Secondary battery and electric apparatus
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Solution Overview
Problem
Current lithium-ion batteries face challenges in maintaining high-temperature safety performance, particularly at high voltages, due to redox decomposition reactions that lead to increased impedance and short circuits.
Innovation Solution
A secondary battery design incorporating a positive electrode plate with an inorganic coating and specific electrolyte additives, such as lithium difluorophosphate, succinonitrile, and a controlled mass ratio of the inorganic coating to electrolyte, enhances film formation and reduces side reactions, improving thermal stability and anti-overcharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high voltage is used to increase energy density, then energy storage capacity is improved, but high-temperature safety performance deteriorates due to redox decomposition reactions
Solution Approach 1:
An inorganic coating layer is introduced as an intermediary between the positive electrode active material and the electrolyte. This coating prevents direct contact and redox decomposition reactions while allowing lithium ion transport, thereby maintaining high voltage operation without compromising high-temperature safety performance
Solution Approach 2:
The positive electrode is designed as a composite structure combining the positive electrode active material with an inorganic coating material. This composite structure provides both the high voltage capability of the active material and the thermal stability of the inorganic coating, resolving the contradiction between energy density and safety
2Reliability
If inorganic coating mass per unit area is increased to improve protective effect, then high-temperature safety performance is improved, but energy density is reduced
Solution Approach 1:
The mass per unit area of the inorganic coating is optimized to a specific range (1-20 g/m2). This parameter optimization ensures sufficient protective effect and high-temperature safety performance while minimizing the coating thickness to reduce energy density loss, thereby resolving the contradiction between safety and energy density
3Reliability
If electrolyte additive concentration is increased to improve film formation quality, then thermal stability is improved, but side reactions may increase
Solution Approach 1:
The concentration of electrolyte additives is optimized to a specific range, ensuring sufficient film formation quality and thermal stability while controlling the amount of additive to minimize side reactions. This parameter optimization resolves the contradiction between thermal stability and side reaction suppression
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 design reduces the risk of short circuits and enhances thermal stability, ensuring improved safety performance at high voltage by minimizing side reactions and maintaining film integrity.
Implementation Method 1
a positive electrode active material layer and an inorganic coating are provided on a surface of the positive electrode current collector
Implementation Method 2
improving film formation quality of cathode electrolyte interface (CEI) film and solid electrolyte interface (SEI) film
Implementation Method 3
improving infiltration performance and flame retardancy of the electrolyte
Implementation Method 4
improving the protective effect of the inorganic coating on the positive electrode plate, and reducing the risk of short circuit
Data Source
AI summary
A secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode plate includes a positive electrode current collector, and a positive electrode active material layer and an inorganic coating are provided on a surface of the positive electrode current collector. The electrolyte includes an additive, and the additive includes at least one of lithium difluorophosphate, succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, or 1,2,3-tris(2-oxyethoxy)propane. A mass per unit area of the inorganic coating is A g/m2, and based on a mass of the electrolyte, a mass percentage of the additive is B %, satisfying 0.01≤B/A≤5. Selection of the foregoing additives and control of B/A within the foregoing range are conducive to improving high-temperature safety performance of the secondary battery at high voltage.