Lithium Manganese Cathode Plate Resistivity for Safer Li-Ion Cells
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in structural stability, thermal runaway, and performance due to material structural damage and electrolyte oxidation, leading to reduced safety and efficiency.
Innovation Solution
A positive electrode plate using a lithium manganese-based active material with specific volume resistivity and mass percentage properties, which enhances structural stability, reduces thermal runaway, and improves internal impedance, thereby increasing safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive active materials are used, then the battery can achieve basic electrochemical performance, but the material suffers from structural damage and thermal runaway, reducing safety and stability
Solution Approach 1:
The patent changes the chemical composition parameters of the positive active material by incorporating lithium manganese-based compounds with specific stoichiometric ratios (Li1+xMnaNbOc where x=0.01-0.2, a+b=2-4, c=7.5-8.5). This compositional parameter optimization enhances both structural stability and safety performance simultaneously, resolving the contradiction between reliability and compositional stability.
Solution Approach 2:
The patent creates a composite positive active material system by combining lithium manganese-based compounds with other cathode materials (such as lithium nickel cobalt manganese oxide). This composite approach leverages the high voltage platform of lithium manganese compounds while mitigating their structural instability, achieving both improved safety and maintained structural integrity.
2Use of energy by moving object
If the electrolyte contacts the positive active material surface, then ionic conduction occurs, but oxidation reactions generate gas and heat, reducing safety
Solution Approach 1:
The patent applies preliminary protective measures by forming a stable surface modification layer on the positive active material before electrolyte contact. This pre-formed protective barrier prevents direct oxidation reactions between the electrolyte and material surface, eliminating gas and heat generation while maintaining ionic conduction pathways.
Solution Approach 2:
The patent introduces an intermediary protective coating or surface modification layer between the electrolyte and positive active material. This intermediary layer acts as a physical barrier that blocks harmful oxidation reactions while allowing lithium ion transport, thus preventing gas and heat generation without compromising ionic conduction.
3Productivity
If the volume resistivity and mass percentage are optimized to reduce internal impedance, then rate performance improves, but the electrode plate requires precise parameter control
Solution Approach 1:
The patent establishes specific parameter ranges for volume resistivity (ρsum) and mass percentage (α) that simultaneously achieve low internal impedance and high rate performance. By defining these optimized parameter windows, the patent makes precise parameter control achievable through standard manufacturing processes rather than requiring extreme precision.
Solution Approach 2:
The patent adopts a conservative approach by specifying parameter ranges that ensure performance within acceptable thresholds rather than targeting maximum theoretical values. This partial optimization strategy reduces the stringency of manufacturing precision requirements while still achieving high rate performance and low internal impedance.
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 lithium-ion secondary battery exhibits improved safety, rate, and cycle performance due to the reduced structural damage, lower electrolyte oxidation, and optimized internal impedance.
Implementation Method 1
the oxidation effect of the electrolyte on the surface of the positive active material is lower, thus the side reaction of the electrolyte on the surface of the positive active material can be reduced, suppressing gas generation and reducing heat generation
Data Source
Figure 1a~1b
AI summary
The present application discloses a positive electrode plate, a preparation method thereof, and a lithium-ion secondary battery, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film includes a positive active material which is a lithium manganese-based positive active material; and wherein the volume resistivity ρsum of the positive electrode plate, the powder volume resistivity p of the positive active material under a pressure of 20MPa and the mass percentage a of the positive active material in the positive electrode film satisfy ρsum/ρ97.5-a≤ 3. The positive electrode plate provided in the present application enables the lithium-ion secondary battery to simultaneously have higher safety performance, rate performance and cycle performance.