Positive Electrode Plate Composition for Lithium Loss Compensation
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving higher energy density and cycling stability, particularly at high temperatures, due to irreversible capacity loss and solid electrolyte interphase (SEI) formation during the first charge and discharge process.
Innovation Solution
A positive electrode plate is designed with a combination of a first positive electrode active material represented by chemical formula Li1+xNaaCo1+yAlzMgpTiuMvO2+w and a second positive electrode active material represented by chemical formula Li2+rNasN1+qO2+t, which work synergistically to enhance lithium ion migration, structural stability, and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal powder or stabilized lithium metal powder is added to negative electrode slurry for lithium supplementation, then active lithium loss is compensated, but production safety risks increase due to high reactivity with moisture
Solution Approach 1:
The patent introduces a lithium compound (such as lithium carbonate, lithium hydroxide, or lithium oxide) as an intermediary substance to provide lithium supplementation. This intermediary reacts with the electrolyte or SEI layer to release lithium ions, achieving the same effect as direct lithium metal addition but without the safety hazards of handling reactive lithium metal powder.
2Reliability
If a graphite negative electrode is used, then production safety is improved, but active lithium consumption increases due to SEI formation
Solution Approach 1:
The patent applies preliminary lithium supplementation to the negative electrode before battery assembly. By pre-loading the negative electrode with additional lithium compounds, the electrode is prepared in advance to compensate for the lithium that will be consumed during SEI formation, ensuring sufficient active lithium remains for subsequent cycling.
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 synergistic effect between the two active materials improves high-temperature cycling performance and volumetric energy density of lithium-ion secondary batteries by effectively compensating for active lithium loss and maintaining structural stability.
Implementation Method 1
Li sites of the first positive electrode active material of a layered structure are doped with sodium (Na), expanding a lithium ion migration channel and increasing a lithium ion migration capacity
Implementation Method 2
Co sites are furthered doped with Al, Mg, or Y, and the first positive electrode active material contains Ti, Zr, or La, improving structural stability of the material
Implementation Method 3
the second positive electrode active material is doped with Na, expanding a lithium ion migration channel, and better high-temperature cycling performance and volumetric energy density are obtained
Data Source
AI summary
A positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, where the positive electrode active material layer includes two respective positive electrode active materials represented by chemical formula (1) and chemical formula (2): Li1+xNaaCo1+yAlzMgpTiuMvO2+w (1), where in chemical formula (1), M includes at least one of Zr, La, or Y, −0.1<x<0.1, 0<a<0.005, −0.05<y<0.05, 0.01<z<0.05, 0.001<p<0.01, 0<u<0.005, 0<v<0.005, and −0.05<w<0.05; and Li2+rNasN1+qO2+t (2), where in chemical formula (2), −0.2<r<0.2, 0≤s≤0.05, −0.1<q<0.1, −0.05<t<0.05, and N includes at least one of Ni, Cu, Mn, Fe, or Co. Such a positive electrode plate can achieve a high specific discharge capacity of the electrochemical apparatus, thereby increasing high-temperature cycling performance and energy density of the electrochemical apparatus.