures are used to form spinel phase, then the desired crystal structure is achieved, but oxygen loss and material degradation occur
Solution Approach 1:
The patent optimizes the heating temperature parameter to be the minimum temperature sufficient for spinel phase formation, avoiding excessively high temperatures that would cause oxygen loss. The atmosphere during heating is also controlled to prevent oxidation and oxygen loss while enabling spinel phase formation.
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 process achieves a lithium positive electrode active material with a tap density of 1.8 g cm−3 or higher and maintains capacity with minimal decrease over 100 cycles, enhancing energy density and stability, while reducing the need for excess lithium and process steps.
Implementation Method 1
utilizing a precursor that is partly or fully decomposed
Implementation Method 2
resulting in a spinel phase with a net chemical composition of LixNiyMn2-yO4-δ
Implementation Method 3
the annealing step is generally at a temperature greater than 800° C. in order to cause a loss of oxygen while creating the desired spinel morphology
Data Source
AI summary
A lithium positive electrode active material intermediate including less than 80 wt % spinel phase and a net chemical composition of LixNiyMn2-yO4-δ wherein 0.9≤x≤1.1; 0.4≤y≤0.5; and 0.1≤δ. Further, a process for the preparation of a lithium positive electrode active material with high tap density for a high voltage secondary battery where the cathode is fully or partially operated above 4.4 V vs. Li/Li+, comprising the steps of a)heating a precursor in a reducing atmosphere at a temperature of from 300° C. to 1200° C. to obtain a lithium positive electrode active material intermediate; b)heating the product of step a. in a non-reducing atmosphere at a temperature of from 300° C. to 1200° C.; wherein the mass of the product of step b. increases by at least 0.25% compared to the mass of the product of step a.