Lithium Ion Battery Insulation Layer Heat Management
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Solution Overview
Problem
Lithium ion secondary batteries generate excessive heat during high-rate charging and discharging, posing safety concerns due to the high current density at uncoated positive electrode collector areas, which can lead to oxidative states and exothermic reactions.
Innovation Solution
Incorporating trilithium phosphate (LPO) in the insulation layer adjacent to the positive electrode active material layer, with a higher proportion and specific surface area in the insulation layer compared to the positive electrode active material layer, to form a film that suppresses exothermic reactions at the negative electrode, thereby enhancing overcharge resistance and reducing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the positive electrode collector has uncoated collecting parts for current collection, then current collection efficiency is improved, but heat generation increases due to high current density and oxidation
Solution Approach 1:
The patent applies local quality by providing an insulation layer with specific functional properties (trilithium phosphate inclusion) only at the collecting parts of the positive electrode collector where current collection occurs, rather than uniformly across the entire collector surface. This localized treatment addresses heat generation specifically at the high current density areas while maintaining active material coverage where needed for electrochemical reactions.
Solution Approach 2:
The insulation layer acts as an intermediary between the positive electrode collector and the surrounding environment. It mediates the harmful oxidation and heat generation at the collecting parts by providing a physical barrier and chemical protection through trilithium phosphate, which suppresses exothermic reactions without interfering with the current collection function.
2Reliability
If trilithium phosphate is included in the positive electrode active material layer to improve output characteristic and durability, then battery performance is enhanced, but the amount of LPO required is large and cost increases
Solution Approach 1:
The patent segments the application of trilithium phosphate into two distinct locations: the positive electrode active material layer and the insulation layer. By placing LPO in the insulation layer at the collecting parts, the patent achieves heat suppression and durability improvement without requiring large amounts of LPO in the active material layer, thus reducing overall LPO quantity and cost while maintaining performance.
Solution Approach 2:
The patent extracts the heat suppression function from the positive electrode active material layer and relocates it to the insulation layer. This separation allows the active material layer to focus on electrochemical performance while the insulation layer handles thermal management, reducing the LPO burden on the active material and lowering overall costs.
3Power
If the battery is designed for high-rate charging and discharging, then power output is improved, but heat generation increases due to high current density
Solution Approach 1:
The patent implements preliminary action by pre-installing the insulation layer with trilithium phosphate at the collecting parts of the positive electrode collector before battery operation. This preventive measure is already in place before high-rate charging and discharging begin, so it can immediately suppress heat generation and exothermic reactions when high current density occurs, enabling safe high-power operation.
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 configuration effectively reduces heat generation and improves safety by suppressing exothermic reactions, allowing for safer operation during high-rate charging and discharging, particularly in batteries with a lamination structure used in vehicles.
Implementation Method 1
Trilithium phosphate (Li 3 PO 4 ; which may be hereinafter simply referred to as "LPO") is dissolved in the form of phosphoric acid ions (PO 4 3-)
Implementation Method 2
inclusion of LPO in the insulation layer can intensively suppress the heat generation at the easily heat generating portion of the negative electrode
Implementation Method 3
the insulation layer includes an inorganic filler, trilithium phosphate, and a binder... effectively suppress the heat generation at the easily heat generating portion
Data Source
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AI summary
A lithium ion secondary battery suppressed in heat generation entailed by charging and discharging is provided. A lithium ion secondary battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode collector, a positive electrode active material layer provided at some part of the surface of the positive electrode collector, and including a positive electrode active material, and an insulation layer provided so as to be at the other part of the surface of the positive electrode collector and to be adjacent to the positive electrode active material layer. The insulation layer includes an inorganic filler, LPO, and a binder.